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tmarkuk

M13 First attempt at a glob

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Thanks for all the kind comments regarding my first DSO attempt on M51 in my previous thread, it gave me a real boost in confidence to go out and try something else! So last night whilst I happened to be up late I popped my head out and saw the skies had cleared and they kindly stayed that way all night. I thought I'd have a go at a globular and M13 was well positioned.

m13_final_2.jpg

I also managed to pick up NGC6207 which was a bonus and a satellite which I guess I should remove but kind of like for added interest.

This image is composed of :

20 x 1.5 minute light frames

20 x 1.5 minute dark frames

20 light frames using the home made light box (made since my last session).

20 dark bias frames.

Taken with :

Canon EOS 1000D unmodified at prime focus

Orion Options 250mm F4.8 Reflector

Skywatcher Light Pollution filter

Vixen Sphinx SX Mount

3 cups of tea.

I'm still learning, but I think it came out OK. Reducing noise is going to have to be my next goal. Any comments and advice greatly appreciated.

edit... One day I'll post an image here and get it right first time...

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I think it came out OK as well.

Well done.

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Very nice...

When i tried M13 last week i wanted to try and resolve the stars down to the core and also bring out the feature known as the propellor so I addopted a similar HDR approach to the one i use on other targets that have very bright parts...

I take a range of exposure lenghts and then stack them before combining the layers in CS3. I have the shorter length subs at the top of the stack which only records the brighter stars at the center of the cluster...

Peter...

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That sounds like a plan, I may have to try and get some shorter subs the next time the weather allows and see if I can achieve a similar effect. I also really need to work out how to get the clean black back ground without losing to much detail. Always something new to learn, is what makes this so enjoyable.

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Have a look at an individual sub from the ones you already have... you might be able to use a shorter stack instead of getting new data if the center stars are resolved in it...

Layer this on top of the existing image and adjust the opacity... you might want to delete everything outside the core of this new layer as the outer regions and the background satrfiled are spot on...do this witha generous "feathered" edgle to avoide any obvious "joins"

Peter...

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Thanks for the link and recommendation, I'll definitely add an MPCC to the shopping list.

I'll have a go with your tutorial this evening and see if I can produce something a bit better.

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That is excellent - you've got some great data in that image, and a lovely field of view for M13.

To reduce noise, stack more :icon_rolleyes: Try using a sigma clip algorithm for your stacking as well - it'll get rid of the satellite trail immediately.

As Aza says, you will probably find that using an 'S' shaped curve will allow you stretch the edge without blowing out the core - this is a useful skill in astro-imaging, and M13 is a good target to learn on.

You could also play with Billy's method as well by taking a copy of the stacked image before you've stretched and overlaying one from afterwards and 'rubbing through' to the non-blown-out image in the centre - you have to do it very carefully though, so its not obvious.

Coma Corrector - absolutely - it is the only way to image without coma in a Newtonian design - the Baader MPCC is the one to grab.

Cheers,

Richie

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If my first attempt at a 'glob' had turned out like that, I'd have been well chuffed. :icon_rolleyes:

Well done!!

Dave

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That is a very good Glob and I love the Fuzzy with it, I must look for that one myself. Nice Star colours as well.

I tried it the other night and I know its very low and will be better to image later on in the month. Try it again, stack more and try not to overexpose the core. Before I guided I took many subs at a lower exposure ( about 100 at 30 secs) to protect the core and it worked.

Robin

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Just to say I wasn't trying to be mean, just trying to help!

Yes, I'd love my first attempt at a glob to come out like that - as it was, here is my first attempt at a glob - just happens to be M13!

post-14845-133877370819_thumb.jpg

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At a guess I'd say you have good information there, enough to improve the end result possibly without resorting to combining different length exposures. Seems to me you have overstretched the whole thing so the brighter stars have gone very bright along with the core. When using Levels don't move the white point and when using curves don't let the curve hit the top of the box to the left of the top RH corner. Hope that makes sense. Also set the background to around 15% brightness in PS, not too dark as it never loooks right.

I'm not showing you my first M13, 'nuff said!

Dennis

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I had another go with the processing this evening, I'm certainly happier with some aspects of it, but not others.

m13.jpg

I shall have to get out again another night and try again with a lot more subs I think.

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This is one of the targets where you have to treat different parts of the image differently. To get the background starfield and other "fuzzies" you need to stack lots of long subs but this will totatly burn out the core of M13 which requires shorter subs to resolve the stars and "propellor".

You'll soon know if you have the "information" there by looking at a single sub and see what the core of the cluster looks like...

Peter....

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I think there is a lot of data in there. How about posting the raw stacked file so we can have a go at processing. I have only done one glob, and that was a year ago, so I would like to have a play :icon_rolleyes:

If you wanted to upload it, you can use www.mediafire.com to host ;)

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That's a great first glob and certainly one to be proud of, they're not easy objects to image and you've made a very good job of it.

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Hi

Just tried to download the file, but it seems to be invalid!

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A brilliant first go at M13.

The use of DDP ( digital development processing) brings out the central stars.

You do need a program like ImagesPlus , MaximDL etc that has DDP.

Below shows one of my images that had DDP.

John

post-13061-133877371135_thumb.jpg

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Sorry the file does work :icon_rolleyes:

I guess it had not finished uploading when I tried it.

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Not sure what's wrong there Arran, I've downloaded the file on two PCs and both have been able to extract the files and open them, in photoshop and gimp. What error are you getting?

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I have given your tif a process, and I think your data is pretty good.

Your exposure lengths are fine, but you do need more of them!

What ISO did you use? You may have gone too high with that.

Also how do you focus? I would suggest you make a Bahtinov mask ASAP :icon_rolleyes:

m13s.jpg

m13crop.jpg

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I love the M13, one of the first messiers I tried photographing, I was well chuffed when I actually got some resemblence after just two timed shots. I think there is always enough in there to bring something out.

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I have given your tif a process, and I think your data is pretty good.

Your exposure lengths are fine, but you do need more of them!

What ISO did you use? You may have gone too high with that.

Also how do you focus? I would suggest you make a Bahtinov mask ASAP :icon_rolleyes:

Those look great, thanks for that! The ISO was 800, I shall try a lower setting next time I try a globular. My previous M51 image was taken at ISO 1600 so I went with the next step down for this session.

I made a Bahtinov mask a while back, though I think the star I focussed on was far to dim as it was very difficult to see the spikes and I guess I ended up slightly off focus. For my last image I used a far brighter star and they stood out much better, I'll have to make sure I spend more time checking it next time.

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If your ISO was 800 you could go down to 400 for these really bright globs. But also when I looked back at my M13 I used 60 second subs. So maybe try some at that length too.

Focus is key, but also maybe there is a bit of trailing in this image too.

To get the best polar alignment I can, I use this method, along with a reticuled eyepiece:

Tim & Becky's Deep Space Imaging Page

Takes a little while to get your head round it, but its easy really. I always use this when setting up.

I must say your images are really good for a beginner! Keep it up :icon_rolleyes:

And keep practising processing, that helps make all the difference too.

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