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RE: [APML] TMB 115/805 - which focuser to choose



Hi Radek
 
If you get the CNC tube with the 3" focuser, you'll be able to use the standard TMB/APM medium format Field Flattener.  If you get the FF with a Pentax 67 camera mount - be sure it's the Japanese manufacture version - it should allow you to mount almost any 35mm or CCD camera using standard thread-on Borg components available from Hutech in the USA.  This option would give you the greatest flexibility in mounting cameras of any type, and the nice thing about the Borg adapters is that they preserve the correct FF-to-film plane spacing.  I suspect that the FeatherTouch focuser is actually a better unit (I haven't tried one, but hear they are excellent), but unless you can be sure that a Field Flattener is available to fit it, you may have problems with image quality shooting at prime focus without a FF.  It may also be possible to get a reducer for the TMB115, but certainly if you get the TMB/APM FF, there are Borg components to mate a 2" accessory like the TeleVue reducer.
 
Unfortunately, there are a couple of different APM Pentax 67 camera mounts around.  The Japanese manufactured versions I have for my TMB152 and TMB105 both accept the Borg adapters for 35mm, and I'm certain that Ted Ishikawa at Hutech has something to fit any 2" or C-mount accessory as well.  It will be important to determine what version you are getting before you buy.  Good luck, and good shooting.  I think that with a FF, that 115 will be an excellent astrophotography instrument.

Jon Kolb
Adventures in Astrophotography
http://home.datawest.net
jkolb@datawest.net
Life Member, International Dark Sky Association

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