Kevin_A

OK., these are the two grub screw that I found... do I need to remove them? Seems to have some Loctite or something smeared over them.

I did find my set of small German metric wrenches... 2, 1.5, 1.3, 0.9, 0.7.. 1.3mm appears to be the right one. But with the Loctite, it means they don't want you to fool with them?

I think the ball will be part of the parts you took off.

Yeah, I found the ball, but which hole is it supposed to go into? :-)

I think you will need to use the lens spanner down by the glass.

Hmm, that won't allow me to remove the iris and replace with a milled part, though, does it? I need to be able to remove the iris completely.

Interstingly, there is an aperture stop somewhere that is fully circular, when you open the lens up completely to f/2.

Chen

Kevin_A maybe you have to remove a lens group before you get to the iris assembly.

I thought you had gotten to remove the iris completely? Do you remember what you had to remove?

The glass elements are still in there. Time for lunch. This thing can wait for a different day when I am in better mood. Go work on the Sigma 40 base plate first.

Chen

Kevin_A I never got to my iris as mine has electronics and that adds another layer of complexity.

Ouch, I thought you said you got to the iris.

OK, this project is definitely in the backburner now; perhaps buried for good. I will try to put things back to as normal as I can, and see if I can still get a working lens, without the aperture click stops (still have no idea where that ball goes into).

I don't like redneck engineering; working with no documentation. Life is too short for that.

Started to work on the Sigma 40 already. I am just going to modify the base plate of the Rokinon, seen here with a 1:1 printout and the Sigma to measure where to move some of the holes, and to figure out if I have the right belts in my stockpile. Perhaps send the design out before the next workweek for the web machine shop to work on it.

Speaking of belts, it really helps using 10mm belts instead of the 6mm astro hobbyists seem to like to use. Everything feels more solid. Well, that extra bearing to hold the EAF shaft definitely does not hurt either.

That Blue Fireball CAA that you see in the photo above, really helps in this case, belt or no belt. That tripod ring does not allow the lens to be rotated.

I am still trying to get used to the Nikon's left-handed bayonet! I keep tightening the bayonet when trying to remove the lens, and wonder why the bayonet does not even budge :-) :-).

I am still on the look out for the Sigma 40 with an EF mount. I don't think a new one exists on this planet anymore.

Chen

Kevin_A

Aha, this is the last plastic ring, with just the stainless bayonet plate removed.

There may be a way to attach a M54 interface to it.

PreciseParts can do a "bolted" version of EFW mounting that converts a flat flange to a M54 tube. An aluminum plate can go on instead of the bayonet plate,and a precise part can be bolted to it. This is one of my PreciseParts "bolted" adapters (to M54); picture from PreciseParts:

But the backfocus is still pretty short though. The EF bayonet plate is 3mm thick. So, about 40mm to 45mm worth of backfocus to play with (not enough backfocus for both a CAA and a filter drawer). But at least we don't have to deal with flakey ZWO camera adapters. I'll look into adapting the Rokinon this way.

Heck -- I should look at the Sigma 40's Nikon bayonet plate to see if I can do a direct M54 connection. The key is going to be how short can PreciseParts make a bolted adapter to M54. I'll do anything to avoid flakey ZWO parts.

Chen