QHY268C: Multiple resolutions

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cschatz
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QHY268C: Multiple resolutions

#1

Post by cschatz »

Hi there all this is my first post here. I had initially purchased SharpCap just for the polar alignment (which is working super well for me)
but recently transitioned from DSLR to the QHY268C hence now using SharpCap for imaging as well... Having come from Backyard EOS
there are a few interface suggestions I have but I'll put that on the feature request part. Overall I think SC is a remarkable piece of software
and am happy to be part of this community.

My immediate question though was last weekend's imaging session I seemed to get 2 different resolutions without (knowingly at least) changing them....

The 2 resolutions are:
6252 x 4176
6280 x 4210

My first thought was that it was the difference between raws acquired through Live Stack and those just captured by Snapshot or Quick Capture.
But I saw within those lists fluctuations of those 2 resolutions also...

This isn't the end of the world and I'm not upset losing 30 or so pixels, but DSS is barking that the res is different hence can't stack/register.
If I change canvas size in Gimp the debayering messes up which is not surprising as I'm guessing the debayering is very sensitive to the row/index alignment hence you can't crop at will....Trying to debayer and save as an RGB file like TIF has had spotty results in PIPP but could be user error..

I was using the most recent download of Sharpcap 4, camera is QHY268C,RAW16 and FITS format, I put USB traffic to 10 (still not totally sure what that is) and gain was around 60.....

Anyhow just putting this out there as possibly a bug or if I goofed on something happy to be pointed in the right direction. Otherwise
if anyone has a battle tested system for cropping a FITS file or debayer conversions would love to hear it...

Cheers!
Casey
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Re: QHY268C: Multiple resolutions

#2

Post by admin »

Hi Casey,

I think that you are seeing the difference between the available resolutions for the QHY camera depending on whether it is run in video mode or still camera mode.

You can end up in still mode either by turning off 'Live View' in SharpCap so that it acts as a still camera or selecting the 'Force Still Mode' option, which means SharpCap runs the camera in still mode internally but captures a continuous stream of images like a video camera does.

Most camera brands hide this difference in behaviour from the end user (and the software developer) in their SDK, but QHY tend to focus on making all the functionality of the camera available, including those few extra pixels in each direction in video mode.

Probably the best thing here is to enable the 'force still mode' option and save a default capture profile that will turn it on each time you open the camera - this will ensure that you get the same resolution regardless of whether you have SharpCap in live video or still camera mode. The only thing this will not work for is if you want to do high speed imaging (lunar/solar/planetary) with the camera - in that case you will need to turn still mode off, but then you will not be worrying about darks/flats :)

cheers,

Robin
cschatz
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Joined: Mon Aug 02, 2021 9:07 am

Re: QHY268C: Multiple resolutions

#3

Post by cschatz »

Hi there Robin thanks for the response!

I got back to imaging a couple nights ago and was pleasantly surprised to see a
"There's a new version..." splash screen upon loading SC. I might be crazy but
I didn't see "Force Still Mode" anymore in this new version?

Either way I seemed to be getting the full resolution consistently throughout the night
so perhaps you fixed something internal and removed the need for the force
option....
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Re: QHY268C: Multiple resolutions

#4

Post by admin »

Hi,

the force still mode option will hide itself if you have the camera in RGB rather than RAW - RGB does not support still mode, so showing the control in RGB is pointless. Could that have been the reason you did not see it?

cheers,

Robin
cschatz
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Re: QHY268C: Multiple resolutions

#5

Post by cschatz »

I did all my test shots at Raw16 but once I was happy with framing and focus
I began Live Stack. Now I'm nervous that Live Stack forced a different mode?
Here's a screen grab of my session last night but unfortunately the color space
menu is just off screen
manakau_rho_WIP.PNG
manakau_rho_WIP.PNG (794.64 KiB) Viewed 2158 times
Also here's the camera settings file from the last Quick Capture
before I started Live Stack....It shows I was in Raw16:

