Observatory progress

[ChrisM]

I've just been reading about a few others' observatory projects so thought I'd post a brief update on my efforts thus far: (my day job keeps getting in the way...)


Pier and slab poured Aug 07 - 457 mm dia RC
Geodesic dome constructed Jan 08 - 3.6 m dia. plywood
Turntable constructed March 08 - 100 x 50 ply, with rolled 75 x 75 x 6 angle
Building constructed June 08 - circular, stud frame, mini-orb cladding, with observing floor 2.2 m above slab.
Dome lifted into place Aug 08
Current works: weather sealing (it's been an excellent spring season here to thoroughly test it!)
Still to do: stairs, power, lighting & comms, pier extension (steel pipe), fixed wedgeChris

[acropolite]

Impressive work Chris, looks like a "proper" observatory. Keep the photo's coming.:thumbsup:

[[1ponders]]

That look excellent Chris. As Phil says it really looks like the real thing. Unlike some hilton garden sheds being built around here :lol:

[h0ughy]

:prey2: :prey2: :jawdrop: :2thumbs: :bowdown: oh how awesome and splendid is that!!!! Chris its wonderful:thumbsup:

[sheeny]

Impressive!:thumbsup:

Al.

[Matty P]

An awesome looking observatory Chris. :) Looks very well thought out.

Thanks for sharing.

[ChrisM]

Thanks all, for the positive feedback. We decided to go with a classical design since the observatory is pretty much on our front lawn.and therefore has to "look the part". The project has taken a lot more time than I first envisaged, after my wife suggested that "we could build an observatory"! (Mind you - that's the only prompting that I needed.)

I've attached a few pictures of the pier construction. The block supporting the pier comprises 2 cubic metres of 25 MPa concrete, and is well reinforced (I achieved the 1% steel (by volume) as per the Australian Standard). Into the top of the pier are inserted 8 off 12 x 300 mm galvanised bolts that will connect to the steel pier flange.

Like others have suggested with their observatories, the design of mine allows for future expansion (the universe is still expanding) however I'm still considering what equipment I might upgrade to down the track.

Chris

[rsbfoto]

Hi Chris,

Great images to see how such a nice Observatory is growing. :thumbsup:

[I.C.D]

Chris,
Well done what and awesome job I think I can see how you paid for it, did you find the pot of gold at the end of of the rainbow( fourth photo)clear skies and good viewing with the new observatory

Ian C :2thumbs:

[leon]

Wow, that is an awesome construction, :eyepop: and will serve you well into the future, fantastic job, I bet you are stoked with thew finished results, ;)

Leon :thumbsup:

[Ric]

Wonderful work Chris, that view of the sky with the pier looks awesome.

[ChrisM]

It’s been a while since the last update:
The observatory work room (with desk) is now complete with a few creature comforts. I upgraded the old hard stool to a comfy chair, and have wall-mounted the PC monitors and tidied up most of the cabling. On the wall there is a video monitor to keep tabs on the scope, a sound system, and some 2m & 70cm radio comms. A set of drawers allowed me to clean up most of the loose bits of paper, equipment and tools.

Upstairs I’ve added an ED80 to the SCT, and have a TV monitor for the GSTAR-EX, which is very handy when we have a small group of visitors.

All I need now is more spare time - and for it to coincide with clear skies…..
Chris

[seeker372011]

awesome. truly awesome.

[allan gould]

What a wonderful observatory. Impressive comes easily to mind. Enjoy the fruits of all your hard work.

[DavidTrap]

Looks magnificent! Couple of questions: What are the walls downstairs lined with? Do you have problems with your chair banging into the pier?

DT

[ChrisM]

All, Thanks for the comments.

David, the downstairs walls are lined with some old wall panelling that the local hardware had; not sure of its name, but it's similar to what I recall Atco Huts being lined with. It has a false wood grain finish, and is bascially a thin three-ply which bends easily.

Yes - there isn't much spare room with the chair and the pier, but I'm not seriously imaging yet so haven't had a problem. The pier is solid enough for it not to worry anybody visually observing.

Chris

[AstroJunk]

Now THAT's an observatory :thumbsup:

[Ric]

I just caught up with your latest pictures Chris, truly awesome work.

