Newtonian experts - help adjusting a NOVAK cel

[Logieberra (Logan)]

Evening guys

I've got a 10" Skywatcher newt that I'm very fond of... aside from the pimary mirror cell.

So I purchased a used Novak cell for the mirror. She's solid.

Problem is that the cell is designed for a larger tube, so the Novak arms are too wide. They need to be cut to size.

The standard skywatcher cell is designed for the 10" mirror, naturally, so it's a snug fit and is perfectly centred with spacers etc.

The Novak cell is customizable, and can be adjusted every which way.

Questions:

1. how important is it that the mirror be perfectly centred in the cell?

2. how can I do this?

3. if I get the arms cut down, how pefect must the cut be? Can I do it myself with a hacksaw or do I need a machine shop to do it spot on?

Here is the unit. The three arms are wider than the scope's tube, they need to be trimmed about 10mm on each arm.

I need your help here. I got a 'D+' in highschool metal work

[catseyeman (Jim Fly)]

Hi Logan,

Optimal scope performance does not require "Precision" centering of the Primary in the tube. If you are "careful" with your hacksaw to cut the support arm lengths to within 2mm shortest to longest, you'll be fine. I'd be more concerned about having enough clearance inside the tube for the mirror-support assembly arms and whether or not the clips will keep the Primary secured. What size mirror is the cell designed for?

Regards,

Jim Fly

[bmitchell82 (Brendan)]

that was my exact expression to logan in any case. My main concerns are not due to the mirror cell fitting, because as long as everything fits then its all good. My main thing is about the collimation proceedures.

He has cats eye gear and i recently upgraded the whole secondary system for him with a kit i make because.

A. the SW vanes are too light they flex too much and make it really hard to get fine adjustments. so new 1.5mm Stainless vanes and a 40mm secondary stalk holds everything super stiff.

B. The rear cell needs to have tool less collimation as so you can adjust the fine adjustments needed for cats eye gear. the adjustments need to be smooth and easy this is the only way to get really nice adjustments!

The Novak although strong and definately well designed does not offer tool less design and you would need to use a socket to sort it all out and that could become tiresome!

My preference is for the Orion optics mirror cell. but yeah you have to work with what you have and i know this due to being a uni student!

[catseyeman (Jim Fly)]

I agree - I would definitely replace the 3 hex adjustment bolts with threaded-stud knobs of the appropriate size like can be seen and had here:

http://www.mcmaster.com/#knobs/=8itpr3

[Logieberra (Logan)]

Thanks guys

And welcome Jim, Brendan and I love the Catseye equipment.

Jim, the cell is designed for a 10" mirror, so she's within specs.

Great ideas on the knobs - will upgrade when I get a chance.

I won't be using the stock mirror support clasps. I'd look to use silicone / solastic to keep the mirror in there. No mirror pinching with this approach.

One question please Jim, "cut the support arm lengths to within 2mm shortest to longest"
- so if they're cut, give or take 2mm shorter or longer between all three arms they should be fine? I think that my hacksaw skills can provide these tollerences!

What I like about the Novak is the thermals should be great - air can pass straight through.

And it has double the springs (6 vs. 3) and they're stronger springs then the Skywatcher variety). It is VERY difficult to push mirror once they're taught. Where as the Skywatcher cell can be moved by hand if pushed...

A work in progress.

Regards,

Logan.

[catseyeman (Jim Fly)]

Originally Posted by Logieberra

One question please Jim, "cut the support arm lengths to within 2mm shortest to longest"
- so if they're cut, give or take 2mm shorter or longer between all three arms they should be fine?

Roger that! Just remember the fail-safe rule: "Measure twice - cut once."

[GrahamL]

Is the cell cast ?

[astro744]

I have the same primary holder and it requires a 300mm ID tube. In fact I dont think you would want less than 300mm ID to avoid tube currents spilling into the light path. How much do you have to take off? If only a little why not use a bench grinder with a side sanding disc attachment. You may go through a few discs of course sand paper but you should get a better result.

[stringscope (Ian)]

Hi Logan,

Happy to help out if you want to bring the scope/mount aroung to "Ian"s telescope workshop" for a look see.

I have sent you a PM.

Cheers,

[catseyeman (Jim Fly)]

Originally Posted by astro744

How much do you have to take off? If only a little why not use a bench grinder with a side sanding disc attachment. You may go through a few discs of course sand paper but you should get a better result.

Logan stated in his original post that he needed to remove 10mm - that's probably a bit much for a "bench-grinder-only" approach. A bench grinder WOULD be useful for the final "tweak" of the lengths (having cut a bit on the long side with the hack saw).

Regards,

Jim Fly

[astro744]

Originally Posted by catseyeman

Logan stated in his original post that he needed to remove 10mm - that's probably a bit much for a "bench-grinder-only" approach. A bench grinder WOULD be useful for the final "tweak" of the lengths (having cut a bit on the long side with the hack saw).

Regards,

Jim Fly

Sorry. Missed that number.

[Logieberra (Logan)]

Graham: not quite sure of the material sorry.

Astro744: any chance of grabbing more details about your setup. How best to mount the pimary in these cells, and any other helpful details?

Ian: thanks for the offer to help. Sounds great. The benefits of CAS membership

Jim: will be sure to double-tripple check the numbers before hacking

[bmitchell82 (Brendan)]

hehehe being ally it would stuff the grinder disk before you went half way though it damn ally!

The skywatcher standard tube is a grand 285mm ID (don't ask me why they did that the silly buggers) it vignettes the 75% illuminated light cone! very annoying! But in saying this it is a Dobsonian hahahaha.

Good luck Logan with getting this thing together!