Obs conversion back on track.

[centroid]

After coming up with a somewhat innovative, if not strange looking (as below ), solution to imaging on windy nights, a recent enquiry has put my original concept of converting the RoR obs to one with a rotating turret/dome, has come back 'on-track' (excuse the pun ).

The main 'stumbling block' had been finding a company with the necessary expertise and equipment, to 'cold bend' angle iron into a circle without any kinks or ripples, to make a 'track' for the dome to rotate on. Engineering companies that can bend/form flat or tubular section, are plentiful, but not so for angle iron.

I found two companies( one in Dagenham and the other in Lowestoft) that were prepared make what I wanted, as a 'one off' job. Some weren't interested in little 'one off' jobs for 'joe public'.

I chose the company in Lowestoft, as they did not have a minimum order charge, which was a cheaper option as I would only pay for the material used and the labour charge (two men for 45 mins apparently). The guy I spoke to was extremely helpful and interested in how the ring would be used.

So, today I have ordered a 1.8m dia ring, which will be made from 30mm x 30mm x 5mm (thick) Angle Iron, and the join closed with a weld.

5mm gauge was recommended as it would 'roll' nicely into a circle, without the chance of the sides tending to lean inwards.

My design will be for an eight sided, flat-topped turret, with a sliding hatch on the roof, and a 'drop down' door on one of the octagon sides.

It will rotate on 8 castor wheels.

The plan is to have a 600mm wide aperture, that will extend a scopes width beyond the zenith.

I'll take photos as the project progresses, and 'post' updates in this section of the forum.

Dave

[Dave Moulton]

Dave,

It sound as if you will have your hands full this summer. I built a roll off roof Obsy last summer in the poring rain that was June. I made the thing up as I went along one big plus though is that the sides are that high it is sheltered from the wind. I have still managed to do some imaging in wind approaching 20mph with good results.

Good luck with the project,

Dave

[barkis]

Hi Dave,

When I was planning my dome years and years ago, I too had the same problem of getting a firm to roll angle to a circle. I was told, at the thickness and size I wanted . 3"x3" x 3/8", would mean incremental heating whilst rolling the metal. Too expensive.

I settled on 4"x 3/8" rolled into a 10" ring, with 4x4" plate welded at 90 degree intervals around the ring. These horizontal plates sat on the four walls of the observatory. 4 more right angled plates were welded to those, to facilitate bolting, and securing the ring to the walls.

Of course the Obs. roof was flat, and sealing it to the wall of the ring was quite difficult, and it was an ongoing headache keeping the seal intact. In the end, I got so fed up with leaks, I suspended some guttering under the ring inside the dome, and piped it out through the wall.

into a drain.

I am sure you won't have any problems like that, and you will find being enclosed a much better situation in more ways than one.

Don't forget the lesson Rog's dome taught you. Namely slit aperture , but as you have a SCT, it is not such a big issue.

Good Luck.

Ron.

[centroid]

Hi Dave

I've had my RoR obs for something like 5 1/2 years now, and wind was never a real issue when I was using a 10" LX200GPS. However, since upgrading to a 12" LX200R (last September), with its long focal length (3048mm), there have been several occasions when I've had to stop imaging due the wind affecting the long exposure subs (up to 20 mins).

With a 6.3 Focal Reducer in-line, the focal ratio is still around f/7, and with the H9C attached, the mag is effectively quite high. Thus the tiniest momentary tremor caused by a gust of wind, can ruin 20 mins worth of sub.

Backing onto open farm land, my ops is quite exposed to the wind.

So, the only real answer is to provide the scope with as much wind shielding as possible, and of course the dome will do that. I'm not a great fan of domes, as I do like to see the whole sky, when standing in the obs, and having to keep moving it round during an imaging session could be an irritation. With the RoR, I can leave my scope imaging for hours and not have to worry about remembering to move anything. However, there's 'fors and againsts' with both types of obs, and its a case of 'you can't have your cake and eat it'.

Dave

[Helen]

Shame you can't have a roll-off dome - best of both worlds!!

Helen

[centroid]

Hi Ron,

In my case, the angle iron ring track, will only be a guide for the castors, and not really carrying any weight, so 30x30mm is more than adequate for my purpose.

