Archive for the ‘Serrurier 20in (50cm) Reflector’ Category

20 inch (50cm) Reflector Ready

Posted by Paulo Cacella on 5th January 2014 in Instruments, Observatory, Recent Posts, Serrurier 20in (50cm) Reflector
I´ve finished today the reflector. The design was a Serrurier Truss (the same as Palomar Observatory). The first night at theobservatory with a reak sky was perfect. The telescope performed flawlessly, maintened collimation, impressive images of Jupiter, Eta Carinae Nebula, Open Clusters etc.

Telescope is setup on a Chronosmount HPO. The mount is capable of a 250 pounds differential load. This means that it can handle Telescope and acessories without a counterweight.

The telescope structure was manufactured in two days. I´ve used aluminum and proper tools and bolts. Alot of patience too.

Next night available I´ll test with cameras and RCC-I Baader coma corrector.

tel2.

Observe in the picture below that we can see Sirius, the brightest one, to the right, Orion shines with his belt in the center and Hyades and Pleiades finishes the parade to the left.This was the sky when the telescope saw the first light. A kind of Science and Poetry.

tel1  

20 in (50cm) mirror arrived

Posted by Paulo Cacella on 30th April 2011 in Observatory, Serrurier 20in (50cm) Reflector
I’ve got my mirror to build the telescope. It is a 20″ with strehl ratio 0.98 from pegasus optics.



Building a 20 in (50 cm) F4.3 newtonian – Part I The Software Tools

Posted by Paulo Cacella on 13th November 2010 in Observatory, Serrurier 20in (50cm) Reflector
I have ordered a 20 inches mirror from Pegasus Optics to build a 20 inches F4.3 newtonian. The instrument will have basically three roles in the observatory : Visual observation of deep sky objects, imaging of faint objects and spectroscopy. The first step is to design the telescope. It is not really possible to design an optimized system for all these functions. We have two possible options : A single compromise design or a changeable secondary to allow these functions to be optimal in each case. I am not sure at this point the real differences I may find, then a field test will be necessary before reaching a final conclusion.

To design the telescope we may calculate everything manually or, in a better way, use a free software to do this. The most simple and useful for the first design is NEWT for Windows.

We have basically two commercially available secondaries for this telescope. One is the 3.5 in and the other is 4 in.

Design 1 – 2 inches focuser and a 3.5 diagonal





The obstruction by area was 3% and by diameter 18%, what keeps Airy disks in a reasonable shape.  With a camera there will be no 100% illumination anywahere and the 75% illumination will reach a diameter of 1.7 inches.

Telescope dimensions would be



When not considering the 2 inches additional space for the camera we have a 0.2 inches 100% illuminated field and a 1.92 inches for 75%. Full data would be