From: Milton Aupperle <milton@outcastsoft.com>
Date: June 22, 2008 11:00:12 AM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] Re: Quick question about alignment
Hi Kirkus;
On 21-Jun-08, at 3:28 PM, KirkusMcGurkus wrote:
-----------SNIPPED for brevity
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.
I did the same thing to my HEQ5 mount.
It had lots of black "gunk" they call "grease" (I think it's just spit, soot and old newspapers ground into a paste). At -38°C it would turn into concrete and the mount would basically not move or just binds, regardless of how much I fiddled with the gear / motor tension.
I removed it all (toothbrush, lots of paper towels, toothpicks and several cans of WD40 and degreasers) and re-greased my HEQ5 with a yellow lithium based grease. I also cleaned out the bearings too and then re-oiled them with good quality machine oil.
Also make sure you have no play in the RA or Dec motion when "locked". That will causes all sorts of erratic issues.
Just this spring I finally tracked down and eliminated the cause of my 4 second Dec reversal time and it's now at 1 second maximum to reverse directions. The Dec gearing had some play (from the factory) and they also had no lubricant on the Ra or Dec gears at all. So I greased them up and they now run and it tracks a lot smoother.
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.
Balance is important so that the gears are always engaged, especially on the RA. Also keeping the Guide at 1X or lower helps too, because it can either turn the motors off (at 1x) or just slow the motors down without having to reverse directions for backward correction.
I have noticed more turbulence over the past few attempts.
Increased turbulence will be a factor too and your accuracy will be decreased as it chases turbulence. Astro IIDC 4 will use FWHM measurements to try and identify when turbulence has kicked in when tracking a single star.
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.
I don't think the 2x2 binning will make a difference, unless you also had hot pixels (i.e. a pixel that is stuck white or brighter than normal and stays that way). I normally have Astro IIDC do a Dark frame with the guide camera just before I start tracking, especially if I use high Gains / Brightness or longer exposures to remove them. Also the camera temperature can make "hot pixels" appear after a period of time too, so I let the camera run for a while to achieve steady state before guiding with it. With the old Unibrain / iBot / Pyro cameras, I do a dark Dark and a Flat frame to remove the inherent "Isoch Step" noise, which is that vertical band that appears on the left side of the view too.
Poor polar alignment will be the main issue. Pretty much all guiding software assumes that the corrections it has to make are for periodic error, not poor off axis alignment. And the biggest issue will be Dec, because Dec Lag makes it far more difficult to correct.
Also, Astro IIDC 4 can also optionally send 2 move command per correction cycle now so it can correct RA and Dec at the same time, which improves latency.
HTH..
Milton J. Aupperle
President
ASC - Aupperle Services and Contracting
Mac Software (Drivers, Components and Application) Specialist
#1005 - 815 14th Avenue. S.W.
Calgary Alberta T2R0N5
1-(403)-229-9456
www.outcastsoft.com