Farpoint Astro 2" Autocollimator

[Dragan]

Just thought I'd help get this forum started.

Recently I received my 2" Autocollimator from Farpoint Astronmical Research link Though I haven't had a chance to use it yet, I thought I'd pass along some of its build qualities.

First off, in 20+ years of observing with reflectors I've never owned a "real" AC. Its always been a plastic cap with "something shiny" on the inside that had a hole through it. This has now changed.

This is one serious AC. This thing is a real work of art. Its made of anodized aluminum with, get this, a real mirror flat. Real glass. NOT "something shiny" It also comes with a rubber cap to help protect the mirror.

I've only had it for a couple of days now and have not had a chance to test it out. But I can't wait till I do!

For more information contact James at the link above. Tell him I sent you!

Here are some pics....

AC1 (Large).JPGAC2 (Large).jpgAC3 (Large).jpg

[Marko]

First of all thank you and Jimi's for your efforts in setting up this forum.

I would be curious as to your thoughts on use of this (or any good) autocollimator as I generally setup using the catseye 2" 'BlackCat XL' cheshire which I very much like on the starmaster as the triangle pattern just touches the edges of the cat's eye. Only at times do I tend to take the extra effort to use the 2" autocollimator from catseye because it is very touchy. It is of same quality as what you describe from Farpoint I suspect. When I say 'touchy' I mean to say any sort of pushing on the focuser with it in place or rotation of the tool as you are viewing has an effect on the ghost images. My scope is a starmaster 18" f/3.7 with feathertouch and is fairly stable instrument.

At one point Steve Gottlieb (thanks for pointing me to this forum Steve) and myself attempted to assess in the field the ease of use of the autocollimator vs what you gain in the view once the eyepiece is inplace. I feel the StarMaster is secure in it's focuser attachment to the secondary cage and yet the autocollimator due to it's sensitivity in the multiple reflections and path length show such very small alignment issues. Perhaps with an autocollimator getting 'close' is all one can ask for and that is the improvement to look for over the simple cheshire alignment.

What I wonder about is it being so 'touchy' when it is used VS how that translates to when my paracorr and 7mm Nagler is in the scope. I wonder if I would be better off with a 1.25" autocollimator used with everything inplace except the 7mm Nagler (don't have any ethos so I stick to the nagler set generally at 1.25"). At that time of above evaluation none of us had an Ethos but with the Ethos being so heavy and long I question the effect of the moment from that weight on the focuser of paracorr/ethos and how that impacts the very carefully done autocollimator process (I suspect it voids it to some extent).

Thanks for any thoughts

[Dragan]

Hi Mark,

I've never had a decent autocollimator. To be honest, I'm not quite sure what to expect with this one. I've owned and used the plastic cap kind which in itself had a tendency to exhibit alignment issues and I've never put much credence into it. (side note, it was Jimi who taught me how to use an AC over 8 years ago! I had never used one before that) I've typically always collimated with a laser and just started using a Flug about 3 or 4 years ago. Using this combo I've never had any problems and I've always exhibited a perfect star test upon completing collimation.

Two years ago I had my Kendrick laser re-collimated by Kendrick. Knowing it was perfect, I then painstaking took the time to ensure that my focuser was square, optically and mechanically. I also made sure my secondary was as centered as possible. (I have no offset). Will I find an issue with the new AC? Only time will tell. I don't think I'm going to have a weight problem as my laser with the Flug is heavier than the AC alone and the focuser board/FT focuser on my scope are robust enough.

As soon as I have the opportunity to set up my scope and do a test I'll let you know. I'm interested to see what I find.

[Don Pensack]

Anyone on the Forum who would like my "How To" article on collimation, including the use of an autocollimator, please feel free to download the article from:
http://www.cloudynights.com/item.php?item_id=2677
The autocollimator is an amazing tool and allows collimation precision to be elevated to new heights.
Picture "Collimated" as having the collimation of the scope somewhere in a circular zone. Anywhere in that zone is "collimated".
But mechanical sags and flexures can take a scope out of the zone in use.
The AC allows you to get near the center of that "zone of collimation" so that mechanical flexures (unless severe) will not take you away from the "collimated" state.
It is especially important in short focal ratio scopes, where tolerances get a lot tighter, and in scopes where coma correctors are used.
Don Pensack
Los Angeles

[rmollise]

Hope you enjoy it. Me? After trying everything over the years from 35mm film cans with holes in the bottom to lasers, I've landed on today's ubiquitous combination Cheshire-sight tube. I find it can easily produce a collimation good enough for anything I want to do. Complaints? Due to the nature of the beast, the crosshairs are naturally "out of focus," but still...great collimation in a minute or two with a tool that costs 50 bucks? I like.

[kemer]

I can't find the product information for this on their site. They still have the 2" cheshire, which seems to be the same principle, except rather than mirror flat, there is a ring of reflective tape; it's an attractive hunk of nicely machined aluminum with a bright red anodized surface. I have found this to work very well to collimate my secondary position. I still use a laser to complete and fine tune the collimation. The combination works like a charm, but I'm wondering what makes this "auto".
cheshire2inch.jpg

Kemer Thomson
18" f/4.2 Obsession UC

[Don Pensack]

The cheshire is used to do primary mirror alignment to the optical axis. The autocollimator has a first surface mirror on the inside and shows multiple reflections of the primary centermark. It reveals residual errors in both primary and secondary alignments that can dial in the alignment to a greater degree than is possible with a sight tube and cheshire. If you use a Paracorr coma correcto, the elimination of the residual errors improves the performance of the Paracorr by bringing the center of the optical path to the center of the coma correcting lens, essential for best correction.
You can see how the tools work and what they do by clicking on my link in my prior message in this thread.

[FaintFuzzies]

I know the gents at Fairpoint and am impressed with their shop. I'm going there soon to check out their auto collimator and will let you guy know what I think.