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Newb needs help with M81 process


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:mad: Hi all,

Finally got my EQ6 autoguiding the other night for the first time ever complete with my first 5minute subs! Great stuff... Only problem now is i haven't really been in the game prior to this for at least 6-12months (And then i still wasn't very good)

total of 2h35m worth of 5minute subs with darks/flat

I tried but this is all i've come up with so far which doesn't look very good at all could someone do me the favour of giving it a good ol process and tell me where im going wrong :hello2:

View image: M81 21 03 10 Stack11111111111111 Low.jpg

Here is the .TIFF file that was saved directly from DSS after it finished stacking

MEGAUPLOAD - The leading online storage and file delivery service

or

http://hotfile.com/dl/34400278/ee6890b/M81_21.03.10_Stack.TIF.html

:):headbang::icon_salut:

Just gave it another go myself, it looked ok on the monitor on the other side of the room now it looks just as bad here!

qZGli.jpg

Edited by fuuuuuu
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Hi

I to am a newbie, not sure my attempt is an improvment, i just used levels and curves within PS. I may be wrong but i think the diffraction spikes on the stars suggest you need to collimate the scope

Regards

John B

post-17074-133877435886_thumb.jpg

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I think it looks pretty nice actually... Nice round stars. Sampling well matched to pixel size... looks good.

It's pretty hard to know how 'good' your processing is without seeing the raw data to compare. However, I certainly can't see any major problems/mistakes. No big gradients (you can see where the flat field correction has worked by the increased noise in the top right of the image) or hot pixels. I assume the raw image is quite vignetted?? (brighter in the middle than the edges). Just looks like it needed a bit more exposure time to beat down the background noise..

I prefer the version you put up first (linked), where you could see a bit of noise in the background; but that's the type of image I'm used to looking at.

What is the telescope? I'm assuming it is a Newtonian with four spider vanes from the diffraction spikes? Nothing (that I can see) to indicate there is any problem with the collimation...

What is the camera??

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Cheers guys didnt know about the collimation thing tbh its never been done!

The scope is a 150PL sky watcher and the camera is a 350D modded to clear glass,

So you think longer exposure? Should i be aiming for 10minute subs? Little disheartening when there my first 5minute subs yet the result doesnt seem to be much better then when i was using 60second subs :)

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Cheers guys didnt know about the collimation thing tbh its never been done!

Wouldn't worry about it at this stage. Doesn't seem to be affecting anything here

The scope is a 150PL sky watcher and the camera is a 350D modded to clear glass,

So you think longer exposure? Should i be aiming for 10minute subs? Little disheartening when there my first 5minute subs yet the result doesnt seem to be much better then when i was using 60second subs :)

Hmmm. Bit odd. I would expect you to be getting deeper than that in 2.5 hours. It should certainly look better than a 60s sub. That does suggest something is going amiss in the processing.

What steps did you take? What algorithm are you using to stack the images? I'm afraid I don't know the details of DSS though.

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I just used the standard settings for stacking in dss, saved the output as 16bit tiff when Im trying to process in ps cs3 I notice the histogram is always very small and after I make a few adjustments the histogram scatters and I end up with barely one at all(just a few very spread out lines)

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I'm afraid I don't know anything about DSS, so can't help you with that bit.

I would suggest you try to process a single 5 minute frame (i.e. don't stack anything), and compare that result to the stacked image. Clearly the stacked image should be a lot better with a lot less noise in the background. If it isn't; somethings going wrong in the stacking. What, I can't say as I don't know the software...

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What software are you using/recommend?

I use IRAF... you don't even want to consider going there :) I process images from a scientific point of view; not very often from a pretty picture point of view. So, I don't know much about things like levels/curves/etc -- but I do understand the basic processing steps and various combining algorithms.

Aesthetically, your image looks very good to me. But when you said you thought it was comparable to a single 60 second sub; that made me think there is probably something going wrong with the combining step. That's why I suggest processing a single frame, and seeing what you get.

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