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sanmatt

A bit of helping imaging M101 please

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Hola!

With the promise of clear skies tonight (fingers crossed) I want to get out and have a bash with the new addition to my astro family of stuff. I've just picked up a Celestron CG5 GT Advanced GOTO (with power pack) from an SGL friend.

I'm hoping that a sturdier mount and goto and the ability to track will give my AP a real boost and I can try other things, as much as I enjoy star trails and lunar stuff I do want to try DSO imaging now.

So I'm thinking I'd really like to capture M101, but I dont know how to go about it.

Can you maybe glance your eyes over my kit and tell me if I am dreaming or if I can achieve this? And how should I go about it?

My idea was to use the CG mount, slew to M101 (once PA'd and done the 2 star alignment and a couple of calibration stars I think) - and I was going to just use the dslr on the mount, and leave the scope at home?

And for the spec, I was thinking of subs of 2 mins? As many as I can get, as well as darks and bias (havent managed any of the white ones yet [flats??])

Thanks Sandra

Edited by sanmatt

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Might be a bit difficult without autoguiding as M101 has quite a low surface brightness. You might want to try something thats more of a giver - M27 (dumbell) or M57 (ring) will be up later tonight, you can grab those with short exposures. You might have trouble with glare from the moon though.

With the CG5, your routine before starting will be:

1) Rough PA (centre polaris through the RA axis)

2) 2 alignment stars + 3 calibration stars (well spaced)

3) Slew to a named star near the southern meridian and close(ish) to the celestial equator (the mount will warn you if the star is unsuitable).

4) Choose "polar align" under the align menu, scroll down to "align mount".

5) Follow the instructions onscreen until complete.

6) While still on that star, focus your camera. Reason is that your focus stands less chance of slipping when using the locking screw as gravity wont be acting on your camera so much as it would if it was pointing higher up.

7) Update your alignment stars by slewing to them (using named star function), then choosing the alignment stars function under the align menu (it will ask you which one you want to overwrite).

8) Once thats done, you can update your calibration stars with the same method but I find the goto is still fairly accurate(ish) after PA - it depends on how far off you were in the first place. In fact I believe the firmware update readme says that you shouldnt need to update everything after software PA, but I do it anyway since my CCD chip isnt that big.

Hope that helps, all we need now is a bit of clear sky tonight (fingers & toes crossed!)

Rob

Edited by Uranium235

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I agree with Rob, M101 is very faint and needs a lot of imaging time - I've done nearly 2hrs with my 1100d and need more. In addition to Rob's suggestions you could try some Globular Clusters like M3 and M13 - they'll give some quick pleasing results too.

Look forward to seeing your results :hello2:

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Hi thats brill thanks Rob, I'll try one of the ones you mentioned instead. Is it the full moon that might mess me up trying to get M101 then? Is that better on a moonless night?

What is autoguiding though?

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I agree with Rob, M101 is very faint and needs a lot of imaging time - I've done nearly 2hrs with my 1100d and need more. In addition to Rob's suggestions you could try some Globular Clusters like M3 and M13 - they'll give some quick pleasing results too.

Look forward to seeing your results :hello2:

Ah so is it one of those where you'd need to leave everything set up and come back to it night afternight? Or just many many hours in total, best reserved for longer darker nights?

What sort of subs/spec should I aim for? The only ones Ive done so far is ISO800/1600 and 30s subs! Havent attempted anything longer yet!

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I shot nearly 3 hours worth of 5min subs using ISO1600 at f/5 and could have done with about double that really. Dark skies make the world of difference. Moonlight is a real pain for imaging galaxies.

ac11773b-d3aa-49ad-a7b9-f1af5e3cd89f_resized.jpg

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Yes, very nice :hello2:

Good luck with your imaging, Sandra, it's great fun but a steep learning curve :)

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It's great fun but very addictive :hello2: and only as complicated as you want it to be. If you have dark skies, a camera and a nice lens on a tracking mount with a remote timer are all you need to get great shots.

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M101 is faint so I would not attempt it unless you have lovely dark sky and no moon you could give it a bash but if your sky is not dark and the moon is out your subs will be washed out. M13 would be a good target you can do fairly short subs with that one and get good results last time I did it the subs were 36seconds long at an iso of 1600 or 800 took about 80 of those and stacked with 60 darks flats and bias shots. All unguided just a rough polar alignment as 36 second shots wont be problem. heres what you can expect with short subs unguided.

M13%2520200p%2520master%2520image%2520copy_filtered.jpg

Edited by Quatermass

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wow that is great. If I can achieve something like that then I am going to be extremely happy! I'm not expecting Hubble from my garden and my limited knowledge, just something nice.

Onoe thing I'm not so sure of is the zoom, I use the lens right open/back (?) as if capturing widefield, do you do the zooming in bit during processing?

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I dont use the zoom function on my canon 350d when taking the images any more now using backyard eos to zoom and focus with plus my bahtinov mask which is much better. But you can just put the bahtinov mask on focus roughly then zoom in to check your focused if your camera has live view should be easy. ;)

Sent from my GT-S5670 using Tapatalk 2

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M5 might be a nice object, its bright, reasonably situated, all that's required is a cloudless sky...;)

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I wouldn't go near a galaxy in any moonlight whatever...

Olly

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Must admit my first DSO target was M101 and although I was pleased to capture something for the first time, it most certainly wasnt the best choice for a first attempt considering (the usual excuse of equipment) moon was out, short exposures, LP etc

M51 was much much more productive under the same circumstances.

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Thanks all of you, much appreciated.

Well tonight it's looking promising out there, but I am feeling less than chipper at present so I'm just setting up in the garden instead of going to a dark spot. Some LP but not horrific usually, so what do you think I should have a bash at? Thanks

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If its clear have a crack at m13 in Hercules its a great subject and you can use short subs which which will mean no guiding hassles to start off with. An ISO of 800 and 60 or more subs at 45 seconds should give you good results. Stack those with 30 darks flats and bias shots should do the trick. Hope you have a lovely clear night just make sure your focus is as good as you can get it to capture the detail in the core.

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Fab thank you. So while Im waiting for it to darken to PA, Im going to start my darks - , and bias is the ones where you do the fastest shutter speed? 1/2000 I think ours does? And flats is the one with the white t shirt? hmm that might be tricky, Im not sure I have anything to do that with.

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I dont know if you have a timer on your camera but what I do is take all the main shots first after I have focused up then when I am done I put my telescope and everthing in my shed in one go leaving the camera on the telescope with the lid on. I use the remote timer set it to take 60 darks and let it do that while I go to get some kip. I take the bias and flats in the morning, bias are easy just keep the lid on the scope and take 30 fast shutter speed shots. For flats I set the camera to AV so it will adjust the exposure correctly and stretch a white t shirt over the end of the scope and point it to the outside 30 of them should be fine. Darks are crucial I find that if you do more then 30 you get a pretty smooth image 60 and above even better but past that it doesn't seem to make much difference. Have fun hope it goes really well and look forward to seeing your results. ;)

Edited by Quatermass

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For my flats, I used to leave the camera on the scope when I brought it in overnight. The next day when it was bright indoors, just popped the scope (with camera on still) onto a table facing a white wall, took some plain shots - job done.

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That's a great idea flats are not dependent on temperature like darks are so it saves time and the more subs you get of your main image that is what really matter.

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Having a right nightmare here. Cant polar align it, it wont track, polaris is whizzing across the FOV. Tried to 2 star align, cant do that either! I chose Dubhe as my 1st star and I think I got it in the polar finder, then tried in the low power EP, and couldnt work out which one it was.

;)

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