Galileo and the Space Station

Although Galileo did not invent the telescope, his increasingly powerful instruments revolutionized our understanding of the vast universe.

Yesterday evening at 10:39pm in Tualatin, what would Galileo have seen through one of his early telescopes, with its 9x magnification? Well, there would be Jupiter, of course, with its four visible moons. And the Moon would soon rise, so he could examine the cratering.

But wait! What is that "star" moving majestically through the heavens, from west to east? Bright as Venus, what could it be?

"Quick, Mr. Galilei -- get your telescope! Oh, you didn't bring it with you through the Time Portal? Here, use my telephoto lens! It magnifies nine times; about the same as your newly-improved telescope. Still see only a bright dot? No problem; just push that button near your finger, and the image will be magically captured for later, additional study."

So, that's what "Galileo" did last night, and here is the result:



Okay, I suppose Galileo did not have a 10.1 megapixel image sensor on the viewing end of his telescope. Nor did he have the ability to magnify an additional 2x in a photo editor, or increase the contrast a bit. (You can click on the image for the original, full-frame shot.) But if he had, I wonder what Galileo would have thought about the gold-colored appendage?

"Oh, the golden tail Mr. Galilei? That's one of the celestial dragon's solar cell arrays." :-)

Saturn and Mars Together

Here is another quick lunchtime blog entry, to show the results of last night's shooting. Saturn and Mars had their closest conjunction for the next 14 years: only 0.25 degrees apart in the sky. (That's close enough to fit behind the tip of your little finger held at arm's length.)

First of all, here is how the images turned out separately (magnified in a photo editor); you can clearly see Saturn's rings, and can almost see some surface coloration on Mars' disk. Of course, much better amateur telescopic images of these planets exist -- but I'm impressed at what can be done with a simple telephoto lens!





Here they are together; click on the image to see a bigger view.



In order to show you any detail at all, I had to crop fairly tightly. (Click here for the original full-frame image.) The astonishing thing is that you can see Saturn's rings in the same shot with Mars.

Perhaps more incredible to me was what I saw by looking through my small Celestron telescope; I could see Saturn and Mars at the same time, without moving the telescope. That's something that doesn't happen every day! (Or year, or decade in this case!)

I mentioned in an earlier blog entry that someday I'd like to mate the camera with a telescope. Unfortunately, "someday" could be a long time in the future (probably never), since that would require one or two orders of magnitude higher time and resource commitment.

In the meantime, I'm thoroughly enjoying Casual Astrophotography.

Astrophotography With a Camera and Tripod

There have been some questions about the setup/procedure I used for the "Jupiter and His Minions" shot. So, I figured I'd do a quick lunchtime blog entry to describe the technique.



If you click on the photo above, you'll get the original, full-resolution image. The first thing you'll notice is that I did not see anything like the final picture in my camera's viewfinder. Instead, I saw a mostly black frame with a tiny white dot in the middle. Thanks to the Canon XTi's 10-megapixel resolution, a tightly-cropped view of the frame center shows the Jovian moons, in color.

In order to show the moons, it was necessary to significantly overexpose Jupiter's disk (ISO-800, 1/2 sec, f/5.6). Here is what it looks like when the picture is exposed for the planet's disk itself (ISO-800, 1/30 sec, f/16):



Notice that the disk appears much larger in the overexposed shot. This is due to one of the well-known problems faced by astronomers ever since the camera was invented: bright stars make bigger dots in an astrophotograph. Even though all of the stars have the same apparent size -- they are point-sources with no discernible diameter -- brighter ones "look" bigger in the picture. Although a planet like Jupiter does have visible width, overexposure makes the disk look bigger than it ought to be. Oh well.

Another tricky thing about astrophotography is getting the image in focus. It's harder than it sounds, since most lenses (even set for Manual) don't have a hard stop at "infinity." And when the target object is small and dim, it can be impossible to judge sharpness by eye. A camera's autofocus sometimes works, but not at the granularity needed -- and often it fails to lock on to a celestial object completely.

I used manual focus, aided by a modified Hartmann mask to create diffraction spikes. You can read about it here:

http://www.astronomy-pictures.com/Imaging-Tips.htm#focus2

On a bright point source (my bare maglight bulb), here is what it looks like when it's almost in focus; two images are coming together into one:



When focus is attained, twelve diffraction spikes appear radially around the point:



There is a saying: "In theory, there is no difference between theory and practice. But in practice, there is." When I used the technique on Jupiter, the spikes were a bit mushy, perhaps due to the fact that it was not actually a point source:



However, it got the job done. I suspect that Venus -- bright and small -- will work better with diffraction spike focusing. But that will be a different astrophotography adventure.

Tonight (July 10), I hope to capture Saturn and Mars on their closest conjunction for the next 14 years. They will be in the west, shortly after sunset.

Jupiter and His Minions

Jupiter is making its closest 2008 approach to Earth tonight. Last night I aimed my 300mm telephoto (480mm film equivalent) in the direction of the Jovian system, and captured the planet with four of its largest moons:



One of these days, I'll mate my camera to a telescope, and then I'll be a "real" amateur astrophotographer. In the meantime, I was surprised what could be done with a simple tripod and camera.

Fire Flowers

It's July 5th, which naturally falls after the 4th of July. I can imagine that the Flickr servers are chugging away at full speed, servicing the uploads from photographers who think their shots of their fireworks are better than those of a bazillion competitors out there.

Well, I have no illusions that my Fire Flowers from the Tigard fireworks display are better than others'. But one thing I can pretty much guarantee: they are unique. A gorgeous landscape scene will likely be photographed hundreds of times per year, and 95% of those shots will be nearly identical. The other 5% will be differentiated on some environmental thing like pretty cloud formations or a sunset. Sometimes, a creative photographer will find or make something different about the recorded scene. But it's still the same scene.

In contrast, firework photos are by their very nature unique. There is no well-defined start or stop of any given exposure, so each photographer will get something different from the same gunpowder blasts that light up the sky.

So without further ado, here is my contribution to the massive July 5th Flickr upload event. Click here or on the picture below to view a full-window slideshow of 25 unique Fire Flowers.