Sauron's Eye...

[NigeB]

Evening All,

 

I had a few good nights on M57 in the middle of the summer, but it's taken me ages to get anything remotely good out of the data. I wanted to show the outer shells, but found it was really tricky to get those to look right and still show the inner ring structure. Today I've been playing around with Pixinsight's HDRM and Deconvolution tools, with some star masks to try and protect the rest of the image. It's getting there but the detail in the central hole is not good (I can see that it's there in the data, but I've not yet managed to preserve it in the final image). You can also see quite clearly where the mask I used to restrict the HDRM processing used on the inner ring, ends.

Still working on it but I need a change of subject for a while - I can see M57's with my eyes closed this evening. I think I'm more pleased with the galaxy at the 1 o'clock position than the main target...!

As always, comments and suggestions very welcome - happy to let others have the stacked frames if they want to have a go.

Exposure details below the image. My wife (who has been ignored all day in favour of Pixinsight) took one look at this and said "Sauron's Eye"...

Thanks

Nigel

16 x 600s L
16 x 600s R
10 x 600s G
10 x 600s B
13 x 1200s H-alpha

TOA150 @ f/11 / Atik460 / Mesu200

[wimvb]

That looks pretty decent to me.

If you're having trouble with HDRMT, try just using a star mask to protect the brightest stars (set scale to a high number)

Some of the stars in your image have magenta cores. This is common if you use Masked stretch or arcsinh stretch. Here's a procedure to correct this.

http://pixinsight.com.ar/en/info/processing-examples/28/maskedstretch-stars-sores.html

[NigeB]

7 hours ago, wimvb said:

That looks pretty decent to me.

If you're having trouble with HDRMT, try just using a star mask to protect the brightest stars (set scale to a high number)

Some of the stars in your image have magenta cores. This is common if you use Masked stretch or arcsinh stretch. Here's a procedure to correct this.

http://pixinsight.com.ar/en/info/processing-examples/28/maskedstretch-stars-sores.html

Thanks for your comments and link, Wim. I did use a star mask but perhaps hadn't set scale high enough - that looks like a useful repair process in the pixinsight resource. 

I think it's inevitable that I'll try this again. The raw data look good - it's the processing which is the issue. The lack of smooth transition between the HRDM'd core and the rest of the image is something I guess is easy to solve with layers in PS, but I'm sure there must be a way of achieving the same result in PI.  One of the case studies on the PI pages is M57 taken with a 1.2 m telescope, and they also use a mask to restrict the HDRM to the core - but without the same obvious boundary. Unfortunately they don't give much detail on the process.

Nigel

 

 

[wimvb]

2 hours ago, NigeB said:

Thanks for your comments and link, Wim. I did use a star mask but perhaps hadn't set scale high enough - that looks like a useful repair process in the pixinsight resource. 

I think it's inevitable that I'll try this again. The raw data look good - it's the processing which is the issue. The lack of smooth transition between the HRDM'd core and the rest of the image is something I guess is easy to solve with layers in PS, but I'm sure there must be a way of achieving the same result in PI.  One of the case studies on the PI pages is M57 taken with a 1.2 m telescope, and they also use a mask to restrict the HDRM to the core - but without the same obvious boundary. Unfortunately they don't give much detail on the process.

Nigel

 

 

Here's the missing information (at least my version of it):

1. create a star mask with large scale growth set to a higher than default number: 3 (or 4, depending on your data). Also check binarize and aggregate.

2. create a range mask to target only the nebula. Play around with threshold (lower range) to get the size you need. Then set the blurring parameter to a high value. This will give you a smooth transition.

3. Subtract the star mask from the range mask with pixelmath:

range_mask - star_mask

or my favourite (no need to rescale the result):

range_mask * ~star_mask

To tone down the HDRM result, you can decrease the brightness of the mask. In curvestransformation pull down the white marker (top right) to midway. This will give you an automatic blend of 50% HDR and 50% original image. It also allows you to be more aggressive in HDR.

Good luck.

PS: you could do the mask dimming in Pixelmath; just multiply by 0.5. But by using curves and preview checked, you can quickly adjust to taste.

[NigeB]

Wim,

Brilliant - that is really helpful. I'd not looked at the Range Mask - that fuzziness parameter sounds like exactly the thing I was missing.  Basically, I did a large scale star mask minus a small scale star mask - your method looks much more controllable. I'll give this a go and re-post when I've had a chance.

Thanks Again

 

Nigel

 

[wimvb]

My pleasure

[Stub Mandrel]

Wow Nige, that's excellent!

I need darker skies to get anywhere near that, and Lyra is heading out of my sky already ?

[NigeB]

2 hours ago, Stub Mandrel said:

Wow Nige, that's excellent!

I need darker skies to get anywhere near that, and Lyra is heading out of my sky already ?

Thanks Neil.  We are quite lucky, there are not many dark sky sites in the east midlands but our village is in one of the "least bad" parts for light pollution. On the negative side, I can't image planets because of trees to the south, so I have to image things high up!

I'm starting to see the Pleiades creeping above the observatory wall at the end of sessions now, so some nice targets coming up to replace the Ring.

Thanks

Nigel

[Rodd]

how did you achieve F11?  A powermate? or the 1.5x extender?  Very nice.

Rodd

[NigeB]

Thanks Rodd. I use a Tak ED 1.5 extender. It works well - optically it seems to be essentially invisible except for the desired change in plate scale, and it's lightweight (much lighter than my powermate) and has a good mechanical fit. It lives on the telescope at the moment, but I'm going to go back to f/7 for a few targets soon.

Nigel

 

 

[whatablanker]

I don't use pixinsight but it looks really good. It's great to see you've got the small spiral up to the right.