Thanks Michael.
The stars are some of the roundest Ive ever had, so I guess the
proof is in the pudding.? Still, it gives me something to tweak -
all part of the fun.? I did finally turn down a flexible coupler
and installed it about an hour ago.? A lot of work when you dont
have a lathe.? But at least the RA is done now, and maybe that
will be enough to subdue the 2nd order harmonic.
Yes, I will do a guiding assistant to accomplish what you
suggest.? Ill let it run for at least an hour.? I really just
wanted to get a baseline imaging session with the mount first
before the clouds thickened around 11pm and had to call it quits,
otherwise it would have been done last night.? Honestly, with the
cloud cover, I wouldnt have trusted the GA data anyway.
Thanks again for your help and suggestions,
-Tony
On 5/2/2021 1:30 PM, Michael Herman
wrote:
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No idea on the cause of that "half-period"
oscillation, Tony.? If it's not causing imaging problems, you
are in good shape.
However, please do this test to eliminate the
PHD2 as a cause:?
Just run an unguided 45 min to 1 hour tracking
of a star near meridian and equator.? Then you will get the
mount PE without any PHD2 autoguiding effects.
Have fun,
Michael
Hi All -
Well, the first shakedown run shook out a few bugs, but
worked through them eventually.? Overall, I think it was a
successful first light for my recently converted OnStep
G11.? I think I know what direction I want to head in, but
wanted to get the opinion of those that are familiar with
the mount.? The G11 is from 2009, has the two piece worm
blocks (fresh bearings), and has not been run in some
years before I purchased it. ? I was shooting m63 and
m101, both at pretty close to zenith, and well north of
the celestial equator, so perhaps not a very challenging
guide target.? Still, I was pretty happy with a VERY
consistent .75 to .85 arc-sec RMS for a first try,
especially considering I was shooting through thin cloud
cover the entire night.?
![Full size image]()
There's some very obvious periodic error on the RA worm.?
Lets throw the log through PEC prep to find? the period,
shall we?
The sharp spike is 119 seconds, or half the worm period.?
A quick search online shows this is most likely slipping
of the oldham coupler.? I dont have oldham coupler, they
are rigid, but they could easily have been tightened down
out of alignment, or even slipping as? the worm rotates.?
But other than the 119 second period, nothing stands out
at me as an issue.? I'm a bit relieved that I don't see
the dreaded 75 second spike.? Are there any other obvious
sources for 119-120 second PE?
I will attempt to re-align everything on the RA drivetrain
to try and center it better with the rigid coupler.? In two
weeks I hope to see my parents again for the first time
since covid, and if I beg and plead enough, maybe my dad
will bring a couple turned down helical couplers with him
when they arrive.
But all in all, seems like a good start for this mount.?
The guide error was incredibly regular compared to my last
mount which was totally random, so nothing to tune out.?
Considering the clouds and he fact that I didnt bother
setting up a wind break (< 5 mph), I think this thing
shows a lot of promise.? Glad to finally be aboard the
Losmandy train...
Any thoughts or suggestions?
Thanks all,
-Tony
