The guide scope: 90 mm Maksutov on an iOptron goto mount "the Cube"
Astronomy - equipment 0
updated Sep  '12

The beginnings of a lifelong interest in Astronomy was kindled in 1979 when I chanced upon books in the town's library. I remember well the photographs of primitive but effective telescopes, noisy galaxy images, and spring air at the time. Decades later, the same books are no more at the Westmount library, but the same spring scent evokes the memories.

Astronomy was a private affair until the mid 80s when I visited the folks at Stellar Telescopes on Decarie in Montreal; Fred Clarke, Donald Alexander, Gary Boyle and Alister Ling. Friendship ensued and we'd meet Thursday evenings and late summer at Stellafane.

Having graduated in both Physics and electrical engineering at McGill university, my interest in Astronomy covers the latest cosmological developments to telescopes nuts and bolts. I've polished the 8 inch mirror twice and built three mounts in the process, coded thousands of lines of C, built an observatory and two CCD cameras. I've ported snippets of my code onto flight simulators! The mostly home made components are discussed below; I've spent too many hours on glorious summer days and freezing winter nights coding outdoors, hammering and cursing my designs.
Dome
Having built a house in 1995 on two heavily forested acres,  I erected a tower to catch a better view of the firmament rolling above. The concrete pier sprung from deep in the ground and isolated from the octogonal  tower is some 18 feet in height. The observatory stands 22 feet and 12 in diameter. Four drives move the dome. The 60" dome shutters are opened by chain driven screws powered by a 12V battery. Relative position/velocity are sensed by an optical encoder and absolute position by an AS8150 barcode reader. A pan/tilt infrared night vision camera provides a view into the dome during remote operations. A 500W air conditioner is software controlled with an X10 to keep the temperature difference inside vs outside less than 2 degrees in summer. Time lapse videos here.
                                                   Telescope
The Newtonian 8 inch parabolic mirror has a 44" focal length (F/5.5), hand figured twice since 1980. It tied for best optics at Stellafane in 1989 (with a 6" Maksutov). The mirror is the only original part of the telescope; three paper and one aluminum tubes, three mountings, two secondary mirrors, many new coatings later, it eventually became a guide scope for the C14 OTA (here). A 90mm Maksutov on a Goto mount (iOptron's "the Cube") used to serve as steerable guide scope via Ascom - arguably the only such use of a Goto scope in the world! Both scopes have full aperture RC servo motored sky end caps. In 2010 the Cube took on new duties as a mount for a Lunt 60mm H alpha Solar scope.
Main scope motored sky cap - in half open position
Scope with Audine and cooling fluid tubes.
Mounting
In my workshop, the fork arms and other parts were cut, welded, lathed & milled. The nylon gears mesh with 3/16" bolts; done by spinning a tap against the disks on a lathe, it naturally cut into and spun the disk. I built/coded an 8051 uController four channel power amplifier to drive the phases of two stepper motors in a saw tooth (not micro-stepping); it's ultra smooth. Right ascension screw sensing provides PEC (periodic error correction). The same DOS PC also has predictor corrector tracking software to ramp up the motors to track satellites via LX200 RS232 commands issued by satellite tracking software. Guide 8 provides pointing commands via the network.

In 2007, the stepper motors and home grown linear amplifiers were replaced with IMS intelligent motors via USB, and the incremental encoders were replaced with 17 bit serial absolute encoders that are read by a USB FPGA (see here). It had become a pain to support both the ISA card and the relative encoders which required finding the index pulses for absolute positioning. The DOS PC was no longer required and removed from the observatory. I coded Ascom compliancy into my drive software so the CCD camera could guide the scope. The right ascension gear and worm were replaced with a 9 inch Byers gear and worm with a far lower and repeatable periodic error (graph below - 1 sec exposure @ 10 sec interval).
Newly installed Byers on RA and serially linked intelligent micro stepping motor
17 bit absolute encoder housed in bottom black box. Previous homemade RA drive shown - replaced by Byers.
Measured periodic error on home made and Byer's drives
CCD Cameras
I built two CCD cameras; Cookbook and Audine. Both cooled with Melcor's thermo-electrics and pumped glycol. The Peltier currents are  PWMed by a 68HC811 uC. The Cookbook was replaced by a USB Starshoot for Ascom guiding. The Audine has a novel balanced impulse shutter I designed generating no heat in operation. I purchased a USB box for the Audine from Essentielles Electroniques, ridding PC resource usage (paralell port), halving readout times and removing the interference picked up from the PWM. The Audine is reknowned for frost build up on the CCD glass face; foam blocks were sculpted to fit in most of the empty spaces within the camera; ultimately, sealing the camera and pumping a partial  vacuum did the trick. The coolant is in a tank, pump circulated, with valves to purge or replenish the system easily (see photo further below - click to expand).
Audine innards - homemade balanced impulse shutter and air space occupying foam.
Computers and Software
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[
 
Pardon the mess of wires: improvements in the dead of winter, wires are very stiff. I cleaned it up the following summer.



Movie 'tracking' a geo-synchronous satelite whilst stars fly by:
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Astronomy

Computers and cooling tank - click on on items
ThermalBox [no longer in observatory] DomeBox DomeBox

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Me and my tower in the trees
See here for latest development on new 14" OTA installation.
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