A Cool Night with a NexStar

DS022604 RECENT OBSERVATIONS
by David Knisely

DATE: February 26th, 2004, 0130 to 0445 hrs UTC.
LOCATION: Beatrice, Nebraska, USA, 40.283N, 96.735W, (402m elevation)
INSTRUMENTS: Celestron NexStar 9.25GPS SCT, 78x, 195x, 297x, 388x, 479x,
CONDITIONS: Partly Cloudy, Temp. 30 deg. F. (-1.1 deg. C), wind calm.
UNAIDED-EYE ZENITH LIMITING MAGNITUDE: 5.0
SEEING (above 45 deg. altitude): 1.5 to 0.5 arc seconds (Antoniadi II)

OBJECTS OBSERVED: Venus, Mars, Moon, Saturn, Jupiter, Struve 872, Rigel
Sirius, M42.

OBSERVATIONS: I finally got a night when it wasn't near or below zero and the
snow cover wasn't covering up the driveway. I had the new NexStar 9.25GPS
that I am reviewing out for cooldown while I went on a quick trip out to
Arbys for a sandwich. By the time I got back, all was ready, and unlike
previous outings with the 9.25, the seeing was quite good. After watching
the NexStar go though its alignment gymnastics (and doing some tweaking of
the alignment) my first target was brilliant Venus. Even at 78x, it showed
its gibbous form well, with a pure-white color. From there, it was a short
slew to the moon, but one problem with Go-To operation is that the moon is
a very big target. I ended up looking at the area illuminated by only
Earthshine, so it took a little slewing to get back onto the illuminated
portion. The view, despite a little high cirrus, was spectacular, with a high
level of fine detail visible. The sun was just rising on the central peak of
Theophilus, so it was fun to watch more and more of the peak emerge from the
darkness. The area around and south of Madler showed numerous tiny pits in a
fine field on the west edge of Mare Nectaris. It was fun to slew around all
over the surface, rather than having to reach up and nudge the scope
repeatedly to get things where I wanted them.
I could have just manually slewed the scope to Mars since it wasn't very
far away from the moon, but since I had a high power eyepiece in the scope, I
decided to let the scope do the work and see just how close it would come.
The slew didn't put Mars quite in the center, but it wasn't far away. At
297x and up, the planet was still quite tiny (5.76" arc), but surprisingly
showed a vague dark patch (probably Mare Erythraeum) across the middle of the
disk, along with a hint of a bluish patch around the south polar region.
From Mars, it was on to Rigel, and even at 78x, the star's tiny faint
companion was nicely shown, with jet-black sky between them. At 297x, the
companion was easier to see and occasionally showed a diffraction disk when
the seeing settled down. With seeing this good, I decided to try for the E
and F stars in the Trapezium, so with a couple of keystrokes, I sent the
scope slewing to M42. Sure enough, both E and F were visible through some
of the high haze which was passing through that region, along with the very
mottled nebulosity of the central core of the Orion nebula. With these
successes, I decided to try for the "pup" white dwarf companion to Sirius.
Unfortunately, I didn't get more than a hint of it, as the seeing at that
bright star (located over a nearby home with a heat vent) made the area
around it mottled with "false" companions.
I had seen in Richard Digon-Smith's book STARLIST 2000 that he noted
the faint double star Struve 872 as one of the more colorful binaries. The
book indicated that it was a gold-blue pair, so I was off to try and find
it. While the database of the NexStar has a number of the most prominent
double stars in its double-star list, Struve 872 wasn't one of them (and from
the view I got, I can see why it didn't make the list). Digon-Smith's book
doesn't give the coordinates for the double, so I had to go to Megastar to
find out where it was. I dutifully input the coordinates to the NexStar, and
it obligingly slewed to the double. As I have seen with other colorful
claims in Digon-Smith's book, this one also wasn't all that accurate. It
consists of a magnitude 6.9 star and a mag. 7.5 star about 11.3 arc seconds
apart, with very little difference in color between them. The primary was
perhaps a pale yellowish-white, and the companion was maybe a bit more yellow
but fainter, so it was difficult to see much of a color contrast here.
I had had enough of doubles for a while, so it was on to Saturn. My
first look brought out an immediate "WOW!" as seeing was rock-steady. The
contrast provided by the StarBright XLT coatings put a lot of black sky
between the inner moons of Dione, Rhea, and Tethys and the edges of the
rings. I had to search around for a while, but I finally did locate faint
Hyperion amongst the numerous field stars of Gemini. Titan showed its disk,
and I did occasionally glimpse Enceladus, but Saturn was simply stunning! It
was one of those "Mack Truck through the Cassini Division" nights, with the
planet taking all the power I could muster. The Crepe ring showed its dark
gray form well, hugging the inside of the B-ring, while the B-ring showed
its "step" variations in brightness across its span. I didn't see the true
Encke Division, but the rings still showed a lot of detail. The planet
itself showed the narrow fine belt that sits right on the equator, along with
the broad main orangish band. That large band almost appeared to contain two
distinct components, although the poleward side was rather diffuse. I could
also see two other very fine belts, one north of the dark polar cap and one
hugging the cap's northern edge. The dark southern cap itself looked a bit
darker towards its center.
For a final target, Jupiter was finally getting out of the heated air
above the house, so it was time to see what it showed. I wasn't disappointed
as the view was nearly as good as it had been at Saturn. I counted 7 or 8
belts with lots of fine detail, including a rather prominent white oval in
one of the temperate belts. The moons also showed some interesting color
variations at high power, although at low power, they seemed almost
colorless. I identified Io fairly easily, as its pale yellowish-orange
coloration made it stand out. Europa looked nearly white, while Ganymede
showed its larger and more greyish disk well. Callisto had a very pale
almost reddish-brown cast, although the color was quite subtle to say the
least. At this point, I noticed some frost forming on the side of the tube
and the corrector plate was showing dewing as well, so it was time to break
things down and get back inside to warm up a bit.

Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
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