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Hotech SCA Laser Collimator
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Hotech SCA Laser Collimator
I needed a good, solid, laser collimator. I chose the HoTech SCA, and have been happy with my choice.
I use four Newts rather regularly: an F4.5 10 incher, a F5 12.5 and F5 22, and F6 8. The ten and the eight are solid tube, and the 12.5 and 22 are truss with shroud. I have been observing seriously for about 15 years, mostly in southern California. I have used a variety of collimators through the years, and was fairly satisfied with my Orion Lasermate Deluxe until it turned flaky about a year ago. I spent that year borrowing collimators of various brands from my buddies, and making a wish list for what my ideal collimator might have.
I wanted one-person collimation: a window where I could see the return beam coming back up while I was adjusting collimation screws at the rear of the tubeâ€”even on solid tube scopes.
I wanted something solid that would last for a while.
I wanted a collimator for my 1.25 focuser as well as my 2 inch.
I wanted a tool that fit easily in my eyepiece case.
I wanted something that would not cost more than it should.
I wanted consistent results: I was always a bit bothered that I could insert my collimator in the drawtube, get everything lined up, remove the collimator, reinsert it, and my "collimation" would be off. Obviously, since my secondary or primary had not shifted, my collimator had. I was getting different readings depending on how and where I inserted the collimator or how the setscrew moved it. Not all the time, but disturbingly often enough.
In the year since my Orion Lasermate started to abandon me (faulty on-off switch on the laser, for those who want to know), I had the opportunity to borrow probably half a dozen laser collimators of different brands, quality, and capabilities. (And I've looked at a few others at RTMC Astronomy Expo and PATS). Most of them worked fine, but none were perfect. One was made of Delrin with the kind of laser pointer you can get at the dime store (What's a dime store?). Some of them were pretty fancy, with projected holographic patterns that help center the mirrors, or attachments that go on the far end of the drawtube to help locate the return beam. Some were obviously finely machined aluminum. But I would have had to pay a lot for those. And, frankly, I did not need the fancy things too much. My scopes are in the ballpark whenever I first set them out for the evening, and the laser collimator is mostly just to tweak them towards the peak. Those times when I really need to collimate from scratch, I still use a sight tube as well as a laser collimator and sometimes a barlow-collimator.
At PATS this last September, I finally pulled the trigger, and got myself the HoTech. I had talked to David Ho several times, and knew he stood behind his products. But more importantly, this collimator met my wish list best of all those I saw at the show (and had borrowed for the past year). I suppose for full disclosure purposes I should point out that I like to hang around big functions like the Winter Star Party, RTMC, PATS, and such, and have hob-nobbed with Howie Glatter (now-- there are some stories!!!) and David Ho, various telescope store salespeople, and others who make or market laser collimators. I believe, though, that I can keep my evaluation of the products separate from the relationships I may have with the people!
The HoTech had the 45 degree angled side-view mirror. When the return beam is coming back up, it reflects off the "white-with-gridlines surface"-easily visible from the back of the scope where I am kneeling down twisting collimation screws. I fell in love with these rear-view windows when I first saw them on my old Orion collimator. They made it possible for one person to collimate a newt from the back. HoTech improved on the concept by making the white background surface, and grid markings. In all fairness, other collimators have adopted the whitish background with grid and the rear-view window since I first bought my early edition Orion.
As for build quality, my impression is generally favorable. It is not as heavily built as some. But do I really get better collimation out of a tool milled from a single billet of aluminum than I get with this? When I first took it out of the box, I did have a problem with the on-off "switch" (Rotate the battery cap down, and it turns on; loosen the cap, it turns off. Not my favorite arrangement, but it does work.). HoTech immediately replaced the original collimator, no questions asked, and I have had no problem since.
I tested the collimator to see if it were itself collimated (Did the beam head straight out, or was it skewed?). One easily-run test for most laser collimators is to rotate them in the drawtube. If the laser dot stays put, things are fine. But if the beam describes an arc it means the laser itself is not collimated (assuming a fairly good fit in the drawtube-otherwise you may just be chasing slop). However, one cannot run this test with an SCA laser collimator because the tool will not rotate easily in the drawtube. Instead one must rotate the collimator carefully in a v-block while watching the beam against a far wall. I did this, and the HoTech dot stayed put, just like it should.
One of the problems with judging durability of a new product is that the reviewer has few samples to judge. So, before I wrote this, I called a few people who sell these things, and was told that they have seen no real problems or returns with the HoTech collimators. (And, since they knew I already owned one, and that I would be very unhappy if they did not tell me the truth (!!!), I knew they were not just "funning" me to get a sale.)
