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Old 17-05-2021, 12:46 PM
Alchemy (Clive)
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QHY268C Mini Review

Disclaimer..., this is provided as a resource for those interested in the camera, not a commentary of processing or other equipment.

The QHY268C retails as of May 2021 for approx $3300 AU

I have been waiting for CMOS to reach a point where some of the limitations, in particular, banding and amp glow, to be resolved. this camera seems to have done that.

theres a lot of specifications, modes etc that i will not go into, its more of a practical limited real world test, without scientific analysis. WYSIWYG.

There are a number of modes (4) to choose from, each having its own dynamic range well depth and noise read. After reviewing the charts and with no other basis i chose high gain at 0 with an offset of 30, this made sure the signal was not clipped. this gives it a practical range of 14 stops, significantly more than my qhy8 and qhy9 mono.

Out of the box everything you need is supplied, although some of the spacers varied from the website information. for the simplest use, one can download the QHY package which includes a capture program and drivers, my experience was it worked, no glitches.

upon opening the capture program, you select the mode (high gain in my case) and once open set the offset an gain in the capture to your required level. note that if you select a different gain you will need to set it each time in the planner table.

temperature can then be set... of note qhy website suggests not to drop temperature too quickly, how reliable this information is i dont know, but with the qhy9 i just set it to -20 and auto temperature and left it alone without a care, on this one i set it around 30% power and leave it to stabilize, and if needed rise it again 10% , then if its stabilised around the temperature i want i set it to auto -10. the cooling on this camera is nowhere powerful as the qhy9 as i can drop it 50 below ambient.
with time used for focusing setting up guiding etc, by the time you are ready to image its all good. i chose -10 simply as most of the year thats achievable by the specs, and it lessens the required dark frame library.

other things of note, the glass screen has no UV/IR coating, it would appear more attention has been given to antireflective coatings, of note the one that came with the qhy9 was appalling and replaced quickly, i have found that on a star of magnitude .6 i was getting minor reflections on the 268, the assumption is reflections from the glass to the Astronomik uv/ir filter and back, i have not noticed it since on less bright stars. to fit the filter i have a ZWO filter drawer, of note i havent seen any light leaks as per other reviews.

the 3 screw adapter allows camera rotation, this seems like great idea unti you realise with the filter drawer the filter is rotated with respect to the chip, each time you move it you need different flats (found that out the hard way) it woud be nice if there was a callibration marker on the outside if you had this i mind.

onto the interesting stuff.... does it work? is it noisy? as they say a picture says a thousand words so.....shot through a FLT132 bortle 3.3 skies

PICTURE 1 centre of a 1:1 single 5 minute sub not debayered showing hot pixels and exposure range of M83 as by screen stretch in pixinsight. no further development.

PICTURE 2 the same sub now debayered in pixinsight and the screen stretch applied.

PICTURE 3 Stacked 13 frames of 5 minutes no dithering (heres where i worked out each night needed different flats if youve rotated the camera) sso just one nights frames (cloud rolled in as per melbourne), so stacked in deepsky stacker with color calibration, median for lights, 80 darks average, 20 flats average, 20 dark flats average. no bias files. then the autosave file histogram stretched in pixinsight and absolutely minimal processing. you could get more data and deconvolve etc for a better image. but this is something a beginner could achieve easily.

PICTURE 4 same as picture 3 but now stetched to show residual noise.

PICTURE 5 50 % resolution crop

PICTURE 6 25% resolution full frame with minimal cropping

so is it any good, for ease of use and the fact i could get a useable picture from an hour of data, its going to appeal to the time constrained cloudy skies dweller. (if i lived in a better location than Melbourne id get the mono version), time will tell and im interested in how it responds to filters etc. but for now im happy enough, in due course i may get the mono version as well, but i already have a mono camera and i moved the qhy8 on some time ago.

having had the opportunity to process some of martin pughs data, its something of an eye opener, and now im not overly fussed if mine's not the worlds greatest data, one can always spend more and more money in pursuit of excellence, and its out of my budget.

happy to answer any simple practical questions i can about the camera. i wont get into the technical level of detail some here can extract.
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  #2  
Old 17-05-2021, 01:54 PM
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multiweb (Marc)
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Cool review Clive. Impressive indeed for such a short integration time.
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Old 18-05-2021, 09:41 AM
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Nikolas (Nik)
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Quote:
Originally Posted by Alchemy View Post

The QHY268C retails as of May 2021 for approx $3300 AU

This is where I stopped reading
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Old 20-05-2021, 04:56 PM
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Good review. I am finding my QHY600m to be a nice little beastie but it needs to be tamed.