It's a work of art. :thumbsup:

[renormalised]

Very nice job...that's a LX90 you have there, isn't it??

I like the control room...quite comfy:):)

[bert]

That is an impressive piece of work. Now go out and use it!

Looks as good as if not better than a bought one.

Brett

[astroron]

What a work of art, looks better than a professional observatory.
Awesome

[ChrisM]

Thanks for the compliments guys. The materials cost far less than the cost of "a bought one" but I did invest hundreds of hours of my own time.

However, the result has made an amazing difference to my observing time. Previously, setting up the LX90 on the tripod on the front lawn would happen about twice a month (if that), whereas now I observe up to three or four times a week (eight times this month so far) and it takes just 5 minutes to be underway.

Chris

[spearo]

Beautiful work Chris
Quite the achievement!
well done
frank

[bloodhound31]

This is the most amazing observatory I have ever seen! I am actually close to tears. I want to pull mine down and start again!!

Beautiful, skilled, professional job there mate! Big salute!

Baz.

[Ric]

Hi Chris, out of interest did you have to get council approval or anything like that?

I spoke with my local council once and as much as I tried to explain to them what it was all I got was the old "rabbit in the headlights" stare back at me. Their comment eventually was that it sounds like a garden shed for which I don't need approval, that is fine with me.

Cheers

[ChrisM]

Hi Ric,

A probing question, and the short answer is no.

I went to the local council office first to enquire whether I would need a planning permit, and since I live on a few acres with lots of trees, the neighbours were not going to be visually affected by the construction, so the simple answer was that no Planning Permit was needed. (Some years previously, I did have to obtain a Planning Permit for a tower that I erected here.) I think that they also asked about project cost, and at the time I thought that it would be well under the figure that they stated.

However, I then asked about a building permit. This function was outsourced from the Council so I rang around a number of building surveyors. My enquiries were met with widely-varying answers. Finally, I found one who was actively looking to help me proceed without the need for a permit. I don't know why the others did not follow the same rules, or even themselves have a consistent approach.

The criteria that the project had to meet (to not need a building permit) were:


Does not need a Planning Permit
Walls not greater than 3 m high (this doesn't include the dome)
Is not built of masonry
Is not more than 10 square metres in plan
Can be called a "shed" (which of course it is)

Apart from the extra cost of a permit ($450 min), I am sure glad that I did not have to debate the plan for this circular construction.

Chris

[ChrisM]

Baz, your own obs is a nice piece of work too, and an encouragement to many others.

Chris

[Scorpius51]

Chris

That is brilliant! Well done and great viewing to you. It's inspiring, but it's also not going to happen for me - at least not at that level.

Cheers
John

[sheeny]

I'll see my previous "impressive" and raise it two "very"s!

Wow!:)

Al.

[RB]

Incredible !!!
Excellent work Chris.

:scared2:

[ausastronomer]

Excellent job Chris,

That is actually a very similar design to one of Steven Lee's private observatories near Coonabarabran. The only difference being Steve's "dome" houses a 20" dob and doesn't have the pier. Having been built many years ago, the downstairs section of Steve's observatory has now accumulated an amazing collection of homebuilt telescopes and ATM parts, as opposed to your computer setup. Steve actually has his imaging setup in a roll off roof observatory.

Cheers,
John B

[Brettstar6754]

I like it!

Building Observatories is just a great thing.

Cheers,
Brett

[TrevorW]

Excellent obs

[pgc hunter]

What a beautiful observatory. You are living the dream!

[Rex]

Wow, that gives a hole new meaning to going to the shed. What an observatory, truely amazing.

[bloodhound31]

Do you have a website yet Chris?

[ChrisM]

Not yet Barry - it's a bit like the obs construction project: it took a couple of years. I'll give a yell when it's up and going.

Cheers, Chris

[cybereye]

I've just discovered this thread. OMG!!! WOW!!!

Cheers,
Mario

PSI wonder if I should show the pictures in this thread to my wife....

[RobF]

Wow. Certainly a very impressive construction for an amateur observatory - looks very professional.

[netwolf]

An amazing work of art. Defintely no shed.

