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.
You can achieve this easily with the
Baader VariLock 46, lockable T-2 ExtensionTube 29-46mm with spanner tool (T-2 part #25V) #2956946 ( http://www.baader-planetarium.com/en/accessories/adapters-imaging-accessories/astro-t2-system/baader-varilock-46-lockable-t-2-extensiontube-29-46mm-with-spanner-tool-(t-2-part-25v).html )
Please check the camera manual if the back-focus measured from the T-2-thread is 18mm. If it is different, you can use either the Varilock 46 (for 29-46mm) or the VariLock 29 (for 20-29mm).
All regular T-rings (but not the low profile adapters) provide the necessary distance of 55mm, which is an industrial standard.
Do you sell the necessary spacers to do that?
The 12-16mm has to be set to 13,7mm then you get in summary the required 55mm distance from sensore to the MPCC. Actually the
T2 extension rings will obstruct the image because it is a bottle neck but you have to do a crop down to APS-C at the picture anyway.
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.
Baader MPCC Mark III - Multi Purpose Newton Coma Correktor
Coma corrector for Newton telescopes that neither reduces the focal length nor the image field of your telescope
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 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 base-element 2858400A is prepared for use with a DSLR and a standard T-ring, it can be used over the T-2 thread on all standard T-rings. Since the T-thread vignettes with cameras with larger sensors (such as full-format DSLRs), the T-2 thread can be removed. Then an M48 thread is free, and the free aperture increases from 38 to 44 mm. The M48 spacer ring for MPCC III / Protective EOS T-ring can be connected directly to the Protective CANON DSLR T-ring.
This means that you do not only have sharp stars in the entire picture but also illuminate large sensors!
Visual and photographic application
In addition, the MPCC can be used both visually and photographically. The V-1 set # 2454803 contains the necessary adapters for most eyepieces or cameras with a 1.25 "socket - a detailed description can be found in the manual, which can be can be downloaded as a PDF under the tab "Downloads". The basic element of the MPCC can be upgraded at any time for visual use, all necessary parts are also available separately.
Technical data of MPCC Mark III
- no change in focal length or field size, an f4 Newtonian remains f4.
- 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 Coating™ 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
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