Gear Reviews, Informational

PixInsight vs Astro Pixel Processor: Which is Best for Astronomical Image Stacking?

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Astrophotographers aiming to produce high-quality deep sky images rely on specialised software to stack and process their images. Two of the most popular choices for astronomical image stacking are PixInsight (PI) and Astro Pixel Processor (APP). While both tools offer powerful capabilities, they cater to different user needs and workflows. In this article, we explore the pros, cons, and key differences between PixInsight and Astro Pixel Processor to help you decide which is best for your astrophotography workflow.

PixInsight: Precision and Advanced Processing

PixInsight has built a reputation as the gold standard for deep sky image processing, offering unparalleled control over stacking, calibration, and post-processing.

Pros of PixInsight:

  1. Highly Customisable Processing – PI provides an extensive suite of tools and scripts that allow users to fine-tune every step of the image stacking and processing pipeline.
  2. Superior Calibration and Integration – The calibration and stacking tools in PI, such as Weighted Batch Preprocessing (WBPP), allow for precise control over light frames, darks, flats, and bias frames.
  3. Advanced Noise Reduction and Detail Enhancement – Features like Multiscale Linear Transform and Deconvolution provide powerful ways to refine details and suppress noise.
  4. Script and Process Automation – Users can automate complex workflows using PixelMath and scripting tools, streamlining repetitive tasks.
  5. Extensive Community Support and Plugins – A vast community of astrophotographers contributes to plugins, scripts, and detailed tutorials.

Cons of PixInsight:

  1. Steep Learning Curve – The interface is not beginner-friendly, requiring significant time and effort to master.
  2. No Native GPU Acceleration – PI relies heavily on CPU power, making processing times longer on large datasets compared to GPU-accelerated software. CUDA based GPUs can be added with the relevant runtime libraries.
  3. Expensive One-Time Purchase – The upfront cost can be high, though it does offer lifetime access without subscription fees.
  4. Recent Performance Issues on Windows (Reported by me) – Some users have reported significant performance issues with PixInsight on Windows 11, particularly with the latest 24H2 update. Discussions on the PixInsight forum indicate that versions 1.8.9-2, 1.8.9-3 and 1.9.2
    exhibit degraded performance on certain high core CPU systems, which only appears to affect the Windows version of PixInsight. Users running high-end hardware may experience lower-than-expected processing speeds until a fix is released.

    https://pixinsight.com/forum/index.php?threads/new-xeon-gen-5-system-low-performance-looks-like-1-8-9-2-3-dont-like-w11-24h2.24249/

Astro Pixel Processor: Simplicity and Efficiency

Astro Pixel Processor (APP) is designed for astrophotographers who want a more streamlined and intuitive approach to stacking and initial image processing.

Pros of Astro Pixel Processor:

  1. User-Friendly Interface – APP provides a more intuitive experience with a structured workflow, making it easier for beginners to get high-quality results.
  2. Automatic Calibration and Stacking – The software simplifies the pre-processing steps, requiring minimal manual intervention.
  3. Multi-Channel and Multi-Session Support – APP excels at handling mosaic projects and multi-filter data, making it ideal for narrowband imaging.
  4. Optimised for Speed – The use of efficient algorithms and multi-threading improves processing times, especially on modern CPUs.
  5. Excellent Gradient Reduction and Light Pollution Removal – The Local Normalisation Correction (LNC) and Adaptive Background Neutralisation (ABN) help correct background gradients effectively.

Cons of Astro Pixel Processor:

  1. Less Advanced Post-Processing – While APP is excellent for stacking, it lacks the sophisticated post-processing tools found in PixInsight.
  2. Subscription-Based Model – Unlike PI, APP requires an annual licence or a higher-cost perpetual licence.
  3. Limited Customisation of Algorithms – Users have less control over individual processing parameters compared to PixInsight.

Key Differences Between PixInsight and Astro Pixel Processor

FeaturePixInsight (PI)Astro Pixel Processor (APP)
Ease of UseSteep learning curve, complex UIUser-friendly and intuitive
Stacking PowerAdvanced, fine-tuned stackingFast, automated stacking
Calibration ToolsExtensive and manual controlAutomated and efficient
Post-ProcessingIndustry-leading, full-featuredBasic adjustments available
SpeedCPU-based, can be slow, recent Windows issues reportedFaster due to optimised threading
PricingOne-time purchase (£200+)Subscription or perpetual licence (£100+/year)

Which One Should You Choose?

  • If you want maximum control, professional-level processing, and a comprehensive astrophotography workflow, PixInsight is the superior choice.
  • If you prioritise ease of use, efficient stacking, and automation while still achieving excellent results, Astro Pixel Processor is a great alternative.

Many astrophotographers use both (Like me)—APP for stacking and initial processing, followed by PI for detailed refinement and final adjustments.

Regardless of your choice, both PixInsight and Astro Pixel Processor are powerful tools that can elevate your astrophotography, helping you extract the best possible detail from your hard-earned data.

ColdMOS Images

Eternal Quest: The Elephant’s Trunk Nebula Unveiled

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In the boundless theatre of the night sky, where celestial tales unfold across the eons, lies an ethereal masterpiece that has captivated the gaze of astronomers and dreamers alike. This image, a delicate two-panel mosaic, is a profound revelation of the Elephant’s Trunk Nebula, known formally by its catalog designations IC 1396A, nestled within the larger expanse of the IC 1396 complex in the constellation of Cepheus.

Crafted with meticulous dedication over the span of five months, this portrait of the cosmos was brought to life using a full-frame monochrome CMOS camera, a testament to the intersection of art and technology. The camera, acting as a modern-day alchemist, transformed the invisible into the visible, capturing the nebula’s intricate details and sweeping gas clouds that resemble an elephant’s trunk, reaching out into the void.

