OSC QHY8L - very orange images

[Obi Wan Ken00bi]

Hi SGL!

I've just received my brand new QHY8L camera but the images, after debayering using GBRG, are coming out rather orange. The moon was very white when I shot this.

Arcturus same! (ok that IS a red giant, but all the other stars are also rather orange).

Am I doing something wrong here?

 

edit: topic name

[JohnSadlerAstro]

Hi,

I have had trouble with DSS displaying horrible looking colours, have you tried "stacking" the one picture then exporting as a tif or similar? You can then try aligning the histogram in another processing software. Although, for that matter you can do that in DSS, I believe. 

That  will hopefully sort the issue out.

John

[Obi Wan Ken00bi]

10 minutes ago, JohnSadlerAstro said:

Hi,

I have had trouble with DSS displaying horrible looking colours, have you tried "stacking" the one picture then exporting as a tif or similar? You can then try aligning the histogram in another processing software. Although, for that matter you can do that in DSS, I believe. 

 That  will hopefully sort the issue out.

John

Hi John!

Thanks for your reply. Yes I have tried that. Photoshop just shows the same yellow-ish color after 'stacking' one image and saving as a TIFF. Also EZcap which ships with the QHY8L shows the yellow/orange color when saved to JPG....

[steppenwolf]

Can you post up a single FITS file for us to examine, please - not a screen shot but an actual data file.

[Obi Wan Ken00bi]

1 hour ago, steppenwolf said:

Can you post up a single FITS file for us to examine, please - not a screen shot but an actual data file.

Here you go! Thanks for helping out

moon5ms.fit

moon10ms.fit

moon14ms.fit

and Arcturus and some surrounding stars:

Testqhy8I.fit

[Stub Mandrel]

Does the camera have a built in IR filter?

[steppenwolf]

OK, thank you for uploading them. I can't get an accurate colour rendition straight from the de-Bayering  - I can match your yellow colouring or swing it to blue but I think this is simply an over-red exposure. Are you using an IR filter?

 

[steppenwolf]

Ooopps doubled with Neil!

[Thalestris24]

It's probably to do with the qhy8l being sensitive in the red end of the spectrum (good for h-alpha!). I think you probably just have to do a histogram alignment and maybe adjustment in curves to get a whiter moon. Also, the qhy8l needs a minimum exposure time of something like 2.5s (from memory - check in the user guide) so you'd need a filter to reduce the brightness of the Moon (neutral density filter?) rather than trying to do very short exposures.

Louise

 

[Obi Wan Ken00bi]

Hi all,

Thanks for digging into this. The camera does have a build in IR filter I believe (see image). Over exposure on the red and green pixels seems to make sense (cam has two green pixels after all). I didn't buy this camera to make images of the moon offcourse. I'll try some DSO's as soon as it get dark again. Right now in Denmark it only gets 'dark' between 01:00 and 03:00, and not really dark dark, the sun glow is still here. Not enough contrast for DSO I think. You guys know of any objects that I could still try with long exposures to try out the camera?

 

Btw Steve, You have returned now officially the favor of me buying your book and promoting it amoung my friends, hihi. Thanks!

 

[Stub Mandrel]

32 minutes ago, Obi Wan Ken00bi said:

(cam has two green pixels after all)

Nearly all colour cameras have this and it is allowed for by the debayer algorithms. More likely Louise is correct and although it has an IR filter it still has increased red sensitivity (like a modded DSLR).

M27 is a good test target, it is bright and has easily captured blue/cyan coloured emissions but also red areas at eth edges easily captured by a Ha sensitive camera.

[Obi Wan Ken00bi]

Makes sense indeed. I will target the dumbell asap (it’s on my list anyway). I’ll report back in a month or so when it gets dark enough during the night  

 

keep you posted!

[Thalestris24]

Here is spectral response curve of the qhy8l sensor. The IR glass window will likely have some effect on the far red.

Louise

[Obi Wan Ken00bi]

Thanks Louise,

Based on your chart +post and info by  Neil and Peter, I changed the curves to increase blue spectrum and decreased red, so this should be more accurate image of the moon

I'll keep you all posted of my first DSO, cant wait!

[saac]

Very informative post -  excellent example of what SGL does well.  

Jim 

[Obi Wan Ken00bi]

So, storm in a teacup! Below normal images with the QHY8L. (Under light polluted sky so with CLS filter, no coma corrector which arrived only today and not in full darkness due to summer time in northern Denmark). Colors are not orange