Starship Asterisk*

So any ray entering the objective lens at any angle will converge at the focal point (more or less, depending on "aberration" perhaps?)? I suppose there's a way to calculate the exact path of any given ray...I need an interactive model to play with! telescope magnification angles.jpg Rays...

Thanks. That would almost makes sense if I only I could understand why those particular light ray lines are the appropriate ones to choose to indicate that this is actually happening! The rays seem suspiciously convenient. There's nothing special about them. A ray entering straight will exit straig...

Al right. My problem is that I keep ignoring the effect that the magnification has. And frankly, now that I realize that, I realize I'm not even clear how the magnification is happening, in apparent opposition to the fact that the objective lens is larger than the eyepiece lens. 😟 So, why does the ...

Yes, exactly as shown in the image: all those photons in the entire larger area of the objective lens are compressed down to the smaller area of the eyepiece lens. Why isn't that what's actually happening? telescope and eye.jpg That is what's happening. Absolutely, more photons are entering the eye...

Still making no sense to me. If I put my pupil at the focal point of the objective lens in the picture, and we're pointed at the Sun, my eye would be severely burned (as would a piece of paper placed there). Right? So why isn't that intensity merely a bit reduced by the expansion of the rays on the...

Well, what if the eyepiece diameter is the same size as the pupil? Isn't it receiving more photons per area than it would without the optics in place? telescope and eye.jpg You certainly collect more photons. But you distribute them over a larger area. That's why there's no change in brightness. Sa...

How does that pertain to this image, which sure looks like it is concentrating more photons onto a lesser area: https://letstalkscience.ca/sites/default/files/styles/width_800px/public/2019-12/path-rays-refractor.png Yes... but how much of that light is making it into the eye? All of the light that...

Well, yes, I suppose if you put your face in the path of the eyepiece your eyes would get the same number of photons per unit area as if there were no telescope at all. But I think of telescopes with magnification > 1 as concentrating the photons into a smaller area, thus increasing brightness. Is ...

I fear I will never understand this point that you're always making. 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...

So, given that the first telescopes were invented in 1608 , it took more than 200 years for astronomers to discover the spiral arms of spiral galaxies. That should give you an idea of how faint the arms typically are. It's worth mentioning (again) that telescopes don't make anything brighter, only ...

So, given that the first telescopes were invented in 1608 , it took more than 200 years for astronomers to discover the spiral arms of spiral galaxies. That should give you an idea of how faint the arms typically are. It's worth mentioning (again) that telescopes don't make anything brighter, only ...

And why is the lack of a Hubble image understandable? Is it just because Hubble's FOV is too small to take it all in? Most or all of these objects have been imaged by the HST. It's just the wide field that encompasses all of them that Hubble can't do (as is the case with the majority of APOD images...

And, for the understandable lack of a Hubble portrait of this extended group... And why is the lack of a Hubble image understandable? Is it just because Hubble's FOV is too small to take it all in? Most or all of these objects have been imaged by the HST. It's just the wide field that encompasses a...

Jim Armstrong wrote: ↑Wed Nov 06, 2024 4:58 pm Perhaps it is only my connection to APOD that gives a photograph of a cat when the link to "Still being discovered" at the bottom is accessed.

It would not be an APOD without at least one caption link to a cat image.

I think there are two explanations for the crazily red B-V index for blue-looking NGC 6744. First, the B-V value for NGC 6744 is not its "total" but its "effective" B-V, and those values may well be different, for all I know. The second explanation is that its yellow center must...

What is the estimated distance between IC 2118 and Rigel? It's amazing that a star can illuminate an object even very far away. Alex This nebula is extremely dim. Don't be fooled by an image exposed for hours. If Rigel were the only star in the sky it would do just fine to light up a nighttime land...

Hi Chris - I believe I have the old master file on an old hard drive. I'll check tomorrow and see. That's a good idea - I haven't worked with OSC data in a while, so it'll be fun to see what these new tools can do with that type of data. A lot has changed in the last four years! FYI, for anybody wh...

Hi Chris - I believe I have the old master file on an old hard drive. I'll check tomorrow and see. That's a good idea - I haven't worked with OSC data in a while, so it'll be fun to see what these new tools can do with that type of data. A lot has changed in the last four years! FYI, for anybody wh...

Hi everyone, I really appreciate this conversation. As the owner of the image, please allow me to provide some information and clarity on the situation. This photo was taken in July of 2020 (over four years ago), when I had less than one of year of astrophotography experience. I submitted it to APO...

I don't know the history of this image, but I think it is exactly what should NEVER be awarded an APOD. Aside from the shape of the bubble, there is not a single detail that is real, there is no match with the details visible in the Hubble version. Here is a simple comparison: https://www.youtube.c...

This image displays a disturbing trend in some astroimaging these days of overprocessing to the point that structure is invented. We only need to look at the size of the stars to see that seeing conditions were limited to about 2 arcseconds. All that fine detail inside the nebula was synthesized by ...

I really appreciate the nice pink / magenta Hydrogen Alpha emission :) BTW, by coincidence I was imaging this target a couple of nights ago, in H-alpha as well as RGB. Two processed versions here from exactly the same data. One has all of the H-alpha data mapped to the red channel (which is physica...

I really appreciate the nice pink / magenta Hydrogen Alpha emission :) BTW, by coincidence I was imaging this target a couple of nights ago, in H-alpha as well as RGB. Two processed versions here from exactly the same data. One has all of the H-alpha data mapped to the red channel (which is physica...

I like the arts and artsy photos but this is a science site that many people who don’t know anything about astronomy learn from. They shouldn’t be posting photos of things in a straight line that show as bent. So you would prefer that the horizon be shown as bent? You can't project a sphere onto a ...

florid_snow wrote: ↑Sun Oct 27, 2024 2:58 pm I really appreciate the nice pink / magenta Hydrogen Alpha emission

H-alpha isn't pink! It's deep ruby red. I think what you mean is that you appreciate that you're seeing some combination of H-alpha, H-beta, and continuum radiation that is resulting in a pink color.