SPAO Replacement – Planning

Construction of the Snowy Plains Astrophysical Observatory was completed in 2002. The site was my back yard on the East side of the property offering excellent views of the N-NE- E-SE-S-SW and Zenith skies. To the W and NW the house impedes the view, with a tree that eventually had to come down due S. At the time the land to the South was completely devoted to farmland so light pollution was extremely minimal.  Since then, the Sage Creek sub-division has increased light pollution immensely, rendering the observatory much less useful than in previous years. Clearly, I need to move the whole thing to darker skies.

SPAO May 2022 with 10″ telescope

Originally the observatory was designed to house a 16″ f5 reflector on a horseshoe mount with an 8″ f10 “planet killer” telescope mounted on top. The building was in fact built around the large mount for this telescope to avoid having to manhandle it into the shed after completion. This setup included a large pad instead of a pier for the horseshoe mount. Eventually it was clear that the telescopes for the shed were not going to get completed very quickly (and in fact are just starting to get worked on again 20 years later!) so instead a pier was added to the pad for the telescope and an 8″ SCT mounted in the shed. The pier for the mount was bolted to the pad and over the decades has not shifted at all. Whether this is a characteristic of using pads instead of drilling piers deep below the frost line is not clear and may just be fortuitous for the particular patch of land the observatory sits on.

In May once the observatory went into full operation with a 10” F/4.7 scope on an NEQ6 (above) I noticed that over the winter some of the 4×4 supports for the runoff rails have shifted, and it looked like the 600 lb roof had a real possibility of a sideways excursion through the neighbour’s fence at any time. While this can be corrected, it instead made me move a micro-observatory (MO) project to the front burner, since anything I build will need to be capable of relocating to a dark sky site. Building the MO will involve demolishing the existing building and using the materials to build with. This is helpful as materials are now extremely expensive, so reusing what I have makes this a very low cost project.

Micro-observatory planning model

The figures above are from a model in Fusion 360 showing the concept for the MO. Overall this is pretty much the same concept as my larger observatory, scaled down from 10×10 to about 4×4.  Reducing the size of the roof simplifies automation immensely.

A square building sufficient for the telescope only to swing in it’s various movements without needing room for a person to stand in the shed to operate the telescope.  The building sits on cottage blocks as do the supports for the roof runoff. The roof slides back on 4 V groove runners per side on steel angle iron rails.  A traditional pier is shown as well as two large bolts to secure the building from simply being loaded on a trailer and stolen. More on security in subsequent articles. The roof runs off to the North to facilitate viewing South, and is tilted to facilitate solar panels with a rain gutter required to ensure moisture running off the roof does not end up in the structure.

Automation is planned using a gate opening system that uses a toothed wheel and gear rail to open and close based on the time and weather, My intention is to keep the observatory busy any time the sky is clear 4 seasons with photometric observations and astrophotography.   This will also require a weather station and AllSky camera, which I am already operating near my existing observatory.

Some accommodation for winter operation to keep the rails clear and deal with snow also requires some experimentation. Given my current observatory is often unusable December-March due to being buried in snow, clearly this problem will be even worse with a smaller building so I’ll be looking at different active measures to keep the building snow-free.

Operating the roof automatically will require a new level of rigour in detecting clouds and rain and putting the MO in safe mode (telescope parked, roof locked) whenever weather deteriorates. Critical functions such as roof movement and mount power will need to be battery backed to ensure even in a power interruption the shed can go into safe mode. Since the power system will likely be solar (and perhaps wind) battery levels will need to be monitored closely and low levels initiate safe mode automatically.


Needless to say this will be a completely automated observatory, continuing a process of automation I’ve been engaged in for many years. My current observatory has gotten the to point where the only time I need to be in there is to roll the roof on and off, and to occasionally troubleshoot cables and connections. Often all problems are resolved by simply cycling the power, so the new shed will need this capability.  Since it will be a remote observatory it will need to be solar powered, and have some form of Internet to allow me to control it remotely and download data. When the MO moves out to a dark site I’ll use a Mifi cellular wireless hub I already own to communicate. Since this device uses a cellular data plan that can be costly,  I will have a computer in the building that will process most data (e.g. calibration, stacking, and differential photometry) and simply send me the resulting images and data, rather than gigabytes of unprocessed data. With sub-exposures from my ZWO ASI183MM camera now topping 72megs each in FITS format, I currently move a ton of data around on my home network. This is unfeasible for a remote observatory.

Fortunately, the software tools to create a system of this nature are available free from the Open Source community. Currently my setup uses Stellarmate on a Raspberry Pi 4[1] (RPi4) to run the mount, focuser, filter wheel, imaging camera, guide camera, and GPS using the INDI[2] server system operated from my desk inside the house with KStars and EKOS.  Adding image processing with SIRIL[3] to do automated calibration and using Python to process science images complete the picture, although as SIRIL currently doesn’t run on RPi a beefy computer will be needed on which to run these processes. This will be done on an HP EliteDesk 800 mini desktop computer I already own, which has lots of RAM and a powerful CPU. To make integrating with the RPi4 easier this computer will run Ubuntu LINUX. The HP will connect to the Mifi wirelessly and to the rest of the observatory via a 1GB wired network and provide Internet to all of the other devices. For more info on the software I use and develop in Python check out my Python page[4] on my website. All software I build for this MO will be Open Source and published on my page.

HP mini-computer

Initially I expect power will be provided by house electrical, but eventually will move to a pair of 33 Ah battery packs, each charged via a 40W solar panel on the roof of the building. Each panel includes a 7A charge controller to prevent overcharging the batteries. Hopefully this will keep the batteries charged to the degree they can operate the building and telescope as often as needed but testing will determine if something with larger capacity is required.

Solar panel

The MO will sit in my back yard for a couple of years to fine tune the system to be completely autonomous so once I plunk it out at a dark site I won’t need to touch it very often. How often I need to touch the MO while in my back yard will be a big determining factor as to when it’s ready to move!