Archive for February 1st, 2017

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Misusing a fast reflactor: moon-gazing with the Bresser AR102S Comet Edition

February 1, 2017

bresser-ar102s-comet-set-up-for-moongazing

I was going to hold off before I posted anything on the performance of the Bresser Messier AR102S Comet Edition (which I swear I am going to start calling something else, just as soon as I think of a good nickname). That’s because I haven’t had a chance to try it out under the conditions where it is likely to do well. This is an optically fast scope, optimized for low-power, widefield scanning, ideally under dark skies where those faint stars can really pop. A great time and place to test-drive this scope would have been last Saturday night at the Salton Sea, right after the new moon, when Terry Nakazono and I stayed up observing almost to dawn, (expect that observing report in the not-too-distant future).

Unfortunately, the scope arrived Sunday afternoon, a day late for our Salton trip. Mount Baldy is covered in ice and snow, and I haven’t had time on these school nights to get up there anyway, much less to get to anyplace farther away. And the skies down here in Claremont have been crappy this week. Never clouded out, but never truly clear either – there has been a thin, high-altitude haze that is really good at both obscuring dim stuff and reflecting light pollution. So the only objects that have looked good are the bright, small things – the moon, Venus, Jupiter, and double stars. In other words, exactly the things that the AR102S Comet Edition is not specialized for.

So I don’t feel like I can give the scope a fair review yet, because all I’ve been able to do with it are the things it’s not built for. It’s like taking a Lamborghini Huracán on a Moab jeep trail – it’s not going to work out well, in ways that are completely predictable, and you’re not going to learn very much by doing it.

But when has that ever stopped me? I may not be able to review the scope, but I can still play around with it.

crescent-moon-2017-01-31-raw

Here’s a raw shot of the moon, taken with a Nikon Coolpix 4500 shooting afocally (and handheld) through the supplied 20mm 70-degree eyepiece.

crescent-moon-2017-01-31-processed

Same shot tweaked with Unsharp Mask and Curves in GIMP.

crescent-moon-2017-01-31-greyscale

And then converted to black and white.

I didn’t learn much. Yes, there is chromatic aberration. In other news, water is wet and the Pope is Catholic. On the plus side, the Trapezium in Orion is split into four members at 23x. Haven’t tried it on the Double Double or any other double stars, really.

On the to-do list are (1) to get this scope out someplace dark and clear and really put it through its paces, at a variety of magnifications – and using a variety of eyepiece designs – on a variety of targets, (2) to do some actual testing on close double stars and doubles with significant magnitude differences, and (3) to experiment with sub-aperture masks to knock down the CA on bright stuff. “Why not just use a smaller or better-corrected scope?” you may wonder. Well, this is sold as a travel kit, and if by using a sub-aperture mask I can make it into a passable solar system scope, I’ve just made it a better all-rounder when and if I take it on the road.

Given the waxing moon and the continuing lousy forecast for the coming week, I’ll probably have to tackle that to-do list in reverse order. Stay tuned.

earthshine-2017-01-31

Parting shot. I got this Earthshine pic by doing a half-second exposure with the Coolpix. It’s not nearly as good as the one in the banner at the top of the page. I need to try again next cycle when the moon is younger.