HoTech - an interesting development, laser based collimation.

[Dennis]

It looks like there are three parallel lasers on the source/target disc from where their beams enter the optical tube. The laser beams return to the source/target disc, placed quite close to the OTA and by noting the position of the returned beams, you can make comfortable adjustments to the 2dary holder to collimate your ‘scope.

No price yet, it seems 1st production units will be available at the end of April 2010.

Get one H0ughy, you know you need one! ;):)

http://www.hotechusa.com/searchresults.asp?cat=23

Cheers

Dennis

[dcalleja]

I wonder how much it will be

[Starkler]

It would appear that accuracy depends on the three parallel laser beams being precisely that.

Is it possible for them to shift in relation to each other? Do you need to collimate the collimator? The sales blurb doesn't tell you.

[h0ughy]

looks too high tech for me Dennis, though i already have the 2" hotech collimator - its pretty good

[Omaroo]

Very interesting Dennis :) Would it work on the Mewlon?

[multiweb]

This is very clever indeed. I used a similar thinking in physically aligning the optics of my C11 but I had to remove the secondary for it to work. The card had to be set at the primary focal plane and you had to shine a torch through a pin hole to match the laser dot. This is really nicely integrated though. I'll definitely get one. Finaly a system where you can accurately quantify an offset and take the guessing out of the equation. Dennis, you're going to send me broke. :lol: Thanks heaps for posting though. :thumbsup: You're forgiven.

[OneOfOne]

I had a look at their site when it was first announced in Sky & Tel (US version) a few months ago. It looks like an interesting idea for sure. I seem to recall finding something somewhere that indicated the price was something around US$300-400? I don't remember where I got this information now as it was months ago, but this figure just sticks in my mind.

If I buy one, I will let you know.

[Paul Haese]

How does one align the collimator to the optical axis? This would seem critical to getting collimation correct. If you are not exactly square to the line you could align it all but still be totally out of collimation. There must be a way of maintaining square to the optical axis. If not then it is a gimick and not worth investigating.

[multiweb]

That's the first question I have asked them when emailing David at Hotech. How do you align on the primary optical axis and more importantly how do you square the board with the corrector/primary plane. I can't describe the whole procedure here but here's an extract from the answer he provided:

There is the fourth laser located in the center of the target projecting a crosshair laser toward the primary mirror (see last photo on the webpage). User will need to identify the exact 4 corners on the primary mirror internally or externally for the crosshair laser for center aiming reference because the secondary blocks the center crosshair. Once the crosshair is center aimed on the primary by referencing the 4 corners, the telescope then aim back to the target from the reflected 4-corners on primary back to the target's printed cross lines (see the first top right photo on the webpage). If both projecting and reflected crosshair are lined up with the primary's 4-corner and the target's cross lines, then co-alignment of the laser and the telescope is achieved.

[Barrykgerdes]

I am no authority on collimation nor do I have any qualifications in physics. I read pages and pages of ways to do collimation on a telescope using lasers etc but I am sure that most of the people trying to collimate a telescope do not know what they are really trying to do.

To me the aim of collimation is to adjust the optical system so that the light from the distant object that is falling on the full surface of the primary mirror is collected at the focal plane in the same phase so that the most use is made of the full area of the mirror. This of course requires very precise positioning of every item in the light path.

While I can see that the path of a laser beam can get the preliminary collimation very close, its precision is not equal to the wavelength of light that is the basis for the star testing that has always been the accepted way to do it.

Using a true point source very highly magnified produces diffraction of light around the edges of an object in the path that gives an alternate light path to the mirror that interferes with the direct beam such that it strikes the focal plane in and out of phase with the direct beam.

If we make this obstruction the circular secondary mirror in a reflector telescope and get it precisely in the centre of the light path it will produce concentric rings about the image of the point source.

This phenomena is used to make very fine adjustments to the mirror angle so that the rings become truely concentric. Because we are now measuring micro distances it can also show up other irregularities in the light path.

Thierry Legault wrote a very informative article on collimation. I think it is still available at

http://perso.club-internet.fr/legault

If not I still have a copy of it.

Barry

[multiweb]

Nothing wil replace a star test but this will greatly help to quantify mechanical alignment. Been playing long enough with pinholes in cardboards and lasers to see the value in this system. My idea of collimating is getting everything aligned mechanicaly as a starting point then you start tilting and tweaking things and in my experience it works fine because you need a starting point.

[Barrykgerdes]

Yes Marc

That is what the laser is good for and is the first step in collimation. I am only trying to stress that this is only the start to real collimation on a star.

I think Trevor is making an artificial star but it will need to be placed a long way down the back yard to subtend an angle of well under an arc second.

Barry

[Starkler]

Really? I can easily see collimation errors with standard tools that I cant see with a star test.

[multiweb]

If the seeing is good, the mirror at ambient temp and you have no tube current then a star test will show things that standard tools won't show. Unless you are using tools I'm not aware of? I assume laser, cheshire, etc?