Posted 20 September 2009 - 09:16 PM
Alas, I'm not one of them. My observatory is elevated about three feet, but it's also located in a shallow valley. My seeing isn't the greatest in the world. But hey, I actually HAVE an observatory, which is way better than not.
Posted 28 September 2009 - 07:48 AM
I suspect that if you build underground, you'll regret it for a long time to come. Sorry to be a downer.
Posted 29 September 2009 - 12:02 PM
Unless you have it in a really arid climate, you are going to have huge issues with humidity... There is no way to really avoid this.
the deeper your hole/walls, the colder it will naturally be (unless you simultaneously heat it)... this causes relative humidity to skyrocket. If you dehumidify, that heats it in the process...
Depending on how rapidly the air in the underground space is (or can be) exposed to outside airflows will determine if you will get so humid as to actually reach saturation and the resultant condensation - on every surface...
Even Super Insulating is not going to help you, because, unless you can super insulate AND also make it 100% airtight (versus outside air) - the outside air (warmer and therefore carrying higher moisture content) will get in and be exposed to the colder area below ground... and raise RH and/or condense...
And, you don't want to have a 100% airtight observatory anyways - defeats one of the main points - instant acclimation to ambient temp... You've got two conflicting requirements with such a design.
Here's a real world datapoint: I built a super insulated wine cellar in my 8' deep basement. It has R90+ insulation in the ceiling, and R68+ in the walls. Full vapor barrier. Exposed concrete floor inside (so has a heat "sink" at deep earth ambient temperature, which here in MA is around 55F).
In Winter, the air temperature stabilizes at a low of 57F, in Summer, it gradually peaks at a high of 63F; with gentle swings in fall and spring to/from those values...
The humidity varies from 80% in summer, to around 55% in winter. This is totally passive, and with COMPLETE vapor barrier (and double doors as well!).
Not a telescope friendly climate:
Too humid and NEVER at ambient to outside...
Sorry, I just don't think having the actual observatory be undergound makes any kind of sense...
It would only work if you had very highly regulated HVAC control of temperature and humidity, AND also had massive insulation...
Why bother??? Uber-expensive, fiddly, etc...
Sorry to "rain" on the idea parade...
Again, this only applies to areas that HAVE humidity and temperature swings... it might work out ok in Arizona, New Mexico, Nevada, Utah and other places similar...
clear enough skies
How do you handle the humidity in your cellar?
Humidity in a Wine cellar is a GOOD thing; the higher the better... what you do NOT want is condensation...
Pretty much the once a day ingress/egress to snag a bottle probably mixes enough air (even with dual air-locked doors 36" apart) to ensure that it would never get out of control.
In the main part of my basement, however, I run de-humidifiers from about March through October... else IT gets too humid, and there's lots of stuff down there that does NOT like high humidity!
clear enough skies
Posted 17 November 2011 - 01:05 AM
Now all I have to do is to make the roof for the warm room and the dome for the observatory. That's the project for the winter.
About the condensation on the walls: I've added some large-diameter pipes with automated venting units to wipe humid air out of the room, and some other tricks to prevent humidity.
I don't have a pier, because I will use my custom horseshoe mount in the dome, so no need for a pier.
Posted 17 November 2011 - 09:37 AM
Very often the air responsible for bad seeing is close to the ground, so this would make that worse. Look up the Stellar Cellar- built because of an unreasonable HOA.
Posted 17 November 2011 - 10:59 AM
Heck, you even wore your yellow lab out!
Thanks for the great update, we are anxious to keep following your progress!
Posted 17 November 2011 - 12:14 PM
Posted 17 November 2011 - 03:18 PM
About the amount of concrete: I carried up the hill about 6.5 tons of concrete sofar, climbing about 20000 steps (and another 20000 on the way back), walked about 40 kilometers, and climbed a mountain about 5000m high (and back down).
The stats are also valid for my dog, because he was my only workmate (well okay, he carried no concrete at all), following me with every turn.
I'll start creating my pipe-bending machine next week, as I plan to have an all metal 4 meter dome.
Btw, the name of the observatory is Talpa Minor, because it sounds constellationish, but in latin it means "Little Mole", and comes from a Czech cartoon: http://en.wikipedia....iler_character)
Posted 18 November 2011 - 11:54 AM
I consider myself to be ambitious, but your effort makes me feel lazy!!! You carried 6.5 tons of mix up a hill in a bucket??!!!
I really hope the end result is good for you.
Good luck AND KEEP US POSTED
Posted 20 November 2011 - 12:20 PM
The Stellar Cellar
To borrow a phrase from the real estate business, whether it will work depends entirely on three things: location, location, location.
I live in the desert southwest. I didn't have to worry about ground water or humidity. I did have to make sure there was adequate drainage (we can get heavy rains in our monsoon season), but that was really the only major consideration. BTW, the Stellar Cellar made it through the monsoon this summer completely dry.
Posted 22 May 2012 - 11:49 AM
The dome structure (cca. 12.5 feet in diameter) is now about 2/3 part ready, but I had to stop welding because of heavy rains this week. The rusty bit of metal is only temporarily welded to the dome slit to maintain position until the structure is ready.
I've already had a rotating mechanism, but it is now removed as I plan to change it to a more sturdy one and waiting for parts to come in. The structure will be covered with 1.5mm thick metal sheets, and I still hesitate about the opening style of the dome slit.
So, this is my keyhole to the universe:
If I should post elsewhere, pls let me know.
Posted 23 May 2012 - 01:08 PM
Posted 24 May 2012 - 09:18 PM
Posted 25 May 2012 - 09:21 AM
I'm still not sure why there is the urge to go underground for observatories. I typically look for reasons difficult solutions are necessary.
Have a plan in your back pocket to make it into a basement.
Posted 21 June 2013 - 12:40 PM
I was worried that the large metal will scoop heat from the Sun (and it really does), but it seems that the ground in fact does its job, and keeps the dome pretty cool.
Posted 21 June 2013 - 04:56 PM
We'd love to see some pictures of the interior!
Posted 21 June 2013 - 06:01 PM