The Markless™ Counterweight System
is a sliding, adjustable system which can be used to quickly re-balance your Obsession® Telescope (or almost any other Dobsonian mount Newtonian reflector truss telescope) when you have changed eyepieces, and/or added/removed something from the Upper Tube Assembly (UTA). The barbel weight typically used (2.5 lbs. for larger scopes) is not included because it costs more to ship than its purchase price at Wal-Mart™!
Four sizes to choose from: MCW-25, MCW-20, MCW-18, MCW-15. The MCW mounting brackets fit only Obsession Telescopes, but the sliding board can be attached with optional wood screws on non-Obsession big Dobs.
“But wait, there’s more!” That familiar proclamation is the introduction for a new optional component to the MCW. For reference, I call it the Front Counter Weight, or FCW. I know that isn’t very imaginative, but at least we can have a discussion and not get confused! The FCW fits any big Dob telescope and is custom made to order.
The purpose of the FCW is to keep the center of gravity of the counterweight system coincident with the mechanical axis of the telescope so that the telescope is properly balanced regardless of the elevation of the truss tube assembly. I have tested it and it works exceptionally well. In practice, one would split the total sliding weight between the MCW and the FCW. For example, if you used 5 pounds of sliding weight, you would put 2.5 pounds on the MCW and 2.5 pounds on the FCW. Most of the time, you would not need to adjust the position of the FCW weight.
The FCW construction is simpler than the MCW and is not "markless". That is because the front transom on Obsession rocker boxes is in the way of using a bottom Markless bracket. The FCW will require two #8 screws (supplied) for mounting. I think the overall improvement in balance is worth it. The accompanying pictures shows the FCW (and the RCW) in place on a 12.5” Obsession clone. They have 1.25 pound weights attached. Different sizes of FCWs are available for each Obsession and any other big Dob, so please indicate your Obsession model or your telescope's mirror box dimensions when you order.
The Rear Counterweight (RCW) is very similar to the FCW in style and construction. Like the FCW, the RCW is not "markless". It mounts with stainless steel sheet metal screws. However, the RCW has a safety cable like its older cousin, the MCW.
As with the MCW, the barbel flat plate weights are not included because their shipping cost is greater than the cost of the weights. However, I have located an excellent source for the weights and they have all of the small sizes (down to 1.25 pounds) in gray, black, and even chrome! Even their S&H was reasonable. Write me for the link when you order.
Pricing summary:
North Carolina residents please add 8.25% sales tax.
To order, or for more information, email me at cs(at)marklessastronomics dot com
Charles Starks, Charlotte, NC
Astrocrumb Filter Slides - a "MUST HAVE" accessory for your Big Dob. Roger builds 'em RIGHT!
Copyright 2003-2010, by Charles Starks, Charlotte, NC, All Rights Reserved
Updated: 4:31 PM 1/26/2010