FreeLists / az-observing / [AZ-Observing] Re: R: 2008 All Arizona Messier Marathon - results

[Jeff Hopkins <phxjeff@xxxxxxxxxxx>]

Hi AJ,

While I have little interest in the AAMM, like Lorenzo, I too am 
amazed at the observation of M77 one degree above the horizon at 
twilight. As I understand it M77 is slightly brighter than 9th 
Magnitude (extraterrestrial magnitude). At one degree above the 
horizon the extinction is near a maximum. That coupled with the 
closeness to the setting Sun would seem to make a real detection of 
the galaxy next to impossible even with a very large  (meter class) 
telescopes let alone an 8".

For example air mass is equally to approximately 1/cos(angle from 
zenith or 89). Extinction is the extinction coefficient times the air 
mass as a magnitude. At 89 degrees the air mass is around 57. 
Assuming an extinction coefficient of say 0.3 for the visual 
wavelengths, the extinction would be around magnitude 17 which would 
put M77 at about magnitude 26 (17 + 9). That is indeed a big 
challenge for an 8" scope at twilight.

Without some objective data, I find it very difficult to believe it 
was a real observation and perhaps more of the "mind's eye" type.

Jeff

At 09:20 -0700 04/11/2008, AJ Crayon wrote:
>Lorenzo, thank you for your compliments about SAC and our skies here in
>Arizona.
>
>Re - finding M77.  As I wan't at the AAMM so I can't give first hand
>information.  However it was know that a SAC observer found M77 the day
>before the marathon, from the same site, and with a C11, I believe.  The
>observation was defines as extremely difficult.  According to the
>announcement, M77 was 1 degree above the horizon at twilight, which was
>20:14pm Mountain Standard Time (03:14 UT Sunday).  This gives a small
>window, before twilight, to find and do the observation.  No doubt this is a
>surprise, yet every marathon produces some sort of surprise because we have
>such experienced observers.
>
>AJ Crayon
>Phoenix, AZ

-- 
Jeff Hopkins
HPO SOFT
Counting Photons
http://www.hposoft.com/Astro/astro.html
Hopkins Phoenix Observatory
7812 West Clayton Drive
Phoenix, Arizona 85033-2439 U.S.A.
(623)849-5889
(623) 247-1190 (Fax)
www.hposoft.com
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