How to configure your telescope and camera for an object in the sky

Simply grabbing a telescope and a camera to shoot any object in the night sky is quite a bit of a gamble. Most likely the object will be to small or it won't fit in your view and that is exactly what this is about: the field of view or 'FOV'. You need to get your optical train in order. In other words you have to fit the scope, the lenses (barlows and reducers) and camera (size of the pixels) together with the size of the celestial object expressed in 'Arc seconds'.

This sure is a challenge as some objects are quite large like the Andromeda Galaxy. To the naked eye this 'M31' is a faint star. But the actual size is 6 times that of the full moon! Bernards Loop which is a sort of a borderline just east of Orion is as large as Orion itself and a telescope is therefor not your optic of choice which rather is a normal camera with something like an 85mm lens.

So... where to start?

Speed of telescopes by The Space Koala.

How to read, interpret and understand camera specifications: this explanation by Cuiv.

Camera pixels per focal length by Sky Story

Then start with this explanation by Cuiv.

And the calculator that he refers to.


Three different fields of view, my scope only,my scope with the 0.7 reducer an my scope with the Hyperstar V4.


Play with it yourself