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NGC 6992, Eastern Veil Nebula.  Revised OSC Image, improvement on old data., Alan Brunelle
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NGC 6992, Eastern Veil Nebula. Revised OSC Image, improvement on old data.

Revision title: Revised 4/2023

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NGC 6992, Eastern Veil Nebula.  Revised OSC Image, improvement on old data., Alan Brunelle
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NGC 6992, Eastern Veil Nebula. Revised OSC Image, improvement on old data.

Revision title: Revised 4/2023

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Description

Revised 4/2023:
I thought that the original image was pretty good.  In fact on the level of the Technical Card or even the next, I am pretty satisfied with this.  But I still decided to reprocess this from the subs with all the new tools currently on hand.  I believe that this is significantly improved.  In fact, in my original description, I concluded that with OSC, I would never be able to see many of the fainter structures that the narrow band crowd seems to see in their images.  I believe that I have pulled out much of that this time.  Because of this, I decided on a stronger star reduction.  Only partially with BXT.  By far most of the star reduction here was done using Bill Blanshan's star reduction script.  I am finding that I prefer to use Bill's methods for most of the star reduction for two reasons.  First it very well preserves the relative brightness between classes of stars, thereby preserving some sense of the variety of stars and apparent depth of field.  But more importantly, it is best to use late in the processing, sometimes almost the last step.  This is when it is so important to dial in the stars.  It is hard to achieve that unstretched, when BXT is best used.  And it is nearly impossible to assess the exact degree of star reduction so early in processing.  And as far as I have detected, Bill's is less prone to color shift.  Not only that, Bill's method is so fast!

BXT certainly was responsible for the accurate and gentle sharpening of structures.  And for this data, star correction on this data was critical because it was early in my use of the RASA and I had serious tilt issues.  In fact, you can find in one corner some star-doubling that occurred because of the extreme coma those stars had.  But it is not visually an issue, unless you go looking for it.  In any case I am so happy with the improvement that I am providing a Starless version and also a B&W version.  The Starless is nice because there are still enough stars in the final version that hide galaxies and also some of the small fragments of nebulosity that are scattered about.  I find the B&W version nice to remove the visual confusion of color when looking at the complex webs of nebulosity in the brighter sections.  Yes, the colored sections certainly add depth information and the relationships between these features.  But there is something to be said for the B&W, so I provide that for your enjoyment.

Because this is a OSC image, I tried to leave this color with a saturation that is somewhat subdued.  Not super subdued, but just not over the top.  Personal choice and I thought it was faithful to the original.  Its not like I can see any color when I view this through my 5 inch.  So I can't try to make this too realistic!

Finally, I have to say that NGC 6992 has to be one of the most photographed objects presented on AstroBin.  Yet it is probably the least awarded!  I went through so many pages of images without even seeing an acknowledgment!  What gives?  C'mon judges, give this one respect!

Old Description:
The Eastern Veil is thought to be the result of a shock wave moving through the progenitor star's remnant planetary ejecta. The progenitor having gone supernova well after much of the star's material was ejected. An example would be the massive clouds of gas and dust emitted by a Wolf-Rayet star in advance of the inevitable (?) explosion. The question mark is because I have recently read that some massive stars are so prolific in mass ejection that they can actually reduce their overall mass beyond that which would eventually allow for a supernova. This supernova occurred some thousands of years ago. Most of the emitted gas has expanded and cooled and is not visible, however the supernova shock wave is exciting that gas into these overlapping crepe-like emission veils. The Eastern Veil is part of the much larger Cygnus Loop complex. My guess is that this may have been much brighter some centuries in the past because of increased density and concentration and energy of the shock wave.

As old as this object is and delicate as this structure appears, it actually is bright enough for visual telescopy. I can barely make this out visually and also the Western Veil with my 5 inch Mak Newt. And it is even more easily distinguished when employing a UHC filter. But, of course, no colors!

Given that this is a visual target, you would think that my 240 sec exposures here seem rather extravagant for an 11 ich RASA. At 240 sec, the larger stars were getting close to saturation. and the dense starfield is something to deal with. I see that this object is a very popular subject, though, by far, most often in narrow band. Narrow band appears to have the advantage of gaining some of the very faint Ha structures outside of the main Veil body, and as with the use of a UHC filter for visible viewing, the narrow band filters no doubt beat down a lot of the star field. I am not sure I could get much more with longer subs or more subs. Unlike my last few projects posted here, this one was not shelved because I had too little data, but rather my experience with the Western Veil left me less than excited to complete this project. I have since learned some new processing techniques and thought that I would give it a go. I am happy enough to post this and motivated to get back and reprocess my Western Veil as well!

Finally, I note a decent number of galaxies can be seen in this field of view, especially on the side ahead of the leading edge of the shock wave (Left). Even a couple within the bright Veil. However, I could only find a few within the Cygnus Loop area and I wonder if this is because the dark dust and gas is more dense and opaque on that side? My processing has not been too kind to these small background objects however!

Comments

Revisions

  • NGC 6992, Eastern Veil Nebula.  Revised OSC Image, improvement on old data., Alan Brunelle
    Original
  • NGC 6992, Eastern Veil Nebula.  Revised OSC Image, improvement on old data., Alan Brunelle
    B
  • NGC 6992, Eastern Veil Nebula.  Revised OSC Image, improvement on old data., Alan Brunelle
    C
  • Final
    NGC 6992, Eastern Veil Nebula.  Revised OSC Image, improvement on old data., Alan Brunelle
    D

B

Title: Starless of the Revision

Description: See under Description

Uploaded: ...

C

Title: B&W version of the Revision

Description: See Description

Uploaded: ...

D

Title: Revised 4/2023

Description: See updated Description.

Uploaded: ...

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NGC 6992, Eastern Veil Nebula.  Revised OSC Image, improvement on old data., Alan Brunelle