Mosaic IC5070 Pelican Nebula

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BlackWikkett
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Mosaic IC5070 Pelican Nebula

Post by BlackWikkett » Sat Jul 27, 2019 10:20 pm

Some more live stacking of 6 panels to create a new mosaic. This time IC5070 Pelican Nebula. My main setup RC6 and ZWO ASI294 MC Pro. Each individual panel is 33 plus minutes. Follow the link to my flickr page https://www.flickr.com/gp/165305863@N04/hq39fa to see the individual panels. Used Microsoft ICE to stitch the panels. Not the most noise free images and had some trouble getting color balance consistent for all 6 individual images. I'm happy with the result based on the amount of time used to capture the images and create the final mosaic. Each panel is 30+ min plus clean up in Photoshop then assembling the mosaic in MS ICE I have a quick 4.5 hour project with a result I'm happy with. Image capture was broadcast live on NSN https://www.nightskiesnetwork.com/ Come by and have a look some one usually broadcasting nightly, weather permitting. Several SharpCap users and we're happy to answer questions.

ImageIC5070 6 Panel Mosaic 6 x33min WithDisplayStretch_stitch by Black Wikkett, on Flickr

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turfpit
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Re: Mosaic IC5070 Pelican Nebula

Post by turfpit » Sat Jul 27, 2019 10:46 pm

Nice work Wickett. IC5070 is a hard object as a single frame.

Have you considered (if it is possible) to stitch earlier? That way the final processing is applied to only one image. Maybe just equal stretch on each panel to bring out enough detail to enable stitching. With lunar, I stack, stitch, process but that is easier as it is a bright object with detail available on the individual panels. I haven't tackled a deep sky mosaic yet.

Dave

BlackWikkett
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Re: Mosaic IC5070 Pelican Nebula

Post by BlackWikkett » Sun Jul 28, 2019 2:15 pm

Thanks Dave, results were better than expected.

Since I'm live stacking each of the mosaic panels a lot of the processing is done on the fly as the image develops. My original hope was that once I captured the first panel and fine tuned color balance and stretch I would be able to apply those same settings to the following panels. This turned out not to be the case as the results were not acceptable. Probably thin clouds and changes in seeing of the 3+ hours of capturing images. Also I'm broadcasting on NSN and want to provide a pleasing image for myself and viewers. One of the main reasons I like live stacking so much. The immediacy can't be beat!

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turfpit
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Re: Mosaic IC5070 Pelican Nebula

Post by turfpit » Sun Jul 28, 2019 5:37 pm

Wickett

Ah right - I forget about the Live Stack aspect.
Probably thin clouds and changes in seeing of the 3+ hours of capturing images
I have the same issues with lunar mosaics - clouds and object illumination. I cut down the time for each panel to the minimum otherwise the mosaic looks like a patchwork quilt which can never be properly fixed. The long capture time brings about its own set of challenges - which makes your posted image even better.

Dave

donstim
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Re: Mosaic IC5070 Pelican Nebula

Post by donstim » Mon Jul 29, 2019 9:58 pm

Really nice! How do you keep the star bloating down while stretching? Did you do all the stretching in SharpCap, or did you apply further stretched afterwards in Photoshop? (I'm curious as to what "cleanup" you typically do in Photoshop.)

You are saving the images "Exactly As Seen" in SharpCap, right? Is there a reason you do that rather than "Save With Adjustments?" The former is limited to an 8-bit PNG, but the latter can be 16-bit. There doesn't seem to be a problem with dynamic range in these captures by saving the output as 8-bit images. Are you starting with a RAW16 color space in the camera controls?

Thanks -- I've learned a lot from you and Dave and am continuing that process!

Don

BlackWikkett
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Re: Mosaic IC5070 Pelican Nebula

Post by BlackWikkett » Mon Jul 29, 2019 11:49 pm

Thanks!

Photoshop clean up consist of the following: (Photoshop CC 2019 older version should work)
1. Crop to remove dithering artifacts on the image edges, need to be careful as the individual images overlap is only 10% for final mosaic
2. I use a 50% gray fill layer with difference blending
3. Threshold layer at about 25 level to identify a mid point source with eye dropper (shift Click)
4. Curves layer select gray point and use your previous selected source from threshold layer as source (this give a good staring point for white balance)
5. Levels layer set black point
6. Curves layer for "s" curve as needed for any additional stretch. usually not needed but for mosaic can help balance out the contrast
7. HLVG filter to remove green as needed
8. Colormancer Boundary Noise Reduction Filter

This sounds really involved but I can usually complete these steps in less than 5 min. Additional time can be devoted to removing hot pixels as needed.

