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Astrosystems Telekit



If you are like me, you are always purchasing different telescopes in the vain hope of finding THE one telescope that can fulfill all of your observing needs. Although I haven't found THAT scope yet, I have had a lot of fun trying! This article will detail my experiences with building the AstroSystems TeleKit. The AstroSystems TeleKit is a premium dobsonian telescope kit that is complete except for the optics. Although AstroSystems can supply diagonals for the secondary, the purpose of this review will be to detail functionality and construction rather then optical performance. First, a little bit about myself.

I've been observing in the Midwest for about 4 years, and I currently own an older model Vixen 80mm fluorite refractor, a 150mm refractor and a 12.5" reflector affectionately known as "Big Blue". My skies range from magnitude 5 at the zenith and 3 to 4 near the horizon depending on which direction you are facing. I live on 50 acres with abundant observing locations to choose from. In deciding on a large telescope, I wanted enough light gathering for the better faint fuzzies, but not too much to be a pain to set up or transport. I have a screened-in back porch that faces away from the prevailing weather that serves as an ideal three-season home for a large scope. When a local astronomer advertised a homemade 12.5" reflector for sale, I ended up purchasing "Big Blue". While the optics were first rate and the scope quite functional, I decided I wanted a more portable scope with better features and decided on a TeleKit.


Arrival and Description

The scope arrived principally in two large heavy cardboard boxes. Everything arrived without damage and packaged by groups. The wood is advertised as Baltic Birch plywood. While not very light, it is quite beautiful and easy to work. The wood components are CNC routed and sanded to a medium finish. Nearly all of the difficult cuts are already done and I never used a saw during construction. The ends of the rocker and mirror boxes are finger jointed, so no exterior hardware is visible. The upper cage consists of two wooden rings attached by wooden struts, all of the same beautiful wood. The focuser fits into the AstroSystems filter slide, an integrated system for using up to five filters with the turn of a knob. The focuser itself is the AstroSystems Phase 4, which seems to be mostly a plastic (delrin?) base and metal focus tube and components. I believe earlier versions were all metal, but this focuser is quite light, which may have been a reason for the change. The truss poles arrived separately and have a flexible plastic coating to protect them. The truss poles fit into clamps in the mirror box, and have a cam mechanism that attaches them to the cage ring. Three of the poles had slight blemishes in the coatings that may have been caused in shipping, but I didn't see the need to have them replaced, so when I put them together, I just faced the blemished sides to the inside.

The instruction booklet is over 100 pages and includes pictures and descriptions of all components as well as observing advice and tips. There is also a diagram showing the proper name and picture of all the hardware in case you don't know a hex bolt from a flat washer. The book is spiral bound, which is wonderful; so that it stays open to the page you need when your hands are full. The instructions are listed by group (upper cage, mirror box, etc.) and each listing starts with a parts and tool list necessary for completing that component. It also lists all of the tools and supplies you need to purchase to complete the kit. Epoxy, mixing cups and brushes are included, but you need to purchase contact cement and the urethane and paint for finishing. Suggestions are included as well as advice on how to apply them. I found the instruction book a remarkably detailed guide and anything that was unclear could be cleared up with a simple e-mail. I tended to group my questions so as not to end up with two-dozen separate e-mails that would tend to discourage replies. I was quite pleased with the prompt replies that I received (occasionally within the hour) and can't fault the customer service (Randy is the best!).

My schedule is quite busy, so I set a completion date of March 24, 2001. This would be just in time for my annual Messier marathon. I planned a week long vacation for mid-March and spent the time that became available between then by reading the instructions thoroughly and purchasing the additional supplies and tools.

