Greenswale
27-02-2008, 03:22 PM
Had my first play with a UHC-E filter in the back yard last night. Pretty cool device, but when looking at Mars, I noticed a tiny very red spot on the outer circumference of the planet.
I could make the spot move around the circumference of Mars by moving my eye around the eyepiece - an interesting effect. The spot may have been there when observing bright stars such as Sirius, but was difficult to be certain. Removal of the filter resulted in removal of the spot.
Seeing was ordinary, lots of suburban light about, moon was well out of the way. Equipment was Celestron Nexstar 6SE, Tele Vue 32mm Lumicon UHC-E filter.
So the question - what is the explanation for the existence of the little red spot?
I could make the spot move around the circumference of Mars by moving my eye around the eyepiece - an interesting effect. The spot may have been there when observing bright stars such as Sirius, but was difficult to be certain. Removal of the filter resulted in removal of the spot.
Seeing was ordinary, lots of suburban light about, moon was well out of the way. Equipment was Celestron Nexstar 6SE, Tele Vue 32mm Lumicon UHC-E filter.
So the question - what is the explanation for the existence of the little red spot?