From: "milton_aupperle" <milton@outcastsoft.com>

Date: August 21, 2011 11:51:56 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: Guiding HW Addition

Hi Folks;

Testing last night went well and I managed to image M27 before the turublence got really bad.

http://groups.yahoo.com/group/Astro_IIDC/files/DSO/M27_20110820_MJA.jpg 

That is 16 minutes per frame Luma (binned 1x1), 5 min Red, 4 min Green and 4 min Blue (binned 2x2) shot at 1625 mm focal length. Guding was via the new GPIO to ST4 connection on a Flea camera on a Celestron OAG (Off Axis Guider).

I discovered that I needed to connect the Cameras ground to the ST4 ground for the GPIO pins to work and will update the schematic diagram later today.

So I now have one cable running from the Mac to the mount, which  controls two cameras (imager and guider) and also attaches to the ST4 port to control the mount. That will make life a lot simpler when the temperature drops to -30°C or colder and I can leave the guider connected all the time.

TTYL..

Milton Aupperle

--- In Astro_IIDC@yahoogroups.com, "milton_aupperle" <milton@...> wrote:

Hi Folks;

Second time is the charm and here is the revised PCB that should work.

http://groups.yahoo.com/group/Astro_IIDC/files/Other/GPIOtoST4_Interface_V2.jpg

I'll be running tests tonight after it cools down and the sun isn't baking the patio.

One thing I found out is that the latency time is immensely faster with GPIO FireWire versus the GPUSB. The GPUSB takes 8 milliseconds (8/ 1,000th of a second) to send a pulse to open or close a switch.

With Firewire and the GPIO control, that drops to 0.08 milliseconds (8/ 100,000th of a second) to send a pulse to open or close a switch.

Astro IIDC measures the round trip time to send a pulse and if a correction would take less time that this latency, then we would not make the correction until it would be greater than this. This will improve corrections response time.

TTYL..

Milton Aupperle