Howie Glatter collimator - need to borrow

[pmrid]

Like a dill, I sold my Glatter collimator last year along with the holographic lenses it uses AND my Takahashi collimating scope. Thought I would not have any further use for either. HA!!

Well you can guess it I'm sure, I now need one because my RC8's collimation is all to hell.

I can use a basic laser collimator to line up the focuser with the secondary center-spot. But beyond that point, the basic (non-hologram) gear doesn't cut it.

Dos anyone either have a suggestion for using a plain-Jane laser to properly collimate a GSO RC8, or have a Glatter I can borrow for a week or so?

Peter

[RickS]

Hi Peter,

I have a Tak collimating scope and a Glatter. The Glatter is on loan to Camelopardalis to tame his wayward newt but I can probably find a way to help you out if there are no better options.

Drop me an email or send me a PM if you want to discuss.

Cheers,
Rick.

[DJT]

Hi Peter
Do you have a bog standard Cheshire? Are you using tilt plate?

[pmrid]

G'day David.
Yes, and yes.
The tilt plate is great for getting the focuser exactly aligned with the center-spot on the secondary but no use for getting the primary mirror aligned with the secondary. And that's where I'm stuck. When I had a holographic Glatter, I made a screen with a series of concentric circles on it that I slipped over the tube that comes up through the primary. By using the hologram, it was easier for me to see the projected holographic circles and to get them aligned with the primary. Without that, I found it pretty hard to actually see the hologram clearly enough to do that step. But alas, my Glatter is now decorating someone else's cupboard of unused treasures.

And as far as I can see, a plain Cheshire wouldn't be much help either. Perhaps I'm missing something though. I'd be the first to admit what I don't know but it's such a long list, ...

Peter

[pmrid]

Thanks Rick. I'll do that.
Peter

[DJT]

Hi Peter
I tripped over this process the other week and it’s worked for me.
1) physically align your focuser using a collimated laser so it hits the secondary dot. Tick
2) with the collimator, adjust the secondary until the dot is central, alternatively using a laser collimator adjust the secondary so that the beam returns and hits the little hole in the laser collimator.
3) remove all the devices and then step back from the telescope. Peer through the focuser from a meter away to check that the vanes are aligned. This is where you adjust the primary mirror. See piccie. It’s tiny adjustments. You may want to unscrew and remove the baffle so you can see the vanes clearly.
4) you may need to repeat the process again then do a star test.

I used a Baader click adapter to make sure the laser collimator is held consistently in the focuser when I tried this.

Alternatively, wait for rick!

[pmrid]

Thanks again David,

I'll try that. It sounds simple enough to work - and heaven knows, I do love a simple explanation.

I don't suppose it makes much difference what sequence you do steps 2 and 3 in. I was fixated a bit on getting the primary aligned before adjusting the secondary. But if pushed, I cannot say why.

Peter

[DJT]

Actually it does. You need to nail the mechanical alignment first before anything else. What I did was to reset the tilt adapter, ie back of the 2 small hexes and snug up the box hexes till there was nowhere to go. That’s your start point, then adjust back till the focuser is aligned.

Then do step 2 and 3 then iterate as needed.
Without that 1st alignment you are pretty much flapping around.

Really was surprisingly simple in the end

[pmrid]

G'day David and Rick.

Well, I seem to have reached that point of diminishing returns with collimating this RC8. I daresay I could make it a bit better but I'm sure you will understand when I say I am heartily sick of fiddling 'round with it.

As you would expect, there's always another hurdle o overcome after the last and now it's tracking. I'm getting y-axis peak-to-peak of between 1.5 and 2 pixels and consequently decidedly elongated stars.

So now, I go back to tweaking the worms and muttering incantations over the entrails of the mount itself. I did a Rowan belt mod on this NEQ6 last year and although it's a quiet as church, it does not seem to me to be a smooth in RA as it should be.

So now, we set off in search of yet another elusive goal - a well-tuned and well-balanced mount. Ain't it a hoot!!

Peter