Jupiter – more magnified than ever before

I’ve photographed Jupiter before with my 5″ telescope. Its focal length is 1500mm which means Jupiter is quite small on my camera’s sensor when using the prime focus method. For Christmas, Hannah bought me a 5× Barlow lens which gives me an effective focal length of 7500mm. Now, Jupiter is 5× wider and 5× taller, and 25× greater in area on the camera’s sensor.

Unfortunately, there’s a catch. Nothing in optics comes for free, and tonnes of extra magnification comes at the cost of having an image that is much dimmer, significantly harder to focus and much more susceptible to vibrations from the wind, from the camera’s mirror and shutter, and from the motorised telescope mount.

It actually took me about 25 minutes just to line up the telescope with Jupiter and get it in focus. That’s a shockingly long time – Jupiter is the brightest object in the sky except Venus, and normally it only takes a couple of minutes to get the ‘scope centred and focused on such a bright object. The focus isn’t perfect, but the focus is incredibly sensitive at this magnification and every time I touched the focus knob, the telescope took about 30 seconds to settle down again.

So this is the highest digital resolution photograph I’ve ever taken of Jupiter, but the optical resolution is worse. I think with a bit more practice, I could improve on this.

  • Celestron NexStar SLT 127 with 5x Barlow, f=7500mm, Φ=127mm, f/59
  • Canon 600D, ISO 800, ¼s, composite of 11 frames
  • Unsharp mask applied in post; no other processing

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