Show HN: AstroHelm – Use your phone camera to aim a telescope or telephoto lens
openAs an amateur astronomer living in New York City, finding objects in the night sky has always been a huge challenge. I thought about using the smartphone's gyroscope and magnetometer, but the accuracy left a lot to be desired.
Then I learned about plate solving: given a picture of the sky, we can determine exactly where in the sky the camera was pointing by identifying the star pattern. This was a much better fit - as long as the phone and the optics are rigidly connected, we can repeatedly photograph the sky and determine the pointing direction with very high accuracy.
A lot of work was done to design an algorithm that works reliably with smartphone cameras, which have limited light sensitivity and wider field of view which includes buildings and trees. I experimented a lot with machine learning, and to my surprise, traditional CV methods actually performed better at extracting stars from the image.
The result is AstroHelm, an iOS and Android app that helps figure out where your telescope or camera is pointing, and guides you to the object of your choice. Just follow an arrow on screen, and the object will land right in your eyepiece or viewfinder. Everything happens on device, and no internet connection is required.
AstroHelm is free to use and comes with beginner-friendly objects selected for each night. Optional one time purchases unlock more objects and advanced features, such as interoperability with other astronomy software. I am also proud to partner with astronomy clubs and organizations to offer free licenses for outreach.
I hope AstroHelm can make it a little easier to discover the wonders of the night sky, and I look forward to your feedback!
32 comments
- Computes coordinates in less than a second
For comparison, the sky moves 15 arcseconds per second. So without a motorized mount to keep the telescope on target, the accuracy will be short-lived.
It would be easier if you could use an eyepiece adapter. I have no idea why the page claims "The field of view is typically too small for plate solving to work." for that approach - it works just fine with a FOV of at least 0.2 degrees or so, which is much smaller than what most beginner/intermediate scopes have.
And if you do have a scope with a smaller TFOV, I'd argue you're likely not the target audience for the app. (Yes, you can get there cheaply and as a first scope, but it's not the usual route)
Edit: I want to be clear it's not a diss on the app - it's great. Plate solving at that speed is pretty cool. I just wish it'd work at smaller TFOVs :)
As for why we don't support adding optics between the phone and the sky, there are a few reasons. The accuracy from phone's camera lens is good enough, and we don't want to introduce complexity. The plate solving algorithm also benefits heavily from knowing the field of view, which you get from phone's built in camera but need user input for custom optics. Finally, supporting smaller field of view means shipping a much larger star database which most users won't use, so it's just a waste of storage and bandwidth. Not to mention blind solving a small FoV would be very slow and not work interactively.
For alignment, we support two alignment methods. You can align it like a finderscope, i.e. aim your telescope at a distant treetop and drag the crosshair over it. Once you begin observing, you can also sync to the object, which should give you better accuracy.
The best dark-sky sites don't have Internet access. AstroHelm’s plate solving engine runs entirely on device. No internet connection required, and your camera images stay on your phone."
This looks like a great tool for the following application:
o Off-grid, deep wilderness, high mountain, broad desert or ocean navigation (like the way ancient seafarers would navigate via the position of the stars in the nighttime sky, relative to them)
(Also, if you're a Star Trek fan and/or futurist, you'd expect that computers on future spacecraft would or could run some version of this software, or at least some form of Plate Solving / Astrometric Solving algorithm...)
Anyway, the app looks great!
Related:
General wikipedia information page about Astrometric Solving (does not include algorithms!):
https://en.wikipedia.org/wiki/Astrometric_solving
Paper: New Algorithms for Automated Astrometry, by Chris Harvey (2004) (An excellent paper about all that is necessary for such an algorithm!):
https://cs.nyu.edu/home/people/in_memoriam/roweis/papers/Har...
I'm spoiled. The best dark-sky site near me, a meager 4 hour drive, is an astronomy campus with fiber internet providing wifi. Intentionally, it's not a lot of bandwidth to do streaming while you're bored, but enough to run apps like this. They also have a what they named the StarField which is an open field where there is a grid where every 10' or so has an electrical outlet popping up from the ground to power your gear. It's the darkest skies in my state that is not federal land.
A related issue I’ve been wondering about: Why don’t gimbals for cameras and smartphones offer an astrophotography mode for long exposures of the night sky?
https://github.com/sky-map-team/stardroid