Observatory Roof Automation

Background and Context

In 2008 the observatory was constructed in the backyard. In its original form, the roof had to be manually opened at the beginning of the imaging sessions and closed in the middle of the night at the end of the sessions. Avoiding the “middle of the night” uncomfortable escapades was one of the many drivers behind the observatory automation project.

The intent was to make the observatory not only remotely operated but also completely automated. The roof needed to be motorized and made computer controlled.

Here are the details about how it was done.

Design

Observatory Roof Automation

The design was inspired by some of “bat wing” type amateur observatories found online. The two panels of the gable roof were to be hinged on each side and opened from the top.

Prototype

In order to test this design, a small scale prototype was built to scale with foam core material for the mock-up observatory and Lego Mindstorms Robotic Invention System for the motor and mechanical aspects.

Unfortunately no picture of the prototype were taken.

Hardware

Roof panel modifications

Four hinges were installed on each panel along with reinforcement brackets. The panels had to be cut to allow fitting of the nuts and bolts.

Structural reinforcement

Reinforcements were added to the back wall to support the opening mechanism and to the roof panels to avoid sagging.

Motor

A “wiper” type motor was selected due to its slow speed.

Rod, Bolt and Bearings

A long threaded rod with a bolt is used to push/pull the roof braces. The rod rides on a bearing at the top and is attached to the motor (see picture above) with a homemade shaft coupler.

Braces

A pair of aluminum braces are used to push/pull the roof panels so they can open and close.

Controller and wiring

Here is the circuit diagram I designed to control the roof.

An Arduino was selected as the controller and installed in an enclosure along with the circuit.

Limit switches

Limit switches were installed at the top and bottom along with a flexible plastic tab that activates the switches.

Software and driver

Arduino sketch and ASCOM driver

Three functions were implemented directly on the Arduino:

openroof

closeroof

getstatus

These functions are being called by the driver I wrote in C# using ASCOM’s template. The driver allows me to use any ASCOM compliant software to control the roof which is in fact the equivalent of a roll-of-roof type.

Reliability

Except for a repair to the aluminum flashing, the system has been running flawlessly for many years now.