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Getting plate-solving status, please wait...
Sh2-155 Cave Nebula, 



    
        

            Anthony Quintile
Powered byPixInsight

Sh2-155 Cave Nebula

Getting plate-solving status, please wait...
Sh2-155 Cave Nebula, 



    
        

            Anthony Quintile
Powered byPixInsight

Sh2-155 Cave Nebula

Acquisition details

Dates:
Oct. 29, 2022
Frames:
1153×120(38h 26′)
Integration:
38h 26′
Avg. Moon age:
4.37 days
Avg. Moon phase:
20.11%
Bortle Dark-Sky Scale:
3.00

RA center: 22h58m06s.64

DEC center: +62°3000.2

Pixel scale: 1.032 arcsec/pixel

Orientation: -36.079 degrees

Field radius: 1.049 degrees

WCS transformation: thin plate spline

More info:Open 

Resolution: 6101x4028

File size: 36.0 MB

Locations: Home, Flagstaff, AZ, United States

Data source: Backyard

Description

Happy Halloween! Welcome to my Cave!

Since the temps have been cooling substantially as the northern hemisphere shifts into autumn, I thought I'd do an experiment in using Pixinsight as a space heater to warm the office. It was cozy in here after calibrating and integrating 1153 subs. It took the fairly decent iMac that I have approximately 37 hours to complete this integration of 38.4 hours of exposures.

I really love the parts of the sky like the Cave Nebula that have so many diverse colors in nebulae, dust and stars. I wanted to get a lot of time on this because it is such a dark area around the main nebula. I am pretty happy with this outcome.

I really need to give a shout-out to @Adam Block again. I have been using his Fundamentals tutorials, which are really the best instruction on Pixinsight that I have found by a long shot. More pertinently, though, his recent NGC 1333 tutorial had numerous great techniques and epiphanies for me. I highly, highly recommend that anyone who is struggling with the best ways to apply, or general use of, Pixinsight get signed up on the Fundamentals courses. Here's a link to his web site: https://www.adamblockstudios.com/

I don't get anything special from Adam, I just really appreciate his efforts to help me, and everyone else, out with this stuff.

Comments

Revisions

    Sh2-155 Cave Nebula, 



    
        

            Anthony Quintile
    Original
    Sh2-155 Cave Nebula, 



    
        

            Anthony Quintile
    B
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    D
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    E
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            Anthony Quintile
    F
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    G
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    H
  • Final
    Sh2-155 Cave Nebula, 



    
        

            Anthony Quintile
    I

B

Description: "Unclipped"/ lightened up the darkest nebula. I accidentally pulled the blacks in too much early on in the process.

Uploaded: ...

D

Description: Since I am in a bit of a whirlwind of learning and experimenting with Pixinsight, I wanted to revisit this image to address two primary concerns:

-I had clipped the blacks in the darkest nebulae inadvertently in the first iteration and made a half-assed attempt to fix that that I wasn't happy with. This time I fixed this by not making that mistake while I did my initial HT stretch.

-The image suffered from an overall blue cast in the darker end of the histogram, and that doesn't seem accurate or appealing. It was especially apparent in the color of the dark nebulae, which doesn't seem accurate since so many images of dust in space seem to be more brown?

Adam Block does address the blue background issue in the NGC 1333 tutorial I referred to in my main description here. I used his technique of applying DBE to the starless image to remove the blue from the back ground. I also then used SCNR a bit on the blue (and the green, of course) to pull it down.

As I look through the History Explorer on this workflow, it seems like the starless DBE neutralized the blue that I think we'd all like to see out of the bright reflection nebula on the right of the image. The blue is gone before applying the SCNR Blue. Some natural seeming blue still remains throughout the image, (not just stars, that wouldn't count), and the stars in and around the bright reflection nebula seem to be whitish, so I wonder if this reflection nebula should actually be white? I am not sure, but honest application , ( a few times to check different results), of DBE seems to balance the blue out of this part of the image.

