Observing Report for August 22-24, 2003 - Plettstone
Friday
Observers: Michelle, Rashad, Guillermo, Nick & Meifong, and Richard C.
Temperatures hovered around the mid- to low- 60's during the night. Dew
threatened, but never formed. The RH topped out at 90%, and began to drop
after 2AM. No wind. Seeing and transparency were good to very good. Seeing
softened a bit during the night.
Saturday
Observers: Richard C. left and joined by Richard N. and Phil T.
Temperatures hovered around the mid- 60's during the night. Dew was never an
issue. The RH topped out at 78%. No wind. Seeing was very good and
transparency was extraordinary!
Sunday
Only I observed the extra night, hoping for a repeat of yesterday.
Temperatures hovered around 70°F during the night. It was very dry. The RH
never reached 50%. No wind. Yet, seeing and transparency were only average.
However, I'm not complaining about a pleasant, average, dark night.
Scope: 17.5" f/4.5 ultralight
Eyepieces: mostly 7mm and 9mm Nagler T6.
Brief Summary and Selected Highlights
My primary focus was to observe galaxies in Abell 2197. In addition, I
wanted to add to my list of observations in Abell 2199. A2197 and A2199 form
a "Double Cluster" approximately 4-1/2° NW of M13 in Hercules. Member
galaxies aren't as concentrated or as organized as in denser clusters such
as A426 or A1656. One can think of this pair as the galactic analogue to the
familiar "Double (star) Cluster" in Perseus.
Uranometria indicates member galaxies lie within partially overlapping
circles with diameters approximately 1.5° and lying 1.5° apart. My target
lists, generated by searching the NASA/IPAC Extragalactic Database (NED),
include selected galaxies within 1° of each cluster center.
http://pw2.netcom.com/~ahighe/A2197.htm
http://pw2.netcom.com/~ahighe/a2199temp.htm
In addition to the apparent spatial overlap of the clusters, radial
velocities of galaxies in the two clusters also overlap. Consequently, it
is difficult to unambiguously assign membership to galaxies in the overlap
region.
I was able to spend a total of 4-1/2 hours on A2197 and 1-1/2 hours on A2199
during the three nights. The excellent skies allowed me to observe 91
galaxies on the A2197 target list. 75 observations were new. In addition, I
added 25 observations to the A2199 list, bringing the total to 78. Five
objects appear on both lists.
Each target list contains 135-150 objects with photographic magnitudes as
faint as 17.5. Based on the results so far, I hope to be able to observe at
least 100 galaxies in each cluster.
Some Observing Details
"The Sky" planetarium databases mis-plot some galaxies in all the galaxy
clusters I've studied, with the exception of Abell 1656. "The Sky" mis-plots
approximately 10 galaxies in A2197 with deviations up to 2'. In A2199, over
30 galaxies are mis-plotted! In rich galaxy fields, such large deviations
would cause one to incorrectly identify galaxies or miss them entirely. This
is particularly true in A2199 where many of the errors occur where the
concentration of galaxies is the highest. In contrast, the most recent
version of Uranometria 2000 has fewer errors, but doesn't plot galaxies
faint enough.
For example, "The Sky" indicates that MCG+7-34-51 and MCG+7-34-52 are a
close pair of galaxies whose orientation relative to each other runs
approximately north-south. In fact, the pair is located 2' north of the
plotted location and their orientation is rotated 45°. It is not possible to
identify them correctly using "The Sky". Uranometria plots them correctly.
There is considerable confusing about the location of galaxy NGC 6141. "The
Sky" apparently has at least two database entries for this object. One is
3.5' away from the correct location. The other is 22.5' away! Uranometria
gives the correct location of NGC 6141. But there appears to be a misprint
or second identification for it as well. In Chart A3, galaxy NGC 6147 is
labeled as "6147,41". I assume this indicates that either the galaxy shares
both ID's or there is a second galaxy so close to NGC 6147 that it doesn't
show up as a separate symbol. Either interpretation is incorrect. There is,
in fact, a faint galaxy less than 1' WSW of NGC 6147. It is MCG+7-34-22. I
could hold it with averted vision 30% of the time.
Uranometria does have one clear misidentification in A2197. What it labels
as MCG+7-34-92 is really CGCG224-56. MCG+7-34-92 actually is 4.25' SSW from
the indicated location "The Sky" also plots MCG+7-34-92 incorrectly -
showing a location approximately halfway between CGCG224-56 and its true
location.
NGC 6138 is mis-plotted in "The Sky" by 2'. NGC 6138 appears to be plotted
and labeled correctly in Uranometria. It wasn't too difficult to see. At
286X, I could hold it with averted vision 80% of the time. Other
observations, as well as correct coordinates and other data, are listed in
the tables provided on the above-mentioned web pages.
Just so you know, my data source is the NED, or in some cases, recent
publications. I further confirm that all coordinates from the NED correspond
to objects on Digitized Survey Images.
Conditions on Saturday were the best I've seen in at least a year. It's been
a long time since I've experienced such outstanding transparency. Seeing was
also very good, which permitted wonderful high power views of faint
structure. For example, spiral structure was evident in M74, often regarded
as one of the more challenging Messier targets for small scopes. Likewise,
low surface brightness M33 showed obvious spiral arms filled with details -
dust lanes, knots of stars, and puffs of nebulosity. I don't often use
nebula filters on galaxies. However, a UHC filter helped to differentiate
regions of nebulosity from knots of galactic star clouds. In particular, NGC
588, NGC 595, and NGC 604 (the brightest) are a few of the bright nebula
visible in M33.
It was also an opportunity to check out some new equipment. Michelle had
just completed her 15" f/5 and had it out for "first light". It is a
beautiful scope with equally beautiful performance. At one point we were
observing Stefan's Quintet in Pegasus with her 5mm Nagler T6 (380X). The
Quintet was incredible - it just leapt out of the eyepiece. I can't remember
ever seeing it so large, bright, and distinct. I could hold even the
faintest component with averted vision 80% of the time. The galaxies in the
close central pair (NGC 7318A &B) were like a pair of bright headlights.
They were well separated, showing bright central cores within their fainter
haloes.
It was also "first light" for some new modifications on Guillermo's 18"
Obsession. He had just recently installed the Rx Design GOTO system. It
performed surprisingly well, especially considering that this was
essentially the first time Guillermo turned it on - a testimony to the
product and Guillermo's careful installation.
This was an absolutely wonderful weekend. Thanks to all of you who shared
conversation and views. My special thanks to Michelle for her continued
generosity - Plettstone is a treasure.
Albert