SH2-119 Clamshell Nebula

[don4l]

This is SH2-119 in Cygnus.  It sits just under the North American Nebula.  I tried to image this last year, but I couldn't get a result that was at all acceptable.  I was using old Astronomik filters which had appalling halos.  This was taken with Chroma Ha and OIII filters.   Unfortunately, there is very little OIII in this, (but there is loads of SII). 

Hopefully, I will have a decent SII filter next year, and I will come back to this.   The Blue data was almost identical to the OIII as far as I can see, and only takes a fraction of the time.

Camera STL6303,  OTA  FSQ106 @ F3.6, Mount:  EQ6.

120m Ha,  110m OIII, 12m Green, 12m Blue.

CCDCiel, CCDStack, Gimp.

Any advice would be very welcome.

 

[alan potts]

Lovely shot of another I haven't seen before. I must find this catalogue in C-du-C to be able to locate these lovely areas of sky, feel it would be one for Borg 77mm wide area to cover.

Alan

[wimvb]

Thst's s very nice image of an unusual object. As the astrophotographer Metsavainio wrote, it's reminiscent of a wide screen version of the Rosetta nebula. I just wonder what happened to the small stars in your image? The star field reminds me of too aggressive star reduction in Pixinsight. But you used Gimp. 

[don4l]

1 hour ago, alan potts said:

Lovely shot of another I haven't seen before. I must find this catalogue in C-du-C to be able to locate these lovely areas of sky, feel it would be one for Borg 77mm wide area to cover.

Alan

The Sharpless catalogue is full of slightly unusual Ha objects.  I get the feeling that these are ignored because people used to think that Ha imaging was a bit difficult.  For whatever reason (Light pollution, optics, camera????) I find Ha much easier than RGB, so these objects are much easier for me than Galaxies.

The Sharpless catalogue  is part of the "LBN" catalogue on this page :-

https://www.ap-i.net/skychart/en/documentation/installation_of_extra_catalogs

 

Deal Salman maintains a very good website, which is a very good reference for the Sharpless imager:-

http://www.sharplesscatalog.com/sharpless.aspx

 

[don4l]

36 minutes ago, wimvb said:

Thst's s very nice image of an unusual object. As the astrophotographer Metsavainio wrote, it's reminiscent of a wide screen version of the Rosetta nebula. I just wonder what happened to the small stars in your image? The star field reminds me of too aggressive star reduction in Pixinsight. But you used Gimp. 

Thank you.

You are absolutely right about the  stars.   The image was almost nothing but stars when I did the first colour combine.  So, your comment about aggressive star reduction makes complete sense.   I used two different methods at different stages, which won't have helped.  I didn't notice the issue until I did some final touch ups.

I'll have another go at this tonight to see if I can improve things.

 

[ollypenrice]

This is very nice. I have it in a NAN widefield mosaic but, because it is significantly fainter than the NAN, I didn't feel I could stretch it too far without making it dishonestly bright relative to its neighbour. Doing it on its own like this gives you more freedom to bring it on!

Olly

[don4l]

I said that I would have another go - and I almost wish that I hadn't! 

I've reprocessed the image, but I don't think that it is any better.  I've added in some of last year's SII data to the green channel, using layer masks to keep the halos at bay.

I need to do some research on star removal, and replacement.

 

[wimvb]

6 hours ago, don4l said:

need to do some research on star removal, and replacement.

Starnet++ is your friend for this job. It's available as a standalone program as well as a script for PixInsight. Just google it. Process one copy of the image for stars, and one for maximum impact for the nebula. Remove stars in the latter and replace with those of the former. 

Btw, you got more colour variation in the nebula. It looks better, imo. 

Edited October 15, 2019 by wimvb

[alan potts]

I like the second take as well, very nice image.

