Eastern Veil Nebula processing help

[scitmon]

I had my first imaging session with my new equatorial mount last night which meant I spend a lot of the night familiarising myself with polar alignment and such things.  However, I did manage to get around 30 x 60 second exposures of the Eastern Veil Nebula with my unmodified Canon 700d and I am currently struggling to get a good image from the data using StarTools.  I have stacked with darks, flats and bias using DSS.

I'm wondering if I am expecting too much from 30 mins of data or whether I'm just rubbish at processing?  I have attached my stacked image and challenge any startools gurus out there to show me how its done!

stacked.TIF

[richyrich_one]

Not with startools but PI. This is all I could get with a quick stretch etc.

It is an Ha target so an unmodified camera will struggle with so little data. Focus is a lttle off too.

You're off to a good start.

Compared with a single 5 min sub from a modified 600D...JPEG straight from the camera with no processing.

[scitmon]

Thanks for trying, I asked for help over on the Star Tools forum as well and someone has managed to pull out this: 

 

Not had much luck getting anything like this myself.  Its clear I need more data.  I have sent for both my 1000D and 700D to be astro modified, so that should help with future efforts too.

[scitmon]

On 11/25/2017 at 01:32, richyrich_one said:

Focus is a lttle off too.

How can you tell this by the way?

[spillage]

This should put you on the right track.

 

 

[Jannis]

I gave it a quick go in PS, but i wasn't able to get much out of it either. Those at the star tools forum got much more nebulosity out of it for sure.

[wimvb]

On 2017-11-13 at 21:45, scitmon said:

I had my first imaging session with my new equatorial mount last night which meant I spend a lot of the night familiarising myself with polar alignment and such things.  However, I did manage to get around 30 x 60 second exposures of the Eastern Veil Nebula with my unmodified Canon 700d and I am currently struggling to get a good image from the data using StarTools.  I have stacked with darks, flats and bias using DSS.

I'm wondering if I am expecting too much from 30 mins of data or whether I'm just rubbish at processing?  I have attached my stacked image and challenge any startools gurus out there to show me how its done!

The veil is not exactly a beginners object, so you already got yourself a challenge by picking this target as a first try with a standard dslr.

I had a look at your image in PixInsight, and in all fairness I think you won't get a good image out of the data. As @richyrich_one already pointed out, you need a substantial longer exposure time for this target. In my experience, if a single sub doesn't show the object, it'll be very difficult to lift it out during processing.

The result from the Startools forum suggests clipping of the background to bring that under control. The veil itself still shows the kind of noise that is typical for the background of an image, streaks that are common in non-dithered dslr images.

Your stack also has a lot of light pollution (the orange colour cast). Light pollution can be removed easy enough, but not the noise associated with it. To remove that, you need:

1. The longest exposure time that your conditions (= setup + sky) allow.

2. Lots and lots of subs to average noise out.

3. Dithering to break up the pattern caused by remaining warm/hot pixels after calibration.

If your setup is the one in your avatar image, then you should be able to get single frame exposure times of about 2 minutes or more (be prepared to toss a few due to tracking issues). That is, if  polar alignment and balance are spot on. A light pollution filter will help, also with a modded camera.

In stacking, you can experiment with darks (leave them out) vs cosmetic correction and more aggressive pixel rejection. Some dslr imagers can get darks to work, and some can't (they use pixel rejection during stacking).

Hope this helps.

 

[happy-kat]

On 11/26/2017 at 22:57, scitmon said:

Thanks for trying, I asked for help over on the Star Tools forum as well and someone has managed to pull out this: 

Could ask for a copy of the section of the log file relating to that process.

Having had a quick go they did a lot in StarTools think they removed a lot of background stars and tightened the star shapes up too.

[scitmon]

12 hours ago, wimvb said:

The veil is not exactly a beginners object, so you already got yourself a challenge by picking this target as a first try with a standard dslr.

I had a look at your image in PixInsight, and in all fairness I think you won't get a good image out of the data. As @richyrich_one already pointed out, you need a substantial longer exposure time for this target. In my experience, if a single sub doesn't show the object, it'll be very difficult to lift it out during processing.

