First lighted the new equi-dob mount. CCD's M42, M43, M81, M82 and other things. Mostly 5 and 10 second exposures. The mount tracked better than expected. The optics were not cooled down so good focus was not achieved.
M42 2x10 second 20cm 8" Orion DSE EDC-1000 CCD
The mount is made of iron pipe and uses 2 very large bearings. The forks are made of 2 pieces of laminated board screwed and glued together. The fork is bolted to a solid aluminium 12x12 inch plate. Polar alignment is made via a hole up thru the plate and forks. It is easy to acheive good alignment very quickly. The motor is a digital stepper motor and the driver was built using a 555 timer that drives a decade counter set to 4. Its output feeds nand and not gates that then bias the drive transistors. Fairly accurate timing results. The motor drives a worm that drives the main worm gear (1/4 x 20 all-thread). The main worm is clutched by a split ring like piece of PVC that has a mating 1/4x20 piece of all-thread screwed to it. RA tracking is locked by tightening a large radiator clamp around the split ring. The mating of the 1/4x20 worm gear and the 1/4x20 split ring occurs over several "teeth". This may help average out periodic errors. The current setup will track for 8 hours before needing to be reset. Resetting the slip ring clutch takes a minute. Overall, the mount is very stable and tracks real well. It acts just like a dob in "feel" eliminating the problem of acquiring at the zenith.
Left image shows all-thread screwed to the clutch which is locked with a radiator
clamp.
I built the stepper motor controller before I knew there was the SAA1027 chip. I hope to
change my circuitry to the SAA1027 so I can achieve micro-stepping instead of just single-stepping.
It all works well! Other than tracking, the mount actually acts like a Dob when the
clutch is unlocked. It does not have a problem moving to the zenith like a rocker-box
would have due to the equitorial nature of the mount.
