Tag Archives: imaging

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

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.

Sharpstar 20032PNT F3.2 Paraboloid Astrograph Review

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!

ZWO ASI2400MC Pro Full Frame 24mpx camera review

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

A step by step guide to Collimation

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.

SharpStar 15028HNT

After months of trying to get my trusty Sky-Watcher Quattro F4 to work with the ASA 0.73x reducer I decided to go all in on an F2.8 astrograph. After doing some research I stumbled across the SharpStar 15028HNT F2.8 Hyperboloid Newtonian Reflector from my local supplier 365Astronomy.

After toying with the idea and speaking to my good friend Nick from Altair Astro and with the idea of going back to a refractor, I decided that I could not go back to slower than F4 and I wanted something that in essence would work with a bigger sensor than my QHY183M, and the Sharpstar looked like it could work for me, so I placed my order with Zoltan from 365Astronomy and collected it the following day.

Unboxing the scope, I was like a young child at christmas, the scope came with a very sturdy protective hard case and removing the scope out of the case you could immediately feel that a lot of time and effort had gone into producing the 15028HNT.

Aperture: 150mm
Focal Length: 420mm
Focal Ratio: F2.8
Weight: 6kg
Tube Material: Carbon Fiber

With the scope unboxed I started to fit my equipment onto the scope. In order to fit my Sesto Senso I had to rotate the focuser 90 degrees clockwise due to the telescope mounting rings, this is when I noticed an isue that one of the grub screws on the focuser would not tighten and I needed to stop the backlash, fortunately there’s another grub screw on the other side that tightened and stopped the backlash.

Before I attached my imaging equipment, I had to ensure that the telescope was collimated, so I stumbled across the collimation guide which after speaking with my good friend Terry Hancock over at Grand Mesa Observatory who was also evaluating the same scope, we both agreed that the colimation guide wasn’t very well written as it mentioned nothing about collimating the primary. One thing that it mentioned is to remove the corrector, Sharpstar include a tool for you to remove the mounting plate and corrector, but here is a word of advice……..remove this when the telescope is cold, take that advice from someone who tried to remove it whilst it was warm!

I performed a laser collimation with my Concenter Eyepiece to check the secondary, and then a laser to check the primary, now the collimation guide says to remove the corrector, I have done validation with both the corrector removed and the corrector in place, and it made no difference whatsoever, so my opinion is to leave the corrector in place.

With the scope closely collimated, I mounted my StarlightXpress Filterwheel and Camera which with the 15028HNT is an M48 thread for the gear to screw onto.

I will post some images as soon as I have completed some, the weather has been pretty poor (probably because I bought a new scope), but the frames I have got so far are very sharp, pinpoint and I can honestly say I have never seen images come directly off the camera so sharp.

My field of view with the QHY183M is around 1.21 Arcsec/Pixel which gives me a FOV or around 1.81°x1.2° and I love the difraction spikes being at 45 degrees compared to the 90 degrees on the skywatcher and I already have a pretty full target list for this scope ready to go this season.

Apart from the couple of product issues I have experienced (Grub screw on focuser and tube clamp thumbscrew being threaded) I am extremely happy with the scope, it is performing really well and here are a couple of work in progress images that I have started

Dark Shark Nebula Moscaic Panel 1 – 51x300S in Red, 25x300S in Green and Blue
Elephant’s Trunk – 51x300S in 6nm Ha
M45 – Mosaic Panel 1 – 12x150S in R, G and B

After a few weeks, the telescope has held collimation very well, I have not had to perform any re-collimation, I will re-evaluate this in the much colder months of winter.

I am so happy with the scope that I am actually considering a second one for an OSC Camera with a bigger sensor.

