Tested the QHY268M + Review

Hi, 

Thank you for the review ! I also use MODE1 all the time, as I never needed some of the specific advantage of other modes.
I was surprised by the typical exposure times you mentioned, I would expect the longest sub exposure time (300-600) to be at gain 0. Maybe there is a confusion.

I would like to mention I had fogging issues (I never had with my previous CCD). Fogging can occur if cooling is too quick.
I did not find it was easy and quick to use the refillable desiccant, I finally decided to keep the tube screwed on the camera.

Overall I could not agree more that the performance of this camera is excellent.

Hi  Rouzbeh, Thank you for writing this review.  I too come from years of mono imaging with CCD, and the Sony IMX571 and IMX455 chips camera have sparked my interest in moving to CMOS.  Prior CMOS cameras always had too many draw backs for me. Over the years I have imaged with  various Starlight Xpress CCD cameras (HX-916, SXVF-H9, Trius SX-694, Trius SX-814 and Trius SX-46)  The Sony ICX-694 had a read noise of 3 with QE of 70%.  Almost as good and better than some CMOS. The H9, SX-694 and SX-814 do not require dark frame subtraction due to their low dark noise.  So all the talk of from new imagers about how dead CCD is and how great CMOS is, did not equate with the Sony CCD ICX694 and 814.  I think new CMOS imagers have never imaged with a top quality Sony CCD.

That being said. The discussion (primarily Cloudy Night) about the IMX571 encoraged me to consider it. I purchased the QHY268M and QUICK 2" x 7 FW.  It arrives Jan.4.  I have mostly been using a SX-47 (Kodac KAF12600 6nm pix).  I love the size, but hate the long download times.  The need for a shutter has also irritated me. It's large 6nm pixels limited me to longer focal lengths.  I have been using it with a Tak FSQ106ED at F5.  Stars are nice corner to corner with the 27mm x 21.6mm size chip.

I realized that I could achieve the same field of view as the SX-46/FSQ106 with the IMX571 chip using the FSQ106 at F3.6.  The smaller IMX571 3.76 nm pixels allowed me to use the Tak 0.73x reducer and still get good sampeling.  This should shorten my sub-exposures a lot.  I have been using 600 and 900 sec with the Sx-46 to get the faint stuff.  I am hoping to obtain the same S/N  with the QHY268M at 300 to 700 sec using narrow band filters.  I live in Bortle 7 skies and have to use narrow band.

I saw that your download time for the QHY268 was 3sec with USB3.  I was hoping for a little faster.   I like to remotely focus at full 1x1.
I run a Cad5 cable into the house from a POD observatory through a USB2 converter.

I was glad to hear there was no tilt issue.  This is something I have been concerned about. I choose QHY over ZWO due to decussions about ZWO quality controll. Mainly "Oil Gate". the issue with oil from the heat transfer pad leaking onto the chip and ZWO's lack of response for a whole year.  I also understand QHY has resolved it's driver issues.  I will be using MaximDL v6.

Thanks again for the review.

Lynn K.

Lynn K:
Hi  Rouzbeh, Thank you for writing this review.  I too come from years of mono imaging with CCD, and the Sony IMX571 and IMX455 chips camera have sparked my interest in moving to CMOS.  Prior CMOS cameras always had too many draw backs for me. Over the years I have imaged with  various Starlight Xpress CCD cameras (HX-916, SXVF-H9, Trius SX-694, Trius SX-814 and Trius SX-46)  The Sony ICX-694 had a read noise of 3 with QE of 70%.  Almost as good and better than some CMOS. The H9, SX-694 and SX-814 do not require dark frame subtraction due to their low dark noise.  So all the talk of from new imagers about how dead CCD is and how great CMOS is, did not equate with the Sony CCD ICX694 and 814.  I think new CMOS imagers have never imaged with a top quality Sony CCD.

That being said. The discussion (primarily Cloudy Night) about the IMX571 encoraged me to consider it. I purchased the QHY268M and QUICK 2" x 7 FW.  It arrives Jan.4.  I have mostly been using a SX-47 (Kodac KAF12600 6nm pix).  I love the size, but hate the long download times.  The need for a shutter has also irritated me. It's large 6nm pixels limited me to longer focal lengths.  I have been using it with a Tak FSQ106ED at F5.  Stars are nice corner to corner with the 27mm x 21.6mm size chip.

I realized that I could achieve the same field of view as the SX-46/FSQ106 with the IMX571 chip using the FSQ106 at F3.6.  The smaller IMX571 3.76 nm pixels allowed me to use the Tak 0.73x reducer and still get good sampeling.  This should shorten my sub-exposures a lot.  I have been using 600 and 900 sec with the Sx-46 to get the faint stuff.  I am hoping to obtain the same S/N  with the QHY268M at 300 to 700 sec using narrow band filters.  I live in Bortle 7 skies and have to use narrow band.

