Polarscope reticule adjustment.

[sophiecentaur]

I recently bought an 'unused' s/h EQ3 Pro (literally never used afaics) and I noticed that the polariscope reticule was not 'upright' in the eyepiece with the mount in the home position. I read that this is not uncommon and that it often needs to be aligned. I loosened the grub screws after removing the eyepiece and easily managed to rotate the reticule. But , clumsy, I slackened the grub screws too much and out came the reticule. Having cleaned it up and replaced it, I found that the three screws  were difficult to adjust relative to each other in the way I would expect. Slackening one screw doesn't allow the other two to be moved. Centering the reticule whilst rotating the RA is hit and miss and, even when the screws are tightened, the reticule (or lens?) seems to fall about inside so the alignment varies by several minutes of arc. The reticule seems firm in its ring and the EP lens also seems firm. In such a basic system, there doesn't seem to be anything else that could be loose. Have I missed something (or dropped a spacer ring or something) or is there a secret to getting the reticule mounting to behave itself? Perhaps loads of grease in the groove?

PS Why doesn't the reticule have the Dipper and Casiopea on it - only Octans? On my NEQ6, lining up the Dipper using both eyes and placing polaris where the polariscope app tells you to gives very good tracking  - enough to allow exposures of a couple of minutes without star trails - so it's pretty adequate for most purposes. 

[JamesF]

The reticle has Octans on it because there's no useful pole star in the southern hemisphere.  In the northern hemisphere all you need on the polar scope is the pair of circles, one of which indicates the path of  Polaris about the NCP and the other the position of Polaris.

I found my EQ3-2 polar scope awkward to adjust, but it was already ten years old by the time I bought it, so I can't speak for what had been done with it beforehand.  I think I ended up putting an O ring around the non eyepiece end to help stabilise it inside the RA axis.

James

[johninderby]

I like my old Telescope Express one. Fits into a 6x30 finder bracket. Not illuminated but better optics than normally found in a pole scope.

Edited September 22, 2019 by johninderby

[sophiecentaur]

3 hours ago, JamesF said:

 

  I think I ended up putting an O ring around the non eyepiece end to help stabilise it inside the RA axis.

James

That brings me to another question. Everything was torqued up very tight and I could find no 'civilised' way to unscrew the polarscop from the tube it sits in. (I assume the thread on the polariscope goes into a threaded bore). I looked for a set screw, holding the scope into the mount but found none .  Do I need to get out my large stilsons?

3 hours ago, johninderby said:

I like my old Telescope Express one. Fits into a 6x30 finder bracket.

Sounds good and easier to get the head to it in the home position than kneeling down with your head at an awkward angle. I imagine the reticule needs a bigger range of adjustment, though.

But the question still stands about the wobbling reticule. It's disconcerting. 

[Captain Scarlet]

7 minutes ago, sophiecentaur said:

... Do I need to get out my large Stilsons?

Well that’s exactly what I had to do to remove and fix (parallax and reticule alignment) the polar scope in my then-new AZ-EQ6 a year or so ago. Took a lot of courage, but it worked. Everything had been cemented together.

M

[JamesF]

I don't think I needed to do anything particularly brutal to remove the polar scope on my EQ3-2, but that might depend on whether it is factory-fitted or after-market.

James