Astrophotography upgrade: larger telescope or new camera?

Thinking of a larger telescope for astrophotography? It might be time for a camera upgrade instead.

Telescope and star trails. Credit: Pat Gaines / Getty Images

At the SolarSphere 2020 virtual star party event, astrophotographer Gary Palmer and I, along with several other BBC Sky at Night Magazine contributors, were part of an ‘ask an astronomer’ session held over Zoom, and something Gary said about astro imaging equipment piqued my interest.

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Gary pointed out that in theory, once you have a telescope then the only thing you probably need to change, if you are an astro imager, is the camera, as its sensor size can affect how much of your view you can image.

A full frame sensor is likely to image a wide view whereas using another with a smaller sensor will only see the inner part of the view: almost the same as changing eyepieces.

So rather than upgrading your telescope  it might be worth looking instead at what cameras you are using and get a range of cameras/imagers to provide a wider range of imaging scales.

Altair Astro GPCAM2 290C colour camera
The Altair Astro GPCAM2 290C colour camera. Credit: BBC Sky at Night Magazine

You can see the effect of how different sensors provide different views with a telescope by using many of the popular planetarium and sky mapping apps available.

I use several, including Stellarium on my PC and Sky Safari Pro on my iPhone XR and iPad.

I can programme in the telescope focal length and camera  sensor sizes and have overlays showing what each sensor will image using a particular combination.

It’s also useful for planning what camera to use depending on the size of the target.

For more on this, read our top tips for using Stellarium.

A diagram showing the scale of the fields of view acquired with a Canon DSLR and a GPCAM. Credit: Paul Money.
A diagram showing the scale of the fields of view acquired with a Canon DSLR and a GPCAM. Credit: Paul Money.

For example, as a rule I wouldn’t use my Canon EOS 50D DSLR to image Jupiter if I wanted detail on the planet. The field of view when coupled with my StarGate 500 is quite large, making Jupiter appear quite small.

Compare that with my GPCAM 290C camera which, using its full sensor size, gets much closer, and has the option of selecting a region of interest even smaller to pick up more of the planet’s detail.

It also has the added benefit of smaller download size!

So, the next time you get aperture fever and wonder about getting a larger telescope for imaging, perhaps instead think of adding a different camera instead.

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Paul Money is BBC Sky at Night Magazine’s Reviews Editor. Read more of his stargazing tips at Astrospace.