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Hotech laser collimator

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#1 scott50

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Posted 28 June 2013 - 01:09 PM

I have a 2" Hotech laser collimator, a 2" Catseye Cheshire and a 2" sight tube. My usual procedure for collimation is to make sure the secondary looks round in the sight tube, then use the Hotech to further align the secondary and rough-tune the primary, then fine-tune the primary with the Cheshire. The Hotech has an expanding barrel to center it in the focuser. However, when I use eyepieces, I use the adjustment screw. Won't this cause a difference in collimation? I notice a shift in the laser when I switch from the expanding barrel to the focuser screw. Should I either use the focuser screw when using the Hotech, or not use the focuser screw to hold in my eyepieces? (Yes, I know star testing is cheap and fool-proof, but sometimes I want to collimate in the daylight). Any advice?

#2 desertlens

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Posted 28 June 2013 - 01:27 PM

I use the locking screw and the expansion system together. The result has been good collimation of both primary and secondary mirrors. I found the rubber expansion rings to be a bit "squishy" but helpful for centering.

#3 scott50

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Posted 30 June 2013 - 01:43 PM

Thanks for the tip. I'll try it.

#4 Mike B

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Posted 30 June 2013 - 02:24 PM

I really hate to say it, but i've grown suspicious of the Hotech's feasibility... i've used their 2" laser for quite some time, but a CN thread a while back challenged my thinking- and so i challenged the Hotech, trying a few tricks with it, like rotating it *while snugg'd* in the focuser; was quite discouraged to see the beam waver all over the place on my primary! I tweaked the Hotech laser's collimation a bit, which seemed to help... a little... but overall i remain unimpressed.

It seemed like such a great idea. I hope you have better luck with your unit. And *yes*, the tilt imposed by set-screws is a non-contender... a collimation tool designed with seriously tight tolerances seems the ONLY real solution here.

I dunno... a Howie Glatter unit may be in my (near?) future...
:shrug:

#5 Jarrod

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Posted 01 July 2013 - 08:57 AM

Collimation refers to aligning the mirrors and focuser tube to one another. It's therefore important that the collimating tools are centered and parallel to the focuser tube. But once the scope is correctly collimated, it's not as important for the eye piece to be perfectly centered to enjoy the benefit. Parallel is probably quite important, however.

I spent a good chunk of my weekend with the Hotech, trying every technique I could think of to find which one creates the most reproducible results. What I found is that the self-centering mechanism does not behave well with compression-ring style visual backs becuase there is very little perfectly flat and non-pliable surface area for the rubber centering rings to press against. If I instead put on a visual back that has set screws (and therefore a smooth inside for the rubber rings to grab), I get much more repeatable results (leaving the setscrews backed out - not tightened against the laser). within a couple mm in terms of where the laser hits the primary on each insertion. This appears to be enough to give a consistent readout with the barlowed laser center-spot shadow which seems to be the gold standard for primary alignment.

Also, results are not as repeatable if you are only snugging the laser to the point where it can still rotate in the focuser. When I get it tight enough that it won't budge, the results are better in terms of repeatability and I therefore assume accuracy.

Those are my notes on how to make best use of the Hotech. However, I agree with MikeB that the proper solution is a collimator built to extremely high tolerance that simply goes into the focuser one way and one way only. In that ideal case there would be no need for "proper technique" and therefore no room for user error.

#6 JayinUT

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Posted 02 July 2013 - 11:25 AM

I have 1.5 inch Hotech that I had listed for sale. No takers. Now I'll probably give it away to someone locally who wants it. I did get the Howie Glatter system, all of it and I have the Cats Eye System and it depends when I am setting up to which one I use. Both are outstanding and I am glad I have both.

#7 howard929

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Posted 02 July 2013 - 12:27 PM

Collimation refers to aligning the mirrors and focuser tube to one another. It's therefore important that the collimating tools are centered and parallel to the focuser tube. But once the scope is correctly collimated, it's not as important for the eye piece to be perfectly centered to enjoy the benefit. Parallel is probably quite important, however.

