Deep Sky Observatory

Jupsat Pro Astronomy Software

Secrets of the Deep Sky

Get Instant Access

Jack Newton

Figure 16.1 The Newtons' home in British Columbia, housing the observatory, darkroom, machine shop, computer room and home cinema.

I have been an amateur astronomer for almost forty years, yet today I find the universe as mysterious and intriguing as I did during my childhood. I took my first astrophotographs at age twelve, in an attempt to prove to my school chums that I really could resolve the rings around Saturn, even though my instrument was a tiny refractor and my vantage point the roof of a parish church! Since that time, I have constructed a number of observatories in locations all across Canada. Whenever I found myself "between properties" or fleeing light pollution, I ventured forth with mobile

telescopes. What follows is a description of the "observatory with living quarters attached", which I have been enjoying for the past four years.

Before beginning, I should explain that I never quite got the hang of reading blueprints or following building plans. All of my previous observatory designs, stationary and mobile, reflect my personal belief that function takes precedence over form. If something isn't available off the shelf, then I design and build my own. If something doesn't fit, then I get a bigger hammer! My usual strategy is to watch the "doers" and then adopt their most noteworthy ideas. I'm unimpressed with expensive, flashy setups which look great but never get used. I unreservedly "borrow'' the best ideas I see in other observatories, and am delighted if other people choose to adopt mine. I devote a great deal of time to astrophotography; however, I am devoted to public education in astronomy, and frequently open my observatory to students of all ages. I get a lot of enjoyment out of teaching young people visual observing techniques, and introducing them to the wonders of the universe through computer imaging.

I realised my dream of one day building a mountain-top home, with an observatory on the roof and a large telescope inside when my wife, Alice, and I discovered 72 acres of property on the extreme southwestern tip of Vancouver Island, British Columbia, Canada. The heavily treed land overlooks the Straits of Juan de Fuca and the beautiful Olympic Mountains in Washington State, USA. This site is on Mount Matheson, 300 m (1000 ft) above sea level. It is not a lofty height as far as mountain elevations are concerned, yet is usually sufficient to keep the fog and ground haze well below us.

I trailered my telescope to an adjoining parkland site for almost three years before committing to the mountain location. I did all I could to test the suitability of the site beforehand. Anyone who has ever tried to forecast weather for coastal areas will confirm that such predictions constitute a far from exacting science. Conditions tend to vary quite considerably hour-to-hour, much less over days and weeks. Generally, the local weather from January through June seems to follow no set "pattern". And decent seeing during July and August can be disturbed by winds down the Strait. As often as not, though, September through December make up for the other months of uncertainty, and frequently offer still air with arc-second seeing.

Alice and I self-designed our new home (see Figure 16.1) to include all the favourite features of past homes in which we'd lived and allowed for the addition of a few extras: the observatory, an 11-tonne telescope pier, a photographic darkroom, a machine shop, computer room and home cinema. My warm office is in the level directly below the observatory, and from here I can manually or auto-guide. We planned the house in such a way as to allow plenty of room for the pursuit of our many varied interests. I knew from previous experience that I would seldom have a night alone in the dome, and so paid particularly close attention to details enhancing the comfort, convenience and safety of the observatory. We included the theatre not only for our own enjoyment, but also as a projection room where we can entertain the visitors who overflow the dome during observing sessions and tours.

I designed and built the 4.8 m (16 ft) dome myself, after regular work hours and on weekends. I was up against a rather gruelling time schedule of thirty days from start to finish. This was due to a number of factors. First, the unexpectedly fast sale of our previous home (which we needed to sell in order to free up money for the new one) had forced us into rental accommodation on only three weeks' notice. Second, the new construction progressed quickly, and any delay in the dome would cost our building contractor lost time (and us more money). So the dome had to be completed, delivered and ready for lifting by crane on the same day that the roof trusses were put into place. Finally, just to add to the excitement, we were ticketed to leave for the solar eclipse in Baja, California only a day or two after the scheduled lift. There was no margin for relaxation!

I did the fabricating in a friend's spacious and well-equipped workshop some distance from our home. I needed to construct the dome in halves, so that it could be more easily transported to the new site.

I started by cutting curved 200 mm (8 in) widths of 30mm (fin) plywood from 1.2 m x 2.4m (4ft x 8 ft) sheets and positioning them on the shop floor to form a 4.8 m (16 ft) circular base. I then glued and screwed two additional plywood layers over the first one to create a strong laminated base-ring. I built the two main overhead arches using the same diameter as for the base and set them 1.2 m (4 ft) apart. I then laminated strips of 4.8m (16ft) x 60mm (2jin) x 10mm (I in) cedar lathe (the kind commonly sold by garden shops to make rose trellises) to form a 100 mm (4 in) thickness and bent these into position, C-clamping them to the circular base as a temporary bending form. I needed twenty-two of these laminated ribs, which I had also glued and screwed for strength. I then formed the front of the dome by placing the ribs at 0.6 m (2 ft) intervals from the outside of the basering to the arches (see Figure 16.2). I secured them into place using metal brackets. I then covered the "skeleton" with I mm (sin) thick mahogany door-skins (see Figure 16.I). This sheeting is the thin material used by manufacturers to cover hollow (as opposed to solid) core doors, and is usually available from a builders' supply store in 1.2 m x 2.4 m (4 ft x 8 ft) sheets. I shaped and cut each section, bent it over the rib structure, glued it into position over the ribs, and then nailed it into place. Once all of the panels were in place, I painted the interior of the dome black to cut down on reflected light and sprayed it with Lysol disinfectant as a mildew retardant. Finally, I covered the outside of the dome with fibreglass cloth and topped it with two coats of resin and a final white coat. Once dry, the dome was finally ready to be moved out of the workshop!

