Sunday, September 20, 2009

Jupiter Again?

Looks like I'm a little obsessed with Jupiter. After recording all four Galilean moons with my D300 and 70-300VR hand held, I thought I was done with that planet. But tonight I got the bug to see if I could record a cleaner image of the moons. No idea why, but there you have it.

I started by bringing the tripod outside and hooking up the 70-300VR with VR off. VR can interact with the perfect stillness of the tripod to mess things up. This tripod is the Feisol 3471 and the ball head is the Markins M20L, for those who care about such things. The legs are not fully opened, the thinnest segments remain undeployed, which adds to the stiffness. There is no center column to transform it into a monopod, so this is about as good as it gets.

I attached the cable release as well so that I could use mirror lockup. That way, slower shutter speeds do not add a tiny amount of mirror shake since the mirror is taken out of the way and vibrations are allowed to settle before pressing the button to make the exposure.

So ... first thing, h0w many moons are visible tonight? Akkana Peck's Juplet tells me that I should see three moons and a shadow.

You can see that Callisto has moved to the other side of Jupiter. It is in a slow orbit, so it takes a week to get there I think. Io and Europa are visible, as is Europa's shadow. Ganymede is hidden behind the planet I suppose.

Anyway, the shadow won't be visible to me since I don't have that kind of resolution and I cannot do a time exposure (I don't have a tracking mount.)

I started with the 70-300VR at the same settings as last time, 3200 ISO, F8 and 1/20s. And sure enough, the very first exposure I got was pretty good. There is a lot of gunk around the planet that must be processed away using black and white conversion of specific colors, then levels and other filters. This is what was left, and it's better than the hand held one I think.

I tried other settings, but this was the best exposure from that lens. I then switched to the 300mm F4 AFS lens, which is somewhat sharper than the consumer lens. This one is sharp wide open, although I preferred the images I got with it stopped down a bit. It resolves slightly better at F8, and every little bit counts at around 600 million km.

The best shot I got from this lens at 3200 ISO was a little better and a little worse.

Better shape to the planet and moons, but slightly worse separation of Europa from the planet. Still, not bad.

Here I started playing with settings to lower the ISO. One thing I discovered is that there is not much point going below about 1/3s because the moons seem to fail to resolve at 1s ... looks pretty bad. So the lowest ISO I could reasonably shoot was 800. Still, that's a lot cleaner than 3200 and the result is very nice. The moons and planet are very round with nice edges, even after my heavy processing. Definitely looks like an astronomy image :-)

So there you go ... 300mm lens is more than enough to resolve the moons .. even when close to the planet as Europa was tonight. Go for it ... gotta say that it's pretty fun ...

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