I save 8 bit png as I'm using the small display histogram to make adjustments and stretching, color balance that's adjusted in Live Stacking is also preserved by saving "exactly as seen" The initial images are captured from the camera as 16 bit fit then Live stacking does the reset. I use gaussian blur and sharpening in SC also. I don't plan to print these images and only display online via flickr.com so 8 bit is just fine for my needs.

Keeping the stars from bloating I find comes to good focus and the miracle ASI294 camera. This thing has some outstanding dynamic range and it takes quite a lot to saturate the sensor.

If you have questions don't hesitate to ask I'm usually online on NSN if someone is broadcasting. Even if I'm not broadcasting I can go live and easily show you or anyone else interested the process I use.
Last edited by BlackWikkett on Tue Jul 30, 2019 4:53 pm, edited 1 time in total.

donstim
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Re: Mosaic IC5070 Pelican Nebula

Post by donstim » Tue Jul 30, 2019 12:38 am

I use the freeware GIMP for post processing. I'll have to see whether the PS features you use have cohorts in GIMP. I know most of them do, but I don't know about setting a threshold level for a gray point or whether there are tools like an HLVG filter or a Colormancer Boundary Noise Reduction Filter. It takes me a lot longer than 5 minutes to do the relatively small amount of post processing I do (typically levels, round stars, background fixes, curves)!

I have the same camera and believe I achieve good focus. But stretching usually (not always) stretches and "bloats" the stars for me.

Why use the small histogram at all? I only use the livestack histogram. It doesn't portray everything you do "correctly" in that histogram, particularly when using the color adjustment tools in the same tab, but it all seems to be accurately represented in the small histogram and in the "save with adjustments" saved file at 16 bits. In other words, I do all the adjusting in the live stacking histogram while viewing the small histogram for the effects of those adjustments. It may not be as easy or straightforward as making the adjustments directly with the small histogram, but you have the advantage of using the "save with adjustments" option. Or, are there adjustments that you can make using the small histogram that you just can't make using the livestack histogram?

Don

BlackWikkett
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Re: Mosaic IC5070 Pelican Nebula

Post by BlackWikkett » Tue Jul 30, 2019 4:44 pm

Using the display histogram and live stack histogram, my method. Use Lives stack histogram in logarithmic mode.

Live stack histogram is the raw data from the camera. The display histogram reflects post processing of stretch, noise reduction, sharpening and color.

Since I don't use preprocessing in SC image controls to get a close color balance using red and blue adjustments. The R, G, B and Lum curves in the live stack histogram are not aligned. In LS I'll auto stretch after 2 frames then auto white balance. These changes are reflected in small display histogram. Some more manual tweaking of the LS color sliders to align the peaks of the R, G, B and Lum histogram curves in the display histogram. Also applying an auto stretch in display histogram. Then I'll manually move the display histogram mid and black point to taste and what the current stacked image allows. As more data comes I'll fine tune LS color sliders and tweak the stretch in the display histogram. When complete I save as seen. This gives me a good starting point for the minimal post processing. This tends to be an interactive process that keeps me very engaged in the capturing the photons since i'm constantly adjusting to get the images i'm happy with. Some objects are a lot less involved and allow making a fewer adjustments.

Robin, If you happen to see this. The above process is why I'd love to have a larger display histogram that may be able to be popped out and pinned to the bottom or top of the display similar to how the Live stack is pinned.

Hope this all makes sense.

donstim
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Re: Mosaic IC5070 Pelican Nebula

Post by donstim » Tue Jul 30, 2019 5:13 pm

Yep, agree with all that. But I think you can do all the tweaking of color and stretching in the LS histogram (not touch the display histogram at all) and see the effects in the display histogram. (They won't be reflected correctly in the LS histogram since, as you say, that is using the raw data directly from the camera.) All this tweaking will be shown correctly in the display histogram and will be present in the 16-but png file saved under "save with adjustments." At least, that is what I think is happening in my experience.

BlackWikkett
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Re: Mosaic IC5070 Pelican Nebula

Post by BlackWikkett » Wed Jul 31, 2019 3:53 am

That's a good point Don, I'll have to give it try the next time I'm out. Now when that will be is anyone's guess. All the weather forecasting sites and tools I use seem to be in constant flux. I've only been in the Astronomy game for two years but seems the past summers have had more clear nights. Here's hoping for clear skies soon!

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