Regards
Fahim

[SMan]

:jawdrop:
You need to publish that in "Better Homes and Observatories" or something...that is just stunning.

[ChrisM]

Thanks Henryk and others for the positive feedback. The only thing missing recently has been a clear sky. As for publishing an article, the thought had crossed my mind - maybe something for the IIS projects department.

I'm still considering motorising the dome and will be aiming for a low-profile non-clunky solution.

Chris

[ChrisM]

Seeing Robin's latest pics prompted me to dig out a few dome construction pics, which I had omitted to include in this thread.

Basic details: I used the Desert Domes Calculator with 3V "fineness" and a 3.6 metre diameter. http://www.desertdomes.com/domecalc.html
The geodesic dome uses 105 triangles from 9 mm exterior ply. Edges were beveled by hand plane and joined with liquid nails and plywood hubs (to suit the pentagonal or hexagonal shapes) fixed by screws.

As others have found, it's easier to start construction upside down. Due to the weight and size, I turned it up the right way before it got too big and heavy. The finished weight was about 90 kg although this increased to around 220 kg once the dome ring and steel turntable ring were added.

All joints were sealed with ample Sikaflex and painted externally with a very thick Solagard. The inside was painted with a mould-resistant black paint.

Chris

[ChrisM]

A few more pics.

I projected a vertical laser line to mark out the cut lines for the aperture. Something like 2 days to mark it out and 20 minutes to do the cut!

The shutter (Mk II) comprises two curved plywood side pieces, spaced apart by three lengths of 10 mm threaded rod. I fixed 35 mm bearings to each end of each rod; these ride on aluminium strips fixed to the top of the aperture frame. The tracks are extended beyond the frame using 6 mm threaded rod as standoffs. This was a bit fiddly but it works well. I first tried thin plywood sheet as the shutter surface, but the join was unsuccessful. The final version uses 0.55 mm sign-white sheet metal. Since a full-length shutter can't be parked, the lower 0.5 m of the aperture is covered by a hinged shutter that doesn't normally need to be opened.

Chris

[issdaol]

Beautiful setup mate :thumbsup:

[ChrisM]

A late afternoon pic today shows the sheet metal weather seal, and the aluminium shutter tracks. Fabrication of the weather seal was complicated because I forgot to make the diameter of the walls a little less than that of the dome. Therefore, the seal, which is attached to the dome, needed a step so that it would clear the walls. Truth be known, it could have done with a larger step as it binds occasionally - depending on the temperature.

Chris

[h0ughy]

very picturesque - you could try a silicone spray to keep it moving smoothly - i use some on my dome

[ChrisM]

Now that is a good idea. Thanks David. I'll have to give it a try.

Chris

[ChrisM]

I eventually tried the silicone spray today, and it has worked a treat! Much smoother and quieter running. Thanks h0ughy.

[bloodhound31]

Hey Chris, can I ask, did you get this idea from my dome or did you see it elsewhere?

As far as I know, I came up with this original idea when I built ASIGN and couldn't afford the usual strips I had seen others use to join the triangles. Once the inspiration for the little pentagons and hexagons was realised and worked, I was happy for the whole world to use it. I've since seen them used on other observatories and it would be personally interesting to find out where people get the idea from.

Baz.

[ChrisM]

Baz, I suspect that you're right: I probably did get the idea from you. I can recall looking over your construction notes pretty carefully on your website, as well as those from Barry Neumann (who fibre-glassed cardboard) for his geodesic dome. Either way, the idea worked well. Originally, I overlooked liquid nails and tried ordinary wood glue, but that was hopeless. The final result was very strong. Tonight, it will be subject to 120 kph wind gusts here, so I've battened down the hatch even more than usual.

Cheers, Chris

[bloodhound31]

Thanks Chris, it's just interesting is all. I would like to see the idea spread as my little "Thank you" contribution to the world for all the help I got from others when I built mine.

[ChrisM]

After more than 3 years in place, the pristine white dome was no more. Especially on the Southern side, it had turned a grungy green, although from a distance, the overall impression was still white.

Today I sponged on some sodium hypochlorite in the form of "30 second Outdoor Cleaner" that I got from the local hardware. A rinse with the hose then revealed the pristine white again.

