Colliminating Secondary of 130P-DS

[Stefan73]

I'm trying to slightly adjust the secondary to get the collimination spot on (and as a learning exercise). 

As far as I know it's the three little allen key bolts at the front I need to turn gently to move the laser dot around the primary (one of which has an allen key in it in the photo).  The problem is I can't shift them at all. Applying force does move the secondary but it just moves back when I stop so I think I'm just bending the spider slightly rather than actually turning a bolt.

I'm presuming I'd start by slightly undoing (anti clockwise) one bolt?  Is there some sort of locking screw I need to undo first?  WD40?  Just more force?

[wookie1965]

You may have to loosen the central screw, I would check to make sure the 3 collimating bolts have not dug into the metal at the back as when you try to adjust them they will snap back into the same position.

 

[Ratlet]

Been going through this myself.  You might need to loosen one first before you can tighten the others. Just don't loosen two at once too much as the mirror might rotate and you'll have an extra step (rotate the secondary to the correct position).

Good luck.  It's not too bad once you get going.  Bit of a steep learning curve but levels out pretty quick.

[LaurenceT]

You may find it easier to replace the Allen key bolts with Bob's Knobs. I'm not brilliant at collimation but using these bolts on the primary and secondary mirrors alleviates my stress! Sorry if you've already heard of them.

Bob's Knobs StellaLyra / Celestron / Sky-Watcher Newtonian Collimation Knobs | First Light Optics

[alacant]

1 hour ago, Stefan73 said:

problem is I can't shift them

Hi

Turn the hex key 90º and give it a sharp tap. The whole central secondary assembly will now be loose. 

To adjust the tilt, loosen ONE at a time tightening ONE other to take the slack. If you're using this for imaging, use a Cheshire sight tube with cross hairs to get it perfect.

To give yourself a fighting chance and retain your hair, replace the sw grubs with m4 screws. 10 for €1:

HTH

 

 

Edited August 31, 2022 by alacant

[bosun21]

This is a straightforward operation. First hold the side of your secondary holder to stop any rotation and loosen the central screw a half turn. This will now allow you to adjust the three Allen screws (one at a time). Select the one adjacent to the direction you need your laser dot to travel to be in the central mark on your mirror. By small adjustments you will easily achieve this. Once centered retighten the central screw. Job done.

[Stefan73]

Thanks all.  It did just need a bit more oomph.... your answers gave me the confidence to give it a bit more oomph!  Looks sorted now according to lasers and cheshires so I'll see if the stars agree.

Allegedly secondaries hold their position well but, if not, I may well replace the grubs as suggested.

 

[Spile]

I find on average ante when I am not transporting my 8” reflector in my car, I will need to tweak my secondary (see https://astro.catshill.com/collimation-guide/) every month or so. The primary rarely needs adjustment.