Nov 10: More M27, start 2 new targets

Tonight looks like a repeat of last night – the sky is clear and the CSC says excellent transparency all night. I’ve opened the dome at 7:30 PM, and am taking another 2 hours of M27 in 15-minute subs, to add to the data collected the last couple of nights.

I just noticed that for the first 500 seconds of the first 900-second sub, I forgot to turn PEC on. It was still guided, but more correction needed than I would have liked. So I may end up discarding this first sub – we’ll see how it turns out. The other 1.75 hours will be PEC-corrected in any case.
Sure enough, in post-processing Maxim recommended discarding the first sub (and another) for poor star-roundness, so I went along with this. The result, with 4.5 hours of data, is starting to look nice – detail in the outer gas envelope is beginning to show well.

Pleased with that and still looking at a nice clear sky, I tried an initial take of M74, which is well positioned above the roofs and hedge. I captured a little less than an hour of this, stopping when I hit the tracking limit on the West side of the mount. A quick look in post-processing the following day tells me I don’t have enough data yet to put up a first draft image that I’d be happy with, so I’m just keeping these subs to be added to later.

2010-11-10-NGC2003-2Next, a completely new target for me: NGC 2403, high in the North. The catalogues show this as a fairly large and very pretty spiral, and it’s well positioned for my viewing location. It’s a bit high and may be blocked by edge of the dome cover before too long (next summer: build a PZT to roll the cover off). Having refocused, I took a fresh set of flats, then 4 x 15-minute subs.

Unfortunately, 2 of the 4 subs have a satellite trail through them. This will probably average out in stacking, but leaves me with only 2 really good ones for now. So, again, I’m not putting up a processed image yet; more data gathering first. Here’s a quick view, though.

Am I right in thinking that targets near Celestial North will have a higher probability of having satellites pass through? (I’m thinking the same probability for randomly-placed satellites, but a higher probability for polar orbits.) This would suggest that I should go with shorter subs – perhaps 10 minutes instead of 15 – to lose less time when an image is spoiled.

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