Unity gain

Discussion of using SharpCap for Deep Sky Imaging
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Darkside
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Unity gain

Post by Darkside »

I've just run the smart histogram and it's giving me setting up of 895 using a dual narrowband filter, normally the gain for my Hypercam is just under 400, is this normal as I assumed unity gain didn't change, or has something gone wrong? I'm still getting 900 MDR which is what it normally is. TIA
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Re: Unity gain

Post by admin »

Hi,

basically what has happened is that the sky brightness is lower with the filter, so you need to take longer subs - so long that optimum settings can't be found in your normal exposure range (you have a min/max exposure you can choose - say 5s to 5min - in the brain window).

When this happens, SharpCap will pick a higher gain than usual to compensate. Note that the gain option is 'aim for unity gain' not 'use unity gain' - that means that SharpCap tries to get as close to unity gain as possible given the other constraints.

cheers,

Robin
Darkside
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Joined: Fri Apr 17, 2020 11:50 am

Re: Unity gain

Post by Darkside »

Thanks very much for your prompt reply.
Darkside
Posts: 13
Joined: Fri Apr 17, 2020 11:50 am

Re: Unity gain

Post by Darkside »

I think something went wrong when I measured the sky as I got a gain of 895 and exposure of 502s, this was aiming for unity gain and seems much higher/longer than what I was expecting.
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Re: Unity gain

Post by admin »

Hi,

did you happen to note down the sky background measurement value? Would that value it's possible to re-run the calculation and see if the results makes sense in terms of the measured value. If that value was unusually low then a longer exposure and higher gain would be recommended.

Cheers, Robin
Darkside
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Re: Unity gain

Post by Darkside »

I didn't unfortunately, if I get results I'm not expecting I shall make a note next time. I was wondering if the sensor data that is pre-installed on Sharpcap is kept if a sensor analysis is run or does the new sensor analysis overwrite the data that came pre-installed.
If it does overwrite it can the original data that came with the download be reinstalled somehow?
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Re: Unity gain

Post by admin »

Hi,

the data that is pre-installed was SharpCap is never deleted, but if you do your own sensor analysis then a separate file is created with those results in it. SharpCap will use the data from your own analysis in preference to the pre-installed data. To go back to using the pre-installed data, find and delete the file containing your own measurements which will be in the folder

Code: Select all

C:\Users\<your user name>\AppData\Roaming\SharpCap\SensorCharacteristics
Once you've done that, restart SharpCap and you will you back on the default data.

Cheers, Robin
Darkside
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Joined: Fri Apr 17, 2020 11:50 am

Re: Unity gain

Post by Darkside »

Thank you very much.
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