From: Goran Hosinsky 
To:  atm{at}shore.net
Reply-To: Goran Hosinsky 


Thanks Tom for your comments!
A site test campaign with two 24 m masts and thermo sensors is outside my
possibilities (I have had some experience participating in the LEST
campaign at various sites).  I am looking for something simple and cheap.
The possible sites are all inside a radius of 200 meters. If I could put
numbers
on the twinkling of a star in zenith or measure the seeing disk this would be a
way. I would just walk between the different sites and measure. Not
simultaneously but good enough.

I have a 3”  f16 old refractor that I could set up at the second site. On the
first site I could use my 10” LXD55 S/N stopped down to 3” (f/13.5), but
how do I put a numeric value on the seeing?

Saludos
Goran

Tom Krajci wrote:

>>From: Goran Hosinsky 
>>
>>
>
>
>
>>I am planning for my observation hut and in the meantime I have set up
>>
>>
>a
>
>
>>fixed pier in the garden.
>>I am living on the slope of a volcanic island and the area consists of
>>small ridges going down slope,
>>perhaps 50’ high and 300’ away from the next one. My pier is in the
>>valley between two ridges,
>>near one of them. At night there is a marked temperature variation
>>between the ridges and the
>>valleys with the valleys being notable colder and sometimes with cool
>>air moving downslope.
>>
>>
>
>This flow of cold air you mention is similar to what I have repeatedly
>suffered while at the Okie-Tex Star Party.  See:
>http://www.okie-tex.com/
>
>It spoiled seeing because we were at the mouth of a box canyon...and the
>flood of downstream cold air rolled right over the observing site.
>Pretty by day...dark, transparent skies...lousy seeing.  It was great
>for low power and binocular observing.
>
>
>
>>what would be the best place for the observation hut. Up
>>on the ridge or down
>>in the valley?
>>
>>
>
>Valley is often pretty bad.  Ridge tops are usually better.
>
>
>
>>With the telescope being near ground the cool air moving
>>down the slope might
>>blow away the local heating from the ground?
>>
>>
>
>Perhaps in the early evening this is true, but as night continues, the
>flood of cold air will probably get worse.  This is how it is at
>Okie-Tex.  I've also experienced something similar in Chimgan,
>Uzbekistan...near the foot of a 10,000 ridge.  I need to find an
>observing site a few kilometers farther from this ridge to avoid the
>cold 'avalance' of air from the mountaintops.
>
>
>
>>I would like to make comparative tests of the seeing before deciding
>>where to put my hut but
>>I do not see how I can do that. Any suggestions?
>>
>>
>
>Use a temperature probe/thermometer to measure air temperature at
>various heights above ground at various sites, on various nights.  Keep
>and analyze the data.  Look at the rate of temperature drop versus
>height above ground.  If you are serious about good seeing you may find
>your data implies that if you put your scope 8 feet, or 12 feet above
>ground...you'll avoid the lousy seeing from rapid temperature change
>near the ground.
>
>Clyde Tombaugh, discoverer of Pluto...his 16 inch telescope was elevated
>above the ground for this reason.  How high?  I don't recall...maybe 8
>feet or so.
>
>If you are a devotee of the Stellafane bathing suit contest approach to
>telescope making...an elevated observing platform is not for you.  If
>you are serious about good seeing...you may need an elevated platform.
>
>Tom Krajci
>Tashkent, Uzbekistan
>
>
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