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M31 revisited.

stan26

By stan26
in Imaging - Deep Sky

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stan26

stan26

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A wider perspective this time using my 200mm L lens, and my modded 1000D.

Final stacked image is 1hr 42min made up of 2min subs. No flats, No darks, but 200 x bias.

Guided on the trusty EQ3-2 using PHD.

My initial plan was to get around 4-5 hrs data, but weather and need for sleep have restricted me to one imaging session :mad:

Stan.

8204393317_e27c7146a2_o.jpg

Andromeda by James stannard, on Flickr

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stan26

stan26

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Awesome image Stan, i really like these wider views of M31, for no darks theres hardly any noise too and my old 1000D was well noisey, were you using a low ISO?

Thanks Jamie, these where taken at ISO1600. The individual subs are quite noisey, and although I believe my method of stacking using kappa sigma clipping mode in DSS along with at least 2-1 ratio bias to light frames helps a lot with noise, I think most of the noise and any other abberations can be dealt with in the post processing. I use photoshop CS6 to edit all my pics, and make good use of its tools in different layers to do selective editing to reduce things like noise, gradients, colour casts etc.

Cheers

Stan.

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stan26

stan26

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Thanks guys, I'm quite chuffed with the results given the relatively short exposure time, but I will be adding more data as soon as the moon/clouds go away. I want to create a big full res image of m31.....

Stan.

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cfpendock

cfpendock

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That's a fantastic image! I note that you used a modded camera. Is it this that gives so much incredible detail of the disk? or just skilled photography? I like very much the colours (including the stars). How did you achieve focus?

Cvhris

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stan26

stan26

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That's a fantastic image! I note that you used a modded camera. Is it this that gives so much incredible detail of the disk? or just skilled photography? I like very much the colours (including the stars). How did you achieve focus?

Cvhris

Hi Chris, I guess the modded camera does make a bit of a difference, it certainly does to the red response in other nebula's, but I think sub length and overall exposure time is the key to revealing the detail. personally I don't think 200mm resolves a great deal of detail in M31, I actualy pull more out using my old achro refractor, but im after overall image quality and prefer the wider FOV. Obviously is crutial to get the tracking of the target spot on and focus is very important, even more so with lens im using. When stopped down to F4 the 200L gives a very crisp flat field with excellent contast, I think that qualtiy optics makes a big difference alone, as per my sig its "just a mini APO" !!, BUT the real key to bringing out the detail is in the processing, making use of all the captued data stretching the histogram using curves/levels without pushing it too far....

As for focusing, I use a home made bahtinov mask and focus on the brightest star available. Live view comes in handy here. Some people reckon they can't focus this lens manually and have to use software to control focus, I personally have never found it a problem, just a bit of a delicated process. I also let the lens/camera cool down outside about an hour before I focus it, this way the focus won't shift with temprature change.

Cheers

Stan :smiley:

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cfpendock

cfpendock

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Thanks for the info, Stan. I agree the lens is good, and M31 is my favourite target - it seems to have everything for me, and I don't even need a telescope (except for tracking) ! But you seem to have got lots of detail - even in the core. I haven't been able to achieve that using my un-modded 550d and the same lens as you - in fact to get much detail at all I used two exposures, one for the core and another for the ring detail.

My best effort to date:

And that is why I was interested in your amazing pic! Like you, I don't find focussing a problem using live view, I've tried various masks but they don't seem to improve things. But I do find the stars sharper at F3.5 than 2.8 - I haven't tried f4 yet!

I think I need to try again with many more exposures, but I always thought this was to get rid of noise, which I don't find too much of a problem. Also lots more experience with processing......

The question is: is it worth modifying the camera? I am not sure, because I use it a lot in the daytime. In which case I just have to persevere. So many congratulations to you on having achieved such a magnificent result, and thanks again for the info.

chris

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VigdisVZ

VigdisVZ

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The question is: is it worth modifying the camera? I am not sure, because I use it a lot in the daytime.

Depends on if you want to go after certain nebulae. For some targets it's little difference, for others modding is a requirement.

There are ways to work around using a modded camera for day to day work, like white balance settings and filters, but if you're serious you might also consider using a CCD camera with different filters instead of a DSLR.

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cfpendock

cfpendock

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Depends on if you want to go after certain nebulae. For some targets it's little difference, for others modding is a requirement.

There are ways to work around using a modded camera for day to day work, like white balance settings and filters, but if you're serious you might also consider using a CCD camera with different filters instead of a DSLR.

You are right Carl. About the CCD I mean. I am quite serious, but not at all seriously rich....And the price of some of these astrophotography toys can sting.... And that is why I am so impressed when people like Stan (and others) can make such incredible images from their "semi normal" cameras. I will have to consider your suggestion of work arounds for using my camera in the daytime. I like this idea.

But I also saw Mel's image taken with an unmodded camera...

I have to say that I find these peoples skill pretty awe-inspiring!

chris

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stan26

stan26

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Thanks for the info, Stan. I agree the lens is good, and M31 is my favourite target - it seems to have everything for me, and I don't even need a telescope (except for tracking) ! But you seem to have got lots of detail - even in the core. I haven't been able to achieve that using my un-modded 550d and the same lens as you - in fact to get much detail at all I used two exposures, one for the core and another for the ring detail.

My best effort to date:

http://stargazerslou...ed-andromeda/�� And that is why I was interested in your amazing pic! Like you, I don't find focussing a problem using live view, I've tried various masks but they don't seem to improve things. But I do find the stars sharper at F3.5 than 2.8 - I haven't tried f4 yet!

I think I need to try again with many more exposures, but I always thought this was to get rid of noise, which I don't find too much of a problem. Also lots more experience with processing......

The question is: is it worth modifying the camera? I am not sure, because I use it a lot in the daytime. In which case I just have to persevere. So many congratulations to you on having achieved such a magnificent result, and thanks again for the info.

chris

Hi Chris, Looking at your image I see nothing at all wrong with it given the exposure time. More data, and I mean a lot more data will bring out more detail. For most deep sky targets I tend to aim for nothing less than a 1hour exposure time final stacked image. I usually find this rule gives the target adequate detail and structure with acceptable signal to noise, but obviously as no doubt you have read before, the more subs/exposure the better!

As for the core detail, i simply done two different edits of the same stacked image. (in short) > One i stretched the heck out off to get the outer dust lane detail, the other I only stretched a small amount and layered them together in PS. I boosted colour in various regions also using layer masks, brush tools etc. The "selective colour range" tool in PS is brilliant for selective editing of the all the stars at once. I use this tool to boost star saturation and I often (as above image) reduce the star size by 1 pixel, to help "pop" the main target through what is often I find a sea of distracting white dots.

As for modding the camera DEFINITELY worth it for some targets, not so much for others, just depends on what they are made up of. My first image with the modded 1000D was NCG7000 north american nebula. Its only 79mins but the jump red response from my unmodded 500D was incredible. You can see my north american neb here With targets such as this and things like the rosette nebula which contain lots of red (HA) the difference will be quite dramatic, but with galaxies like above I think the difference will be less noticeable...

Stan :smiley:

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