Imaging Mars near opposition

Mars is a small, unforgiving target. Even near opposition the disk only grows to around 17 arcseconds, and the surface contrast is low enough that bad seeing erases everything. After a full season of trying, here is what actually moved the needle.

1. seeing beats aperture

I spent a long time wishing for a bigger scope. The truth is that on most nights the atmosphere, not the optics, sets the limit. A 4-inch refractor on a steady night beats an 8-inch on a turbulent one. I learned to check the jet-stream forecast before bothering to set up.

2. lucky imaging

The whole game is capturing thousands of frames and keeping only the sharpest few percent. I shoot 90-second runs at high frame rate, then stack the best 5–10% in AutoStakkert. Longer than 90 seconds and the planet's rotation starts to smear surface detail.

capture:  ~3000 frames / 90 s
keep:     best 8%
stack:    AutoStakkert (drizzle off)
sharpen:  light wavelets, stop early

3. derotation

If you want more signal, capture several runs and derotate them in WinJUPOS before combining. It feels like cheating, but it is just undoing the planet's own spin so the frames line up. Syrtis Major finally showed up cleanly once I did this.

misc.

Two things I keep relearning:

• Collimation matters more than I want it to. A slightly miscollimated scope throws away the sharpest frames first.
• Resist the urge to over-sharpen. The wavelet sliders are a trap; stop while it still looks like a planet and not a coin.