[QHY268C]
FrameType=Light
Debayer Preview=On
Output Format=FITS files (*.fits)
Binning=1x1
Capture Area=6252x4176
Colour Space=RAW16
Pan=0
Tilt=0
Read Mode=PhotoGraphic DSO
Enable Live Broadcast=Off
Use DDR Buffer=On
USB Traffic=9
Offset=0
Frame Rate Limit=Maximum
Gain=70
Exposure=180.000s
Calibration End Pos Adjust=5730
Calibration Start Pos Adjust=16360
GPS Calibration LED=Off
GPS Freq Stabilization=Off
GPS=Off
Timestamp Frames=Off
White Bal (B)=10
White Bal (G)=10
White Bal (R)=10
Contrast=0
Brightness=0
Gamma=1
Temperature=-24.9
Target Temperature=-25
Cooler Power=236(Auto)
Background Subtraction=Off
Planet/Disk Stabilization=Off
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=None
Display Black Point=0.037593984962406
Display MidTone Point=0.321301373735089
Display White Point=1
Notes=
TimeStamp=2021-08-11T08:59:12.1989513Z
SharpCapVersion=4.0.8026.0
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Re: QHY268C: Multiple resolutions

#6

Post by admin »

Hi,

no, that all looks like it was in RAW16 (and I can see the force still mode control in your screenshot too).

Nice image by the way!

Robin
cschatz
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Re: QHY268C: Multiple resolutions

#7

Post by cschatz »

Thanks ! The Rho Ophiuchus is really amazing and here in New Zealand it's at zenith as opposed to
Los Angeles where I'm from in which it only gets 30ish degrees above the horizon....

I'm embarrassed now yes the "Force Still Mode" is clearly there! I guess in the excitement of getting
what I could before the clouds rolled in I didn't see it :-) The was another post about a poor fella being in
'Panic Mode' or something because using that feature had caused some issues. It seems that it was
ultimately resolved and not SC's fault, but I think it still made me apprehensive about using that mode.

Indeed I am still getting a seemingly arbitrary mix in which occasionally that slightly lower res creeps in.
Likely I will make a workflow in which I debayer all images to TIF, than make a Photoshop action that
checks the canvas size and fix it. This should be enough to trick Deep Sky Stacker into proceeding..

Coming from DSLR I'm finding the FIT format annoying to use. Is there something magic about that format
that I'm missing? I'm perhaps spoiled by the niceties of Lightroom as a way of organizing and pruning
out the bad shots...
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Re: QHY268C: Multiple resolutions

#8

Post by admin »

Hi,

FIT format has the advantage of header data being standardized for astro use (co-ordinates, filter, etc) and also the bulk of astro processing applications handling it nicely. That probably makes it the standard.

PNG can happily support 16 bit data, but a lot of applications quietly drop 16 bit files to 8 bit when opening them, so you have to be careful there.

TIFF again can support 16 bit, but there is a whole minefield around compression in TIFF files as a lot of applications don't support compressed files.

cheers,

Robin
cschatz
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Re: QHY268C: Multiple resolutions

#9

Post by cschatz »

Hi there Robin sorry to dig up an old questionbut Antares is setting and it's time to start processing
all these!

The other day I wanted shoot dark frames to correlate with the 6280 x 4210 images captured
during the live stacking session...To my surprise that resolution isn't even on the menu!

There have been a few releases since that shoot, so that 6280 x 4210 may have been a burp
in the live stacking saving, all of which is fine, but the question now if I trim the canvas
size to match all the other 6252x4176 shots, is it about the center of the image? Or anchored
to a corner?

Obviously calibration frames have to be pixel to pixel overlaid perfectly. I don't know how to compare a
light and a dark/light frame....Ideally I'd shoot a chart with both res but that 6280 isn't even on there anymore....

Any thoughts appreciated as I have lights darks biases and flats all with slightly different resolutions...

Cheers,
Casey
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Re: QHY268C: Multiple resolutions

#10

Post by admin »

Hi Casey,

as far as I know, the 6280x4210 resolution should be available if you put the camera into live view (video) mode (select live view in the toolbar, turn off 'force still mode' if you had it switched on).

I honestly wish that the QHY SDK gave a consistent image size between video and still mode as it would avoid all this trouble. QHY like to give flexibility to developers to get the most out of the camera, but the simplified approach of other manufacturers is easier on the software developer and the end user!

I don't have information about how the two resolutions relate to each other in terms of offset/crop requirements to get from one to the other - I suspect that this information varies from model to model. It is possible to work this out though:

* Take dark frame images at the same settings in both live and still mode
* look for an obvious hot/warm pixel (or pattern of hot/warm pixels) near the top-left corner of the image
* Compare the X,Y co-ordinates of the hot pixel(s) between the live and still images to work out the offset between the top-left of the live frame and the top-left of the still frame

Using this info you can work out the correct crop to apply to make the images line up in a pixel-perfect way. I'd still recommend either working entirely in live mode or entirely in still mode to avoid the need to do this though.

thanks,

Robin
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