SAAO - South African Astronomical Observatory

SAAO 1.0-m Telescope


The 1.0-m telescope was built by Grubb Parsons in 1964 and erected originally in Cape Town. At the time of the move to Sutherland, the Cassegrain f-ratio was changed from f/20 to f/16. See the optical diagram in Figure 1 for the relevant dimensions.

Cassegrain focus  

f/16, ~12.94 arcsec/mm (CCD)



Offset-guider and acquisition box

Baffle System

8' Diameter unobstructed field at Cassegrain


100 mm f/10 refractor


Figure 1.  Optical diagram of the 1.0-m telescope.

Sky Coverage

The design of the telescope and its building limit the view of the sky somewhat. The following are approximate observing limits for the 1.0-m telescope on the east side of the pier.  The eastern limits are set by the south pier at -80° and the prime focus carriage at all other declinations.  If observations require the telescope to operate west of pier, a request should be made to the Head of Telescope Operations when applying for observing time.



Acquisition & Autoguider Camera

Use of the acquisition camera and autoguider is described in the TCS manual, which also contains instructions for the selection of guide stars.  Findercharts of 8x8 arcmin are appropriate.  

Visitors' Instrumentation

There are practical limitations on the equipment that can be mounted on the telescope. The unvignetted field is about 34.5 arcmin (160 mm), but if the acquisition and guidance box is used this reduces it to 12 arcmin (55 mm). The focus can only be moved from 250 mm behind the mounting plate to 950 mm behind it, or if the guider box is used, from 0 mm to 530 mm. The instrument may weigh up to 150 kg. It may be possible to carry heavier equipment but SAAO should be consulted at an early stage. The equipment should not be longer than 1500 mm. Note that long, bulky equipment severely restricts the observing limits of the telescope. Cables for visitors' own equipment should be about 12 m long to drape over the telescope and reach the floor. The warm room is about 5 m away when the telescope is on the east side of the pier.

The acquisition and guidance box (Figure 2) is identical to that on the 1.9-m telescope.  The mounting hole positions for the Cassegrain small instrument adaptor are the same as those for the two inner rings on the 1.9-m Cassegrain small instrument adaptor.

Figure 2.  Acquisition/Guider box.