However, this image is more than a snapshot; it is a chapter in an ongoing saga dictated by the unpredictable whims of the UK’s weather. The journey to encapsulate the nebula’s full glory has been a dance with the elements, with many nights spent under the cloak of clouds rather than stars. Despite these challenges, the initial results have unveiled a stunning glimpse into the cosmos, showcasing the nebula’s haunting beauty and the vibrant activity within its star-forming regions.

Yet, the story does not end here. The image is a promise of what is yet to come, as there are plans to revisit the Elephant’s Trunk Nebula later this year. The aim is to deepen the exploration, to add more data to this cosmic tapestry, and to further refine the clarity and depth of this celestial phenomenon.

This endeavor, a blend of patience, passion, and precision, highlights not just the technical prowess required for astrophotography but also the enduring human desire to connect with the universe. Through this image, we are reminded of our place in the cosmos, a mere speck within the vastness, yet capable of capturing and celebrating its majesty.

The Elephant’s Trunk Nebula stands as a beacon in the dark, a symbol of the mysteries that await our discovery. With each photograph, we peel back another layer of the universe, bringing us closer to understanding the grand design of which we are a part. This image is an invitation to gaze upwards, to wonder, and to dream of the infinite possibilities that lie beyond our world.

Here is the Astrobin link for the full resolution image: https://www.astrobin.com/full/qxmduq/0/

Frames:
Chroma H-alpha 3nm Bandpass 50 mm: 81×300″(6h 45′) (gain: 100.00) -10°C bin 1×1
Chroma OIII 3nm Bandpass 50 mm: 91×300″(7h 35′) (gain: 100.00) -10°C bin 1×1
Chroma SII 3nm Bandpass 50 mm: 125×300″(10h 25′) (gain: 100.00) -10°C bin 1×1

Integration: 24h 45m
Darks: 51
Flats: 51
Bias: 201

Equipment:
Imaging Camera: ZWO ASI Cameras ASI6200MM Pro Gain 100 -10C
Imaging Scope: Sharpstar Optics 20032PNT F3.2 Paraboloid Astrograph
Filters: Chroma 50mm 3nm Filters
Filterwheel: ZWO ASI Cameras 7x EFW
Guide Camera: ZWO ASI Cameras ASI290MM
Mount: Sky-Watcher EQ8 Pro German Equatorial Mount
Auto Focuser: Primalucelab Sesto Senso2
Environmental conditions: Primalucelab ECCO2
Observatory Control: PrimaLuceLab Eagle Eagle 4 Pro
Roof Control: Talon RoR
Image Acquisition: Main Sequence Software Sequence Generator Pro
Image Calibration and Stacking: Astro Pixel Processor
Image Processing: PixInsight, Russ Croman’s BlurXterminator and StarExterminator

ColdMOS Images

Heart and Soul 3 Panel Mosaic

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In the boundless theatre of the night sky, a spectacle of cosmic proportions gently unfolds. Here, through the unblinking eye of my camera, we witness the Heart and Soul Nebulae, celestial bodies of unimaginable scale and beauty. Captured in the vivid hues of the Hubble Palette, this image is the culmination of over 68 hours of patient vigil over the course of six months, a testament to the relentless march of time and space.

The Heart Nebula, known as IC 1805, and its companion, the Soul Nebula, IC 1848, are more than mere clusters of gas and dust. They are incubators of stars, cosmic nurseries where new celestial lives begin. Nestled within is the charmingly named Fish Head Nebula, a smaller star-forming region within this grand cosmic landscape.

Each pixel of this mosaic is a story, a tiny fragment of the universe’s narrative, captured through the artful blend of sulfur, hydrogen, and oxygen emissions. As we gaze upon this image, we are not merely observers but voyagers, embarking on an odyssey across the galaxy. It invites us to ponder our place in this magnificent universe, a reminder of both our insignificance and our profound connection to the cosmos.

In the grand scheme of things, this image is but a fleeting glimpse into the eternal dance of the cosmos. It is a humble offering to the beauty and complexity of the universe, a universe that continues to captivate and inspire us with its endless mysteries.

Catalog Names:
IC 1805 (Heart Nebula)
IC 1848 (Soul Nebula)
Fish Head Nebula (Part of the Heart Nebula)

Acquisition Dates:
16 May 2023, 17 May 2023, 20 May 2023, 21 May 2023, 25 May 2023, 26 May 2023, 27 May 2023, 28 May 2023, 15 Jun 2023, 16 Jun 2023, 24 Jun 2023, 25 Jun 2023, 26 Jun 2023, 13 Jul 2023, 16 Jul 2023, 17 Jul 2023, 19 Jul 2023, 20 Jul 2023, 25 Jul 2023, 26 Jul 2023, 6 Aug 2023, 7 Aug 2023, 9 Aug 2023, 10 Aug 2023, 17 Aug 2023, 20 Aug 2023, 22 Aug 2023, 5 Sep 2023, 9 Sep 2023, 15 Sep 2023, 23 Sep 2023, 29 Sep 2023, 8 Oct 2023, 9 Oct 2023, 14 Oct 2023, 15 Oct 2023, 6 Nov 2023, 7 Nov 2023, 10 Nov 2023, 11 Nov 2023, 14 Nov 2023, 15 Nov 2023, 19 Nov 2023, 20 Nov 2023, 22 Nov 2023, 24 Nov 2023, 25 Nov 2023

Frames:

Chroma H-alpha 3nm Bandpass 50 mm: 213×300″(17h 45′) (gain: 100.00) -10°C bin 1×1
Chroma OIII 3nm Bandpass 50 mm: 303×300″(25h 15′) (gain: 100.00) -10°C bin 1×1
Chroma SII 3nm Bandpass 50 mm: 303×300″(25h 15′) (gain: 100.00) -10°C bin 1×1

To see the image in all its glory, use the link

Equipment:
Imaging Camera: ZWO Astronomy Cameras ASI6200MM Pro Gain 100 -10C
Imaging Scope: Sharpstar Optics 20032PNT F3.2 Paraboloid Astrograph
Filters: Chroma 50mm 3nm Filters
Filterwheel: ZWO Astronomy Cameras 7x EFW
Guide Camera: ZWO Astronomy Cameras ASI290MM
Mount: Sky-Watcher EQ8 Pro German Equatorial Mount
Auto Focuser: Primalucelab Sesto Senso2
Environmental conditions: Primalucelab ECCO2
Observatory Control: Primalucelab Eagle Eagle 4 Pro
Roof Control: Talon RoR
Image Acquisition: Main Sequence Software Sequence Generator Pro
Image Calibration and Stacking: Astro Pixel Processor
Image Processing: PixInsight, EZ Processing Suite, Russ Croman’s BlurXterminator and StarExterminator

Informational

The Art of Exposure in Astrophotography: Short & Frequent vs. Long & Few

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Introduction
Artistic and scientific practises collide in astrophotography, which lets us capture the vast beauty of the cosmos from our own backyards. Exposure is a major factor in creating stunning photographs like these. Today, we’ll delve into one of the most contentious issues in astrophotography: the debate between taking fewer, longer exposures versus taking many shorter ones. Knowing the benefits and drawbacks of each technique will help you select the best one for your heavenly masterpiece.

Shorter But Higher Quantity Exposures

Pros:

  1. Mitigate Tracking Errors: Inaccuracies in tracking can be mitigated by using shorter exposures. Polar misalignment, periodic error, wind, and other disturbances can all cause minor deviations in the position of the stars, even with the best tracking mounts. These flaws will be less noticeable in the final product if the exposure time is shortened.
  2. Reduction of Overexposure: Overexposing bright objects or regions is avoided and detail is preserved by using shorter exposures. This is especially helpful in high-dynamic-range objects like nebulae, star clusters, and galaxies.
  3. Increased Flexibility: You can get more information out of your data if you take more pictures. Negative images caused by things like satellite trails or sudden atmospheric turbulence can be thrown out without having a major impact on the quality of the data as a whole.

Cons:

  1. Increased Noise: Noise, especially read noise from your camera, is more noticeable in short exposures. Image stacking and dark frame subtraction can help with this, but it’s still something to think about.
  2. Intensive Data Management: When taking many quick shots, you risk having too much information. The process of organising, storing, and processing such massive amounts of data can be laborious and error-prone.

Longer But Fewer Exposures

Pros:

  1. Better Signal-to-Noise Ratio (SNR): SNR is increased because longer exposures allow more light from faint deep-sky objects to be captured. Images benefit from being clearer, smoother, and more detailed, especially in low-light areas.
  2. Less Processing Required: If there are fewer frames in total, your workflow could be simpler and require fewer resources to complete. This is helpful regardless, but especially so when working with less robust computer hardware.
  3. Less Impact from Read Noise: Taking longer exposures results in less read noise from the camera sensor than taking a large number of shorter ones.

Cons:

  1. Risk of Overexposure: When using a long exposure, highlights risk being overexposed. Particularly in regions with bright stars or nebulae, this can cause a loss of fine detail.
  2. More Vulnerable to Tracking Errors: When using a long exposure, mistakes in tracking and atmospheric disturbances are more likely to occur. Stars will start to blur or trail if you move even slightly, ruining an otherwise perfect exposure.
  3. Less Room for Error: When there are fewer options, each photo is more precious. Unexpected problems (such as a plane crossing, sudden gusts of wind, etc.) that affect some frames have a greater effect on the overall image quality.

Conclusion
The equipment you’re using, the object you’re photographing, and the sky conditions all play a role in determining whether you should use shorter, more frequent exposures or longer, fewer ones. Keep in mind that neither method is better than the other. How well the strategy works to get you where you want to go is what matters.

Trying out different shutter speeds and exposures is always a good idea. After all, astrophotography is not just about getting the perfect shot; it’s also about the process of getting there. Keep in mind that the sky is always there for you to use as a blank canvas. Have fun with it!

Equipment, Informational

The CCD vs. CMOS Showdown: Why Monochrome Cameras Excel in Astrophotography Over One Shot Color

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Introduction
One of the first things photographers must decide when venturing into astrophotography is what kind of camera sensor they’ll need to capture the beauty of the cosmos. Charge-Coupled Device (CCD) and Complementary Metal Oxide Semiconductor (CMOS) image sensors are two of the most common on the market (CMOS). Each has its own set of pros and cons that make it better or worse for astrophotography in certain situations. Further complicating matters is the ongoing discussion between advocates of monochrome and one-shot colour cameras.

Understanding CCD and CMOS Sensors
Light is converted into electronic signals by the CCD or CMOS sensor at the centre of a digital camera. The image quality, cost, and power consumption are all impacted, but in fundamentally different ways.

CCD Sensors
CCDs have been the go-to sensors for astronomy photography for quite some time. They are well-known for the exceptional clarity and sensitivity to light of their photographs. These sensors generate low-noise, high-quality images by transferring charge across the chip and converting it into voltage in a single spot: the array’s corner. In turn, this improves light collection by allowing for a greater pixel fill-factor. CCDs, on the other hand, are typically more costly and power-hungry than their CMOS counterparts. In addition, they experience ‘blooming,’ an effect in which overcharged pixels leak their energy into neighbouring ones.