As for versatility-1.25 and 2 inch compatibility-I knew I could always just stick an eyepiece adapter on the smaller version to get it to fit the larger drawtube. But, I did not want to introduce more slop, and that is what can happen with an adapter. The HoTech system beats this problem with its SCA mechanism-more later.
I am impressed with the way this relatively compact collimator fits nicely in the eyepiece case. (Down side: I don't get to use the really nice box this thing comes in.) It is not a disaster, really, to have a big collimator. But smaller and lighter is nicer in general.
As for cost, the 1.25 version of the collimator is listed for $89. This compares to about $65 for the least expensive of the laser collimators to about $115 for the more expensive. The adapter to 2 inch brings it to $120-lower than most competition's two inchers. So, you are getting a collimator that is priced about right.
But-and this is what makes it special-the HoTech is self-centering. The Self-Centering Adapter ("SCA" in the title) is basically two rings of foam/rubber (three in the two inch adapter) just large enough to fit around the collimator tube, and just (barely) small enough to fit in the drawtube. After insertion, one twists a ring, which compresses the rubber on one of the rings, and forces it outward all around-thereby centering the collimator. More than just centered, though, the collimator is now attached, as it were, to the drawtube. It is as if it is all one piece. It is as tight as a setscrew can make it-but the setscrew tightens in only one axis of the tube while the rubber rings tighten evenly all the way around. The result is a laser collimator that seats very firmly in the center of the drawtube. And if you are using the 1.25 version in the 2 inch adapter, it is practically as solid as a one piece two inch collimator. Earlier I mentioned getting different results every time I insert the collimator in the drawtube, even when I have not moved the primary or secondary. This does not happen with the SCA. I get the same results every time because the collimator is in the same place every time. It does not move around depending on where and how you adjust the setscrew. This mechanism does make it harder to slip the collimator in and out of the drawtube (it is a tighter fit, even when in the loose position), and it does take a few seconds longer to loosen the ring and insert or remove the collimator than with a traditional setscrew. But these are small prices to pay for the solidity of the collimator, and repeatability of the procedures.
For those who demand Barlow collimation, of course, the HoTech tool can be used with a Barlow. But if you are using a Barlow-laser technique to compensate for a laser that is not centered in the drawtube, or slopping around because of differing manufacturing tolerances, then you may be able to skip it. The self-centering obviates the need for a Barlow in many situations.
This collimator is not magic. A return beam, even properly hitting the return point, cannot tell if the secondary is properly centered under the drawtube. If the drawtube or focuser itself rocks back and forth, then the collimation results will be inconsistent. If the focuser is not perpendicular to the tube, and properly aligned, then any laser collimator will have problems. If the center spot on the primary is not in the center, collimation will fail. In short, this collimator cannot fix problems it is not designed to fix.
Does this Self-Centering-Adapter give me the best collimation possible? Sure does for me. That is not meant to be flip. The best collimation I ever get is with a high magnification star test, and I have not done that since I don't know when. It just does not improve my experience at the eyepiece. (I do check my laser assisted collimation at "viewing power," and I do not notice any need to do further collimation by star tests. Perhaps I'd find something wrong at higher power!?! Perhaps I would be a little more careful were I using my newt tubes in astroimaging.) Precise collimation depends on so many variables: weight and balance shifts, temperature shifting strut and tube lengths, the dynamics of a moving tube/spider/mirror cell, variations in tube elevation, position of eyepiece in the drawtube, tightness of the setscrew."¦ The list goes on and one can worry only so much in life. I think we all know people who collimate their scope depending on what altitude they expect to be viewing, and recollimate during the night as the temperatures shift. I don't.
In short-I like my HoTech SCA laser collimator. I did not pay much, if anything, more than I would have to pay for most other good quality lasers, and I paid a lot less than I could have for some of them. And for that I get solidity and repeatability, and good, quick collimation.
The HoTech SCA 1.25 laser collimator (bottom) fits tightly into the 2 inch adapter (top). This combo makes a solid unit that can be used for either 1.25 or 2 inch drawtubes. Note the soft rubber rings and the knurled ring. These constitute the SCA mechanism. (See text for explanation.) Even without this mechanism, the HoTech collimator is a good competitor, but the SCA addition really adds stability!
The HoTech SCA 1.25 showing improper collimation of the primary on my home-made F6 8 incher. Note the red dot is seen against the grid of the rear-view cutout window (rather than disappearing into the center hole-which would indicate good collimation). This was taken in bright sunlight, and the return dot was easily visible (and redder than in this picture) while I worked the collimation screws from the rear of the tube.
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