Observatory build - Dob Deck and Closet

[furrysocks2]

Currently, have an 8.5" DIY dobsonian newt for which I hope to build an equatorial platform, and an ST102 on an EQ3-2 which I hope to motorise.

I'm currently reducing ancillary kit for financial reasons - recently had the dob up for sale, but it's going to stay with me for a while - I was being a bit premature. Like to retain just a couple of scopes, some EPs and a camera or two. Both scopes are stored in the garage which is less than ideal (dust, dirt, clutter etc...). Part of my problem is the faff of dragging scopes and kit out and back in again... I'd much prefer to simply be able to go out and observe, and for the kids to be able to do the same perhaps.

I've got a south-facing gable end against which I'm considering building a small observatory at the western end, or at least a fold-back shelter in which to store my scope(s). South should be good for lunar, solar, planets, etc, but there is fair skyglow to the south and no Polaris for aligment. I also lose access to almost all of the circumpolar targets as well as the darkest part of my sky. So being able to relatively easily remove scopes from storage and set up in another location and re-position accurately is a must. That said, seasonal viewing and lunar studies should satisfy me, in place.

If I retain the tripod for portable use and mount the EQ3-2 head on a pier, then the pier must must not foul the range of motion of the dob. I want to minimise footprint of the whole structure, so the walls may not completely encompass the dob's range of motion. If they did, then a pier towards the outer edge might be possible, but on the other hand, a removable pier begins to add subtlety and complexity back into setup and tear down. Ideally, the pier would be under cover so that the head and ideally scope could remain set up after use, even if it then required a tear down to use the dob... that's perhaps just down to obs planning, etc.

Currently gravelled, but happy to strip back an area, dig and pour a base, and frame a floor/shed around it. The dob's got quite a swing to it, OTA is probably 5'6" and sticks out the back of the base a bit, so while it should be easy enough to define the position for the dob base, I expect the floor/decking will need to extend beyond where I want the walls to extend to, unless I go bigger for the sake of having a fixed pier for the eq head beyond the swing of the dob.

Total area available for decking is approx 8' square with the shelter itself being only as large as it needs to be. I suppose the first thing to determine is at what height the floor should be... a step or two up means slightly lower altitudes in the west become observable. With that, I can locate the dob az axis, define a footprint for the overall structure and location for the pier.

 

Early thoughts, acknowledging the limitations for all the effort...

 

 

[furrysocks2]

Approximate swing of the dob below, assuming minimum altitude of 25 degrees (yet to actually check that - 30 could bring things in a little tighter but actually once you're that low you don't need that much clearance to go lower, to be fair).

 

Allowing 6" for wall thickness, in reality probably keep them below 4". Green walls could remain in place but would need to be low enough, or split, for access to lowest elevations. Amber walls instead would be optionally removable, perhaps bi-fold. Gable to the north, fence to the west. The roof would raise up, back against the gable.

Overall, I prefer the amber walls for their smaller footprint, they would secure from the inside before lowering the roof. I might want to mount the pier as close to the SE corner as possible, but wouldn't want to have to remove the head before lowering the roof - removing scope ok-ish. So some thinking to do on heights and clearance. Tarp stowed in the roof for quick deployment. Decking would probably extend to the green lines to provide flat surface for observing chair.

[furrysocks2]

Scope situated 4'3" x 3' from proposed perimeter, base sitting around 4" from gravel, probably lower than I intend the decking to be.

Skimming several house roofs, I can actually get lower than I thought... zenith is a little inaccurate and all northern directions are likely to reduce once a roof is resting back against the gable. East is right, west is left, as if looking down on the obsy from the south.

I couldn't find my compass so I used a clock and a ruler and lined the scope up with the ruler by eye, dial inclinometer friction-fit into one of the alt bearings. No EP, just sighting through the focuser until I determined I was clear of obstructions.

[furrysocks2]

The dob probably doesn't need a very large concrete base really, other than something stable and isolated from the timber floor. I'm having second thoughts as to whether keeping the EQ3-2 set up indoors is perhaps a step too far for such a small space.

So this is perhaps just a dob closet. Which should be build-able in a weekend.

 

On decking and weather proofing... if I just had an area of timber decking, say the full 8'x8', and the dob plinth were to be raised above that, I wonder how best to mount the walls. The gaps between the decking timbers would extend under the walls - I also wonder whether keeping the floor uninsulated with no membrane underneath might aid airflow. 

If bi-fold walls ran on bearings or similar in some alu/steel channel that was low enough that the observing chair could straddle it, then a weather-strip skirt at the bottom of the walls would at least provide some protection from wind-blown debris and water. Water might creep along the boards themselves, but I don't know if that would matter too much. I might well install a temp/humidity logger.

I'm not particularly precious about the scope at this point although that might change if/when I get the mirror recoated.

 

So:

• anchor a runner against the gable wall for floor joists to hang from
• a runner to attach the roof panel to
• uprights anchored to the same wall on which the attach the side walls - one fixed, one bi-fold
• dig in a post for the SW corner to attach the southern bi-fold wall to
• form a base for the dob
• frame up the floor joists and deck it
• then the walls and roof go on top of that

[furrysocks2]

I've got small paving slabs for footings and can get a large paving slab and blocks for dob plinth. Reckon I could frame and deck the base with new wood for £100. Structure on top could be constructed wholly afterwards.

