Skywatcher MN190 primary mirror

[TrickySpot]

Hi Guys,

Can any owner of a MN190 please let me know if the screws that adjust the primary mirror are spring loaded? When I unwind mine, they just wind out, they don't 'push' the mirror forward, as if there is a spring missing, driving me crazy  - any help would be most appreciated! 

Thanks in advance!

[opticalpath]

Hi.  There are 6 screws involved in the primary tilt adjustment.  The three Philips head screws 'pull' the mirror cell towards the bottom of the OTA as they are turned clockwise.  Beside each of the three Philips screws is a small recessed hex socket screw.  These push the mirror cell in the opposite direction when they are turned clockwise.  So the way the adjustment works is that there are three pairs of push-pull screws that oppose one another.  So when you 'loosen' one of the Philips screws, you should 'tighten' the corresponding hex socket screw, for example.

Not sure why you're not seeing some movement of the mirror cell, though.  Are you sure it's not moving?  It's hard to tell unless you're looking at the reflections through the focuser.

It's perfectly possible to remove the whole primary mirror assembly if you have to do this to work out what's going wrong.  Just undo the six screws around the circumference of OTA and the whole mirror+ mirror cell pulls out.  But mark the position of the cell on the tube with some tape first so you can put it back in exactly the same orientation.

Adrian

[perfrej]

The "springs" consist of two or three stacked O-rings and they are on the normal screws (3 of them). Just take the cell out of the tube; it does not affect collimation at all.

/per

[TrickySpot]

The "springs" consist of two or three stacked O-rings and they are on the normal screws (3 of them). Just take the cell out of the tube; it does not affect collimation at all.

/per

Just waiting for some other news re OTA and can then perhaps dismantle it to see whats gone wrong....I see you guys are the experts though, I read through your very long thread on MN190 collimation!