Monthly Archives: July 2013

I’ve written four posts now on Simple Astrophotography (here, here, here, and here) which use only basic camera equipment that an advanced amateur photographer might have already in hand. The equipment list so far hasn’t included anything other than a modern DSLR (I use a Canon, you could use a Nikon, Sony, whatever), a tripod, a telephoto lens, and a little bit of knowledge about what to look for and how to shoot it.

Now let’s up the game a little bit and start Intermediate Astrophotography using a small telescope. Here’s last night’s setup:

This is my current “little” telescope, a 5″ Meade ETX-125EC, a Muskatov design telescope.

As you can see in the top picture, it’s portable (more or less) with a heavy-duty mount. The whole thing weighs about forty pound or so. “Luggable” might be a better term than “portable”, but it’s easy enough to take out on short notice to set up on the sidewalk out front. For accurate use and more advanced stargazing and astrophotography a precise alignment is necessary with the yoke (seen going from about the 8 o’clock position to the 2 o’clock position in the bottom picture) pointed straight at Polaris, the North Star. If that alignment is accurate and you power the motor in the telescope mount’s base, the telescope will stay aligned with the stars as the Earth turns. For last night’s work, just “eyeballing it” was fast and “close enough for government work”.

This particular telescope is about a dozen years old. The current models in this size with the heavy-duty mount run a bit less than $2,000. That’s why I don’t expect everyone to have one sitting around in the garage – but if you want to get into this sort of thing, it’s not an outrageous amount either.

My Canon DSLR will be attached to the telescope using an adapter ring that you can get for about $20 or $30 from any good camera or telescope store. (If you don’t know one, I would recommend Woodland Hills Cameras & Telescope – and every type of DSLR has a different adapter ring, so make sure you get the right one for your camera.) The adapter ring screws into a connecting tube, where the thick portion of the tube can hold an eyepiece for more magnification (that’s advanced astrophotography, not intermediate) and the narrow portion fits into the telescope where the eyepiece normally goes.

For last night’s beginning work, I first wanted to shoot something big, bright, and easy to focus on, i.e., the moon. (I knew how to do all of this twenty-five years ago, but it’s been a while, so we’re revisiting the learning curve just a tad here.)

But first…

Very pretty, but not good for photographing the moon. On the other hand, considering how bad it looked in the east, north, & south, these clouds in the west weren’t bad. Even with the clouds skipping over the moon and hiding it from time to time, I was able to get the telescope lined up and make sure that the finder scope (seen with its eyepiece sticking off at a 90-degree angle to the left side, above) was properly aligned.

Then it was time to take a couple of quick pictures the “simple” way, using just the telephoto lens, for reference:

Using the telephoto lens at 70mm, you can see the crescent moon, three days old and 13% illuminated.

Using the telephoto lens at 300mm you can start to see a bit of detail, maybe a few craters or maria on the terminator. However, the moon only fills a small fraction of the frame of the picture.

As it got darker and I started to try to use the telescope, of course, the clouds got thicker. At first I was getting nowhere with the DSLR attached to the camera, so I took the camera off and put in a 25mm (low power) eyepiece. Even with the clouds drifting in and out, this will give you a gorgeous view of the moon, the moon’s disk just about filling the low-power field of view through the telescope.

It occurred to me that there was an intermediate intermediate step before I got the DSLR camera working correctly on the telescope. And you can try this (with the telescope owner’s permission in advance, of course!) if you’re at a star party or someplace where someone has set up a telescope, or even a pair of binoculars.

With the telescope focused and aligned, I tried simply holding my iPhone camera up to the lens and seeing if the iPhone would see what my eye saw and photograph it:

To my surprise and amazement, it sort of did!

You’ll notice that the image shows some serious vignetting, where the full frame of the iPhone photograph only picks up a central, circular image from the telescope eyepiece. (You’ll also notice that there was a wisp of cloud across the top third of the moon, from center left to upper right.)

But you can also see a lot of detail, especially along the terminator. I was surprised, but pleased that I at least had something to show for my efforts!

