SharpCap Forums

Tried the Sensor Analysis in 5/29/2018 version last night.

FYI it can get "stuck" if light is too bright. I had to manually pull the exposure slider down to get it to auto set again at one point.

Trying to use a light on the side of the house, it was always too bright or too dark, depending on what filter I used or how direct I aimed at the light. Also the warning messages in yellow at the top, I think should not be "sticky" but should automatically go away when conditions change, so as not to send the wrong message about current conditions.

Then, with an exposure of 2.7ms I got banding (light responding to 60Hz mains?) and turned out to be unusable.

Then it hit me that the moon was full, so I used that. Not perfectly uniform, but I tried to pick a small uniform area. Still not sure if/where the feedback on the size of the area you have picked is.

OK, so successful multiple runs using the moon. Too bright with LRGB, but OK with NB filters. I did get slightly different results per filter, or maybe it would be the same for three runs on the same filter? Because I didn't have perfectly uniform illumination the area I chose?

Let me know if you want the log file.

Hi,

glad to hear that you are getting on better now - some further suggestions for a suitable light source:

1) To get a more even illumination from the moon or similar external source, defocus a fair bit.
2) If you get flicker bands from artificial light then make the selection box tall and thin so it averages over several bands - it also averages over a few frames so this is usually good enough.

cheers,

Robin

Yeah I tried to use the plastic defuser I use for skyflats, but it cuts 60% so it was too dim.

Will try your suggestions.

Also, could you help me understand the difference between the results I'm getting to date and the published values here:

https://astronomy-imaging-camera.com/pr ... 600mm-cool

e.g. e/ADU and Full Well(e) values.

Thanks!

Hi,

the initial stage of the measurement (where it plots the straight line graph) to measure the e/ADU at minimum gain has come up with the wrong number (about 2-3 instead of about 5). This measurement acts as a baseline for all other measurements that are measured in electrons (all the read noise and all the e/ADU values), so if that is off then all the others are off by the same ratio.

So, the question is why... You are seeing some variability in your measurements which could well be down to the moon image you were using having brightness variations in it on small scales, so maybe worth re-trying with a better flat frame. If that doesn't help then have a play with some of the camera options to see if any of them make a difference. I've just re-tested my 1600MM-Cool and have had e/ADU for 0 gain in the 4.92 to 4.95 range consistently over several measurements.

cheers,

Robin

OK with skyflat diffuser in the evening light, much better! Went very fast as well. Right at the end it did say it was too bright but the results look great (compares well with published data).

Ah, excellent!

Thinking about it I believe that the combination of the detail in the selection area and the fact that it would be altering from frame to frame due to seeing would cause issues with the e/ADU measurement. Detail that remains absolutely fixed from frame to frame would have much less effect (probably negligble).

cheers,

Robin