Celestron c70 Project

[happy-kat]

Eyepiece holder now modeled, simplified the design there is no counter sunk entry I don't need it. Have added two holes to the holder 45 degrees apart. The holder is a smidge over 32mm as loser is better than too tight, 32.3mm gives approximately .5mm of play and/or print expansion.

Tomorrow hope to measure and place the two main fixing holes for the base though the concern right now is there won't be enough clearance from the eyepiece holder as I had to make the wall quite thick to take the threaded m3 fittings.

[happy-kat]

Have now done all the measuring so later I plan to model it up, I will start from scratch again as it lets me practice using SketchUp.

[happy-kat]

The Moon was actually visible!

Took the opportunity to retest infinity focus, using the 25mm there were a further 23 turns of the finger to the max distance focus stop past the Moon and from my neighbors house 11 back to the closest focus stop. I have added an additional 6mm to the eyepiece tube this reduced infinity to being 18 from the max focus stop but brought me to about 20 feet for close stuff (original specifications 16ft). If I want any closer I will use an extension tube.

Tried to test with other eyepieces but holding by hand with the lousy 10mm was pretty impossible, but even if not parfocal I think I have easily enough focus turns.

Edited December 23, 2015 by happy-kat

[happy-kat]

Finding it fun and games finding the holes to repair in my model, using solid inspector but it's not showing me where the holes are... Yet

[happy-kat]

Model is now finished and dimensions checked many times.
I have m3 sized brass threaded fixings for printed models to insert into the two holes in the eyepiece turret using a soldering iron tip. The recess also gives the potential of using a thin washer if the overall hole is too generous for the bolt to provide good purchase against the telescope back.
The base has two indented areas to go over the focus wheel fixing screws so that the base will fit flush across the back of the telescope.

[happy-kat]

Not sure if anyone is reading this thread. But I would be grateful if someone who knows about 3d printing could take a look at my model please?

I don't want to get it printed if the model is bad and I don't know enough to know if my model would be an expensive print mistake as I don't have any friends who know anything about this to help. I have put links to skp and the stl files.

https://drive.google.com/open?id=0BzE0JrSB84yceWxpcW9NSkM5Yzg

https://drive.google.com/open?id=0BzE0JrSB84yceWxpcW9NSkM5Yzg

Any help gratefully appreciated.

[happy-kat]

Those files are now replaced with a v7 with a few uneeded lines tidied up.

[happy-kat]

Have now finished and ironed out the model so that there are no errors.

New bits added for strength to the eyepiece turret.

Printing next with 2 days left on my Pro license trial, I wonder if I will lose any of the functions I have been using.

[Ruud]

It certainly looks solid. I hope it works well.

One of the advantages of this adaptation is that you will be able to use a proper star diagonal. I think that the erecting prism in the C70 may be this little telescope's weakest link.

I'll cross my fingers for that functionality you don't want to lose!

[happy-kat]

Thank you for posting.

Already tested my cardboard prototype with an errecting diagonal from my ST80. I have plenty focus travel either way if for any reason my star diagonal is a different light path length which I couldn't test at the time as it was wrapped up for Christmas though it appears a similar length in size. I do have a very compact star diagonal but it is not here.

There is also a glazed (could not decide if glass or plastic) element in the C70 between the inbuilt prism and the eyepiece which is part of the moulded rear piece.

[happy-kat]

Learning new stuff, section pane from underneath is giving me a perfect birds eye view of exactly what I need to trim away. My model from above looks perfect but from inside I have some tidying to do.

Edited January 9, 2016 by happy-kat

[happy-kat]

I have been caught up on other things and need to get back onto finishing the lasts bits so I can get the model actually printed. Currently there are a few problem areas on the model that would spoil printing so I need to fix them first. I think I will save a copy and scale it right up so I can see very closely to try to track down the problems I have on the turret join and the bits inside the model I need to remove that I see in the sectioned view.

[happy-kat]

Now that I have windows 10 64bit on the desktop I can try and sort my model out so I can get it printed. I'm really hoping I won't have to start from scratch again.

[happy-kat]

Still dabbling with this project, working my way through the model getting rid of the internal faces from dragging the side support bars through the turret.

It is a lot easier to use SketchUP now I have a windows 10 64 bit to work on.

Tonight's editing I have gone from 36 internal edge faces down to just 6, this is good progress.

Edited February 16, 2017 by happy-kat

[happy-kat]

Got there Solid Inspector reprots no errors everything is shinny, done it!

[Stub Mandrel]

On 16/02/2017 at 21:56, happy-kat said:

Still dabbling with this project, working my way through the model getting rid of the internal faces from dragging the side support bars through the turret.

It is a lot easier to use SketchUP now I have a windows 10 64 bit to work on.

Tonight's editing I have gone from 36 internal edge faces down to just 6, this is good progress.

Yes that's what you sent, looks right here >PHEW<

[happy-kat]

After my eye watering print quote I have since found a few that will do it for under £15 so I can progress now.

But is it best for this object PLA or ABS and what about microns. Think I'll go for ABS as it will be used outside and 200 as there is no cost uplift..@Stub Mandrel

What does 'FDM printed parts are not solid and are printed with 20% infill by default.' mean in practice, will it make my part weaker then if it were solid inside.

Edited February 21, 2017 by happy-kat

[Stub Mandrel]

Thinner layers mean it takes longer to print, so 100 micron will take twice as long as 200 - hence the extra cost. 200 micron (0.2) is fine for anything where surface finish is unimportant. 0.1mm is a good finish and 0.075 is excellent.

I used 0.1mm for tube rings so they look nicer, but even 0.2mm looks good when done with a decent machine.

15% - 25% infill is usually plenty for strength but if it is likely to be highly stressed go up to 50%, bear in mind most of the strength of most structures is in the outer layers - reduced infill is a big plus for 3D printing.

[happy-kat]

3Dhub order has been submitted, £15.20, waiting on conformation and then hopefully just for the post man.

[happy-kat]

That's it payment sent and now the waiting starts. It will be in ABS white translucent 200 microns. Quite excited to see the fruition of this project and how it might workout on this mini Mak. It's a hobbyiest printing it through the hub but with great feedback so I hope all wiill be well.

[Ruud]

6 minutes ago, happy-kat said:

That's it payment sent and now the waiting starts. It will be in ABS white translucent 200 microns. Quite excited to see the fruition of this project and how it might workout on this mini Mak. It's a hobbyiest printing it through the hub but with great feedback so I hope all wiill be well.

I do hope it works as planned!

[happy-kat]

Cheers :-)

I think I will puit a circle of thin rubber I have from a snapped exercise band between the print and the back of the mak as a diy dust/damp seal it will be better than nothing and thin enough to not effect the join.

[happy-kat]

Going to wait for the new backing before final trimming of the rubber surround. Before that I'll place it in the airing cupboard to make it more pliable as it is resistant to fitting easily all around the tube. Still haven't found the soldering iron needed for the brass fittings.

 

[happy-kat]

Dada

The eye piece fits brilliantly. Really pleased. Brass fittings to add later and a dry run to check holes line up with back of mak.

 

[happy-kat]

I've been thinking after a test construct if it works then in order to spread the load weight as the two bolts are tiny and give tiny purchase area I think I'll use exterior Velcro to attach it. That stuff sticks and meshes very well only I won't have factored in the additional 3mm of thickness.