I saw that your download time for the QHY268 was 3sec with USB3.  I was hoping for a little faster.   I like to remotely focus at full 1x1.
I run a Cad5 cable into the house from a POD observatory through a USB2 converter.

I was glad to hear there was no tilt issue.  This is something I have been concerned about. I choose QHY over ZWO due to decussions about ZWO quality controll. Mainly "Oil Gate". the issue with oil from the heat transfer pad leaking onto the chip and ZWO's lack of response for a whole year.  I also understand QHY has resolved it's driver issues.  I will be using MaximDL v6.

Thanks again for the review.

Lynn K.

Hi Lynn,

Glad you liked the review. I agree with all the points you made and heard about both those issues, the oil and tilt issues with ZWOs. I had a few ZWOs as well and exactly as you said, the old CMOS sensors were not really comparable to these two new IXM sensors.
I'm surprised people still but cameras like the 294, 183, and 1600!

The download time was quoted from QHY, I cant tell the exact time it may be 1 to 2 seconds even, its hard to measure. I suppose a lot of it depends on your C, USB cable, etc...

Overall I think you will love the camera. Looking forward to your results.


Rouz,
https://linktr.ee/Rouz_Astro

Nice review. I have the QHY268C, OSC version & have been very pleased with it so far.

Nice review. I have the QHY268C, OSC version & have been very pleased with it so far.

Thank you for commenting! 
I havent used the OSC, I supposed it should be equally good.


Rouz,

read noise, quantum efficiency, full well, etc. basically identical. My sharpcap pro sensor analysis on my QHY268C looked almost identical to yours done on your QHY268M. the 268C version does lack the internal humidity sensor that the 258M version has. Apart from the bayer matrix vs. mono, that is the only difference that I can determine.

So far I have only had my QHY268C for about a month, so still getting to know it. Thus far I have only used mode 0. I've tried gain 0/offset 30 for broadband & also gain 30/offset 45 for narrowband. I have not tried high gain mode yet. 

Since you didn't mention it in the review, curious your own thoughts/experiences using mode 0 with it?

Nice review. I have the QHY268C, OSC version & have been very pleased with it so far.

Thank you for commenting! 
I havent used the OSC, I supposed it should be equally good.


Rouz,

read noise, quantum efficiency, full well, etc. basically identical. My sharpcap pro sensor analysis on my QHY268C looked almost identical to yours done on your QHY268M. the 268C version does lack the internal humidity sensor that the 258M version has. Apart from the bayer matrix vs. mono, that is the only difference that I can determine.

So far I have only had my QHY268C for about a month, so still getting to know it. Thus far I have only used mode 0. I've tried gain 0/offset 30 for broadband & also gain 30/offset 45 for narrowband. I have not tried high gain mode yet. 

Since you didn't mention it in the review, curious your own thoughts/experiences using mode 0 with it?

I used mode 0 for a few images but I believe mode 1 should be better.

In mode 1, if you need more FWC at gain0 there is about 50k of FWC which is quite a lot for these small pixels. That + the bayer matrix.

The DR if higher in mode 1 as well, both at gain 0 and gain56.

The other modes would be useful in a situation where you need a lot of FWC, perhaps with a lum filter, mono sensor and fast optics?

I suppose there is no perfect setting, but which is best for which senario.

I living in bortle 7+ and thus far have only used this camera with my F4 Newtonian, so a fast setup. Thought the added full well would help mitigate some of the heavy light pollution I deal with. Was somewhat concerned that high gain mode would over saturate too easily in my conditions, but will try it at some point. Before long I will be trying the QHY268 with my slower F9 rig, so high gain probably wise there. 

curious the bortle scale where you’ve done most of your evaluation of this camera?

I have got a QHY268 mono camera the best gain is 102 offset 76 powerful camera used this gain with narrow band
Martin Williams

I have had a QHY268M since June of 2021.  I initially used Mode 1 (High Gain) exclusively, with Gain 56 and Offset 10, in order to get the lowest possible read noise.  It is a good choice with narrowband imaging, like H-alpha shots of nebulae.

I have been playing around with Mode 3 (Extended Fullwell 2CMS) lately, shooting LRGB images of small, faint galaxies with a 100 mm refractor, a tough test for any camera.   Small galaxy images often suffer from overexposed stars because of shooting longer luminance subs to capture the faint targets.  Mode 3 with Gain 14 provides a full well depth that is approximately four times greater than Mode 1, Gain 56, meaning that fewer stars become overexposed.  The cost is higher read noise.

