When last we left our plucky hero (i.e., me) we had spotted Comet Lovejoy and managed to get a couple of blurry photos of it. There was considerable room for improvement.
Last night I went out and spent some time playing with the manual focus on the Tamron 70-300mm zoom telephoto lens that I’m using on my Canon Rebel xT camera. Eventually I got better (leaving more room for improvement yet) by concentrating on bright constellations, such as the Pleiades and Orion. Eventually I ended up with this (remember, click on any image to get the full-sized version):
This is an eight-second exposure at 70mm. The “belt” of Orion is in the upper left corner (three bright stars in a row) and you can just see the Orion Nebula (the middle star in the “sword”) at the far left edge, right about in the middle. Minimal blurring, which is good. No comet, which is bad. On January 3rd, it would have been visible in the lower right corner — but of course, it’s moving (up and to the right in this view), so it’s now out of the frame.
It wasn’t that hard to find, pretty easily visible in just a few seconds through binoculars. This is another eight-second exposure at 70mm. Unfortunately, despite my practice earlier in the evening, all of my 300mm exposures (and we’re talking a couple hundred here) were all out of focus and trash. (Frustrating!)
Again, if you’re looking yourself (and you should be, assuming you’re not in one of those places with -40°F temperatures tonight), it will just be a hazy, grey or white patch through binoculars, almost like a vague and dim cloud. Sorry, the human eye doesn’t have enough receptors to see it like a camera can and give you that bright green glow that you see in pictures. For example, that picture is from a 12″ telescope in dark skies with almost 18 minutes of exposure on eight frames combined. Compared to that, your eye doesn’t stand a chance!
Tonight we have scattered clouds that are getting thicker as the evening wears on. I managed to get this eight-second image at 81mm…
…and this one (also eight-seconds at 81mm), both of which clearly show the green comet as a small, fuzzy ball. Both of these images are in pretty good focus, but the stars are a tiny bit blurred because of “trailing”. I’m using the camera on a fixed tripod, but the Earth is moving, so in a longer exposure the stars look like little streaks. For example…
…compare this image to the first one above. This is the 30-second exposure taken in the same set as that 8-second exposure, and you can see how all of the stars are little arcs/lines going from the upper left toward the lower right. Proof that Galileo was correct — the Earth DOES move! (The “fix” for this is a telescope mount which is designed to counter-rotate at the same rate as the Earth does, so if it’s aligned correctly, the stars stay motionless relative to the camera. But I didn’t want to go to all of the effort tonight of hauling the big scope out and setting it up in the yard. Maybe after these clouds clear in a couple of days.)
Now, it’s 22:46 PST — let’s save the draft of this and take go back out to take one more shot tonight at getting some 300mm shots that don’t suck.
23:16 PST — The good news is that I got some 300mm images that are in much better focus than before. The bad news is that I wasn’t pointed at the comet.
You can’t actually see the faint, fuzzy comet through the camera viewfinder. You can only the brighter stars that way. Also, with the lens zoomed in like that you’ve got a much smaller field of view. So I sort of get it “close” to where I need to be, then take sets of pictures in a “search pattern” — sort of like playing “Battleship”. But midway through the first set the clouds rolled in with a vengeance. Right now you can’t even see the moon except as a brighter blotchy area in the thickening clouds, so I think that’s it for tonight.
But the next clear night, we’re going to kick that comet’s ass!