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#151 Astrojensen

Astrojensen

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Posted 24 December 2019 - 11:53 AM

I was out in the little dome in the cold a couple nights ago.  I had a pet heating pad going on the small table with the ep case sitting on it.  The pad only gets to about 100F before it turns off.  I couldn't focus the scope precisely.  I turned off the pad and things improved greatly.  The heat plume from the pad was exiting the dome slit in front of the objective.  The same thing happens with body heat.  Bundling up sufficiently helps the body heat to not escape and ruin the seeing. 

This problem is as old as observatory domes. Some domes are much more susceptible to it than others. A wide dome slit helps tremendously. My old mentor Per Darnell told me that the old observatory in Copenhagen on Østervold had a relatively narrow dome slit and more than two persons in the dome caused bad seeing, despite the dome being quite large. 

 

I think the professionals call it "dome seeing" or "slit seeing". It's one of the downsides of a dome, compared to a roll-off roof observatory. 

 

 

Clear skies!
Thomas, Denmark


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#152 Don Taylor

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Posted 25 December 2019 - 08:51 PM

This problem is as old as observatory domes. Some domes are much more susceptible to it than others. A wide dome slit helps tremendously. My old mentor Per Darnell told me that the old observatory in Copenhagen on Østervold had a relatively narrow dome slit and more than two persons in the dome caused bad seeing, despite the dome being quite large. 

 

I think the professionals call it "dome seeing" or "slit seeing". It's one of the downsides of a dome, compared to a roll-off roof observatory. 

 

 

Clear skies!
Thomas, Denmark

 

Yes - we used the term "dome seeing". The observatory runs I participated in were just prior to the installation of apparatus for remote observing - so we were bundled-up and worked from the (hydraulic) floor beneath the telescope. The dome volume was quite large yet we took great care to reduce thermal seeing effects - by managing when the dome was opened, eliminating all possible heat sources (except for the observers) etc.  I can imagine the effects in a small dome could be quite pronounced. FWIW - many modern telescopes include extensive and sophisticated thermal management into the design - including the means to open the sides of the walls beneath the dome itself and other active and passive measures.

 

(P.S. - no, i'm not a  "professional" - but had the honor of assisting a lifelong friend's optical telescope observations used in his doctoral thesis - my avatar is one of the images)


Edited by Don Taylor, 25 December 2019 - 08:55 PM.

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#153 Markus Tang

Markus Tang

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Posted 10 January 2020 - 11:28 PM

Can you post a link to it? I only see the 152 triplet, and 150mm FPL53 doublet...

Well,I heard the manufacturer of that 152 triplet and the APM 152ED is going to launch their own 150ED doublet with FPL53.


Edited by Markus Tang, 10 January 2020 - 11:28 PM.


#154 Corcaroli78

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Posted 14 January 2020 - 04:39 AM

Hi Rudi

 

Don't worry, I'll bring it to the next star party. It's not THAT big and easily fit in my car. 

 

I'll probably need another case or carrying bag, though, as the transport crate it comes in is ENORMOUS and extremely awkward to handle. It should have been fitted with wheels and a handle on the middle for easier handling. Maybe I'll modify it, now that I know I'll keep the scope for a while.

 

 

Clear skies!
Thomas, Denmark

Well.... looking forward to see in person the new scope. It seems that the faithful Telementor will have a rest from Kompedal this year :-)  not enough room for both?

 

Congratulations that everything went well and you enjoy your new scope :-)

 

Carlos




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