Collimating a Moonlight focuser

[bomberbaz]

Hi all and ltns, been out of the loop recently but now I am back and as usual its with a problem.

Bought a Moonlight focuser a while back but I have a problem in that I cannot find a guide to collimating once installed on the tube. I have a vague idea but this is no good especially when you are collimating a F5 scope.

The intention once this is installed is to also clean the primary and then do a step by step collimation of the full scope to get it as near perfect as possible.

So has anyone got a link to collimating a focuser please?

Much obliged.

Steve

[bomberbaz]

surely someone has changed focusers on a newtonian? Can anyone give me pointers please?

FWIW my thoughts around this are as follows.  I was thinking that you mark the very centre of the secondary using some low tac masking tape & a pen, and then ensure the secondary is correctly collimated using a collimating cap. Then fit new focuser and using a correctly collimated laser, line it up with the central dot on secondary. Et voila, the alignment should be done.

Does this sound about right or am I maybe missing something?

TIA all

Steve

[Tinker1947]

I changed mine replaced it with a Moonlite, done the Newt then the Dob, they didn't need any adjustment as they use the same 4 holes in the tube as the original SW focuser, when you remove the SW focuser do it with the scope on its side they use a metal plate inside the tube and this needs to be held in one hand while the retaining screws are removed, fitting the Moonlite base is simple 4 screws through the hole and line them up with the base so its central, thats all there is to it, the Moonlite than fits on the new base with options for distance with the spacers and screws provided....less than 10 minutes and your done....

[Moonshane]

I never bother actually aligning the focuser as long as it looks about right. There's enough adjustment in the other elements without the need to do so.

[mapstar]

Hiya Steve,

I cant see a problem with your thought process above and shouldn't be too far out.

When I've fitted the moon light and also the feather touch on both scopes I've made I actually first aligned the focuser without the secondary in.

I put the laser in so the dot appeared on the opposite side of the upper tube then measured it from the underside of the upper tube assembly (you have a flex tube so would do the same)adjusting the top and bottom levelling grub screws so the laser hit the tape at the same distance up at both the focuser and opposite side.  I then put the secondary back in( assuming the spider is centred) and adjusted the focuser  left/right levelling grub screws so it was centred on the minor axis with the secondary aligned as best as possible. Then lock the outer bolts so it can't move

You would then collimate the usual way for a fast newtonian. 

Hope that helps and isnt too confusing

Damian

[bomberbaz]

Hiya Steve,

I cant see a problem with your thought process above and shouldn't be too far out.

When I've fitted the moon light and also the feather touch on both scopes I've made I actually first aligned the focuser without the secondary in.

I put the laser in so the dot appeared on the opposite side of the upper tube then measured it from the underside of the upper tube assembly (you have a flex tube so would do the same)adjusting the top and bottom levelling grub screws so the laser hit the tape at the same distance up at both the focuser and opposite side.  I then put the secondary back in( assuming the spider is centred) and adjusted the focuser  left/right levelling grub screws so it was centred on the minor axis with the secondary aligned as best as possible. Then lock the outer bolts so it can't move

You would then collimate the usual way for a fast newtonian. 

Hope that helps and isnt too confusing

Damian

actually makes perfect sense as that was what I was thinking as an alternative. I will decide which is least fiddly because as shane says, the adjustment in the rest of the process will remove any "minor" misalignment. Cheers

[Ricochet]

surely someone has changed focusers on a newtonian? Can anyone give me pointers please?

FWIW my thoughts around this are as follows.  I was thinking that you mark the very centre of the secondary using some low tac masking tape & a pen, and then ensure the secondary is correctly collimated using a collimating cap. Then fit new focuser and using a correctly collimated laser, line it up with the central dot on secondary. Et voila, the alignment should be done.

Does this sound about right or am I maybe missing something?

TIA all

Steve

I posted the technique I used for realigning a focuser in another thread. http://stargazerslounge.com/topic/258529-collimation-europa-200/?p=2827874 It was a similar idea except instead of marking a point on the secondary I removed the secondary and marked a point on the opposite side of the tube. However, I was repositioning the existing focuser so you might want to make some additional measurements to confirm that the distance to the centre of the new focuser is also a possible distance to the centre of the secondary. If you are able to reuse the old mounting holes for the new focuser I doubt it will be a problem.

If you can fit the new focuser without removing the secondary then you might find that it fits perfectly anyway and a minor collimation tweak on the secondary is all that is needed.

[John]

I upgraded my focuser to a Moonlite on my 12" dob. It fitted straight on and I did not find any collimation of the focuser was needed.

There are 4 collimation hex screws around the focuser to adjust the tilt if needed but I didn't touch those.

[bomberbaz]

Managed this a lot easier than expected but thanks all for the input it was much appreciated.

Simply made sure the secondary was correctly collimated before switching focuser. Then inserted a cheshire into the newly fitted moonlite and checked to see how the mirror looked through this. There was a need to tweak the bottom right hex key and use top right, bottom left to take up the slack to get a even view of white card around it and it was then bob on as they say.

I personally think that having all elements lined up is crucial to getting the best possible view from your scope. The new moonlite is really smooth even with a paracorr and the Nikon fitted and there appears no initial evidence of slop or tube flexing.

I would mention the only down side is my coma corrector (MPCC) does not now fit into the focuser as it was fitted into an extension tube which was a permanent part of the old crayford, I can however screw directly into the EP but that is simply too much messing. So I shall try it out without the CC for the views and see if its ok. If not I need to make additional adjustments to allow me to use the ext tube again with the focuser which can be done but lets see how we go without. 

Steve

[Tinker1947]

My Baader MPCC fits inside the Moonlite ok, used for imagine though, never used it on the Dob the view to me seem ok.....

[Lowjiber]

I use MoonLites.  The last step in the build process is to collimate every one before shipping it.  You may be looking for a problem that doesn't exist.

Moonlites obviously can be collimated if needed.  Contact Moonlite owner, Ron Newman, at: moonlite7@live.com

Ron is a great guy and customer service is first and formost on his mind.  He'll send you the instructions.

[bomberbaz]

I use MoonLites.  The last step in the build process is to collimate every one before shipping it.  You may be looking for a problem that doesn't exist.

Moonlites obviously can be collimated if needed.  Contact Moonlite owner, Ron Newman, at: moonlite7@live.com

Ron is a great guy and customer service is first and formost on his mind.  He'll send you the instructions.

Thanks for this buddy but I have the instructions, they came with the focuser.

Like I said it was the merest tweaks tbh, you can hardly tell unless you look really close at the focuser where the hex screws are. 

All I need to do now is a field test once the primary is re-installed.

Whilst on the subject of the primary, cleaning it was the simplest thing ever. I honestly cannot see what all the fuss is over this job, it took less than an hour and half hour of that was letting it soak in lukewarm water. Ready to re-install now once the replacement screws arrive. The ones I took out to get at the mirror were awful, cheap rubbish.

I will do field test hopefully after xmas and make a post to let others know how I got on and what I did to get where it hopefully will be. (IE Perfect  )

Steve

[phileefan]

Hi all,

Had a chance to visit Ron at his shop the other day. He gave me a tour of the shop and met all the guys. Very nice people. I had accidently knocked my focuser out of collimation and Ron made it right again. Anyhow, as Lowjiber  stated above, every MoonLite focuser is collimated before it ships out. Clear skies......... 

[Tinker1947]

I would think the best way to test is bung a DSLR in the focuser and take a short image, if the star look ok in all 4 corners leave it be, a MPCC will correct the Coma......