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Dark site observation???

Started by Inge_S, 09/13/2002 12:15PM
Posted 09/13/2002 12:15PM Opening Post
Wednesday night a few of the members of our local astronomy club went out observing. Conditions seemed very promising, no wind, transparent air, no moon interfering and end of twilight about 22:15 p.m. We had three scopes available, my 8-inch PB, a home-made 6-inch F/10 dob with Lichtenknecker optics and a short-tube 80mm refractor which was not used very much. There was some stray light from the town 10 - 15 km away, and some auroral glow in the north, and during the time needed for dark-adaptation we observed double stars.

Zeta Aquarii was very nice in both Dobsonians, and I trained the PB on several closer doubles just to confirm that seeing was sub-arcsecond.

But a really dark sky appears to be difficult to get these days. As our eyes got dark-adapted the auroral activity increased, and although most of the activity was in the north, the light from the aurora became annoying. Of course, the brighter deep-sky objects were nice. We observed M27, M71, M92, M81/M82 and several others with pleasure. Also M33 and M101 were visible, but the views could not be compared with what could be experienced under excellent conditions. The Veil-nebula with an O-III filter was nice, but not outstanding. The Crescent-nebula (NGC 6888) was extremely difficult. The 14.2 mag star near M57 could not be seen (sometimes this is possible from my driveway). NGC7331 was reasonably bright, but Stephan's quintet was a mere smudge even when its position was accurately known. I didn't even bother to look for NGC185, NGC147 and IC342 which actually were on my observing schedule.

Two objects, however, seemed to impress the club members. The two planetaries NGC7027 and NGC7662 impressed both with their surface brightness and their blue colour.

During the session I also observed the two globulars in Delphinus. NGC6934 is the brighter of the two. The 8-inch, in fact, shows several stars in it. It reminds me a bit of M56, although it is a bit fainter. NGC7006 is much fainter due to its location 150.000 light years away from the galactic centre on the far side of the Milky Way. It appears much smaller to me than the "Intergalactic traveller" in Lynx, but the brightness is comparable.

At the end of the session, the auroral display was quite impressive. Certainly it is a beautiful phenomenon, but hopefully the next great display will be an evening when the wind is too strong for telescopic observation. We really need the few clear, dark nights we can get.
Posted 09/13/2002 06:35PM #1

Do you subscribe to 'AstroAlert' which forecasts the aurora activity along with all sorts of sun action?