What are the units of a photometer?

Related questions

• How are quasars, seyfert galaxies, radio galaxies, and normal galactic nuclei related?
• What is the major observational difference between a Seyfert galaxy and a normal spiral galaxy?
• How are seyfert galaxies like quasars?
• Does the Milky Way have an active galactic nucleus? Is it or is it a type 1 or type 2 Seyfert galaxy?
• Seyfert galaxies are thought to be undergoing very violent processes. Does that mean they are...
• How are X-rays used in astrophysics and astronomy?
• How do x-rays help determine a celestial body's temperature?
• What range of temperatures can an x-ray distinguish when studying celestial bodies?
• If x-rays are normally absorbed by the earth's atmosphere, how do astronomers overcome this...
• What types of objects in space emit x-rays? How are the x-rays detected?