Because my dome is over 5 metres tall, I can't quite reach all of it from the ladder or from the slot, so the plan is to put a sponge on a stick to complete the job. Anyway, the photo shows you how well it is working!

Chris

[bloodhound31]

Whoa! SHINY!

[bloodhound31]

Chris, can you please tell us a bit about how you worked out the curve of the stairs, and how you attached the steps themselves to the wall?

I assume the curved bit is roll-formed flat steel? What do I need to know to make a set of stairs like this? My internal wall diameter will be a little under 5 metres and ascending 2 metres to the floor above.

Any help would be appreciated.

Baz.

[ChrisM]

Baz, The stairs are generally (see below) 600 mm wide and rise 2.35 metres, with a total of 12 steps including the landing. The key component was the 200 x 10 mm plate that I had rolled to a helix with a radius of 600 mm less than my observatory radius (inner wall). From memory, this was pretty close to a radius of 1100 mm. Of course, the helix has to rise the distance that the stairs do. (So for your obs, if the inside radius of the wall is say 2400, and you want stairs 600 wide, then the helix would have a radius of 1800.)

The sketch that I presented to the rolling shop showed a cylinder of 1090 mm radius, with a band (forming the helix shape) rising from the ground up to the top of the cylinder over a specified portion of the circumference. I've attached the sketch that I gave to the rolling shop.

As it turned out, they rolled it for the wrong hand (ie. did not follow my drawing), and they had to do a fresh one for me. They also had trouble keeping a constant radius, with the result that my stairs reach a minimum width of 545 mm about 3 steps from the top, but they flair out to 800 mm wide at the bottom. At first this seems to be not good, but in reality, the flair is perfect. It gives the stairs a more grand appearance!

The steps are solid hardwood (Vic Ash) 25 x 160 mm. On the stringer, I bolted a 50 x 50 mm angle for each step, and secured the step with a couple of wood screws to each one (from underneath). The outer end of each step rests on a pine batten which is itself screwed to the stud frame.

I welded a flange to the top of the stringer and it's bolted to one of the floor joists (190 x 45 F17). The bottom of the stringer is bolted to the concrete slab with a small bracket. The whole result is very solid.

Some quick pics attached.

Hope that is of some help.

Chris

[bloodhound31]

AH YES!! I see it now. You have answered one of my toughest questions in one photograph. I was wondering about the helical roll on the 10 x 200. You wouldn't believe it, but I found a piece that might match exactly, sitting out the back of my old place of employment. I've hit the boss up for it.

Of all the features of an observatory, I like your spiral stair the most. I've GOTTA have one!!

Now all I have to do is work out what measurements to give the roll-formers for my 2.5 radius room with a 2 metre high wall.......maths has never been a strong point beyond simple arithmetic for me.....

Thanks so much for the advice mate.

Baz.

[HolyWars]

I've visited this thread many many times, and I am always amazed at how brilliant your observatory is Chris. I can only dream of having my own like that one day.

Well done! :)

[ChrisM]

Thanks HolyWars - It took a lot of thought and effort to design and construct it, but I would venture to say that anyone with a few simple building skills (and I am not a builder) and the will, could build something of which they are rightfully proud.

You have to live your dreams!

Chris

[ChrisM]

A few enhancements and an upgrade have occured over the last month.

I got some cheap digital thermometers and have put these on a panel to show concrete pier temp, steel pier temp and the ambient temp upstairs. No surprises here - the concrete pier is always lagging the trend.

Also from ebay, I got a cheap ($5.47) IR light which I use to boost the lighting for the scope/mount surveillance CCTV. Sample pic attached. The view is actually clearer than this snap would indicate. I've wired in a 5 Watt resistor into one leg of the SPDT centre-off switch to provide a Low/High lighting option.

To better protect the telescopes and mount, I got a custom-made cover made from tent fly material. The actual material is purple PU-coated nylon, and it's got a drawcord which allows me to pull it in tight around the pier. I place a few silica gel dessicant canisters around the mount to help keep any trapped moisture under control.

