Celestron Polar Finder Scope

So. I think I managed to align the axis of the Polar Finder Scope with the polar axis of the CGEM mount.

There were a few mishaps and holdups.

In Grasslands last weekend I learned that my compact allan key set did not have a key that fit, and while Kevin loaned me his I gave up quickly, and also became annoyed that the PFS is not sold illuminated (useless otherwise).

This afternoon I figured that to get started I needed to find the correct size allan key. But when I pulled out the scope upon arrival, it appeared to be missing two of the three reticle adjustment screws. So I hitched a ride with Ned and John to B&E to replace them. B&E did not have a set of allan keys, but we found imperial screws that fit, though couldn’t tell if they were getting caught up, or were depressed as much as they could be. So we found another little hex toolkit to try to remove the last remaining adjustment screw and ooops. I turned it the wrong way and it went and fell in to the body of the polar scope.

Handy B&E dude showed me how to simply unscrew the entire eyepiece, and we found all three screws at that point. It seems that one scratched the far end of the glass, but along the edge, not in the centre. When I put it back together the screws held the entire eyepiece in place – so that it could not be spun around, apparently to focus. This confused me.

How, I needed to know, am I supposed to orient the reticle correctly to align it with the big dipper (thinking that this was the task of the eyepiece, after confirming that the year/date chart were useless), and with Polaris, if I can’t move the thing? I eventually read the “Using the Polar Finder” section of the two-page instruction manual to learn that
all one needs to do is to move the RA axis until the pattern matches the orientation in the sky. Then use azimuth and altitude knobs to get Polaris inside the circle. I suppose, then, that the RA axis alignment marks become void, since the new position of the RA should probably not be changed once Polaris is positioned within the scope, and thus the mount more finely polar aligned. I will have to sort this part out.  update, 10 March 2013. I just posted this today, and looking back realized I’d forgotten I identified moving the RA axis back in October. However, my supposition was wrong: once Polaris is positioned in its circle in the polar axis finder scope, return RA and DEC to home position, with arrows aligned, then power up and run through the 2-star (then ‘all star’ if preferred) routine.

So. I took out the mount and tripod and chose the fartherst object I could see from the concrete sculpture pad on the academic green. I find controlling the altitude adjustment bolts to be a pain. The big fat one at the back moves the altitude up just fine, once the smaller front bolt is loosened. But the only way I can figure out how to move the altitude down is to simply loosen both and push, in the small increments it permits. The azimuth knobs are a little less finicky, though it moves more smoothly clockwise than counterclockwise (I just now read that only at this point should the mount be tightly bolted to the tripod. It’s the last instruction).

Once I’d centred the object, which had a handy cross-shape at right angles, it dawned on me that I’d chosen the wind tubrine. I held my breath and hoped the wind didn’t pick up and proceeded. Then I read the part that I’m not trying to centre the cross-hairs on this object, but on the axis of rotation. Okay.

It took more than the 3-4 swings back and forth of the R.A. axis to get close, and maybe because I feared completely loosening and loosing, or tightening and loosing again within the eyepiece, those tiny screws. And I didn’t get it *perfect*. But I got it pretty darned close.

I have very little confidence that the Polar Finder Scope is sturdy enough for those screws, or the reticle, to actually hold in place, but I put back on the caps and I am ready to rig a way to illuminate the polar axis shaft.

John has a great idea about that. In my last post I linked to Marueen’s rigged t-tube with flashlight. John wondered if I could get my hands on a small strip of photo-luminescent paper and simply cut a couple inches, loop it to fit the insert of the polar axis hole, and use a small battery to power it. That would be really cool and if Rebecca has any spare bits I will definitely try it. It would be compact, easily inserted and removable, create no visible obstruction, and wouldn’t require any more hardware than a way to affix the battery. I’ll post about that if I get to it.

Now all I need to do is find a night to go out and actually sight Polaris using the Polar Finder Scope…..