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Tuesday, July 1, 2014

Vacation Quest #1: Astrophotography

One of the quests I've set for myself this vacation is to work on my astrophotography. I've a 20-year-old Meade 16" Schmidt-Cassegrain telescope and a three-year old Canon EOS 60D DSLR camera. I've had occasion about four times in the last three years to couple the two together and attempt to shoot things in the night sky. I've had some decent luck photographing the moon, but planets and deep space objects still vex me. With planets, they are so frigging bright that they typically come out as nothing but bright blotches. Any detail is completely washed out on any timed exposures. As for deep space objects, the issue there is tracking - and to a lesser degree exposure time - but exposure time is a non-issue if tracking is broken. The telescope I have does not have an equatorial mount. All tracking is done by altazimuth.

[caption id="attachment_3139" align="alignright" width="512"]Telescope Mounts Telescope Mounts[/caption]

Here's a little picture to help you out with understanding the issue here. With the altazimuth mount, tracking is accomplished with very small horizontal and vertical stepping. If you plotted the tracking on a piece of paper, it'd look like a staircase. Therein lies the problem. All nighttime lights transcribe an arc across the heavens except those very close to Polaris, the northern star. They go in circles. Over a relatively short period of time, altazimuth tracking breaks down causing the object you are trying to track to leave streaks as the telescope tracking deviates from the arc of the object. The equatorial mount avoids this issue by inserting a wedge below the telescope. The wedge is set to your latitude. Once set, it allows the telescope to track in an arc, perfectly matching the rotation of the Earth.

The other thing causing me some grief is the EOS 60D is limited to a 30 second exposure. Deep space objects like planetary nebula that "shine" in reflected light require a longer exposure. Other deep space objects like large galaxies require less exposure time, but more is usually better. Things like globular clusters require the least exposure time, but for really nice results you want most of a minute to collect light. I get 30 seconds, so I make do with what I've got. I could replace the ROM on my camera with something like Magic Lantern, but I'm not quite ready to take that risk with such an expensive piece of equipment.

Telling you all that is not some form of making an excuse. Some quests are harder than others. In the span of two nights I took over 100 astrophotos, and I threw all but four of them out. They were just that bad. But being completely honest, I'm a real noob when it comes to astrophotography. Hell, I've only gotten back into photography in general the past three years. It's a learning process but it's a fun process. So I'm going to share the four I kept from this past weekend. Friday was the new moon, so this weekend was an excellent time to try to capture some deep space objects! Also, if you click on the image it will take you to the full size image in my Flickr account. Be warned, they are LARGE. There you can see all the settings for my camera. Feel free to peruse my other photos while your there. It'll prove that I may have always been a gamer, but gaming isn't all I do. ;)

[caption id="attachment_3150" align="aligncenter" width="1291"]Polaris Polaris[/caption]

The first thing I'm start with is the last thing I shot. This is the star Polaris, which I mentioned earlier. It's the north star and the end star in the handle of the Ursa Minor, the Little Dipper. I include it as a reference to what a "bright" star looks like through my rig. Polaris is not the brightest star in the sky. It pales besides Vega, Arcturus (the two stars I used to align on both nights,) and Sirius, the brightest star in the northern hemisphere. Polaris is in fact the 47th brightest star in the Northern Hemisphere with an absolute magnitude of -3.64.

[caption id="attachment_3152" align="aligncenter" width="1293"]M4 M4[/caption]

The second astrophotography I want to show you is M4. The 'M' stands for Messier, one of the first catalogues of deep space objects. This is a globular cluster. These are groupings of tens of thousands of typically very old stars that reside just outside our own galaxy. You can recognize them in your telescope by one easy description. They look like snowballs in space. This particular cluster looks more open than many because it is the closest globular cluster to the Earth at 7200 light years distance. I got it with a 15 second exposure Saturday night.

[caption id="attachment_3148" align="aligncenter" width="1298"]M80 M80[/caption]

This is another Messier globular cluster. It shows the snowball in space description really is an apt one. All those faint stars in the center cluster are part of it. M80 is about 11,700 light years from Earth. To really get it to stand out I'd need a longer exposure time, but I'm fairly happy with this result. :)

[caption id="attachment_3149" align="aligncenter" width="1306"]M82 M82[/caption]

But the astrophotograph I am most pleased with is this capture of the galaxy M82. You may remember having seen this galaxy in the news in late January and February when a supernova was spotted in what is the lower half of this astrophoto. I am particularly pleased with how well the dust lane, that diagonal band cutting across the disk of the galaxy, shows up. That is the hallmark signature of M82, and I'm surprised a 30 second exposure got it so well - relatively speaking. Have a look at the Hubble picture if you want to see M82's full glory. This is also the furthest object I shot at 11,420,000 light years from Earth. :P

And that's Vacation Quest #1 - at least for now. Right now I'm embarked on Vacation Quest #2. I actually set this post up Monday night with a scheduled post date and time. As I'll be literally in the field all day, don't expect anything from me on Wednesday. It will be a long day. Unless it's really super cool and I just can't contain myself. So who knows. Hopefully I'll have something good to report regardless. Cheers!

3 comments:

  1. Some of objects in that Polaris picture look greenish to me. Since there are no green stars I prefer to interpret this as evidence for rogue terraforming machines aka Alastair Reynolds' Greenfly.

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  2. Sorry to disappoint, but star come in many colors, including greenish. However, this is not a completely true color image. The night sky is not actually black. It is a ruddy chocolate brown. Our eyes simply can't pick up that faint background glow, but the camera does. So in processing I must white balance to make it look "normal" and that shifts the colors a tad. That said, I like your explanation batter. :P

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  3. That's an interesting thing to do. I hope you are able to gather some nice shots and maybe you share them with us.

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