CMOS Sensors
In contrast, CMOS sensors have shorter processing times and use less power because light is converted to voltage right at each pixel’s location. They have lower manufacturing costs, making them common in smartphones and consumer-grade cameras. Their read noise and sensitivity are typically higher than that of CCDs, though. Recently developed technologies have allowed CMOS sensors to catch up to and even surpass CCDs in terms of performance, closing the gap between the two.

Monochrome vs. One Shot Colour Cameras
After settling on a CCD or CMOS camera, the next big decision in astrophotography is whether to use a monochrome or one-shot colour camera.

One Shot Color Cameras
As the name implies, a One Shot Color camera takes a complete colour picture with just one click of the shutter. The Bayer mosaic used in these cameras covers each pixel with red, green, and blue filters. The greatest benefit of these cameras lies in their ease of use. Even amateur astronomers can easily take stunning, colourful pictures of the night sky with these instruments.

Monochrome Cameras
Images taken with a monochrome camera are grayscale. These cameras capture red, green, and blue light through individual filters and combine them into full colour in post-production. Even though using a monochrome camera is more difficult and time-consuming, there are some benefits.

Why Monochrome Cameras Excel in Astrophotography
In general, monochrome cameras have higher sensitivities than single-shot colour ones. They are up to three times as sensitive as cameras that use a Bayer filter because all of the light that reaches the sensor is used to create the image. This heightened sensitivities is especially helpful in low-light astrophotography.

Additionally, more options and control can be had during the imaging process when separate filters are used with a monochrome camera. Using a hydrogen-alpha filter, astronomical photographers can isolate and emphasise specific wavelengths of light, such as the ionised hydrogen regions in nebulae. Imaging in light-polluted skies or capturing narrowband images greatly benefits from this ability.

Because the information for each colour channel is captured by the entire sensor rather than just a subset of pixels, as in one-shot colour cameras, the resulting images have greater resolution and detail.

Conclusion
In conclusion, CCD and CMOS sensors each have their uses in astrophotography, and the one you settle on will depend on your particular goals, financial constraints, and level of experience. Comparing monochrome and one-shot colour cameras, the former has better sensitivity, flexibility, and resolution while the latter is more user-friendly and saves time. Therefore, the investment in a monochrome camera and separate filters can be well worth it for serious astrophotographers seeking to capture the highest quality images.

Informational

Creating a Hubble Palette Image from OSC Dual Band Data

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Many people like myself have transitioned from a MONO camera to a One Shot Colour (OSC) for whatever reason, for me it was all about not being able to get the required amount of time due to weather conditions here in the UK. When I first considered moving to an OSC camera, it dawned on me that I would not be able to produce the vibrant Hubble Palette images that I could produce by imaging with specific filters on my MONO camera, specifically Hydrogen Alpha (Ha), Oxygen 3 (OIII) and Sulphur Dioxide 2 (SII) which would then be mapped to the appropriate colour channels when creating the final image stack.

Now along came Dual and Tri band narrowband filters for OSC cameras which peaked my attention, the Dual Band filters allow Ha and OIII data to pass, the Tri Band filters allow Ha, Hb (Hydrogen Beta) and OIII to pass but at a high Nm value. I reached out to my friends at Optolong who had two filters, the L-eNhance and the L-eXtreme, the L-eNhance is a Tri Band filter, but after speaking with Optolong it would not work well for me at F2.8, so I went with the L-eXtreme Dual Band filter which has both the Ha and OIII at 7nm.

After receinving my ASI6200MC Pro, I decided to start acquiring data on a 1/2 to 2/3 moonlit nights on the North America Nebula, and so far when writing this post I had acquired a total of 60 frames of 300 seconds each at a gain value of 100, I processed the image my normal way in PixInsight and below is the result of the image:

North America Nebula, 60x300S at Gain100, Darks, Flats and BIAS frames applied with the ASI6200MC Pro using the Optolong L-eXtreme Dual Band 2″ Filter

I thought that my data looks good enough to work with and experiment with trying to build an SHO (Hubble Palette) image with, and I have spoken with Shawn Nielsen on this exact subject a few times so he gave me some hints and tips especially with the blending of the channels. So off I went to try and produce an SHO image.

Before we start, there are some requirements:

  • This tutorial uses PixInsight, I am not sure how you would acomplish this with Photoshop since I have not used PhotoShop for Astro Image Processing for a number of years
  • Data captured with a One Shot Color (OSC) camera using a Dual or Tri Band Narrowband filter
  • Image is non-linear…so fully processed

Step 1 – Split the Channels

In order to re-assign the channels, you have to split the normal image into Red, Green and Blue channels, I found this to work better on a fully processed “Non-Linear” image as above, once this was done, I renamed the images in PixInsight to “Ha” – Red Channel, “OIII” – Blue Channel and “SII” – Green Channel, this makes it easier for Pixelmath in PixInsight to work with the image names. Once this was done, I used PixelMath to create a new image stack with the channels assigned, and this is how PixelMath was configured

Red Channel = SII
Green Channel = 0.8*Ha + 0.2*OIII
Blue Channel = OIII

Once applied this produced the following image stack (do not close the Ha, OIII or SII images, you will need these later on):

SHO Combined image from PixelMath

Step 2 – Reduce Magenta saturation

As you can see from the above image, some of the brighter stars have a magenta hue around them, so to reduce this, I use the ColorMask plugin in PixInsight (You will need to download this), and selected Magenta

ColorMask tool with Magenta selected

When you click on OK, it will create the Magenta Mask which would look something like this:

