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pshepp1890

Altair hypercam 183c

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Hi all. 

Just got a hypercam 183c to pair with my sky watcher 10" quattro f4 Newtonian. I have the f4 apalantic coma corrector too. 

Question is what or how to I set the gain and offset? I've read a few pages but I'm lost. I'm new to dedicated astro cameras moving from my un modded dslr. 

Any help and tips would be great full with this camera. 

Cheers. 

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Apt has native support for the hypercam, so you should be able to set both gain and offset in APT.

Reading thishttps://www.cloudynights.com/topic/599475-sony-imx183-mono-test-thread-asi-qhy-etc/page-7

Gave me a lot of info.. not the hypercam, but same sensor.. Jon Rista seems to suggest that you dont go overboard with the gain on this sensor, as it has bad amp glow and a tendency toward horizontal banding.

I have the hypercam 183m and have just started using it last week. For now I am sticking to unity gain (398) for my sensor, should be around 400 for yours too. I plan on staying between 200 and 800 and varying the exposure length to get the desired signal.. the offset I have set to 200, for no particular reason.. ?

 

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Thanks so much for the reply. Il read that page on my next break. 

When it comes to offset I've heard anywhere between 100 and 1000 is safe. Is that the same with this camera? Also something about taking 2 second frames with the camera pointing at a white wall to set the max gain? 

Is this something you have heard of? 

Cheers

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4 hours ago, pshepp1890 said:

Thanks so much for the reply. Il read that page on my next break. 

When it comes to offset I've heard anywhere between 100 and 1000 is safe. Is that the same with this camera? Also something about taking 2 second frames with the camera pointing at a white wall to set the max gain? 

Is this something you have heard of? 

Cheers

No.. can't say that I have.. ?

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57 minutes ago, pshepp1890 said:

So is it the right thing to do? 

Doesn't sound terribly scientific to me, I wouldn't rely on it..

I've heard of shooting a long subbat something bright to determine the full well depth.

 

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SharpCap has a very useful sensor analysis function which determines the optimal levels

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I image with the qhy183c and use gain 11 and offset 76 with reasonable success. 

 

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As I understand it (can someone correct me if I am wrong) the optimal gain (all other things being equal) is where e/ADU (analog digital unit) is closest to 1 ("unity"); I believe this means that each analog electron will correspond to a recorded digital value of 1.  My 183c is a 12-bit sensor so each pixel can have a value between 0 and 4095 and in my case a gain value of around 430 (in the 0-5000 range) will allow a full well capacity of around 4096. This does not equate to maximum dynamic range (which comes with lower gain values), nor does it 'amplify' the signal as much as higher gains will if you need to bring out faint signal. I have found that with EAA for example I need to increase the gain significantly to bring out faint signal in short exposures.

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I believe the offset defines the signal level of black taking into account that there is always a degree of noise signal. So the optimal level of offset is just enough to lift the 'black' level above this noise. A figure of 30 has been recommended for the 183c elsewhere.

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23 minutes ago, prusling said:

As I understand it (can someone correct me if I am wrong) the optimal gain (all other things being equal) is where e/ADU (analog digital unit) is closest to 1 ("unity"); I believe this means that each analog electron will correspond to a recorded digital value of 1.  My 183c is a 12-bit sensor so each pixel can have a value between 0 and 4095 and in my case a gain value of around 430 (in the 0-5000 range) will allow a full well capacity of around 4096. This does not equate to maximum dynamic range (which comes with lower gain values), nor does it 'amplify' the signal as much as higher gains will if you need to bring out faint signal. I have found that with EAA for example I need to increase the gain significantly to bring out faint signal in short exposures.

Thanks for that, it's slowly making more sence. ? What I can do is complete the sharp cap sensor analysis tonight and put a screen shot up. Once I can "see" what is being explained, I can learn from it for the future. 

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I think you are going to find that at some point you are just going to have to try and test what works. In the end these settings will change depending on the sky brightness of your location, and the brightness of your target.

Each sensor has some characteristics that lends itself to lean in a certain direction. The imx183 seems to need slightly longer exposures than for instance the very popular asi1600 or qhy163 equivalent. This due to slightly higher read noise and smaller pixels.

Edited by jjosefsen

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To be fair that's the same as my thinking. 

I just want to get it into the right area before sitting outside in the dark trying to sort it. 

 

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On 16/10/2018 at 15:02, jjosefsen said:

Apt has native support for the hypercam, so you should be able to set both gain and offset in APT.

Reading thishttps://www.cloudynights.com/topic/599475-sony-imx183-mono-test-thread-asi-qhy-etc/page-7

Gave me a lot of info.. not the hypercam, but same sensor.. Jon Rista seems to suggest that you dont go overboard with the gain on this sensor, as it has bad amp glow and a tendency toward horizontal banding.

I have the hypercam 183m and have just started using it last week. For now I am sticking to unity gain (398) for my sensor, should be around 400 for yours too. I plan on staying between 200 and 800 and varying the exposure length to get the desired signal.. the offset I have set to 200, for no particular reason.. ?

 

A offset of 200 is too high that's using 5% of you dynamic range in offset. 50 or so might be more like it. 

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10 minutes ago, Adam J said:

A offset of 200 is too high that's using 5% of you dynamic range in offset. 50 or so might be more like it. 

I'm pretty sure I read on CN the unity gain and offset is 11 and 76 respectfully. That's why I use that and have decent results. 

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Software uses different ranges for gain values - if I remember correctly SharpCap uses 0-5000 for this camera, but other software can use a different range.  Maybe it should be expressed as a % - in my case around 8.6% for unity.

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3 hours ago, Adam J said:

A offset of 200 is too high that's using 5% of you dynamic range in offset. 50 or so might be more like it. 

Maybe.. the thing is the range of values are different from software to software. The ascom driver I use had gain from 100 to 4999, where as in apt I believe it is different. But I am still trying different settings. It's honestly a little confusing..

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8 hours ago, prusling said:

As I understand it (can someone correct me if I am wrong) the optimal gain (all other things being equal) is where e/ADU (analog digital unit) is closest to 1 ("unity"); I believe this means that each analog electron will correspond to a recorded digital value of 1.  My 183c is a 12-bit sensor so each pixel can have a value between 0 and 4095 and in my case a gain value of around 430 (in the 0-5000 range) will allow a full well capacity of around 4096. This does not equate to maximum dynamic range (which comes with lower gain values), nor does it 'amplify' the signal as much as higher gains will if you need to bring out faint signal. I have found that with EAA for example I need to increase the gain significantly to bring out faint signal in short exposures.

What gain did you set in ascom for your 183c? Its coming up as a multiplier rather than a number or percentage... 

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35 minutes ago, jjosefsen said:

Maybe.. the thing is the range of values are different from software to software. The ascom driver I use had gain from 100 to 4999, where as in apt I believe it is different. But I am still trying different settings. It's honestly a little confusing..

Yes I noticed that about the hypercam. Really odd. Can you set in one and read off the value in the other? Is it a linear relationship etc. I would ask on the apt forum. 

Edited by Adam J

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4 hours ago, geordie85 said:

I'm pretty sure I read on CN the unity gain and offset is 11 and 76 respectfully. That's why I use that and have decent results. 

Yes but in what software it seems the range is different in different applications for the hypercam. 

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So setting my offset to 45 gives me an average of 750 when taking a bias frame. 

I am having problems setting the gain though. I've got it as low as posse but everything still comes out at max exposure, even at just a 2 second sub. 

Also if I set my shutter speed below 0.1 to try and get a bias frame, the end picture is fuzzy grey, like it's been stretched. I'm using Astrophotography Tool. 

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