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I went for 100 subs last night with 30 darks and bias. Exposures of 1 minute each - no flats but Ill do them later and equipment as per my sig. I was a bit disappointed as I had better results with less shots but longer exposures. I though more data would be better? Will the flats make a difference? Or is it processing?

Thanks,

Stevepost-44244-0-39830400-1444623022_thumb.j

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Processing will bring out more detail but also highlight all the vignetting which is where the flats will come into play.

It looks like the basis of a nice image.

There is some subtle aberration of the stars at all four corners: not sure if this is coma or a non-flat field, others will hopefully be able to advise.

Don't be disheartened, M31 is hard; not only is it so big, but the core of it is so bright and its arms very faint.

James

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M31 is tricky. I never managed to get satisfactory results with short exposures with my 200p on my old EQ5 mount. I could bring up the faint regions by stretching the levels, but only at the expense of unacceptable levels of noise. I did rather better with longer exposures (5minutes) guided on my AZ-EQ6 even though the total length of exposures wasn't much longer. Some people recommend taking combining two sets of data, one set with shortish exposures to capture the core and one set of long exposures to capture the faint outer regions of the galaxy. Personally I think M31 is a bit big for the 200p and prefer images of M31 capturing the whole galaxy taken with longer focal length telescopes. As mentioned by Jambouk the stretched stars towards the corners of the image look exactly like the coma I see with my 200p.

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It's almost impossible to tell on this darn phone but have you clipped the faint data off by adjusting the background so it appears dark?

For me M31 has a lot of stars and there is no black background space, it appears foggy.

I don't think M31 is difficult at all to get an ok image, much like M27, it's a good target to start. I do think it's more difficult to get it right when blending together the bright and faint areas.

Sent from my SM-N9005 using Tapatalk

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How did you get all of the galaxy in your field of view. I have the same set up as you but in the fov calculator on the web it shows andromeda as far to big to get in the fov although you seem to have managed it ?

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For faint stuff like Andromeda's arms, you need longer exposures. With short exposures you're capturing only a small number of photons so the detail's less. No amount of stacking will add detail I'm afraid! That's a nice capture with what you've got, though. 

Alexxx

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How did you get all of the galaxy in your field of view. I have the same set up as you but in the fov calculator on the web it shows andromeda as far to big to get in the fov although you seem to have managed it ?

I think it's just the core. The satellite galaxy in the image is M32. That's why Stevie feels so disappointed with his image. The galaxy should almost fill the whole image at this focal length.

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With short exposures you're capturing only a small number of photons so the detail's less. No amount of stacking will add detail I'm afraid!

Not so - the detail should eventually appear if you stack - you just might have to have a total exposure time somewhat longer than if you take longer subs.

However there is something odd going on - 100x1 min should get you a stunning image with that equipment.  Your image looks more like a single sub.

NigelM

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Relating to your initial query, I also find that shorter subs give less data/detail, even if the total integration time is more. An hour of 5 min subs gives me a better image than an hour of 90 second subs. I think it depends on all sorts of factors like light pollution, equipment etc and may be different for others. It's just what I have found for me in my location...

You might end up with a less noisy image though. Your image looks good to me and a skilled processor (not me!) would, I am sure, extract some more detail from it. Tim 

postscript....just had a little play with your jpg. Looks like you have clipped the black point during stretching. Have another go and leave the white point alone!

Edited by StargeezerTim
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I went for 100 subs last night with 30 darks and bias. Exposures of 1 minute each - no flats but Ill do them later and equipment as per my sig. I was a bit disappointed as I had better results with less shots but longer exposures. I though more data would be better? Will the flats make a difference? Or is it processing?

Thanks,

Steveattachicon.gifAndromeda 11 Oct Jpeg.jpg

Will depend on your scope and ISO setting as well as exposure time but assuming ISO 800-1600 I would have expected more detail then you show. I realise my setup is different but this is one taken on 9/10 100 x 30 sec @ ISO1600. Non-modified Canon 600D. It is definitely not my best but is more what I would have expected to see.

I don't find it easy to prise out the detail in M31 during post processing perhaps because of the short subs, but keep experimenting until I can't get any more or I am pleased with the result. On this one I did go for a blackish background but as stated above it really isn't that dark. 

post-34685-0-23784400-1444658683_thumb.j

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I've experienced this problem all too often with most DSOs, but M31 is probably the most affected. The level of light pollution is great enough to wash out all of the dim outer edged of the galaxy. Because the two are similar colours, it makes it even more difficult to extract, which it appears you tried to do, and in the process, clipped out the galaxy with too harsh use of the black point. The gradient in the photo doesn't help, either.

Possible solutions are: flats, and/or GradientXTerminator, to remove the gradient, and moving away from light pollution (or getting a filter). I'm sorry to say that longer exposures, although they get more data from the galaxy, also get more data from the light pollution - so your job getting an image of the outer arms will be made little easier.

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Will depend on your scope and ISO setting as well as exposure time but assuming ISO 800-1600 I would have expected more detail then you show. I realise my setup is different but this is one taken on 9/10 100 x 30 sec @ ISO1600. Non-modified Canon 600D. It is definitely not my best but is more what I would have expected to see.

I don't find it easy to prise out the detail in M31 during post processing perhaps because of the short subs, but keep experimenting until I can't get any more or I am pleased with the result. On this one I did go for a blackish background but as stated above it really isn't that dark. 

attachicon.gifM3109102015cas2cpp6B.jpg

Wow! 30s?? I've been put in my place! :grin:

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I'm going to try again tonight, any suggestions for the camera settings - maybe ISO 1600 and shorter subs. I can't really go too long as I'm not guiding.

Thanks.

As yours is an F5 scope compared to my f6.3, I see no reason to change from what I said above. 100 x 30 secs should give you some detail in the outer regions. Neither of us are going to match the quality and detail of a guided scope and modded camera or CCD but I still think it's worth doing. If you can go to 45 secs without oblong stars, try a few at that also. As has been said don't try to darken the sky too much in post processing it really isn't all that dark when you look at it.

Good luck.

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Certainly looks better, well done. Can I suggest that before stacking you look at each frame and delete any that have out of round stars or other aberrations as they will have a detrimental effect on the end stack.

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Yes, looking better.

Flat frames are more important than the dark ones, mostly as they reduce the vignetting. Bit you really need to take a set of flats each time you image, unless you are not adjusting the focus or moving the camera in any way between sessions.

Great stuff.

James

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