DFM Engineering, Inc.
was founded in 1979 by Dr. Frank Melsheimer. Dr. Melsheimer is a highly recognized authority in telescope design and manufacturing.
16"~50" ( 0.4m~1.3m) Standard Cassegrain Telescopes.
http://www.dfmengineering.com/company_history.html
http://www.hkastroforum.net/viewtopic.php?t=862
-------------------------------------------------------------------------
Equatorial Fork Mount
The DFM equatorial fork mount offers a number of advantages.
It's versatile: use it visually, with instruments or remotely.
It provides significantly more instrument clearance than is available with horseshoe telescope mounts.
And there are giant advantages over ALT/AZ and German equatorial mounts.
• Easier to guide because there is no field rotation as with ALT/AZ mount
• Tracks objects through the zenith where there are fewer atmospheric disturbances (ALT/AZ has a singularity at the zenith)
• Lower cost that ALT/AZ mounts
• Compact shape and very smooth drive make it user-friendly
• Space efficient - more versatile in the same space as ALT/AZ or German mounts
• Minimum Eye Piece sweep for more convenient viewing than with German equatorial mounts
• Less counterweight required than with German equatorial mounts
-----------------------------------------------------------------------
CCT-20 and CCT-24
STANDARD OPTICS:
• Our typical 0.5M & 0.6M Classical Cassegrains have an F/3 primary mirror with an effective ratio between F/8 and F/18. The 125mm field is fully shielded and unvignetted.
• Back focus is 28cm from mounting surface
• 2 variable, low voltage power outlets for reticles provided on optical tube assembly
• 2 AC power outlets on optical tube assembly
• Finderscope: 5 in. F/9 with 2 in. dia, 32mm focal length eyepiece and projection reticle
TELESCOPE MOUNT:
• 30 in. diameter friction drive in RA and 28 in. diameter friction drive in DEC
• Steel mirror cell with multiple 12-bolt patterns per KPNO standard
• Tracking accuracy: +/- 0.5 arc seconds in 5 minutes, +/- 5.0 arc seconds in 1 hour
• Pointing accuracy (with refraction and alignment correction) better than 30 arc seconds RMS
• Variable set, guide and tracking rates: 0 to 4 deg./sec.
• Supports 65kg instrument load with CG 36cm behind mounting surface
Telescope Control Systems
The DFM Engineering Telescope Control System (TCS), provides a user-friendly interface to the telescope.
Utilizing an IBM compatible computer with multiple displays and a keyboard, you have continual position display, status reporting, and an easy-to-use, menu-driven command set.
Our pointing model corrects for precession, nutation, aberration, atmospheric refraction, mount misalignments and flexure.
Typically, the DFM Engineering TCS and pointing model will achieve 10 to 20 arc- second blind pointing to a 60° zenith distance.
Computer operation is simple. A total of 28 commands are divided into four submenus: initialization, movement, rates and miscellaneous.
All commands are available to your external computer, allowing you to create your own custom user interface.
And the TCS becomes a peripheral to your computer system, allowing integration with your own observing program.