Then the clouds cleared a bit, I put the camera back on the telescope, figured out what I had been doing wrong, and finally:

1/30 second exposure

1/60 second exposure

1/25 second exposure

The focus was pretty good, although it might get better with more practice. You can see how these three shots with slightly different exposures have different tradeoffs between overexposing the bright limb and underexposing the dark terminator line. When shooting pictures of the moon, you’ll have a huge dynamic range to deal with. (Again, DIGITAL PICTURES ARE CHEAP! These were the best three of dozens and dozens of pictures taken, bracketing the exposures both darker and lighter.)

And finally, not the most in focus or well exposed picture of the night, but possibly the luckiest:

1/30 second exposure, but what’s that little red line on the left? (You will probably have to click on the image to view or download the full-sized picture.) Odds are that it’s a 747 headed from Dallas to Honolulu, about 250,00 miles closer than the big planetary body in the background.

That was great! Will it be clear tonight? I’ll let you know tomorrow.

Two months ago I write three articles (here, here, and here) about some simple and easy ways to use little more than a digital camera and a tripod to get some pictures of comets, the stars, and the ISS as it flies by overhead.

Last month I gave everyone a heads up about Saturn and the moon being near each other in the evening sky, making Saturn easy to find for even the novice backyard astronomer. I took a bunch of pictures that night (of course!!) and wanted to share with you, especially since a similar viewing opportunity will be coming up in mid-July.

First I was simply taking pictures of the waxing gibbous moon using my Canon Rebel Xt DSLR and a Tamron 70-300mm telephoto zoom lens.

(Click on any image to enlarge & see the full-sized image.)

A telephoto lens of this size won’t let the moon fill the frame, but it’s more than big enough to let you see considerable detail. It’s critical to get your focusing correct. You can try to let the camera autofocus to get you in the ballpark and I’ll take a few pictures using autofocus, but I always try to take most of my pictures focusing manually to get it perfect.

You’ll need to bracket a number of pictures to get the exposure correct on the moon. Remember the rule – “Digital photographs are CHEAP!” The moon will be far, far brighter than your camera thinks it is, while the camera’s light sensors will try to average over the whole frame to set the exposure if you’re in full automatic mode. So full automatic mode will give you pictures of the moon way, WAY overexposed, just a huge white blob.

For example, on this night the camera on full automatic mode wanted to do exposures in the 1/30  second and 1/60 second range. I shot bracketed exposures all the way down to 1/500 sec and then double check, only to be amazed that they were still seriously overexposed. This picture was taken at 1/4000 sec at f5.6, the fastest the camera will go.

You may be photographing an object in a really dark, black sky, but it’s really bright, especially as you get closer to full moon.

I tried to take pictures of Saturn with this lens, but at 300mm it’s just not big enough to show any detail. Saturn here is the bright dot just above center, but the only thing making it look like it’s bigger than a dot is a slight vibration in the camera during the 1/3 second exposure.

So, given that 1/4000 sec was good for the moon and 1/3 sec was good for Saturn, how does one go about taking a picture of the two of them in the same frame?

Unless you’re using Photoshop, it’s tough. Getting Saturn to show up at all will guarantee enough glare from the moon to wash out the frame, while exposing for the moon will leave Saturn lost in the gloom. Also, for most lenses, if you put the moon anywhere near the center of the picture you’ll get horrible ghost images from the internal reflections in the lens. The lens flare seen above is one thing (think JJ Abrams!!), multiple ghost images across the frame are another.

The next step for me is to try to go beyond “simple” astrophotography into what we might call “intermediate” astrophotography, using telescopic gear that the average person won’t have just lying about. We’re not talking about tens of thousands of dollars in gear here – it’s absolutely amazing what you can get for $1,000 or less, telescopes that would have cost twenty or fifty times that just twenty years ago. Still, it’s not “simple”.

I hope we’ll get to that later in July.

One final extremely simple astrophoto that you can take, which I spotted at the Angels game on July 4th. If you go out just after sunset these days and look to the west-northwest you’ll see a really bright object sinking toward the horizon an hour or two behind the sun.

That’s Venus.

Way above the roof of Angels Stadium you see two big, blobby, ghostly images – those are reflections of the lights under the roof. But just a smidgen above the center of the roof, right over a green stanchion or support sticking up, you can see a clear, bright pinpoint.

Voila! Even in the glare and lights of a fully illuminated baseball stadium, you can spot (and photograph) Venus.