- Catadioptric telescope Cassegrain Relay of 400 mm. diameter at F/6.5 (Larrosa)

- Apochromatic telescope of 120 mm. diameter at F/6.5 (Vixen)

- Camera CCD ST8XE with dual CCD for autoguiding (SBIG) only on T400.

- Camera CCD ST8300M (SBIG).

- Camera SLR (Canon 350D) modified without IR filters, on the R120 telescope or Carl Zeiss photographic lens.

The main telescope of 400 mm. is inside a dome on an equatorial fork mount controlled from the computer room downstairs. The 120-mm apochromatic refractor and photographic lens of 2.8/180 are piggybacked to the main telescope.

Doing a comparison between some optical configurations we will note the Cassegrain-Relay has a great advantage against other configurations like Schmidt-Cassegrain, Newton or Ritchey-Cretien, due to the following reasons:

- Quick focal ratio and small secondary obstruction (F/6.5 - 27%).
- The 96% of all visual spectrum from 400 to 700 nm, inside de Airy disk.
- All optical surfaces are spherical so, easy to make and easy to verify.
- Low sensibility to decentering / uncolimation.

Component layout of the 400 mm. Cassegrain-Relay optical system.

Spot diagram on axis of the 400 mm. Cassegrain-Relay telescope.

Modulation transfer function (MTF) of the 400 mm. Cassegrain-Relay telescope.


The telescope tracking accuracy without PEC is +- 1.5" (arcsec). The centering accuracy after an slew of 35º degrees is 18".5 arcsec.





  Copyright 2012 - Joan Genebriera

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