Does using variable Offset simply buy a few more ADU headroom?

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Stonius
Posts: 11
Joined: Wed May 30, 2018 11:36 am

Does using variable Offset simply buy a few more ADU headroom?

Post by Stonius » Wed Jan 09, 2019 3:44 am

Late to the party here, but as far as I can gather, if you choose to use variable offset, the end result is simply that you get at most 40 ADU extra headroom in the highlights.

I figure this on the published offset of 10 to be used at 0 gain. Now they're just saying 'keep it at 50' you could claw back another 40ADU, but this doesn't affect the noisy end of the image, only the highlights.

And let's face it, 40ADU isn't going to make much difference to an image.

Is this correct?

Markus

Stonius
Posts: 11
Joined: Wed May 30, 2018 11:36 am

Re: Does using variable Offset simply buy a few more ADU headroom?

Post by Stonius » Thu Jan 10, 2019 12:49 pm

Sorry, should have mentioned that this refers to the ASI1600 MM Pro.

I should also add, that my own experiments would imply that you can get away with much lower Offsets while still not clipping the read noise.

It's only really once you get into gains of 250+ that you need to be looking at using offsets over 30 ADU.

As I said in my first post (talking to myself here - sheesh!) I think that even if claw back even 40 ADU (best case) - I imagine that it will be only evident in the way the brightest stars are clipped.

Can anyone else confirm my thinking is correct?
Gain Vs Offset.JPG

Katherine.Tsai
Posts: 3
Joined: Fri Dec 07, 2018 10:24 am

Re: Does using variable Offset simply buy a few more ADU headroom?

Post by Katherine.Tsai » Mon Jan 14, 2019 10:33 am

Hi Markus,
Yes, you are right.

You could also change the gain and offset in the settings If you are using ASICAP.

Stonius
Posts: 11
Joined: Wed May 30, 2018 11:36 am

Re: Does using variable Offset simply buy a few more ADU headroom?

Post by Stonius » Wed Jan 16, 2019 8:56 am

Many Thanks :-)

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