Once the mask has been applied to the image, I then use Curves Transformation to reduce the saturation which will reduce the Magenta in the image


The result in reducing the magenta can be seen in this image, you will notice there is now no longer a hue around the brighter stars

Result after Magenta Saturation reduced using Magenta ColorMask and Curves Transformation

Step 4 – ColorMask – Green


Again using the Color Mask tool, I want to select the green channel, as we will want to manipulate most of the green here to red, so again ColorMask:

This then produced a mask that looks like the following:

Step 5 – Manipulate the Green Data

Once the Green Mask has been applied to the image, since most of the data in the image is green, we are looking to manipulate that data to turn it golden yellow, so for this we use the Curves Transformation again

The above Curves transformation was applied to the image three times whilst the the green mask was still im place, and this resulted in the following image changes:

Resulting image after green data manipulated in the red channel using Curves Transformation

So as you can see we are starting to see the vibrant colours associated with Hubble Palette images

Step 6 – Create a Starless version of the OIII Data

Now remember I said not to close out the separated channel images, this is because we are going to want ot bring out the blue in the image without affecting the stars, so for this we will turn the OIII image into a starless version by using the StarNet tool in PixInsight

Here’s the OIII Image before we apply StarNet star removal:

Default settings used in the StarNet process

This resulted in the following OIII image with no stars:

Step 7 – Range Selection on OIII Data

Because we do not want to affect the whole image, we will use the range selection tool on the starless OIII image to select areas we wish to manipulate, now we have to be careful that the changes we make are not too “Sharp” that they cause blotchy areas, so within the range selection tool, not only do we change the upper limit to suit the range we want to create the mask for, but we also need to change the fuzziness and smoothness settings to make it more blended, these are the setings I used:


Which resulted in the following range mask

Step 8 – Bring out the Blue with Curves Transformation

We apply the Range Mask to the SHO Image so that we can bring out the Blue in the section of the nebula where the OIII resides, with the range mask applied we will use the Curves Transformation Process again as follows:

Curves transformation process to increase blue, reduce red and increase saturation of image with rangemask applied

The result of which is:

Result after first curves transformation with RangeMask applied

As you can see we have started to bring out the blue data, but we are not quite there yet, with the range mask still applied, we will go again with the curves transformation only this time, just reducing the red element:


The result of the 2nd curves transformation with the Range Mask is as follows:

Resulting image after 2nd pass with Curves Transformation to remove the red elemtn in the range mask

Step 9 – Apply Saturation against a luminance mask

On the above image, we extract out the luminance and apply as a mask to the image, and we then use the Curves Transformation for the final time to boost the saturation to the luminance

Luminance Mask to be applied to image
Curves Transformation with Luminance Mask applied

Final Image

I repeated the same process on my Elephant’s Trunk Nebula that I acquired the data when testing out the ASI2400MC Pro and this was the resulting image:

I hope this tutorial helps in producing your SHO images from your OSC Narrowband images, I know many of my followers have been waiting for me to write this up, so enjoy and share.

Equipment, Gear Reviews, Informational

Sharpstar 20032PNT F3.2 Paraboloid Astrograph Review

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Having owned the Sharpstar 15028HNT, I decided I wanted a larger light bucket without really sacrificing on speed, so I opted for the big brother of the 15028HNT which is the SharpStar 20032PNT.

I picked up my 20032PNT from Zoltan at 365Astronomy, and could not wait to get it home and unbox it, so after removing it from not just one carboard box, but two, I was presented with a very large flight case, which evidently is a larger version than the one that came with the 15028HNT.

Once I had the scope unpacked and inspected everything, the first thing I noticed was the focuser, the 20032PNT has a large focuser, which is big enough to accomodate the reducer/corrector that has an M68 connector thread as well as an M54 and an M48 connector thread.

The scope is well built, as I would expect from the build quality of the 15028HNT, the red annodised alluminium tube rings just give that final touch of finese. The 3 inch focuser is very smooth, and will no doubt be able to handle quite a load of equipment.

The first thing I planned to do was ensure that the primary mirror was secure and did not rock back and forward as well as replace the stock fan. I have fed back to SharpStar that they should mount the fan externally and also mount it with shock absorbing rubber mounters, and have the airflow into the tube from the back, rather than drawing air down the tube from the secondary. Here are my images of the fan replacement:

Primary Mirror assembly removed from OTA
Fan assembly with mirror removed
Stock Fan

Stock fan removed and added in a PWM fan connector should the fan ever need to be replaced, it can be replaced without removing the mirror assembly
Anti vibration fan mounting points
External fan connected to PWM connector
How the fan looks from the outside, the image is missing the fan filter which I added afterwards

Once everything was back together, I mounted my Eagle4Pro onto the top bar, as well as added an extra long losmandy plate because I wanted the OTA as far forward as I could get it in order to have the camera in the right location without it hitting the mount at all.

And here is the scope on the mighty EQ8 Pro mount

My first set of image testing did not go so well. My previous 15028HNT did not protrude above the walls of the observatory, so despite the fact that the secondary mirrors on both scopes are right up at the top of the tube, the 20032PNT was picking up stray light from my neighbour, so I had to adopt a dew shield that would extend the OTA by around 5 inches:

Scope with dew shield attached

Flats
I first started to have issues with my flats that was taken with a flat panel, the flat frames would “Overcorrect” the images, but one thing I noticed that there was a lot of vignetting happening. Sky flats seemed to work better, but I was not happy with the vignetting. Now since I am using a full frame sensor on the ASI6200MM Pro, and the scope supports full frame, I was a little intrigued as to why I was getting so much vignetting, you can see from the master flat below that there was indeed a significant amount of vignetting.

