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.
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:
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.
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.
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:
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.
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:
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.
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.
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:
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.
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.
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!
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.
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.
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?
ASI2400MC
ASI128MC
ASI6200MC
Image Sensor
IMX410
IMX128
IMX455
Pixel Size
5.94
5.97
3.76
Full Well Capacity
100ke
76ke
51.4ke
Cooling Delta
-35C
-35C
-35C
Resolution
6072×4042
6032*4032
9576×6388
ADC
14-Bit
14-Bit
16-Bit
Read Noise
1.1e-6.4e
2.5e
1.2e-3.5e
DDR Buffer
256MB
256MB
256MB
QE
>80%
>53%
>80%
FPS (Video)
8
5
2
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 FilterElephant’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
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
Set of hex drivers (For adjusting the secondary mirror)
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.
As many of you know, I have been using QHY cameras for a while, but with my plan to move to a RASA telescope next year and wanting to image with a bigger sensor than the QHY183M I decided to go for a bigger sensor but moving away from Mono, the latest addition to the QHY familly is the QHY268C Photographic Version. I had been talking to the QHY team for a long time about this particular camera, and finally I have one.
The QHY268C is a once shot colour camera based on the APS-C Sized back illimunated Sony IMX571 sensor, the camera has a true 16-Bit Analog to Digital Convertor (ADC), now there are a few camera models out there using this sensor, cameras such as the ZWO ASI2600, but one thing that sets the QHY268C apart from the others is the ability to have a 75ke full well capacity which is 25ke higher than the ZWO ASI2600. In my opinion, when imaging at fast focal ratios, a higher full well is desired to protect the colour around bright stars for example.
Opening the box I was greeted with a camera that was bigger and heavier than my 183M, but then the sensor is much bigger than the 183M anyway so this would be expected, but what I did not expect is the additional items that came with the camera:
Inside the box was:
QHY268C Photographic Version
UK mains plug for 12V AC adapter
12V AC adapter
Car 12v power cable
Self locking power cable
1.5M USB 3.0 cable
Dessicant drying tube
Self centering adapter plate
M54 to M48 adapter plate
M54 to 2″ nose adapter
A range of spacers to give you from 0.5mm to 13.5mm spacing
Associated screws for spacing adapters
QHY cameras have come along way since I bought my QHY183M, one of the things QHY has really worked on is amp glow, my early version of the QHY183M was renowned for was amp glow, which could be removed in image calibrations, but the QHY268C produces no amp glow whatsoever, below is a dark frame of 600S taken at -13.5C and you can clearly see there is no evidence of amp glow.
Single frame 600 seconds, Gain 26, Offset 30, -13.5C – Mono (Not Debayered)
Attaching to the telescope was pretty straight forward as I had already planned the imaging train before the camera arrived, since I will be using the SharpStar 15028HNT F2.8 Paraboloid Astrograph which has an M48 thread, I decided to keep the whole imaging train at M48 except for the camera of course which has an M54 thread, so I did not actually need to use any of the adapters that came with the camera, the reason for this is because I wanted to include a filter drawer, so my image train consists of the following (from telescope to camera)
As you can see with all the above I reach my desired back focus of 55mm perfectly, if I was not going to be using a filter drawer (For my Optolong L-Pro and L-eXtreme filters), I would probably have stuck with the spacers that came with the camera. Below is a picture of the camera successfully connected to the telescope.
As far as settings go, after speaking with QHY on this at great length, I will be imaging in Mode 0 (Photographic mode) to avail of the massive 75ke full well, offset I will leave at 30, but Gain I will use two different settings, I will use Gain 0 for most bright objects with the L-Pro filter, but for the L-eXtreme, I’ll probably set a gain level of 26, luckily with SGPro I can set the gain level per object. From a cooling perspective I always image at -20C, one thing I have noticed is that this camera cools to exactly -35C below ambient, I tested this when the ambient temperature was 20.10 degrees, and the camera cooled down to -14.9C, it was always 25C lower until the ambient dropped below 15C and the camera remained at my setting of -20C.
The build quality of the camera is as expected having owned a QHY183M, one thing I did notice is that the fan in the QHY268C is much quieter than the 183M. Technical Details of the camera:
I can’t wait to get imaging with this camera, I have a very aggresive target list for this year in both RGB and Narrowband with the Optolong L-eXtreme filter, I will write part two of the review once I have some actual imaging data. Time to build my dark library.
I was lucky enough that Terry from StarlightXpress sent me a Lodestar X2 for me to test to see how well it performed against my existing guider camera, so it only seemed fair that I provide my feedback via an equipment review. Many who know me know I have been using a QHY5L-II camera as a guide camera for a few years now but after seeing a few of my fellow astrophotographers using the Lodestar cameras it seemed silly not to try one out.
In comparison to the QHY5L-II the Lodestar X2 is a true CCD camera and not a CMOS camera, so immediately this would yield some higher sensitivity in what stars can be selected. One thing that is immediately noticable between the cameras is the Lodestar X2 is longer than the length of the QHY5L-II.
