Monthly Archives: July 2013

I know that we’ve started on some more advanced (intermediate) astrophotography, but I ran across some photos from last year and realized that there’s another simple astronomical object that can be easily photographed.

The sun!

Unlike the moon, constellations, aurora (which I’ve never seen in person but would kill to get to see and photograph!), and satellites, photographing the sun has the potential to be dangerous. It goes without saying, but I’ll say it anyway: DO NOT LOOK AT THE SUN THROUGH YOUR CAMERA! ESPECIALLY DO NOT LOOK AT THE SUN THROUGH A TELEPHOTO LENS!! EVER!! NOT EVEN ONCE!!! YOU’LL SERIOUSLY DAMAGE YOUR EYES AND POSSIBLY GO BLIND!! (Not that other kind of “you’ll go blind” either, this is the real thing, physics and science and all of that, not moral guilt and BS and bullying.)

That doesn’t mean that you can’t take photos. You just need to be clever.

First, you need to block out about 99% of the light from the sun. It’s possible to do this with a fancy solar filter and in fact you can get such filters for telescopes like my 5″ Meade ETX-125EC, but they’re expensive. I’m still talking “simple” here.

You can get one of these from any astronomy or telescope store for about $1. (If you wait until the day before an eclipse or the day of an eclipse, it might be $10 – if you know what I mean.) Coincidentally, it’s just about the perfect size to cover the front end on my 70mm-300mm Tamron zoom lens. I simply taped it on with a couple tiny tabs of duct tape.

Make sure that it completely covers the lens – even the tiniest bit of stray full-intensity sunlight will ruin your day and possibly your camera.

To aim at the sun, put your camera on a tripod. Point the lens (covered with your cardboard and mylar “Solar Viewer”) at the sun.

I’ll repeat one more time: DO NOT LOOK THROUGH YOUR CAMERA AT THE SUN, EVEN IF YOU HAVE YOUR $1 SHIELD COVERING THE LENS! EVEN IF YOU THINK IT’S OK, IT’S NOT. YOU’RE STILL GETTING MAGNIFIED AND FOCUSED UV LIGHT SHOT STRAIGHT INTO YOUR EYEBALL. OH, AND DID I MENTION — YOU’LL GO BLIND!!

If you have one of the newer DSLR’s that actually shows an image on the back like an iPhone or camcorder does, this is a piece of cake. While you shouldn’t ever look through the lens at the sun, looking at an LCD display on the back of the camera is completely safe. Just “eyeball” your pointing, then refine it by looking at the LCD display.

If you have an older DSLR (like I do) where it only uses the LCD display on the back to show you the picture after you take it, aiming is a bit trickier, but still pretty easy. “Eyeball” your pointing, then look behind you at your shadow. If you can see the shadow of the lens, you’re still not pointing in the right direction. Move the tripod until you minimize the size of the camera’s shadow, meaning that you have it “square” to the sun. Shoot a picture and then look at the result on your LCD display – adjust accordingly. Easy peasy!

The mylar solar filter will make the sun’s image look very orange. No worries. As for the size of the sun’s image in the frame, it will be EXACTLY as big as the moon’s image is from when we were playing around with taking pictures of it with the same lens and camera.

This makes perfect sense if you think about it – what happens during a full solar eclipse? The moon passes directly in front of the sun and we see the solar corona because the angular size of the moon and sun are exactly the same. Right? (Yeah, yeah, annular eclipses, blah, blah, blah. Close enough for government work!)

So does it work?

Yes! Yes it does. These pictures were taken on June 5, 2012 when a very rare event, a transit of Venus, occurred. How rare? Transits of Venus occur in pairs eight years apart, and this was the second one of the pair that occurred in 2004 and 2012. The previous pair were in 1874 and 1882, while the next pair will be in 2117 and 2125.

That rare.

So, that black dot that you see at about the two o’clock position? That’s the planet Venus silhouetted against the face of the sun.

Of course, it’s moving. It can take hours to cross the face of the sun. From Los Angeles I took pictures from about 17:20 to 19:25, at which point the sun was setting. Then, to prove that it really was moving (I don’t think NASA really needed my proof, but it’s a nice little exercise to do anyway.) I took five frames covering that 2:05 period and put them together using Photoshop.

All with my off-the-shelf camera, tripod, telephoto lens, a $1 mylar card (OK, it was $5 ’cause I waited until that morning) and a little bit of caution and cleverness.

POP QUIZ: What should you never, EVER do because it really, REALLY will make you go blind?

Very good. You get ice cream.

I need to go find some aurora some day.

Yesterday we talked about the first efforts to take astrophotos with the camera attached to a small telescope, essentially using the telescope as a honkin’ big telephoto lens. Last night I tried again using the same setup with the moon a day further along in its monthly cycle.

Here you can see the camera attached to the telescope, with the small finder scope just to the left of the camera.

There were still clouds in the area, very pretty and pink and cotton candy like, but a pain for this kind of work.

(Click on the images to view or download the full sized versions.)

The southern limb of the moon. On all of the pictures here (as with almost all astrophotography) south is up, so the pictures appear to be flipped compared to maps. There are all kinds of good lunar maps online if you would like to play along.

When these pictures were taken, the moon was 21% illuminated, four days and twenty hours past new. This picture was a 1/60 second exposure and slightly blurry due to vibration.

The large, round, flat area just to the right of the terminator and just above the bottom of the picture is Mare Nectaris. The large crater sticking up (to the south) out of it, half open, is Fracastorius, approximately 124km wide. The crater just above (south) of that with the really nice central peak just being illuminated is Piccolomini (88km).

A 1/100 second exposure. In the center, below (north of) Mare Nectaris we see Mare Tranquillitatis, the Sea of Tranquility, where Apollo 11 landed in 1969. The large, circular area near the limb below (north) of that is Mare Crisium. The two prominent craters near the terminator at the very bottom (north) are Aristoteles (87 km, nearly fully illuminated) and Eudoxus (67 km, rim illuminated but floor deep in shadow).

Not fantastic, not spectacular, but not bad for two nights’ work. Still plenty of room for improvement, but to a good first approximation it’s working!

What’s next? Well, not too far above the horizon, about twenty or thirty degrees to the north of the moon there’s this really, really bright object. What is it?

This is a 1/100 second exposure, so even with all of that dark night sky there this is a bright object, but much smaller than the moon. Yet it’s not quite a pinpoint, seems to have an actual discernible structure or form.

If we isolate the central image we can see that it appears to be showing phases, much like the moon does. But no other detail, no surface features.

Of course we know what it is (Venus), but did we actually photograph it correctly, seeing the phase and not just some random jiggle in the telescope rig, smearing a stellar pinpoint into something bigger? For confirmation, let’s go to a really neat website run by the US Naval Observatory:

This is a computer-generated image of what Venus should look like at the time that my picture was taken. It most certainly appears that for the first time I’ve gotten a good photography of Venus!

Clouds permitting, we’ll continue to watch the moon as it heads toward full moon on July 22nd. It’s amazing how features can vary so widely on how they look as the lighting and shadows change. A couple hundred years ago, using telescopes less powerful than the one I’ve got and with no photography, these kinds of observations and measurements gave astronomers the first accurate idea of how big the craters and mountains of the moon were.

As far as Venus is concerned, Galileo’s observation of the phases of Venus (and Mercury) were a key point in the evidence that the sun was at the center of the solar system. (Planets inside our orbit show phases while planets outside our orbit do not. Simple geometry from there.) While the Catholic Church forced him to recant in order to avoid being burned at the stake as a heretic, the facts and the evidence remain.