I have been pleased with the performance of Mode 3 for luminance imaging.  Although the read noise is higher, I have generally found that it is swamped by sky noise for 5-minute luminance exposures, so it has very little effect.  The number of "burned out" star cores is definitely reduced in a direct comparison of Mode 3 vs. Mode 1. 

For a more detailed discussion of the modes and some quantitative analysis of the camera's performance in different modes and various Gain settings, please visit this extensive discussion on Cloudy Nights.

Cloudy Nights: Received my QHY268M

https://astrob.in/m0dwbm/0/
Running Chicken taken F5.6  Sky Rover 102mm super apo QHY 268 mono gain 102 offset 76 i dont know where you getting your information from i have been imagining for 5 years i tested the camera out on different gains and offsets if this helps gain 102 and 76 offset works fine a bit more grunt with out losing the quality of the image. Worth a try
Martin Williams

I have had a QHY268M since June of 2021.  I initially used Mode 1 (High Gain) exclusively, with Gain 56 and Offset 10, in order to get the lowest possible read noise.  It is a good choice with narrowband imaging, like H-alpha shots of nebulae.

I have been playing around with Mode 3 (Extended Fullwell 2CMS) lately, shooting LRGB images of small, faint galaxies with a 100 mm refractor, a tough test for any camera.   Small galaxy images often suffer from overexposed stars because of shooting longer luminance subs to capture the faint targets.  Mode 3 with Gain 14 provides a full well depth that is approximately four times greater than Mode 1, Gain 56, meaning that fewer stars become overexposed.  The cost is higher read noise.

I have been pleased with the performance of Mode 3 for luminance imaging.  Although the read noise is higher, I have generally found that it is swamped by sky noise for 5-minute luminance exposures, so it has very little effect.  The number of "burned out" star cores is definitely reduced in a direct comparison of Mode 3 vs. Mode 1. 

For a more detailed discussion of the modes and some quantitative analysis of the camera's performance in different modes and various Gain settings, please visit this extensive discussion on Cloudy Nights.

Cloudy Nights: Received my QHY268M

Yes mode 3 (2CMS) is an excellent choice for LRGB, specially from light polluted areas where read noise matters less.

The FWC is a lot higher and that does help with keeping the stars bright.

Thanks for sharing.


Rouz

Martin Williams:
https://astrob.in/m0dwbm/0/
Running Chicken taken F5.6  Sky Rover 102mm super apo QHY 268 mono gain 102 offset 76 i dont know where you getting your information from i have been imagining for 5 years i tested the camera out on different gains and offsets if this helps gain 102 and 76 offset works fine a bit more grunt with out losing the quality of the image. Worth a try
Martin Williams

I'm not sure how you tested the camera, one good way is Sharpcap sensor analysis and another is Pixinsgiht CCD parameters.
I have found these useful after 19 years of imaging with CCD and CMOS cameras.

Martin Williams:
Sorry but QHY EMAILED ME 102 GAIN IS BEST AND MY IMAGE I TAKEN OF THE RUNNING CHICKEN STACKS UP SO WHY SHOULD I CHANGE CAN YOU EAXPLAIN
and what is wrong with the image of the running image i took when i was emailed from QHY to use gain 102 for best results i have used gain 56 it is not so 
good as gain 102 look you can use what your comfortable with i am saying what i feel  and used the QHY 268 mono which is the best gain that works and the proof is in the image that you take props this might help and i have taken some quality images with this camera the only way you find out is to try the camera on different gains and offsets you self instead of all this jargon about gain and offsets what works and dont you have got to try it your self when your taken images
Astrophotography is a big learning curve.
Martin Williams
Perth WA hills

Once you look at the full well capcity at gain 102, you realize there is nothing there. 

I recommend you look up what gain does for read noise and FWC and the relationship between them (Dynamic range). These are the basics of digital imaging.
It will  help you improve the images dramatically. 

Agreed, it can be complicated with a steep learning curve. Its always best to research and understand the fundamentals and gain experience from the community of fellow astrophotographers.

"QHY said so" is not always the best solution, I personally would like to know why. 


As you asked to point out areas that can be improved in that image. I would recommend the following:
https://www.astrobin.com/full/m0dwbm/0/

• Large stars are bloated (large white blobs)
[*]
• Background is black (clipped)
[*]
• Core of nebula is washed out (lack of dynamic range)
[*]
• Stars in upper corners indicating tilt
[*]
• Stars in outer perimeter are not round indicating telescope is not correcting the corners well
[*]
• Excessive noise reduction
[*]
• Excessive sharpening

I hope these are helpful;.



Rouz,