[Plamadude30k]

Astronomers consider anything >.5 degrees to be pretty wide field. The detector I’ve been using has a field of 9.7 arcminutes on a side, or ~0.02 square degrees. Basically, hold the head of a pin at arm’s length. That’s considered a fairly normal field of view.

[Plamadude30k]

Nicely done, Farktographer. I like how the trees ground the photo–I find you really need something interesting in the foreground in wide field astrophotography to really make a good image. Even just a few trees can improve it greatly.

[Plamadude30k]

I almost forgot to post this week! Nice work, everybody.

[Plamadude30k]

http://gplus.to/plamadude30k

I was really reluctant to join-facebook is a bit tiresome, and I just don’t feel like I need more of that. Still, I do like how they’ve built it around ‘circles’-it makes a modicum of sense.

[Plamadude30k]

My buddy did just that for a sony alpha. Turns out, the pre-programmed remotes are coded signals, not a solid, high-density IR beam, so your best bet is an IR LED from Radio Shack, a button, and a 3V (or whatever the nominal LED voltage is) battery. It’ll run you about $8 total, which is comparable to a cheap hong kong trigger.

Yep, IR remotes use a modulated signal in the 38-40kHz range.

When building your own, don’t forget a resistor or your IR LED will likely live a bright but very brief life. Use Ohm’s law (R=V/I) to calculate the resistor size based on the battery voltage (V) and maximum current (I) of the IR LED.

That’s really weird-I could swear my camera triggered in remote mode when I lit the magnesium shavings. I’m going to try it again.

[Plamadude30k]

While I’m at it, I figured I’d post the results of my experiments with different lenses for astrophotos. Both of these photos were taken from the exact same place with the exact same camera settings of:
28mm, f/minimum (either 2.5 or 4), 20 second exposures, ISO of 400. The exact same (minor) postprocessing was applied to both. Let’s see the results.

Image 1-Vivitar (actually made by Tamron) 28mm f/2.5 prime:

Image 2-Nikkor 18-105mm f/3.5-5.6:

Clearly the faster lens is brighter, and personally I think it has excellent color reproduction. If we zoom in, however, we can see the real differences:

Vivitar, zoomed:

Nikkor, zoomed (same region):

So, yeah. Chrom. Abb., coma, possibly spherical aberration, maybe even some astigmatism, though it’s worth it to note that astigmatism is difficult to diagnose here since everything else could easily mask it. In fact, there’s some really interesting field curvature and off-axis things going on elsewhere in the image-mostly REALLY strong chromatic aberration. Thankfully it’s not bad enough to notice on a computer screen/zoomed out image, but I wouldn’t want to print it. The Nikkor, on the other hand, is optically good enough that my focus and star movement is worse than any possible flaws in the optics. Weirdly, I think I actually had better focus on the 28mm. I guess that’s the difference between a $400 lens and a $40 lens.

[Plamadude30k]

The 18-55mm is an okay lens-it’s what I started with (though mine wasn’t the VR version). The focus on it is excessively fiddly, though, and if you’re not extremely lucky the focus will be noticeably off. Sadly, skill and experience has almost no effect there. You basically just guess. Equally sadly, you’re probably not going to find too many better wide/fast lenses for a nikon unless you’re willing to spend $$$$ to $$$$$. Trust me, I’ve looked.

As for the remote, it’s super simple-you could probably build one. Basically an IR led with a button to turn it on. There’s no coded signal on it either-I’ve managed to set off my camera by igniting magnesium shavings from my backpacking firestarting kit using just a knife and steel.

[Plamadude30k]

How’d the experiments go? If need to feel better about yours, I could probably dig up my first attempts at astrophotography-they were hopeless.

Getting away from light pollution is always a good idea, and unless you have a motorized tracking mount, you’ll want a wide-angle lens, the faster the better. I’ve been going back and forth between my 18-105 mm f/3.5-5.6 set at 18mm, f/3.5 and my 28mm f/2.5. The 28mm is WAY faster and has weirdly awesome saturation/color reproduction, but is optically…crap. The 18-105mm is a great lens, but for some mysterious reason, I’m never 100% satisfied with the astrophotos that come out of it.

As for getting exposures longer than 30 seconds, if you have a nikon, you’ll almost certainly need a remote. The ML-L3 is the one I use-cheap and effective. You can also take a bunch of shorter exposures and stack them-I think there’s some free software for that floating around on the internet.

[Plamadude30k]

Is that the wrong point of view? Am I not doing enough? Should I take a hard stance here just on principal? I’d like to know what you all think…

I think that’s completely up to you, but if it was me, I’d be more than a little annoyed that they never asked for permission to use the photo. So far, I’ve allowed anybody who takes the time to ask to use my photos for free, so long as they’re not using them for commercial means. I’d just ask them to attribute the photo correctly and to please ask before blatantly stealing somebody else’s work.

[Plamadude30k]

That’s not a bad idea, Rav, having some experience with lenses without any focus demarcation at all, making little marks could help. I can’t begin to tell you how many out of focus astro images I’ve taken. Sometimes you can focus on a star if you can find a sufficiently bright one, but that’s not always an option. I’ve used distant city lights sometimes, too-anything further away than ~100 meters should get you close enough, depending on the lens-further is always better, of course. I also like to focus on point sources rather than extended sources-it just seems to be easier. Of course, there’s plenty of other problems to worry about once you’ve got the focus down. I was out at Kitt Peak not too long ago, and out of ~50 images, only a few were usable. Turns out I was out on the catwalk with a ton of astro camp students who kept nudging my tripod-not on purpose of course, but it was enough to subtly ruin almost every image I took. Even a few with nice looking meteors. Grrr.

[Plamadude30k]

God, photojojo is just full of precious little things that make me want to engage in an involuntary personal protein spill.

Nice to know there’s other Carlin fans here. Also, completely agreed.

[Plamadude30k]

Man, why can’t this one be scheduled *after* I move to Hawaii?

[Plamadude30k]

Well, I think I’m going to sit this one out-the only shot I have that I would consider using was already used in a previous contest. Unfortunately I just didn’t have time to go out and shoot stuff this week. I’ll be watching it as avidly as ever, though.

[Plamadude30k]

I got absolutely nothing-I think a lot of the Tucson fireworks were cancelled on account of rain. The lightning wasn’t even very impressive-lots of cloud-to-cloud stuff that was rendered pretty much invisible. Good stuff here, though.

[Plamadude30k]

How did this turn out?

Best thing I’ve done to a pork product since I breaded and deep-fried a bacon strip wrapped around some cheese. I had 5 pounds of pork shoulder when I started, and I think I still have most of it left. Dinner for a week!

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