M101 / NGC 5457 – Pinwheel Galaxy in RGB

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

PrimaluceLabs Sesto Senso Robo Focuser

Getting the best FWHM in your images is something that I have struggled with when imaging a whole night. As the temperature fluctuates, so does the FWHM in your images, this was a problem I had with my images at the beginning of the season. I looked around and the only focuser I could find was not a stepper motor focuser, so it didn’t offer predictable results. Since I am using the stock focuser for my Sky-Watcher Quattro 8-CF (and it’s a solid focuser at that), I did not really want to change focuser mid-season, so I did some research and landed upon the PrimaluceLabs Sesto Senso ROBO Focuser.

Now my expectations here were pretty low since I tried an electronic focuser and tried to use some sort of Auto Focus routine without any length of success, but when the Sesto Senso arrived I was excited as I looked at it and thought to myself that this would do the job.

Out of the box the Sesto Senso is very solid, good quality feel to it, and came with a bunch of different adapters for different focusers, one specifically for my Sky-Watcher Focuser too. I read the installation instructions a couple of times and set to work on upgrading my scope.

Installation
Installation was fairly easy and straight forward, I removed the slow focusing knob off the focuser and attached the adapter for the Sky-Watcher that came with the Sesto Senso, so within 30 minutes it was successfully fitted. And I can still manually focus with the fast focusing knob on the other side of the focuser:

After all the physical installation was done, I then needed to install the software on the observatory PC, since I image using Sequence Generator Pro, I proceeded to install Sesto Software and the ASCOM driver so that SGPro could talk to the focuser, again this was relatively simple to do. Once this was completed it was important to load up the Sesto software and perform a calibration so that the Sesto Senso knows where the most innner and outer focus positions are.

Setting the Focus Control module in SGPro was a breeze, for this I used a Focusing Mask to get a rough focus and set that point for all of my filters, now the following setting are what works for me really well, but basically:

  • I use 20 data points to achieve focus.
  • Step size between focus points is 20
  • Focus frame is 10 seconds for all filters, this is to get a better normalised focus frame, I was finding 5 seconds was too short and gave un-predictable results.
  • I set it to re-focus after a temperature change of 3.0 Degrees C since the last focus.
  • I re-focus on any centering action which is useful if you use a mirrored telescope like me.
Sequence Generate Pro Auto Focus settings
You can see here that my start off point is 50146, so it will go 10 points either direction of this point at 20 steps per point

I have now been using the Sesto Senso for a few months now and it has not failed me, I maintain a good FWHM value throughout the night and it an awesome piece of kit, well done Primaluce Labs. Is there anything that I would change about it?

Only one thing…….It requires separate power, which in all honesty I can understand why but if I could run the power through USB that would be a bonus.

One problem I have with the Auto Focus routine in SGPro is that in the image sequence, since my filters for LRGB are all parfocal, but my Narrowband filters are not, I only wish to focus on a filter change if it’s going from LRGB to Narrowband to LRGB or Narrowband to Narrowband, unfortunately SGPro doesn’t have that intelligence in the sequence, I am trying to persuade Jared to have that in there to make life that bit more simple.

Anyway I hope this review inspires you to consider this awesome piece of kit, it’s certainly helped me!

NGC6888 – Crescent Nebula in SHO Narrowband

This object is a little tricker for me since I only have a 3-3.5 hour window per evening due to trees and the house blocking my view, this is also the first image that I used the drizzle function within PixInsight to be able to provide a detailed up close version of the image, I was very happy to have captured the brown “Globules” within the nebula to

Crescent Nebula in SHO Narrowband
Same object but with a 2x drizzle function in PixInsight applied

Image Details:
Red Channel – SII Data – 89x300S
Green Channel – Ha Data – 64x300S
Blue Channel – OIII Data – 109x300S

