Saturday, October 10, 2015

#16 - Saturday, October 10, 2015 - I Need More Dumbbell

I focused on just one object tonight, since we didn’t get out there and set up until about 10 PM and it was cold: the Dumbbell Nebula again.  This time, it turned out rather well!  But the accepted frames ratio was terrible: out of the 125 I took, I only deemed 23 to be good, and DSS only took 18.  At 30s apiece, that’s 9 minutes total.  But, the sky was fairly dark, and it was high in the sky, so it turned out rather well.  It was also cold, which reduced camera noise, and it was subtracted easily by DSS.  Also, my alignment must have been pretty decent, since the nebula stayed in nearly the exact same position for most of the time.  
M27 Dumbbell Nebula
Nikon D3100 on the C8
18x30s, ISO-3200
[Author's Note: Wow, my definition of "rather well" has definitely changed!]

I’m quickly hitting the limit of what I can do, though.  18/125 photos is awful.  And it was at 250° azimuth and 50-60° altitude, so no problem at all with high field rotation.  It’s just periodic tracking error.  I really need a wedge :/

Monday, October 5, 2015

#15 - Monday, October 5, 2015 - Finally, some not-so-bad images!

What luck to get two nights in a row of mostly clear skies.  It was humid though, and it had been warm that day and was still kind of warm, so the visibility was pretty poor.  The sky was even brighter than it was on Sunday night.  (Actually, most of the sky was pretty dark on Sunday night).  This was my friend Jared’s first time looking through a telescope, and he was thoroughly impressed.  We caught Saturn just before it set, so it wasn’t very clear, but you could still see it reasonably well with the 13mm eyepiece.  We also looked at the Andromeda galaxy, a few clusters including Hercules, Butterfly and Double, and double star Mizar and Alcor in the Big Dipper, which is now mostly behind the trees to the northwest.  There were a bunch of persistent and spread-out airplane contrails, along with a few other high-altitude clouds, which made the visibility even worse, so finding a suitable object for photography was difficult.  I tried the Omega Nebula, but didn’t get many pictures before it wound up behind a cloud.  I only got four good ones (again, cable got jiggled and several were turned into JPEGs), which stacked reasonably well, but is also grainy and dim.  This one is a promising target – I have another version where I increased the luminosity, and you can see even more of it, and it’s quite pretty – but it’s close to setting, and it’s in the southwest where all the light is, so this might have to wait until next year.
M17 Swan Nebula - you can really see the swan here!
Nikon D3100 on my C8, 4x20s, ISO-3200

After having to give up on the Omega Nebula, I couldn’t find any other nebulae that were a) bright enough, b) high enough in the sky, and c) not too high in the sky.  It seemed like everything was either between 10-15° or above 70° [above the horizon].  On the other hand, if I can go out on another weekend night before it gets too cold, the North America nebula is starting to get low enough in the sky on toward midnight or 1 AM that I could try to image part of it – it’s huge!  Also, the Orion nebula is now rising at about 12:30 AM, so if I can go next weekend, I won’t be able to start imaging it until about 1:30 AM, when it’ll be closer to 20° high.  But it is very bright - +4 magnitude – so maybe like 60 or 70 images will make something good.  We’ll see.  Also, for the record, Stellarium is a fabulous app for planning!  Other things to try include the Eagle Nebula, which I haven’t tried yet because during the summer it was too high, but now that it’s lower, I took a 30-second single exposure just to see if I’ll be able to see it, and I can’t see really any gas at all.  On others like the Omega, Lagoon and Dumbbell Nebulae, the gas is apparent even in a single exposure.  So I’m not sure I can take long-enough pictures of it to be able to get anything worthwhile.  That one might have to wait until I get a focal reducer. 
After giving up on the Omega, I ended up just imaging the Double Cluster, which looks nice in the telescope, but star clusters don’t make for great photographs, at least I haven’t been able to do very well.  There is very little color information; the RGB curves are nearly delta spikes. [As it turns out, you want the RGB curves to be narrow spikes in your RAW images].  So this was 17 images (out of 57 originals) taken of the Double Cluster, or, at least, half of the cluster.  It’s pretty large, apparently.
Part of the Double Cluster, taken with my Nikon D3100 on the C8.
17x20s, ISO-3200

Sunday, October 4, 2015

#14 - Sunday, October 4, 2015 - Persist!

The long break was because I was gone for over half of September on work trips, and before that I was busy and the weather wasn’t good.  

I took some 220 pictures of the Dumbbell Nebula, but several things were not in my favor.
·         All of the good nebulae – Omega, Trifid, Lagoon, Eagle, etc. – are setting pretty early now, and since that puts them in the southwest, the direction of the town or city that is causing all the light in that part of the sky, imaging them yields not-very-good results. 
·         The camera cable got jiggled at some point, so over half the pictures were in JPEG before I realized it and reset that setting back to raw.  (The camera-control program I was using, digiCamControl, automatically sets the image to JPEG every time the camera is plugged in.  And no, I can’t edit the default settings.)
·         The Dumbbell Nebula was pretty high in the sky, up in the 60°-altitude range (part of the reason I picked it – somewhat less light and much less atmosphere), but that gets into the range where the tracking is poor for alt-az mounts.  So not only did it drift a lot, but the majority of the photos wad periodic tracking error.  So, out of 220, only 7 came out, since many were lost to JPEG and the rest to periodic error.

The picture didn’t turn out too badly, actually.  It is pretty grainy though.  And, of course, I always want more light.
M27 Dumbbell Nebula
Nikon D3100 on my C8, 7x30s, ISO-3200