Quote:

---

Hi Don,

DO I interpret correctly that you refer
to imaging wihtout using VS-PEC ( in case
of using EQMOD ) ??
If so, typical residual PE would be around
+4 -4 seconds I believe.
Then using PHD on top of this will get you
around +1/-1 seconds average, which is way
below my average seeing over here :-(

---

Yes, Mert, that's correct. Plus or minus 4 arc-seconds is 8 arc-seconds peak to peak, which is the figure that really matters. That's too much for my imaging setup, so PHD would still be necessary - and PHD can get me to the vicinity of 2 arc-seconds peak-to-peak all by itself, so I don't bother with PEC control through EQMOD.

As I'm sure you know, Mert, the tracking errors of a typical Atlas have some irregular components, which is why EQMOD PEC can't completely eliminate them. If PHD starts to apply a PE correction and simultaneously EMOD kicks in with its own correction, that can't make PHD's job any easier. Perhaps if I got my Atlas hypertuned to smooth out and minimize the tracking errors then EQMOD PEC might be enough by itself, which would definitely be worthwhile.

Last time I checked there was still considerable debate in the EQMOD group on Yahoo about the advisability of using EQMOD PEC control along with autoguiding - I guess if your imaging setup is right on the brink of being usable with PHD it might be worthwhile, but mine isn't at that point. But I think the real beneficiaries of EQMOD PEC are those imagers whose lower resolution optical trains let them do unguided long exposures with EQMOD.

--------------------
Don
----------
Atlas EQ-G
Orion 8" f/4.9 newtonian
Orion 127mm Mak-Cass
Orion Skyview Pro mount
Orion 80mm guide scope
Canon Digital Rebel XT
Meade DSI
Philips SPC 900 NC webcam

Post Extras