101 Darks, Flats and BIAS Frames used 

Equipment Used:-
Imaging Camera: QHY183M Mono ColdMOS Camera at -20C
Imaging Scope: Skywatcher Quattro 8″ F4 Newtonian
Guide Scope: Skywatcher Finder Scope
Guide Camera: QHY5L-II
Mount: Skywatcher EQ8 Pro GEM Mount
Focuser: PrimaluceLabs ROBO Focuser
Filterwheel: StarlightXpress 7x36mm EFW
Filters: Baader 7nm Ha, SII and OIII
Acquision Software: Main Sequence Software Sequence Generator Pro
Processing Software: Pixinsight 1.8.5

Pegasus Astro Ultimate PowerBox

I spent a lot of time looking at PowerBoxes/USB Controllers, the late Per Frejvall had developed a very nice Remote USB Hub but of course with the passing of Per, these are no longer available. I looked at two hubs, the HitechAstro Mount Hub Pro abnd the one I settled for was the Pegasus Astro Ultimate PowerBox.

Unboxing the PowerBox I was pleased with the build quality, they even ship mounting brackets for you to be able to mount it onto your setup, here’s an image of mine mounted on top of my Sky-Watcher Quattro:

Pegasus Astro Ultimate PowerBox on Imaging Setup

I loaded up the software onto the observatory PC and again pleasantly surprised at how easy it was to get started and configure the names of the powered devices connected as well as names for each of the dew heaters, in the following image you can see my power connected devices and my dew heater for my guider camera:

Screenshot of Control Software

I configured the software to automatically power my devices the moment the unit is switched on, so what do I have connected to the PowerBox?

  • QHY5L-II Guide Camera
  • StarlightXpress USB Filterwheel
  • PrimaluceLabs ROBO Focuser
  • EQ8 Pro Mount PC-Direct Cable

I didn’t connect my QHY183M at the moment as I discovered that during image download it seemed to cause a timeout on the QHY5L-II Camera, I have raised a ticket with Pegasus Astro on this one. From a Power perspective, I only have my QHY183M and my Rear Fan assembly/heater connected as I currently do not have the power cable to connect directly to the hub for the EQ8 Pro (On Order). There is also a temperature sensor for the ultimate version, which works well as an interface for Sequence Generator Pro and my Auto Focuser routines.

I have been using the Hub now for a good few months, I am pretty happy with it, am I totally happy you might ask, well to be honest there’s a couple of niggly things that I have emailed Pegasus Astro about (awaiting a response):

  • Voltage. I am running 13.8V regulated bench power supply capable of delivering up to 15A which is powering the hub, however when devices such as the camera, dew heater, fan assembly are all running, the voltage level drops down to around 12V according to the software, I would not expect this to do so, I would expect it to remain 13.8V. My EQ8 Pro mount is powered by the same supply (but not through the hub currently) and during slew the voltage in the software does not change, so it’s obviously something being caluclated within the hub somewhere.
  • Issue with USB3 Camera (QHY183M) is still outstanding
  • When you set the power to the dew heater for example I always run it at 170, however when the software restarts you have to manually go and set this again
  • Ability to reboot or “Disconnect” a specific USB Port remotely would have been nice.

The main reason I wanted something like this was the ability to reboot the hub remotely, with standard USB Hubs this is not possible, as above, I would love to have a bit more granularity on this and have it on a per USB port but it works well for me right now.


QHY183M Review – Part 1

After much waiting (due to delays on Sony Sensors) I have finally received my QHY183M ColdMOS camera from QHYCCD which I collected from ModernAstronomy last weekend, so I apologise for the really bad weather we’ve had.

As you all know, for the past few years I have been using an Atik 383L+ Mono 8.3Mpx CCD Camera, so when QHY announced the QHY183C I immediately asked them if there was going to be a mono version to which they said….Yes!

