22" F3.38 DIY Scope Build

[SimonfromSussex]

Finally the cell and spider arrived from astrosystems on Saturday so I can get going on the build   

It's hopefully going to be a 22" F3.38 scope.

I'm going to go with a classic obsession design given how fast the scope is (I cannot afford any flex).

I doubt I will make anything as beautiful as some of the other built scopes on here but I'm going to do my best.

For me the build is simply a tool to let me view what the mirror can show so it's very much going to be practicality over looks (that's my excuse anyway).

Mirror info is here: http://stargazerslounge.com/topic/222338-john-nichol-22-f338-mirror-has-arrived

I ordered a kit cell from this company in the states:

http://astrosystems.biz

Here is the jigsaw puzzle ready to assemble

Started today by priming the mirror point system

I also ordered the spider, secondary holder & top cage fixing brackets from astrosystems.

The quality of their product looks really good but it took ages to ship, quoted 3-4 weeks but was 9 before sending.

Very reasonable though so if you can wait for their product I think it's worth it.

Rustysplit is going to help with the wood working (almost certainly couldn't do it without him, cheers Al!!). 

Hopefully start on the top cage tomorrow, getting excited now!!!!!!

[nightfisher]

Im not a dob man, but look forward to seeing this in build

[estwing]

Great big dob build ......YES!

[JRM]

Awesome,will be watching the build, keep the post coming please.

Rick M

[SimonfromSussex]

Good day today up at Al's workshop.

Lots of the cutting for the bearings, mirror box, and rocker box done.

Plus ply in press gluing over night to make double thickness (we are working with 3/4" ply and need 1.5" for the bearing surfaces).

Then we started the secondary cage cutting (remembering to mark post holes and top bracket positions while we still had a central hole)!

Firstly we made a ring indent with the router

Then we jig-sawed out the rough outer section.

Finally inner ring cut with the router. 

[Chris]

I love it, subscribed to thread with bells on! :-)

Chris

[starman345]

Great stuff Simon! I'm envious of that John Nichol mirror, did you settle on a secondary mirror size yet?

[Daniel-K]

hurry up and get it ready for DFII

[SimonfromSussex]

115mm for the secondary. It's blooming massive!

I'll def do my best Dan!!

[swamp thing]

Cool. Will be watching this one with interest Simon.

[estwing]

if its anything like Alans it will be fantastic....

[SimonfromSussex]

if its anything like Alans it will be fantastic....

No pressure then 

[Rustysplit]

Bright and early start tomorrow Si. Don't forget the biscuits!!

[astronymonkey]

Looking forward to how this is going to turn out, youve made a great start though.

I was wondering what sort of weight the primary mirror was, and what thickness it is ?

Cheers

[SimonfromSussex]

Not sure on the exact mirror weight yet Astromonkey, except to say VERY heavy!!??

It's 44mm thick.

[sloz1664]

115mm for a secondary. That's bigger than the first Newt I purchased     

Looking forward to the rest of this superb project build. 

Steve

[mapstar]

Good luck with the build I'll be watching with interest

1.5" for the bearings is pretty hefty? How did you come to that width?

Damian

[SimonfromSussex]

Good luck with the build I'll be watching with interest

1.5" for the bearings is pretty hefty? How did you come to that width?

Damian

We are using this book Damian and that was the recommended spec:

http://www.obsessiontelescopes.com/publications/index.php

I think on Steve's (swampthing) 20" scope his were actually slightly wider than that.

[SimonfromSussex]

Another good day today, starting to take shape.

Al, got the holes drilled in the two pre cut rings first thing and counter sunk some holes for the alu tubes.

I purchased these tubes: Aluminium Round Tube (6063T6) 11/4 in x 16 swg - 2500 m from: 

http://www.aluminiumwarehouse.co.uk/Aluminium-Round_Tube/c120_131/index.html?osCsid=6qcaj5fu8t3qqidl5lnq3rbtj2

I also purchased these connectors (M8x1.2MM THRDED SPRING INS) to hold the tubes in place:

http://www.essentracomponents.co.uk/mss/mss-pc.nsf/WebEngine?OpenAgent&cmd=category&category=MVED-97LTMM-69538&catalog=MEX-EN

Fit like this:

Al then pushed them in with a vice to keep them square

We then drilled the tubes to take the spider (I used astrosystems for these: http://astrosystems.biz/sechold.htm

and then screwed it all up.

Focus board and telrad board added and then the focuser hole drilled and fitted

I went with a moolight CR2 http://www.firstlightoptics.com/moonlite-focusers/moonlite-cr-dual-rate-tri-knob-crayford-focuser-for-newtonians.html

I have to say it is beautifully engineered (lovely smooth action). 

Final job on the top cage today was to glue the truss brackets in place. Again astrosystems for these brackets: http://astrosystems.biz/utlltl.htm

[Scott]

Another good day today, starting to take shape.

Looking good Simon, How's it looking for Hersty? There'll be a queue for looky's. £5 a go and you'll pay for that mirror in no time  .

[SimonfromSussex]

Cheers Scott, sadly I don't think we will be there by Friday................

[SimonfromSussex]

Then this afternoon we made the side bearings

First to router a circle from the pre-cut & glued (double thickness) square

Then to loose some weight we cut out some center sections

The finished bearings (subject to a bit of cleaning)

Just gotta knock up a couple of boxes for the bottom tomorrow Al and we are done right?????? 

[Daniel-K]

si are you not using the sips @F3.38  it could get messy ?

[SimonfromSussex]

I don't want to loose focal length Dan (which I think a sips would change) so I have baader coma correctors permanently screwed to my wide field eyepieces.

[Daniel-K]

I don't want to loose focal length Dan (which I think a sips would change) so I have baader coma correctors permanently screwed to my wide field eyepieces.

how do you find that works si? im still undecided if I should get the sips and just get a moonlite and have the same option as you. I only have 2 WF EP'S and would save me a fair few quid. plus in the 14" ATM its not bad at all at f4.5 and my 16" is going to be the same f4.5