Transforming the Canon FD 300mm f2.8L into a telegraph with autofocus via JMI NGF-CM plus a ZWO EAF

The first attempt does not work out well, since it's difficult to print the 77mm thread.  

I have tuned the printing parameters for several times but it didn't help much.

Therefore, I design another adapter from ground zero again.  I found the original 77mm ring for the FD mounting mechanism could be reused and here's the prototype:

Some fitting issues, and I did the fitting with a cutter.

It looks great, with the NGF-CM fitted.

The whole model was refined and printed again.  I will use black PETG in the final version and add felt lined black sticked inside.

Three generation of equipments combined: Canon FD lens, JMI focuser and ZWO EAF.

I am so excited, and I hope I can try it out soon.

--

Prototypes

Those thinner rings were the attempts of printing 77mm threads.

The bigger blue adapter was the first prototype of the redesigned adapter without the need of 77mm threads.

Summary: 3D printing could not be too precise, they are plastic afterall.  Expansion and contraction, annealing is apparently an issue.  They are pretty strong but to maintain accurate precision and collimation, you will need to redesign the whole thing.  Don't even try to push its precision or strength, try to avoid these.

--

20260409 Additional Notes

Set the limit of focuser travel of the NGF-CM with ZWO EAF in my ASIAir last night.

Set the focuser position to the middle of the travel.

Confirmed that it could reach infinity focus with ample of rooms for adjustment, even without touching the NGF-CM.  So autofocus should work, but to be verified with the stars.

20260406 M102 et al

Continue my Messier Marathon with suboptimal sky.

Started at 9:23pm, summer time marks the beginning of less imaging time.

First up is M102, 28 minutes of exposure:

Next up is M105 with M95 and M96 (mosaic), will do at least one hour of exposure, finally 65 minutes of exposure:

Below will be left for the next time: M103, M85, M64.

Also setup my Canon 200mm f2.8 with guiding Markarian's Chain, containing M84, M86, and surrounding objects, etc.  

No polar alignment was done, just very rough focusing since my ipad air was dead.  Not really easy to do all these with a small mobile screen.  

Try to stack 30s exposures like the S30 therefore.

Very poor result.

Second attempt, reduce exposure to 10s and then stack.

20260405 M109 and Messier Marathon

The quest continue...

Started at 21:42 rather late but it cleared up a bit after the storm dave.

I will send the whole observation session with it, maybe around 45 minutes.  A promising target which deserves better treatment.

Finally, 1:7:30.

20260329 Clear with showers, occassional stormy

Started at around 9:33p (summer time started)

First target is M44 which is pretty close to the moon, but open clusters should be fine.  

6.5 minutes exposure

M63 for 12.5 minutes

M94 for 16 minutes:

M3 for 18 minutes.

Stopped eventually due to shower.

20260328 Messier marathon session three: thin Cloud Observation

Start at around 9:50pm.

M101 is the first target, I have very limited time tonight but I don't want to rush like the last time.  So I am spending more time on this target, 47.5 minutes.

M106 is the next and the last target, see if 10-15 minutes would be good enough.  Stopped at 13 minutes, time to sleep, there's one less hour tonight due to switching to summer time.

20260327 Messier marathon session two: clear Skies with sudden rains

I still too the plunge to continue my Messier marathon.

The first target is M45 before it's sinking too low, I expect to spend 20 minutes with it for a 1.3x mosaic.  Starting from around 20:40. 

It refuses to perform AI denoise at 20 minutes, saying that the mosaic is incomplete.  I shall wait a little bit longer, maybe until 25 minutes.  So sad further exposure ruined the stacked image, I didn't save any individual and so it's really less than useable.  Just a record, 25 minutes wasted.

Broken M45 mosaic:

I hope to do one more two more objects before closing.

M100 is the next one, really low.  Let me do 8 minutes or so.

And then M98 with M99 before they sink too low (also with NGC 4208 plus NGC 4237), let me do around 8 minutes or so.

Then M67 for 5 minutes.

Finally M65 + M66 and also NGC 3628 before it snows (forecast), so for 30 minutes.   Got only 13 minutes before cloud rolling in.

Not a bad night, the forecast was bad but I got a handful of targets done.

Canon FD 300mm f2.8L second generation

With my new 3D printer, and the help of my daughter who is keen on making 3D models, this project is realised so quickly and it's a BIG success.

It was pessimistic about the thread (77mm 0.75 tpi) but it turns out to be nearly perfect.

It can reach infinity focus with some rooms.  So now this little lens could do autofocusing with asiair!

Aside from using an eyepiece, I also use 533mc pro to test.  It works without problem.

Other than the above adapter, I will be making two more:

a. 2" nosepiece in order to be used with my 85mm refractor for fine focusing

b. SCT female thread in order to be used with my SCT

I can then sell that CYCK focuser.

--

I have removed the ebay ad of my Canon 300mm, will be keeping it and making good use of it.

I have ordered black PETG carbon fibre filaments to print a strong adapter.  My daughter has modified the adapter to have more threads on more secure connection to the lens.

--

Later I found that the thread is less than perfect so that it's not screwed all the way in and thus leaving the gap.  It is probably not strong enough.  But the good news is that, if the quality of the thread improves, I will get even more room for focusing.

Time to do some fine tuning.

--

I have printed a new version with PETG, stronger apparantly.  But yet, the thread is less than perfect.  I will need to do some more experiments.  

I have printed another ring only to save filament and time.  But then it still less than perfection.  

JMI NGF-CM with ZWO EAF

Since the JMII NGF-CM is lower profile, I want to see if it could be used with the Canon FD 300mm f2.8L.

It might be able to replace the CYCK focuser entirely, to use with my Ranger like now, to use with my 8" SCT, and to use with my 85mm refractor for deep sky imaging.

The first feasibility test was to attach the ZWO EAF to the JMI focuser, to replace the existing JMI mini DC motor.

Original JMI mini DC motor removed.

Replace the coupler on the focuser shaft.  It was for the DRO controller which I had sold.  Now it's attached to a coupler bundled with the ZWO EAF.

Next step is to attach the focusing motor, and I have proper screws on hand fortunately.

The next test would be to try it out on the Canon FD 300mm f2.8L to see if it could reach infinity focus.  If that could be done, I am going to keep the lens.  I now had it posted on ebay but so far no one really placed a bid yet.

I did a handheld test and it works with a 20mm eyepiece.  Since the 533mc could take a 2" nosepiece, and thus saving 1cm from the 2" to 1.25" adapter!  This makes even more room for reaching infinity focus.

Specification of the adapter: everything like my existing Ranger adapter, except it's with 77mm female thread instead of 76mm.

The project looks quite promising.

I will certainly keep my Canon FD 300mm f2.8L if that could be done.  I will then be able to have autofocusing with this lens!  My 533mc has a relatively small sensor which works pretty well with this ancient lens.

Next step is to make a SCT adapter for the JMI-CM, and then a 2" nosepiece.  The CYCK focuser could then be sold!

--

I believe one with a 2" nosepiece would be good enough.  

I have a 2" adapter on my SCT so it's good enough.

I can put the whole thing into the focuser of my 85mm refractor too.