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Re: Newt Secondary Mod Revisited

PostPosted: Sat May 07, 2011 6:13 pm
by Malamuteboy
Thought I'd ask as I had the sense to check mine today as it's a 300 scope and I was ordering all the bits. (I'll have spares soon also) Then when I watched your tute again I noticed that it seemed the same size.

Hope you didn't mind.

Steve.

Re: Newt Secondary Mod Revisited

PostPosted: Sun May 22, 2011 9:50 pm
by DaveD
Hi Dion,

Excellent tutorial. Thanks.

I mentioned it to a fellow Newt user who pointed me at the so called 'milk jug' mod. See here:

http://www.cloudynights.com/ubbthreads/ ... t/all/vc/1

It seems 'milk jug' is a generic term for any plastic washer cut from a milk carton or similar. The plastic washers I've cut from a standard UK milk carton are very smooth on one side. So I've tried this mod on my 200P using two such washers, with smooth sides facing each other and it seems to work. The idea seems to be that the polyethylene washer has some resilience to pressure of the collimation screws making moving the secondary holder more consistent and controllable. I've also rounded the tips of my collimation screws into hemispheres (Bob's knobs, I'm afraid) to spread their pressure on the plastic washer.

I final point is to graphite under the head of the central holding screw since this is the joint that is moving when the secondary is adjusted.

Clear skies

Dave

Re: Newt Secondary Mod Revisited

PostPosted: Thu Mar 22, 2012 3:36 pm
by ReesD
Hi Dion,

What is the length of the M5 centre bolt?

Thanks.

Re: Newt Secondary Mod Revisited

PostPosted: Thu Mar 22, 2012 5:46 pm
by Dion
Hmmm, now you got me, it's either 35 or 40mm, if you get 40 you can always cut it down.

Re: Newt Secondary Mod Revisited

PostPosted: Sun Apr 15, 2012 7:53 am
by peterwilson26
Hi Dion,

Thank for your Videos I have learnt a lot from them and done a few mods on my Skywatcher 200PDS.
Through the summer I am going to flock my scope and whilst doing so I am going to do your mod on the secondary mirror by fitting a S/S and Teflon washer. Forgive me if this is a daft question, but by fitting these two items it is going to move the mirror 2mm out of alignment of the focuser tube. I know I must be missing an obvious answer here.

Thanks,
Peter

Newt Secondary Mod Revisited

PostPosted: Sun Apr 15, 2012 12:44 pm
by nev
You adjust the central screw to compensate for the 2 mm


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Re: Newt Secondary Mod Revisited

PostPosted: Sun Apr 15, 2012 1:07 pm
by Dion
What you find is that if you take a small makeup mirror (doesn't every bloke have one!) and place it in your yube under the secondary, you will probably see that there is a fair gap between the centre boss of the spider and the boss of the secondary, ie the grubs push it out a fair amount, also, when you come to centre the secondary under the focuser, in skywatchers you nearly always tend to find that it actually needs moving a tad more 'down' the tube, (towards primary) so the washers actually tend to tighten up those tolerances and it all balances out.

Re: Newt Secondary Mod Revisited

PostPosted: Sun Apr 15, 2012 2:35 pm
by peterwilson26
Great stuff. Just thought I'd check before I took the thing to bits.

Re: Newt Secondary Mod Revisited

PostPosted: Wed Apr 18, 2012 1:03 pm
by peterwilson26
Hi Guys,

Could you recommend a supplier for M10x35 washer and the M4 M5 socket screws, all of the suppliers I have looked at just supply in packs of 50 or 100.

Thanks

Re: Newt Secondary Mod Revisited

PostPosted: Wed Apr 18, 2012 1:11 pm
by Dion
ebay is your very best friend for this stuff Peter.