Zwo ASI585mc > Takumar 200mm F/4

[brenski]

Looking to see if it's possible to connect a Zwo ASI585mc to a Takumar 200mm F/4 (M42 thread)

At present I've used a combination of the various connectors I have and infinity is nowhere near correct. Looks like a backfocus issue.

Has anybody done this successfully using the 2" ring connector?
if so, what connector/spacer did you use? how did you do it

[Elp]

It should be possible. With the Takumars you generally have to adjust the infinity stop on the lens (unscrew the three retaining screws around the circumference of the focus ring, move the focus ring around a fraction when it's moving in a free state, then put the three screws back in). This is required as it doesn't focus R G and B at the same point (only the red and green are the most visually see-able), you'll notice this when trying to find focus, one side the stars will have red halo bloat, on the other side of focus green halo bloat. By doing the infinity focus adjustment you can go into the green and dial the focus back, otherwise the stars will always have a red bloat.

[Elp]

I've also found with the 200mm it needs to be stopped down to f5.6, maybe more.

[brenski]

cheers

[Ratlet]

@Elp has pretty much covered everything.

I use mine with a m42-canon adapter then canonzwo filter drawer which gives the correct spacing, however still needed to adjust infinity.  It's not massively uncommon on a lot of older lenses for infinity to be out, but fortunately the takumar 200mm is super easy to adjust.

Stopped down it's an excellent performer.

 

[michael8554]

Hi brenski

Any lens will infinity-focus before the infinity mark, without modification, if you have the spacing less (or more, I can never remember) than the Flange Distance.

Which is 45.46mm for a M42 x 1 threaded Pentax lens.

Michael