Primary locking knobs - yes or no?

[glend (Glen)]

Re GSO 12" mirrors, I have seen a thread here which suggested throwing away the primary mirror locking knobs when upgrading to the stiffer Farpoint springs, has anyone done this and are they no longer required?

I have the Farpoint springs on the way.

[mental4astro (Alexander)]

Hey Glen,

Locking nuts when actuated will actually cause a small amount of movement in the primary mirror away from the collimation you just painstakingly worked on achieving. Using stronger compression springs is by far the easiest solution. Using the stronger springs makes the locking nuts redundant, but is does also make the primary mirror more susceptible to needing more regular collimation tweaks. But this is nothing compared to having a great collimation result kicked away by "locking" nuts - bit of a contradictory term really.

All my Newtonians use stronger springs. I never liked locking nuts, and was only too happy to ditch them altogether. Even in my 17.5" dob, no locking nuts here either, and the springs hold collimation without any problems during a night's session.

Mental.

[Irish stargazer (John)]

I swapped the locking nuts out on my 12" lightbridge with Bobs Knobs springs. It holds collimation well without the locking knobs which were always awkward to use but as said previously requires checking every now and again. I always collimate the scope pointed in the general direction I observe in i.e. planet, moon etc..only takes a minute with the Glatter and Blug collimator.

[barx1963 (Malcolm)]

Ditto on the locking knobs. Cannot understand why they put them in. On my 12" GSO I replaced all the collimation knobs and springs with Bobs Knobs and found that it held collimation easily with the stronger springs.
I don't know if GSO have updated their springs when they went to the new knurled knobs that they now have, but I would have thought it would be much cheaper to use better springs and ditch the locking knobs.

Malcolm

[asimov (John)]

Certainly stronger springs are the way to go. My old 8" newt uses car valve springs & you need a socket set to collimate with. There ain't no moving that thing out of collimation in a hurry!