by Chris Peterson » Tue Nov 22, 2011 5:30 pm
'Toine wrote:Hi everybody, I've been intrigued by this green orb near Aldebaran too. It looks like a planetary nebula, but there isn't any planetary nebula here, especially bright and big like this. I've searched if there's not any comets in this part of the sky those days, but there's just Garradd in Hercule. So what can it be? :?: Could it be an artefact? :shock: If someone have an idea :mrgreen:
Whenever you see green halos or fuzzy spots in a nighttime image made with an ordinary camera lens, you should suspect some sort of internal reflection. Camera lenses have many surfaces, and they normally have antireflection coatings that have a peak reflectivity in the green part of the spectrum.
This could be a ghost reflection of Aldeberan (likely, given that it is near the optical axis), of another bright star, of one of the artificial lights on the ground, or of something outside the field completely, like the Moon.
[quote="'Toine"]Hi everybody, I've been intrigued by this green orb near Aldebaran too. It looks like a planetary nebula, but there isn't any planetary nebula here, especially bright and big like this. I've searched if there's not any comets in this part of the sky those days, but there's just Garradd in Hercule. So what can it be? :?: Could it be an artefact? :shock: If someone have an idea :mrgreen:[/quote]
Whenever you see green halos or fuzzy spots in a nighttime image made with an ordinary camera lens, you should suspect some sort of internal reflection. Camera lenses have many surfaces, and they normally have antireflection coatings that have a peak reflectivity in the green part of the spectrum.
This could be a ghost reflection of Aldeberan (likely, given that it is near the optical axis), of another bright star, of one of the artificial lights on the ground, or of something outside the field completely, like the Moon.