Tag Archives: imaging

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.

Skywatcher Quattro 8-CF Imaging Newtonian

After much deliberation and conversations back and forth with Bernard at Modern Astronomy, I finally decided to go for the Skywatcher Quattro 8-CF 8” F4 Reflector, there was a number of factors that helped me reach this decision, most of it was the British weather being so unpredictable that I needed to get as many photons for my images in the shortest available time.  I was used to imaging at F7.5 that the F4 was going to give me significantly faster optics, I also opted for the Carbon Fiber version purely from a thermal expansion perspective as it was going to perform better than the steel tube version.  I also opted for the 8” as the Native focal length of 800mm suited me perfectly, and I plan on getting the Keller reducer to bring it down to 560mm @ F2.8.

Setup and Collimation
When I received my telescope and optically matched Aplanatic Coma Corrector, I was impressed with the build quality of the scope itself, internal baffles to boost contrast as well as eliminate stray light, and the focuser is pretty sturdy for a stock focuser, and quite easily handles the weight of my CCD and Filterwheel.  I mounted the telescope next to my Guide scope on my Skywatcher EQ8, I wish they had provided a Losmandy plate with the telescope, but the Vixen style bar still worked out well.  After balancing the scopes on the mount I was ready to check the collimation, for this I used my Farpoint Collimation Kit, firstly the laser to ensure it hits the centre spot of the primary, and the laser return reached the centre point of the laser collimator itself, the adjustments required were very minor.  After this I verified the collimation with the Farpoint Cheshire and it verified that the collimation was correct, only thing left to do was a star test, for this I used a 10mm Eyepiece and a fairly bright defocused star, the star was spot on, I could see all the concentric rings.  I then proceeded to perform the same star test with the CCD and the Aplanatic Corrector to verify, which of course it did.

Scope Details:
Focal Length: 800mm
Apperture: 8 Inch
Focal Ratio: F4
Tube Composition: Carbon Fiber
Focuser: 2″ Dual Speed Linear Power Focuser

First light
My first target for 2016 is the Iris Nebula, my first set of frames came through and for a 5 minute exposure I was impressed with how much data I had collected, data that would have taken over 15 minutes to collect on the F7.5 refractor I now use as a guide scope, I managed to finish a target off within a few days of imaging rather than over a multitude of nights

I have also not had to re-collimate the scope or adjust the focuser on the scope over the few weeks I have had it, so overall I am above and beyond happy with my decision and I am now able to image targets in a shorter timeframe which in the UK you have to grab every clear sky you can

A few months on
I have had to re-collimate the scope 0 times, even after removing the primary mirror assemply for cleaning, the focuser is still rock solid and holds the camera gear extremely well.   I have made an addition to the scope, I have added a fan system to the rear of the primary mirror, the fan also has some nichrome wire which allows the air being blown around the primary to be just above the dew point which prevents dew forming on the primary and believe it or not the secondary also, even in high humidity sessions.

Build Quality: Extremely pleased with the build quality of the scope, even the focuser is sturdy and holds all of my gear really well

Collimation: Extremely easy with the right tools, it has required no further collimation in the months that I have now owned the scope

Improvements: Could have come with a fan assembly, most of the other F4 scopes from other vendors do

Conclusion
After months of usage, I have produced some really good images in short timeframes due to the fast F4 ratio, I am looking forward to using this scope again next season with 3nm NarrowBand filters and possibly the Keller Reducer to bring it down to F2.8