Altair 183c to Takumar 300mm

[brenski]

Hi

Just wondering if I can link my Takumar lens to the Altair 183c for image capture

♦ Altair 183c > Takumar SMC 300mm F/4 [M42]

1. Can it be done? what adapter is required?
2. What about backfocus?

thanks

[Franklin]

I've got a Carl Zeiss Jena 135mm F/3.5 which has the M42 screw thread fitting and the same camera as you, the T2 on the camera threads straight on (kind of, they're both 42mm but the lens has 1.00mm pitch and the T2 on the camera 0.75mm but they will connect). My lens needs a T2 extension tube of about 30mm to reach infinity focus, your lens may need a different size.

 

Edited October 16, 2023 by Franklin

[brenski]

thanks

[Clarkey]

You can get m42 adaptors for 0.75 to 1.0 pitch. I think I ordered some from fleabay. Also, if you search online you should be able to get the back focus for your lens. If you get a variable adjuster it will give you some wriggle room.

[brenski]

4 minutes ago, Clarkey said:

You can get m42 adaptors for 0.75 to 1.0 pitch. I think I ordered some from fleabay. Also, if you search online you should be able to get the back focus for your lens. If you get a variable adjuster it will give you some wriggle room.

thanks. what is a variable adjuster? is that the depth of the  0.75 to 1.0?

[Franklin]

No it's a variable extension tube that fits between camera and lens.

For example. The distance to chip on the 183c=12.5mm and the back focus on my CZJ 135 is 45.5mm so with my lens I need an extension that is 45.5-12.5=33mm long. Your lens will be different and a variable extension allows different distances to be achieved.

Astro Essentials T2 / M42 Extension Tube Set (4mm, 5mm, 6mm, 7mm, 8mm & 9mm) | First Light Optics

This set would give a number of options along with a M42-T2 mentioned above.

Edited October 17, 2023 by Franklin

[Elp]

Another way of doing it is as you would with your dslr, have an m42 to camera mount ring > zwo lens adaptor > camera m42 female to m42 female ring or additional m42 spacers > camera.

Zwo do various lens adaptors, I've got the two EF canon ones and also a Sony one. It's always useful to have an m42 spacer ring set at hand (and also 0.3-1mm spacer rings) for micro adjustment.

[michael8554]

Astromania M48X0.75 Male/M42X1 Female to M42X0.75 Male Telescope Adapter:

That gets you from the M42x1 of the Takumar to T2 M42x0.75

I don't know how thick that is.

The Takumar Flange Distance is 45.46mm.

The distance to chip on the 183C is 12.5mm.

Leaving 32.96mm to fill with the adapter and T2 spacers.

Now I can't remember which, but if you over or under fill with stock-width spacers, one will allow the lens to go through infinity focus, with best infinity focus just before the mark on the lens.

Michael

 

[brenski]

that's brilliant ^ , thanks 

[Elp]

You may have to do the infinity focus adjustment on the lens so you can focus slightly past infinity (loosen the three screws around the focus barrel, change the barrel position then retighten). You'll know when you've done it as your red star halos will disappear and turn to green as you move past the red and into green focus point whereas before the mod your stars are usually haloed red. I had to do it for my 135 and 200mm.

[brenski]

1 hour ago, Elp said:

You may have to do the infinity focus adjustment on the lens so you can focus slightly past infinity (loosen the three screws around the focus barrel, change the barrel position then retighten). You'll know when you've done it as your red star halos will disappear and turn to green as you move past the red and into green focus point whereas before the mod your stars are usually haloed red. I had to do it for my 135 and 200mm.

thanks, I'm not really confident enough to "not break things". I may have to find someone in the UK who can do this for me - happy to pay to get it done correctly.

[Elp]

It's incredibly simple to do, probably easier than unlocking a door. Here's a video:

https://youtu.be/pawDoE82DQk?si=tv9ELI-SbYPxrFSb

 

Edited October 20, 2023 by Elp

[brenski]

cheers

[alacant]

Hi

Here's one we did by trial and error using an adapter similar to that specified by @michael8554. Since the Takumar 300 doesn't focus by moving internal elements relative to eachother, the spacing isn't critical. So long as you're within about 10mm, you can focus by simply twisting the lens barrel outward to reach infinity. I think the 183 has 17mm bf and the Takumar 45mm, so the adapter + a 20mm ring should get you there.

Note that at infinity,  the old Takumars focus only blue and green, leaving stars with a red halo. Use live stream to get you there, then back away until the red halo just disappears.

Cheers and HTH

Edited October 20, 2023 by alacant
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