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Collimators
¿ªÔÆÌåÓýHi Group, ? I am looking for a collimator? for my C14edge . Who tested the HOTECH? SCT advanced collimator and/or the BAADER C1335? recommended by Celestron. Which is the best or the easiest of use ?? ? Regards. ? Andr¨¦ Schwachheim. |
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Andre, I bought the HOTECH collimator last year for my C-14, mounted on a pier in my obs.? I have not been able to get the screen back far enough-because of the height of the walls- to do a good job.? I was able to get a rough collimation, but haven't used it since.? I believe it to be an extremely accurate system, but takes some time to set up.? It is for sale-contact me off line if interested.? It is like new, stored in original fitted case. budh.
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SCTs are?easy to?collimate?because there is only one accessible adjustment - secondary tilt-tip.? Collimation aids are entirely unnecessary and of dubious value compared to star collimation.?Star collimation is very sensitive and precise, though it may take some time to develop an eye for assessing the?concentric placement of?diffraction rings (start with centering the shadow).? A potential problem with most collimation aids (incl artificial stars) is that they require?collimating in horizontal position. That?can easily result in miss-collimation?when sky pointing, due to?flexure (esp of the primary). This is more likely in larger scopes but can occur for any scope. Save your money for a sexier gadget. Stan |
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I agree, the HoTech, while clever, its too complicated and requires VERY precise alignment with the scope to give good results. Even he admits that a final star collimation should be done for accurate collimation... meaning you should just do that anyway as that is all that really matters and gross centering of the secondary is dead easy. And free.
Star collimation is not that difficult and doesn't need to be done very often, maybe once a year, to justify spending $500 on one of these gadgets. |
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I have the HOTECH advanced collimator for my HD1400 and it really works for my case. Star collimation worked when I had some one supporting the work since I wasn't able to reach the alignment screws of the secondary mirror while looking at a target start with my eye because of the size of the scope.? Star collimation was not that difficult, but not that easy either. I saw the diffraction ring and my friend rotated the screws with my instruction. Communication was critical and only a fraction of turn of the screw dramatically changed the shape of airy pattern so it was very very frustrating for both of us. The alignment work took 20-30 minutes until we got satisfied with the pattern and I always felt guilty getting their precious time. So I bought the kit four months ago and used twice. Here is what I experienced; Pros: - First and foremost, it gives an accurate collimation. Right after the collimation I made a trip and ? observed a star whose diffraction ring around the airy disk was perfectly complete and uniform. - The collimation can be done daytime, so you can save time for observation - There is no risk to touch the corrector plate with your fingers by accident, compared with? ? start collimation at night - You could collimate the scope even the it is in sky positioning, if your tripod allows you to do so. Cons: The collimation kit requires we set and perfectly co-align the collimator plate and the scope, so you may need an elevator tripod with a head that enables precise gear movement in three directions(such as Manfrotto 410). The head is contained in the kit (called Fine Adjustment Stage) but is cheap and lack of stability. As advised in the previous reply, I now like the idea of Live view function of DSLR (especially one with flip LCD such as Nikon D5200). Yasushi Fukunaga |