How I Fine Tune Focus on Jupiter

Starlog November 4th, 2023, 11:23 p.m. local time

I missed the actual Jupiter opposition by a few days, due to weather. But Saturday night had very clear skies, so I waited until near midnight to photograph the planet.

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When I started photographing the planets, circa 2016-2017, Jupiter was low in my South sky, relatively speaking, here in the Northern Hemisphere. Each year, the planets and particularly Jupiter have etched higher into the sky. This year, 2023, Jupiter, almost feels like it is around Zenith. I am sure this is due to the tilt of the Earth and the North Pole “pointing” more into the direction of outer planets, away from the Sun, during Winter.

Nudging my manual Dobsonian telescope for each short movie capture is a greater challenge with the scope pointing nearly straight up. Bending down to read the finder has always been tough. Getting clearer images, though, is a worthy benefit when the target object is so high. Trade-offs.

Last year, I started using Canon’s software on my MacBook to get more precise focus on the planets. The large screen is particularly useful for the largest planet, making the task almost easy. I just need to (1) crank up the ISO to maximum temporarily on the camera and (2) get the sharpest image possible on the smallest visible Galilean moon. This allows for generally crisp final images, even with a manual Dobsonian and entry-level DSLR camera, as the accompanying image here demonstrates.

The black dot on Jupiter’s surface was Io’s shadow.

Summary of my equipment, settings, and software used:

• Telescope: Dobsonian reflector 254mm / 10″ (homemade)
• Camera: Canon EOS Rebel SL3
• Barlow: TeleVue Powermate x5 1.25″
• Filter: Baader Neodymium 1.25″
• Canon T ring and adapter
• Relevant camera settings:
• ISO 200
• Exposure: 30
• HD video at 60fps
• Created from eight videos of about 30s each, best 35% of frames (via Autostakkert)
• Software for post-processing:
• PIPP
• Autostakkert
• Registax 6
• PaintShop Pro for minor touch-ups

Thank you for taking the time to read my article.