Thursday, January 15, 2009
Comment on this picture: NGC3521
It looks like light is coming in from the side. This is a classic example of what that does. Even though the light source is off to the side, and not in the image, it still creates an illuminated area As you can see, the shape of the illuminated area is like a conic section. That supports the idea that the source of the light is outside the field of view. Baffles inside the telescope are intended to stop this. They do reduce it. But do not eliminate it. There is usually a strategy about being so many degrees AWAY from the source of illumination. That can help when the moon is out, or when the sun is coming up.
P.S. -Also there is a question of getting more exposure for NGC3521. This is typically done by taking 5, 10 or 20 images, and stacking them together. This improves the signal to noise. And it gives more information of the dim object to work with.
Then POST-PROCESSING is essential. A deep space object is NEVER done, when the images are complete.
That is less than have the time and skill involved. Specialized software is mandatory. This increases the visibility of dim objects. However, this only applies to "pretty pictures". Scientific images are data. And the data is not manipulated to make it look prettier.