No Tool Collimation, Bobs Knobs

[Charic]

Has anyone ever noticed after upgrading to Bob's Knobs, and  especially if you took the option of fitting some new replacement 'SPRINGS' to the  Primary mirror, that there is the  need to collimate more often?

I have been mulling over this particular question and  upgrade for a long time now, but the cost  for  Bobs Knobs is off-putting,  just for a few bolts,  and  I can't see how the Springs can make an improvement over the stock 'O' rings?

On my telescope the OTA end collar has 6 holes, 3 are threaded for the locking Allen bolts, and 3 are just countersunk holes, not threaded. This is where the adjuster passes through and screws into the Mirror Cell housing. Finger tightening  the 3 adjusters should put the mirror cell flat to the OTA collar mount, any further tightening against the 'O' ring will add any tilt required to align the mirror.  This adjustment is slight and at most, can be  no more than the thickness of the compressed 'O' ring. Unscrewing the adjuster will loose any tilt, against the OTA collar to flat level again then eventually  loose again! This is the only advantage I can see for the use of 'springs', but if the mirror needs this much movement, I would suspect something is wrong?

In order to use 'thumb' type adjusters, they must have some  length / reach, in order to use them by hand, so  they would need some sort of sleeve / collar  between the  head of the adjuster and the counter sunk hole on the face plate in order to hold them in place.  I believe this is incorporated in Bobs' Knobs, ( looks like a white sleeve as far as I can see from the small images supplied)

If I could find a suitable  sleeve / collar then I could easily make my own kit.

I can't see the advantage at present of fitting springs in-place of the 'O' rings.  I think the mirror would be to loose under spring tension alone, requiring more regular collimation at the slightest movement of the telescope, hence my original question.......need to collimate more often.  I believe the Mirror cell is held more securely with the use of the standard 'O' rings. 

Your thoughts please!

[Tinker1947]

These might work, i use them on the secondary mirror

http://a2a4.com/acatalog/KNURLED_THUMB_SCREWS_HIGH_A_2-1.html

[Floater]

I fitted Bob's Knobs, Chas, and the advantage for me was no longer having to use a Phillips screwdriver when collimating - which I found to be a right royal pain! I find collimation is pretty solid and I don't need to do too much adjusting and don't need to do even that too often. (Mind you, as you'll know, up our way opportunities to stargaze have been few of late ...)

I didn't go for the springs or the secondary mirror set, just the six replacements for the primary. Well worth it as far as I'm concerned. But if you're happy with your setup, you know what they say: if it ain't broke, don't fix it!

[Gazabone]

I've fitted Bobs Knobs to my SW250 Dob but not springs. Seems to hold collimation very well for me.

[ronl]

The newer SW 200p comes with Bob's Knobs type screws fitted, and they still use the

O rings, mine keeps collimation very well, only needs a tweak now and then, the knobs

do make life easier, and faster. 

[brantuk]

Another advantage of bob's knobs style colli screws is that you won't risk dropping an allen key on the primary mirror. I found that any secondary mirror adjustments are done a lot faster. Not tried the stronger springs yet - but I do intend to at some stage.