I could have used 3mm thickness material, but the engineering expert said this would be difficult to roll into a circle without the sides of the angle tending to bend inwards, hence I accepted his recommendation for 5mm material.

The sides of the 'turret' will be clad in the same 'redwood' shiplap as the obs and warmroom, so as to blend in with what's already there. The flat roof and hatch, will be exterior grade plywood. At this stage I'm not sure how to weatherproof this., i.e. roofing felt, preservative, or paint etc.

Also I will have the same issue with the four corners of the obs, as dropping an octagonal dome on a square obs, will leave the four corners open to the sky. So the plan is, to completely cover the open top of the obs, with a sheet of 18mm exterior ply, and then cut out a circle, just inside the circumference of the angle iron ring, allowing access into the dome.

The 'master plan' is to leave the RoR in place, build the dome dome/turret as a complete module, then roll the RoR back off onto its runway, and try the dome for size etc. If things aren't right, then I can still roll the roof back on, while I address any issues with the dome. Once I know, that all will be well, then I remove the RoR, and the 4'x2' framework onto which it rolls off.

Lots to think about, and lots of 'bridges to cross' along the way I guess :?

Dave

[centroid]

Shame you can't have a roll-off dome - best of both worlds!!

Helen

Now there's a thought Helen!!

Dave

[centroid]

Don't forget the lesson Rog's dome taught you. Namely slit aperture , but as you have a SCT, it is not such a big issue.

Good Luck.

Ron.

Ah yes, I forgot to answer that one Ron.

As you say, not so much of a problem with my Fork Mount, but I plan to make the aperture 600mm wide anyway.

Dave

[steppenwolf]

This is a really interesting project ans I am looking forward to following the progress. Having used both a roll-off roof and a rotating dome and aperture, I can see the advantages of both but in the end, my original decision was the right one for ME, I have no regrets - except maybe I should have got the 9 foot one ...... or a 16 foot one would be nice too ........

[centroid]

I have no regrets - except maybe I should have got the 9 foot one ...... or a 16 foot one would be nice too ........

Now there would be the answer to all our problems Steve, and the the best of 'all worlds'.

As constructing an octagonal dome means an awful lot of Mitres to be cut, and fairly accurately too, if the end product is to function properly, I'm considering buying one of these 1600 - 1880W 10" bladed compound mitre saws, as it be a useful tool to have in the resident toolkit anyway.

Dave

[George]

Shame you can't have a roll-off dome - best of both worlds!!

Helen

That wouldent be too hard, you would be effectively subtituting a peak roof for a flat roof with an attached dome, wouldent take much enginnering to put castors on the flat bit. In Daves case its a case of flattening the roof and attaching a dome, I dont see a reason why not to leave it roll off and have the best of both worlds.

blumming hell got me thinking of modifiying my own :shock:

[Helen]

I thought it wasn't a totally daft idea! although I did wonder about getting it rigid enough to be able to take the turning forces....

Helen (who is not even contemplating doing it to her newly-constructed and almost-working properly roll-off!)

[barkis]

I thought it wasn't a totally daft idea! although I did wonder about getting it rigid enough to be able to take the turning forces....

Helen (who is not even contemplating doing it to her newly-constructed and almost-working properly roll-off!)

Did you ever post a pic. of the finished Ob. Helen.? I don't remember seeing one.

Ron.

[centroid]

The project is now underway .

This morning, the 1800W Mitre Saw arrived from 'Screwfix'.

Then I went and bought all the framework timber, and put the new saw to work. The eight sections of the octagonal base ring have now all been cut, with nice neat 22.5 degree Mitres. I have to say that the saw makes for very consistently accurate Mitres, and makes the job quick and easy.

Tomorrow the angle iron ring that I ordered, is being delivered, although due to other commitments, I'll not be doing any work on the 'dome'.

Dave

[Helen]

Did you ever post a pic. of the finished Ob. Helen.? I don't remember seeing one.

Ron.

Thanks for the nudge Ron, my computer was playing up and so I couldn't load the almost-final photos. I'll start another thread...

Helen

[barkis]

I shall be following this modification with a great deal of interest Dave.

If you could post a few progression images as you proceed, It would be appreciated, as I think there will be more interested members than just me.

Cheers.

Ron.