M13 from Wymswold - advice needed

[Johnnyaardvark]

Hi all

 

Posting these before they are finished really as I am having problems with fuzziness around stars. Some have a black ring around them too. The final version is a stacked image of about 17x 25 second subs. No darks or flats. The stars  on not perfectly round on the original.

 

I have posted here: an original; a cropped original; a cropped darkened version of one of the unstacked originals (these are to show the shape of the stars and lack of fuzziness around them ) and a crop of the stacked version. Stacked in DSS.  

 

Looking for advice on how to get rid of some of the issues and the over bright central region in the final stacked image.

 

Thanks,

 

Steve

 

No stacked no crop no editing

M13 Globular Cluster Hercules - no editing by sja88, on Flickr

 

No Stacking, one 25 second image, cropped

M13 Org jpg crop by sja88, on Flickr

 

No Stacking, one 25 second image, some image processing and cropped

M13 orig jpg edit crop copy by sja88, on Flickr

 

 

17 (best of 22) images stackked in DSS. Nice as it shows a galaxy (I think to the side too but problem with bloating/fuzz around stars? Need further editing but delaying on this until I find out more about working around the problems it has... if I can?!

M13 Orig Stack 2 cropped by sja88, on Flickr

 

 

Comments, suggestions, advice... most welcome,

 

Thanks

 

Steve

[Perkil8r]

Looks like the data is fine, possibly some work on focus reqd but not half bad as focus goes. A lot of those issues will be processed out.

[+RonC]

Check your DSS settings, Graham had a problem with 'polo' like stars and changed the settings in DSS 

[Perkil8r]

Usually something to do with the auto remove hot pixels as I recall from my first attempts. It thinks stars are hot pixels

[Doc]

Nice one Steve.

 

Like the last one and you have caught Ngc6207 as well.

[xanthic]

Hi Steve. Can you list your DSS settings? The sub look ok, I hope you don't mind but I had a quick go at processing that top pic. You need to constrain the curve when processing targets like this. Add plenty of points in and tweak them until it looks better. Don't try to push the image too far with one iteration. It's better to improve it a little, apply it and then tweak curves again. I gave this one an unsharp mask, curves, dropped the red a bit to remove some of the noise. If you can do the same on the stacked version, I reckon you'll have a good image.

 

[Johnnyaardvark]

Thanks everyone.

 

Trying again with a lower threshold than I had been using (but don't think that will change anything) and have removed hot pixel removal/detection just in case (hmmmn Mike ) but not had problems with that before. From my subs I don't think the focus is much of an issue but the very slightly elongated stars could be.

 

As for settings I am pretty much using the default. Had upped the star detection threshold as I'd hoped with them bing full DSLR images it may reduce the processing required. Was still finding around 200 stars and have tried two settings, returned it now to 10 to have a go. Also did have a go with Kappa sigma clipping on the stacking "light" tab which I think was kind of the change that Graham made re: his polomint stars... again the stacked image was pretty much the same.

 

Will see if there are any changes this time and will have a go at editing with the stacked image with your comments in mind Leigh. Thanks and you are welcome re: editing that image. Looks nice

 

Steve

[Astrocookie]

Hi Steve.

 

RE: bright core.

 

I took 12 subs at 300s for the outer stars and 12 subs at 90s for the core then layered them in PS with a mask around the centre to only allow the shorter exposure to show through.

 

I can send you a pdf of the procedure (it was in an old S@N) if you fancy a go.

 

I imagine you have a bigger scope than me as you are catching a lot of light for a short exposure compared to mine.

[Johnnyaardvark]

Hi Steve.

 

RE: bright core.

 

I took 12 subs at 300s for the outer stars and 12 subs at 90s for the core then layered them in PS with a mask around the centre to only allow the shorter exposure to show through.

 

I can send you a pdf of the procedure (it was in an old S@N) if you fancy a go.

 

I imagine you have a bigger scope than me as you are catching a lot of light for a short exposure compared to mine.

 

Thanks that would be good. Just done something similar but with the data I have... adjusting the curves on a feathered selection of the core and something similar on NGC6207 (Thanks @Doc )

 

About to post that image in another thread.

 

As for the scope I'm using a borrowed ED80 my subs are as short as they are mostly due to tracking limitations. Improved polar alignment last night no end but the seemed to struggle with particularly long subs anyway. All a good learning experience.

 

Steve