Chris Nexstar 8SE; Celestron AVX mount; Hyperion 8-24 mm zoom; Orion 9x50 RACI; Baader Sky Surfer Messier count 110/110 "Though my soul may set in darkness, it will rise in perfect light; I have loved the stars too fondly to be fearful of the night" 51N, 2W My Gallery
Takahashi TSA-120 & Explore Scientific 102mm APO Refractors
Lunt 60mm PT Ha
Celestron Edge 800 & Edge 1100 SCT's
Celestron AVX & CGEM Mount's
Televue Ethos 100* 21mm, 17mm, 13mm, 10mm and 6mm & Explore Scientific 82* 4.7mm Canon Rebel T3i DSLR SBIG STF-8300M, FW5-8300, OAG-8300, ST-Ic guide & planetary camera
Quote:My question. Can one of these new stars be a previously used "calibration star" in the original procedure?
Quote:Check teamcelestron search for "calibration stars".Just a snippet from the thread written by the engineer that codes the HC and MC firmware."That said, the last 4 points in a 2+4 alignment each measure cone error against the "backdrop" of the two star alignment. In that sense, this is really just a 3 point alignment with the last point being an average of 4 measurements. Why would the 4 measurements of the cone error vary? One cause is mount flexure as the OP eluded to. In principle you could use some of the extra data points in the 2+4 to back out the mount flexure terms. The legacy handcontrol did not have the computational prowess, the code space, or even sufficient RAM to do that kind of computation."I wish it worked like T-point also, but it doesn't.
Quote:That reads as an over-simplified description of the method, and I stand by my interpretation - which is consistent with Chris's.Furthermore, it focuses on cone error and ignores dec. index error - which I claim is quite important to get right.I would go further and say that - since the calibration stars cannot distinguish flexure from refraction or whatever - in effect they do help compensate for all those effects - even if they don't explicitly model those terms like t-point does.Frank
Quote: doubt nexstar has dec index error correction because the firmware is the same across all the mounts and the CG-5 AGT for starters has no DEC or RA indexes to check against.
Quote:I disagree with that. I do not think it works that way. Each star contributes information about the error in its part of the sky, and that error is different in different parts of the sky, and averaging all the star positions to one would lose that information.Frank
Uncle Rod Uncle Rod's Astroblog: http://uncle-rods.blogspot.com/
Quote: I haven't actually used those mounts without index switches - but the principle is the same: even if the mount is mechanically perfect, it needs to know which dec.
Quote:Yes - the index marks correspond to the switch positions - and as such they are assumed to be slightly offset from the true 0/90 location and not perfect. That offset has to be calibrated very accurately - for a gem or fork mount - if the pointing is to be accurate.
LX850 blog: www.LX-850.com
personal website: www.wadsworthobservatory.com
Quote:I completely disagree. The dec. offset is very different from the RA offset - which is what I assume you are referring to.
Quote:The Dec offset is one of the things that is calculated as part of the alignment process, along with Ra offset, cone error and the two polar align errors
Quote:Wrong. Try it.Chris
Quote:Wong what? Read this