Re[4]: ATM body heat in the light path.

[Dwight Elvey <elvey@hal.com>]

Dominic-Luc Webb molmed <Dominic.Luc-Webb@molmed.ki.se> wrote:
> 
>  For a human body to do this by merely standing 
> near a telescope is intuitively difficult to grasp, but I could 
> make some calculations tomorrow to get a gestimate of how much 
> signal one would get.


Hi Dominic
 On a quite night, when out looking at one of the comets,
( can't remember which one it was ) I was also looking a
Mars. It was a real quite night and Mars was quite clear.
Mars got really distorted for a while and then cleared
again. I thought at first it was just jet stream or something.
I remembered the effect I'd seen from placing my hand
near the front and started to look for the source.
I noticed that there was a house on the ridge
right under the path of Mars, about 1/4 mile. I was able to walk up from
that house some 40 degrees into the sky and clearly see the turbulence
on stars as I went up. Local things like these can have
quite an effect and am not surprise to see someone claiming
that someone standing in front of the telescope by about
20 feet or so could also do as much.
 Rather then calculating it, go out and experiment some,
then go back and explain it with calculation. This will
make sure that you model it correctly. Do my out of focus
trick first.
Dwight