Calculating wall height for roll of roof observatory question.

[bluesilver (Peter)]

Hi, Just a bit of a basic math question that i am sure i am over thinking.
I have came across this document for calculating wall height for an observatory, it basically works on a 25 degree angle which i think is a good number, I think going below 25 degrees you end up in too much atmosphere ( any comment on this would be appreciated ) The shed is out in a pretty open area, so not much in the way of tress, houses
http://astronomy.mdodd.com/files/Cal...all_Height.pdf

My shed is going to be 3m X 3m
Pier dead center and a height of 950 mm
I am just trying to work out with that document link above, if the height ( given as Hscope ) is just the height of the counter balance shaft when it is at horizontal?

If so, my mount is about 360 tall when the counter balance shaft is at horizontal.
So that makes the Hscope height a total of 1310mm

Putting it all together, 25 degrees ( 0.466 ) X 1500 mm ( Centre of shed to wall ) = 699 mm + 1310 (Hscope ) = 2009 mm Height of wall

So in summary, if this Hscope is the height of the counter weight shaft, then my wall height can be at a maximum of 2 meters tall.

Dose all this sound about correct?
Sorry for the long drawn out question here,
But any advice would be appreciated.
Thanks.

[glend (Glen)]

Hmm, well are you planning on imaging? Most experienced imagers avoid starting up on any object below 40 degrees, for the usual reasons: thick atmo to shoot through, more light scatter from towns, street lights, etc.
Secondly, mount height may not always be the same, as you may buy a different mount, etc. Consider whether your using a tradition mount cage on top of the pier. Will you be using any sort of riser dovetail setup etc. Many factors affect the height of your scope.
I tend to favour having the equipment sitting down inside the walls, as it seems to create a stable environment and discourage dew and whatever wind maybe around to push on a scope.
Just a few thoughts based on my experience.

[bluesilver (Peter)]

Appreciate the reply,
Yes, i have left a fair bit out of the original question, I guess i wasn't trying to make it too complicated.
But yes, I am setting it up for imaging, but not remotely, I still want to go out and set it up and running, let it run and do it's imaging while i go back inside, and come out latter, close it all down, shut everything off manually.

I am in Borlte 2 area, shed will be a good 50 meters or more away from trees, houses.

I am building my own pier, so no cage onto, mount will bolt directly to pier without any spacing.

Scope is a Skywatcher Esprit 150, mount iOptron CEM120
So total height of mount with counter weight shaft horizontal is 1310 mm
25 degrees from this height puts the wall height at 2 meters.

Mount will sit at a home position with counter weight bar sitting horizontal.

So it is sounding so far that my plan of a 2 meter wall height will be fine so far, this means that 25 degrees is the minimum elevation i can image targets at.

[glend (Glen)]

How are you building the walls? Is the site flat, building on a slope? My obsdrvatory is on a sloped site, build on timber posts. Pier rises through the floor, without touching the structure. If your building using timber, consider the standard timber lengths available locally. Have fun.

[bluesilver (Peter)]

Site is reasonably flat, Concrete floor and the pier will be separate from the concrete floor.
The walls will be just some 50 x50 duragal posts with 90 x 45 treated pine and with roofing iron screwed onto the side.
Will start a thread on it once i get things sorted

[LonelySpoon (Neville)]

Have you considered what orientation you will park the scope at?

If you park it horizontally, facing East/West, you can raise the height of the pier/pad by the difference in a N/S park where the scope pokes up at the SCP.

You should get a few more degrees 'downwards' that way...

I designed my walls to allow my scope, on an EQ8, to get down to 15 degrees with 2m walls. Just built the concrete pad up appropriately.

I currently have a dome on top, but allowed for the possibility of making it a ROR.

Neville
LSO

[Startrek (Martin)]

Peter,
Good luck with your ROR Obs
You must be champing at the bit to get started
It’s very satisfying having your rig installed permanently, polar aligned and ready to image
One suggestion if I may , you mentioned about setting up ( I presume imaging gear only ) running an imaging session and then shutting down. This is what I do at my South Coast NexDome , however I ran 2 x Cat 5e cables ( 1 active and 1 spare ) from the house to the Dome ( approx 30m ) and this allows me to control and check on the imaging session from the house ( my study ) using Windows 10 Remote Desktop. All you need is a second lappy ( cheap one ). It works beautifully , so far no drop outs of issues in the past 18 months.
It does save walking out to the Dome , especially in the winter months and tweaking things if needed or if cloud rolls in for half an hour or so.
I don’t know how far your Obs will be from your house but you can run Cat 5e data cable up to 90m
Well worth installing it ( even if you don’t use it straight away)

Clear Skies
Martin

[bluesilver (Peter)]

Appreciate all the replies and advice, open to any suggestions.
I already have my pier built, i kind of got some metal from work before it was thrown out, so was limited to it being 950 mm tall.
But it is 8" schedule 40 pie, so decent wall thickness and a 1" pressure flange for the base.
I am not sure i would want to image below 25 degrees, but a 1800 wall height will let me get to 19 degrees.
For the park position, I was just going to go from the polar aligned position and then just go 90 degrees east so that counter weight shat is horizontal.

The cat 5 cable is a very good idea, I already have 240v out there as i run soil heating cable in a garden patch where i grow giant pumpkins for competition, the observatory is going to go in the back corner of this patch.
I would have to measure the distance it is from the house for the cat 5 cable, I don't think it is 90m, but would be getting close.

Either that on run it off Wi-Fi possibly? not really up with that part, will have to research more into it.

Shutting it down, I just mean, put the mount in park position, turn the power off, take the laptop back inside.

Definitely keen to get started, takes a good 3/4 hour now to drag everything out and setup in my current observing site the driveway, plus the weight of the mount doesn't get any lighter.
Will take some time as i only get about a few hours each 3rd week + weekends due to shift work.

Just about got things drawn up ready to go out and get the items required.