Making an eyepiece extension

[dikman]

I have Celestron 102 SLT that will only achieve eyepiece focus by using a diagonal, so I figured I need an eyepiece extension tube. I was going to buy one but then thought "why not make one?". Not having any aluminium, tube or solid, to fit a 2" focuser, I fired up the foundry, melted some aluminium and cast an oversize cylinder. Lots of machining later and I had a functional extension tube (and a small bucket of aluminium turnings!).

I was going to anodize it but there are quite a few impurity imperfections, which I used filler on, so painted it instead. I didn't want to machine it too thin so there is a little bit of weight to it but nothing that will cause any problems. It works well, but because the length was a guess on my part it can probably be shortened by maybe 30 - 40mm. Maybe one day, it should be easy as all the hard work has been done.

[Tinderboxsky]

Great little project. It has come up well.

I too, find these small projects to create one’s own accessories very satisfying.

Thanks for sharing.

[oska]

Nice one Richard. Casting anything gets two thumbs up from me ;)

[dikman]

Thanks fellas, it's hard to get anywhere near precise castings using sand moulds so I just make things oversize and allow for lots of machining!:lol:

Aluminium is relatively easy, I've tinkered with brass too but that takes a LOT more heat!

[bojan]

Great project!
But sometimes, for not too demanding parts it is easier and quite OK to use 3D printed parts..

Some time ago I made EOS adapter for my C11 (https://www.iceinspace.com.au/forum/showpost.php?p=1558746&postcount=28), it was printed slightly larger, then machined to dimension. For threads (M42x1 mm) I used M39-M42 adapters (https://www.ebay.com.au/itm/314122204598?hash=item49232475b6:g: 9hsAAOSwrO5iu8fz&amdata=enc%3AAQAHAAAA0DIdUnvdxZenHh 2qftXdgT3JTYrRKp6iZs1eqHri9vAf5xNT7 qvwW16jH77U3GjhbY%2BuWkp9xSeWqQE9Dj f4Jo7mhtJg2JPQmJOn3Ynr%2B7sJ53%2B4r 1HBkO3M%2BThWFqNwLHIT9zyx1ZJypLFEF9 dPgHvR1bgpxOqT7ZfCwYoMSr2X2cG4%2FiF Kng0X%2BMB%2BIdj3aANhXSk2GuuCxAK%2F wQIYIs%2FuxQbKowK10ytgCMAlw0OQHAdPr SskXfpgqkW7HrptCHyomev2nG%2FqpjbzX2 BON7w%3D%7Ctkp%3ABk9SR6y8kZv3YA) from ebay, glued in place. They were ~2$~8$.. still cheap enough so no need to bother with machining.

[dikman]

Good point, bojan, and you're right, a 3D printed piece would be more than adequate for supporting an eyepiece. Unfortunately (for me) while I have made several attempts to learn to design things for 3D printing I haven't persevered with it. I'm not sure why that is.:shrug:

While it's a lot more work doing it my way it's a method that I don't have any problems with.