Get a grip

[Ben the Ignorant]

Hi.

I had an old-fashioned 7x35 binoc that was not worth much except as a spare parts donor, the kind with hard eyecups and so-so optics. Components that proved useful here are the rubber front rings, by chance they have the ideal diameter to fit my dobsonian's (single-speed) focuser wheels. I only wanted a small increase in girth to make focusing somewhat more accurate, a better grip, and to forget annoying cold metal against the skin. The larger diameter does add a small amount of accuracy, but the improved grip does much more to accurize focusing, unexpectedly.

Why is that? I had never realized it, but finger flesh squashes noticeably on the metal wheel before it starts engaging the grooves, plus the semi-gloss aluminum kinda slips under the fingers, and that slack makes focusing rather tedious at f/5. I didn't feel a need to install a double-speed focuser because the taiwanese machining is excellent, and after experiencing the touch of instant grip I feel I approach the precion of two-speed focuser, anyway, but without the ultra-convenience of demultiplication of course, you need all your dexterity.

Hard to believe unless you try; I would have had a hard time believing such a cheap simplistic mod could do so much. A friend informed me that some observers buy toy car rubber wheels to get the same effect. I recommend the mod even if the increase in diameter is not much, just removing the slack does a little miracle for minute adjustments. The rings fit the wheels very tight as they are, however I'll add droplets of wood glue under the rubber because tales of lost items on the observing field are real (weak glue leaves the mod reversible).

A similar job was done on my Celestron 5's right ascension knob, it went from 25mm to 33mm, enough to gain accuracy but not as much in this case because the gears are not as precisely machined as the smooth rod and plate in the GSO's crayford, and the mass that's put in motion is several kilos.

A water bottle cap was press-fitted on the knurled knob, after which a rubber ring from another super-cheap junk bino was slid over the cap. No one would know it's a mod unless they are told so, or they know the original Celestron thingy.

Another reason for rubberizing knobs is noise, those on my EQ-3 are shiny plastic, cold to the touch, and squeaking like a mouse is roaming around when I turned them. Here are the low-price binocs I took the rubber from, and the knobs that were garnished with it; the objective housings are now bare plastic but the lenses were removed to make a magnifier, anyway:

The next rubber mod is not about grip. Steel nuts and bolts outside the dovetail would bump against my AZ-4 mount's arm, causing nasty noise and risking chipping the paint. Having several more leftover rubber rings (from the eyepieces this time), I first replaced the standard 1/4" steel nuts with the round plastic camera platforms you receive for free with mounting rings. Slid the rubber over the disks, voilà! No damage, no noise.

Aluminum is cold at night, and I had plenty of large O-rings left after buying a box for the smaller ones. I hate to leave things unused, so I wrapped my red flashlight in an assortment of O-rings and cheap binoc covering for the grip, the warmer contact on the hand, and also the look after I noticed the professional or "tough gear" appearence. No chance of dumping this flashlight, it seems to stick to the hand, moving the aim from the "front" to the "down" position is very swift, and done without any apprehension of fumbling or letting it slide out of the hand. From the atlas page to the eyepiece stand in confidence. Felt good so I did the same with my everyday carry white flashlight:

Recycling at work! Hope you picked up useful ideas for yourself.