Help with collimation of MN190

[TrickySpot]

Hi Guys,

Any chance that somebody would be willing to assist me in collimating my MN190? It took a hard knock a few weeks back and its totally off - and the secondary seems to be glued into the corrector lense, so struggling to rotate it with the centre screw that is actually for the in/out movement of the secondary.

It would be gratefully appreciated! I'm in West Drayton, West London and if a fee is required then just me know!

Thanks,

Martin

[TrickySpot]

Does anybody at least know if there should be springs between the primary mirror and the back housing where the collimation screws pass through? Mine doesn't have, so when you loosen a screw, there is nothing to take up the slack, so collimation doesn't seem possible.

I did manage to loosen the secondary from the corrector though, so its just the primary thats now hassling me.

Thanks!

[Langy]

I'm sure someone will soon be able to help.

Just a thought from someone who knows nothing about it, if you loosen one screw and tighten the other two does that not work?

Imagine that there are no screws but the mirror sits in a centre piece which is help in place by tightening all three screws, depending on how far each screw is in alters the tilt.

As I said I may be totally wrong, the only thought about having springs is that you add the extra chance of vibration in unless then are very compressed.

[TrickySpot]

I'm sure someone will soon be able to help.

Just a thought from someone who knows nothing about it, if you loosen one screw and tighten the other two does that not work?

Imagine that there are no screws but the mirror sits in a centre piece which is help in place by tightening all three screws, depending on how far each screw is in alters the tilt.

As I said I may be totally wrong, the only thought about having springs is that you add the extra chance of vibration in unless then are very compressed.

Thanks Paul, but no - it doesn't work like its supposed to, i.e. loosen one, tighten the other two. For mine to work, there must either be springs, or something that prevents the screws from winding out of the body (perhaps a washer of sorts on the inside??), or the mirror must pivot on a central pin like the secondary.

I think the knock it took must have messed up whatever was in place, or the entire primary has shifted something stupid relative to the back plate. I think it might be time to admit that its too damaged to fix - I can still get excellent photos if I collimate after each slew, but after a slew the primary rocks/moves too much because of the one screw whose slack can't be taken up.

[opticalpath]

It sounds like maybe one of the primary adjustment screws has become detached from the mirror cell, so when you 'loosen' it, it is not moving the mirror cell as it should.  I would try loosening off the small hex socket screw adjacent to the 'bad' Philips head screw then try 'tightening' the Philips head screw to see if it grips something and becomes snug, or if it just turns endlessly. 

 

If you can't figure out what's going on, it's not difficult to remove the whole primary mirror/ cell assembly from the bottom of the tube.  Then you could inspect it and see what's up.  You just have to remove the six screws around the circumference of the OTA and carefully pull out the whole assembly.  If you do, just put some tape markers on the tube and on the bottom assembly first, so you can be sure to replace it in the same orientation.

 

I'm not far from you - if you still want some hands-on help PM me.

 

Adrian

[Gunnar]

Does anybody at least know if there should be springs between the primary mirror and the back housing where the collimation screws pass through? Mine doesn't have, so when you loosen a screw, there is nothing to take up the slack, so collimation doesn't seem possible.

I did manage to loosen the secondary from the corrector though, so its just the primary thats now hassling me.

Thanks!

Hi

There are no springs between backhousing and mirrorcell on the MN190. Primary adjustment screws run thru flexible rubbergrommets as i remember it, not much flex in them they are only about 6mm thick.

http://stargazerslounge.com/topic/141012-skywatcher-190mn-fitting-of-a-moonlite-focuser/

Gunnar

[Gunnar]

Hi

There are no springs between backhousing and mirrorcell on the MN190. Primary adjustment screws run thru flexible rubbergrommets as i remember it, not much flex in them they are only about 6mm thick.

http://stargazerslounge.com/topic/141012-skywatcher-190mn-fitting-of-a-moonlite-focuser/

Gunnar

http://www.telescope.com/assets/product_files/instructions/29370_07-09.pdf