Observations from General Nathan Twining Observatory, New
Mexico - New 2007 Mar. 22, 20h UT
This is the observatory of The Albuquerque Astronomical Society at
Belen, NM
From: Steve Welch
Subject: Re: A first summary of observations of Sun. am's Pluto occultation
Date: Tue, 20 Mar 2007 23:03:07 -0600
To: dunham@starpower.net
Hi, David,
Bill Wallace and myself at GNTO (Belen, NM) both recorded the
occultation. It was cloudy over most of the sky from GNTO earlier
in the evening, but never got cloudy in the southeast, and about an
hour and a half before the occultation it totally cleared up, so we
were luckier than you or Becky or many others. Bill and I both used
integrating video cameras with 2 second integrations, Bill a
Malincam Ultra, and me an SAC9V (modified Mintron), and both of us
easily saw the Pluto plus star target on our video monitors.
Bill and I observed the occultation with these extended red
sensitivity integrating video cameras (Sony EXview SuperHAD CCD's)
with no filtration on the TAAS (The Albuquerque Astronomical
Society) Observatory's 11" Celestron OTA and 16" Newtonian
telescopes, respectively. Both of our cameras were running in a 2
second integration mode, both using KiwiOSD's, and both were
recording the event on miniDV tape using my two Canon Camcorders.
The star plus Pluto image was very easily visible on the video
monitors. We were seeing quite a few more stars on the monitors
than our pointing computer was showing with a 16 mag cutoff, so I
think we'll see the occultation when I reduce the data, but I'm
going to have to get some software working or send our video tapes
off to someone who can reduce them.
Although I haven't yet figured out how to extract the data from the
video tape yet, none of us saw the occultation for sure with our
eyeballs on the video monitors. Ariel Boston (my 19 year old
daughter) and Pete Eschman (the observatory director) thought they
saw Pluto get fainter than a nearby star that they thought it was a
little brighter than on the video monitor, but I was looking at the
same monitor, and it was beyond me. That was on the 16" scope, where
I was running at a much too large plate scale of something like 1/2
arcsec per pixel. For the Charon occultation later this year, and
I'll try to use a new focuser we just had made for the 16" for that
occultation--we should be able to use a focal reducer and get a more
reasonable 1 or 2 arc sec per pixel, and and thus get a better
signal to noise ratio with these low-cost amateur CCD cameras (they
are actually modified surveillance cameras--pretty impressive for
what they are).
The scope I was on (the 16") wasn't tracking very well, at the time
of the occultation, but between Bill's and my video tapes, we should
get some good timings. Originally, I had planned on using my new
Watec WAT-902H2 Ultimate camera on this 16" scope and stacking
frames until we got something reasonable, However, we didn't have
time to try out the new focuser that might have given me a chance to
get the plate scale down to something more reasonable (our 16" scope
is f/ 6.1), and I was afraid to try it. Considering how badly the
scope was tracking, I think I made the right decision--I'm not sure
I could have acquired and kept Pluto in the tiny field (even with a
focal reducer) when I probably could only just barely see it on the
monitor. Next time...
Fun stuff!
I'll try to reduce my tapes or send them to someone who can here
Real Soon Now. Do you have any suggestions?
Steve
---
Steve Welch -- swelch@complex.org or swelch@philzimmermann.com
http://complex.org/~swelch
Complex Systems Research, Inc.
+1-505-866-7668 (NM voice) +1-505-866-4668 (NM fax)
+1-303-530-2661 (CSR voice)
+1-303-579-4778 (mobile)