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