Author Topic: Western Veil Nebula Processing Assistance  (Read 303 times)

Offline sandconp

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Western Veil Nebula Processing Assistance
« on: 2019 August 05 19:56:08 »
I was wondering if I could have some assistance in processing my image of the Western Veil Nebula.  I have used PixInsight on Galaxies and Planets with lots of success but I have never done anything with nebula.

I will post the link here for my FITS File.  If you can help me, I would appreciate if you listed the steps to process my image so I could learn from it.

https://www.dropbox.com/s/3a3fd2la3qa6kzw/Stack_16bits_30frames_450s.fits?dl=0

Offline ngc1535

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Re: Western Veil Nebula Processing Assistance
« Reply #1 on: 2019 August 05 21:29:39 »
Hi Sandconp

Based on the image there are some suggestions that might help. They are more primary than object-oriented (e.g. nebulae, galaxies..etc) considerations.
You didn't mention them... but you might already be aware of them.

-The image appears to have out-of-focus stars. Is this the way the images usually are? Do you focus manually or with an automated method?
-It appears that vignetting is likely a bit of an issue. Do you take flats with your data?
-There are some hot pixels that did not calibrate out. Did you use dark frames (or calibrate) at the same exposure time and temperature?
-Since the hot pixels persist, it appears the data was not acquired in a dithered fashion. You might want to look into this..it will really help in a number of ways!
-Even though the data is not dithered randomly... image rejection should still help in the combination of frames to reduce hot pixels. An application of Cosmetic Correction will also be very helpful if no dithering and no luck with rejection. It seems like you have enough frames to make things cleaner.
-There is a blue bias to the data- and the nebula is not quite a typical white-balanced expected color. Did you use Photometric Color Calibration or regular Color Calibration?

There are some other things here as well... but the above is a good start and independent of the object you are working on.
Is this is the kind of information you were looking for?
-adam
« Last Edit: 2019 August 05 21:45:32 by ngc1535 »

Offline sandconp

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Re: Western Veil Nebula Processing Assistance
« Reply #2 on: 2019 August 05 22:40:44 »
I did a manual focus using a Bahtinov Mask using Sharpcap Pro with Live stacking.  The stacked file (FITS) is then brought in directly to PixInsight for post processing.

Here is my first attempt to try and process the Western Veil Nebula.  I know it's kind of ugly because there seems to be a lot of noise and I did not apply and darks prior to starting the capture.  In the past I never had to worry about applying dark frames with other objects such as M51.

https://www.dropbox.com/s/z5gcqs6ojntsbnr/NGC6960.tif?dl=0

Offline Andres.Pozo

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Re: Western Veil Nebula Processing Assistance
« Reply #3 on: 2019 August 06 00:29:30 »
I will post the link here for my FITS File.  If you can help me, I would appreciate if you listed the steps to process my image so I could learn from it.
Hi,
I think you should start mastering the basics.
First, the focus of the image is terrible, you need to improve it since a bad focus can not be fixed in software. Perhaps it is only one of the frames, but you should check it.
Second, I think that you have not calibrated the images (bias/dark/flat). This is easy to do and makes easier the rest of processing steps.
Third, I don't know Sharpcap, but I wouldn't use live stacking as the starting point of the processing. PixInsight has tools to select/discard bad frames and first class algorithms to align and integrate images. The step of discarding bad frames is essential: there can be problems in the guiding, focus, clouds, ... A bad frame can destroy a good image.


Offline dave_galera

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Re: Western Veil Nebula Processing Assistance
« Reply #4 on: 2019 August 06 00:35:13 »
Using SharpCap with live stacking is for visual use only, it is not intended to bring the stacked images in to a image processing package like PixInsight for the reason Andres pointed out.
Dave