OBSERVING LADDER. I use a six foot ladder. I added about three additional rungs between the bottom three rungs, so now there's a step every six inches or so. Once I got over the initial strangeness of a ladder with such close spacing it was very comfortable to use! I don't remember any object/observing height where I could not find a rung to step on that gave a comfortable observing position. There was no neck craning or stooping needed! Also, a six foot ladder leaves enough ladder above me that when doing high mag observing I can lean/rest my torso/shoulder on the upper parts of the ladder for steadier viewing. A good ladder helps for longer/comfortable observing.

COLLIMATION. Using only a cheesy, home made sight tube and peep hole this f/6 system only may need one minor tweak of collimation adjustment with the star test. . .if the seeing is good enough. A laser collimator is not needed.

STAR TESTING THE OPTICS. Seeing was not very good, but this mirror looks better than my ten inch inch f/7. . .especially in the outer zones where the most mirror area lies. (My ten inch tests as a bit better than 1/6 wave and less than 1/8 wave. The sixteen inch's outer zones star test as clearly/obviously better in the outer zones) The very inner zones of the sixteen inch (only out to a radius of about 2 - 2.25 inches, which is a small portion of the entire mirror's area) are a bit overcorrected but beyond that area the star test is very good. I still need steadier skies for a more definitive result. This is a good mirror! I may not star test again until spring/summer or whenever I get much better seeing. This mirror is plenty good enough to enjoy right now and at this point additional star testing may only be good for the ego and bragging rights around the water cooler ;-)

SPRING COUNTERWEIGHT SYSTEM. IT WORKS! Just like the paper analysis, it works! (To make things more in my favor I use larger - 22 inch diameter - elevation bearings with a 90 degree Teflon pad spacing. This means I don't need to change counterweighting setups when swapping between heavy two inch eyepieces and small 1.25 inch eyepieces. (The friction in elevation motion is a bit higher than I'm used to. . .I may scoot the bearing pads a bit closer together.) The setup I'm using replaces the need for about 15 pounds of counterweights at the back of the mirror box (the scope is about three pounds nose-heavy without the springs.) and allows my mirror box to be about four inches shorter than without springs. . .now it'll fit through my car door! Stuart Field deserves the credit for the theory and geometry of the spring counterweight system - it couldn't have been built without his contribution. TECHNICAL COMMENTS...

SPRING COUNTERWEIGHTS-2. Continue to work well! A lucky break: Since I use two springs (one on each side of the rocker box) I've found that when I unhook one of the springs and put a light/1.25 inch eyepiece in the focuser. . .it's almost perfectly counterbalanced!

MIRROR FIGURE. After about an hour of cool down time I was able to do some rough star testing (more accurate testing will require better seeing, making a 33% obstruction, and closely examining Suiter's diagrams). A wee bit of over-correction in the very inner zones visible with a 7.5 mm eyepiece. . .I can't see problems so far in the outer zones. (This mirror may be a better figure than my ten inch!) I wonder if the little bit of over-correction is partly due to the rapidly dropping air temps last night? Need more testing in various conditions RTV gluing mirror to cell: No warping noted from RTV glued method to the mirror cell. (Not really new news here, as Mel and others have mentioned before)

SIX POINT MIRROR SUPPORT. No image degradation noted. (Need better seeing to get more critical tests.) Not bad for a 1.6 inch thick mirror!

MIRROR BOX BAFFLING. I've noticed that some large dobs with open/tailgate mirror cells don't baffle the back of the mirror box. I've temporarily taped some strips of flocking paper across the back of the mirror box so that you can't see the ground/grass from the eyepiece. I didn't get a chance to compare this to other non-baffled scopes, but it was easy to do and certainly can't hurt. Still plenty of room in back for air flow.

UPPER RING (instead of a secondary cage/cylinder). It's frequently breezy (or worse!) on the mountaintops, and the upper ring design is fantastic for this! Even in light breezes the 36 inch nearby was moving and bobbing and required hands-on steering to counteract the breeze. . .but my scope was barely moving (about 1/4 of Jupiter's diameter in light breezes. . .at least less than the planet's diameter in most breezes). In higher breezes. . .when many big scopes (especially those with shrouds) were having trouble staying put - the sixteen inch could still be used at lower powers. In really high winds the secondary vanes (or maybe the truss tubes?) start fluttering/buzzing and the image moves so rapidly that it's blurred into a useless mess. The flutter problem in high winds is the limiting factor here, not the upper ring/low wind profile design. Great concept! Thanks to Mel, Bruce, and others for this idea!

TRUSS TUBE ATTACHMENT METHOD. I didn't make fancy clamps (too lazy and cheap), I didn't crush the tubes flat (didn't want to mess with a torch or risk cracking tube walls). I inserted wood dowels in the tubes' very ends and drilled mounting holes. The truss tubes bolt to mirror box and upper ring. At upper ring I have only ONE attachment point for the each pair of truss tubes, not two mounting points like you often see in truss tube scopes. Why make twice the mounting hardware for the upper ring? It may not look as slick as other mounting systems, but it works fine.

FOCUSER AND UPPER RING BAFFLING. Works well! After the sun dropped below the horizon I observed the four day old moon. . .I didn't side by side compare with a solid tube newt, but the contrast appeared good. By pulling my eye back about four inches from the eyepiece (use a long focal length eyepiece for this test) I could see the secondary and primary mirror in focus. . .and baffling material. . .and nothing else. . .which is what you want. By moving my head to the side (to examine the edge of the field of view) I could see if the baffling was the only thing visible at other angles. It was. The baffling layout works well if you don't try to use a low profile focuser setup. In case I observe in a street light infested area I've made my focuser bottom baffle aperture removable. I can insert a smaller baffle that allows the eyepiece to "see" only the secondary mirror. . .and very little else. It will limit the size of the unvignetted field a good bit, but may help improve contrast in tough street light situations. For observing in daytime I'd probably also rig a sun shade (or short/half shroud near the mirror box) to make sure no sunlight falls on the mirror and inside of mirror box.)

FILTER HOLDER. I mounted my helical focuser to the upper ring by making a short wood box to provide mounting points for the focuser base and baffle just below the focuser. In between them I set up a system for quick change filter capability by cutting two grooves in the wood box. The two inch filters (colored glass for planets and nebula filters too) are mounted on squares that slide in/out. This may not be as fast/easy as a long slider bar with several filters, but that can get rather large with four or more two inch filters. I think it works pretty well. . .especially when "blinking" the O-III filter to find planetary nebulae or showing how much more visible the Veil nebula is with/without the O-III.

TAPE MEASURE SETTING CIRCLES. Work well! After aligning on the crescent moon I dialed in Vega and Altair in bright evening twilight. Also found Uranus in darker twilight. At one point in the night I was observing with a 170x eyepiece and four objects (in a row!) I dialed in on the setting circles were in the eyepiece field of view! Who needs a low power eyepiece? Still looking for a surplus (i.e. inexpensive!) penta prism. . . .

This thing rocks! Nine-point supports are not needed at this aperture and thickness! Spring counterweights work as designed at all elevations!

Major Tom Krajci USAF