Yet another Hacker News

Show HN: AstroHelm – Use your phone camera to aim a telescope or telephoto lens

25 points HeavenFox 2 days ago 10 comments

Hello HN!

As 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!

chantepierre 1 hour ago | parent

Hey, I'd actually use that. I build telescopes (see personal site in profile) and only do visual astronomy. I voluntarily prefer to use old-ish phones, i.e. currently I am using an iPhone SE 2022. Do you think the weak signal under the night sky would work with your plate solving ?

rrr_oh_man 1 hour ago | parent

Cool project!

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

But:

“After that, whatever I called for was in the field of view, even when I was using a 5mm eyepiece.”

chantepierre 1 hour ago | parent

They mean that the FOV seen by the phone through an eyepiece is too small to run a successful plate solve.

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

rrr_oh_man 1 hour ago | parent

Thank you for the explanation!

chantepierre 1 hour ago | parent

For more context, the other comment saying "I’m really impressed… guided me almost dead on to the double cluster when asked." is a bit funny, because the double cluster is easily seen naked-eye in suburban sky, which is as easy as it gets for deep sky objects. But the comment you quoted makes the app look good and I'm going to try it if the fall cloud cover ever goes away.

fanatic2pope 1 hour ago | parent

This looks great, but why is there no "plus" version for Android?

soltanov 53 minutes ago | parent

Good call ditching ML. Traditional CV still wins on power, latency, and determinism for star centroiding.

danbruc 38 minutes ago | parent

- Accurate up to within 10 arcseconds (1/360 of a degree)

- 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.

solarist 22 minutes ago | parent

OP mixed up accuracy and resolution.

skypanther 31 minutes ago | parent

This looks like a nice alternative to PiFinder. No extra hardware required. https://www.pifinder.io/