Preconstruction and Tools

There is a list of needed and suggested tools and parts at the front of the manual. I believe that the most important tools that you will need are eight good clamps and a router. My advice is to get the best router bits available. They only cost about $10 more apiece then the cheaper ones, but make the work much easier. I bought Jorgensen clamps at $14 each instead of the more expensive brand name clamps at $25. I experienced no problems with these clamps but you do have to purchase the rubber protectors separately. I used Krylon flat black spray paint for blackening, and it covered very well. I chose a solvent-based semi-gloss urethane and was extremely pleased with the results. If you can borrow tools rather then buy them, you can save a lot of money but my workshop needed stocking anyway. Be sure that you understand the construction steps completely before beginning that stage. It helps to write notes in the margin and make checklists of the steps.

Construction

My goal was to have the majority of construction completed to the urethane and painting stage before the vacation week. This would allow time for the individual coats to dry before final assembly. The instruction book divides construction into the following stages:

  1. Upper cage part 1
  2. Upper cage part 2
  3. Mirror Box
  4. Ground Board
  5. Rocker Box
  6. Mirror Cell
  7. Truss Poles
  8. Altitude Bearings
  9. Post-construction **
  10. Final Preparation **

** I added these two
The manual addresses these areas, but I found it easier to think of them as assembly steps and will treat them as such.

Upper Cage

This stage consists of gluing the rings to the spacers and attaching the filter slide/focuser to the cage. The filter slide is an integral component that allows the use of up to five filters at the turn of a knob. Be aware that the pictures in the manual are often taken with unpainted and unfinished components to show better detail. The filter slide and cage need to be painted and finished before assembly. Ironically, this was the last component that I completed even though it is listed first. Since the assembly was so basic, I waited until the more difficult stages were nearing completion so that everything could be painted at the same time. The cage rings are assembled using wooden dowels inserted into predrilled holes in the struts. They are clamped overnight and then sanded and finished. The filter slide is temporarily attached with eye screws and screws to mark the location of the tube baffle mounts. After gluing the mounts to the filter slide, it is painted black behind the mounts and finished on the front. The slide is then permanently attached to the cage. Next, double-sided tape is applied to the cage and baffle mounts. The baffle is inserted and the back side of the tape is pulled off while pressing the baffle into the tape to ensure a firm grip. The focuser is attached and the pre-drilled hole in the struts is used to drill a hole through the baffle for attachment of the spider. The secondary holder attaches to the spider, and the upper cage is complete.

Mirror Box

The mirror box is the most critical component to assemble correctly. Any amount that the box is not square means that the mirror cell, truss tubes and rocker box may all be affected. To ensure that the box would stay square, I invested $15 in a corner clamp. This device holds two pieces at a 90-degree angle. Since I was assembling by myself, I applied epoxy to the finger joints of all four sides and then assembled. The eight clamps were applied with four around the top and the other four around the bottom. I left them slightly loose so that when I attached the corner clamp, it would align the panels. I then tightened the clamps and checked the diagonal distance between the corners to make sure that they were the same. Don't forget to check the distance at the bottom of the box!! I remembered an hour after I started, but luckily it was square. My mirror box came out PERFECTLY square. After three days, I removed the clamps and epoxied in the lower truss clamps. There is a spacer that guarantees the truss clamps are identically placed. I used two clamps to hold the spacer to the mirror box, and one more to clamp the truss clamp. Unfortunately, this meant that the truss clams could only be glued in one at a time. I could have used the spacer only for alignment and then removed it while the epoxy cured, but I wanted to make sure that the truss clamp remained in place. Rather then make three additional spacers, I chose to glue the clamps on four successive week days when there was no time for a larger project. This process resulted in results so good, that I couldn't measure any difference in alignment. Next up were the mirror cell blocks. These allow the mirror cell to be bolted to the mirror box. I waited to attach these until the mirror cell was completed, so I will address these in the Mirror Cell section.

Ground Board

The ground board seemed to be the simplest piece to assemble, so of course it presented the biggest problem. The ground board has three feet that need to be attached. These feet give ground clearance, and provide a housing for the bearings that move the scope in azimuth. Assembly is straight out of the manual. No surprises here until later.

