Gina's Observatory

[Gina]

Gina - you can always lay a piece of 2 x 1 (or similar) on top of your joists just to give a bit more clearance...

Francis

The top of the pier base was designed to be below the bottom of the joists. In fact if I use 600mm joist centres I can have a joist clear of the RHS of the block and the next one over the LHS of the pier block where there is a good gap (over 10mm). Alternatively I could put pieces of 3x2x1 between beams and joists.

Here is a new diagram of the floor section (rather rough but shows the idea) :-

[Gina]

Just noticed that the webcam image online was not updating (YawCam failure again). I've now re-run YawCam and the image is now up-to-date. I apologise for the interruption to the service. To compensate I'll select a few saved images and post those.

[fwm891]

Gina, 10 mm isn't a lot of space above your pier block especially as a floor of this type is liable to bow down when you walk on it. It might be worth thinking about doubling up the joist across the pier base by putting two side-by-side (you could then reduce the vertical section of the paired joist and put small blocks under either end to restore the height). The rest of the floor area will be fine. It might be a bit belt-n-braces but if you intend walking on the floor while using the scope you don't want a joist bearing even temporarily on the pier base.

Francis

[Gina]

Gina, 10 mm isn't a lot of space above your pier block especially as a floor of this type is liable to bow down when you walk on it. It might be worth thinking about doubling up the joist across the pier base by putting two side-by-side (you could then reduce the vertical section of the paired joist and put small blocks under either end to restore the height). The rest of the floor area will be fine. It might be a bit belt-n-braces but if you intend walking on the floor while using the scope you don't want a joist bearing even temporarily on the pier base.

Francis

That sounds a good plan - thank you

[Gina]

Photos of today's progress. floor beams in place with DPC between them and the concrete :-

1 & 2. Viewed from different angles.

3. Took cover off pier and mount.

4. Showing wall ties to be used to secure beams to the concrete blocks - to stop the shed blowing away in a gale (These are on both sides of each beam and at both ends).

[Gina]

Just been out and placed a 5x2 plank where the joist would go over the pier base to measure the actual gap. The minimum gap is actually just over 20mm. While I was there I decided to see how much the plank (on edge like a joist) moved when I jumped up and down on it in the middle. It hardly moved at all certainly nowhere near 10 or 20mm. So I think it will be fine as in the design above.

[Gina]

As promised, some enhanced images from part of the saved webcam images :-

1. Cutting the DPC.

2. Laying beam in position.

3. Laying the DPC into position.

4. Third and last beam being put in position.

5. Adjusting the DPC.

[Astrokev]

Looking good Gina, but please could you tell me what the blue and white "bucket" is in the background? It's been there since you started your digging and never seems to move! My curiosity has gotten the better of me, so had to ask !

[yesyes]

That's the rain gauge for the weather station I assume...

[Gina]

That's the rain gauge for the weather station I assume...

Correct

[Astrokev]

Ah, thanks. Curiosity satisfied!

[Gina]

The blue part is a 10" funnel which collects the rain drops and directs them into a tipping bucket type rain gauge. The white part is an inverted cattle lick bucket with the bottom cut out leaving an outer shell just the right size to take the top of the funnel and hold it in place. The collection area of this gauge is a bit bigger than most and the gauge responds to the lightest shower.

Talking of rain... that's what it's doing now I'm also expecting it to be yet another cloudy night with no chance of seeing any celestial objects That's if it's not actually raining!

A few days ago I put the mount on the pier (as I said in a post somewhere above). Not only to make it look better and show some progress but also thinking I might get a clear sky and to try a polar alignment. Ha ha... fat chance. Every night since has been cloudy.

[Gina]

Sunny spells and cloud today

Checking spacing and clearance of joists - here are a couple of photos showing two pieces of 5x2 joist in the positions of two of the joists I shall be using (new pressure treated timber of the same size). These are spaced at 600mm and the floor will use 5 joists with the thicker (25mm) floor boards. I'll attach a diagram.

1. View from north side showing gap under joist.

2. View from west side showing position of the two joists nearest the pier base.

3. Diagram showing the latest design of the floor frame. The joist spacing is actually 588mm, ie. slightly less than 600.

