From: Milton Aupperle <milton@outcastsoft.com>

Date: April 9, 2008 10:26:25 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Guiding Celestron mount?

Hi Alen;

On 9-Apr-08, at 3:09 AM, Alen Salamun wrote:

Hello Milton!

I really can't belive it how Celestron would make guiding over autoguide port different as over HC commands.

Auto guiding over the ST4 port does not use any commands at all. You basically are using a 3.3 volt relay box that closes switches and that activates servos in the mount. Think of it as 4 light switches that are on or off for each axis.

Also bandwidth USB vs. Serial should be no issue at all. 115kb/s is more than enough for guiding commands and results as they are very very short.

Even if a command would be 1kb long we could issue 100 commands/s.

That would be true if you were running at 115Kb, but your running at 9600 baud (N 8 1) with the serial ports, which is 1.17 kilobytes per second maximum. And there have to be delays between commands, because your waiting for response back from the mount with Celstron. The GPUSB takes 1 to 2  millisecond round trip to send a single command (we mesasure it and account for that when starting / stopping the servos), so it's very quick and precise.

Secondly, with the Celestron protocol you have to read the current position (both RA and then Dec) out first then write the new location back out. It is at least 3 times as slow as doing it Meades way or the GPUSB way, which don't require you to wait for a response - just tell it to move for this length of time.

We clearly didn't understand us over programming help part. I wanted to say, that if you don't have Celestron mount by hand to test anything I can do it.

Ahh, okay - I thought you were insinuating I didn't know what I was doing. Sorry for the misunderstanding. My HEQ5 mount is pretty much the same as a CG5E and uses the Celestron commands, but I still guide with a GPUSB.

Well we cleared the issue, Celestron is the one to blame as it seems.

I completely agree with that.

If you look through Celestrons and Meades LX command sets, you can see just how different they are. The Celstron one is designed for goto and offers very little direct control after that. The Meade API is much better engineered and thought out.

Hope that helps..

Milton Aupperle.