*UPDATED* fixed a few config issues. Should work now as described.

I posted an SD-card image on DropBox: https://www.dropbox.com/s/idmsyydqbjci9l3/pi_for_telescope.dmg.zip?dl=0

You need an 16 GB (8GB might work) SD card, larger are OK as well of course.

*** UPDATE: Even I am using an 8GB to create the image it seems to be too big to write it back to an 8GB card. So please use a 16GB card. It's anyway difficult meanwhile to get an 8GB card. ***

It should boot on PI 2 B+ and PI 3 B+ and also on PI Zero W.  Username: pi Password: raspberry

I finished all config steps I described in my project. But there are a few to-do's;

• Wi-Fi is NOT configured. You have to configure yourself with sudo raspi-config. For Pi 2 B+ add a USB dongle of course.
• HDMI is not turned off to allow you to boot a PI Zero with keyboard and screen so you can configure the Wi-Fi
• System is prepared for RO, but booting RW. Just change /boot/cmdline.txt 
• you can add a GPS, everything is configured, just connect the hardware.
• hand controller time is set from NTP or GPS
• location is set to a fixed location, have a look at /home/pi/hc-location.sh
• Check the script to disable the green LED and run it manually /home/pi-led-off.sh  You might need to change one value for your hardware.

This should give you a quick start in just 30min.

Let me know if you found the little easter egg.