Saturn is probably the most exciting planet on the firmament to watch. Looking through a telescope and spotting this gas giant with its ring system is something remarkable one will never forget. You can find this science-fiction-like planet for the next couple of weeks at the constellation of Virgin, just above the bright star Spica. Saturn got about 60 circling moons, but only a few can be seen with an amateur telescope. Imaging planets is best done with a CCD-camera in video modus and stacking a couple of hundred single shots from the video with software. Since I don´t have one (yet), I only take single shots, which is good for getting familiar with the equipment.
Single shot of Saturn with Meade 8″ ACF, LXD 75, 9 mm Plössl, 2 x Barlow, Pentax k-x, 10 sec., Iso 100, no crop;
Meade 8″ ACF is the telescope, LXD 75 is an equatorial mount, Plössl´s are ocular, a Barlow lens works like a tele converter with a camera. The 8″ got a focal length of 2000 mm and a f 10 aperture; if you divide the focal length through the ocular focal length you get the magnification of your set up. In this case: 2000 mm/9mm= 222 times, doubled up by the Barlow lens= 444 times; a normal pair of binoculars like a 10*50 got a magnification of 10 times!
So this image shows Saturn with a 444 times magnification compared to the naked eye. By using a Barlow lens, like with tele converters, you double up the aperture – in this case from f 10 to f 20. And the focal length with this set up? Actually, astrophotographers don´t really talk about that, they just say: I used that set up. I calculated a focal length of almost 47 000 mm/ 47 meter! with this set up, including the crop factor of my k-x, but I´m not sure about that… just enjoy the image!
“I was, I remember, I still remember when the first time I pointed the telescope at the sky and I saw Saturn with the rings. It was a beautiful image.”
(Umberto Guidoni, Italian Astronaut, born 1954)