M51 - Luminance

[cjdawson]

Last night I captured 60 frames of Luminance on M51 (caught the red as well, but didn't get the G or B, as it clouded over)

I tried processing with Astro pixel processor, using Darks, Flats, DarkFlats, Bias and of course the lights.

Here's my result.

I've got all the data it is several GB in size (as you'd expect) however, looking at this, I don't think that the flats are working properly as there's still some vignetting in the image - I'd have expected that to have been corrected out.

That said, I don't see any dust bunnies, so maybe I'm wrong.

The image was taken from my front garden under bortle 8 a sky.

The exposures are 58*60" at unity gain with offset 52.

 

I did notice when I was taking the dark flats that there were some minimum values of 16 from in the image stats.  I've never seen it lower than that, so I'm wondering if this is the root of the problem and I should bump the offset some more?

Are there any other suggestions that would help to improve things?

btw, I'm still sorting out the focusser, so I think the focusing could be improved some more.   Wanted to capture some data last night as it's hard to get a clear night where I live.

[cjdawson]

Think I figured out why the vignetting didn't get completely removed    I've been shooting with an offset of 52.   However, I did notice in the flats for darks that some of the values were 16 on the image statistics in SGPro.  This is the minium value that I've seen, so maybe there's negative clipping happening, hence no correction.

[dunc]

Hi CJDawson

This may not be directly applicable but I have an ASI294MC Pro and have struggled with issues like this for a year. I was using the default offset of 30 as set by the driver at install and unity gain. I tried increasing the offset with no positive benefit. I recently ran the Sensor Analysis and Smart Histogram in SharpCap Pro and it suggested an offset of 4 which surprised me. But low and behold I now get lovely well calibrated images with lots of signal. I was just about to sell the camera before this! 

Hope that helps

Duncan

[cjdawson]

oh wow thanks @dunc I'll take a look into that.