Collimation with a twsit

[uspl]

Hi all,

De to a lack of storage space and the risk of damage caused by my kids, my little f7 scope gets moved a lot. As it is not of the highest quality I find I have to collimate it perhaps a bit more than others.

I looked at the Bob's Knobs option of replacing the Philips head screws but I finished up doing a bit more of an adjustment than just that.

Basically, I now have the primary mirror mounted on a spring loaded “raft”. For those who have seen heavy machinery mounted this way they will know what I mean. To explain:

First I removed all six screws, the mounting screws and the collimating set screws. These were standard Philips M4/.8 pitch screws. As replacements I have used socket head cap screws in black oxide stainless steel. These are 25mm M4 screws that have an Allen key head that then takes a 15mm diameter knurled plastic cap to give good finger grip.

To remount the primary I first added a small compression spring to each of the three mounting screws. These springs are high tensile steel and quite “springy”. By tightening the mounting screws only half their length, I now have the primary securely mounted in the tube and the springs keep it that way.

For the set screws, I used 40mm M4 versions of the mounting screws with the same caps fitted. As I adjust each of the collimating screws, the spring on the corresponding mount screw compresses and the other two expand. The primary can move freely over about a 5mm travel in any of the axis, more than enough to get alignment.

When I can locate some suitable screws for the secondary I will probably make the same adaption.

I have no vibration issues with the mirror mounted this way and collimation is a snap. If anything, my primary is now more vibration damped than ever as is does not make direct contact with the tube but rather floats on its raft.

I never have to adjust the mount screws at all, just a minor turn of the set screws and I am done. Maybe someone will tell me I have done this completely the wrong way as far as a mirror mount goes, but it works just fine.

[tnbk00 (Daniel)]

Sounds like a good mod. Is there any chance of some photos?

[uspl]

There you go, very simple and for about $3 all up very cost effective.