Well after last night’s astrophotography session with a 400mm f/5.6 lens, and 3× teleconverter, I decided to try again with an even longer optical system.
I rummaged a 700mm f/11 telescope and used the same 3× teleconverter, for an effective focal length of 2.1m. This provided almost twice the magnification of last night’s setup, albeit with a much more unwieldy telescope which is extremely difficult to aim accurately, and takes about 30 seconds to stop wobbling after I adjust it.
As you can see, this image is larger than the previous attempt. If I want to improve further, I will need all or any of the following:
- A lens with greater magnification, to achieve greater resolution on the sensor
- A faster lens. At this magnification using a shutter speed any slower than 1/30 causes Jupiter to be blurred
- A camera with a higher pixel density sensor, to achieve greater resolution
- A motorised tracking tripod, to ease the process and to allow me to shoot slower than 1/30 and collect more light
- A camera with a lower-noise sensor. I’m using a several-years-old Canon 450D, which is not renowned for its high ISO performance
All of these are expensive, so don’t hold your breath 😉
Jonathan Gazeley 