[Gina]

Put my little scope on the mount and tried various alignments. At the same time measured up the wall height to give clearance of view. Placed a short piece of floor board on the joists to get the floor height (roughly because the floor board I used was thinner than the ones I'm getting). BTW, I jumped up and down on that board and it only moved a little

Some photos :-

1. Scope aimed at distant test tree and almost exactly horizontal. The southern horizon is a few degrees above this.

2. Scope turned over and again aimed at the tree.

3. Scope aimed towards polar axis.

4. Photo showing the tree taken at 70mm focal length with DSLR. (Pointed to by arrow.)

[fwm891]

Looking really good Gina - I can only dream of horizons like that !

Clear skies. Francis

[Gina]

Taken a couple of terrestrial images with scope and DSLR. Tried to do some solar but the clouds keep getting in the way. The sunny spells are too brief

Must say the scope and camera feel very much more stable on the pier I can focus without moving the image. And these images were taken without camera remote release.

Images attached :-

1. Unmodified image of tree.

2. Image enhanced in GIMP.

3. Image of comms tower on far hill.

4. As above but enhanced.

[yesyes]

Aaww, nice image of the famous Tree Top Nebula..

[martin_h]

Just looking at your web cam...can you send some of that blue sky oop norf please.

[Earl]

Is that a scope i see set up now !!!!

Go Gina Go Gina

[Gina]

Aaww, nice image of the famous Tree Top Nebula..

Hehe

Just looking at your web cam...can you send some of that blue sky oop norf please.

Not a lot of it here - but it's a pity we can't send weather to other parts. eg. Australia was dying for rain when we had too much!!

Is that a scope i see set up now !!!!

Go Gina Go Gina

Yep! Scope on mount and it feels really solid on that mount and pier We might just get a clear night tonight but with so many lumps of timber about to trip over I think I might be wise to leave night play until I've got the floor down. But I'll see how I feel about that when it gets dark

Tomorrow, if we get sunshine I might set up again for solar imaging. Power up the mount, line up the sun and set for lunar tracking. I think the polar alignment is probably near enough for that. At least I should be able to get some DSLR images. Might even take my laptop out to the site and try some webcam images. Otherwise I really want the obsy and warm room built before doing any night-time imaging.

[malc-c]

Just watch yourself Gina, I thought about setting up the scope one night whilst in mid build but the thought of moving around a scope on a building site in the dark put me off... too many chances to trip over and hurt oneself !

That mount looks really good on the pier... well done

[Gina]

Just watch yourself Gina, I thought about setting up the scope one night whilst in mid build but the thought of moving around a scope on a building site in the dark put me off... too many chances to trip over and hurt oneself !

Yes, I agree, it's just not worth the risk.

That mount looks really good on the pier... well done

Thank you I'm really pleased with it

I think I've upset the weather with mentioning setting up for solar imaging today! The nice sunny day forecast hasn't materialised - it's overcast, dull and drizzly instead!

[Gina]

Been measuring the heights I need to make the walls to maximise the viewing angles. I seem to have lost about 3" off the designed height of the pier. I know where most of it has gone. I'm using 5x2 rather than 4x2 joists and 1" floor boards instead of half inch plywood. That's 1.5". Then when I was pouring and prodding the pier concrete the threaded rods moved down slightly so the concrete didn't come right up to the top of the tube. That probably accounts for another inch.

Now the side and east end walls I can make lower though this makes the roll off section higher, heavier and a bit less rigid. To the west(ish) will be the roll off roof which can't be any lower. I've calculated that the lowest angle of view will now be about 30 degrees whereas the trees and houses would allow 15 to 20 degrees.

I could alter my mount adapter to have a greater space between the steel plates by replacing the nuts, bolts and washers with threaded rod and nuts, as some others here have used. This might reduce the rigidity a bit. The holes are 15mm and I'm using M14 bolts ATM. So I'd be using M14 threaded rod on about a 4" radius. Having gained extreme rigidity I'm a bit loathe to throw any of it away.

I'd be interested in your opinions, please.

[Freff]

Hi Gina, sorry to hear your dilemma.

I thinks that adjusting the mount may be the easiest method.

This is the way I have done it and I have a propensity to over engineer things. I used 4 x 16mm high tensile steel tow hitch bolts which has made my setup very rigid indeed. I have welded one end into the top plate adding that bit of extra rigidity and keeping the top plate clear.

I think the bigger nuts my foul your pier if you go this way, and you may have to do it in reverse.

This has given me about 4" space between plates which I think is about what you've lost.

[fwm891]

Gina, That's a shame. I would go with the enlarged roll off roof and lower your fixed walls to allow your 15º FOV. You can easily strengthen the run-off roof parts with plywood gusset pieces. They will provide stiffness without increasing the weight significantly. It would be financially cheaper and easier to construct. Francis