T-Ring Pentax-K to T-2i

The hight of the ring must be slightly shorter. In case of temperature drift or mechanical tolerances you need some focus travel left to be able to compensate. Therefore most photo lenses are "over shooting" the hard stop for infinity.

Unfortunately this T-Ring is not designed to hold a filter. But you can connect the T-Ring with a 2" nosepiese http://www.baader-planetarium.com/en/accessories/adapters-imaging-accessories/astro-t2-system/baader-2%22--t-2-nose-piece-and-camera-adapter-%28same-as-used-by-sbig%29-%28t-2-part-16%29.html wich has a 48mm filter thread

The Pentax K indeed has got a flange focal distance of ~45mm - but this in fact is the distance from the (bayonet) lens flange at the front end of the camera body itself to the sensor inside the camera. If you use a PENTAX T-2- T-ring-adapter (for instance our item # 2408302), you gain the exact additional distance to produce the required distance of 55mm with your PENTAX camera body. 55 mm is a well established industry standard for DSLR-T-2 rings (dating back to the days of SLR-emulsion films). Accordingly the T-2-rings matching different DSLR-cameras have got different heights. This is to provide a standard lens distance for any DSLR camera body, so that also third party lenses (Tamron, Soligor a.o.) can be used on any DSLR camera. This is the reason why the MPCC had been designed for the 55 mm focus distance. Today the standard has "softened" somehow with the advent of mirrorless 4/3 cameras and many other imaging tools that continue to replace DSLR-cameras these days. It is the reason why we have been designing a multitude of other variable length adapters like the "Vari-Lock-system". Also many modern telescopes do require larger light cone throughput than the T-2 standard can supply. For this reason the latest design of the MPCC even can unthread the T-2 male thread and be attached with the outer M48 thread supplied at the camera-end of the MPCC. However, finding the right parts for producing the correct sensor-distance is somewhat trickier than using the well established T-2 standard.