erick
23-12-2008, 06:30 PM
As a prelude, let me say that I know that, if you always use your laser collimator barlowed, its internal collimation is not a big issue. But most people seem to want to be sure that their laser collimator is well aligned, since most laser collimators can be used, and are used in the non-barlowed configuration.
With my previous GSO deluxe laser, I followed the approach recommended to me and constructed a V-block in which the collimator sat, at two contact points, one on the barrel and one on the rear of the body (see image). I adjusted the grub screws holding the internal laser until the laser spot turned in a tight circle some 4-5 m away.
When I bought my new HoTech laser collimator( http://www.hotechusa.com/collimator.html ), I set off to do the same exercise. It’s a little more difficult since the barrel end now has rubber o-rings so it won’t rotate as smoothly, but I tried. I didn’t like the result, so I queried HoTech. David Ho advised me that there was no reason to believe that the rear of the collimator’s body was a reasonable reference point which, in retrospect, makes a lot of sense. Rather, the laser should be rotated around the barrel that fits in the focusser.
Now I didn’t have a lathe where I could mount the collimator barrel in the spindle and rotate it, (and have the required 5m or more distance from the collimator to a wall at which the spot’s motion could be observed). On David’s advice, I designed a tool to perform this task.
Essentially it is a cylindrical piece of metal with a hole through the central axis and a hole at one end, on that axis, and which is exactly centred in, and parallel to the outer surface of the cylinder. I took the opportunity to prepare a 2” hole at one end and a 1.25” hole at the other, so it could be reversed for different sizes of laser barrel. The tool sits on a v-block. My very skilful machinist (Alan, ajlane on IIS) did a marvellous job, deciding to fit Teflon to the edges, then bevelling them slightly to allow for smooth and accurate rotation of the tool. We extended the base at each end so that it could be clamped down to reduce movement.
See photos in this and further posts.
It was designed primarily for my HoTech laser collimator which came with a 1.25” barrel and a 2” adapter. The collimator is inserted in the hole and the o-rings compressed to centre it and hold it secure.
However, I asked Alan to provide a grub screw at each end so that collimators (and anything else) without this centering technology could be placed in the tool. The grub screws were positioned the same distance away from the edge as the thumbscrew is below the lip of a GSO focusser. They end in a plastic pad to avoid damage to the device being “clamped”. The also fall below flush on the outside surface so they don’t impede the tool when it is being rotated.
It is elegant, pretty and works like a charm. Thanks David and Alan!
Elsewhere, I’ll report on the outcome of tests of my HoTech laser collimator.
With my previous GSO deluxe laser, I followed the approach recommended to me and constructed a V-block in which the collimator sat, at two contact points, one on the barrel and one on the rear of the body (see image). I adjusted the grub screws holding the internal laser until the laser spot turned in a tight circle some 4-5 m away.
When I bought my new HoTech laser collimator( http://www.hotechusa.com/collimator.html ), I set off to do the same exercise. It’s a little more difficult since the barrel end now has rubber o-rings so it won’t rotate as smoothly, but I tried. I didn’t like the result, so I queried HoTech. David Ho advised me that there was no reason to believe that the rear of the collimator’s body was a reasonable reference point which, in retrospect, makes a lot of sense. Rather, the laser should be rotated around the barrel that fits in the focusser.
Now I didn’t have a lathe where I could mount the collimator barrel in the spindle and rotate it, (and have the required 5m or more distance from the collimator to a wall at which the spot’s motion could be observed). On David’s advice, I designed a tool to perform this task.
Essentially it is a cylindrical piece of metal with a hole through the central axis and a hole at one end, on that axis, and which is exactly centred in, and parallel to the outer surface of the cylinder. I took the opportunity to prepare a 2” hole at one end and a 1.25” hole at the other, so it could be reversed for different sizes of laser barrel. The tool sits on a v-block. My very skilful machinist (Alan, ajlane on IIS) did a marvellous job, deciding to fit Teflon to the edges, then bevelling them slightly to allow for smooth and accurate rotation of the tool. We extended the base at each end so that it could be clamped down to reduce movement.
See photos in this and further posts.
It was designed primarily for my HoTech laser collimator which came with a 1.25” barrel and a 2” adapter. The collimator is inserted in the hole and the o-rings compressed to centre it and hold it secure.
However, I asked Alan to provide a grub screw at each end so that collimators (and anything else) without this centering technology could be placed in the tool. The grub screws were positioned the same distance away from the edge as the thumbscrew is below the lip of a GSO focusser. They end in a plastic pad to avoid damage to the device being “clamped”. The also fall below flush on the outside surface so they don’t impede the tool when it is being rotated.
It is elegant, pretty and works like a charm. Thanks David and Alan!
Elsewhere, I’ll report on the outcome of tests of my HoTech laser collimator.