And last but in no way least, I've replaced the LX90 with a larger SCTand a 5" refractor, both of which sit on a 1200 GTO. It's still very early days with this set-up - the refractor hasn't even seen first light yet.

I'll post more in due course.

Chris

[traveller]

Chris, fantastic setup. When will you be taking tours? I for one will be happy to drive to Gippsland and pay an admission price, just to check out the setup :)
Keep the piccys coming, love your work!
Bo

[ChrisM]

Thanks Bo - there have been plenty of friends and family take a look, but it wasn't built as a public facility. Send me a PM if you're coming down this way.

Chris

[Meru]

Have to say - I'm really jealous of you! Good work, you should be very proud of this.

[h0ughy]

nice upgrades

[blindman]

:jawdrop::jawdrop::jawdrop::jawdrop :Wow

[ChrisM]

Here's a few pics of the 700 mm deep power cable trench. Dingo hire was $300 for the weekend. It ripped through the soil pretty easily, although is not very stable on a side slope. Where the trench could not be so deep, I capped it with 75 mm of concrete (as well as the orange warning tape, which was laid about 150 mm above the power cable conduit).

Really glad that I went for a 240 Vac supply rather than solar / battery.

Chris

[ChrisM]

We were away for the recent magnitude 5.3 earthquake which was centred only a few kilometres from here, so it was with some trepidation that we inspected our house and observatory upon arriving home yesterday. I'm glad to report that there appears to be no damage to the observatory, and apart from smashed china ware, vases and ornaments; plus books and pictures on the floor, everything seems to have survived.

Before arriving home, I was concerned that the approx 100 kg of mass on the 3 metre pier might have tested the pier-foundation interface beyond the limit, or, that the building itself may have bashed into the upper part of the pier via the edge of the hole in the observing floor (which is about 2.2 metres above ground level). This appears not to have been the case since the electrical cables that pass through the narrow (~5 - 10 mm) gap do not apear to be marked at all. Whew!

I've just checked the polar alignment and it has moved a small amount in an Easterly direction, which is interesting, since most of the stuff affected in the house also moved in an E-W direction too.

I now think that the 188 kg of reinforcing steel that I put into the pier foundation, along with the 2 cubic metres in the block, and the 450 mm dia concrete pier were all well worth it! After all, who designs their observatory for an earthquake?

Chris

http://www.iceinspace.com.au/forum/attachment.php?attachmentid=48230&d=1222257974

http://www.iceinspace.com.au/forum/attachment.php?attachmentid=48231&d=1222257974

[2stroke]

Thats mint, lol i would move in and live there :)

[DavidTrap]

Good to hear your observatory (& home) survived relatively unscathed.

I wonder if the seismologists at the universities would be interested in your observation about the displacement of your polar alignment??

DT

[ChrisM]

Thanks David. Maybe the movement is largely based on radial direction from the epicentre? I don't know - I guess that the local geology might also affect the direction of movement.

Chris

[Varangian]

Hmmm the missus wouldn't see me for months...

This is the most impressive thing I've seen today (and I've done a lot of surfing)!

[ChrisM]

Hi John.
My wife likes observing too, which is fortunate for my/our hobby. And thanks for the compliments too!

Chris

[ChrisM]

Yesterday I went to switch on the observatory dehumidifier and discovered that it was chockers with ants. They had got into every conceivable nook and cranny. After lots of ant-spray, compressed air and water, they're still not all out, but I reckon that I've got 99% of them so far. I won't reassemble it for a few more days yet.
Chris

[Ric]

Pesky little critters.

Your lucky they haven't found your telescope, that could have spelled real trouble.

[ChrisM]

My dome has been built for over 5 years now, so I thought it time to update this thread by reflecting on the observatory’s design and how well it has worked.

