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focal length   Focal Ratio Magnification of telescope  in focus CCD  or DSLR arcsec per pixel  FoV online fov calculator online CCD suitability online back focus calculator

The Meade Model 647 CCD Flip-mirror system(2") is a major advancement in systems specifically designed for CCD imaging where large CCD chips are employed. One of the most important aspects of this system is the dramatic reduction in setup and focus time after intial calibration. Threaded on to the rear cell of any Meade LX-series mirror-lens telescope or to other Schmidt-Cassegrain telescope brands, the Flip-miror allows direct visual inspection  of the imaging area, permitting quick and convenient  image composition and focus. The Flip-Mirror may be used with any Meade Pictor CCD Autoguider/Imager or with other CCD imager brands with remove-able lens 35 mm SLR cameras Operations Manual

known as Logic Drive in Celestron astromaster series based on DC servo motor, with a simple analog PWM control circuitry, the speed is controlled by a potentiometer

they are actually based on same principles, that the motor drive rotate tangentially your instrument  along a equatorial plane. the main difference, is the size and weight of instrument you are using. Astrotrac ( and also Fornax )can be described as an miniaturised equatorial platform so that all have same limitations. they have around 2 hours of useful tracking time, and have to reset to zero position first before continue Actually there was a tangent arm drive project started by Manchester Astronomical Society in 1994 which develops very much use the same concept of "screw rod + stepper motor " budget astronomer Reiner Vogel on equatorial platform

astrotrack drive: installation manual from familystar forum: 6V 馬達用的是 42PM48L03(42MP48L?), 在規格上可用電壓 19V/1.27A http://www.motionking.com/Products/PM_Stepper_Motors/42PM_Stepper_Motor.htm 另一種是 12V 馬達之 Pro Mount 再加上 "SynScan EQ3(盒上印刷)" 馬達驅動器 SynScan TM V.3 Firmware Update-able Hand Control New features include ongoing firmware update-ability via the internet, Pointing Accuracy Enhancement (PAE), and capability to store star alignment data. Also can accept new GPS mouse attachment. High precision stepper motors Motor Controller: Microstep driving with auto-power saving feature Resolution: 0.288 arc second Slew Rate: 0.5x, 1x, 8x, 16x, 32x, 64x, 400x, 500x, 600x, 800x Tracking Rate: Sidereal, Lunar, Solar Tracking Mode: R.A. tracking ST-4 type Autoguider Interface: Support 0.25x, 0.5x, 0.75x 1x guiding rate Maximum Payload Capacity: Approx 9kg Power requirement: 11 to 15 V DC 2 Amp (Tip positive) (Power supply n