Eyepiece and Laptop Rack
Submitted: Monday, 29th January 2007 by Stephen McNelley
This article describes an eyepiece/laptop rack that I devised for a 10” Dobsonian base. Originally I built the rack with a notebook computer in mind, but there was just one problem…. I didn’t have one. So with the rack built and screwed solidly to the base and doing nothing I surmised that this small laptop table would be a useful holder for eyepieces if I took to it with a hole saw. After matching the 1.25 and 2 inch ep barrels to the right hole saws and some careful spacing measurements on the plywood board I set to work, 30 minutes later and a bit of a clean up with sand paper there was an eyepiece rack that could fit 16 ep’s, and it could be used to fasten other useful goodies to also.
This version was built from waste timber- plywood and Tassie oak using wood glue and some suitable loose screws from the loose screw department, but any materials could be used for construction. Alloy would be very good weight wise, but it might also vibrate more with push/pull directional changes of the scope, timber is more quiet when changing ep’s- something to consider late in the night if you have neighbours nearby. I won’t go into the rack construction in great depth, hopefully the photos explain most of the details and the images here are of an experimental design that has rough edges.
Planning it is just a matter of measuring the few angle’s involved from your base to the rack and the desired rack position in relation to it’s four supporting struts, the height you want the rack to be when sitting viewing and some simple common sense- your Dob base and it’s customising is a very personal thing. For this project we only need a protractor or an angle measure maybe, a tape measure, a tennon saw, a vice, decent wood glue for joining and then screwing all the members together, two or three G-clamps for aligning the two main rack struts to the base before drilling and fastening the whole rack, and some appropriate screws loose.
I found the most important consideration was how you fasten the main rack struts to the inside (outside might work to, giving a wider rack) of the Dob base frame walls. You need as thin a timber as possible because there is not usually much clearance between the OTA and the inside Dob walls, and you don’t want the rack’s mounting struts to rub on the tube when it swings through altitude. Yet these two supporting strut members need to be strong- Tassie Oak does the job yet it is a fairly light pine. Countersunk screw fasteners are the best choice for the whole thing from a functional/aesthetic perspective as they sit flush in the timber. Also, being careful not to drill your small pilot holes for the screws all the way through the Dob upright frames, and matching the length of the screws to the strut timber and frame widths pays big dividends. Use the G-clamps to help hold the two main rack struts to the Dob base as you align the whole rack, and tighten them well before you drill the small pilot holes through the struts and Dob frames for the counter sunk fastening screws. Again, try not to drill all the way through to the outside of base, as I did…
Before you drill, make sure that the telescope tube does not hit the rack itself when the scope is pointing straight up and at its maximum altitude travel on the mount, a cm of clearance between the scope and rack will be ok. Lastly the rack has to be just high enough so that you can drop the nose of the scope to a horizontal level and the mirror end of the tube doesn’t hit the rack or any ep’s that are sitting in the rack, this is where the G-clamps come in handy for adjusting the rack position before drilling and fastening.
With this rack, once the thing was trial attached to the mount, and I sat down and got over my amazement, I removed it and sprayed the whole thing with a cheap flat black enamel. Viola, very chuffed.
Now that I have just begun to image the Moon and planets with the 25cm Dob the rack is fulfilling its intended role very nicely, cost nothing too and the two extra alloy ep holders I made and screwed onto the left side of the base accommodate the ep division with ease if required when it is laptop time.
Included are some images of the wide wheelbase Dob transporter trolley, which doubles as a height adjustable viewing seat. The two short steel forks bolted to the base lifting plate give a little more lifting leverage and stability when hauling, and also make sitting on the thing for viewing more stable and it is less likely to tip forward as you peer into the cosmos. The wider axle cost $4 from a steel engineering shop, just take the old one in and say “G’day mate, I need a longer one”, 650mm gives a much more stable ride and the trolley still goes through normal doorways fine.
All that’s needed then is two tube spacers/sleeves to stop sideways slop in the axle between the wheels and the trolley frame, and to drill small holes through the axle ends to fit your wheel retaining split pins- the engineering shop would probably do that for a few $. Hopefully the images explain the details.
I built this trolley seat as a trial experiment a year and a bit ago, low and behold if I am still using it as is and are always vowing to one day ‘make a better looking one’.