Olivier Hainaut

Hibernating. Will come back when the musky smell dissipates.

[Olivier Hainaut @ohainaut]

Hibernating this account. The musky smell has become too unpleasant.

[Jonathan McDowell @planet4589]

I've created a little web page to describe the 1912 9-inch Clark Refractor on the roof of the Harvard Observatory https://t.co/xolkfrv68c

[Olivier Hainaut @ohainaut]

Radio-astronomy pollution from satellite constellations

[Robert Massey @RobertMMassey]

And there *are* mitigation approaches that work. Needs a global effort to regulate and make them mandatory.

[Robert Massey @RobertMMassey]

Great work by @FedeDiVruno. There's an urgent need to regulate radio interference from spacecraft. Why would we want to deliberately obscure our view of the universe?

[Physics In History @PhysInHistory]

On this day in 1687, Sir Isaac Newton publishes Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), one of the most significant works in the history of science.

The Principia*states Newton's laws of motion, forming the foundation of classical mechanics; Newton's law of universal gravitation; and a derivation of Johannes Kepler's laws of planetary motion (which Kepler had first obtained empirically).

[ESA's Euclid mission @ESA_Euclid]

@ESA_Euclid as seen from the Calar Alto Schmidt telescope by ESA Planetary Defence Office @esaoperations , 5.5 hours after launch on its way to L2.
👉🏻 https://t.co/lsszKvbTDq

[Olivier Hainaut @ohainaut]

@apolitosb Enjoy it while it lasts. Soon, we will have extra virgin olive oil from Belgium, UK, Denmark added to the mix...

[Olivier Hainaut @ohainaut]

@apolitosb @markmccaughrean @astro_jcm Photons travel in space at the speed of light: they don't age... 🧐

[Olivier Hainaut @ohainaut]

@esaoperations @AsteroidDay @ESO Yep! We got it. Faint (super faint!), but it's there!

[Olivier Hainaut @ohainaut]

@JohnBarentine @ESO @Andy4Science ...and its companion article, which is more readable and a little bit more recent, from the same @Andy4Science, @ohainaut, et al: https://t.co/n3DbeTWR36

[Olivier Hainaut @ohainaut]

@CyberTower red 147

[Olivier Hainaut @ohainaut]

@CyberTower red xxx

[Olivier Hainaut @ohainaut]

@JohnBarentine @Andy4Science Don't hesitate to call if you want more info or if something is not clear. Comments are of course welcome (email pls - I'm not often on Twitter).

[Olivier Hainaut @ohainaut]

@CyberTower blue blue

[Olivier Hainaut @ohainaut]

@GetBAC They are spectacular because they are low and flying together. Once they reach their final altitude, they will be too faint to see. I computed (for ESO https://t.co/NYmklWcJSF) that ~100 will be visible for 1h after twilight, then they drop in the shadow.

[Olivier Hainaut @ohainaut]

@atomicthumbs Don't worry too much: as soon as they reach their final orbit, they won't be visible with the naked eye anymore. I computed (for ESO telescopes) about 100 sat will be visible in twilight when all the 27000 foreseen are launched. All are gone 1h after.

[Olivier Hainaut @ohainaut]

@michael_w_busch Actually, astronomical observations will be essentially unaffected by megaconstellations. I computed the effect (for ESO telescopes): <~1% during the first/last 1-2 hours of the night. It is slightly worse for LSST. See https://t.co/w0CXS8XsWV

[Olivier Hainaut @ohainaut]

@skyglowberlin @Isinlor @ESO @TheNRAO @IAU_org The calculations I made are for 27000 satellites in 19 constellations. Don't ask me about radio telescopes: I know about optical, not radio. Someone else will have to comment. I understand there are already some regulations in place for radio.

[Olivier Hainaut @ohainaut]

@rgrokett @lcjohnso @89Marvaz @cerrotololo @elonmusk Correct, but the occultation will last 0.2-2 ms (depending on the altitude and zenithal dist.), causing an error of the order of 0.1 milli-mag. Even for transit work, that's below the precision of ground-based photometry. Note there are already several thousands of sat up there.

[Olivier Hainaut @ohainaut]

@lcjohnso @89Marvaz @cerrotololo ... I ran some fairly detailed computations on the effect on the ESO telescopes (eg VLT, and soon ELT) considering Starlink and the other constellations: we will be very moderately affected for ~1h after sunset/before sunrise, at ~1% level.