Another thing that I changed was to do my initial DBE after PCC, counter to current conventional wisdom as I understand it. I don't have a lot of gradients in my integration, and I was getting weird results from doing DBE first, even after trying various approaches and selection placements and numbers in DBE.

DBE and Background Neutralization, (applied during PCC in my case), are powerful tools and I've seen so many folks, either blythely or expertly(?), apply them in a seemingly haphazard way. When I experiment with them I can get very different results with small changes. I hope to develop better familiarity with them so that the results I get are consistent and desirable. I think especially with a field full of nebula, with very little actual background, it seems hard to use them to affect only the background.

I think this version seems more refined than the previous, and holds up better in the small details if I zoom in.

Uploaded: ...

E

Description: Darkened slightly, fixed bright star halo.

Uploaded: ...

F

Description: Today I learned about the complication of needing use the ICCTransformation Process before saving and image as a PNG in Pixinsight.

Most of my processing to date has been finalized in Photoshop that renders PNGs that look like the PSD file. This is not true for Pixinsight. There is a good tutorial here: https://www.lightvortexastronomy.com/tutorial-preparing-images-for-publication.html

Uploaded: ...

G

Title: My first APOD!

Description: I've only submitted for an APOD twice, and my second time was a charm!



https://apod.nasa.gov/apod/ap221130.html

Uploaded: ...

H

Description: Upon some prodding, and because of my own obsessiveness, I wanted to correct the color of LBN 524, the reflection nebula on the right hand side of the image.

My earlier iterations had shown this as blue. PCC, and/or maybe the way I was applying Background Neutralization, was yielding a blue cast to the whole image which I was trying to correct, but this caused the loss of the blue in this reflection nebula, (see my previous revision description for more details). A cursory application of the new SPCC yielded a pale blue reflection nebula, but not as much of a blue cast to the whole image.

Because I was otherwise pretty happy with the rest of this image, I used a previous iteration to mask the blue nebula into the final iteration rather than completely reprocessing using SPCC. I think I was able to get this to look pretty natural and a true representation of the colors of all the nebula.

Uploaded: ...

I

Title: Reprocessed from original integration

Description: This object is a real challenge to work on. There are so many different colors in the nebula, and a lot of different stuff going on, so it always feels a bit "too much".

I shot and processed this originally just before SPCC was released, so I was using PCC. I didn't trust the colors I had originally, thinking I had screwed something up, (DBE maybe?), and made the background too blue. In my zeal to neutralize the blue, I tweaked the whole thing towards yellow/orange, which wasn't really correct. I then was assured by others that the reflection nebula on the right should be blueish since it is illuminated by a blue star. My futzing had washed out the blue from this area. To band-aid this I had originally adjusted a layer in Photoshop and painted through a mask. Super cattywampus.

I wanted to reprocess this using not only SPCC, but BlurX and some other new-to-me tools, and trusting that that the colors in the dark areas here are actually in the blues. Additionally, since I have been reprocessing a lot of older data I have become more familiar and comfortable with a lot of PI processes and techniques.

This version definitely treats the fine details better, and I think the color is more correct.

I did rely on Photoshop a bit more than usual to correct/balance some background brightnesses (darknesses) that may have resulted from a less-than-optimal application of DBE. I did, however, successfully protect the dark nebulae in the object throughout the processing well with GAME Script generated masks. I think I really nicely retained some dynamic range in those dark areas.

I reduced stars a second time because the stars add to the overall chaos and I think the image benefits from less pronounced stars. Hopefully the late-process star reduction didn't screw anything up like the last time I used it. I looked closely and I think it's OK.

Since there is so much going on here, please take some time to zoom in on the max-resolution version and see what you can!

Uploaded: ...

Sky plot

Sky plot

Histogram

Sh2-155 Cave Nebula, 



    
        

            Anthony Quintile