The Observatory

Planning and Construction

This Observatory is situated in my backyard in the little suburban town Melkbosstrand some 25 km from the City of Cape Town, Western Cape, South Africa.

Introduction

As already indicated in my introduction to this website, I was a “late bloomer” with respect to the purchasing of my first telescope. My first telescope was a Celestron NexStar 127SLT Mak. I soon, however realized that it wasn’t enough. I subsequently bought an old Meade XL200 10” Classic and although I was very happy with its performance I jumped to it when I recently had the opportunity to acquire a 14” Meade LX200R GPS. While the 10” scope can still be described “mobile”, the latter definitely is not. This obviously lead to the construction of the Melkbosch Skies Observatory and subsequently to the development of this website. This page provides more detailed descriptions of the planning and construction the Observatory building.

Initial planning

Constructing a small backyard observatory to accommodate my needs wasn’t easy. As far as I could ascertain, there are no private companies in South Africa, or in the rest of Africa for that matter, who specialize in the construction of backyard observatories. Most amateur astronomers either make use of plastic garden sheds or so-called “Wendy” huts (a term used in South Africa for slatted wooden huts) but neither is effective from a security or weather point of view. I considered ordering a pre-fabricated POD kit from Sky Sheds.com in the USA. Although they don’t normally ship to South Africa, the chaps were extremely helpful and were quite willing to make a plan. It eventually however appeared that the POD would be too small for my purposes.  Eventually I was forced to commission a private construction company to build my observatory.

In spite of my eagerness to bring Melkbosch Skies Observatory into service, it was important to take enough time to make sure it would meet my needs. Detailed planning for the Observatory continued for a few weeks before construction began. Being in a built-up area with relatively small plots (500 m²), finding a suitable spot for the observatory was difficult and the options limited. The floor level also had to be raised to get a view over the adjacent houses’ roofs and trees.

Type of Building

The most important design choice to be made was roll-off roof vs. dome observatory. Domes have traditionally been the classic design for observatories, but roll-off roof designs provide an all-sky open view. Construction of a flat sliding roof is also less complicated. After review of the offerings for prefabricated huts, mostly wood and plastic, I chose the latest light steel frame construction method with flat roof running on wheels. It is 9 square meters (approx. 10 x 10 feet) in extent, which provides enough space for me, my equipment, and a couple of guests.

Approvals

Our local authority requires an engineer’s certificate as well as detailed drawings for a structure of this size. Although it wasn’t required, the neighbours’ consent was also obtained. They all insisted on being invited to the evential official opening of the observatory.

Obviously, I had to make sure that the aesthetics of the structure meet with my dear wife’s approval.

Construction

We opted for a light steel frame construction on fairly heavy steel base. The very able construction team of Global Construction Management  were responsible for the actual construction of the Observatory and as Des Palm, the owner of the company predicted at the outset of the project, we would have a number of interesting “Oh sh@#!” moments throughout the project. We never, however failed to overcome any of these “moments”.

The floor was constructed on 306 x 306 mm UC steel columns, raised 800 mm from the ground. The floor surface consists of 21 mm shutter board floor board, with 25mm Isoboard insulation and 12 mm MagnaBoard sheets on top. I installed industrial grade carpet tiles on top.

The walls are 12 mm MagnaBoard© (Magnesium Oxide) panels onto 90 mm x Z275 galvanized Light Steel frames with 63 kg mineral wool wall insulation and 18 mm shutter board on the inside. The corner posts are 150 x 150 x 6 mm steel columns.

The roof is Colorbond steel roof sheeting on industrial sisalation on 100 x 50 mm galvanized lipped channel purlins on 100 x 50 mm rectangular roof beams.

Telescope Pier

The telescope pier was constructed of heavy steel, 150x150x6 mm (square) and planted in one cubic meter steel enforced concrete. It runs through an opening in the floor without touching the observatory’s floor structure. Electricity, video and computer cables were channeled under the floor and inside the pier in separate conduits, with multi-plugs fixed to the side of the pier. There are therefore no cables lying on the floor. I fixed a heavy-duty Meade equatorial wedge on top of the pier for long exposure astrophotography, although I don’t foresee getting into that quickly.

With the telescope already available, it was easy to get the needed measurements and calculate the appropriate pier height. The roof structure misses the top of the telescope by about two to three cm when the telescope is pointed at the horizon.

A late note on the pier. Although I initially thought that the base was sturdy enough to prevent vibrations, I did eventually find that vibrations took longer than the norm (about 3 seconds) to subside when the scope was bumped by accident. Not wanting to remove the scope after being polar aligned and set up, we opted not to weld larger and longer flanges onto the base but rather to encase it in a concrete pillar. This did the trick.

Services

It made sense to install utilities at the outset than to add them later. For this reason, I planned on ample electrical and data/video services with provision for expansion. The major elements are

• Eight circuit breaker distribution board with space for expansion if required
•  No less than eight wall plugs installed in all four walls, with three based in close proximity of my work station
• Special wall plug for roof motor
• Switched electrical outlets on each circuit, to allow LED lighting to be controlled from a switch panel near the door
• Video cabling, to support video cameras and for LED video monitor (actually small TV)
• Conduits to the ports in the pier and wall plugs run in the walls and under the observatory floor, to eliminate trip hazards.

I planned for my workstation along the West wall. The observatory door had to be oriented to the North-East. This orientation keeps the door opposite the prevailing South-Eastern wind and also facing the residence. We have since decided to enclose our patio area, with the result that the observatory door now forms part of the enclosed patio area, thus improving security tremendously.

The roof control, motor and power supply are placed opposite from the door, on the Southern wall. The roof opens and slides away to the South. We initially used a standard 500kg gate motor but soon realized that it wouldn’t last with the heavy roof. We eventually opted for a workshop hoist crane motor that the contractor had available. Totally too strong for this application but I will never have to worry about it not being able to open or close the roof.

Furniture

I am not a handyman. I have, as my dear wife would aptly describe me, ten thumbs! I initially had a private contractor carpenter measure up where I wanted cupboards and my workstation and provided him with my choice of wood finishes. However, after three weeks of no-show by the contractor my impatience got the better of me. I eventually opted to buy DIY desk and cupboard kits from MAKRO, a large wholesale retailer owned by Massmart, which I proceeded to assemble with much swearing and sweating. Although I had to make do with wood finishes that weren’t my first choice, I am still rather chuffed with the end results. I installed a small two drawer desk to serve as work station and two standing shelved cupboards against the West and East walls in the corners nearest to the door. I removed most of the shelves from the one cupboard to also make room for my three telescopes’ tripods.

First Light 

The Observatory structure was completed by end October 2017. However, due to our decision to enclose the patio area between our house and the Observatory, thus creating a new recreational area and linking the Observatory and the house, the telescope could only be installed late December 2017. The telescope was finally set up and aligned on the night of Saturday, 13 January 2018. This is therefore the date that it officially saw its “First Light”.

My good friend and astronomy hardware mentor, Martin Lyons and I duly celebrated the occasion with a glass of very good Pinotage.