If you build an astronomy device and want to control it with some awesome PC software, then you need to write an ASCOM (AStronomy Common Object Model) driver. There are great resources available for writing a single ASCOM driver for your DIY astronomy equipment. Check out the video on the ASCOM website for a guide on writing a single-device driver! But say, for instance, you have two devices (a Telescope and a Focuser) and would like to control them with one microcontroller. Or say you want to control your telescope with Astrophotography Toolkit AND PHD2 at the same time. Then you need to write a Driver Server!
Astrophotography is a bit of a money pit. I recently delved into it with my 80-200 f/2.8L and a home-built tracking mount. It was so much fun that I decided to buy a telescope! So my entire budget went into an 80mm APO.
The problem was that a telescope alone is useless for star pics – some quality infrastructure is needed. This post is about my attempt to affordably build the following components:
High-precision Tracking Mount with an ASCOM-compliant driver
Guide camera and scope to help the tracking
Portable Power supply
Telescope Focusing motor with an ASCOM-compliant driver
The V2.1 update produced a working mount, but it unfortunately was not very user friendly. I made a few modifications to improve the setup and aiming time, as well as its ability to disassemble and stow in a modest-sized wood box for storage and transport.
V2.2 (codename: HoLi) is the mount’s final design, as I’m very happy with it and have moved on to building the V3.0. See the photo of Orion’s Nebula below taken using this mount, I’ve been happy with its performance using lenses as long as 300mm.
At the last minute, I purchased a sheet of Baader Planetarium solar film for the eclipse on Monday. With little time to spare, the film was taped to a cardboard box and slid over my telescope. Prayers were made that the wind wouldn’t blow the film off of the scope, and the next day I decided to build a proper holder for the expensive film – $100 CAD for an 8″ x 11″ sheet!
I’ve recently developed a healthy interest in astrophotography. A very useful tool for photographing the great beyond is an astrotracker. It counters the rotation of the earth (360 degrees per day) and allows for long exposure times without creating star trails. Here’s my POC build- it’s as cheap as borscht and worked great for very light loads. However, it failed to properly support my camera setup- a 5Dc with Tokina 16-28, total mass of over 1.8 kg (without the battery grip). As such, it is to be dismantled and a better version is in the works (waiting on eBay China parts). That said – If you have an SL1 with an EF-S lens (less than 1kg total mass), this may do the trick!
Screws, 1/4 nuts, 1/4 ready-rod, hot glue
Linear actuator from DVD-burner
eBay China L298N dual H-bridge – $4
eBay China mini breadboard – $1
Power resistors – $10
ATTiny85 microcontroller (and programmer)
Various tidbits here and there
The linear actuator operated on 5v, which meant that our 12v supply needed to be tamed with a couple resistors (biggest cost of the whole project). I used a 11×17 sheet of paper, folded into a tube for the 8xAAA battery holder and a spring to apply pressure to the battery contacts. A cheap battery holder will be a welcome update for the MK2.
As a note for future projects: the linear actuator was excellent for light-duty projects. Do not de-solder the power supply ribbon, instead simply cut it. The ribbon provides support to the feeble leads coming out of the motor (I ruined one motor by treating the leads harshly). The microcontroller was programmed to provide power for a brief duration (500ms) during each step. This greatly reduced heat build-up in the actuator, and likely greatly improved the actuator’s life. Finding a 5v H-bridge would be a nice improvement over the 12v L298N.