FreeLists / az-observing / [AZ-Observing] Re: R: 2008 All Arizona Messier Marathon - results

[Bob Christ <bchrist@xxxxxxxxxxxxxx>]

If my figuring is correct, M77 at nautical twilight (19:45) was ~ 6.5° 
above the horizon.  Here is the approach I used and failed ...

Scope: Celestron NexStar 9.25" GPS.  This time of year I use Polaris 
(always) and Sirius as alignment stars.  As soon as Sirius became 
visible (still very much daylight), I performed a one-star alignment on 
it and then slewed to Polaris to locate it -totally invisible to the 
naked eye at this point.  I then performed my usual 2-star alignment 
using Polaris and Sirius.  The sky was light when I slewed to M77, and 
it was significantly above the mountains.  (Later, my alignment proved 
to be absolutely "right-on")  At his point, the view was strictly a nice 
shade of blue sky.

When the sky started to darken I used the Precision Go-To feature 
(calibrated on star Kaffalijidhma, mag 3.53) to further assure I was 
right on M77.  I checked the view every 10 minutes until Nautical 
Twilight and then pretty much "glued" myself to the eyepiece .  As 
Astronomical Twilight approached several stars were visible in the 1° 
FOV, but no M77.  I remained at the eyepiece until the mountains in the 
horizon finally extended a little more than half-way up in the FOV.  
Crushed!

Methinks some type filter would have been beneficial?  There's a DGM 
Galaxy Filter (modified broadband) available - might something like this 
have helped?  Don't know.

Bob Christ



Brian Skiff wrote:
>      Since M77 has such a bright nucleus, it is probably recoverable
> in considerable twilight, especially with a well-aligned go-to mount.
> Don't know what the answer is, however.  How high up was it at -12 deg
> solar altitude (i.e. end of nautical twilight)?  The sky is
> probably plenty dark then for M77.
>
>      The bright twilight/low altitude observations more-or-less
> required by the MM, by the way, argues in favor of holding the Marathon
> as close as possible to the optimum date even with, say, 40% Moonlight.
> This is especially so given the horsepower brought to bear on the
> targets (per the rankings list).  As long as it's cloudfree,
> modest Moonlight is not a serious hindrance, and allows you an
> out if the weather's bad to hold it the next weekend (or whatever)
> without the Moon.
>
>
> \Brian
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