Rocker Box

The rocker box assembly is very similar to the mirror box, except that a small amount of alignment error is not as critical. The back of my rocker box is only two inches tall to allow the mirror box to swing out. This causes a potential assembly problem, because clamping too hard can cause the sides of the rocker box to bow in. The kit is provided with a spacer to hold the sides at the proper distance when clamping. This same spacer can be used after cutting it slightly for the mirror box assembly, but I didn't need it then. After drying, pilot holes are drilled and counter sunk in the bottom of the box sides to attach the bottom. Then Formica is attached to the bottom of the box with contact cement. A hole is drilled through the Formica where it matches with the hole in the bottom of the rocker box for the pivot bolt. That's it for now.

Mirror Cell

All of the wood until now has been ¾" birch ply. The mirror cell is much thicker, but still is faced with birch ply. There are CNC routed holes for the locator posts that position the mirror and the sling posts that anchor the sling. There are also holes for the cooling fan, control unit, collimation bolts and handholds for lowering the cell for adjustments and cleaning. Epoxy the posts in and surface glue the transport pads. The transport pads are three wood squares covered with padding that support the mirror when the collimation bolts are turned all the way out. The pivot pins should be temporarily attached to check for alignment in the mirror cell. Push the mirror cell in until flush and mark the inside of the mirror box where it meets the cell. This is where you epoxy the mirror cell mounts in the mirror box. This ensures that the surfaces will mate properly. After finishing the outside and painting the inside, attach the fan and control units. Then the support triangles are attached to the collimation bolts and the sling is attached to the sling posts. The triangles are held in position by a ring that allows them to move independently, but still maintain their relative orientation.

Truss Poles

A wooden plug is epoxied into one end of the truss poles, and later drilled to accept the screw that attaches it to the upper truss fastener. The cam device that attaches the truss tube to the upper cage is installed per the instructions after the fastener is finished.

Altitude Bearings

The altitude bearings are shaped like wagon wheel with spokes. This adds a wonderfully elegant touch that I've only seen on the larger Starmaster scopes. The ebony star Formica is attached with contact cement and then round over the corners by sanding.

Post-Construction

This is basically the routing, sanding, painting and finishing stage. All wood pieces are filled with wood putty and sanded to a medium finish before starting assembly. I found that very little putty was necessary and almost no sanding due to the outstanding quality of the kit. This is where your investment in quality router bits pays off. I assembled all wooden parts as completely as possible before routing. Then with all the parts ready, I was able to do all of my routing in less then an hour. AstroSystems recommends using a 1" flush bit to knock off the bit of finger joint that extends beyond the sides of the boxes. This worked beautifully and made the rounding of the edges much easier. I used a 1/8" round-over bit on all exterior edges of the mirror box, rocker box and ground board. I then put in a 3/8" round-over bit for the finger joints. The only sanding remaining was to fine sand the surface and remove the compression lines from the wood. Compression lines are a by-product of manufacturing the birch ply and look like zebra stripes that usually run across the grain. Patient sanding and a bright light at a low angle will show when they have been removed. The instructions recommend three coats of solvent-based urethane on external wood parts. This includes the inside of the rocker box but not the bottom. All wood pieces should receive an initial coat of 50/50 solvent/urethane and then the exterior sides are sanded and a full-body urethane coat is applied. Sand between each coat and finish off with an aerosol coat for a beautiful finish. I chose to blacken the internal areas before my finish urethane coat in case of over spray errors. Two coats of the Krylon flat black and the internal surface showed no detail in modest light. Remember that the upper cage is easier to urethane before attaching the baffle. Likewise with the upper truss fasteners before attaching to the truss poles.