Figure 16.2 The overhead arches, laminated ribs and mahogany sheeting used to form the dome structure above the base ring.

Figure 16.2 The overhead arches, laminated ribs and mahogany sheeting used to form the dome structure above the base ring.

Dome Forms Building

Unfortunately, the only egress from the workshop Figure 16.3 The was down a steep, narrow, twisting and gravelled mahogany sheeting access road and then along a public roadway for seen fr°m the outside. several miles. We made this move after nightfall, because although the dome halves were neatly sandwiched back-to-back for transport, their width still exceeded the legal limit for open-road hauling without a special permit.

Save for the weather, which was cold, wet and windy, the move to the new neighbourhood went without a hitch. We celebrated our success with a champagne toast, hunched inside the dome alongside the roadway. Somehow, I couldn't help wondering if this experience bore any resemblance to a party in an Arctic igloo. . . .

The next day, I finished assembling the dome by reconnecting the halves of the base. My final crucial step was to bend electrical conduit to form a ring, which I attached to the bottom of the dome.

I then turned my attention to the portion of the house roof where the dome would sit. I had a 1 m (31 ft) pony wall built on the roof, and I installed five in grooved V-wheels in an upward position every 0.3 m (1 ft) along the top of this wall. The idea is that when the dome is lowered, the conduit ring on the bottom of the dome becomes the track in which the wheels ride. I'm pleased to say that my prayers were

Figure 16.4 The dome about to be hoisted into position on the roof.

ultimately answered as the dome was lowered over the track, the two circles matched up perfectly and the dome rotated freely. With the dome now securely in place, I attached the covering for the slit, which has a 1.2 m x 0.6 m (4 ft x 2 ft) section at the bottom that flips out on hinges. The upper 3 m (10 ft) section slides over the top (see Figure 16.5).

I also considered other special needs when planning the "perfect" observatory which would soon house my 635 mm (25 in) f/5 Newtonian telescope. Local building regulations required that I build an engineered support pier to carry the 3-tonne weight of the telescope. Apparently, there was no precedent for such a structure on the records of the inspection branch. Once I explained to the civil engineer and

Figure 16.5 The dome-slit, with lower flap and sliding upper section.

the building inspector just what I was trying to accomplish, I met with no resistance. I had our contractor put in a 1 m x 1 m (3 ft x 3 ft) pilon consisting of concrete blocks reinforced with steel rods and filled with concrete. It sits on a special footing anchored to bedrock and runs up through the three floors of our home into the dome (see Figures 16.6 and 16.7). To accommodate movement of the telescope inside the dome, I had our builder reduce the diameter of the pier to 0.3 m (14 in) where it entered the dome. The floors and ceilings in the rooms below butt up to, but do not touch, the pier itself, since any vibration caused by walking, doors closing, etc., would be echoed through to the telescope and camera. Also, since heatwaves cause distortion on the mirror, the telescope must be constantly kept at ambient temperature. I therefore arranged for insulation of the floor and the separate stairway leading to the dome. An interior door at the bottom of the stairs closes the office off from the stairs. I put in a lift-up trap door at the top of the steps, and having two independent doors between the dome and the warmer temperatures of the house has proven quite effective. (These days, I often turn on an exhaust fan to gently move air through the dome about an hour prior to doing any observing.)

To ensure that people can safely move between the office and the dome, I have positioned low-wattage sidewall lights in the stairwell, and installed red lights on dimmer switches in the dome itself. The floor in the dome is carpeted. This certainly helps to reduce breakage to eyepieces or other equipment that may be

Figure 16.6 The position of the observatory on the building.

Figure 16.6 The position of the observatory on the building.

Figure 16.7 The concrete telescope pier (just visible, left of centre) rises through three floors of the house.

dropped from the top rung of my tall observing ladder. I have also affixed strips of the carpet to the inside of the dome wall to act as a protective skirting where the wheels run in the track. This not only prevents fingers, hands or clothing from becoming accidentally ensnared while the dome is being rotated, but offers the further advantage of cutting down the drafts which would normally enter through the gap. The dome sometimes does retain some moisture due to marine fog. I keep a small heater kept dialled to a very low setting in close proximity to the telescope and computers. During the winter months, high winds often buffet the mountain-top. To help prevent the dome from lifting, I have thick chains attaching it to the inside of this pony wall in at least a half-dozen places.

