Double Cluster

[Jannis]

Ok, so, I just got home from work, had around 3 hours before bedtime (wich was 2 hours ago now anyway, but.. ), and i wanted to try to capture something new. BUT, mother nature would let me go that easily...

Well, as usual, it all started nice. Clear weather, no wind and so on..

But then, moon just had to be in the position where i wanted to image, so, had to chamge. Ok i thought, double cluster instead!

Well, after calibrating PHD (wich took a millenium as i use a webcam and a 200mm guidescope), i started to take pictures. Seemd fine. But then... Clouda came over as i was imagine, and, you guessed it, PHD lost track and started guiding all over the place. So, had to turn PHD off. As it was only thin clouds, i'm too stubborn to let that stop me.

So i lowerd my subs to 20 sec and increased ISO to 800. Worked fine, for teh first 40 frames.. Then, miss wind came by to say hello, and PHD wasn't even needed anymore now to make sure the stars went all over the place... So, finally, i agve up, and decided to put on the scope cap and take teh darks and go inside..

After a few darks, i realiced my previous issuie was still there, and orange glow. Thinking this was too bright to be sensor noice, i mooved my scope away from teh street light, and sure enough, now the orange glow was somewhere else..

Turns out scope cap isn't really enough for darks as it's too bright around where i am (= 5 meters away from a street lamp). So, had to give up this also, and skip the darks...

So i packed down everything and went inside, and just when i came out to get teh tripod, being teh last part, there was no wind, and barly any clouds... --.--

Well, ok, so here it is:

Double Cluster taken with unmodded 550D. 42x 20s ISO800. No darks, flats, bias or anything else that everyone else would normally add.. lol.

Stacked in DSS, and preocessed quickly in PS.

Oh yeah, and just to add, it seems my scope have collimation issues as i have very egg shapes stars everywhere exept in the middle? I know focuse is good, wich i previously though was the issue, as i just got to try my new lazer cut bahtinov mask.

Wich i, also for no aperant reason, adds a pic of..

[Shibby]

Well captured Jannis, particularly considering only 20s subs! By the way, that's the best diffraction pattern I've ever seen, no mistaking the focus with that is there

The star shapes will be due to coma, I assume you have a Newtonian. PS lens correction can help to some extent.

[jgs001]

Nice result. Nice looking mask too. The egg shaped stars, probably best to get an MPCC or the SW Coma Corrector to sort that out. The lens correction tools in PS will deal with it, but you lose some of the edges in doing so.

[Jannis]

I'm mostly pleased with the result, considering all the problems there was with taking it. I would really have liked smaller and more clear stars though. But i guess it's only that much details you can get from 14min exposure at ISO 800 without guiding.

Thanks for feedback on coma. I don't have any coma corrector, and haven't used any lens corrector in PS. I'll give it a try.

So it may be that my scope don't really need to be collimated, just ahve a coma corrector, or use corrector in PS (any difference in result from these two, btw?)?

I don't yet have a collimation lazer, and haven't collimated my scope at all. It's just like it was when unpacked and put together.

The mask works like a dream indeed. No dubting the focuse any more. Also made a small one for the finderscope, but cuts are a bit unclear as the lazer machine had slight problems cutting 0,6mm wide lines without melthing the 1mm thick stainless steel, so it's a bit uneven, but i think it will still work well. Main mask was made in 3mm stainless steel, so a bit veavy, but no problem for just focusing. And what a result, comparing to my quickly homemade version made from foam!

I can strongly recommend this for everyone.

[Jannis]

Just wondering, i tried lens correction in PS, and got stars a mor more round, but still not perfect. however, when i had set it so that stars was looking OK around on the sides, the middle part looked rather unclear and blurry. Is this normal, or am i messiun up some settings somewhere?

Is there a specific settings i should use for the 200 PDS with canon 550D, or do i just need to try and see what looks best?