Light pollution as a light source

The other night was the first night in weeks where it wasn't cloudy. Of course, there was a mad scramble when Melbourne-based astrophotographers were all running outside to take photos. Naturally, I was one of them.

We couldn't run far though. The Melbourne Coronavirus lockdown prevented anyone from leaving their homes.

On the night in question, the Moon was about three quarters full (waxing gibbous, if you're into that sort of thing), and not far from Jupiter and Saturn. Mars was up later. The Helix Nebula was around half way between Saturn. and Mars, and the Sculptor Galaxy followed.

But imaging under moonlight is challenging, especially if you're after deep-sky targets like nebulas or galaxies. Moonlight washes out the really faint light from these targets, meaning the signal (nebula light) to noise (moonlight) ratio is really low.

You can drag out these details using many subexposures, or use light pollution or narrowband filters, but at best you'll get an image which still isn't as good as one you'd get at a dark sky site.

So I didn't go for the Helix or Sculptor. Instead I went for the dwarf planet Ceres. While I was doing that, I thought I'd also try something that took advantage of the moonlight, rather than fighting against it.

I used the light pollution as a light source.

This is when you use a long exposure to take photos in darkness, using different and unusual light sources. I'm no expert at this, but there are some who are masters at light painting (and I'm looking at YOU, Deanne!). In this case, the Moon was providing my photons.

I put the camera on the tripod, set the timer to take a series of 30 second exposures, and went back to watching Ceres.

The photo shows my "office", with me, my computer, mount and scope. The subtle moonlight is casting shadows downward onto the grass, but the fence is casting a shadow sideways. It's the neighbour's porch light which is also shining on the house behind.

Shadows can be a bit puzzling, really.