From: "KirkusMcGurkus" <kirk@stenvall.net>
Date: June 21, 2008 3:28:22 PM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: Quick question about alignment
--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <milton@...> wrote:
Dear Kirkus;
On 21-Jun-08, at 2:36 PM, KirkusMcGurkus wrote:
For solid, accurate tracking, how dependent is Astro IIDC on good
polar alignment of the mount?
If the mount is off a lot, then it's continually makes corrections to
compensate. Dec corrections is always a major issue because of Dec
motor Lag. RA Lag is less an issue, unless the gear tensions is bad
and then you have "play" on the RA access.
I had one excellent night of tracking several weeks ago - I was easily
able to get 10 minute exposures with barely a hiccup. But since then,
I've had some trouble with getting my mount dead-on as far as polar
alignment. And since then, I've not been able to get Astro IIDC to
reliably track at all.
Which "version" of Astro IIDC?
3.02.03
And have you changed anything on your mount, like gear tensions /
motors / re-balanced it etc? And has it warmed up a lot since you
last had accurate tracking?
I've changed just about everything. LOL. After having that good bout
of tracking, I decided to overload my mount with an OTA that was just
too much for it. Since moving back to the more realistic OTA, I've had
the polar alignment trouble. Since then, I've torn both motors and the
DEC assembly apart so I could replace the crappy stock grease with
white lithium grease and have tweaked and retweaked the wormgear settings.
The temperature as also been consistently climbing over the past week.
We're currently in the middle of an extreme heat warning. Temperatures
at night have from the lower 40s to the mid 60s.
For example, my HEQ5 mount was tracking "okay" on the east side of
the north south line, but as as soon as it crossed over to the west
side, tracking errors was 1/4 of what it was before. I re-balanced my
scopes counter weights to give it less weight to the east and
tracking improved a lot.
I've heard of doing this, but have never tried. I do spend an extra
amount of time balancing the mount at the beginning of the night.
Using a DSLR, I keep the focus tube nearly pointing at the ground. I
keep it a little off-center to compensate for the spotting scope that
is located right beside it. Even at that, I've found that when
balancing on the DEC axis, I tend to be a little "rear" heavy when the
OTA is pointed East.
And now that the weather has finally warmed up here, I have to once
again (third time since spring arrived) re-adjust the tension of
gearing for the both RA and Dec. If I don't, I get play on the RA or
DEC access when it warms up and when it cooler the gears can "Bind"
when slewing at high speeds.
Add in turbulence (which gives false directional changes), over
loading of the mount (which stresses the motors and reduces response
time), poor weight balancing (which stresses the motors and also
causes gear issues) and tracking can go form great to crap very easily.
I have noticed more turbulence over the past few attempts. But since
the "good" night, I've always switched to using 2x2 binned monochrome.
The last good night I believe I was just using straight color.
HTH..
Milton J. Aupperle