Two Collections for Comparison:  C11 and Stellarvue 130

I am going over the Sharpless2 Objects again with my new C11 and a few more years experience. 

Here I am looking to get a little more detail now that I have my hands on AI tools and GHS and leave this in greyscale. 

This version is only about 2h of Ha and processed with BlurX and NoiseX and GHS with a light retouch of NoiseX after the stretch.

The area is full of H-alpha and took several passes of GHS to get all the gradients sorta balanced.

On this image I also did some research on the effects of AI processing on star counts... a proxy for image quality... after a discussion with the Alex Woronow:=MsoNormalThe L image is the 8 best images by SubFrameSelector (SS):  Star count 1091. 
Throw all 16 images in and count goes up to 1236. 
Throw out the 2 worst images by SS, goes up to 1288. 

So, the internal weighting in Weighted Batch Preprocessing is not enough to get rid of marginal images, if they are included in the stack.

It is also of interest is look at what happens to the star  counts with BlurX and NoiseX 3405 and 7145.

Anyway, my bottom line is that you do need the SS but that the impact of BlurX and StarX on star count is at least an order of magnitude greater that the impact of SS or weighting. 

Finally, all this AI, IMHO, just sets up the image to be piped into GHS and careful stertching. 



Previous Images for Comparison:

Below is a wider angle image taken with my Stellarvue and a close up of the Sh2 objects... if you like RED color.  The first one is much wider angle than the C11 and gives a nice show of the H-alpha in the region.


Sh2 99 and 100


Sh2 99 and 100 HA RGB

A Note On Why Greyscale often Looks More Detailed Than Color:

I've had some discussions on this topic and my simplistic understanding is both 1. physiology and 2. physics (and 3. art theory):

1. A quote:

To fully know why this happens, we have to understand how we see objects using our eyes. There are essentially two ways in which we see things with our human eyes, through the Cone cells in our eyes and through the Rod cells.These two receptors serve different purposes. The Cone cells are the one responsible for sensing colors and are most active during the day. In the night, however, we tend to use the Rod cells because they are better in low light conditions and in sensing motion. But they have a disadvantage of not being able to perceive color.

So, when you go color you are using the less detail oriented system in your eye.

2.  On the physics, my simplistic idea is that the signal is in all three channels in L (RGB combined) but in primarily Red Ha the signal really is 1/3 as strong.  If you add in the Hb signal as say 1/3 more to the B channel, image looks brighter....

3.  Anyway, on top of this, if you look at Ansel Adams work with the Zone system and also the guys with GHS, you want the histogram allocated across the whole dynamic range.... in Ansel's words paraphrased 1/11th of the signal in each of the 11 grey zones.  So you look at his images and they are pleasing in part because he burned and dodged his images to get this allocation of light... of course his captures were carefully calculated to get this from the start.  Variety in Zones is the spice of life in B&W.

Basic Information From GalaxyMap about Sh2 99 and 100:

This star formation complex is embedded in the massive W58 radio source and molecular cloud, and is catalogued by Avedisova as SFR 70.29+1.60.

The region also includes Sh 2-100, 5 masers, and numerous additional radio and infrared sources including 7 HII regions.

Available distance estimates suggests that the W58 molecular cloud is located in the Perseus arm.

This HII region is part of the W58 radio complex. 1

A major study of this star formation complex appears in a 2010 paper and finds 7 HII regions. 2

Notes: 

1. ^ Georgelin, Y. M. & Georgelin, Y. P. (1976). "The spiral structure of our Galaxy determined from H II regions", Astronomy and Astrophysics, Vol. 49, 57-79.

2. ^ Samal, M. R., Pandey, A. K., Ojha, D. K., et al. (2010). "A Multiwavelength Study of Star Formation in the Vicinity of Galactic H II Region Sh 2-100", The Astrophysical Journal, Vol. 714, 1015-1036.


Distance Estimates:

6700 pc

8000 pc +/- 2500

GENERAL NOTE ON SHARPLESS2 OBJECTS>>>>>>>>>>>>>

There are 313 Sh2 objects.  All now imaged by yours truly.  These are basically the Hydrogen Alpha and other ionized nebulae around the edge of the Milky Way.

This is my collection:

Sharpless2

Wide-Angle Hydrogen Alpha Nikon Image Sh2 79-171

Please note there is also a Sharpless2 Group with now more than 3000 examples.

Sharpless2 Group

Other useful links include:

Gary Imm's Collection

GalaxyMap's Collection

The Sharpless Catalog

The MDW H-alpha Sky Survey

Reiner Vogel's detailed observing catalog

Hope you enjoy these obscure but interesting objects...