Back in '95, an 8086 drove the dome and scope. I built an ISA card (visible in open box image here) with 35 ICs to provide all manner of digital and analog I/O and buckets of code. All migrated successively to 80166, 80286, DX400, Pentium II and an Athlon. The PC(s) linked up via buried coax ethernet to a another in the house (upgraded to wireless in 2007), where I do all my control remotely. I coded s/w to reduce the data, batch processing of raw images, and a clever sub-pixel alignment tool which pixel interpolates multiple FIT
images (improved resolution and star shapes). PC hard disks life span are much shortened by freezing temperatures, so PC(s) are inside an insulated box (shown here open and closed - click image to 'open'), with three thermostats; one controls a low power hair dryer to increase the box' temperature, at which point a second starts up the PCs and a third exhausts excess heat via a fan, fully sealed/screened from insect intrusion. Diskless operation with CF flash memory via IDE was attempted to remove the need for temperature control, but proved to be excessively slow and having too few total permissible write cycles.
A recent addition is a Pentium D, unheated. An Hitachi Endurastar
2.5" hard disk was chosen as it can operate down to -20 Celcius. In July 2007, the home grown drives and incremental encoders were replaced with commercial components accessible via USB. In May 2008, the *warm box* PC was removed and all operations and devices are now under the lone Pentium D. In February 2010, Icron Ranger 2104 was installed, providing USB services over 150ft/46m of CAT6 buried cable so that the house PC could drive the entire observatory (Dome PC removed - no more winter temperatures and humidity issues!). Too bad solid state drives came too late :o[