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09-08-2012, 06:02 PM   #1
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Where to get 48mm Pentax T-ring?

I'm looking for a wide T-ring adapter for my K-5 that has 48mm threads (instead of conventional 42mm) and I can't find one. There somewhat easy to find for Canikon cameras but not for Pentax. Anyone have an idea where I could get one? I've looked everywhere.

If I can't find one for a Pentax do you think a Nikon might fit?

09-08-2012, 08:28 PM   #2
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The T-mount is, by definition, 42mm x 0.75 tpmm. Anything else is not a t-ring.

Why do you need 48mm? I've never seen a lens with a 48mm threaded mount.
09-08-2012, 10:56 PM   #3
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TopherTheME does not want T-mount, he/she wants T-ring, I believe it is for the telescopes.
possibly there:
CAMERA ADAPTERS for TELESCOPES & MICROSCOPES!
CAMERA ADAPTERS for TELESCOPES & MICROSCOPES!
T-Mount 48mm Ring Mounts | Edmund Optics
Don't you need a FF camera for those activities?
see at that:
A wide T-ring converts a SLR or DSLR camera mount to a wide-format T-thread. This wide (48mm) T-ring supports full 35mm format cameras. A wide format T-ring is needed for astrophotographic applications using a Canon DSLR or SLR camera and a focal-reducer / corrector lens. This larger than standard size, wide 48mm diameter T-ring supports full 35mm format Canon cameras. Not compatible with standard T-threaded accessories. Couples camera body to wide, 48mm T-threads on Focal Reducers for Orion ED80 and ED100 refractor telescopes. Compatible with wide format 48mm T-threaded accessories only. Not compatible with standard (42mm) T-threaded camera adapters.
Nikon F pre AI mount usually will mount on Pentax K , sometimes might need small trimming
09-09-2012, 04:24 AM   #4
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I was wondering if the 48mm is more standard as 2" adapter?

09-09-2012, 07:21 AM   #5
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I wonder if this M48 to T2 adapter would do the trick. The limiting ID is still the K-mount and as long as you have sufficient in-travel in the focuser, the extra 3.5mm thickness should not present an issue.
Teleskop Service M48 to T2 Adapter - Male to Male Thread - OPT Telescopes

Last edited by Ex Finn.; 09-09-2012 at 07:33 AM.
03-01-2017, 05:31 AM   #6
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QuoteOriginally posted by TopherTheME Quote
I'm looking for a wide T-ring adapter for my K-5 that has 48mm threads (instead of conventional 42mm) and I can't find one. There somewhat easy to find for Canikon cameras but not for Pentax. Anyone have an idea where I could get one? I've looked everywhere.

If I can't find one for a Pentax do you think a Nikon might fit?
Awakening this old thread since i just ran into the same problem. Did anyone find a solution to this. M48-T2 adapter is not an option, i want to avoid any bottlenecks.
03-16-2017, 09:06 PM   #7
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QuoteOriginally posted by Lage Quote
Awakening this old thread since i just ran into the same problem. Did anyone find a solution to this. M48-T2 adapter is not an option, i want to avoid any bottlenecks.
I was searching for something similar and found this thread. I don't need M48, just some way to interface my K-1 to a telescope without vignetting. A typical t-ring blocks the corners of the full frame sensor. Some leads for you:

They don't mention what threads this product uses, but definitely wider than a standard t-ring. Maybe send them an email. Takahashi Wide Mount Pentax-K T-Ring - Buy Telescopes

This one combines the usual t-ring and 2" adapter, and is my top choice at the moment. 2" UltraWide True-2 Prime Focus Adapter - Telescope Camera Adapters | TelescopeAdapters.com

They also sell just the wide ring but I don't see it for Pentax Wide (48mm) Format T-Rings - Telescope Camera Adapters | TelescopeAdapters.com
09-02-2018, 01:09 PM   #8
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I also urgently need a Pentax K bajonet with a female 48mm (2“) thread on the tel scope side to connect my flattener-reducer (male thread 48mm) with the camera and hold in the short distance of 55 mm between the reducer and the sensor.

Is it possible that this connection does not exist anywhere on earth?


Last edited by Pete_XL; 09-02-2018 at 01:23 PM.
09-02-2018, 08:24 PM   #9
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QuoteOriginally posted by Pete_XL Quote
I also urgently need a Pentax K bajonet with a female 48mm (2“) thread on the tel scope side to connect my flattener-reducer (male thread 48mm) with the camera and hold in the short distance of 55 mm between the reducer and the sensor.

