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Yes, if you have one of these things, we all do it - sooner or later, we loosen our polar scope recticle too much and it falls out and rolls around inside the polar scope. This makes polar alignment impossible - but it's very easy to fix! The trick is in understanding how the polar scope is put together... let's take it apart for a look. The polar scope will easily unscrew from the mount. Once it's out, hold it vertically with the "eyepiece" side facing up and the "objective" side facing down, like so:
The "eyepiece" end of the polar scope unscrews. Remove it, and you will expose the loose recticle. At this point you can just empty it out into your hand if you'd like to have a closer look at it, although it's not necessary to completely remove it in order to fix your trouble unless for some reason the glass recticle lens itself has fallen out of its holder. More on this in a bit. Here's a picture of the recticle itself:
Note that there's a larger "outside" ring that is the "holder" for the glass recticle, and a smaller ring that screws into the larger ring to secure the glass recticle lens in place. In the very unlikely event that this holder assembly has come apart, just drop the glass lens in place as shown and tighten the smaller ring into the larger ring with a small "jewelers" screwdriver until the recticle lens is snugly held in the metal "framework". Be careful not to over tighten the inside ring as you could shatter the recticle glass! Just so you have an idea of what it looks like, here's a look at the back side of the recticle:
Now, the whole reason we're taking this thing apart in the first place is probably because we loosened one or more of the adjustment screws too much and the recticle assembly fell out as one piece. Fortunately this is an avoidable problem. The recticle is designed with a flange (or slot, or channel - pick the word you like) that will retain the recticle in place if we don't loosen it too much:
If you look down the disassembled polar scope towards the objective, it might look something like this:
In this case, note that one adjustment screw is way out (unscrewed) and one is not. This one screw was loose enough to allow the recticle to just fall right out. Notice that if it had not been loosened so far, the recticle would have still been held in place by the flange. Keep this in mind when you are adjusting the recticle for accurate centering later on. However, now that the recticle *is* out, it might be prudent to loosen the other two adjustment screws so that they do not extend into the area that the recticle needs to fall into. These adjustment screws require a 1.5mm allen key, by the way. Once you've unscrewed the adjustment screws enough to clear the opening, just drop the recticle into the polar scope with this side facing you. Now that nothing is in the way, it should be pretty easy to get it right:
Now, tighten the adjustment screws up until the recticle is roughly centered in the housing. They should be tight enough to hold the recticle firmly in place, but definitely not "cranked down hard"! You could ruin your recticle if you over tighten it in this "holder"! Once it's in place, it should look something like this: 
Now that the recticle is back in its holder, you can thread the "eyepiece" back in, looking through the "eyepiece" and continuing to screw it in until the recticle is in sharp focus. Then just thread the whole polar scope assembly back into the RA axis of your mount. Problem solved! Once the recticle is re-installed and we have the polar scope re-installed in the mount, we will definitely need to re-align the recticle to the RA axis of the mount. Accuracy is the name of the game at this stage - the more accurately the recticle is aligned, the better your chances are of getting really good polar alignments using the polar scope. At this point, I could go through a discussion of the whole procedure for accurately lining up your recticle to the RA axis of your mount, but instead I'll direct you to one of the best explanations on the web for how to do this that I've ever found: Instructions for aligning your polar scope recticle
Good Luck and Clear Skies!
Charlie |
