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Can you help me with this image?

astrophotography dslr
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#1 Astrojourneyuk

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Posted 31 October 2020 - 06:54 AM

Hi,

 

This is my first post so please go easy. smile.gif

 

I have been trying some astrophotography over summer with some success. I have a Canon DLSR 60D (astro-modded), SkyWatcher Star Adventurer mount and a SVBONY Light Pollution Filter.

 

A few things I'm having trouble with include, focussing, vignetting and post processing. I'm not sure if the end result image is due to not enough data, out of focus, artefacts with the light pollution filter etc.

 

Here is my end result of the heart and soul nebula. (I tried inserting an image but it didn't work)

 

https://drive.google...iew?usp=sharing

 

What I think seems to be the issues with this image is the stars are all very red and there is a central red circle that doesn't quite feel like the nebula fully.

 

Here is the original stacked and un processed TIFF - https://drive.google...iew?usp=sharing

 

Thanks

Marc


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#2 Ethanwyh

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Posted 31 October 2020 - 07:47 AM

This is a result from a hard stretch. It shows a circle with artifacts along the perimeter of the image (no, not the red borders)
Also, note that there is a dark patch at the bottom right of your image, this is either an internal reflection from the filter (if you used any) or a dust mote. 

1. Did you take flats/proper flats?

2. Can you confirm if there are any light leaks (Less likely imo)

circle.jpg


Edited by Ethanwyh, 31 October 2020 - 07:48 AM.

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#3 kathyastro

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Posted 31 October 2020 - 08:04 AM

A few things I'm having trouble with include, focussing, vignetting and post processing. I'm not sure if the end result image is due to not enough data, out of focus, artefacts with the light pollution filter etc.

Marc

Hi, Marc.

 

You are correct in assessing the areas that need work: focussing, vignetting and post processing.  I would add collimation.  And you need more data.

 

Your stars are fairly tight, but not quite "there".  I would say that your focus is close, but not exact.  Use a Bahtinov mask.  The star shapes look a little funky, suggesting a collimation issue.  But the shapes are not consistent across the image, so there might (also) be some tilt in your image train.

 

You definitely have a vignetting and dust-bunny problem.  You need to take flats.  It is possible to compensate a bit in post-processing by doing a background extraction, but that tends to leave its own artifacts.  Better to nip it in the bud at the calibration step.

 

After doing a background extraction to deal with the vignetting, there wasn't enough left to do a decent stretch.  So, you need to accumulate a lot more data, with either longer exposure times or more frames.

 

On the plus side, your tracking and/or guiding look pretty good.


Edited by kathyastro, 31 October 2020 - 08:05 AM.

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#4 Astrojourneyuk

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Posted 31 October 2020 - 08:49 AM

Thank you to you both for your helpful comments. One thing I forgot to mention is that I was using a Canon EF 70-200mm f2.8 lens rather than a telescope.

 

I have heard of Bahtinov masks which sound like they would help.

 

I had to google dust bunnies to find out what they were. :)

 

I find this hobby really exciting and massively frustrating at the same time. Mainly frustrating due to the sheer amount of cloud in the UK. It's clear next week but then with a full moon. Urgh.

 

Looking at the post processing example Ethanwyh provided it's encouraging to know that the colours of the stars aren't necessarily capture being the issue but more post processing. I had another go just now and the resulting image was better, but still not as clear as yours.

 

If anyone has any good tutorials to share I'd very much appreciate that.

 

Thanks again for your excellent help.

 

Marc


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