I built the telescope mount around a 430 mm (17 in) Mathis worm gear. The German equatorial design best suits my needs. The right ascension housing is constructed from heavy-walled 200 mm (8 in) pipe welded into 15 mm steel positioning plates. The right ascension shaft itself is 150 mm (6 in) pipe mounted through a bearing at each end; a larger clutch was added to this assembly incorporating a four-screw pressure plate. The declination housing is 150 mm (6 in) in diameter with a 100 mm (4 in) pipe shaft mounted in bearings at each end. The counterweight shaft is just an extension of the declination rod to secure the 450 lb (200 kg) of counterweight. The top end of the declination shaft is

Figure 16.7 The concrete telescope pier (just visible, left of centre) rises through three floors of the house.

attached to a 0.3 m x 1m (1 ft x 3 ft) 10 mm (2 in) steel plate. This plate has two larger rings welded to it to support the telescope tube. A 450 mm (18 in) tangent arm declination clutch is attached around the declination housing and worm-driven with a reversible synchronous motor. The cradle is 10 mm (iin) x 50 mm (2 in) wide steel bands reinforced with 25 mm (1 in) angle-iron. The 55 lb (25 kg) base of the cradle is a 1 m x 0.3 m (40in x 12 in) slab of 12 mm (2in) steel. The mirror telescope tube and cradle weigh in at over 300 lb (140 kg). The finished mount is equipped with optical encoders on both right ascension and declination for a CAT (computer-assisted telescope) computer.

The 50 mm (2 in) thick Pyrex primary mirror for my 635 mm (25 in) f/5 telescope was produced by Galaxy Optics in Colorado, and has a beautiful figure. The guiding head and eyepiece provide me with nearly 800 power for guiding. The mirror cell is 645 mm (25nn) pan-style, with a 10 mm (2in) aluminium plate base and a 50 mm (2 in) band screwed around the base to support the sides of the mirror.

I floated the mirror 100% on bubble pack (plastic packing material with air bubbles). I secured the mirror with six claws, which do not touch the surface of the mirror. I had a shipyard fabricate the barrel for the 3m (10ft) long tube, which is 3mm (sin) thick aluminium, rolled in three sections and welded together. I have since painted that aluminium tube over with flat black paint, and find that the tube currents have been greatly reduced.

I use a 110 mm (44 in) minor-axis diagonal and home-made off-axis guider. The simple guider is constructed using a 10mm (fin) aluminium plate that rotates in a ring mounting on the side of the telescope where the focuser would be positioned. This forms a photographic platform and permits quick changes in a variety of equipment. The guider has two prisms which are mounted on one side of the 60 mm (22 in) focusing tube. The prisms will rotate through the field and the whole plate will rotate as well. This is coupled with a 3x barlow and a 12 mm eyepiece which produces 800 power for guiding. I can virtually pick up any star in the field to guide on. I have a 180 mm (7 in) Meade f/9 refractor mounted onto the side of the large scope. This refractor has excellent optics for CCD imaging. I also use a 305 mm (12 in) LX200 series Meade computer-controlled telescope.

I now use a number of CCD cameras, some of which I own and others which I am beta-testing. I use three computers for imaging and guiding my telescope. The first is a 486-66 with I2 mB of RAM and a 1.4 GB hard drive. The motherboard has a cache using 4 mB of RAM with the CD-ROM and The Sky program. I have an NEC 4GF monitor and Diamond Viper 24-bit graphics video card, utilising 2 MB on the card. The 486 computer is in my office, directly below the observatory and is connected through conduit to the observatory. This is designed to control my telescope from the warm room. I also have a I86-40 in the dome, which I use for operating my CCD imaging camera. A second, older 286 is used to control the autoguider CCD camera.

I guide the main telescope with a home built off-axis guider. This guider features a binocular set of prisms injected into the edge of the same field of view as the primary CCD camera uses. The prism assembly slides under my electric focuser. I am presently using an ST-6 to auto guide my telescope. The telescope's guiding head is designed to rotate I60° and slide in through the field at the same time. It makes picking out a star to guide on from the field a very simple task. Although I have a 180 mm (7 in) Meade refractor mounted on the side of my large telescope, flexure remains a problem. I have found it much easier to place a small 90 mm (I.5 in) Maksutov on the top of the Meade and use the ST-4 or ST-6 to autoguide the 17 mm (7 in) with the big telescope's drive. Even though this combination sounds very much like the "tail wagging the dog'', it works flawlessly.

Using the Sky Pro program enables me to use three CCD cameras at the same time. I use one with Sky Pro, one with the I86 computer and the third one with the ST-6 to guide the CCD camera on the 286.

I'm having the time of my life in my home observatory. It's wonderful to be able to spend time observing, rather than facing a long drive to a distant site and a struggle to set up, only to have the wind or cloud move in. I can now image-process on the nights when the weather just doesn't co-operate, and love the new possibilities that CCD cameras and this wonderful observatory have opened up to me.

Chapter 17

Was this article helpful?

0 0
Telescopes Mastery

Telescopes Mastery

Through this ebook, you are going to learn what you will need to know all about the telescopes that can provide a fun and rewarding hobby for you and your family!

Get My Free Ebook


Post a comment