[furrysocks2]

I guess I'm starting with just a "dob deck"... permission sought, a shrug in response. Shame I just sold my nailgun... :/

[Alan White]

Dob Deck sounds a good start, but will this still involve a long drag out of the Dob?

 

[furrysocks2]

19 minutes ago, Alan White said:

Dob Deck sounds a good start, but will this still involve a long drag out of the Dob?

Not for long.

I'll buy wood for the base tomorrow morning, it'll be "a surprise" for my lady when she gets back on Sunday night. 

[furrysocks2]

[furrysocks2]

Just thought... equatorial platform may need a larger footprint than a 2'x2' slab, I don't know as I haven't built one yet.

[Alan White]

11 hours ago, furrysocks2 said:

Not for long.

I'll buy wood for the base tomorrow morning, it'll be "a surprise" for my lady when she gets back on Sunday night. 

This is a sure fire way to discover if it was a shrug of approval or a nervous tick!   

Wish you luck with both the build and reception.

[furrysocks2]

Reception will be better if I get any of the other jobs ticked off my list. Last time she went away, I built her a herb garden... that wasn't on the list.

Wood's ready to go. Can't start until sundown, though... :/

[furrysocks2]

Done before midday.

[Macavity]

Looks very nice indeed! The only thing I might say is that
*Welsh* weather snapped the (plastic) bolt assembly on
my Keter(?) store in two and bent the hinges irreparably! 

But maybe you are a bit luckier with WINDS in Scotland?

[furrysocks2]

Ouch!

I'm sheltered from the prevailing wind by that fence panel.

[furrysocks2]

Thinking about insulation from direct sunlight while I'm repairing gutters... any advice? Clad the inside of the walls and roof in kingspan/celotex, something thin like 12 or 25mm?

Thinking half a dozen vents...

https://www.screwfix.com/p/map-vent-fixed-louvre-vent-with-flyscreen-white-229-x-76mm/5104d

Maybe a solar powered fan?

[furrysocks2]

Took a couple of days for the deck to be mentioned, but the reception was such that I was allowed down to the wood yard earlier to pick up the rest.

First build will be about 1.8m (w) x 1.2m (d) x 1.2m (h). A neat fit for the scope as it is, so the pad may need lowered or sides and top raised when I build the equatorial platform.

Can't start until sun-up, though... :/

[Beulah]

Allowed, LOL. That's it, drip feed the plans... 

 

 

[furrysocks2]

To be fair, I'm making it up as I go along but there is a bit of that, aye! Pretending like I'm not spending too much time thinking about it. Just a quickie.

With the pad located where it is and keeping wall thickness to a minimum, I figure I can stow the scope at 90 degrees to squeeze the build out of 4 sheets of 9mm OSB. Panel re-enforcement with 2x1", a lip round the underside of the top to hold the sides square, with a little 2x3" left over from the deck for securing the back to the wall. Should come in under £200 all in. Some left over paint will colour-match it to the back of the house if there's enough in the tin.

Forecast dry, time to drag the tools out. 

[furrysocks2]

Carcass done.

Still needs vents, roof covering, to be anchored to the wall behind, catches to secure the removable walls, a pulley/catch/prop/etc to raise the roof and such like. But fully closed, while not secure, it's solid enough to sit on and wiggle about.

From fully closed, by lifting the lid just a touch, I can take the bi-fold front wall off and set it aside...

 

Then the lid lifts up, side wall comes off and I'm ready to go.

 

The loss of a good portion of the NW sky over the lowest part of the gable, due to the raised lid, is a pity.

[furrysocks2]

I went through the root of my thumb nail with the impact driver when it slipped off a screw, which was also a pity.

[Alan White]

8 hours ago, furrysocks2 said:

I went through the root of my thumb nail with the impact driver when it slipped off a screw, which was also a pity.

Ouch, I can truly feel your pain.
I trapped my finger between a shock absorber spring a few years ago, did my nail bed in, your quote made my toes curl with the memory.

Swift recovery.

[Charic]

On 24/09/2017 at 14:14, furrysocks2 said:

I'm sheltered from the prevailing wind by that fence panel.

Those Larch panels are something that I have been considering this week, for a simple screen for me and the Dob.
Four would be enough, painted dark oak, or several coats to almost black, a simple fixing in each of the four corners, to quickly erect the unit, when and where?

Failing that, considered just erecting them  to escape the street lighting and the neighbours lights. The gardens to my east are not affected by the street light, the difference is very noticeable.

[furrysocks2]

22 hours ago, Charic said:

Those Larch panels are something that I have been considering this week, for a simple screen for me and the Dob.
Four would be enough, painted dark oak, or several coats to almost black, a simple fixing in each of the four corners, to quickly erect the unit, when and where?

Failing that, considered just erecting them  to escape the street lighting and the neighbours lights. The gardens to my east are not affected by the street light, the difference is very noticeable.

This?

http://www.spacegazer.com/index.asp?pageid=97497

[furrysocks2]

Clear tonight...

Got the back panel secured to the wall and the roof held at one corner with a bit of string - not ideal but safe enough.

Hunting my baader film, sun's out!