[Okeydokey]

I have a K-m does that mean all K fit, lenses will fit?
I gather some of ye-olde manual lenses are of very good quality and worth hunting down to fit my camera... any opinions that can qualify this?
I'm looking for prime lenses for astrophotography so am about to invest in a 50mm and seperately a 500mm with teleplus x 2 teleconverter.

Many thanks

[Adam]

Yes, manual lenses will mount & work without an adapter. Ready this article for more info on how to actually meter with these lenses:

https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html

[Okeydokey]

Thank you very much, exactly what I needed to know!

[Giklab]

Hold on a sec. Which 500mm lens? (I assume the TC is a Kenko?) For astrophotography you'd be much better off with an actual telescope instead of 'ordinary' lenses.

[Tanzer]

The problem with a lot of old lenses, regardless of mount, is that they are prone to internal fogging and mold. So hunt those lenses down carefully. The marketplace forum here is reliable, compared to craigslist (yikes, you've been warned!) or ebay.

[tibbitts]

I'm not knowledgeable about astro photography, but I believe most people who are use a telescope adapter rather than a traditional lens.

Regarding old lenses in general, despite my on-going gripes about newer Pentax lenses (notably the ultra-wobbly 16-45, and the inconsistent 55-300), in general I think newer lenses are better than older ones, and are generally more convenient to use.

[Okeydokey]

I find it hard to understand why the Pentax M42 adapter ring is so much more expensive than the grey versions, fleabay throws them out at a few pounds (UK), for the grey versions. I now have a 55mm f1.7 Chinon on its way and the jury is out on the 500mm. I have a scope and have always been in two minds about a large low cost, previously owned lens. Thanks for all your advice!

[boriscleto]

I find it hard to understand why the Pentax M42 adapter ring is so much more expensive than the grey versions

https://www.pentaxforums.com/forums/general-technical-troubleshooting/237060-...dapter+problem

https://www.pentaxforums.com/forums/general-technical-troubleshooting/167741-...dapter+problem

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/166996-problem...pter-ring.html

https://www.pentaxforums.com/forums/general-technical-troubleshooting/135940-...dapter+problem

https://www.pentaxforums.com/forums/general-technical-troubleshooting/128957-...dapter+problem

etc, etc, etc...

[rbefly]

Hello Okeydokey, Welcome to the Forum!
The links provided by boriscleto are the tip of the iceberg. If you've never had the nerve-wracking job of trying to remove an inexpensive screw-on adapter from a camera body or lens, I suggest you avoid it.
But that's a lesson many have to learn themselves.
Ron

[Just1MoreDave]

I find it ihard to understand why the Pentax M42 adapter ring is so much more expensive than the grey versions, fleabay throws them out at a few pounds (UK), for the grey versions. I now have a 55mm f1.7 Chinon on its way and the jury is out on the 500mm. I have a scope and have always been in two minds about a large low cost, previously owned lens. Thanks for all your advice!

I have a decent 500mm f8 mirror lens. I think one reason people use telescopes instead of lenses is that the scope already has a tracking mount. I can get some decent shots of the moon but that's pretty bright. Still I have to raise ISO at 500 or using a TC to get 1000mm, just because the moon moves pretty fast across the frame. Faster 500mm lenses are around but not in my price range.

On the adapter, the Pentax one at least shows you how the thing was meant to work. I have some broken cameras and old lenses to test out off-brand adapters, and most of them will work eventually. If you don't want to adjust and file and pray to the lens gods to get the lens off your DSLR, maybe the extra cost is worth it.