From: LARRY KLAES (ljk4_at_msn.com)
Date: Fri Jul 09 2004 - 06:02:47 PDT
----- Original Message -----
From: Trudy Bell<mailto:trudy.bell_at_WORLDNET.ATT.NET>
To: HASTRO-L_at_LISTSERV.WVU.EDU<mailto:HASTRO-L_at_LISTSERV.WVU.EDU>
Sent: Friday, July 09, 2004 8:55 AM
Subject: [HASTRO-L] black drop effect - optics, seeing, diffraction...?
I am cross-posting this request because I would like to solicit
reports from as many experienced observers as possible. If you deem this
request too off-topic for discussion on the list, please send your
information to me off-list at t.e.bell_at_ieee.org<mailto:t.e.bell_at_ieee.org> .
Since last month's transit of Venus, there has been much private and public
e-mail and verbal discussion among people who did or did not see the black
drop effect at second or third contacts. Some (e.g. Bart Fried) have
speculated whether there is a significant contribution from seeing, others
have hypothesized about its being a product of inferior optics. This
transit, some people were also watching the transit through H-alpha filters
or other specialized equipment unavailable in previous transits.
Several thoughts strike me. First, the black drop is certainly
real: it's been photographed and drawn too consistently, throwing off people
who had no expectations about what to observe. Second, not everyone has seen
it **even in the 18th and 19th centuries.** Third, we can't resolve its
causes and the conditions under which it appears without some systematic
collection of data from the 2004 transit that could be used to formulate a
definitive theory that could be tested by experiment in 2012. Lastly, the
type, size, quality, and wavelength region of the instruments used for
observation likely have some essential contribution - making this like of
investigation right up the alley of the ATS, especially after historian
Bradley Schaefer's definitive analysis in the Journal for the History of
Astronomy that concluded that the black drop is due in part to the
diffraction of light **inside a telescope.**
While memories are still fresh, I'd like to collect reports from
observers who did see the black drop, and those who did not see it. Please
include info about your telescope (aperture, focal length, type/brand,
eyepiece, any filters, method of observing - e.g., direct or projected),
your location (including altitude, surrounding terrain or water), sky
conditions (transparency, seeing, sun altitude), and what you saw or
photographed. Please also include some information about your own experience
as an astronomical observer, plus full contact information in case there are
follow-up questions. My instinct is there is a solid optics/physics story
here somewhere for some (unspecified) future issue of the Journal of the
Antique Telescope Society, **if** enough raw data can be assembled to hand
some qualified author (such as Schaefer) definitive information on which to
base an analysis, hypothesis, and proposed experiment for 2012.
It would be of particular interest to hear from people who
observed the transit through any 18th or 19th-century telescopes,
especially if they were able to compare their observations at the time of
the transit with comparable telescopes of 20th or 21st-century manufacture.
My apprehension is that if too much more time elapses, memory
dims or people's impressions might be affected by reports they might read
from others. Also, many more people observed the transit for their own
private benefit than intend to write about it for publication; those results
would also be valuable to receive.
Thank you for your consideration. - Trudy E. Bell, Managing Editor, Journal
of the Antique Telescope Society, t.e.bell_at_ieee.org<mailto:t.e.bell_at_ieee.org>
==========================================================
==========================================================
The Sun: Our Nearest Star
Engineering Tomorrow: Today's Technology Experts Envision the Next Century
==========================================================
This archive was generated by hypermail 2.1.6
: Fri Jul 09 2004 - 06:14:22 PDT
Trudy E. Bell / Writer and Editor
1260 Andrews Ave.
Lakewood, OH 44107
phone: 216-221-5008
fax: 216-221-5088 [call or e-mail first - it's off to stop unsolicited junk
faxes]
<mailto:t.e.bell_at_ieee.org<mailto:t.e.bell_at_ieee.org>> t.e.bell_at_ieee.org<mailto:t.e.bell_at_ieee.org>
<http://home.att.net/~trudy.bell
Recent books:
The Inner Planets
Comets, Meteors, Asteroids, and the Outer Reaches
Three of a series of six books comprising The New Solar System middle-school
series (Byron Preiss Visual Publications/Smart Apple Media, 2003)
(IEEE Press, 2000)
Edited by Janie Fouke, written by Trudy E. Bell and Dave Dooling
(named an Outstanding Academic Title by Choice magazine, January 2001)
<http://shop.ieee.org/store/product.asp?prodno=PC5803
http://shop.ieee.org/store/product.asp?prodno=PC5803
<http://www.wiley.com/cda/product/0,,0780353625,00.html
http://www.wiley.com/cda/product/0,,0780353625,00.html