95 points | 4d ago | Discuss on Hacker News | Back to Radar
Pls fix (AI slop?):
Unsupported: Smartphone Eyepiece Adapter
Eyepiece adapters hold the phone’s camera over the eyepiece so you can photograph through the telescope. AstroHelm does not support this configuration. The field of view is typically too small for plate solving to work
“After that, whatever I called for was in the field of view, even when I was using a 5mm eyepiece.”
The comment of the user says "the plate solve was precise enough that the object I wanted was centered (for the observer, not for the phone) when I used a 5mm eyepiece" (which is usually an high-power, meaning tiny-FOV eyepiece)
Most pointing methods aren't accurate enough to correctly center an object at high power and require you to use a lower power eyepiece, nudge the object a bit, then switch to high power. I understand how you read it as slop but the two sentences aren't contradictory, and the user comment hints to an useful pointing tool :)
Edit : bad tenses and grammar fixes
- 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?
@HeavenFox - also in NYC - drop me a line over at allisterk.com if you have a chance!
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