13 minutes of the Scultpor

[ChrisM]

My excuse is that everyone has to image NGC 253 at least once!

I took 19 x 1 minute subs and for the first time, had a go at analysing the quality of each frame. I used PixInsight to get the FWHM for the same star in each frame, and as per the attached graph, there was a bit of variation over the period that I was taking pictures; from 2.6" to 3.4". I discarded all frames with a FWHM > 3.0" leaving 13 x 1 minute frames for processing, and used the best one as the reference frame. I am interested to know whether others check the FWHM on each frame via PI, and whether there is an automated way to do it.

Nikon D7000
ISO 1250
Manual focus on camera display
13 x 1 minute subs
M14 SCT unguided
FL = 3556 mm
Processed with PixInsight, size reduction in LR4

Chris

[dutch2]

Fantastic image, well done.

[Larryp]

:thumbsup:

[Bassnut]

Huge detail for 13min . Noisy natch, but bodes well. Now stop being silly and take longer subs :lol:.

[strongmanmike]

Yeah I agree with drunked Fred on this one, looks really promising indeed :thumbsup:

NO I don't check FWHM, just chuck anything obviously crap, imaging time is so precious, I am emotionally attached to every sub :sadeyes: :lol:

Mike

[ChrisM]

Thanks Ingrid. I'm still finding my way around PixInsight.


Thanks Larry - glad you liked it.


Thanks Fred. I had plans for more data last night, but reckon we were the only area with any cloud at all. The rest of Victoria had clear skies, judging by the overnight temps. I agree that the background is noisy; I might have another go at that. I will be in a position to take longer subs when I get some guiding happening. No plans for that just yet though.



I think 19 subs is the most that I have ever churned out, so tossing out one third of them wasn't easy. Maybe I should reprocess it using all the data?

Chris

[Lee]

Nice image...
I tend to put aside the obvious duds at capture, then eyeball the rest later for quality. I use Nebulosity +/- CCD Inspector to quantify sometimes....

[RickS]

Nice detail, Chris!

SubframeSelector is a really nice PI script for checking the quality of your subs. It analyses FWHM, Eccentricity, SNR, etc. and allows you to select the subs to keep and reject manually or automatically. The author has built a collection of useful tools: http://pixinsight.com/forum/index.php?topic=5712.0

Cheers,
Rick.

[Lee]

I might add - 3m FL and 1 minute unguided.... your mount is doing better than mine! I doubt I'd get round stars with my G-11 with 1 min unguided at 800mm....

[ChrisM]

Thanks Lee. With my current workflow, I don't get to see my results until I've finished shooting (usually when the clouds arrive), but this will change one day....



Thanks Rick. I am pleased with the detail too. I compared the core region with an ESO pic and couldn't see any more detail in theirs. I've had a quick look at the PI forum and that script looks to be the bee's knees. What can be done with PI never ceases to amaze me.



I've tried 2 minutes and that's too long. It would be good to get some longer exposures one day though.

Chris