[AZ-Observing] Re: Trip to NM -- and sky brightness

  • From: Stan Gorodenski <stanlep@xxxxxxxxxxxxx>
  • To: az-observing@xxxxxxxxxxxxx, astroayers@xxxxxxxxx
  • Date: Sun, 07 Jun 2009 14:05:19 -0700


Robert Ayers wrote:

>I read your article with interest since I'm looking for a dark sky
>site in AZ-NM and have looked at locations around Pie Town / Quemado.

I would like to encourage you to look at the area I am in. I am in a 
subdivision called Last Frontier. It is about 20 miles west-sw of Datil. 
There are already two amateur astronomers, not counting me,  in the 
surrounding subdivisions of Old Thomas Place, and other subdivisions I 
do not recall. One of the amateurs is from Seattle and is in the process 
of building his home and observatory there. He already has a floor and a 
40" sq block pier laid for the observatory. The other one is currently 
living there and has a more economical observatory using one of those 
polyethylene(?) domes that glow in the dark (something he doesn't like 
but discovered this feature after he put it up and started using it). 
Good Earth Realty in Datil is the closest realty to my place and these 
other subdivisions.

>I agree that your SQM reading are un-good.   

Thanks for the comment. This is what I want to hear, not that I want to 
hear bad things, just straight forward opinions.

>"Far away from lights"
>one should see 21.8 or better.   

These were taken in September, as I stated in my original email, and it 
was raining here and there while I was camped out for 5 days. I had no 
problem at night with clouds, though. The day I left for Arizona I had 
to delay my departure until the afternoon because of rain. I would guess 
since it was in the monsoon season this would pretty much rule out dust 
from the Plains of San Augustin to the south. When I took the readings I 
pointed straight up and so I suppose I could go to a planetarium 
software, like Guide, and see what part of the sky I might have been 
reading. It does appear, from what others have said, that it more than 
likely is sky glow. If so, it would be useful to know if the atmospheric 
conditions in the area has more nights of sky glow than other areas. I 
mentioned the fact that the skies appear lighter than I think they 
should to the amateur that lives near my place. He said he notices that 
once in awhile the skies get this way, but he doesn't know why. Probably 
sky glow.

>But I note that SQMs do differ.   And
>Brian Skiff notes that when the summer Milky Way is overhead a zenith
>SQM reading at a dark site will be affected by the Milky Way.   Might
>your varying readings from Sept 2007 be partly explained by when at
>night you made the readings?  Milky Way moves ...
>My absolutely best sky was observing from north Chile, in the Atacama
>desert at over 13000 feet.  Retinal oxygen starvation did darken the
>sky, but what was scary-good was that the "color" of the sky was the
>same at the horizon as at the zenith.  

This is the way the sky is at my place, and pretty much this way all the 
way from Red Hill (about 10 miles E of the Az-NM border) to Datil.

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