Image issues.

[peeb61 (Paul)]

Folks,

As mentioned before in a previous post, my polar alignment was out and Polemaster arrives today.

Doing a couple of test runs last night I ended up with this image of M20, just a short exposure set with no bias, darks or flats yet and a quick process in Photoshop.

I'm thinking the bright area is street lights? Not apparent in the original subs.

Paul

Many thanks in advance.

[glend (Glen)]

That gradient light becomes additive as you stack more subs. You do need bias and darks at the very least. I suggest you shoot some of those and reprocess in DSS, it will look much better imho. Take the time to build a bias and dark library for your camera.

[peeb61 (Paul)]

Thanks Glen for you input, the darks, bias and flats are on the cards for sure, I also had camera flop and ended up with out of focus stars in one corner, looking at this image I can see this now has almost been eliminated and hence found this other issue with the gradient.

Small steps eh?

I do have a roundabout with lights just over the fence at the corner of my street, probably from there.

When I am serious and ready to go, the screens will go up to block out all of this LP.

Thanks again Glen.

Paul

[JA]

Originally Posted by peeb61

Folks,

As mentioned before in a previous post, my polar alignment was out and Polemaster arrives today.

Doing a couple of test runs last night I ended up with this image of M20, just a short exposure set with no bias, darks or flats yet and a quick process in Photoshop.

I'm thinking the bright area is street lights? Not apparent in the original subs.

Paul

Many thanks in advance.

Anything is possible, and it's odd that it may not have shown up (or possibly may have not shown up enough) in your subs, but there's a whole lot of other stuff going around there that may contribute. Refer attached composite image of your M20 image rotated and resized to suit a comparison with another wider field image (grabbed from google images with attribution) of M8 and M20 which shows similar but not identical light brownish nebulosity/gas/light between M8 and M20.

Who knows? If you suspect extraneous light try another location away from potential sources or a long "lens hood"

Best
JA

[peeb61 (Paul)]

Thanks JA,

Couldn't find the attachment! Would love to see it.

Paul

[JA]

Originally Posted by peeb61

Thanks JA,

Couldn't find the attachment! Would love to see it.

Paul

It wouldn't load originally. It's now loaded

Best
JA

[Startrek (Martin)]

That’s a really nice M20
Great work
Yes artificial light especially from street lights can makes things difficult when imaging
When I image in suburban Sydney ( Bortle 8 skies) I use poly tarps from Bunnings to try an eliminate the glare from both neighbours outside lights which for some unknown reason stay on all night ( my exterior lights are all on sensors, don’t know why theirs are not and both homes are modern only a few years old , mines 70 years old )
The tarps make a huge difference and only take me 10 minutes to hang up and tie off
Also maybe try a light baffle

[peeb61 (Paul)]

Thanks Martin, it's really down to you! You put me on the right track with USB to Com cable!!...it hasn't missed a connection once since I got it!

The image is only 3 x 3minutes and only a tester. Hopefully I can achieve more once all of my issues are ironed out.

The tarps sound like a good idea, simple and easy the way I like. I have flat black ply boards which I wing nut into the upper walls to block out the street lights and have bought a dew shield for the long runs.

Thanks for your words.

Paul

[peeb61 (Paul)]

Originally Posted by JA

It wouldn't load originally. It's now loaded

Best
JA

JA, I really see what you mean now and you have me wondering, food for thought, thanks for taking the time to put it all together to show me the "light!"

A really good example.

Paul

[sil (Steve)]

Physical blocking is good but won't remove it. Its light pollution and will remain there in the sky reflecting back very very faintly from dust and moisture as that orange brown A look into a good light polution filter could be in your future, at the cost of loss of photons as with any filter. Gradient removing the pollution though is very effective so depending on your location and workflow you might be fine with capturing it or prefer to fiilter it optically . Astronomy provides many paths to travel to throw away that pesky money

[peeb61 (Paul)]

Originally Posted by sil

Physical blocking is good but won't remove it. Its light pollution and will remain there in the sky reflecting back very very faintly from dust and moisture as that orange brown A look into a good light polution filter could be in your future, at the cost of loss of photons as with any filter. Gradient removing the pollution though is very effective so depending on your location and workflow you might be fine with capturing it or prefer to fiilter it optically . Astronomy provides many paths to travel to throw away that pesky money

Thanks Steve, I was thinking along the lines of LP given the fact as I mentioned I live on the corner near a large roundabout with 3x whooper orange lights pointing down along with a foot path light...the challenge is on!

Paul

[The_bluester (Paul)]

Another tactic if you have a gradient (Particularly in the eastern or western sky) is to limit the area you capture in either side of the meridian. It does however also limit your available capture time per target each night.

I know of some people with permanent setups that restrict imaging to about 30 degrees each side of the meridian to get both the best seeing (Least atmosphere to transit) and the least chance of gradients from light pollution. You can really see that from my place. I am lucky in that I live in a fairly dark area but if I image to the east below about 40 degrees then a gradient from nearby Kilmore starts to show up and likewise to the South the light pollution of Melbourne begins to rear it's head.

I am looking forward to an astro camp later in the year to image some stuff around the pole that suffers from the light pollution at home. I might be able to combat it with filters to a fair degree per Steve's suggestion, but I have plenty of sky to image so I will just save the southern stuff for astro camps.

[peeb61 (Paul)]

Thanks Paul,
Gotcha! See what you mean.

Paul