Starship Asterisk*

Why is the resolution of the Moon's surface much worse than the image of Orion? Something to do with the dynamic range of the camera? Not sure, but this image seems to be a still (or even a screen grab) from the first second of this video: https://www.flickr.com/photos/nasa2explore/52520558512/in/a...

fredk wrote: ↑Wed Nov 20, 2024 5:31 pm I contacted the Webb news team about this. They agreed the release was confusing and say they'll try to make it clear that these are diffraction spikes in future releases.

Thanks!

In case it's not obvious, as it wasn't to me, the HH objects are shown in the mouse-over at the " featured image " link. I think the fragments on both sides of Geck's image are, as Victor suspects, something like mini "pillars of creation". Herbig-Haro objects are small, glowing...

In case it's not obvious, as it wasn't to me, the HH objects are shown in the mouse-over at the "featured image" link.

So, experts, what's the consensus: are those red "rays" real, or just JWST diffraction spike artifacts?

Hello APOD and fellow astronomy enthusiasts, I'm excited to share an image I captured of Comet Tsuchinshan–ATLAS, where a double streak is visible in the comet’s tail. This stack was created from exposures taken on the night of October 23, 2024, between 20:01 and 21:56 local time, from Salles Courb...

It's not clear from the APOD caption or the Webb release, but the straight red rays near the centre of NGC 1365 in the APOD image are diffraction spikes due to the bright compact sources around the nucleus, not actual features in the galaxy. They're more obvious as diffraction spikes in the partner...

I completely agree with you, Ann. The red rays only exist in mid-infrared (MIRI). The matter is clear in near-infrared (NIRCAM) images. What a beauty. I would book that trip immediately :wink: https://live.staticflickr.com/65535/54137866836_148cd50ecb_b.jpg bigger: https://live.staticflickr.com/655...

Red rays or no, how can that clearly core-like dead center bright spot NOT be the core? Hmm, on second thought, maybe there are two cores! I changed my mind, Johnny. I now believe that the bright yellowish spot is indeed the core, and the source from which the red rays appear is probably a hidden s...

NGC 1365 is a very interesting and impressive galaxy, and JWST's MIRI image sheds new light on it. ... Let's take a closer look at the core as seen by MIRI: APOD 13 November 2024 detail annotated.png https://asterisk.apod.com/download/file.php?id=50574&mode=view Let's look at the objects in the...

https://apod.nasa.gov/apod/calendar/S_241113.jpg Barred Spiral Galaxy NGC 1365 from Webb [...] Astronomers suspect the gravity field of NGC 1365's bar plays a crucial role in the galaxy's evolution, funneling gas and dust into a star-forming maelstrom and ultimately feeding material into the active...

To all those people posting their excellent photos of the comet and its dark streak, are you also sending them to APOD as requested in the text? Regardless though, they're nice to see here as well!

JohnD wrote: ↑Tue Nov 12, 2024 10:45 am Me too! It looks to cast a shadow of the main star on the structures nearer us. A dust cloud would surely have been long ago blown away?

Looks like just an unusually opaque glob of dust to me. I google but didn't find anything that pointed it out.

As long as that distant object is a point source (like a star) that lies on the optical axis. Any extended object (regardless of distance) will result in rays entering at different angles, and a point source off of the optical axis will create an image that isn't at the focal point. But aren't thos...

Delves? Makes sense to me. "Delves" as in digs, which is appropriate since it is STILL being dug or carved by running water! delve (v.) Middle English delven, from Old English delfan "to dig, turn up with a spade or other tool, excavate" (class III strong verb; past tense dealf,...

Rays converge at the focal plane , not the focal point . Otherwise you'd never have an image at the focal plane. A bundle of rays around the optical axis will converge at the focal point. Parallel bundles coming at other angles will converge above or below the focal point, but nominally on a plane ...

There's nothing special about them. A ray entering straight will exit straight. No matter what angle a ray comes in, it has to exit at a steeper angle, and that angle is just the input angle times the angular magnification. So any ray entering the objective lens at any angle will converge at the fo...

Maybe the easiest way to imagine it is by considering the angle of rays. A ray coming into the objective at some angle will exit the eyepiece at a steeper angle (assuming the focal length of the eyepiece is less than that of the objective). A fan of rays spanning a wider angle is the same thing you...

That is what's happening. Absolutely, more photons are entering the eye. But the photon flux per unit area doesn't change. Aperture: 50mm F1 (objective): 500mm F2 (eyepiece): 50mm Pupil size: 5mm The magnification of this system is 10X. The pupil of the eye maps exactly back to the diameter of the ...

An objective lens by itself is not a telescope. A single objective is a focal optical system. A telescope is an afocal optical system. The only reason a telescope forms an image is because the lens of your eye is a focal optical system. Again, work backwards from your retina. Can you figure out any...

You certainly collect more photons. But you distribute them over a larger area. That's why there's no change in brightness. Say you have a dark adapted pupil size of 6mm. With a scope operating at 100X, you'd need an objective of 600mm to achieve the same surface brightness on your retina that your...

Yes... but how much of that light is making it into the eye? All of the light that is outside the diameter of your pupil is lost. That's why you have to project the size of your pupil backwards through the system. Doing that you'll see that the effective aperture is not the physical aperture, but t...

Ok, now make your 1-m telescope have a magnification of two. Propagate your eye's pupil backwards through that system, and you'll see that the only light entering your eye is from a central disk on the objective that is twice the diameter of your pupil. Does that make sense? So you are collecting f...

Maybe it would help if you considered a telescope with a one meter aperture, and an objective and an eyepiece with the same focal length. That is, a one meter aperture and a magnification of one. Can you see why that won't produce an image brighter than your eye alone? Well, yes, I suppose if you p...

It's worth mentioning (again) that telescopes don't make anything brighter, only bigger. A perfect telescope produces an image on the back of the eye with the same brightness as the eye alone receives. In actual life, telescopes aren't perfect, and the image is always somewhat less bright. But we d...