Polarscope collimation

[Rock Doctor]

After much swearing, frustration and trying to do too much over adjustment with the grub screws on the polarscope last night I returned to it this morning in a better frame of mind and bingo everything just fell into place.  I realised that I had to do far more with the dec and az adjustments so that there was only a little fine adjustment to do with the collimation grub screws.   It was surprising just how far out it was in its as purchased state to my mount.  . Pointed it at a neighbours end ridge tile and the central crosshair stays in the same position as the RA is rotated and when I move the reticule so that the Polaris target was in the same position it tracked exactly around the circle. Hopefully that's it sorted.

[philjay]

Great stuff Dave, they are a bit fiddley the 1st time but once done, barring major trauma to the mount, you wont need to do it again

[Rock Doctor]

They are very fiddly. Half a turn too much on the grub screws and they disappear. You then have to take the polarscope apart to retrieve the screw. I can see why some people mod the grub screws with thumb screws.. It also saves fiddling with a very fine Allen key in the dark if you want to check the collimation on Polaris. 

[Brantuk]

Oh... I've done that before too - one turn too far and it falls into the gubbins - not only did I have to take it to bits to retrieve, I had to reassemble it correctly too. I wouldn't even attempt that in the dark.

 

Glad you're sorted now - but yes they certainly could pay more attention to setting them correctly before selling - we pay enough for the blinking stuff lol

[Rock Doctor]

Kim,

 

I'm still shocked that I had to buy a polar scope as one isn't included with the mount.

 

Another thing that I came across yesterday was after following the alignment process for a NEQ6 mount. During the mount levelling process there are a couple of occasions when you rotate the mount to check it's level and make reference to a couple of graduated collars for Dec and RA. The same collars on my mount are just plain and there are just a couple of marks to indicate the home position. I still managed to check these and found that the dec home position marks were slightly out.

 

Also spent some time on the tripod and moved the North peg so that a single leg now points to North and marked up where the legs go on the paving which should help to speed up setting up.

[Brantuk]

Your setting circles (collars) should be graduated on that mount - they ought to be as usable as the NEQ6 circles. I think I'd complain about that cos if the gps/goto goes pear shaped then you have no way of finding stuff other than manually. But the home position should be accurate - I'd have to look at it to comment on that one.

 

Make sure that moving the North peg doesn't over balance any part of the rig - I only mention it cos I notice you don't extend the legs to get a wider footprint. I guess it's obvious but I'll say it just to be safe: check the center of gravity is actually central when the scope is in all orientations or you risk the scope falling over (like what happened to me lol).

[philjay]

My cge has no circles let alone graduated ones. Yep this means you are on your own if things go pear shaped im afraid. Its goto or nowt on these mounts im afraid, but looking on the brightside, ive had mine 8 years and never had any probs

[Rock Doctor]

Thanks Phil, and Kim you got me a little worried about changing the Az peg to over a leg so I Googled. All of the pictures show the mount in the default position with the counter weight bar between two legs but I found a thread on Cloudynights which starts off by lowering the mount for extra stability by lengthening the spreader bars which allows the legs to splay wider. Someone else then goes onto say that the first thing that they did with the mount was put the peg over a leg for greater stability, the reason that Celestron defaults to between two legs is that at lower latitudes the counterweight bar will foul on the leg. At our latitude it wont be a problem.

[Brantuk]

Ahhh that's good news Dave - I was worried for you and your scope - so it was good to be cautious and get the full story.

 

(There's always someone who's been there, seen it, and got the T-shirt lol).

[Rock Doctor]

I must admit you had me in a panic and I was thinking that I would have to go and put the peg back in it's original position, especially when I googled and selected images and they all showed the mount with the counter-weight bar between legs.   The chap that said that he'd moved the peg said that he was actually concerned about the stability of the mount with a 22lb counter-weight with the bar between the legs so moved the peg and says the mount is a lot more stable.

[Brantuk]

Excellent

[dawson]

I replaced my grub screws with ones i could turn by hand. Makes aligning the polar scope easier....

However, it transpires lugging my mount head around in a suitcase has resulted in the hand turned knobs coming lose, and then i wonder why my polar alignment was shocking....

So, after re-aligning the polar scope, i though "i'll do these screws up nice and tight so they don't rub lose again" and got out the screw driver and tightened each an eighth of a turn until it was nice and snug.... Looked through the polar scope ro check it was bang on and it was (pretty much) but they was a bulls eye fracture of the reticle glass over Cassiopeia. Luckily it doesn't impact on the rest of the view [yet] but it's a lesson for everyone else, read the instruction and don't tighten the reticle screws too tight!

James

[Brantuk]

Another one bites the dust lol. Yup - just tight enough to hold the reticule in place without applying any pressure to it does the trick. Similar thing with collimation and locking bolts on mirrors and lenses - just snicked up enough to support the optics "in place" is more than enough.

[dawson]

If's not bitten the dust just yet; but i've emailed FLO to find out how much a replacement is as i'm worried the crack may spread.

James