Is it possible that this connection does not exist anywhere on earth?
Nowhere that I could find. I built my own from parts I cobbled together and machined, using only my drill press and files. I recall using the insert from a Nikon M48 version (easily found) and the Pentax K end of a Pentax K to 2" tube adapter (for inserting into a 2" focuser), I think from Scopestuff. The Pentax K part of the Pentax K to 2" tube adapter was removed (leaving the male T2 adapter part on the 2" tube), and its female T2 adapter was removed with the 3 screws on the outside edge. The insert from the Nikon adapter was turned down, with a new V-groove, to fit into the remaining part of the Pentax K piece that held the female T2 adapter. So now the Pentax K part has the M48 female adapter.

The hardest part was building the attachment of the female M48 ring to the drill press. I used an M48 filter ring with an epoxied-in round plate, and added a centered hole to chuck it into a mandrel to attach to the drill press. I screwed on the female M48 ring, and filed the outer edge to match the outer edge of the female T2 adapter that was removed.

This fits perfectly onto my SkyWatcher Esprit 80 400mm f5 telescope, with its M48-threaded field flattener, and maintains parallel alignment with the sensor plane.

A hack job, but it works.
09-30-2018, 07:38 AM   #10
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QuoteOriginally posted by i_trax Quote
TopherTheME does not want T-mount, he/she wants T-ring, I believe it is for the telescopes.
possibly there:
CAMERA ADAPTERS for TELESCOPES & MICROSCOPES!
CAMERA ADAPTERS for TELESCOPES & MICROSCOPES!
T-Mount 48mm Ring Mounts | Edmund Optics
Don't you need a FF camera for those activities?
see at that:
A wide T-ring converts a SLR or DSLR camera mount to a wide-format T-thread. This wide (48mm) T-ring supports full 35mm format cameras. A wide format T-ring is needed for astrophotographic applications using a Canon DSLR or SLR camera and a focal-reducer / corrector lens. This larger than standard size, wide 48mm diameter T-ring supports full 35mm format Canon cameras. Not compatible with standard T-threaded accessories. Couples camera body to wide, 48mm T-threads on Focal Reducers for Orion ED80 and ED100 refractor telescopes. Compatible with wide format 48mm T-threaded accessories only. Not compatible with standard (42mm) T-threaded camera adapters.
Nikon F pre AI mount usually will mount on Pentax K , sometimes might need small trimming
Hello

You are absolutely wright. I had this problem with my K1 and a 42 mm T Ring. It does not cover the FF sensor and create a intense vignetting efect with or without a focal reducer. An M48 is needed.
Regards
10-09-2018, 07:26 AM   #11
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I bought this male M42 to female M48 adapter: Opticstar M42(M) to M48(F) Adapter.
Fits the Pentax K to T adapter nicely.
Now I just need the field flattener
10-09-2018, 11:24 AM   #12
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QuoteOriginally posted by DrawsACircle Quote
I bought this male M42 to female M48 adapter: Opticstar M42(M) to M48(F) Adapter.
Fits the Pentax K to T adapter nicely.
Now I just need the field flattener
What is the minimal distance from sensor to flattener you can reach with that adapter combination?
I need 55 mm distance and I will have my T adapter drilled wider to directly insert a M48 ring there. This is the only chanceI see for my setup to stay near the 10 mm that remain from the camera flange to the flattener.
10-09-2018, 11:52 AM   #13
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The adapter adds approximately 1 mm to the PK to T adapter (Teleskop-Express: TS Optics T2 Ring f)
PK to T adpater flange is 9,3mm thick, so approx. 10,3mm between the camera housing and the flattener.
10-09-2018, 12:15 PM   #14
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QuoteOriginally posted by DrawsACircle Quote
The adapter adds approximately 1 mm to the PK to T adapter (Teleskop-Express: TS Optics T2 Ring f)
PK to T adpater flange is 9,3mm thick, so approx. 10,3mm between the camera housing and the flattener.
Thank you for the information. So I would end up with 45.46 + 10.30 = 55.76 mm. Thats not too far away from my goal!!!
10-09-2018, 12:40 PM   #15
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I’ll just remove the 0,3-0,5mm on the PK->T adapter using a metal turning lathe (we have one at work).
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