So firstly you might ask why I chose the QHY183 camera?  Well the simple reason for this is that it offered me a higher pixel resolution for almost the same field of view that my Atik 383L+ offered, however there were other factors that swayed my decission:

  • Back Illuminated Sensor
  • High Quantum Efficiency (QE)
  • Optimal Cooling
  • Lightweight

So let’s first of all talk about the back illumination and what this means to astrophotography.  Typically CMOS sensors are orientated with the light receiving surface and the transistors/wiring facing the light, so when imaging it is possible to get reflections of light bouncing off the circuitry, with a back illuminated sensor, all the circuitry are on the underside of the surface that faces the light, thus elliminating the possibility of reflections bouncing off the transistors, the following image shows this in a bit more detail (Courtesty of QHYCCD):

So obviously the more light we can get to the imaging surface the better it is for our data acquisition, every photon counts right?!

The QHY183M has an extremely high Quantum Efficiency (QE) of 84% which means that more data is absorbed by the chip than my previous imaging camera which had a QE of just over 60% based on the KAF-8300 sensor from Kodak.

One of the first things I tested when I unpacked the camera was the cooling system, I wanted to know how good the cooling system was, QHY stated between 40-45C Delta, so considering the outside temperature was +5C I managed to get the camera down to -41.6C which was a delta slightly above the 45C promised by QHY, so considering I typically image at -20C this now means I can image when the outside temperature at night is even as high as +25C which typically doesn’t happen in the UK.  I also noticed that the QHY183M uses less current than my 383L+ did to get ot the same temperature, so another bonus of less power requirement.

Weight is always an astrophotographers enemy, so it was much to my delight that the QHY183M weighs a lot less than my ATIK 383L+ did, the 383L+ weighed in around 700g and the QHY183M weighs in around 450g.

Out of the box
My first impression of the camera is that it is well built, a bit more of a compact design in comparison to my previous camera, has a USB3.0 connector (even though I am still using USB 2.0) and has a port to connect a dessicant tube to if required.

Software Installation
Driver installation was relatively straight forward, if you are using a third party imaging program like Sequence Generator Pro, make sure you install the ASCOM drivers so that SGPro can then speak to the camera.  In SGPro there are options for Gain settings, according to QHY the unity gain for the 183M is 11, so I have mine set to this value in SGPro.

Image Download Speed
After completing my dark frames library, I noticed that the download speed from Camera to Observatory PC was much much faster than my Atik was, even though I am using the same USB 2.0 Hub, on the Atik it could take anywhere up to 20 seconds to download the image at 1×1 binning, obviously the QHY183M is a much bigger sensor at 20mpx, however the image download time is circa 5 seconds which reduces image acquisition time greatly for multiple exposures.

Dark Frames
My dark frame library is completed, below are four different exposure times, 90, 180, 300 and 600 seconds, each image consists of 25 frames combined using PixInsight

90 Seconds:

180 Seconds:

300 Seconds:

600 Seconds:

As you can see the darks are really good, if you stretch out the images you will see the AMP glow on the right side of the image, this will be removed in dark frame subtraction and is a common artifact on all CMOS based imagers.

I did have the occasional icing issue on my 383L+, however the QHY183M has a heated optical window, so time will tell on how often I will need to use the dessicant tube.

Conclusion so far…before imaging

Pros:

  • Excellent design.
  • Lightweight.
  • Very predictable cooling system cools to -45C below ambient.
  • Cooling system is much quieter than my previous camera
  • Less current draw versus my previous camera.
  • Easy software installation.
  • Very fast download speed of around 5 seconds per frame at 1×1 Binning.
  • Very high QE of 84%

Cons:

  • AMP glow, I am probably being a bit mean considering all CMOS based cameras are subjected to this.
  • M42 thread on the camera is not long enough for the StarlightXpress EFW, I had to place a piece of card between the camera and the Filterwheel otherwise the camera just keeps spinning round and doesn’t tighten.
  • There’s no electronic shutter like my previous camera, which means for my dark frames it has to be completely dark in the observatory

I hope this review is beneficial to you all, especially if you are considering either the 183C or the 183M.  I will post part 2 of my review when I have actually got it all focused and acquired some photons from the sky.