Skywatcher coma corrector alignment/tilt in focuser

[Pompey Monkey]

After sorting out the correct spacing between my SW coma corcector and SBIG camera (see here http://stargazerslounge.com/topic/255270-skywatcher-coma-corrector-with-ccd-and-filterwheel/ ), I am now facing another issue.

How do I keep the CC square in the focuser? At the moment I have the standard Skywatcher DS focuser. This is good in that it does not have any perceptible slop and also does not unwind under the weight of the corrector, filter wheel and CCD. However, the coma corrector is just held in the focuser by the two thumb screws and most definitely wants to shift about somewhat.

Does anyone have any ideas about how to fix this?

I have spent hours searching online for a definitive solution with no luck. So far my options are:

1. Drill and tap to accommodate a third thumb screw in the focuser;

2. Try a 2" adapter with a compression ring like this: http://www.firstlightoptics.com/adapters/flo-compression-ring-adapter-synta-skywatcher.html ;

3. Is there a quick-lock adapter that will fit the P-DS focuser?

4. Should I buy a second-hand Moonlight or the improved SW DS focuser (which is the incorrect radius for my 150 P-DS)?

BTW, Olly warned me about this when I stayed there a few weeks back. LOL.

Edit: I just found this old thread: http://stargazerslounge.com/topic/157954-avoiding-camera-rocking-in-focuser/

Typical: After all day getting nowhere, I find a possible fix five minutes after asking for help!

Any feedback would still be appreciated!

[Uranium235]

Only two of those four options are worth trying.

1) Third thumb screw - by far the cheapest solution, but requires access to a bench drill. Takes about half an hour.

4) Replacement focuser - by far the most expensive option, but requires a complete strip down of the telescope.

Go for the third thumbscrew first, and avoid compression rings like the plague.

[Uranium235]

Oh, and here is my solution. An internally mounted CC and M48 threaded/tilt compensated focuser:

[Pompey Monkey]

Only two of those four options are worth trying.

1) Third thumb screw - by far the cheapest solution, but requires access to a bench drill. Takes about half an hour.

4) Replacement focuser - by far the most expensive option, but requires a complete strip down of the telescope.

Go for the third thumbscrew first, and avoid compression rings like the plague.

Oh, and here is my solution. An internally mounted CC and M48 threaded/tilt compensated focuser:

Thanks for the reply Rob.

I read your thread on how you mounted the Baader MPCC in your focuser a few days back. Unfortunately, the SW CC does not have a removable stop ring and I'm not brave enough to take a file to it!*

I will try the third thumb screw option - I've already ordered an M4 tap from Ebay and, fortunately, I already have a pillar drill

It's also reassuring to see that you get your great results with the standard focuser

Cheers,

Paul

*I've already hacksawed 15 mm from the primary end of my OTA to eliminate the distroted stars caused by the focuser draw tube ingress into the main tube, so I'm not that timid!

[Uranium235]

Ahh I see youve already read about some of my adventures with Mr Hacksaw  

You will find tapping quite easy, just try to keep it straight and about halfway screw it out a bit (to remove any bits of metal), then finish the thread by taking it all the way through. Its fairly soft metal so it wont take long, and you can probably nick a spare M4 thumbscrew from another focuser or a barlow etc... theyre quite common.

[Stub Mandrel]

According to this you need Duck Tape.

[Pompey Monkey]

According to this you need Duck Tape.

I've not been in the Navy, but have worked in support of them. There's a saying that goes: "If it moves: grease it. If it doesn't: paint it"

[Pompey Monkey]

Ahh I see youve already read about some of my adventures with Mr Hacksaw

You will find tapping quite easy, just try to keep it straight and about halfway screw it out a bit (to remove any bits of metal), then finish the thread by taking it all the way through. Its fairly soft metal so it wont take long, and you can probably nick a spare M4 thumbscrew from another focuser or a barlow etc... theyre quite common.

I've tapped before, now and I'll tap into the future! Here's a couple of pictures of my DIY finder guider on my home made pier and pier-adapter (no close-ups, I'm afraid)

[Uranium235]

According to this you need Duck Tape.

Theres a fair chance neither of those will work. 1) The ducktape thickness is more than gap between the CC and the focuser 2" EP adaptor, stands a good chance of not going in at all or getting stuck in there. 2) I wouldnt spray WD40 anywhere near a telescope focuser unless it was taken off completely and away from the mirrors/optics.

[Pompey Monkey]

Theres a fair chance neither of those will work. 1) The ducktape thickness is more than gap between the CC and the focuser 2" EP adaptor, stands a good chance of not going in at all or getting stuck in there. 2) I wouldnt spray WD40 anywhere near a telescope focuser unless it was taken off completely and away from the mirrors/optics.

It is, however, perfect for filling the void between the outside of a 2" to 1.25" eyepiece adapter and the inside of the Meade tube in my finderguider. So perfect, in fact, that I forgot to mention it yesterday!

[Stub Mandrel]

It was intended humorously ;-)

But Duck Tape does hold together my Bahtionov Masks and makes 8" of aluminium fire extinguisher into a nice sliding fit dewshield for my 400mm lens.