Red around M45

[Scooot]

I took this yesterday with my recently acquired Star Adventurer, 200mm lens with my Canon, 1 minute exposures on ISO800. I also used an Astronomic Clip Filter. I stacked about 6 of 12 images and used one dark. I was just trying it out really but I've noticed some little red rings around the main stars. Are these the result of the filter on any surrounding gas or something else? Any info gratefully received.

[Knight of Clear Skies]

Hi, it's probably a little chromatic aberration, the blue and the red focusing at different points. The focus may be a little out, or stopping down a little may help. What lens and aperture setting did you use please?

[Scooot]

Hi, it's probably a little chromatic aberration, the blue and the red focusing at different points. The focus may be a little out, or stopping down a little may help. What lens and aperture setting did you use please?

Thanks. It was an EF 55 - 200 (1:4.5 - 5.6), set near 200 at f5.6.

[D4N]

It can also be IR bloat if you have a full spectrum modded DSLR but are using the non CCD version of the clip filter you will get a lot of unfocused IR ruining bright objects.

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[Knight of Clear Skies]

OK, a few things that might help:
- There is a lot more detail hiding in your image, 6 minutes of data at ISO 800/f5.6 will show hundreds of stars. DSS often produces very dark images by default, the histogram needs stretching out.
- Also, DSS doesn't colour balance automatically, so this may be why the haloes are red, it might not be CA at all.
- Stacking with a single dark won't improve the image, either stack with maybe 12-30 darks or none at all. I still don't bother with darks myself, although I do take 30 dark bias.

With a zoom lens wide open the star shapes will suffer a bit, this is what I got with my 250mm zoom lens at f5.6:

That's a single 1 minute sub with a rough colour balance and stretch and very heavy noise reduction applied. The stars are distorted, especially in the corners, and there are haloes around the stars, which can be more easily seen in the full size version. Stopping down a little can improve the star shapes at the cost of less signal. I get better results with my 40 year old and very cheap 200mm SMC Takumar f4 lens at f5.6 than with my zoom lens.

Hope that's some help and that you enjoy the lens imaging.

[Scooot]

It can also be IR bloat if you have a full spectrum modded DSLR but are using the non CCD version of the clip filter you will get a lot of unfocused IR ruining bright objects.

Sent from my iPad using Tapatalk

Thank you, mines unmodded. Sounds like knights probably correct being chromatic aberration & focus.

[Scooot]

OK, a few things that might help:

- There is a lot more detail hiding in your image, 6 minutes of data at ISO 800/f5.6 will show hundreds of stars. DSS often produces very dark images by default, the histogram needs stretching out.

- Also, DSS doesn't colour balance automatically, so this may be why the haloes are red, it might not be CA at all.

- Stacking with a single dark won't improve the image, either stack with maybe 12-30 darks or none at all. I still don't bother with darks myself, although I do take 30 dark bias.

With a zoom lens wide open the star shapes will suffer a bit, this is what I got with my 250mm zoom lens at f5.6:

That's a single 1 minute sub with a rough colour balance and stretch and very heavy noise reduction applied. The stars are distorted, especially in the corners, and there are haloes around the stars, which can be more easily seen in the full size version. Stopping down a little can improve the star shapes at the cost of less signal. I get better results with my 40 year old and very cheap 200mm SMC Takumar f4 lens at f5.6 than with my zoom lens.

Hope that's some help and that you enjoy the lens imaging.

Thanks again,

Yes I could see loads more detail as I moved the histogram which also turned the background a brighter blue. It was late so I left it as it was but then wondered about the redness. I have a lot to learn. Thanks for the info about the darks, I'll have another play with it.

Also I used AS2 to stack not DSS although I wonder whether AS2 is better for planetary.

btw, I like your image, something to aim for

[Scooot]

Think it must have been the lens. I took this with my baby tak on the star adventurer tonight. 10 of 20 images, 1 minute at ISO 800. No darks etc.

Looks like I've got some vignetting. Wonder why it only shows when I upload it here?