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INDI Library v1.9.2 Released (14 Sep 2021)

Bimonthly Stable INDI Library release introduces new drivers and fixes for existing ones.

Excellent tutorial on minimizing noise and optimizing exposure parameters

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Hi Fenriques,

Sadly, no, don't have an Excel file with simulations. That might be useful to build.

I only have the numbers I gave in my last reply, which fit the abhorrent conditions in my backyard in a white zone and which match closely what the sharpcap site says and what the formulas in the cloudynights blog also suggest. They were obtained recently with an RC-8" at f/8 using the ASI1600MM Pro at 240 gain. The ADUs come out a little higher than in the cloudnights discussion I provided the link to, I will continue tweaking times and gain some more until my results are optimized to the conditions (that doesn't say much!).

One drawback not discussed in the video presentations or the blogs is the time factor required for downloading and dithering. The shorter the exposure times, the more those come into play. By going to shorter exposure times one will progressively end up with less integration time, since progressively more time is being wasted downloading the images and dithering. That is especially critical when using a Raspberry Pi, which is much slower than a mini-PC, or when downloading the images over WiFi. Here, it becomes essential to use a mini-PC at least, preferably the more computing power one has the better. Also, USB3 becomes absolutely critical for downloading the images. For those reasons, it seems to me to make sense not to go below 30 s exposures and rather preserve dynamic range by using a lower gain for luminance, while keeping the median ADUs in the low 2000s.

That makes the scheduler more important than ever. With that, one can then program image acquisition at different gain values, i.e. perhaps 120 gain/30s for L, 180 gain/30s for RGB and 300 gain/60s for narrowband from the city at f/8.

Jasem, if you are reading this, that would be a useful addition to the capture module: Allow different gain values to be programmed for the different filter settings (rather than only one gain value for the entire sequence), without the need to set up separate entries for the same target in the scheduler.

What do y'all think?

Best

Jo
Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set
2 years 5 months ago #36935

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hi Jo,
I'm using a color cmos so I'm not really concerned about the gain issue you mentioned.
Anyway, having a different gain setting per sequence wouldn't increase time to take calibration frames too much? that could be automated of course but storage / download time would increase.

Ferrante
2 years 5 months ago #36967

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Hi Ferrante,

Don't tell anyone (:blush: ) and don't post that fact on the internet, but I am a little lazy with my calibration frames. I am reusing my darks and flats for pretty extended periods of time and given that my area is light polluted, I have no problem with that. The noise is always much greater than the subtle difference from sensor shift over time. I have to use narrowband, one shot color is just not cutting it from the city, except for the very brightest objects like M42.
Anyway, given the dead time lost in downloads and dithering, exposure times of less than 30s seem to be counterproductive as they cut down substantially on total integration time achieved during the session. That was the main point I wanted to draw attention to.
Cheers
Jo
Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set
2 years 5 months ago #36971

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