Red Master Flat in PixInsight

I did some calculations and found what my problem was. Since my camera is full frame, it has a diameter of 44mm. The M54 connector on the telescope is 55mm away from the sensor, so a simple equation tells me that my light cone is larger than the M54 connector:

Sensor diameter + (distance from sensor / focal ratio)
44 + (55/3.2) =61.1875mm

The internal diameter of the M54 connector is around 51mm, so the light cone was being restricted by around 10mm. So I had a custom M68 to M54 adapter made which is 28.5mm in length, the reason for this is because the backfocus from the M68 connector is 61mm, so if we apply our formula:

44 + (61/3.2) = 63.06mm, this is way below the internal diameter of the M68 connector male thread, so vignetting should be minimised. Now because I do have some M54 in my image train, I know I would not completely elliminate vignetting and this is why, using the above formula, we can work out the light cone at varying part of the imaging train:

12.5mm (EFW mating to camera) = 47.9mm
18mm (50.4mm Filters distance from sensor) = 49.62mm
32.5mm (Light entrance to EFW distance from sensor) = 54.15mm

As you can see, I should expect some vignetting to occur because the light cone at the EFW M54 connector (with around 51mm internal) is 54.15mm, so I would be clipping the light cone slightly, but the result is as follows, again red filter, you can see that the vignetting is significantly reduced:

Collimation was done using the exact same process I used on the 15028HNT, you can read the guide here.

Conclusion:
SharpStar have again produced an outstanding quality astrograph, with a massive focuser to take on the largest of imaging trains, as well as finishing off the product with high quality annodised OTA rings. I am extremely happy with the performance of the telescope, below is my first image which happens to be a 2 panel mosaic:

Iris Nebula, 2 Panel Mosaic, Each Panel consists of 151x60S frames at Gain100, for L, R, G and B, for the full resolution image please use this link

Backfocus information:
M42 connector: 53mm
M54 connector: 55mm
M68 connector: 61mm

Focal Length (With Reducer/Corrector): 640mm
Focal Ratio: F3.2
Newtonian Type: Paraboloid
Focuser Size: 3″

The only complaint I have is with regards to the fan, which I have made a suggestion to SharpStar on that. Good job again SharpStar!

Equipment, Gear Reviews

ZWO ASI6200 62mpx Full Frame Camera Review

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I recently wrote a review on the ZWO ASI2400 24mpx full frame camera, so I thought I would also do the same for the big brother which is the ZWO ASI6200 full frame camera with a mammoth 62mpx which I picked up from 365astronomy when returning the ASI2400 after the review. Looking at both of the cameras, there is no obvious difference from the outside except for the model number, both cameras are exactly the same size and feel roughly the same weight and the build quality is identicallyu exceptional.

ASI6200MC Pro One Shot Colour Camera

If we compare the specifications of the ASI6200 to the ASI2400 we can see where each camera has an advantage over the other:

ASI2400ASI6200
Weight700g700g
SensorIMX410IMX455
Sensor SizeFull FrameFull Frame
Pixel Size5.94um3.76um
Resolution24mpx62mpx
Full Well Capacity at 0 Gain100ke51ke
Qe>80%91%
ADC14-Bit16-Bit
High Gain Mode140100
Full well at High Gain Mode20ke18ke

So as you can see from the comparison on specification there are some differences, the ASI2400 has the edge on full well capacity, however the ASI6200 has a much more smaller pixel size as well as a higher Qe which to me gives the ASI6200 the edge over the ASI2400.

Now since both cameras are the exact same field of view due to them both being full frame sensors, the question is how does this affect resolution, clearly the ASI6200 has the upper hand having significantly more pixels than the ASI2400, but how does this translate to an image?

Iris Nebula taken with the ASI2400MC Pro, 82x150S at Gain 26, darks, flats and BIAS frames applied
Iris Nebula taken with the ASI6200MC Pro 48x150S at Gain 100, Darks, Flats and BIAS frames applied

As you can see, both cameras offer the exact same field of view, however when you zoom in on the images you start to see where the ASI6200 excels above the ASI2400 with the higher resolution

On the left is the ASI2400MC Pro and on the right is the ASI6200MC Pro

As you can clearly see from the above two images, the 6200 offers a much better resolution which will allow a much finer level of detail, however, depending on your sky conditions and focal length the ASI6200 might not be possible due to over or under sampling

You can see here, that on my SharpStar 15028HNT which has a Focal Length of 420mm the ASI2400 would lead to Under Sampling in my “OK” seeing conditions

But the ASI6200 shows in the green area:

If I increase the focal length to around 1150 the ASI6200 no longer becomes suitable and the ASI2400 is more suited to this focal length and sky conditions:

So as you can see, both the ASI2400 and ASI6200 is not a “One Size Fits All” scenario, you have to work out the best suitability depending on your conditions and equipment to be used.

From a price perspective, the ASI6200 is only slightly more expensive than the ASI2400, but both cameras offer the full frame capability and a fantastic field of view, but for me personally the ASI6200 beats the ASI2400 when using the focal length of my SharpStar 15028HNT. Just like it’s smaller version, the looks, feels, sounds and operates exactly the same way. Here is another image taken with the ASI6200 and then my Synthetic SHO version which I will be writing a tutorial on how to acomplish with Dual Band Filters.

North America Nebula – 60x300S at Gain 100 using the Optolong L-eXtreme Filter on the SharpStar 15028HNT
Synthetic SHO using the same data as the previous image

Either way, both ZWO cameras I have tested have been of awesome quality, and I would recommend either camera if you wish to go down the full frame route, but personally my favourite is the ASI6200MC Pro, more images to come since this is now my new camera.

