How do I find the factory set offset in ZWO cameras

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Menno555
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Re: How do I find the factory set offset in ZWO cameras

#11

Post by Menno555 »

https://astronomy-imaging-camera.com/software-drivers under the Developers tab. But these are really files for developers, it has to be decompiled and so on. Information is contained in DLL files as far as know, so no readable text.
But all in all the offset/brightness setting is not such a big deal. Well, it is :) but you can set it to your liking/needs yourself. When I had my 294MC camera, I always was on the low side with offset, between 5 and 20.

Menno
GaryS
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Re: How do I find the factory set offset in ZWO cameras

#12

Post by GaryS »

Thanks again Menno. For me this all relates to an unrelenting quest to get decent functional Flats. I think the preset offset is central a getting flats to work correctly. For EAA observing, it’s not so important but for variable imaging and analysis, it has to be a good as possible.
Cheers
Gary
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Menno555
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Re: How do I find the factory set offset in ZWO cameras

#13

Post by Menno555 »

There is no connection between the default offset and flats
For example: I capture with 90 seconds, Gain 120 and Offset/Brightness 15. For my darks I use the same settings and for my flats and darkflats I only adjust the exposure time. And I will have normal functioning (dark)flats then.

Menno
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turfpit
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Re: How do I find the factory set offset in ZWO cameras

#14

Post by turfpit »

Gary

See page 10 of viewtopic.php?f=35&t=2552. Note that black_level for Altair is brightness for ZWO (and offset for QHY). I am basically using the histogram to decide what offset to use for a given gain. If I change the gain then I repeat the process for establishing the offset. I would only be using a couple of gain settings so once these are learnt - job done.

Once offset (for a given gain) has been established I proceed as follows
  • capture lights using gain and established offset
  • capture darks using same settings as lights (exposure, gain, offset)
  • capture bias using minimum exposure (and same gain & offset as above)
  • capture flats by keeping gain and offset as above but adjusting exposure downwards until I have approximately 50% histogram
Note that all the above was achieved using the histogram - that makes the processes repeatable. See the histograms below.

A decent flat frame (for me) gives a mean value of ~30,000 when viewed in FITS Liberator.

For flat frames I use a home made light panel built for about £20.

As for the default offset for the ZWO camera, Robin is best placed to answer that.

Dave

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