Quote:The PEC on the CGEM can not take out the infamous 8/3 error as it is non integer. Either a 3 worm rotation PEC would have to be instituted (not a 3 rotation average) or new motors. For some mounts the non integer componet is larger than the first harmonic.
"Starman" Dan Doyle
Texas Astronomical Society of Dallas
Central Texas Astronomical Society
8" LX200GPS w/ST80 guidescope, Canon 350D+DSI Pro
150mm f/8 Sky Watcher Refractor
10" f/4.5 Homemade Dob RV-6 Criterion Dynascope http://www.darcstarobservatory.webs.com
Quote:Adding a 3-cycle sensor isn't something I can think of doing elegantly.. there's not a lot of space inside the mount.
I lost count of my scopes. Now I just want mobility. I came, I saw, I bought some interesting accessories, and put names to faces: NEAF 2012, ASAE 2012, SWAP 2013, ASAE 2013.
Quote:The goal here isn't just to overcome the 8/3 resonance-
Quote: it cannot be done with a bolt-on, because the internal motor encoder on the Celestron is already used by the Nexstar hand controller
Quote:For about the same price I can buy a new Heidenhain encoder and get to have some fun developing something while it's cloudy
PeteGallery: http://www.astrobin.com/users/pmumbower/CGE Pro | modded C9.25 | 8" f/4 newtSBIG ST-2000XM, CFW-9 Astronomik type2c LRGB, Baader 7nm HaQHY5L-II mono, PEMPro2, Sequence Generator Pro, PixInsight, RegiStar
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Quote:1) read the switch to determine EQ North / EQ South operation
Quote:3) read the switch to reverse RA guiding (in case of an ST-4 port that is wired in reverse)
Quote:The ceramic resonator @ 100ppm would drift by about 130" in a sidereal day, or about 2" in 20 minutes.A normal crystal oscillator @ 20ppm would drift by 1" in 60 minutes.
Quote:But one way to sidestep the cosine term issue is to NOT believe the encoder when the cosine term is small. That would mean at worst 5 seconds when we are blind. The encoder has a slot period of 17 seconds.
Quote:Quote:But one way to sidestep the cosine term issue is to NOT believe the encoder when the cosine term is small. That would mean at worst 5 seconds when we are blind. The encoder has a slot period of 17 seconds.What I did for dome azimuth determination using a magnetic sensor was use Atan(Sin/Cos) when Cos was greater than Sin and 90 - Atan(Cos/Sin) when Sin was greater.Chris