Milk bottle top mod for collimation

[Trentend]

Bobs knobs arrive tomorrow to replace the existing 3 secondary adjusting screws in VX12. Wanting to add the milk bottle top mod while I’m at it. Will hold on to the secondary mount (but not touching the mirror) as I carefully unscrew the centre screw keeping the scope horizontal. Presume it’s easy to get the centre screw back on afterwards, being spring loaded, without any special tools?

[fwm891]

I think you just replace one adjustment screw at a time so you maintain the mirror's overall position not all three at once? Cut a slot in the 'washer to allow it to pass the centre bolt.

[AKB]

I did just what the OP suggest, having drilled the tops with a central hole.  I say “tops” because I used two (read somewhere that this was recommended.)  

You might consider slackening off all the adjustment screws and then tightening up the centre one to accommodate the extra thickness which otherwise moves the secondary a bit closer to the primary.

However you do it, you will need to re-collimate afterwards, anyway, and check the centering of the secondary under the focuser. 

[Trentend]

Removed the secondary and surprised not to see a spring, just the central screw going straight in to back of the stalk. Should I fit one? Don’t think I have to but will a spring make the adjustments smoother?

Also some interesting burr marks - the outer ones align to the current adjustment screws (now replaced with Bobs knobs, soooo much better). There are also some marks from what appears to have been adjustment screws much closer together! Not a problem as I’m going to cover these with a plastic washer (milk carton lid too small) but still odd!