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Finderscope way out of alignment


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A bit of a daft problem I'm afraid.....

I'm trying to align my Explorer 150's finderscope but when I tighten the holder into the shoe (correct terminology?) on the scope, there is way too much play and the finder ends up a long way off parallel with the scope, so much so that the alignment screws don't bring it anywhere near back in line. I tried not tightning the shoe screw as much but then the finder just slides out.

Am I doing something wrong, or is it just the case that I will need to pack the shoe with something?

Thanks for any help, I'm getting frustrated! :)

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had exactly the same with my explorer 150 used masking tape wraped round the finder to pack it out then uses insulation tape round the finder and finder holder just for good measure

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Have you assembled the finder correctly? There is an "O" ring that goes in a groove in the finder tube (about half way along). The finder goes into the holder eyepiece end first until the "O" ring slides into the end of the holder (about 5mm). The eyepiece end of the finder shold be at the same end as the adjustment bolts.

I hope I've not offended with oversimplification but you can assemble 'em the wrong way round!!

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I find that sometimes it's the shoe that's out of alignment. I would try this:

  • Loosen the shoe bolts a little until it can be moved a bit (but make sure the nuts cannot fall onto the mirror).
  • Adjust the finder bracket screws to a half way position.
  • Put the finder and bracket in the shoe.
  • Use a wide angle eyepiece (eg 25mm plossl) and find Polaris or another obvious target. Polaris is better as it won't move.
  • Look in the finder and without moving the scope adjust the finder and base until you see the target in the centre if possible.
  • Again don't move anything and mark the position of the shoe with maybe masking tape or insulation tape etc.
  • Remove the finder and bracket and then ensuring the shoe has not moved, tighten the bolts in that position.
  • Repeat the finder position check and hopefully this time it will be close and need only a tweak each time.
  • Sometimes I use double sided sticky foam to ensure the shoe stays put.

Hope this helps.

Shane

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The rubber "O" ring around the forward part of the finder tube is the key here as Bizibilder says. It keeps the finder tube tightly in the front part of the finder mount. With that in place you won't need any packing. Without it, the front end of the finder tube will flop around.

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Wow guys, thanks for the fast replies, this forum is awesome!

The scope is second hand and was already put together, just removed the scope and mount to transport it.

@ Bizibilder, thanks, the "O" ring was hanging around the base of the holder. I had wondered where it should be! (Oh, and the more simplification the better at the moment, lol)

After placing the "O" ring the movement is slightly better but I think I'll have to pack the shoe a little.

@ MorningMajor, thanks for the cable tie suggestion, I will try that.

@ tbird, thanks for the pic, helped to make sure I had it right.

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@ Moonshane That was it, the shoe wasn't aligned parallel to the front of the scope! (I should have thought to check that :)). I unscrewed one side slightly and it seemed to "kick" into position as if it had been tightened out of its natural placement.

Thanks for all your help guys, this really is the most helpful forum I have ever had the pleasure to be a member of. :(

I just need the clouds to shove off now, so I can get a decent look at Saturn & M42 amongst others (full moon allowing). Been using a 76mm Optus reflector (;)) for the last couple of years and only now have I had the money to get a decent scope (albeit second hand) :p

Thanks again all.

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I only wish the membership had a cloud blower we could lend you :)

Lol, that would be lovely but I'm sure I would be quite a way down the queue!

I've just come back inside after an hour ogling M42 - the first time I've ever seen the dust and it absolutely blew me away. Averted vision helped massively as well.

That was over the city with very bad lp so I can only imagine what it will be like on Ardnamurchan in western Scotland when we go in October - can't wait :(. We've sat for hours looking at the Milky Way and watching umpteen satellites every time we've been - even the wife is getting excited!

Waiting for Saturn to rise above the neighbours now and will check out the moon as well - came in because of cloud but it seems to be clearing again.

Oh, and the finder worked flawlessy!

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