The Great Conjunction – December 27th

The powers that be at the National Weather Service and on all of the local television stations said that it would be completely cloudy today, and starting to rain by 21:00 tonight.

As Reagan said, “Trust, but verify.”

It was clear and a million just after sunset. They’re still saying the rain’s coming, but it wasn’t anywhere in sight tonight, so it was time to get the camera back out.

As you can see, they’re each getting lower toward the horizon every night as they both move to pass behind the Sun from our viewpoint. Saturn (dimmer) is now below Jupiter (brighter) and you’ll need to hustle out after sunset to see them before they set.

(Reminder – click on the image to see it full sized.) Up close you can see all four Galilean moons on Jupiter, even though it might look like just three. Ganymede is on the upper left, Callisto further out on the bottom right, and Io and Europa almost next to each other between Jupiter and Callisto.

These are some of the best pictures I’ve taken with this lens and camera, nice and sharp, so you can actually see that Ganymede and Callisto are pinpoints, while the Io-Europa pair is extended along the orbital plane. There’s not quite enough resolution to separate them, but you can see where they’re different than the two separated moons.

I’m very pleased with the quality of these images. Tonight’s imaging sees the first benefits of two major improvements that I discovered while actually reading the camera manuals yesterday. (Yeah, I’ve had the one camera since Christmas 2005… The fact that I can be an idiot is not breaking news.)

First of all, I always thought that when I was in full Manual mode for astrophotography that the lens would be wide open, that is, at its widest aperture. WRONG! It seems that it’s set at whatever it was last set at, which may or may not be wide open. But there’s a way (not a particularly easy or intuitive one) to manually set the aperture after you’ve manually set the exposure time. I found that most of the conjunction pictures that I’ve been taking for the last month have been at f5.6, where the lens can be opened up to f4.0.

For the non-photographers, that means that I can get the same light and brightness and exposure with a 1/2 second shot as I had been getting with a 1 second shot. That in turn means that I can have less trailing as the planet moves and jiggling as the tripod might move. This is all good.

Secondly, I found that there’s a way (again, not a particularly easy or intuitive one) to lock the mirror up before taking a picture. Normally in a DSLR camera there’s a diagonal mirror between the lens and the sensor. The diagonal mirror is how you see through the eyepiece as you’re setting up and focusing your picture. When you push the button to take the picture, in one motion that mirror snaps up out of the way, the shutter releases for a fraction of a second to take the picture, and the mirror snaps back down into place.

In “normal” photography, the shaking of the camera by this mirror movement is infinitesimal and insignificant. When doing astrophotography, it can make a huge difference, vibrating the camera and smearing out the detail in the very delicate and faint image. Not good. But now, instead of simply pushing the button, I’ve discovered how to activate the mode where pushing the button locks the mirror up out of the way and then a second push of the button releases the shutter and takes the picture, after which the mirror locks back down.

It was a bit disconcerting at first – the manual really doesn’t say how this works and I didn’t see any mention of needing to push the button twice, so at first I was convinced that I had done something to break the camera, which would have really pissed me off, but which would have been totally on-brand for 2020. But fiddling with a bit I realized what was going on and got into the rhythm of clicking the button, waiting a second for the vibrations to die down, and then clicking a second time to take the picture.

Maybe it was just dumb luck – but maybe not. Something is responsible for a very noticeable difference in tonight’s pictures versus the rest of them that I’ve been taking this month. We’ll see if the results are consistently better as I take more pictures over the next few weeks.