Noisy M20 (with M21)

[traveller]

Warm nights means warm sensors and more noise.
18 x 300 sec at 1600 ISO with equal darks.
ED80 on EQ6 with modded Canon 1100D (UV/IR clip in with UHC filter)
DSS and PS.
I need to take some cooler darks to match the sensor temp on the light frames. The stars are also slightly bloated due to poor seeing on Monday night.
Comment welcome.
Bo

[Tony_]

G'day Bo,

Your image is pretty good - just needs different processing.
It's a too purple (needs more green) and you can reduce the star bloating a little with processing. I played with it a bit and did this. With more time it could still be better.

Regards,
Tony.

[cometcatcher]

I agree with Tony. It's a nice image.

I'll post some screen grabs on the processing I did. Basically I just even up the RGB channels and the colour balance becomes more neutral. I also ran a minimum filter over the bright stars using the colour range tool with highlights selected to reduce bloat. It's a different look to Tony's but I guess we all process things a bit differently. The original is the first image.

[Tony_]

Yours is better Kevin. I only spent about 2 minutes on it plus I need to improve my processing skills.

Bo - it is quite a good image once it is processed better.

Regards,
Tony.

[traveller]

Thanks tony and Kevin,
Always great to get some processing tips from others.
Will have another go later and if I can improve the image.
Bo

[LightningNZ]

Nice stuff. That UHC filter really hammers the reflection nebula unfortunately.

[traveller]

Yes, I haven't tried imaging without uhc in my backyard, might try it one day and see what exposures I can get without lp washing out the photos.
Bo

[Tony_]

G'day Bo,

Another way to combat light pollution is to take an image of a white sheet of paper during sunshine. You will get a pinkish color. You need to adjust the ISO and exposure to get a good color that is not too bright or too dark (experiment).
You then set this image as your Custom White Balance and select it as the white balance to custom. When you take your exposures at night this will help reduce the pinkish brown color that light pollution causes and makes it easier to balance the image. (do not use a light pollution filter).
I have found this to be as good as (if not better) than light pollution filters

Regards,
Tony.

[LightningNZ]

Tony, that's only going to change the image's colour balance. That's not actually going to improve contrast at all. Light pollution filters actually block ranges of wavelengths from ever getting to the camera, so hopefully what you do get is only the signal from your object.

UHC filters tend to let through just O3 and Ha wavelengths (though they may be quite broad peaks), so a fair bit can get lost. I use a Hutech IDAS LP2 and it doesn't have all that much rejection compared to a UHC or CLS filter, it does let the reflection nebs through.

Ultimately nothing bring back a truly dark sky except for turning the lights out. :lol:

[Tony_]

I've got a Hutech IDAS LP2 also. Maybe my light pollution isn't too bad (but I think it is) but I seem to get better images when I use the white balance rather than the filter? Maybe the color balance is better and it's easier for me to process?
I guess to be sure I need to take some exposures of the same object on the same night with both methods to see which is best. It's a pity we get so few clear nights - very little time to experiment.
On the other hand, my images aren't that great so maybe it doesn't matter which method I use? :shrug: