The Bartels' Equation for Telescope Value

TV = A * F * fe,f,a * fu * fs * fx

Telescope Value = Aperture * FieldOfView * function(eyepieces,filters,accessories) * function(usability) * function(skies) * function(experience)

Telescope Value is the overall value of the telescope to me.

Aperture is so important that we amateurs talk about aperture fever. I can see more with a bigger scope: objects are brighter and more detailed. Yet aperture isn't the only factor...

Larger apertures have smaller fields of view. Many Milky Way objects such as bright and dark nebulae profit from a field of view of several degrees, whereas that one meter 40 inch telescope that we all lust after has a low power field closer to half a degree. Field of view trades off with aperture.

Eyepieces, filters and accessories function to enhance viewing, and sometimes are indispensable, for instance, a nebula filter in light polluted skies.

Usability or ergonomics sadly is often ignored. We don't think of the sore neck or strained back that can result from an uncomfortable eyepiece angle or lifting a heavy telescope into the back of a car. Well thought through ergonomics can enhance viewing: sitting on an astronomer's chair while observing allows me to concentrate on difficult details.

Dark skies with good transparency and excellent seeing can make all the difference. They allow small scopes to achieve what large scopes can show in light polluted skies. Rare nights of perfect seeing when astonishing magnification can be used stay with me for years.

The experience of the observer is a major factor. An experienced observer will see more with a smaller scope than a newbie with a larger scope.

What's your telescope value?

Mel Bartels