Equipment, Gear Reviews

ZWO ASI2400MC Pro Full Frame 24mpx camera review

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I was lucky enough for 365Astronomy to offer me one of the ZWO ASI2400 full frame cameras to test and write a review, so obviously I jumped at the chance, and within a couple of days I was successfully imaging and acquiring data with it, so firstly what is the ASI2400?

The ASI2400MC Pro is a full frame 24mpx camera that utilises the Sony IMX410 back illuminated sensor, ZWO produced a similar camera before which was the ASI128MC Pro (24mpx) and they also have the ASI6200 (62mpx), so what are the differences between the cameras?

ASI2400MCASI128MCASI6200MC
Image SensorIMX410IMX128IMX455
Pixel Size5.945.973.76
Full Well Capacity100ke76ke51.4ke
Cooling Delta-35C-35C-35C
Resolution6072×40426032*40329576×6388
ADC14-Bit14-Bit16-Bit
Read Noise1.1e-6.4e2.5e1.2e-3.5e
DDR Buffer256MB256MB256MB
QE >80%>53%>80%
FPS (Video)852

If we compare the ASI2400 and the ASI128 since they have similar pixel sizes and offer almost a matching resolution, but the ASI2400 clearly is a better camera, with a higher full well capacity, this means that it takes a lot more to saturate out the colours around bright stars for example, but also a big increase on the quantum efficiency going from 53% to >80%.

Now the first thing I noticed was that the ASI2400 was only slightly cheaper than the ASI6200, but the ASI6200 is offering a much higher resolution, so why would people not just go for the ASI6200? Well it comes down to pixel size, the ASI6200 has a pixel size of 3.76 so it would be better suited to a short focal length scope, if I attach the ASI6200 to my SharpStar 15028HNT which has a focal length of 420mm at F2.8, this will give me around 1.85 Arc-Seconds per Pixel which for UK skies is an ideal figure, the ASI2400 has a bit more flexibility with the focal length of telescopes because of the larger pixel size, so whilst the ASI6200 offers a higher resolution image sensor of 62mpx, the ASI2400 offers more flexibility of a higher focal length telescope.

When I unboxed the ASI2400 I was very impressed with the quality, this was the first ZWO Camera I have ever actually seen in the flesh, the red finish matches my SharpStar 15028HNT, but one thing that I noticed straight away was the two additional USB Ports on the top of the camera which I sat and thought to myself that it would certainly help with tidying up my cables around the scope. In the box was a couple of adapters to obtain the very common 55mm back focus, two USB Cables, and a USB 3.0 cable, and the camera arrived in a very nice case too.

I removed the camera sensor cover and revealed the massive full frame sensor and compared it to the APS-C sized camera I have and was like wow, that’s a big sensor, here’s a picture of the sensor:

Size matters, the Full Frame sensor on the ASI2400MC Pro

I noticed too that there was a special tilt plate on the camera which in my opinion is a critical point, my other camera has a tilt plate that is very cumbersome to use, so after a while of looking at the sensor, I decided to start adding my ZWO filter drawer and M48 extension tubes in order to get it connected to the mount, I am using the ZWO M54 2″ Filter drawer which has a 2mm M54 to M48 adapter too, threading the filter drawer on the camera was very smooth, but I would not expect anything less than that with ZWO kit connecting to ZWO kit, here’s a picture with the filter drawer and the Optolong L-Pro 2″ filter connected to the camera:

ZWO M54 Filter Drawer connected to the ASI2400MC Pro

Once connected to the telescope, I had to find out where the camera was facing when connected at the optimal distance of 55mm as all of my image train is threaded on, once identified which direction the top of the camera sensor was facing I could rotate the focuser and then re-check the collimation with the laser before putting the camera back on and connecting the cables.

Identifying which side of the camera the top of the sensor was is so easy on this camera, there’s what looks like a black plastic button on the side of the camera, it is obviously a cover of some sort, but this also indicates which side the top of sensior is located, something I wish all camera vendors would do.

One of the first things I do when testing out a new camera is dark frames, all vendors claim they have zero amp glow, so this is always my first test, and the ASI2400 didn’t let me down, indeed there was zero amp glow and I tested with various exposure times and gain settings, here’s a 300S exposure with Gain 26 which has had a Screen Transfer Function auto stretch applied:

After connecting it all up to the telescope, and acquiring some darks, flats, and BIAS frames, and the skies were clear, it was time to put the camera under a proper test, I had set a couple of targets up, the Cygnus Loop and the Elephant’s Trunk Nebula using the Optolong L-eXtreme Narrowband filter and here are the results:

Cygnus Loop – Eastern Veil, Western Veil and Pickerings Triangle – 29x300S at Gain 26, ASI2400MC Pro on the Sharpstar15028HNT using the Optolong L-eXtreme Dual Band Filter
Elephant’s Trunk Nebula – 19x300S at Gain 26, ASI 2400MC Pro on the SharpStar 15028HNT using the Optolong L-eXtreme Dual Band Filter

So you can see the camera performed really well, stars are almost perfect in the corners (a little fine tuning required on spacing), I am hoping to get a few more clear nights over the next few days to build on the above images and really show off the performance of the ASI2400, and I can’t wait to test it out on the Iris Nebula.

Conclusion:
The ASI2400 is in my opinion an awesome piece of kit, that massive full frame sensor has the adaptability for longer focal length telescopes due to the larger pixel size, the advantage of the USB Hub built into the camera, the adjustable tilt plate on the front of the camera is the most advantageous aspect, would have saved me so much time trying to rectify tilt instead using copper shims, but also the smaller things that are equally as important like having something to identify which way round the sensor is rather than trying to figure it out with images in my opinion is what sets this apart from other similar cameras from other vendors.