The result from the Startools forum suggests clipping of the background to bring that under control. The veil itself still shows the kind of noise that is typical for the background of an image, streaks that are common in non-dithered dslr images.

Your stack also has a lot of light pollution (the orange colour cast). Light pollution can be removed easy enough, but not the noise associated with it. To remove that, you need:

1. The longest exposure time that your conditions (= setup + sky) allow.

2. Lots and lots of subs to average noise out.

3. Dithering to break up the pattern caused by remaining warm/hot pixels after calibration.

If your setup is the one in your avatar image, then you should be able to get single frame exposure times of about 2 minutes or more (be prepared to toss a few due to tracking issues). That is, if  polar alignment and balance are spot on. A light pollution filter will help, also with a modded camera.

In stacking, you can experiment with darks (leave them out) vs cosmetic correction and more aggressive pixel rejection. Some dslr imagers can get darks to work, and some can't (they use pixel rejection during stacking).

Hope this helps.

 

Wow thank you, a lot of useful feedback there.  I'm expecting future attempts to be more successful as my polar alignment skills improve and my camera is being astro modded at the moment with Juan at cheapastrophotography.

Would you be kind enough to answer a few follow questions?

1. I don't have a guiding scope yet so I am just mount tracking the moment, should I still be aiming for 2 min exposures as you say?  

2. Do I need to introduce a significant pause between subs?  I was taking my subs back to back and I wonder if the camera sensor needs more 'cool down' time?

3. Is dithering (never heard of this before, just looked it up) possible without guiding?

4. Looks like I need to add a Light Pollution Filter to my wish list.  Looking at the FLO selection, there is quite a price difference between the Baader/ES ones and the IDAS ones.  Do the IDAS ones justify the price tag in comparison?

[wimvb]

1. Yes, just experiment. Keep the ISO at 800 or even less.

2. Some imagers do. Personally I've always considered it a loss of precious imaging time.

3. Dithering is introducing a random offset in ra and dec between exposures. Google "Tony Hallas astrophotography" for a youtube video. It's probably the very first hit.

4. IDAS filters seem to be better at keeping colours in eg galaxy images, while uhc filters are good for imaging emission nebulae. I use a Baader uhc filter to reduce LP. But if I had to choose again, I would probably get an IDAS filter. I've seen good results with it. Otoh, I do mostly galaxy and reflection nebulae imaging.

[wimvb]

In the mean time, I had a go at your data (PixInsight). Here's my effort.

(click on the image to enlarge)

- dynamic crop to get rid of stacking edges

- DBE to remove gradients

- colour calibration (background neutralization, color calibration)

- HSV repair script to repair star cores (there are still a few less brighter stars that have an ugly red core)

- masked stretch

- masked colour saturation and exponential transformation to enhance the nebula

- resample

[happy-kat]

Had another go in StarTools using modules:

crop | bin | repair | heal | layer and various masks, the background I found hard to do much with though I could neaten the stars and extract the star field to add back in one I had fiddled with the background

 

The mask around the viel was a bit clunky.  haven't got the colours right.

[scitmon]

Thanks for all your attempts, but I don't want to waste your time anymore. Its clear there is a lot of problems with my data.  I watched that Tony Hallas video today and learned about 'mottled colour' which evidently my data has.  I will be attempting dithering from now on with APT.  All part of the learning process!

 

I've also been looking into Light Pollution Filters quite a bit, but I am put off by the fact that I may be wasting my money because my local streets have LED lamps which might not be filtered out properly.  I even contemplated getting a spectrometer to look at what frequencies they output, but I think I'll stick to longer exposures and dithering for now and see how I get on.

[happy-kat]

Having searched on StarTools don't think I'll rush to follow Tony but see if somehow I can do dithering to help my noise. Even though my council had changed to led there still appears a noticeable orange glow so I guess there's still buildings with sodium lights in my area. I enjoyed trying to process another's data, helps with learning.

[wimvb]

12 hours ago, scitmon said:

I even contemplated getting a spectrometer to look at what frequencies they output, but I think I'll stick to longer exposures and dithering for now and see how I get on.

It's very easy to make your own, simple spectrometer with a cd. There are plans on the internet. You won't get exact wavelengths, but by clever use and comparison to known light sources, it should be easy enough to determine your main source of light pollution.