Pentax mount

Chromed (Greg) · #1 10-03-2009, 12:00 AM

Hey guys.
My father recently acquired a Pentax K20D so I've decided that I'm going to hook it up to my 12" Dobzilla and take pictures of the moon and planets (can't do more.... for now). However, I'm having a slight problem.
On bintel they have two Pentax T-rings. One is described as "T-Ring Pentax K" (here) and the other as "T-Ring Pentax Screw" (here).

Is there any difference between them?
Thanks in advance

MrB (Simon) · #2 10-03-2009, 12:06 AM

I think the screw is for the old M42 screw mount bodies like Spotmatics etc(and used by a few other brands a while back)
The 'K' is a bayonet fitting, first used on the K1000 body, but not sure if it's still the same bayonet they use today though?

kinetic (Steve) · #3 10-03-2009, 12:06 AM

Quote:

Originally Posted by Chromed

Hey guys.
My father recently acquired a Pentax K20D so I've decided that I'm going to hook it up to my 12" Dobzilla and take pictures of the moon and planets (can't do more.... for now). However, I'm having a slight problem.
On bintel they have two Pentax T-rings. One is described as "T-Ring Pentax K" (here) and the other as "T-Ring Pentax Screw" (here).

Is there any difference between them?
Thanks in advance

Yes! a big difference.

Pentax screw is fairly old and is just that- a screw or thread way
of attaching lenses.

The newer K type mount is a bayonet or 'insert and turn a bit' type connection.
All newer Pentax (or third party add-on lenses like Sigma made for Pentax)
have the K type adaptor.

I recently bought the Bintel K adaptor for my Pentax camera.
At only 35 scobes it's a good buy

Steve

Chromed (Greg) · #4 10-03-2009, 12:38 AM

Knew it would be a good idea to check

Thanks a heap

space oddity · #5 10-03-2009, 09:12 PM

Having owned numerous Pentax cameras over the decades and a K10D (the model down from your's) I can tell you categorically that you need the PK adaptor. The M42 will only be useable if you get a PK to Pentax screw thread adaptor. Do note, the M42 adaptor could be used on almost any camera with an adaptor, but better to have the single T mount adaptor to keep things simple and less chance of the wobbles. Happy snapping

Chromed (Greg) · #6 13-03-2009, 04:49 PM

Hmm
Can anyone tell me where I can come by a T mount adapter?
I'm having a little trouble, my search skills must suck today

erick (Eric) · #7 13-03-2009, 04:55 PM

www.bintelshop.com.au and search "T-ring Pentax K"

Chromed (Greg) · #8 13-03-2009, 05:05 PM

I got the ring today, but I just worked out that I truely do need an adapter to put the ring into my telescope

Will this one be fine? Or am I confusing myself somewhere along the line?
Link

erick (Eric) · #9 14-03-2009, 11:11 AM

If you can afford one of these from Hotech, you will be very happy:-

http://www.hotechusa.com/SCA%20T-Adapter.html

From Bintel, I think this is the one you need. Search "Bintel Camera Adapter 2" " on their site - $39.

"This adapter slips straight into 2" focusers providing a t-thread for attaching photographic or imaging equipment.

Minimises vignetting by providing the widest clear aperture possible using t-thread connectors.

Safety cut away on barrel to prevent equipment slipping out.

Threaded to accept 2" filters like IR-UV blocking or Deep Sky filters.

Also adds minimum back focus requiring only 6mm! "

kinetic (Steve) · #10 14-03-2009, 11:12 AM

Quote:

Originally Posted by Chromed

I got the ring today, but I just worked out that I truely do need an adapter to put the ring into my telescope

Will this one be fine? Or am I confusing myself somewhere along the line?
Link

NO! that looks like a camera adaptor for LX telescopes only.

Sorry, I should have realised from your original post that
you wanted to connect it to your 'Dobzilla'.

Assuming you have a 2"/1.25" focuser on the Dob, what you needed
was not only the Pentax K adaptor with T mount thread (what you bought),
but also a camera adaptor for the Dob focuser.
Pic of one attached.
This assumes your Dob focuser can take both 2" and 1.25" eyepieces.

NOW for the bad news.....your Dob will probably not come to focus
because the camera's 'film plane' (CCD) is too far out from the
focuser.
Most Dob owners find this out the hard way once they've gone and
bought 'all the bits'.

There are a few possible solutions to bring the 'cone of light' coming out through your focuser further out so it can reach your camera's CCD.
One is to chop approximately 50mm off the bottom end of your Dob tube!
I know this sounds extreme, but I did it, and many others have.
(I'm not sure how feasible it is for a Truss Dob though, mine is an
enclosed single tube DOB.)

Another way is to move the mirror up the tube by using the collimation
adjustment screws.

Another way again is to buy a 'low profile focuser'.
These can get your camera a fraction closer but it's not usually
enough.

Here is an explanation by IIS member Alchemy about the 50mm chop
solution:
http://www.iceinspace.com.au/63-441-0-0-1-0.html

BTW the chop solution doesn't prevent you from going back to
purely visual use of your scope with eyepieces.
You can still reach focus by using 50mm extension tubes in the focuser.

I know all of this sounds like a huge hassle, and nobody is made aware of it when they buy big DOBs! We usually find out years later when we
want to stick our cameras on them

Steve