Firstly, some basic stats on the two-storey 5 metre high obs:

Dome - 3.6 metre diameter, geodesic, 105 off 9 mm plywood triangles
Turntable – rolled 75 x 75 x 6 mm angle iron running on upturned plastic wheels
Walls – 3.0 metres, mini-orb cladding
Foundation: - 2 cubic metre reinforced concrete block
Pier – 2.2 m x 450 mm dia reinforced concrete pier, with an 1100 mm x 275 mm dia steel pier extension.
Mount – AP 1200 GTO
Scopes – M14 SCT & NP 127is
Observatory construction cost - $7k (excluding equipment)


How well has it worked? Overall, very well indeed. To have one’s scope permanently fixed to a mount on a solid pier saves a lot time and makes the whole experience much more satisfying. Set up time is not much more than 5 minutes. The dome provides great protection from the wind and dew, and also from light pollution. The hinged lower slot door rarely needs opening. The observatory has been used mainly for visual work, with over 150 visitors passing through since it was officially opened in 2009. More recently I have experimented with my DSLR camera taking images through both scopes, but mainly through the 14” SCT. I don’t have any guiding (yet) so generally limit exposures to 1 minute at 3.5 metres focal length. I never see any evidence of wind-induced vibration – either in the eyepiece or in images. It seems that the pier is fairly well isolated from the building too.

The two-storey design is neat and compact, but does involve many trips up and down the stairs; this doesn’t worry me at all but does deter some visitors from venturing up the spiral staircase to the observing floor. Last night, we had over a dozen visitors (typically aged over 60) and they all ventured up. If need be, I can rig up a monitor downstairs to show live images.

Issues: Not surprisingly, keeping water out is the key issue.
(a) Water ingress – mainly through penetrations in the dome –eg. Stand-off bolts for the shutter tracks. Also occasionally through an unknown path onto the dome base ring. I am considering hiring a cherry picker so that I can cover the entire dome in a special mesh fabric and then apply a roof sealing paint – industrial quality. This will provide a longer term fix and help protect the timber construction. The top one-third of the dome’s external surface is virtually out of reach – even with a long extension ladder.


(b) The southern side of the dome gradually attracts mould, which can be wiped off with a sponge and some mild bleach.
(c) The bottom plate of the circular building’s timber frame is also timber, and whilst I used a dampcourse layer between it and the slab, it would have been better if I had made it from hardwood or steel. It might be the weak link in the overall design.


(d) Strong winds have not even hinted at moving the dome itself (~250 kg) but have once partly moved the shutter (> 120 kph). It’s now tied down more securely, and it’s best to keep it closed during wind > 25 kph.


(e) Spiders, ants and other insects have chosen the dome as their home. Maybe I need to get a pest exterminator to spray the whole building.


(f) The width of the dome opening is barely 700 mm, which is great for protecting the observers and equipment from the elements, but another 200 – 300 mm would have made the world of difference for ease of keeping the scopes looking through a clear opening. However, the present arrangement is workable, although a 14” scope on an offset GEM is at the limit. (The pier was offset 250 mm North to allow for the original fork-mounted scope.)


If I were to build it again, what might I do differently?
1. Consider making the building only 3.5 m diameter, so that I had the option of using a ready-made fibreglass dome (that could be automated).


2. Use a different material for the building frame’s bottom plate / ring (refer to (c) above)


3. Cut a wider aperture opening – say at least 900 mm wide.


4. Make the dome about 12 mm larger in diameter than the building, so that the weather seal design is much simpler.

Conclusion – The project has been very satisfying to build, own and operate, and has delighted many a visitor. The home-built observatory, which allowed me to upgrade my equipment considerably, does not come without some on-going maintenance, but the rewards are astronomical!

A small selection of pics showing various phases of the project....which of course, will never end.

Chris

[ChrisM]

A few details on the turntable:

Diameter = 3.6 m
Lower ring (fixed to top of walls) = 100 x 50 mm ply
Upper ring (rotates) = 100 x 50 mm ply attached to a 75 x 75 x 6 mm steel ring rolled to 3.6 m dia.

In the photos, the plywood rings are blue, and the steel ring is red.

Eight plastic wheels are mounted on the lower fixed ring, and the steel ring sits on those wheels. Three additional wheels, spaced at 120 deg around the turntable, keep the two rings aligned.

The cross-section drawing also shows how the 5/8 geodesic dome was attached to the top plywood ring, and how the safety hooks (purple, & 13 off), that stop the dome lifting off the walls, were arranged. The brown-coloured C-section in which the safety hooks operate, was made from about 1.6 mm sheet formed and then rolled.

