Televue Paracorr

I picked up a Televue Paracorr Visual when in the USA, bought at the fine store of OPT in Oceanside.
However, I only got my first chance to use it..albeit a brief one...on Sunday night.
I've a F4.6 16" Lightbridge, and I'd noticed that with normal collimating I'd some coma with my Panoptic 35mm eyepiece...no surprise, but it was much less than I'd expected.
So, I married the eyepiece to the paracorr, and the combined weight wasn't pleasant...over 3 pounds.
However, slapping a velcroed 1 kg lead shot bag onto the rear of the dob balanced it out better.
So....my brief test involved using the star fields around Auriga which were well up, and not far from the zenith.
I found that the Paracorr did indeed make a noticeable difference, but as always there's a trade off, in that the extra optics had marginally reduced the available light, but then again there's supposed to be a 1.5 magnification factor also involved.
However, stars remained pretty true to the edges of the FOV, which does the job for me.
I'll need to spend a lot of time on a full evaluation with both the 27 mm and 35mm Panoptics, but it's looking good so far.

Thats a very interesting report.
Was the image noticeably dimmer with it then the view without it??, I thought the magnification factor was 1.15, is it adjustable ?

You're right Dave...it is only a 15% increase in mag.
I didn't notice any real difference as my subject matter consisted only of starfields, and so the magnification wasn't something I was looking at.
To me there was a discernible difference, but again, whether that was due to the difference the Paracorr was actually making to the star field or just a slight loss of light and contrast was hard to judge.
This is one that I'll be having a good time judging...if we get any decent skies, that is, and I'll post up a fuller report when that happens.
In addition, when in california I was introduced to David Ho, who has started making laser equipment for Astronomy, as he also works for the US Military applications, I think.
I've bought one of his 1.25/2" laser collimators....an interesting bit of kit that with its own compression ring system that effectively makes it rock solid in its 2" form compared to any others I've used.
In addition, he's got a 3 in one light, with a white light LED , a 3 step graduated red light LED system, and a very bright green laser integrated....and all shaped as a light sabre handle!
I got the laser collimator for $120, and the light/laser for $100.
I'll be putting photos up.

I've read about the Hotech Laser Collimator.

The consensus seems to that while this self centering makes secondary collimation very accurate and may even overcome the repeatability problem in terms of laser positioning in the focuser for Primary collimation, it still loses out to barlowed laser collimation when it comes to focuser flex and may still not be as accurate even if flex was not an issue.

Then there is the fact that unless your eyepieces also have a self centering mechanism the hotech is collimating the scope to its own centred position in the focuser. Not the actual postion that your eyepieces may be in when inserted. Though this will only mean a bit less than perfect illumination. ie the light cone will not be perfectly centered for your eyepiece.

Another issue to note is that if you are using your paracorr you should collimate the scope with this inserted but a paracorr also makes the margin of error in collimation much tighter, so much so that you need the accuracy of the barlow method even more. And if one needs to use the barlow method anyway then the focusser position repeatability ability of the hotechs self centering mechanism is a bit moot anyway.

So the question is, can one use the barlow method with a hotech?

The Hotech uses a series of rubber rings which compress themselves in the focuser, and I've found that I don't need to use the screws to hold it in place...it's an extremely tight fit, so this acts as a form of self-centring mechanism for it.
It can be used as a Barlowed laser too, not forgetting that this will only deal with the primary and not the secondary mirror, and it's claimed that it will be even more accurate than most collimators in this mode.
I've been using it for a while now, and I'm very impressed. It is rock solid in the focuser and looks cool too.
Image at [ www.hotechusa.com/images/collimator-combination-w600.jpg
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