Offset--do I need one?

[Rodd]

What a tale to tell.  Just spent the entire day (the final day, mind you.  I have been at this for weeks) with a diffraction Limited expert trying to get the zwo asi 1600 to work with new laptop--(new uploads of every software and drivers).  This had everyone stumped.  tried older versions of maxim, ASCOM, ZWO drivers, tried camera in Nebulosity and ASI studios.  Finally, what it came down to, was the first time the new ASI zwo camera control driver is used it comes with blank boxes (accessed through the edit control!) for gain and offset values.  Not until values were manually input, did the driver give me control of the gain and offset.  So my questions

 

1) what is offset; and

2) Do I need to use an offset.  

Now that I can use the camera I may have to manually input the offset and gain.  I won't know until I use it.  Gain is easy.  I know that the default offset for this camera was set at 50 by ZWO--but I am not sure if 50 was the offset for all gains, or just unity, and that may have been the old driver, anyway.  When gain changes, does offset change as well, necessarily?  If this is true, and I have to manually set offset, do I need one?  What would be wrong with an offset of 0 or 1.  I could also use 50?  I know trial and error will be necessary, but I would like a general understanding so I don't lose too many precious nights fiddling with it.

Glad to be back up--though not verified yet, but at least the camera is responding correctly on the bench.  But as you all know, there are a million things that could go wrong, and then some, that could manifest

Anybody know much about offsets?  To be clear, this is for the ASI 1600 mm cool pro.  The version that came out after they switched from man ual gain/offset to preset (or manual) gains but with preset offset of 50.  It seems the new driver goes back to a non preset offset.

Thanks,

Rodd

[Budgie1]

As I understand it (and this may be corrected by others with more knowledge ) the offset setting is there to make sure that no clipping occurs to the black part of your image. 

When offset is at 0 the peak will be hard up against the left hand edge of the histogram, this may lead to some of the black point being lost or not recorded. Increasing the offset will move the peak to the right on the histogram and you're looking for a gap between the left hand end of the histogram and left hand side of the base of the peak.

I found this article which explains it in more detail: https://daleghent.com/2020/08/understanding-camera-offset

[Rodd]

2 hours ago, Budgie1 said:

As I understand it (and this may be corrected by others with more knowledge ) the offset setting is there to make sure that no clipping occurs to the black part of your image. 

When offset is at 0 the peak will be hard up against the left hand edge of the histogram, this may lead to some of the black point being lost or not recorded. Increasing the offset will move the peak to the right on the histogram and you're looking for a gap between the left hand end of the histogram and left hand side of the base of the peak.

I found this article which explains it in more detail: https://daleghent.com/2020/08/understanding-camera-offset

Ahh…. I see. Makes sense.   I guess the old default of 50 is reasonable. Thanks