Your website about your Baader T-ring tells, quote: “Represents the standard exact distance of 55.0mm from the front support surface of the T-ring to the image plane of the camera body forth”
Now, this 55,0mm is longer than the 45,46mm registerdistance from Pentax.
Does the ring still work and let focus?
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.
I also want to use other eyepieces. How do I know the right distance between fieldstop position and the MPCC?
Only if you have a low-profile T-2-ring like #2408318 or if you use the M48-thread, you'll have to use additional spacer rings.
Baader MPCC Mark III - Multi Purpose Newton Coma Corrector
The only coma corrector for Newton telescopes, that neither reduces the focal length nor the image field of your telescope
Large parabolic mirrors are perfectly apt for Deep Sky imaging since they deliver a very large field and enable very short exposure times. However this comes at the price of off axis coma and some residual astigmatism. Coma will distort off axis stars into "comets" which effectively reduces the usable field considerably. Many companys offer various lens systems as solution to counteract coma, most at the downside of increasing the original focal length and reducing the field of view. An f4 optics may become an f4.5
The Multi Purpose Coma Corrector Mark III eliminates coma across the full photographic field without manipulating the focal length. The proprietory lens design has our Phantom Group™ wideband multicoating on all air to glass lens surfaces. This treatment delivers highest transmission combined with lowest amount of scatter and reflections across a very wide spectral range from UV to NIR. The original MPCC had been designed for an f/ratio of f4.5 to f6. The new Mark III however works exceptionally well even down to f3.5. Stars remain pinpoints across the field and the visual use likewise is made much easier - with the help of the 2" (M48) male filter thread at the eyepiece facing side.
The MPCC III is designed to be the most variable coma corrector in the market today. It mounts into every 2" focuser and fits CCD-filter wheels and off axis guiders of various manufacturers.
With the optional T-Spacer (# 245 8405) you will be able to couple the Mark III directly to the Baader Protective Canon DSLR adapter - with or without mounted various filter.
The MPCC MIII Version for either visuell or photographic use contains of the following parts, otherwise see the common description for the MPCC above.
Technical data of MPCC Mark III
- no change in focal length or field size, an f4 Newtonian remains f4.
- newly calculated lens system - designed for an unvignetted field down to f3.5
- maximum sharpness across the field - without center soft spot (as reported of other)
- accepts T-2(M42x0.75) and/or 2"(M48x0.75) threaded photographic- or visual-adapters
- 2" stopping collar removable for increase in backfocus
- For photographic and visual use
- easy to use
- exceptional price/performance ratio
- Phantom Group™ multicoated for maximum transmission and freedom from reflections from UV to NIR
- Optional adapter for direct coupling of the MPCC III directly onto the Baader CANON EOS protective T-ring
- 44mm clear aperture when using the M48(2") filter-tread or the Protective T-ring with optional adapter