Comment by zokier
5 days ago
One thing that I'd be interested in is having telescope mount suitable for doing quantitative measurements, basically doing astrometry from first principles. To me solving the orbits of planets (etc) based solely on my own measurements sounds very compelling. It would be like retracing the steps Kepler etc did.
Sounds like a really interesting potential project. I've been pondering a system that would make amateur observations usable beyond pretty pictures. Single frames captured could be shared in raw form along with metadata (time, coords, calibration frames), potentially allowing aggregators to process it for scientific research (or even prettier pictures). The Vera C. Rubin Observatory is now able to capture the entire southern hemisphere in a couple of days. Imagine having our capturing software contributing to a planet-wide crowdsourced telescope array.
We did this for a recent eclipse- we had thousands of photographs along the path of totality upload photos with GPS and timestamps then registered/aligned/scaled all the images and made one long "movie of totality". It turned out not so great due to the huge variability in camera quality and the resulting images.
The best way to determine the exact position of a planet is not to have a highly calibrated telescope mount that knows exactly where it is looking. Instead, it is to take a decent picture with the planet approximately in the middle, and feed it into a piece of software that looks at all the surrounding stars (with known positions) and calculates the planet position from that.
Getting a telescope mount calibrated that well is nigh on impossible. Calculating position by relative position of nearby stars is incredibly accurate.
Yeah, I know plate solving is a thing. People did it even manually back in the days when plates were just film photographs, you don't need fancy computers for that.
Tbh this is the sort of thing why I would want to do this experiment, to determine what observations/measurements you actually need.
As you noted, to do plate solving successfully you need accurate and comprehensive star catalogue. But if you are starting from first principles then can you build such catalogue without precision aiming? Maybe you can, but it is all bit difficult to wrap your head around without concrete experimentation.
Of course historically afaik this sort of work was done with precision transit instruments. But that is interesting question, can we bypass that step if we use photography and some computation
In this case, a precision transit instrument can be the two corners of two houses (or some other structure that won't move) that are separated by a reasonable distance, an eyeball, and an accurate time. Stand at one and sight along both edges looking South past the other wall, and mark the exact time when a star disappears behind the far wall. That'll give you a load of pretty accurate relative right ascension values. If you can measure the time the the star disappears to within about a second, that gives you an accuracy of 15 arcseconds. If you use a video camera and frame-count, you can get better than that. It'll be best if the far wall is accurately straight and vertical and accurately due South from your observation position. You can get declination values by marking how high on the far wall the star was when it disappeared, or indeed the position in the video when it disappeared, and that accuracy will be the zoom level of your camera. (Make sure you calibrate out the distortions of the camera lens. Creating a panorama in daytime and processing it in something like hugin will give you this.)
Another interesting project might be capturing host star light curves for transiting exoplanets. For a number of closer ones, it can be done conveniently from a backyard with just a photographic lens. Here's one amateur using ASI178MM-c with a Canon FD 300 mm:
https://astropolis.pl/topic/60163-wasp-10-b-w-pegazie-1270-m...
First principles it is not, but people use the Seestar S50 roboscope with a distraction grating to get readings on the emission spectra of stars.
Did you mean diffraction grating? Or is there something I haven't heard of?
Frankly, distraction grating sounds like the perfect name for an amateur astronomy accessory.
Alas, autocorrect.
I really need the distraction grating to be something that distracts me before I buy more astronomy gear.
Works great on cheeses too!
Kepler did it without a telescope, using Tycho's naked-eye observations.
Brahe did have large quadrants (and armillarys) though, which in this context is not all that different especially when you factor in how much light pollution impacts observations.
Not to take away from Brahes exceptional ability at naked eye observations, but the key here is having some sort of instrument that enables precise measurements, be it telescope on a mount or huge mural quadrant.