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Optimal Sub-Exposure Calculator help

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Hi Peter, regarding your question about bandwidth, it seems you are right. You can look on this nice article: aiastro.wordpress.com/2021/07/02/optimum...exposure-calculator/
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10 months 2 weeks ago #93258

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Thank you Joseph for your instruction how to create custom camera profile. I have created one for my SV605MC and it works perfectly.
10 months 2 weeks ago #93269

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Thank you for those instructions! I really do believe that it would be great for the user to have the ability to import or create his own camera profile.

Totally agree with you above. As a SharpCap subscriber for years, I can easily say that every camera is unique, even if they have the same sensor if they belong to the same brand. So if you are looking for the best possible approach, you need to run the sensor analysis on your own.
Last edit: 10 months 2 weeks ago by Euripides.
10 months 2 weeks ago #93286

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Yes, during development of the exposure calculator there was a suggestion that we create a tool to determine camera read-noise. I have attempted to create such a tool, (not as intensive or sophisticated as Dr Glover's tool). But so far my process is not producing results which correspond to manufacturer data for the camera. So I'm either missing something in the read-noise computation process, or the data I'm gathering from the camera (flats and bias images) is faulty.

If anyone has managed to calculate read-noise from a camera, please let me know.
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10 months 2 weeks ago #93292

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With regard to values for filter bandwidth, I was working on the documentation but I could use some feedback on this. I have no formal engineering education, so this a a request for comments.

I think that for narrow-band filters, using the the documented bandwidth (typically 3 to 5 nm) is fine.

But for broad band filters I think some assessment is required. I've attached a png image with mark-ups on the Red and Blue channels of a graph for a set of LRGB filters from Astronomik.

1) Notice that the transmission curves of the filters are quite broad at the base, and narrower at the top. But the base represents no transmission, so it would NOT make sense to use the values like 137 for Blue, or 141 for Red in the calculator. I believe that the bandwidth should probably be measured at reasonably high transmission rate, for example at 80% transmission.
So a value for Blue channel is 64 and Red channel is 65.

2) This point is probably taking the analysis to an unnecessary extreme. The filters never reach 100% transmission efficiency, and the filters for each channels may vary in terms of their peak efficiency. But if you like going to extremes, it would make sense to factor in the max efficiency of a filter. So in this case, Blue bandwidth would be more like 96% of 64 nm, and Red would be more like 98% of 65 nm.

Please let me know if you have other ideas on this.

Thanks
10 months 2 weeks ago #93294
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There is probably also one more thing that needs to be considered: Quantum efficiency of the senzor. Each senzor has different quantum efficiency for particular wavelength.
For example quantum efficiency of IMX533 mono senzor:
10 months 2 weeks ago #93295

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10 months 2 weeks ago #93302

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Sorry for that stupid question: I just updated to Kstars 3.6.5. Where to find thisSub-Exposure Calculator???
10 months 2 weeks ago #93307

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Here you are
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10 months 2 weeks ago #93308
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Thanks Hades,

Just so that I understand this, if we apply the Q.E. to the color filter analysis, in an attempt to get potential balanced signal for each color channel, we would need much more exposure time on Red channel relative to Blue (or Green). So I suspect that the QE could simply be applied as a factor to the bandwidth of each filter, but we would probably only be able to use mean value from the QE graph.

For simplicity let's say that we determined from that Astronomik filter spectrum that each filter is passing 64 nm bandwidth at 80% efficiency.

The QE in the middle of the range for Blue (looks like 0.92), so the effective Blue filter bandwidth for the calculator is 64 * 0.92 = 59 nm.
The QE in the middle of the range for Green (looks like 0.86), so the effective Green filter bandwidth for the calculator is 64 * 0.86 = 55 nm.
The QE in the middle of the range for Red (looks like 0.65), so the effective Red filter bandwidth for the calculator is 64 * 0.65 = 42 nm.

So Green channel gets a slightly longer exposure that Blue channel, and Red channel gets a much longer exposure.
10 months 2 weeks ago #93313

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The filter documentation usually states bandwidht at the FWHM level
Last edit: 10 months 2 weeks ago by Vladimir.
10 months 2 weeks ago #93322

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Hi i try to create a new camera following your description.
but it's possible to copy the new file on the original folder.
it seems than i don't have the authorization for that.
how can i do ( i'm using ekos kstars on a raspberry PI4 with stellarmate)
regards
Last edit: 9 months 3 weeks ago by vera .
9 months 3 weeks ago #93748

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