Final Preparation

Attach the altitude bearings to the mirror box and attach the Teflon to the rocker box. Attach the ground board to the rocker box and the mirror cell to the mirror box. Install the mirror, and then place the mirror box in the rocker. Clamp the truss tubes to the mirror box and the upper cage to the upper truss clamps and you are ready to collimate! Ah, but there was one glitch in the process. The ground board is attached to the rocker box with a brass bolt and bushing. The bolt is drilled for encoder installation, but I found that I could not thread the washer and nut onto the end of the bolt. The picture in the instructions shows a recess on the bottom of the ground board for the washer and nut to be slightly inset. There was no inset drilled in my rocker board and so I had to find a way to inset a 1" circle without making any eccentricities in the existing hole. After several failed attempts, I decided on a MotoTool with a sanding disk attachment. This took approximately 20 minutes of continuous grinding, as too much force would shatter the disk. The final result turned out fine, but a pre-drilled recess or a slightly longer bolt would have simplified things immensely. I should point out that I didn't bother AstroSystems with this problem so they can't be faulted; maybe there was an easy solution that I had missed. The rest of the assembly went without a hitch. There is an extensive description on how to collimate in the instruction manual, along with the pro's and cons of offsetting you secondary. My scope has the optional secondary heater and Sky Commander DSC's. These were easy to install per the instructions. So how does it work?

Under the Stars

If you have been patient enough to read this far, I suppose its only fair that I let you know how my scope turned out. I wanted a more portable, aesthetically pleasing scope then the original Big Blue. Here are pictures of the assembled and broken-down scopes.

As you can see, the AstroSystems body is extremely compact to transport. The weights were surprisingly similar. I had expected a substantial weight savings, but the long focal ratio of the scope necessitated a larger mirror box to offset the upper cage. Both scopes weigh in at 101 pounds. While this is a little heavier then I had hoped, the ease with which I roll the scope out to observe makes up for it. The newer scope also has a smaller footprint (21"x21"), which makes it easier to use a small stool to observe near the zenith. When I attached the Teflon to the rocker box, it is designed to overhang the inside of the box to aid in centering the mirror box. I left my kit extremely tight in case it would have balance problems with my 31mm Nagler. My goal was to complete the kit by March 24th and I beat it by two days. It was ready to test focus on the 23rd. As night came with partially cloudy skies that were getting more threatening, I decided that a quick check to see if all of my eyepieces would come to focus was all that I would try to accomplish. The Phase 4 focuser has 1.2" of focus travel. They must put a lot of engineering into these kits, because when I put in the 31mm Nagler, it focused with more then .25" of in-travel left. Next came the Big Barlow and I was surprised to find that the Barlow could actually be fully inserted into the focuser without bottoming out on the filter in the filter slide. A slight touch of the focus knob and it was perfectly focused. All of my eyepieces came to focus easily with the closest being a 7mm Nagler that still had .25" of out-travel left. The conditions didn't allow any real viewing, so I packed it in to await the next night and the Marathon.

Joe (creator of Big Blue) showed up the next day before sunset, and helped me get set up. We inserted the truss poles into the clamps, slipped on the shroud, and attached the upper cage. Even though I own several other scopes, I decided to only use Big Blue for the night. Joe had brought along a nice Orion 10" reflector and a 5" Schmidt-Cassegrain. I was tempted to get my 80mm fluorite, but decided that it would be an unnecessary addition. My rough collimation of the night before needed only 1/8th of a turn of one of the collimation screws to become as good as we could get with the Cheshire. Even though the scope was disassembled and transported, the scope was amazingly easy to collimate. Some of this was due to the f/6 ratio, but I was still impressed. Slipping the 31mm Nagler into the focuser provided me with a wonderful view of Jupiter in the twilight. A simple twist of the filter slide knob put my 80A filter in position and knocked down the brightness to allow the main equatorial bands to be visible at 60x. I pushed slowly down to acquire Saturn, and the motion was smooth and precise with no backlash. I tentatively removed my hand from the scope and it stayed put, even with the weight of the huge Nagler and the relatively low angle of the scope. No detail was noticeable other then the rings, but Titan was a perfect little diamond chip. By now the sky had darkened enough to pick out several bright stars, and I aligned the Sky Commander using Rigel and Regulus. I didn't bother putting a higher power eyepiece in the focuser, I just guessed at the center in the Nagler and Okayed the alignment. For the rest of the night, the Nagler lived in the focuser and anytime I set the DSC's to a target, it appeared neatly centered in the field of view.



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