ST4 Img Exp Calculator Question

[lewis]

Hi
There is a field "Expose for" in the Exposure Calculator.
My example is running for m-108 galaxy.
What do I have to choose? Target Object or galaxy?
The results are not the same in the calculation of the exposure time.
My question: Whats the difference?
Thanks for your help, I found no answer in the help file.
Ed

[theskyhound]

Hello Ed,

When you choose to expose for a generic option, such as "Galaxy," the surface brightness is calculated for a typical galaxy.

When you choose to expose for a specific target object, which is a galaxy, the surface brightness is calculated for that specific galaxy, taking into account its integrated magnitude, size, and Hubble class.