Good SAO 165346 Graze over populous East Coast, Wed. early pm, Dec. 7
I recorded 2 D's and 2 R's from the shore of a Kent Island peninsula
in the Chesapeake Bay
Bob Vanderbei recorded 1 D and 1 R of the star brightly from 10 km
n.w. of the limit in Princeton, NJ
Updated: 2005 Dec. 9
An account of the grazing occultation, the main part of a message
to Charlie Ridgway and Dave Nelson that was copied to many others,
is given below:
Also, you can read about, and see Vanderbei's images of the star,
appearing quite bright, here.
Charlie and Dave,
Many thanks for trying to observe the southern-limit grazing
occultation of 8.8-mag. SAO 165346 on the dark side of the 45%
sunlit waxing Moon earlier tonight (the graze was during 23h UT of
2005 December 7, at 6:46 pm EST). Now you can appreciate the
difficulty of observing faint stars close to the Moon. Clean
(and/or well-baffled) optics are important as well as aperture to
observe these events.
I video recorded the graze from the back yard of a home in the
southern part of Chester, MD, on the southeast side of Kent Island
on Crab Alley Neck (peninsula) overlooking Crab Alley Bay. I used
my usual setup, a clock-driven 8-inch SCT, f/3.3 focal reducing
lens, and Supercircuits PC164C video camera, recorded with a digital
8mm tape camcorder. Although relatively faint, the view of the star
was clear, with the bright part of the Moon excluded except for just
two bright sunlit peaks at the southern cusp. As I've found in the
past, observing stars this faint is actually easier with the PC164C
video than visually. I actually set up both of my 8-inch SCT's; the
one I used (the 2nd one set up) gave slightly better-focused star
images and less scattered light than the other one. My intention
had been to set up both telescopes at separate locations, but by the
time everything was working with the first telescope, there was only
30 minutes to the graze, not enough time to find a suitable second
site and set everything up. So I just set up both telescopes there
and switched everything to the second one. At that location, I
video recorded an almost two-minute occultation, followed by another
brief (few seconds) occultation about half a minute after the main
event R. Curiously, I had trouble with the GPS time inserters; the
Kiwi never did obtain a fix, giving times 10 seconds off and
flashing X's indicating a problem. It did give a running count of
frames that will be useful. After the graze, I hooked up the McAfee
GPS time inserter in series so both displays were video recorded
during the last several minutes of my recording. After a few
minutes, the McAfee inserter did obtain a fix for a couple of
minutes, giving an accurate time insertion that was verified with
WWV minute and second tones. So its display will calibrate the Kiwi
frame count.
The event was early enough that most residents in the narrow
area (aiming for a location on the profile only 0.2 mile wide) on
the narrow peninsula (the only one on the island that covered the
whole graze zone) had not yet returned home from work. The first
homeowner of the two who were home didn't want me to observe at his
place, and recommended a park that was outside the range I wanted.
Fortunately, the residents of the other house were very
accommodating, suggesting that I observe from their back yard, and
even fed me dinner afterwards! It was cold and windy, so their
hospitality was quite welcome. I showed them the recording I made
on their TV. It turned out that they knew Don Novak, a former co-
worker of mine at CSC many years ago who held parties at his 200-
year-old house on Kent Island a few miles from where I observed
(unfortunately, Don died a few years ago).
I had originally intended to intercept the steep southwest-to-
northeast path south of Hughesville, MD, on the western side of the
Chesapeake Bay, but I could see a lot of cirrus in the south,
confirmed in the IR loop just before leaving home, that already were
reaching the Hughesville area. It turned out that s.e. Kent Island
was about the same distance, and actually much easier to drive to
since unlike US 301 & MD Route 5 in PG and Charles Counties to
Hughesville, US 50 to Kent Island has no traffic lights, and except
for a 2-mile stretch on the east side of Annapolis, even the rush-
hour traffic was relatively light, allowing relatively fast driving
speeds most of the time. Easypass made crossing the Bay Bridge easy.
It's too bad that other observers in the region with 8-inch scopes
couldn't join me to obtain more lines across the lunar profile.
David
_________________
From: charlie.ridgway@gmail.com on behalf of Charlie Ridgway
Sent: Wed 12/7/2005 11:03 PM
To: David Nelson
Cc: Dunham, David
Subject: Re: 7 December Graze After Action
I didn't see it either and for the same reason -- not enough glass.
I was using a 107mm mirror so had even less aperture than you did.
I was able to see HIP 113031 (Mag 5.80) and the Moon and HIP112974
(Mag 6.74) if I moved the Moon out of the FOV, but was not able to
see HIP 112615 (M6.19) on the bright side and closer to the moon, at
all. Although my scope has a theoretical limiting magnitude of
greater than Mag 11 I now know that in the real world I can't even
see a Mag 6.7 star approaching the dark limb of a 45% illuminated
moon. Occult probably would have told me that at the bottom of the
details page but we don't get along well so it isn't even loaded on
this incarnation of my machine.
[Charlie observed from the northern outskirts of New York City,
travelling to the site by subway]
_________________
On 12/7/05, David Nelson wrote:
David and Charlie,
In a nutshell 4 amateur astronomers didn't see the graze from
Metuchen, NJ. We didn't see the star until the moon had completed
the graze and moved away from the star. We had two 6" and two 8"
scopes, the star was quite dim, perhaps even the earthshine
overwhelmed the star. I think if we'd had a 10" or 12", we'd have
been more successful. Our digital camera (Orion StarShooter)
autocompensated for the moon's brightness and didn't have enough
gain for the star to be visible on the laptop live-video screen.
The star may be on the still images after processing.
Finally, I underestimated the cusp angle and was looking in the wrong
spot in the minutes leading up to the graze.
We now know a lot more for future events.
Dave Nelson
_________________
Click here for detailed predition information and
pre-event observation plans.
David Dunham, 2005 December 8
Phones home 301-474-4722; office 240-228-5609; car 301-526-5590
emails dunham@starpower.net or office david.dunham@jhuapl.edu