ASI2600 Gain Preset ASCOM Driver

ASI's Range of Specialised CMOS camera's

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maudette
Posts: 43
Joined: Wed Jan 30, 2019 10:16 am

ASI2600 Gain Preset ASCOM Driver

Post by maudette » Mon May 11, 2020 1:26 am

Hi;

I need clarification.

I understand that ZWO decided to limit the range form 0 -100 on the ASCOM driver. 100 been the unity gain and where the read noise as low and regaining some DR.

BUT, when I select "unity gain" on the ascom "ASICamera Set V6.0.3.28", I get a gain of ZERO (which is no different then highest Dynamic range) under the camera setting.

When I select Lowest read noise, then it goes to 100.

What is unity gain (pleas don't tell me 1 eADU :) ). on the gragh?

I'm so confused about this, I'm thinking of returning my 2600....

bulrichl
Posts: 27
Joined: Sun May 27, 2018 9:18 am
Location: La Palma (Canary Islands)

Re: ASI2600 Gain Preset ASCOM Driver

Post by bulrichl » Mon May 11, 2020 9:56 am

Unity gain means a gain setting, which results in a conversion gain of 1 e-/ADU. As can be seen from the plot "GAIN(e-/ADU)" on the ZWO website ( https://astronomy-imaging-camera.com/pr ... -pro-color ), there is no such gain setting for this camera. Even at a gain setting of 0, the conversion gain is only about 0.76 e-/ADU. This is a property of the sensor that is used in the camera. It is due to the bit depth of the A/D converter of 16 bits and the full well capacity of 50,000 e-: (50,000 e- / 65536 ADU) = 0.76 e-/ADU.

A gain setting of 100 in the ASCOM driver corresponds to a gain setting of 100 in the plot "GAIN(e-/ADU)" on the ZWO website.

My interpretation for the confined range of gain setting in the ASCOM driver:
ZWO measured the characteristic data of the camera over a wide range (range of gain setting 0 - 450). However, for the ASCOM driver, the adjustable range was confined to 0 - 100. The reason for this decision was that actually there are only two gain settings that make sense:
1) Gain setting 0: this allows to use the full well capacity completely and expose longer and with lower risk of saturating stars respectively.
2) Gain setting 100: this allows to take advantage of low readout noise. At still higher gain, the readout noise will not decrease significantly any more, but the dynamic range drops considerably. Therefore these higher gain settings are not reasonable at all.

Bernd

Moson
Posts: 205
Joined: Wed Apr 01, 2020 8:28 am

Re: ASI2600 Gain Preset ASCOM Driver

Post by Moson » Tue May 12, 2020 5:49 am

Thank you for answering this question!
As Bernd mentioned, the gain setting from 0-100 is enough for camera, and the readout noise will not decrease significantly any more when setting higher gain, but the dynamic range drops considerably.

maudette
Posts: 43
Joined: Wed Jan 30, 2019 10:16 am

Re: ASI2600 Gain Preset ASCOM Driver

Post by maudette » Wed May 13, 2020 3:18 am

Thank you for the detailed and clear expectations. I got it and makes sense to me now. thanks again.

Moson
Posts: 205
Joined: Wed Apr 01, 2020 8:28 am

Re: ASI2600 Gain Preset ASCOM Driver

Post by Moson » Wed May 13, 2020 9:56 am

You are welcome!

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