Alan

[glowingturnip]

I like that, especially the 2nd version.  The blue star in the centre gives it a nice punch of colour contrast.  I guess that's quite a large fov isn't it, too big for my set up

[don4l]

6 hours ago, wimvb said:

Starnet++ is your friend for this job. It's available as a standalone program as well as a script for PixInsight. Just google it. Process one copy of the image for stars, and one for maximum impact for the nebula. Remove stars in the latter and replace with those of the former. 

Btw, you got more colour variation in the nebula. It looks better, imo. 

Thanks, Wim.  I've downloaded it and I'll have a play tonight.

 

[don4l]

2 hours ago, glowingturnip said:

I like that, especially the 2nd version.  The blue star in the centre gives it a nice punch of colour contrast.  I guess that's quite a large fov isn't it, too big for my set up

Your FOV will be about 1/3rd of this image.  There are a couple of parts that would make a very nice image, and your stars would be much easier to deal with.  (My camera's pixels are too big for this focal length). 

 

[gorann]

Nice! A new one to me too, at least as an object on its own. Regarding star processing, I am not sure it would help to process them separately - you still have to put them in at the end and need to shrink them before that (but maybe - I have never tried it). If you use PI you could try this method by Adam Block (again, I have not got around to try it myself yet):

https://pixinsight.com/forum/index.php?topic=13567.0

By the way, what caused that vertical line to the right? Looks too broad to be a satellite.

[Jkulin]

Don, can I ask how you are getting the colour images in CdC, if I choose to download I just get the B&W, so I am just wondering if you have a different catalogue? Can you advise please?

This really is a lovely image.

[don4l]

25 minutes ago, gorann said:

Nice! A new one to me too, at least as an object on its own. Regarding star processing, I am not sure it would help to process them separately - you still have to put them in at the end and need to shrink them before that (but maybe - I have never tried it). If you use PI you could try this method by Adam Block (again, I have not got around to try it myself yet):

https://pixinsight.com/forum/index.php?topic=13567.0

By the way, what caused that vertical line to the right? Looks too broad to be a satellite.

The vertical line is a bad column in my CCD chip that didn't calibrate out.  There were four of them, and I had to use the "heal" tool in Gimp to get rid of them.  I didn't do a very good job of it!

The STL6303 is  an old camera that seems to have suffered terribly from 8 years of storage.  My best guess is that cosmic ray hits have caused the damage.  The dark frames are truely awful.  The biggest problem is that the strength of the hot pixels and bad columns seems to vary from one night to the next.

What is interesting, is that an Atik 16HR that was stored with it has suffered no visible damage at all.  It's dark frames are the same now as they were in 2007.

 

[don4l]

12 minutes ago, Jkulin said:

Don, can I ask how you are getting the colour images in CdC, if I choose to download I just get the B&W, so I am just wondering if you have a different catalogue? Can you advise please?

This really is a lovely image.

I have a few methods.  The simplest is to just use Gimp.  I take a screen grab of CdC as a base layer.  I paste a copy of my image on top and then simply line up using the bright stars.

 

The next method is what I use all the time.  I platesolve one of the first subs that I take.  I then paste this header into a processed image  which CdC can display if it is in a directory selected under "Setup -> Pictures -> Image Archive".  I use ASTAP to do the platesolving and the pasting into the stacked (and scaled) image.  I also use ASTAP to bin the image to reduce the size.  CdC slows down if the images are too big.  This method is remarkably accurate.  I can click on one of my stars, and CdC will identify it!  I can then use CdC on subsequent nights to make sure that I am properly centered on the target.

 

 

[don4l]

I've taken a few days to reprocess the image because I had to go back to scratch.  The camera was only at -2C for these images, and I had to shoot new 10m darks!!!

I've used Starnet to remove the stars from a new colour image.  I made a separate colour image of the stars ind CCDStack with unstretched images (Ha, G, and B).  The stars were then added back as a "Lighten" layer in the Gimp.  I haven't done much other processing.

I honestly don't know what to make of the result, so comments are very welcome (Even "Hate it").

Anyway, here it is:-

 

[don4l]

Here is what the centre of the image looked like before using Starnet:-