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Jonesdee

Mini Observatory for Astrophotography

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Hi All

Having lurked on this forum for about a year and made a couple of good purchases from the classifieds section, I thought I would share details of my recent project to construct a mini observatory for astrophotography work. Having personally learned a great deal from SGL, I hope this may assist anyone considering a similar project.

After a lapse of more than 10 years, I got back into astronomy last summer with the purchase of a 200mm Dob, but soon graduated to a second-hand EQ5/200P with the intention of motorising the mount for photographic work.  I followed Tom Carpenter’s excellent instructions for fitting stepper motors and built one of his AstroEQ controllers which works very well indeed.  I now use this with either an 80mm refractor or 6” R-C, given the excessive weight of the 200P for imaging.

Thanks to our weather, it soon became obvious that there are many advantages to having the mount permanently set up and ready to use at very short notice, hence the decision to build the observatory.  Part of the motivation was the challenge of constructing a dome, plus an overall design which was small and would not look too obtrusive in the garden. It was never intended to be used for visual observation, so an overall dome diameter of 1.2 metres gave sufficient space for full movement of both OTAs with SLRs/filter wheel fitted.

A selection of photos of the build can be found here:

https://photos.app.goo.gl/g9DnEucfvhZyHZWr2

The dome is constructed from 18mm ply framing with 3.6mm ply cladding, which was laminated inside and out with glass cloth/epoxy resin. It rotates on 6 rubber-wheeled castors with another 4 mounted horizontally to keep it central. The main shutter runs on 4 transfer rollers with an additional 4 mounted vertically to ensure it does not jam when opening/closing.

The base structure consists of 8 OSB panels with strengthening battens. These fit between eight 45mm x 70mm uprights which support the weight of the top panel and dome.  OSB is not ideal for outdoor use, but the entire structure has been painted with exterior undercoat and three topcoats, so it hopefully will remain weatherproof for a number of years.  The entrance hatch is fitted with surface mounted S/S hinges and an espagnolette lock. The main shutter overlaps the lower hinged flap by 50mm to help with weather proofing and two sliding bolts hold it shut when not in use.

The pier is a 900mm length of 168mm galvanised steel pipe, filled with concrete.  The ground at our location is difficult to dig due to layers of limestone rock below approx. 600mm deep.  For stability, I drove a 2m length of 35 x 35mm steel angle down through the rock prior to pouring around .5 cubic metres of concrete into an appropriately tapered hole.  Short brackets mounted on the angle hold 4 lengths of 8mm rebar which are spiralled into the hole for added strength and support of the steel tube.

The adaptor plates started life as two 200m x 200m x 12.5mm square plates, separated with 4 lengths of 16mm threaded bar.  In addition to levelling, these enable the height of the mount to be adjusted, to accommodate full movement of the scopes inside the small dome. Once the mount and scope were fitted, it was clear that the corners of the plates could collide with the camera or filter wheel, so I resorted to cutting the plates into discs with my woodworking bandsaw (actually a surprisingly easy task) and repositioning the 4 x 16mm rods.

I have only managed to use it twice since completing the build, primarily to drift align the mount, hopefully I will follow this post up with some images in the near future. 

Any questions, please give me a shout

Cheers

Dave

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Many thanks Steve, I'm itching to get to use it properly - at least today's weather has proved that it is waterproof :)

Dave

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Fabulous build Dave. I hope you have many happy years imaging.

How many clamps......:icon_biggrin::icon_biggrin:

Steve

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Cheers Steve

Yup, you just cannot have too many clamps!

Being a keen woodworker for many years, I have aquired a good selection of tools to make a task like this relatively easy to accomplish.

Also, being almost 70 now and recently retired, I have the time to spend on projects like this (certainly beats working!)

Dave

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I'm of a similar vein Dave albeit metal and plastics as first as a Toolmaker, then draughtsman and finally as a Chartered Engineer. 

Always felt best though, working with my hands.

Steve

 

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Lovely observatory Dave. Great build photos - quality job! Hope it gets lots of use.

Kev

Edited by Astrokev

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Cheers Kev, I hope we get some decent weather soon to give it a proper try!

Just to have the mount set up and ready to go is a massive benefit. Being a very compact obs, I can mount the scope through the shutter opening, so it is not necessary to climb inside too often.  Next step will probably be a motor to rotate the dome, but I don't see that as a critical item yet.  With the 80mm refractor, it appears to take around an hour to track from one side of the slit to the other

Dave

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