Frankenscope Miscellaneous

Made a reason    Made a dust-proof, padded case of luon plywood for the OTA--aka "the casket".  Scope base w/its delicate bolts rests on padded studs; there is extra padding and studs to protect the focuser and finder, too.  The case is made of medium-grade ¼” plywood on aluminum angle and bar stock—weight is about 20 pounds.  It was made to fit in my car, which it does, only I forgot to compensate fully for the “slant” of the rear-hatch, so in practice the scope gets transported loose.  Still, this makes for a secure environment for securing the scope if I have an extended period in which I don’t contemplate using it.  NEVER USED IT EVEN ONCE! A waste of time and money...

                                    ·    Mirror cell stored in its shipping container for the first 9 months.   Part of this time simply used the (not too soft) tissue paper to cushion mirror face, since that is how previous owner had stored it.  Later lined the styrofoam w/ultra soft fabric remnants  from “America’s Astronomy store” (aka Walmart).  Finally made a sturdy mirror storage box from left over luon plywood and 2 X 6” scraps.  This lets me suspend the mirror (face down) by its rim w/face in mid-air.  Box lid houses my Hartman mask.  Box doubles as a second table surface in the field (never enough room to put all my stuff as unpack)

                                    ·    Magellan I—added more for its interface w/my laptop (same way I use my LX200) than because enamoured of it in its own right.  Added quick release mounts made from PC power connectors to the azimuth wiring, since the base needs to be taken apart for transportation.

                                    ·    Removeable laptop tray—doubles as place to park eyepieces.  Gets in the way of looking flatfooted at zenith (have to go on tip-toe like w/default trunion position), but handy enough that leave on all the time. UPDATE: ended up making this larger so could accommodate imaging gear when not in focuser, plus a few ep’s, and a larger laptop.

                                    ·    Added larger/more comfortable handle to mirror disk

                                    ·    Scope no longer bears “Meade Starfinder” logo—at this point I’ve invested a lot more time into tweaking it than Meade did to building it and don’t think I need to bear their logo!  (I’m thinking of calling this “Frankenscope”.<g>  It’s probably in the running for ugliest Dob, but I go for function, not aesthetics…)

·        Made an off-axis mask (7” dia hole) for planetary use.  When started trying CCD work, added two holes (triangles, so can line up angles like diffraction patterns) as Hartman focusing mask.  All three holes have cardboard covers that can be velcroed in place when don’t want that particular opening, and velco to hold the covers when I need those openings free.  The mask fits in the lid of my mirror box (which itself doubles as a low-lying table).

·        Made a dedicated solar viewing mask.  (already had Baader filters from my LX200 Kendrick Kwik focus).  Debated using the existing off-axis mask, but decided for safety’s sake to have a dedicated one w/no extraneous holes (plus I would have had to make their masks much more secure—big difference in consequences between having one fall of at night vs. day.).  Mask is secured along entire perimter by velcro—requires a lot of force to put and off manually, so not worried about it blowing off.

Have always been plagued w/mediocre slewing accuracy.  Assumed was “slop” in quick-release base or moved trunions.  When ground board and rocker box were level, the top of the vertical tube was off.  Finally used a large T-square and a level to determine that one trunion was 3/32” (~2mm) higher than the other.  Adjusted it.  Interestingly enough, still found vertical top of scope not level (now worse than ever).  Measured and found out that one side of OTA is 3/32” longer than the other—presumably Meade didn’t cut the sonotube square when begain scope making.  Raises the question of whether it is the top or the bottom that is off… (does it matter?)

I debated long and hard whether to re-make Frankenscope’s optics into a truss tube Dob configuration, but ultimately opted to stick with the current configuration because it is faster to set up than a truss tube package –if the scope needs to be reassembled for each session—and has better light baffling (a tube beats a shroud!). Both factors were important, since I tend to use it a lot for front yard viewing, where I can be set up and tweaking the collimation in five minutes.  The reality of a truss tube set up is that if I had to do that much setup/take down, it would only see use in the field, i.e. a couple of times per month at best.  If aperture fever strikes again, though, you can be sure my next scope with be a truss tube Dob—possibly a folded light path Dob, since I’m partial to keeping my feet on the ground when observing. I wonder how large one of those could be—I was briefly tempted by a 22” folded path on Astromart that would have been at my eye level pointing at zenith…

Dob Driver II—required scrapping the lazy susan/Ezglides that made the azimuth so easy to turn.  Installing the DDR2 itself was pretty easy, however, I had opted to modify a suggestion I found on Jim Fly’s web site to use a De-Sta-Co in-line clamp instead of default turn screw as clutch for azimuth.  Bought two models, and had several false starts (resulting in extra holes in base board !) before I got it in a location where would take the load off wheel.  I then found that the lighter De-Sta-Co clamp could not deal with the considerable weight (200#?) I was trying to lever—it stripped on the second throw!  I moved to the larger clamp; had some issues w/accomodating it’s larger footprint, but got it to work.  Had initially mounted a Teflon foot to its “business end” but through concern that this might fall off and cause the unshielded metal to score the ground board, I replaced the foot w/a teflon strip afixed to the base board, much like the DDR2’s default screw clutch.  I retained the default turn screw to use in tweaking amount of weight azimuth wheel would have to bear.  In practice my clutch works very well—being able to simply throw the lever and move the scope manually makes a big difference in usuability, since the slow slew speed (~3 deg/sec) would result in up to 3 minute slews if trying to re-orient the scope 180*.

Manually the scope no longer has that super-smooth motion (feels more like a stock Star finder now) in azimuth, but was a worthwhile tradeoff to have tracking.  Frankly, since only use manual movement for gross shifting before turnning to DDR direction pad for fine movement control, could argue how easily scope moves manually is now essentially moot point anyway.

Ended up trying to tweak the balance—with all this stuff hanging from the scope, the center of gravity moves considerably between zenith and nearly horizontal position.  Ended up w/weights on bottom side of tube; progressively moved them farther down towards mirror cell end.  Since on bottom side, gravity wanted to pull them off—ended up adding more velcro and eventually having “wings” to stabilize mid-section of each 5 lb belt

Usage notes:

·        Use an illuminated reticle (Siebert 26mm) in finder