Astronomy and Sky Website of Martin Lewis

This is my home-built equatorial platform on which I mount my 222mm and 444mm Dobsonians to allow me to carry out digital video imaging of planets. The platform was built prior to the opposition of Mars in 2007 to allow me to use my undriven 222mm Dobsonian scope to image Mars that opposition. The platform which allows uninterrupted tracking for up to 80 mins, has been in regular use ever since then. 

Here you see the main mechanics and motor of the equatorial platform. In the picture you also see a large compass board on the right-hand-side which is used to set up the platform and align it correctly in azimuth. The compass board uses an oil-filled ship’s compass I bought at a bargain price in a car-boot sale on the Isle of Wight. 

At the far end of the platform’s base board are the two rollers that support the two sectors at the North end of the top board. One roller freely rotates whilst the other one (far left) is driven from a synchronous motor via a worm and wheel gearbox (seen centre left in the picture). In the first incarnation of the platform I used a pair of stepper motors driving directly onto the shaft of this roller. In 2009, however, I removed these and replaced them with the current synchronous motor and gearbox. This has massively reduced vibration, as well as backlash and slippage issues. 

Test photo with stepper motors on and motors off which convinced me that stepper motors had to be replaced by something smoother!

The black box you see in the photo of the baseboard is the drive unit for the synchronous motor (connected to end-position microswitches). The angled plate on the right holds the freely rotating rollers that bear on the similarly angled south sector of the top board.

Here you see the platform as I would use it for tracked shots of the sky with my Canon 500D DSLR. The Manfrotto tripod feet fit into the same Celestron vibration isolating sockets which the 222mm Dobsonian uses. A spring at the centre pulls the tripod down onto the platform to improve stability and reduce the likelihood of the tripod toppling over. In the shot you also see the control handset which allows me to start and stop the platform as well as tweak its speed.
Here you see my 8.75″ scope, Mr.Orb Inspector, mounted on the equatorial platform at the end of a Mars video imaging session one frosty night in January 2010.

From early 2014 have also successfully used my 18″ Dobsonian, Fossil Light, on the platform for many imaging sessions. The platform was actually designed to take the much greater weight of this scope but I never had the courage to try it out until early in 2013 when I used it for a Jupiter imaging session. The exercise of using this bigger scope on the platform has been a great success as I hope you will agree when you look at some of my Jupiter and Mars images from this period.

You can see some pictures of the set up with Fossil Light mounted on the equatorial platform below. It takes about 15mins from decision point to having the fully assembled scope on the mount – not as quick as the set up for Mr.Orb Inspector but quite doable once you get used to the much increased weight of some of the separate components!

Fossil Light mounted on equatorial platform – general view
Fossil Light mounted on equatorial platform – close-up view
Fossil Light mounted on equatorial platform – scope horizontal
Fossil Light lower bearing box mounted on equatorial platform
Fossil Light mounted on equatorial platform – general view at night imaging at home in St.Albans