[AZ-Observing] Observing Notes from Mount Bigelow 61" Session

From: Tom Polakis <tpolakis@xxxxxxx>
To: AZ-Observing@xxxxxxxxxxxxx
Date: Sat, 06 Jan 2007 17:16:56 -0700
A little while back, I posted a link to my pictures from our trip to 
Mount Bigelow to use a 61" telescope.  Here are the observing notes 
from that night.

=========

It was clear until 1 a.m. with good transparency and
seeing that was mostly around 2". Dave's Sky Quality Meter produced
zenith sky brightness readings of around 21.00 to 21.05, so the site
was okay, but still a bit close to Tucson to be called dark.

Pictures from the trip are posted here...
<http://www.pbase.com/polakis/bigelow2006>http://www.pbase.com/polakis/bigelow2006

Since the telescope is a 61" f/13.5, you choose your targets
carefully. We elected to use almost exclusively a 55mm Plossl, which
produced 380x and an 8' field of view with a 4.1mm exit
pupil. Occasionally we used a 31mm Nagler, which produced an almost
equal field of view, but 675x was pushing it for this night, no
matter how sharp the scope is. And just to say I did it, I looked
once through the 20mm eyepiece, which gave us a shimmering
1060x. Since the telescope was to be used for pointing at the
ecliptic, a major compromise is that its English yoke prohibits
pointing north of +60 degrees declination.

Posted below are the observations worth mentioning from my notes,
which leaves out a half dozen of the 25 objects we observed. Suffice
to say, that on a purely aesthetic basis, there are plenty of splashy
objects that do not look as good through constricted field of the 61"
as they do through my 10". The choices were mainly small objects
with high surface brightness, and that led us to a number of
planetary nebulae that gave us "best ever" views. Disclaimer: these
are not my most systematic notes, as there were distractions aplenty,
including my camera.

Finally, I don't know what it takes to get a night on this scope. I
am fortunate to have a friend like Dave Healy.

-----------

NGC 7009, Saturn Nebula: Bright central star is surrounded by a
mottled disc that is vivid blue. There is a dark hollow around the
star, and many knots immediately surrounding it. The surrounding
shell is "inclined" differently, and readily shows the thin arms
leading to the two bulbous ansae. There is a bright knot or star on
the minor axis at the perimeter of the shell.

Einstein's Cross, gravitational lens: This was Dave's single
mandatory target. Succeeded to see an extremely faint haze with four
barely visible nodules. Two of these ("bottom" and "left" -- didn't
note p.a.'s) are brighter.

M77, spiral galaxy: Inner spiral has a very bright core that is
nearly stellar, surrounded by a 2:1 barred inner spiral. Around this
are flocculent spiral arms that form a nearly circular pattern.

NGC 246, planetary nebula: Without a nebula filter, a broken ring
fills the field. The central star has a very faint companion
nearby. With the UHC filter, the ring is thin with numerous breaks;
a strip of nebulosity cuts a two-thirds chord of the disc. Can't say
I'm seeing that much more detail than the 20", but it's brighter.

Abell 2, planetary nebula: A circular disc that eventually shows
itself as a thick ring with a subtly darker center. No central star
is visible, but there is a faint star or a knot at the edge.

M76, Little Dumbbell Nebula: Shows up on Mt. Bigelow computer screen
as "L'L Dumbbell". A very bright "bowtie" is evident. There is a
thick and very bright inner rectangle flanked by symmetrical
loops. A striking 3-D appearance seems to put the planetary in front
of the star field.

NGC 7662, Little Gem Nebula: The inner shell is a very well defined
3:2 disc with an irregular edge. Again, there is a small, dark hole
surrounding the bright central star. The surrounding shell is well
revealed, but pretty smooth in texture, although its outer edge seems
a bit brighter. A milky outer halo doubles the planetary's diameter.

NGC 1023, galaxy: Bright, but not particularly interesting, very
bright core and two elliptical envelopes rotated at different
p.a.'s. I did not see NGC 1023A at edge.

M1, Crab Nebula: Mostly just an amorphous haze without the filter,
but man, the OIII filter brings this one to life! There are many
criss-crossing filaments for many fields that fully rival deep CDD
images. Now the continuous background haze is gone, replaced by
these filaments. Removing the filter easily shows pulsar and
similarly bright star in pair.

Merope, reflection nebula in Pleiades: While we're up here, we blind
ourselves with this view. Scope fails to show IC 349 near Merope,
and panning it shows a couple thin wisps, but 380x just isn't right
for the Pleiades, so we move on quickly.

HIckson 20A: All six galaxies are faint and small in a busy star
field. I really need to see just how faint these are in my 20", as I
haven't looked with it yet.

IC 418, planetary nebula: Very bright star with a surrounding
circular ring. The neon pink color has never been so obvious, but
now there is a burnt orange color at the edge of the disk. Mottled
detail fills the ring with complexity. An outer halo (first sighting
of it for me) doubles the size.

R Leporis: Yep, it's red.

M42, Orion Nebula: Too much detail to describe and would take far too
much time panning at 380x. The ruddy color of the wings and the lime
green around the Trapezium is pretty obvious.

NGC 2261, Hubble's Variable Nebula: The west wall is very bright and
ends abruptly, containing a small highlight halfway along its
length. Plenty of mottling fills the wedge shape of the nebula,
including a sizeable dark shadow just away from R Monocerotis.

NGC 2392, Eskimo Nebula: This one stands up well to 675x (or the
seeing improved). The star is surrounded by an oval shell with a
dark center in an asymmetrical egg shape. The "parka hood" is
slightly fainter and perfectly circular. There are fine, radial
features all around its circumference.

Saturn: Seeing didn't improve after all, so there isn't more to see
tonight than the view with a good amateur scope. The main difference
is the brightness and color of the cloud bands. They are delineated
by their various shades of tan in the polar regions. In contrast to
many sharp Webcam images that have been victimized by a lot of
sharpening, there is not that much color contrast between the A and B
rings, though the Crepe ring remains dull gray. I can't imagine
stopping down could improve the view; as with Jupiter, a lot of the
detail is color contrasts, and stopping down only mutes that.

J320, planetary nebula: This one is a bit too small for tonight. It
is is elongated 3:2 with either a brighter center or a central
star. There is a very faint outer halo.

NGC 2371/2, planetary nebula: Two lobes surround a central star. At
nearly three times the radius of these lobes are outer symmetrical
knots. The OIII filter brings out 2 more, fainter knots at 3 o'clock
and 9 o'clock locations, and the eye can begin to trace (imagine?) a
full-radius disc through the four knots.

The other half dozen objects were:

M15
NGC 253
M79
M78
IC 434
NGC 2359


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[AZ-Observing] Observing Notes from Mount Bigelow 61" Session

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