Last Weds, I attempted to finely tune my collimation using my 50um artifical star 100feet away, again (for the 5th time). Even after 2 hours of scope cooldown with the observatory door open & dew shield on, I am still suffering from nasty tube currents (see attached). Looking at my last Jupiter image taken before moving to my dome showed much better detail than I am achieving now. Previously, I could see the red spot visually no problem (of course in 2004 it was higher in the sky). Since my local seeing improves with a dew shield and having the observatory door open, I have to conclude that my 3+ tons of concrete foundation/base are retaining heat and slowly radiating it up to the scope affecting the tube currents. Next time out, I will use a floor fan to pull the air across the scope and floor out the door. Using this setup 2 hours earlier and maybe leaving the fan on should help. All this recent talk of air conditioners is making me think that besides observing comfort, the AC may be reducing tube currents as well. There's a lot to be said about not having sweat drip onto your 8.8mm eyepiece when observing Jupiter...
I think the roll off roofs have a big advantage here with tube currents since the entire area is open to the ambient. Does anyone else suffer from these currents and what do you do? I may have over-engineered the concrete and killed my own seeing...
Regards,
Steve
I think the roll off roofs have a big advantage here with tube currents since the entire area is open to the ambient. Does anyone else suffer from these currents and what do you do? I may have over-engineered the concrete and killed my own seeing...
Regards,
Steve
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