Attached are two guide graphs taken with the E.fric,
the Pulsar2 (at sidereal rate of course) using relays
directly from the guide camera, and PHD2 as the
The OTA was a 314mm f/5 Harmer-Wynne truss
Cassegrain, which means a focal length of about
1570mm. The OTA and associated camera train
weigh about 24kg, and the concomitant counterweight
was about 26 kg, well-balanced. (See previous postings
in this thread for photos of the setup.)
Since guiding was done with an on-axis guider,
the entire focal length of the main instrument was
used for guiding. Both RA and Dec aggressiveness
were set to 70. The guide camera has a pixel size
of 6.45um, which means a pixel scale of 0.847
arcsec/pixel. According to the Pulsar2 manufacturer,
the guide rate was set to 0.5 sidereal (setting 5).
The target was in the M29 region, which means that
the OTA (at my geographical location) was pointed
near the zenith for these tests, at approximately +38.5
degrees declination. The wind was very low, I estimate
~3kph to completely calm.
One example guide graph was taken with a guide interval
of 2.5 seconds, and the other with a guide interval of 6.0
Unfortunately, this test was done rather hurriedly,
since clouds threatened the sky. That means that the
polar alignment was probably not as good as it could
have been, since I went through only one iteration of the
alignment procedure, which skews the test somewhat.
However, the seeing was fairly good, although
transparency left something to be desired.
The interesting thing to me is that the excursions
around the midpoint were generally within +/- one
second of arc for both the 2.5-second and 6-second
intervals. I suspect that longer intervals (say,
10 seconds) would have about the same performance,
which means that the mount performance is steady
and stable. The slight upward Dec trend in the 6-
second interval graph probably indicates a non-optimal
The polar alignment was certainly not good enough for
an unguided test. I will be re-conducting these tests
as soon as sky conditions allow with 1) better polar
alignment, 2) guiding in a different, more challenging
part of the sky, and 3) longer guide intervals, including
an unguided test. I will also take more care with the
optics (focusing, etc.) so that I can also post some
accompanying images. The images I have now would
not be exactly a fair representation of what the mount
can do, although they are quite as good as anything
I have experienced with my previous mount.
I will also soon post further impressions of the mount
operation, now that I have a little bit of experience
What I *can* say is that the performance under these
conditions seems to be at least as good as my previous
mount, although I am hoping for better performance.
Certainly the Dec behavior is much steadier and more
predictable than with my previous mount.
Edited by Gregory, 05 September 2020 - 10:36 PM.