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Old 30-10-2013, 05:08 PM
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Rex
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Join Date: Jun 2010
Location: Townsville, Australia
Posts: 991
Quote:
Originally Posted by alistairsam View Post
Hi Rex,

Looks very good, lots of detail in there.
I see you've used the CLS LP filter but with an F4, 10 minute exposures gather a lot of LP even with the best filter and after 4 minutes, there's not much gain in signal. its the brown tinge.
I used to use an 8" F4 and have played around a bit with an IDAS LPS-P2 LP filter. so tested different exposure lengths for the same target and realized that the details in a 10min aren't that different from a 5 minute which is only slightly better than a 3 min.

you can easily remove it with processing software like Startools and PI, attached is a quick wipe in startools.

I'd suggest keeping your subs to 3 to 5 minutes and increasing the number of subs.
That would help reduce LP showing up.

Do experiment if you get the chance.
try 10x3 min exposures and then 6 x 5min and compare. well worth it.
or even single subs.

your guiding and coma correction are perfect.

Cheers
Alistair
Thanks Alistiar, some very interesting information. Fortunately for me, the brown in this case comes from my poor processing skills, I think. I only use the CLS-CCD clip filter because where I used to live a couple of years ago I needed it. Where I live now is not perfectly dark but pretty good. M31 is easily visible naked eye, averted vision it is very visible. Thats not to say that LP hasn't played a role in the way this image looked. Just as I finished processing it, I thought it was too red, so I did a selective colour adjustment to change the reds. This is where the orange and brown came from. I have attached the same image to the first post from before I did that final colour adjustment. Please feel free to tell me I am wrong and that you still see LP, as I am really only just starting my astroimaging journey. My processing skills are so good I can make an image look like it is LP affected.

Quote:
Originally Posted by JZ View Post
Another nice shot Rex. Alistair has some interesting comments!
Interesting to see what startools can do too.
I have certainly learned from this!

Cheers,
Ross...
Thanks Ross.
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