If you are looking for a full frame camera and have a short focal length telescope, the ASI2400 or the ASI6200 full frame cameras will do just the job,but any longer focal length scopes, then the ASI2400 is the right choice.

Additional image taken since writing this post:

M31 – Andromeda Galaxy – 51x90S frames at Gain 0 using the Optolong L-Pro Filter, darks and flats applied
Informational

A step by step guide to Collimation

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If like me you own some sort of reflector telescope, whether this be a Newtonian, Dobsonian, Ritchey Chretien or as I have a Hyperboloid Astrograph then you’ll know that there is a very strong importance on collimation, the faster the optics the more critical collimation becomes, especially for imaging. After recently removing the rear mirror assembly for cleaning, as well as changing from the QHY183M to the QHY268C-PH amongst onther stuff in the imaging train, I wanted to share my experience and knowledge around collimation. Let’s start off with the details on what I use

Part 1 – Aligning the Secondary Mirror with the Focuser

Now on my SharpStar 15028HNT, they recommend you unscrew and remove the corrector from the focuser, however I have found no difference in collimation with or without the corrector in place and because it is part of the optical train I’d rather include it in the collimation, so the first step for me since my primary mirror was currently removed was to check the secondary alignment with the focuser, as well as the rotation of the secondary in relation to the focuser, in order to do this, I use the Teleskop-Service Concenter eyepiece, the eyepiece itself has a set of rings engraved into the plastic apperture like so

Teleskop-Express Concenter Eyepiece markings on lower end of barrel

I ensure that my focuser is at the most inward position and since my SharpStar has an M48 thread on the focuser, I used a 2″ extension tube that has an M48 thread on it, and placed the concenter eyepiece in there:

M48 threaded 2″ Extension tube with Teleskop-Express Concenter Eyepiece

This serves well to get the rotation and alignment of the secondary with the focuser by ensuring that the mirror appears as a perfect circle between the rings, now you can adjust your focuser position in order to get the edge of the mirror to appear on the lines, this is what the view looks like through the concenter eyepiece:

Here you can see the secondary mirror appears circular and in line with the concenter eyepiece markings showing a successful alignment with the focuser

The blue at the top right of the image is a piece of card I stuck behind the secondary in order to show the edge of the mirror better.

As you can see my secondary mirror is pretty much perfectly aligned with the focuser and square with the focuser also, if your mirror shows up as more eliptical, this means the mirror needs to be rotated, if the mirror does not fit in within the circle itself, for example if it is over to the left or right, you will need to move the mirror forward or backwards by means of loosening or tightening the central screw that holds the secondary.

You can see from the following image, I have a central screw which is used for moving the mirror up or down the tube away from or closer to the primary, as well as rotation of the mirror, but then there is also the three collimation screws that are used to adjust the mirror direction itself which we will talk about in the next section

Here you can see the central adjustment screw for adjusting the mirror rotation and centering the mirror with the focuser, the three outer scres are used for adjusting the tilt of the mirror to align with the primary

Part 2 – Aligning the Secondary Mirror with Primary Mirror

Now that we have our secondary mirror lined up and square with the focuser, the next step is to align the secondary with the primary, now for this I will use my FarPoint Astro Laser collimator, which itself has recently been collimated by FarPoint Astro, now you can re-use use the 2″ extension tube and place the laser into the tube, but for the SharpStar I will use the M48 to 1.25″ lockable adapter like so:

FarPoint Astro laser collmator in the SharpStar M48 to 1.25″ Adapter

Now the point of this part is to ensure that the laser hits the centre spot of the primary mirror, if it does not, then this is where you would adjust one or more of the three screws on the secondary, as you undo one, you should tighten the other two, as you can see from this image, I need not make any adjustments as the laser hits the centre of the primary perfectly:

Here you can see that the laser hits the primary mirror centre spot

Part 3 – Aligning the Primary Mirror

Now since I do not have to make any further adjustments to the secondary mirror, it is time to focus on the primary mirror, the trick here is to get the laser beam to return to the point of origin, here’s an example of the primary not being correctly aligned:

You can see two dots here, one is the laser aperture, the other is the reflection of the laser from the primary mirror, this reflection needs to meet the aperture

You can clearly see the red dot to the top left of the laser apperture, this means that the primary needs some adjustment by means of the three collimation screws which are situated on the rear of the primary mirror assembly:

Here you can see the primary mirror collimation screws, the larger push/pull the mirror, the smaller are locking screws to secure the mirror in place after successfully collimating.

Most telescopes have a push – pull method here, turning anti-clockwise will push the mirror further up the tube, whereas turning clockwise will pull the mirror towards the bottom of the tube, it is very important not to keep turning anti-clockwise because this could result in the screws becoming disconnected from the primary mirror. After an adjustment on a couple of the collimation screws, my primary is now aligned properly as the laser beam returns into the laser apperture:

Here you can see that there is no additional dot, the dot is centered right on the laser aperture indicating primary alignment is complete

Once the laser collimation has been completed, it is easy to verify this with the FarPoint Auto-Collimator, the eyepiece has a mirror inside which allows you to see where the centre spot of the mirror is and will form a slightly pale dot in the middle, if the dot appears in the middle then you have your collimation pretty much spot on after following the above, maybe a very slight adjustment on the primary collmation screws is all that is required, you can see here what the view looks like:

It is also normal on faster telescopes to see the mirror appearing offset as opposed to central to the OTA itself. Once completed, I would typically then perform a star field test and I prefer to use the Multi Star Collimation in CCD Inspector for this, you can of course use the de-focused star method.

I hope you found this useful, I just thought I would share my process in performing collmation to help others who may be on that journey also.