[AZ-Observing] Re: MM date limits (again)
- From: Tom Polakis <tpolakis@xxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Wed, 17 Mar 2004 18:24:32
The subject of the date range of a perfect score in a Messier marathon
lends itself well to comparing observations with desktop planetarium
software results. Naturally, I can't resist analyzing it to death.
The best source of results is the SEDS site, which is back up and running.
http://www.seds.org/messier/xtra/marathon/results.html
March 29 is near the last date for seeing M74, and that was the Saturday of
the 2003 marathon. 14 people saw all 110 objects, so they must have seen
M74. I found it exceedingly difficult to verify that we were seeing M74.
Frank Kraljic's 10-inch barely showed a haze around a very dim core for no
more than a few minutes before M74 set into the crud layer. It helped to
have a very large-scale map (Megastar with a 1-degree field of view) nearby
to compare the star field. I might believe somebody saw M74 on the 30th,
but even that would be straining credibility.
On the morning side, 25 people at the 2001 Arizona marathon saw M30 as part
of their perfect score. This one was held on March 24/25. And on March
23/24, 1985, Gerry Rattley was the first documented case of somebody seeing
all 110. This is the earliest date for M30 documented on the SEDS site,
with the exception of one outlier. There is one observation of M30 from
the Arizona marathon on March 16/17, 1996.
Here's what the software shows. With the sun at an altitude of -10
degrees, the altitude of M30 is:
March 16/17: 3 deg. 23'
March 20/21: 5 deg. 13'
March 23/24: 6 deg. 35'
I am not so certain that M30 will not be visible from the Arizona City site
next Sunday morning. I don't know the altitude of those distant mountains,
but they can't be more than a couple degrees (it's always much less than
you estimate during daylight). The marathon window for our latitude may be
as long as 10 days. It's interesting to run the planetarium software for
other latitudes. Above something like 40 degrees north, there is no window
for finding all 110 objects, and at 25 degrees north, the window lasts for
weeks.
Tom
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