Is Rooftop A Good Idea?

Blondeb3 (Geoff) · #1 13-12-2011, 08:43 AM

Brand Newbie here - picking up a telescope this weekend and wondering if it's worth planning a viewing space in my roof since I have to peel off roofing sheets in the near future for renovations - perhaps I could build a space into my roof with a panel that can be opened for viewing. It's a timber house in the country. Is this practical or would the house frame allow too much vibration?

rainwatcher (Peter) · #2 13-12-2011, 09:37 AM

Generally not a good idea. Can you convince the missus to let you put a pier right down through the roof and the room below to a concrete slab in the soil through the house, might make an intersting dinner table centre ornament.

More seriously, some people do put long piers down but they also have to be appropriately rigid. Easier and better to build a little obervatory out the back. Brendan Mitchell, I think, has some posts on pier analysis.

Keltik (Trevor) · #3 13-12-2011, 10:13 AM

Having done a bit of work in our roofspace recently, I would agree with Peter, but for slightly different reasons. Even a well-ventilated roofspace gathers much more heat than the rest of the house, (it's nearly stifling under ours, even when the sun isn't that strong) and you would have big issues with air turbulence as that warm air vents through your skylight. If you're using a Newtonian, I would think it would take a prohibitively long time for your mirror to achieve thermal equilibrium.

jenchris (Jennifer) · #4 13-12-2011, 10:24 AM

I'd go with Trevor's case first and Peter's second.
particularly if you have a brick exterior - the heat from brickwork will make it a very difficult early evening!!

barx1963 (Malcolm) · #5 13-12-2011, 01:42 PM

For purely visual vibrations might not be too bad depending upon the structure of the framing etc. but for imaging would need pretty major work. BUT I agree that heat is more of an issue. Even on night following quite cool days the view over my house is severely degraded from rising heat.

What type of scope have you ordered?

Malcolm

bmitchell82 (Brendan) · #6 13-12-2011, 02:41 PM

There have been plenty of observatories that have been put into houses. Heat haze can be mitigated depending on the type of materials that you have already, eg tin roof although it gets stinking hot during the day it has an extremely low thermal mass and will release the heat its gained from the day in no time at all.

If you have bricks around, then your in a bit of bother as they hold heat really well! and hence why they are generally used as a building medium.

Are you wanting to get into astrophotography if not a nice little deck out the back somewhere is a far better/cheaper option. If your looking to go to astrophotography, its a different ball game.

I have done analysis on the different sections and which one proforms the best and they can be found here

Keltik (Trevor) · #7 13-12-2011, 03:34 PM

Some interesting stuff here Geoff. The gist of some of these posts suggests that if you do try for an observatory as part of your house, you have to put in a good deal more infrastructure than just a skylight. One gentleman from Texas seems to have the observatory completely thermally isolated from the house proper, others suggest some form of aircon to bring the area down to isothermy with the outside. Sounds very complex....

Blondeb3 (Geoff) · #8 15-12-2011, 05:39 AM

wow, what a bunch of great replies! Thanks for all the information guys it's great getting such a good range of responses, now I've got some serious reading to do starting with the rooftop design stuff, thanks Trevor, and then Brendan's Pier Design stuff. I think I'll start with viewing from the front verandah just on a tripod - I bought a Meade ETX105 for starters and then I might get more serious with a dob but no plans for astrophotography yet. I'm still considering the ceiling space thing but lots of factors to take into account from what I see here, so I doubt peeling back some roof and installing a flip up panel is going to give me good results in an old timber house. My other thought is to build something on top of our concrete water tank since it has a concrete roof supported by a good diameter pillar up the centre. Should be stable and strong enough to build a practical structure on top, I think the pillar up the centre is about 12" in diameter from memory - does that sound practical, on top of a concrete water tank for a small backyard structure?

ZeroID (Brent) · #9 15-12-2011, 07:39 AM

What are you gaining by elevating your observing position ? Does it let you improve your horizon limits ? Most observing is done as near to straight up as possible. The lower you go the more air you are looking through and the more turbulence so most observing is normally above the 30 degree mark up to zenith.

Some one else pushed a water tank top build before. The comments if I remember correctly were about the rigidity and stabilty of the structure ( a 12" internal pillar helps ) but again also about thermal mass. Large concrete structures maintain their temperature for long periods especially if they are full of water, also a good thermal mass.

If it is just for a stable platform for visual and it is solid enough and gains you some viewing room over trees etc then give it a go. Chuck the tripod up there and see how it works for you. For testing it does not have to be permanent and it costs nothing to try.

Let us know how it works ..

Cheers
Brent

bmitchell82 (Brendan) · #10 15-12-2011, 01:31 PM

the post in the center is probably alright, but i wouldn't be going up there as the concrete lid will not be designed to take the load. if its just yourself you should be right, but if your going to get your tribe up there be warey!

The best place for it I would say is down on the ground that way you don't have to lugg everything up to a high level. It also helps if your observing later in the evening when it is dark!

Thats just my little piece of thoughs on the situation.

graham.hobart (Graham stevens) · #11 07-01-2012, 01:48 AM

from my point of view, I have no choice but to image from a wooden deck and have compensated quite well with this. Some old thongs make great vibration pads, and if you start to image you can do what I do- put some pauses between frames to allow yourself or the mount to settle, don't move around when taking exposures so get yourself an old armchair or something from the tip shop and recline with binoculars while you are shooting!
My deck has the advantages of great drainage so no dewy feet on those cold nights. Don't write off your veranda to start with. Just compensate for the vibrations and allow for them. Give it a go anyway.
Alternatives are much more expensive!
Graham