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mall telescopes are portable; larger ones are not. It may

well be that the serious amateur observer will want

to set up a telescope in a permanent position, and this

means building an observatory, which is not nearly so

difficult as might be imagined, and is well within the

scope of most people.

The simplest form is the run-off shed. Here, the shed

is run on rails, and is simply moved back when the

telescope is to be used. It is wise to make the shed in two

parts which meet in the middle; if the shed is a single

construction, it has to have a door, which must be either

hinged or removable. If hinged, it flaps; if it is removable,

there are problems when trying to replace it in the dark

with a wind blowing, as it tends to act as an effective sail!

The main disadvantage is that the user is unprotected

during observation, stray light can be a nuisance, and any

strong breeze can shake the telescope.

For a refractor, a run-off roof arrangement is suitable.

The slidable portion can either be the top half of the shed,

or merely the actual roof, and an arrangement involving

bicycle-chains and a hand crank is relatively simple to

construct. This is excellent for a refractor, but less so for a

Newtonian or Cassegrain reflector, because here we have

to contend with a restricted view of the sky.

A ‘dome’ need not be a graceful construction; it can

even be square (a contradiction in terms!) and mounted

on a circular rail, so that the entire building revolves and

there is a removable section of the roof. This is suitable for

a relatively small instrument, though larger ‘total rotators’

become so heavy that they tend to stick.

▼ The author’s 39-cm

(15-inch) Newtonian reflector

at Selsey. The mounting is

of the fork type.

The author’srun-off shed

for his 32-cm (12.5-inch)

reflector. The shed is in two

parts which run back on rails

in opposite directions.

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