Setting up a dobsonian telescope

After years of apartment living I finally have a backyard. Even better, this backyard is quite good for astronomy - away from artificial lighting and not too close to the city. So time to get my dusty 17.5" dobsonian telescope out for a spin...

I've had this telescope since 2002 when I decided to get the biggest telescope I could that would fit into my small-medium car, a Vectra. To determine the correct sizing I cut-down a large cardboard box until it would just fit into the boot of my car and used that for the dimensions. It was a team effort - primary mirror from Swayze Optical, structure built by John Connelly on the Gold Coast, mirror support built by Ron Knight from Kenilworth and his friends. If there was ever a prize for the biggest telescope in the smallest car then this would win it!

Here are the parts laid out...

The mirror box on the left-hand side fits into the boot. The 'rocker box' in the center of the photo goes on the back seat. The poles are placed across the floor of the car behind the front seats - they just fit with the doors closed with the door's plastic flexing a few millimetres. The round upper tube assembly can be placed on the back seat with some material around it to keep it steady while travelling.

In the photo above can be seen the focusser, the secondary mirror (set at a 45 degree angle) and the 'finder scope' which is actually half of an old pair of binoculars.

 The mirror is 17.5" (44 cm) in diameter, the glass is 4cm thick and weighs almost 20kg. A new mirror like this must be kept away from dust, insects ... nothing should ever touch the surface. It is strange to have something so heavy but also fragile. The mirror needs to cool down to the ambient temperature before observing to prevent convection currents interfering with image quality. The PC cooling fan in the first photo helps with this.

First step is to place to rocker box into the mirror box like this

and then the mirror into the mirror box.

In some ways the next photo shows the most important part of the telescope

because if you loose just one of these bad-boys at night then you'll not be able to put the telescope together. I've seen someone loose a bolt after driving 100km to a dark sky location and spend an hour looking for it - a sad sight! Keep backup bolts handy.
Now the poles go up

which are attached like this...

and finally the other bolts go into the top of each pole...

to keep the upper tube assembly in place. The telescope is now ready:

While waiting for nightfall it is important to guard the equipment...

In part 2 of this post I'll show some lunar images taken with a cheap handheld mobile phone at the eyepiece and we'll even push the mobile phone to the limit and get an image of the Trapezium cluster and associated Orion nebula.