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Andromeda Final..


Simms

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Well, I think this is about as much as I can tease out of M31 for the timebeing - maybe if the local council kills the lights after 12am like they say they are going to I might revisit and add some more - but I live in a very populated area of Basildon and as a result the light pollution is pretty dire.. But I persevered and I am very happy with my final result - considering I have only owned a scope since January and only been imaging a short while. Its made me very eager to get to a decent dark sky site.. Anyway, enough waffling.

post-23171-133877642878_thumb.jpg

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From Basildon I have to say I'm impressed!!

Did you take flats? I suspect you could pull down the background sky a little.

Olly

Cheers Olly, I bet it makes you want to shut up shop and move to Basildon! ;)

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An image to envy. But perhaps you should crop the right of the image slightly - there seems to be a line running down it - it looks a bit like a paper crease.

It's nice to know that such good images can be made from urban locations. What camera settings di you use? Were you using an LP filter?

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Hi Guys, sorry about the lack of info.. The `line` or `paper` crease seems to be where two images overlapped - I shot this over several weeks (an hour or so each time) and on the last attempt I wasn't lined up quite the same way - DSS took care of the lining up, but didn't seem to crop out the extraneous parts of the misaligned image.

Shot with DSLR (Canon 1Dmk3) on a SW 200pds with HEQ5 - guided with a webcam/finder-scope combo using PHD. Sub times and ISOs etc vary from session to session as I am always experimenting to find the sweet spot between noise and photons captured - I would say the lions share of subs were 300secs at iso320. I also used a SW LP filter and a Baader MPCC (coma corrector). I can dig out the exact number of subs and times/isos if anyone is really interested.

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It looks to me like you didn't use flats and I really would recommend that you try it. It's a hassle but worth it, honestly.

Olly

So Olly, explain the flats - are these the short exposures that show the vignetting of the scope/camera and then subtract that info from the final image? DO they need to be shot at the same ISO as the Subs? Do they have to be over-exposed/under-exposed (under exposing shows off the vignetting more in my experience)..

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Flats; what must not change from the image frames is the orientation of the camera in the scope and the focus. This means you can take off the whole scope-camera assembly as one, if you like, and do them inside. Or you can try 'sky flats.'

You need to contrive an even, flat white light over the objective. Electroluminescent panels, computer screens or white T shirts stretched over the OTA all work for some people. I use a panel but they are costly in large sizes.

Take fifty exposures at an exposure time that gets you between a third and two thirds of the way up the histogram. I think most DSLRs will show a histogram on screen. The peak is what you're looking at.

Take fifty or more bias frames, the shortest you camera can take.

The bias can be considered as 'darks for flats' because dedicated darks for flats would be indistinguishable statistically.

This produces your flat field, which will be disgustingly far from flat!! The middle of the image will be bright and the whople thing covered with loathsome dark blobs. The stacking software will then make corrections to your image, brightening or dimming it in the light of what it reads on your flat.

Olly

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Flats; what must not change from the image frames is the orientation of the camera in the scope and the focus. This means you can take off the whole scope-camera assembly as one, if you like, and do them inside. Or you can try 'sky flats.'

You need to contrive an even, flat white light over the objective. Electroluminescent panels, computer screens or white T shirts stretched over the OTA all work for some people. I use a panel but they are costly in large sizes.

Take fifty exposures at an exposure time that gets you between a third and two thirds of the way up the histogram. I think most DSLRs will show a histogram on screen. The peak is what you're looking at.

Take fifty or more bias frames, the shortest you camera can take.

The bias can be considered as 'darks for flats' because dedicated darks for flats would be indistinguishable statistically.

This produces your flat field, which will be disgustingly far from flat!! The middle of the image will be bright and the whople thing covered with loathsome dark blobs. The stacking software will then make corrections to your image, brightening or dimming it in the light of what it reads on your flat.

Olly

OK, so maybe I can achieve these post sub capture as I usually put my DSLR on in the exactly same orientation (so I can always go back to a subject later on) and obviously focus will be raltively easy to achieve.. You`ve explained this really well Olly, thanks for taking the time out to do this - I`ll have a crack at it over the following week and reprocess my image.. Thanks for your time!

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