Just to add some more comparisons:
QHY5L-II
Lodestar X2
Sensor
Aptima MT9M034
Sony ICX829
Sensor Type
CMOS
CCD
Sensor Size
6.66mmx5.32mm
6.47mmx4.81mm
Pixel Size
3.75um
8.2umx8.4um
MPX
1.2mpx
0.4mpx
QE
74%
77%
Length
54mm
85mm
Weight
45g
50g
Cost (27 Aug 2019)
£175
£378
The first time I used the Lodestar X2, I was shocked at how many stars were in the field of view, for the same 2 second exposure I usually guide at there was a lot of stars to choose from, far more than I could see with the QHY5L-II, there is probably a number of reasons for this, higher sensitivity of the CCD Sensor, slightly higher QE, but also the FOV, with the QHY5L-II on my 8″ Quattro with a 0.73x reducer it would yield a field of view of 0.47°x0.35°, the Lodestar X2 on the other hand would yield a field of view of around 0.6°x0.48°.
Since I use PHD2 for guiding one thing that was immediately apparent was the built in driver for StarlightXpress cameras, I asked Terry which would be the best to use, he said either, it makes no difference, so I tested this and he was right, the in built driver and ASCOM driver produced the exact same result, I remember specifically with the QHY5L-II that QHY recommend you do not use the in built driver and always use the ASCOM driver. When firing up the Lodestar X2 in PHD2 I built my dark frame library in order for me to see how good the ICX829 was for noise, so I compared the 2 second exposures and there was very little difference between using a dark frame library versus not using one, the QHY5L-II definitely requires a dark frame library in PHD2 that’s for sure!
My first night of guider testing seen a little bit of odd behavoiur with the Lodestar X2, since I am using the Pegasus Astro Ultimate USB Hub, I had everything connected in there, including the QHY183M which is a USB3.0 camera albeit connected to a USB 2.0 hub. When the camera was downloading the image the Lodestar would display an array of dots on the screen. Terry confirmed that it was an indication that it was dropping down to USB 1.0 speed. It turns out that when I did the same thing with the QHY5L-II as the guider camera, the QHY5L-II would actually go unresponsive according to PHD2, so I moved the imaging camera to a dedicated USB 3.0 port on the Intel NUC and never had a repeat of the issue on either camera.
PHD2 has no issues picking up and selecting a guide star, there’s plenty of stars to choose from
Conclusion The Lodestar X2 is awesome as a guide camera, it works extremely well, very sensitive, the only drawback in my opinion is price, at over double the price of the QHY5L-II camera maybe a tad out of some folks price range.
M101 / NGC5457 or most commonly known as the Pinwheel Galaxy is a face on spiral galaxy in Ursa Major and has a distance of around 21 million light years from Earth.
The QHY183M picks up quite a lot of the Ha detail in this galaxy without me having to image separate Ha Filter data
Image Details:
101x150S in R
101x150S in G
101x150S in B
Total Capture time: 12.6 Hours
Acquisition Dates: Feb. 27, 2019, March 29, 2019, March 30, 2019, April 1, 2019, April 11, 2019, April 12, 2019, April 14, 2019
All frames had 101 Darks and Flats applied
Equipment Details:
Imaging Camera: Qhyccd 183M Mono ColdMOS Camera at -20C
Imaging Scope: Sky-Watcher Quattro 8″ F4 Imaging Newtonian
Guide Camera: Qhyccd QHY5L-II
Guide Scope: Sky-Watcher Finder Scope
Mount: Sky-Watcher EQ8 Pro
Focuser: Primalucelab ROBO Focuser
FIlterwheel: Starlight Xpress Ltd 7x36mm EFW
Filters: Baader Planetarium RGB
Power and USB Control: Pegasus Astro USB Ultimate Hub Pro
Acquisition Software: Main-Sequence Software Inc. Sequence Generator Pro
Processing Software: PixInsight 1.8.6
The Needle Galaxy is located int he constellation of Coma Berencies and is an edge on spiral galaxy at a distance of 30-50 million light years from earth
Image Details:
101x150S in R
101x150S in G
101x150S in B
Total Capture time: 12.6 Hours
Acquisition Dates: Jan. 28, 2019, Feb. 3, 2019, Feb. 25, 2019, Feb. 26, 2019, Feb. 27, 2019, March 26, 2019, March 29, 2019, March 30, 2019, April 1, 2019
Equipment Details:
Imaging Camera: Qhyccd 183M Mono ColdMOS Camera at -20C
Imaging Scope: Sky-Watcher Quattro 8″ F4 Imaging Newtonian
Guide Camera: Qhyccd QHY5L-II
Guide Scope: Sky-Watcher Finder Scope
Mount: Sky-Watcher EQ8 Pro
Focuser: Primalucelab ROBO Focuser
FIlterwheel: Starlight Xpress Ltd 7x36mm EFW
Filters: Baader Planetarium RGB
Power and USB Control: Pegasus Astro USB Ultimate Hub Pro
Acquisition Software: Main-Sequence Software Inc. Sequence Generator Pro
Processing Software: PixInsight 1.8.6
