Mirror's arrived and now the fun starts

[Kaptain Klevtsov]

Phil, I had springs at first but found that they were springy and let the mirror move out of collimation depending on the angle of the 'scope. Just a pointer for you to watch out for. Other than that, it's looking very interesting, can't wait for the next installment.

Captain Chaos

[geppetto]

Daz

That company seems to hold most springs imaginable in stock

so yes they must have something for your Revelation.

Its just a case of picking the correct ones.

CC

See what you mean about the "too springy" effect.

I did order three very stiff springs to reduce that effect but now you've mentioned

it, I think I will include three extra screws to butt up against the mirror after collimation

to lock it in place, similar to what's on the back of my Revelation.

Edit: not butt up against the mirror, butt up against the 3" ply pads else the screws could push the mirror off the pads

[geppetto]

This is the cheapy plasticy 2" focuser I got from Surplus Shed a couple of years back for $6 8)

It works quite well considering and will do for this job until funds allow for a metal one (seen some for £39 if

I remember correctly)

Also, the three springs (might have gone a bit far with the stiffness of these but perhaps that's a good thing)

[Astroman]

Rather than your individual 3" dia. 1/2" ply disks, I cut a continuous circle of plywood, precision drill and countersink 3 holes for the mounting screws, then silicone the mirror to the ring. The holes are as close to the diameter of the screws as possible, making a tight fit. When assembled, the thickness of the circle and the mounting board, along with the stiffness of the springs makes a nice, stiff cell with little movement, regardless of mirror position in the box. Just a suggestion.

[geppetto]

Good points AM

I decided on three pads, thinking that it would leave a lot of glass exposed

for quicker cooling and a more equal temperature on both sides of the mirror.

However, thinking along the lines of your method, I could cut a circle of ply and then

remove a central portion of it to help the cooling (is that what you did or did you leave

the disc whole?).

Hmmmmm... interesting... its good to talk as they say 8)

[Astroman]

Yes Phil, I should have said "annulus", but the crowd around here may misconstrue it. 8)

[geppetto]

Right OK..

Actually thats going to be a lot easier to put in the correct place on the mirror

than the three pads...

Change of plan then, mirror mount changed to AM's ann...better not...erm doghnut

Thanks AM

[Astroman]

[Kaptain Klevtsov]

If the springs are real brutes Phil., Id put a nut on the coutersunk screw, then a washer for the spring to sit on, then another nut. That way the spring load is not on the plywood where it could dig in or pop the screw though later. If this doesn't make sense, I'll do a picture later.

Captain Chaos

[moondog]

Phil

Yesterday I was going to post you a detail of a reflector mirror cell design that I used some years ago.

It's exactly as Astroman described. I couldn't send it as my internet connection was down. :insects1:

For the sake of completeness I have posted it anyway.

I have shown 2 collimation ideas - one without a spring - which I used, and one with a spring that you want to use.

Hope this helps

MD

[geppetto]

Yep, that makes sense, cheers CC.

Duly noted and added to the design

Thanks for the drawings MD

That pretty much confirms that the design is OK

Will go with the springs on the Mk 1 since they are stiff little bighters.

Any problems on first light and the cell can be quickly changed to non spring

Off to get some wood in a few minutes.. 8)

[justin138]

Don't leave us in suspense Phil - UPDATE!

[geppetto]

Don't leave us in suspense Phil - UPDATE!

Well not a lot really

Got back from town with a small heap of MDF and ply and bolts and stuff.

Hope to make a start tomorrow...

Spinning saw blades..MDF...Plywood...Mmmmmmmmmmm 8)

[geppetto]

Made a start this morning.

Cut the parts and assembled the mirror end OTA box.

Just finished routing out the doughnut for the mirror cell and set the

collimation bolts.

So far so good

[GordonCopestake]

Looks nice, what thickness is that MDF?

[geppetto]

Gordon

The doughnut is 18mm birch ply...

Very tough stuff 8)

[lunator]

Phil

Good progress is being made

How long did it tak you too cut the ply.

Cheers

Ian

[geppetto]

Not long Ian, these routers are the business

Made the cell back board out of two thicknesses of MDF making 1.5" in all.

Mounted the doughnut and pleased to say, this end of the QDD is rock solid.

[geppetto]

Done a test fit of the mirror assembly and all looks OK

This things going to be a beast :shock:

I made the bottom OTA box 600mm long so that it gives me plenty of space

to mount the ALT bearings at the balance point.

Also its heavier and I'm hoping that will bring its center of gravity nearer to the ground.

As a bonus. it should help protect the mirror and cut down on dew.

[Kaptain Klevtsov]

That looks awesome Phil. Bet you can't wait to have a look through it.

Captain Chaos

[geppetto]

Bet you can't wait to have a look through it

Too right CC.. its got me juices flowing that's for sure

[Caz]

Blimey Phil, you don't let the grass grow do you??? :shock: Very impressive!!

Caz

[richard42]

looking good

[FLO]

Starting to feel genuine excitement here

[GazOC]

Looking well Phil. You've got more done in 4 days than I got done in 4 years!!!