Home Observatory Equipment Images Technical Notes


Updated: 07/04/2008


Hardware - a matter of inches

The main scope is a 0.4m F/9 Ritchey-Chretien carbon truss design, model 16RC, manufactured by RC Optical Systems.  The primary mirror uses a 18-point flotation system to mount the plano-back Aries Instruments primary mirror.  Aggressive baffling is used to minimize out-of-field reflections.  The telescope is equipped with a servo-controlled secondary focuser and a Precision Instrument Rotator (PIR).  Focusing is done exclusively by the secondary focuser with the various extension tubes of the FIA providing solid, flexure-free camera mounting at the proper back focus.   The PIR, the red assembly visible at the rear of the scope, provides precise and repeatable rotation of the camera to locate a suitable guide star and/or appropriately frame the image.  The primary mirror fans are under thermistor control to bring the mirror within a user-specified tolerance to ambient temperature.  The secondary mirror can be heated, also under thermistor control, to a user-specified offset from ambient temperature.  All of these controls are operated, powered and controllable by the Telescope Command Center.  The TCC can be commanded locally via a hand controller or remotely via RS-232 and a PC application.  The instrument package consists of an Apogee U16m camera and FW-50-7S filter wheel off-axis guided by an SBIG ST-402 mounted on an AstroDon MegaMOAG.  I image at 0.51 arc-sec./pixel.

Fitting such a large scope into the observatory was tight, to say the least.

Clearances were carefully measured to insure the scope would fit.  It does, but without a lot of space to spare.  The ugly free weight mounted on top of the 16RC was needed to offset the balance point shift necessary to fit the scope in the available space.  The equally ugly free weight on the counter-weight shaft was then needed to offset that weight!  I use a park position that is close to the final nested position and manually nest the scope below the roof with the ME's joystick.


Parked, the scope just barely fits in my "spacious" observatory.  It clears the inside of the roof by a whopping 1.2" and you can see the end-to-end clearance. 

A extended temperature range USB hub is mounted on the MMOAG along with power distribution to minimize the number of wires coming back to the telescope.  Only a 12 volt power cable and a single USB cable is run through the mount.  The TCC RS-232 uses the ME's through-the-mount wiring to get to an Edgeport/4, located on the pier and thence to the computer.  The computer is a Mac Mini running XP Home under Boot Camp. 

The mount is a Software Bisque Paramount ME. This is the finest mount I have ever owned with excellent repeatability, cable management and no clutches!  All power and signal wiring is routed through the mount.  There are no external cables attached to the OTA.

The Paramount sits on a Pier-Tech 3 elevating pier, which can be raised an additional 20" for either visual work or those low southern horizon objects.  For most CCD imaging uses, it is used in its fully retracted position as is the case in this picture.  This allows the 16RC to come within 20 of the horizon and protects the main body of the scope from wind and stray light.

The observatory is built above the roof of a single car garage.  The scope sits on an eight-foot concrete pier.  More specifics on the
observatory construction are located here.

All power supplies are located below the deck in an area that is accessible by lifting up a portion of the carpet and an access panel. The telescope is controlled remotely from my office in the house over a 1 GHz Ethernet network and controlled by my Mac Pro.  The observatory computer runs VNC server and the Mac Pro runs Chicken of the VNC. The cable run to the office is approximately 60 feet. When parked, the telescope is horizontal, pointing south, on the east side of the mount. This allows it to clear the roll-off roof.  The east stop and weather seal is just visible at the top of the black area behind the scopes.  Over many monsoon seasons, this arrangement has proved weather-tight with no leaks.  Finally, Here is a view looking up from below.



Name Version Source
Mira Pro
Qimage Pro (Printing)
Brady & Weber
Software Bisque
Software Bisque
Software Bisque 

Qimage Image Printing Software


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