One thing I might add which is a bit of an issue with CMOS. None of them have shutters. That means taking darks mean you have to remove the camera (which is extremely sensitive to tilt) and then take darks in a dark location with some sort of cap (the supplied cap is not lightproof).

You also need a larger library of darks for the different gain/offset settings and in the case of QHY, 3 different main types of readout modes.So that is a lot of darks and biases.

Its a bit wild imaging at 3.76 micron pixel level. It shows up most little defects you may normally "get away with". It seems to be at its worst at short focal lengths.

I haven't seen any reflections from mine but I use Gen 2 Astrodons and have for years They are expensive but its a one off cost and it gets used over many years with no problems with all my cameras interchangeably.

I use a FLI filter wheel and it stays on the scope and different cameras can be attached to it.

Are you seeing subtle dark horizontal lines/banding that is random? I haven't seen it a lot but it does seem to only appear in heavily underexposed subs.
I haven't seen walking noise yet either. Again I think its a under exposure symptom.

Otherwise the QHY600m handles much the same as my other CCDs and I use it the same way. Perhaps sometimes shorter 5 minute exposures on bright core objects rather than my standard 10 minute exposures.

AUD$3300 is a lot but what Astro CCD camera can you get for that new? They generally start at about $5,000 at least for a new one.

Greg.
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Old 20-05-2021, 05:18 PM
Startrek (Martin)
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Clive,
Excellent review , very comprehensive and well presented
I donít have the QHY268C but I have itís competitor the ZWOASI2600MC
Very similar performance and results
Iíve gone from using a Canon 600D wit QE 38% for nearly 4 years to the 2600MC in August 2020 with QE at 80% ( quantum leap in performance )
I take darks every session ( but hardly use them ) and do not need to remove the camera, just pop the lid on ( 8Ē newt )
When I process with and without darks no matter what objects , integration time , cooling temperature etc... I canít see any discernible difference in my images as this camera is so damn good , extremely low noise , negligible dark current etc.....
I purchased my 2600MC for $3,400 in August last year and now they have come down to $3,200.
Thanks for posting
Cheers
Martin
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Old 20-05-2021, 07:44 PM
Alchemy (Clive)
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Quote:
Originally Posted by gregbradley View Post

One thing I might add which is a bit of an issue with CMOS. None of them have shutters. That means taking darks mean you have to remove the camera (which is extremely sensitive to tilt) and then take darks in a dark location with some sort of cap (the supplied cap is not lightproof).

You also need a larger library of darks for the different gain/offset settings and in the case of QHY, 3 different main types of readout modes.So that is a lot of darks and biases.


I haven't seen any reflections from mine but I use Gen 2 Astrodons and have for years They are expensive but its a one off cost and it gets used over many years with no problems with all my cameras interchangeably.


Are you seeing subtle dark horizontal lines/banding that is random? I haven't seen it a lot but it does seem to only appear in heavily underexposed subs.
I haven't seen walking noise yet either. Again I think its a under exposure symptom.


Greg.
im curious as to why you need to remove the camera for darks, i did a batch after the short picture provided, just closed up the obs put cap on the scope and went to bed while it ran through the night. will stick to one setting for a while.

would love some high spec filters but budgetry constraints, still you get what you pay for.