I spent a good chunk of my weekend with the Hotech, trying every technique I could think of to find which one creates the most reproducible results. What I found is that the self-centering mechanism does not behave well with compression-ring style visual backs becuase there is very little perfectly flat and non-pliable surface area for the rubber centering rings to press against. If I instead put on a visual back that has set screws (and therefore a smooth inside for the rubber rings to grab), I get much more repeatable results (leaving the setscrews backed out - not tightened against the laser). within a couple mm in terms of where the laser hits the primary on each insertion. This appears to be enough to give a consistent readout with the barlowed laser center-spot shadow which seems to be the gold standard for primary alignment.

Also, results are not as repeatable if you are only snugging the laser to the point where it can still rotate in the focuser. When I get it tight enough that it won't budge, the results are better in terms of repeatability and I therefore assume accuracy.

Those are my notes on how to make best use of the Hotech. However, I agree with MikeB that the proper solution is a collimator built to extremely high tolerance that simply goes into the focuser one way and one way only. In that ideal case there would be no need for "proper technique" and therefore no room for user error.


Some quick thoughts.

Using a sloppy fitting laser for secondary tilt adjustments is a hair pulling procedure at best. I do it but don't recommend it.

Barlowing such a laser is well know to negate that effect for the all important primary mirror tilt adjustments.

Glatter laser and blug/tublug seems to be the best available for all of the right reasons.

#8 csrlice12

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Posted 02 July 2013 - 12:50 PM

When considering Laser collimation systems, just ask yourself: "What bad things have I seen/heard about Glatter Laser systems?"

You won't find any....outside of price.....but you get what you pay for......Glatter system--buy once, you'll never need another.

#9 Jason D

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Posted 02 July 2013 - 08:05 PM

I have 1.5 inch Hotech that I had listed for sale. No takers.

Hi Jay, maybe because it would be hard to fit a 1.5 inch laser in a 1.25 inch adapter -- just a thought. ;)
Jason

#10 HOTECH

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Posted 03 July 2013 - 08:52 PM

Hello Mike,
The unit might need a new set of O-ring. Please send the unit back and I can take a quick look for the issue you mentioned. We have lifetime o-ring replacement service. And we have video illustrating how to load the collimator in the focuser for proper registration. Please email us on how to go about the check up. Thank you.
Clear Skies!
David

#11 Mike B

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Posted 04 July 2013 - 01:17 AM

Thanks David, i might consider that... but the unit is essentially brand new. But as i've thot more about the matter, one issue might be that my JMI focuser drawtube is "chased"- in other words, fine groves cut into the walls; this may provide a not-uniform-enough surface for the o-rings to seat against in a "repeatable" manner.

Also, results are not as repeatable if you are only snugging the laser to the point where it can still rotate in the focuser. When I get it tight enough that it won't budge, the results are better in terms of repeatability and I therefore assume accuracy.

I was snugging awfully tight! Again, it may be the grooved tube walls at work in my non-repeatable results?

My latest solution is using an older 2" barrel "Kendrick" laser, and shimming it slightly at equal points around its barrel- so that it sits snug, no wobble. This has given me the best, uniform results.

If a smooth drawtube is all that the Hotech requires, then its "o-ring" gripping design may actually be as good as it sounds!

#12 Jarrod

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Posted 04 July 2013 - 01:49 AM

I was snugging awfully tight! Again, it may be the grooved tube walls at work in my non-repeatable results?


It's possible, based on what I saw with the compression ring adapter. That also may be why you snugged the ring tight but could still rotate the laser in the tube - less surface area for the rubber to grab.

If a smooth drawtube is all that the Hotech requires, then its "o-ring" gripping design may actually be as good as it sounds!


It's not a bad design, but it is not the foolproof design that the Glatter system appears to be by all accounts. However, you don't need to spend $300 on a Glatter system to get an accurate collimation. After a bumpy start, I'm now happy with the results I'm getting with the Hotech.

#13 Mike B

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Posted 04 July 2013 - 01:40 PM

However, you don't need to spend $300 on a Glatter system to get an accurate collimation.

Perhaps not, but since i already have, use, and enjoy tremendously his "TuBlug", the next logical step (his *laser*) is only half of that $300. ;)

Yet like you, i'm finding (what, for now, seems to be) acceptable results with work-arounds, so have not (*YET*) sprung for any more collimation goodies.

It is nice to have some options... as in *beyond* the standard & near-useless lasers that had been the rule a few years ago.
:grin:






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