Blooming issue?

[graham.hobart]

Hello folks, after trying out the SBIG STT 8300 with 200 sec exp bin 1 x 1 on the Trifid with the RC 10, I noticed after stacking in MAxim that when I transferred the linear FITs to STAR Tools and even did a moderate development/stretch, the centre of the brighter stars went blue/saturated?
This ruins the picture.
Is this something I am doing wrong in the acquisition phase or in the processing phase? or is it the camera settings?
Help please
Graham.

[graham.hobart]

Something just occurred to me- is it because I am over sampling with the KAF 8300 and fl2000mm ?
That cannot be right as I can recall having an issue with a different scope and same camera, may be I should bin2x2 and try that?

[RickS]

Graham,

I've used a KAF-8300 (Starlight Xpress H-18) with the RC10 and it worked just fine binned 1x1. It's oversampled unless you're getting great seeing but not ridiculously so. It's around 0.56 arcsec/pixel, IIRC.

It won't take more than a few seconds to get the cores of bright stars to saturate under normal conditions (maybe a little longer with a narrowband filter) so I don't think that's your problem.

Maybe you could upload a single sub somewhere? I'd be happy to take a look and see if there's anything odd about it. If there isn't, which I suspect is the case, then it's a processing issue.

Cheers,
Rick.

[graham.hobart]

Ok I will do so later tonight thanks mate.

[graham.hobart]

Here is the stack exported directly from Maxim (no processing) into Star Tools with just a 52% development applied. See the bright stars with blue centres?
Graham

[RickS]

That does look pretty awful, Graham. I don't have much experience with Startools. If Ivo is around he might have some thoughts. If you can drop a copy of the Maxim stack somewhere (Dropbox?) I can tell you if that looks OK.

Cheers,
Rick.

[Amaranthus]

Test: What do they look like when you open them in Fitswork? That will tell you if it is a StarTools issue or something else.

[graham.hobart]

link.... i hope it works
https://www.dropbox.com/s/dqa52c6gvxkjt7g/Trifid%20RC%2010%20test%20SBIG.fit? dl=0
graz
if not let me knowhttps://www.dropbox.com/s/dqa52c6gvxkjt7g/Trifid%20RC%2010%20test%20SBIG.fit? dl=0

[RickS]

Got it... Here's the result of nothing more than a simple stretch in PI. Looks OK to me. i think it's probably a processing issue?

Cheers,
Rick.

[graham.hobart]

Cheers Rick that's reassuring, I will try and stack again in CCDSTAck tonight then put it through a simple photoshop attack and see what happens!

[irwjager]

Hi Graham,

I had no trouble with the latest version of StarTools (you must be using an old one?), though your data contains a lot 'NaN' entries (pixels without a value), including in the cores of the brighter stars. StarTools interpolates these (instead of making them white or leaving them as gaps), as better results will be obtained by the various algorithms if they have values to work with that lie within the range of neighbouring pixels.
Because your image contains enormous amounts of NaN pixels, interpolation may take a while during loading.

To avoid NaN/ missing values you might want to look into your stacking options - I'd also recommend leaving colour/background calibration off while you're at it, as it will have exacerbated noise before StarTools had a chance to track it. It's nice data though! (heavily oversampled however)

Hope this helps!

[graham.hobart]

Cheers Ivo- I must look at my Maxim settings as that is what I stacked it in.