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

[Stan Gorodenski <stanlep@xxxxxxxxxxxxx>]

Very good analysis Jeff and I agree, especially since this is an 
extended object. However, as you mentioned, it is very close to the Sun 
and so what you failed to take into account was the reflection of the 
sunlight off the galaxy. :-)
Stan


Jeff Hopkins wrote:

>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
>>    
>>
>
>  
>
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