When I was out in the desert last week letting my telescope image the Lagoon Nebula, I spent my downtime trying yet again to take a better picture of the Milky Way.
The basic problem is simple. Since my camera is on a fixed tripod, the longest exposure I can take is about 15 seconds before the stars start to blur. That short exposure time means I have to use my maximum ISO, 12800, which produces lots of noise and soft, blotchy images. I can improve things by taking multiple images, but I'm limited to about ten.
But! Years ago I bought a cheap little equatorial mount designed specifically for cameras. The mount tracks the sky, which means I can make a long exposure with a lower ISO, and I can easily stack 20 or 30 exposures into a final image.
There's only one problem: the mount has to be pointed at Polaris, and I've forgotten how to do this. (With the telescope it's all handled by software.) The basic process is simple: Tilt the mount upward 33° (because I live at 33° latitude) and point it by eyeball toward Polaris. Then look through the polarscope to line up precisely on Polaris.
The problem is that while it's easy to find Polaris just by looking at the sky, the polarscope provides a magnified view where all the stars look alike. So which one is Polaris? I used to be able to do this, but I seem to have lost the knack.
Eventually I gave up and figured that approximately right was good enough. It wasn't. The stars were still streaky, which made the whole image blurry. The image also had a green cast, which might be an artifact of the camera. I'm not sure. On the bright side, the exposure and stacking captured plenty of light and showed lots of the Milky Way, not just the brightest parts.
Oh well. I'll try again next June, when Milky Way season returns.
Beautifully cinematic and dream-like, I really want to know, what happens next?
Yes - but Kevin Drum is the one who produces something with beauty & mystery, but still seeks perfection when he already has created something special that we can apparently appreciate more than he does. I appreciate the charts & opinions, but the photography is memorable.
You can get pretty close by setting your declination to 33 degrees (or whatever your local latitude is) and pointing your mount due north. Then, at least with the polarscope that came with mine, there's reticule inside that has a circle, Polaris should be on this circle or close to it.
Or you can just buy an electronic polarscope, which makes life real simple when you use it with a laptop.
The actual center of rotation of the sky isn't exactly on Polaris, so even if you were to get Polaris in your crosshairs, you'd still be off and the stars would still drift.
My little Star Adventurer mount has a polar scope with a reticle which has the position of the true pole marked out, but you have to know what the local time is, and align the reticle, and get the reticle illuminator adjusted just right, etc. Etc. You basically need a smart phone and the app and an advanced course in polar alignment to do this right.
Obviously, I don't take many astrophotos. Because they are hard.
I know what the green cast is,
it's the Colour Out of Space.
Ha!
1. Use (formerly Google) SkyMap to find things in the sky.
2. Don't you use NINA? It has a built in polar alignment tool. You could use PHD2, but you have to be a masochist to do drift alignment in these days of plate solving.
3. If you want to spend a small amount of money, SharpCap Pro has the slickest plate solving polar alignment I know of.
Use a camera, not your eyeballs. Let the software do the work.
Completely, totally off topic but since there aren’t a lot of comments, here goes.
I was reading about Euclids 5th postulate as posted at the top of Kevin’s post and it got me thinking about why there isn’t a corollary postulate:
If a straight line intersects two other straight lines, and the interior angles on the same side adds up to MORE than two 90 degree angles, the lines will NEVER intersect if extended indefinitely.
Does this matter? Perhaps a mathematician can weigh in on this?
The lines would intersect in the opposite direction.
Right. I get that. That’s the 5th postulate. But I’m talking about the interior angles being on the other side where the lines will never intersect
I'm not a geometer, so I'm not an expert on the nuances of how the postulates fit together from a modern perspective. But:
If I understand your question correctly, start with what John Powell said. Then if the lines also intersected on the other side, which is what you asked about, you would have two distinct lines that intersect at two different points. In ordinary Euclidean geometry, that's not possible. Whether it's possible in other axiom systems may depend on what you are willing to allow as non-Euclidean geometry.
I love this photograph.
Gorgeous.
I assume the linear features to the upper left are from Starlinks.
I’d guess satellites would show as dashes not dots. So I’d further guess that the features you are seeing are due to the human brain’s tendency to see patterns in random data. But what the heck do I know!