noise in the camera.....
i have examined a number of dark frames and from frame to frame there seems to be a completely random pattern to the noise, however if you take a master dark and stretch it a huge amount you can get a pattern, but its not going to be a problem as i have stretched it to the extreme.
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Old 20-05-2021, 08:06 PM
Alchemy (Clive)
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Quote:
Originally Posted by Startrek View Post
Clive,
Excellent review , very comprehensive and well presented
I donít have the QHY268C but I have itís competitor the ZWOASI2600MC
Very similar performance and results
Iíve gone from using a Canon 600D wit QE 38% for nearly 4 years to the 2600MC in August 2020 with QE at 80% ( quantum leap in performance )
I take darks every session ( but hardly use them ) and do not need to remove the camera, just pop the lid on ( 8Ē newt )
When I process with and without darks no matter what objects , integration time , cooling temperature etc... I canít see any discernible difference in my images as this camera is so damn good , extremely low noise , negligible dark current etc.....
I purchased my 2600MC for $3,400 in August last year and now they have come down to $3,200.
Thanks for posting
Cheers
Martin
it would appear these cameras are very clean, i had a modded 300d canon way back, then got a qhy8 then a 9, the 8 was a color chip which was very clean, the 9 less so. i havent really had a chance to gather much with this camera, but it looks very promising, and its fun just to go out and get something to process every time you use it. the upgrade was going to be the mono camera until i went out one night and couldnt get motivated enough to shoot rgb on aforementioned galaxy, so decided on the color.

its expect that both the zwo and the qhy perform similarly, the holden and ford of the camera world, it comes down to the skill of the driver, gregs just got the bathurst model.

i wasnt going to buy a cmos until the amp glow was resolved, bit like going back to my 300d.

3k plus is a bit of money, but this is my 4th camera in approx 18 years, so 6 years for a camera, thats about $1.50 a day, or a lot less than a cup of coffee.
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Old 20-05-2021, 09:37 PM
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Quote:
Originally Posted by Alchemy View Post
im curious as to why you need to remove the camera for darks, i did a batch after the short picture provided, just closed up the obs put cap on the scope and went to bed while it ran through the night. will stick to one setting for a while.

would love some high spec filters but budgetry constraints, still you get what you pay for.

noise in the camera.....
i have examined a number of dark frames and from frame to frame there seems to be a completely random pattern to the noise, however if you take a master dark and stretch it a huge amount you can get a pattern, but its not going to be a problem as i have stretched it to the extreme.

Good point. I'll try simply putting the OTA lens cap on and take darks on a cloudy night. Thanks for the tip.

Greg.
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Old 20-05-2021, 11:48 PM
Startrek (Martin)
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Originally Posted by gregbradley View Post
Good point. I'll try simply putting the OTA lens cap on and take darks on a cloudy night. Thanks for the tip.

Greg.
Greg,
Before I had my NexDome and I was imaging outside ,Iíd just fit the lid on my newt and grab an old black billabong rash shirt and slip it over the end to ensure no stray light snuck between the gaps , does the job
When I image in Sydney my yard is like daylight on some nights so I just use the black rash shirt as well and my darks are usually pretty good
Itís to much time waisting warming cameras and removing , re installing , cooling again etc... every minute outside is precious so I try to minimise time on every facet of AP
Cheers
Martin
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Old 21-05-2021, 07:29 AM
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Quote:
Originally Posted by Alchemy View Post
im curious as to why you need to remove the camera for darks, i did a batch after the short picture provided, just closed up the obs put cap on the scope and went to bed while it ran through the night. will stick to one setting for a while.

would love some high spec filters but budgetry constraints, still you get what you pay for.

noise in the camera.....
i have examined a number of dark frames and from frame to frame there seems to be a completely random pattern to the noise, however if you take a master dark and stretch it a huge amount you can get a pattern, but its not going to be a problem as i have stretched it to the extreme.

Thanks Martin.

Greg.
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Old 22-05-2021, 01:51 PM
Alchemy (Clive)
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Updating performance with Ha Filter

having to rewrite this as my stacking was botched.... of note turn off deepskystacker color calibration .... it gives terrible results

pic 1
5 min sub Ha filter prawn

pic 2
5 min sub M83 Ha..... note that neither deepskystacker or pixinsight could stack these

pic 3 13 frames 5 min subs.

these taken 0 gain 30 offset

will try again with 60 gain to give similar well depth to my qhy9......now done per edit

pic 4
gain 60 offset 30 high gain mode .... Hydrogen in M83
now we have a workable stackable image , 5 min subs.
with processing this could be integrated into an RGB image
RECOMENDATION use this higher setting for narrowband work.

pic 5
Ha added to M83 plus a bit of processing to bring up detail


i think we are done here.
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Last edited by Alchemy; 23-05-2021 at 09:24 PM. Reason: more data again
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