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Dark frames on dual sensors Sbig camera

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Hello,

As it is my first post here, let's present myself: I am an amateur astronomer from France, doing CCD astrophotography since 2011. However I discovered Kstars/Ekos and the INDI world in January 2020 only, so thank you for this huge work and valuable tool, and sorry if my question is a bit naive.

Here is the problem. I use KStars 3.4.1 with a Mac OS 10.14.5. I connect to my Sbig ST10 with its CFW-9 filter wheel and when asked whether it has an internal shutter for dark frames I answered yes. Now, in the Guide panel, when doing a capture, Ekos starts by making a dark frame for the guide chip, however the resulting dark-subtracted image looks horrible, with 9-magnitude star (through a C9.25) barely visibles in a very noisy field. Of course the guiding was very poor. I checked that the cooling was one. I then acquire guide frames and guide with my other software (Equinox Image) and everything was fine. It looks like the dark frame subtraction was not properly done, or that the shutter was not in place. Have you an idea ?

Thanks,
Philippe
2 years 1 month ago #52309

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Anyone ?
2 years 3 weeks ago #52535

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Can you post links to FITS images for both the guide chip LIGHT and DARK frames?
Jasem Mutlaq
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2 years 3 weeks ago #52544

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Thanks,

Unfortunately, I was not wise enough to acquire those frames during my last night session, and it looks like it will not be possible for a while. However, I made the following experiment this afternoon: I connected my ST10, cooled it to -12°C, and acquired with Ekos:
- a frame of the guide chip, without subtracting a dark (case "dark" unchecked): light2s_green_nodarksub.fits
- a dark frame: dark_2s_green_guide.fits
- a frame with "dark" checked: light2s_green_darksub.fits
The files can be retrieved here: pfilliatre.free.fr/indiforum.zip
As the name implies, the exposure is 2s, with a green filter. Of course the only thing that can be seen is the ambiant light, however there is something interesting: the frames with and without dark subtraction are very similar. Indeed, if I subtract the latter with the former, the result is not similar to the dark frame, as it should be, but to random noise. It looks like the dark subtraction is not done, which could explain the very noisy aspect I observed when aiming at a mag 9 star. The dark frame by itself looks correct.
Any idea ?

Philippe
2 years 3 weeks ago #52590

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Hello,

Just a little up to this issue, for which I am still clueless. I upgraded to KStars 3.4.3.
In fact, the guider images without dark subtraction are clean enough (thanks to cooling) for a proper guiding, however it is not a satisfactory fix. Surely I have made a mistake somewhere, but where ?

Thanks,
Philippe
1 year 8 months ago #59419

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Hello,

After a one-year break with Kstars, I come back with this problem of dark frames on the guiding sensor of Sbig cameras (a ST-10 for me).

I now use the 3.5.5 version of Kstars on Mac OS X 10.14.5 (my devices are attached to a brand new Stellarmate), the problem has evolved in the sense that it seems impossible at all to take a dark frame for the guiding sensor. I mean, when I tick the "dark" box in the guide panel, and make a capture, Ekos tells me that it cannot find a suitable dark frame, and invites me to use the wizard tool in the capture panel. But in this wizard tool the menu only proposes the main sensor... Even when I change it by hand in the main capture menu to the guiding chip, darks of the main sensor are taken. By the way, in a wrong directory (/private/var/folders/fd/9fwt29xd2yjbl5r55tpvjb200000gp/T/1642232941/sequence_1 and not Library/Application Support/kstars/darks), see screen capture. 

 

Guiding without a dark frame is of course possible, but this is somewhat puzzling. Any ideas ? I also occasionally guide with a Zwo174MM, without issues (darks are well taken and subtracted).

Thank you for your ideas,
Philippe
4 months 5 days ago #79483
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Hello,

Anyone on this topic?

Thanks,
Philippe
3 months 2 weeks ago #80180

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