On the LHS of the sketch, the weather-shield can be seen. A neater and easier design would have had the turntable a fraction larger in diameter so that the weather shield did not require profiling.

Chris

[ChrisM]

After five years in the weather, the dome had deteriorated more than I expected so I have just spent the weekend finishing what I started doing on the Labour Day w/e in March: applying a new paint system to the dome.

After cleaning the dome, I applied a self-adhesive plastic mesh to the entire dome surface. The mesh comes in 1200, 200 & 50 mm rolls, so it was a bit of patchwork application, with plenty of overlapping areas. The paint was Granosite, which is very thick and forms a membrane in and over the mesh. I lost count of how many coats I applied - perhaps 6 or 7 all up, taking 20 - 25 litres of paint. Even with multiple coats, the mesh is not completely filled up everywhere, so I hope the surface doesn't capture too much dirt.

Access was gained via a trailer-mounted 34 foot cherry picker.

Chris

[Kunama]

Great work Chris, Granosite should last well. I have used it before with the addition of chopped f/g strand. (you get better coverage with less coats)

[hamishbarker]

Hi Chris,



Our local astro society has a great observatory but it was originally built for a long refractor and now houses a 14" SCT. So the pier is really tall and eyepiece access is always by mobile stairs. I don't like them and am trying to convince others that an observing floor could be built to enhance operations, particularly for little ones (we use it mainly for public nights).



How high is the top of your pier's mounting plate (i.e. what the mount bolts to in lieu of a tripod) above the level of the observing floor? Are you (and your wife) satisfied with the level, and how tall is the shorter of you?


I see that your stairs are pretty narrow. I think our dome is a bit bigger than your 3.6m. Is that 3.6m to the inside edge of the walls or ring, or the outside walls?


Thanks in advance for a response and congrats on an excellent obsy!


Cheers,
hamish Barker
Nelson, NZ.

Cheers,
Hamish

[ChrisM]

Hello Hamish and thanks for your kind words. I saw your post just today so apologies for the delayed answer.



The height to the top of the plate upon which the mount (AP GTO 1200) is fixed is 995 mm. Necessarily, this is a compromise but I think it is a good one for the range of elevations that the scope is used for. Due to lots of trees, I rarely observe below about 20 deg - may be once in a while to show a visitor the crescent Moon or Venus, and on those occasions I use a set of steps.



When observing a target above say 70 deg, I need to get down quite low on the adjustable observing stool. The lowest seat position is 325 mm above the floor, and sometimes that is not quite low enough, but that might be for photographic work with the DSLR, which sits out a little way beyond where the EP would be since I don't use the diagonal with the camera.



Most observers would be in the 160 - 180 cm height range. There is also a fair bit of flexibility to be had just by rotating the diagonal to match their height. There is obviously a lower risk having someone get down a bit lower than having them climb steps in the dark, especially when you don't want them to reach out and grab the telescope should they lose their balance.


The OD of my obs is 3600 mm so the nominal ID is 3400. The stairs were designed to be 600 wide, which is adequate in practice. I didn't want to sacrifice any more observing floor space than essential.



I had a quick look at the Nelson Obs website, and I see what you mean about the tall pier! Good luck with your deliberations.


Cheers, Chris

[ChrisM]

One of the disadvantages of a tall observatory (5.2 metres in my case) is that you can't readily get to, or even see, all the parts. Recently, when I did get to see the sliding shutter frame, I was horrified to find that part of it was almost completely rotten and would need replacing.



I bit the bullet and decided to make an aluminium frame rather than copy the original wooden design. The two side rails were cut from a 6.5 metre length of 50 x 50 x 3 mm square hollow section rolled to (hopefully) the correct radius.



I can never cut square with a hacksaw, so used an old mitre saw that still had its original blade (from 1986). It did a great job!


The design is simple: three lengths of 10 mm threaded rod, with a couple of 35 x 10 mm sealed bearings on each, to space the rails the right distance apart. The skin is 0.55 mm 'sign white' sheet metal, which I will pop rivet to the Al frame.



I need to hire a cherry picker to remove the old shutter and install the new one. I'll combine this with a total re-paint of the dome - the last time was in 2014.