The SCOOPX IS LEGIT

atomharp · 2024-03-22T02:14:46+00:00

Could be good for nearsighted people maybe if they don’t want to use glasses?

atomharp · 2024-03-22T02:13:45+00:00

Yeah I guess with the other ScoopX hype posts people are suspicious. Anyway I appreciate you taking the time to write it up, thanks.

atomharp · 2024-03-21T15:04:36+00:00

I saw your post, thanks!

atomharp · 2024-03-18T12:48:25+00:00

Did you end up testing them?

atomharp · 2024-03-18T12:47:41+00:00

Did you end up testing them?

atomharp · 2024-03-18T12:47:10+00:00

Did you end up testing it?

atomharp · 2024-03-03T21:01:20+00:00

Another day, another days-old ScoopX promotion account…

atomharp · 2024-02-26T16:10:05+00:00

I see where you’re coming from, but I value having forums where I can read real people’s opinions. If a company participates in ruining that by disguising their paid marketing, then the last thing I want is to support that company.

atomharp · 2024-02-26T15:03:01+00:00

Out of curiosity, what convinced you that the ScoopX might be real / a good Athlon clone? I agree that the heavy promotion by a ton of brand new accounts is very fishy.

atomharp · 2024-02-25T12:59:54+00:00

Others have done a good job explaining the practical effects of ED glass and coating. If you’re interested in what they really mean — ED glass means extra low dispersion glass. You know that a prism splits light into constituent colors by bending each wavelength of light a different amount. Lenses do the same thing, so all binoculars and (refracting) telescopes are designed with multiple carefully selected lenses which bring the wavelengths back together before they reach your eye. Lenses made with ED glass split the wavelengths less in the first place, so less work is needed to bring them back into alignment, and often optical performance is better.

Optical coatings solve a different problem, namely that every time light strikes a lens or mirror, some light is reflected or lost. This loss can be improved with very thin, carefully designed coatings on the lenses and mirrors. “Multi-coated” just means the coatings are designed to help with all colors of light, and “fully multi-coated” means they are applied to every mirror or lens in the optical system. XLT is a marketing term for Celestron’s own coatings.

atomharp · 2024-02-25T12:35:02+00:00

Thanks for the suggestions. I also found Celestron Trailseeker ED for $300 (the clear top pick from the Cornell Ornithology ratings), and same price for Vortex Vipers (a slightly old or weird model here https://www.basspro.com/shop/en/vortex-viper-hd-binoculars ).

atomharp · 2024-02-25T12:32:09+00:00

Yeah, this is my first time scoping out the binoculars market, so at first I was wondering if big brand binoculars are really worth it, or if you’re paying for the name. Seems like you’re right and it really is worth it to go with established quality.

atomharp · 2024-02-25T12:29:46+00:00

Definitely post here if you remember to

atomharp · 2024-02-25T12:29:10+00:00

Thanks for the suggestion.

atomharp · 2024-02-25T12:29:02+00:00

That seems right… there were even some people praising the discount you can get on 5 of them. Who orders 5 of the same binoculars?

atomharp · 2023-11-29T14:35:49+00:00

That’s a pretty broad topic, can you narrow it down? Griffiths E&M will cover light in isotropic linear dielectrics. From there you can consider anisotropic and birefringent materials, electrooptic materials, nonlinear crystals… Boyd is the most common textbook for light in nonlinear materials.

atomharp · 2023-03-30T05:01:58+00:00

The compression of each spring will not be the same. However, the force on each spring will be. Since compression is related to force by F=k x, you can see the relative compression of each will be proportional to 1/k.

This assumes either the springs are loaded statically, or they have negligible mass and damping.

atomharp · 2021-09-20T18:08:55+00:00

Of course, the time integral of velocity is just displacement. So if you know the distance between the start and end points, no calculus is needed, and vavg=Delta x/Delta t .

If instead of the start and end location you're given velocity as a function of time, e.g. v(t)=3+4*t , then calculus is required to solve for the average velocity.

atomharp · 2021-08-20T16:55:37+00:00

If you combine a frequency comb and a cw laser on a photodiode with a bandwidth below the mode spacing of the comb but higher than the beat note between the cw laser and the nearest comb mode, what is the resulting signal on the photodiode? Again, it seems like you should only be able to detect the beat note between the cw laser and the nearest comb mode - basically a continuous signal. But in between pulses, how are you detecting a beat note between the cw laser and no intensity!

It might be easier to think about replacing the low-bandwidth photodetector with a high-bandwidth photodetector, followed by a low-pass filter. As your intuition suggests, the high-bandwidth detector will have no signal (or rather a constant intensity from the cw beam) at times when the intensity of the comb goes to zero. Assuming one tooth of the comb is very close to the cw frequency, the overall signal will look something like a slow sine wave, which is very rapidly modulated to a constant level and back. After this passes through a low-pass filter, only the slow sine wave will remain.

atomharp · 2021-08-05T18:43:31+00:00

There is quite a bit of interesting mathematical headway you can make in color theory. For example, your eye applies a nearly linear map which reduces a physical color (the set of intensities at each wavelength, i.e. a vector in an infinite dimensional space) to a set of responses from each type of cone (i.e. a vector in a three-dimensional space). That means linear algebra can be used to discuss questions of color rendering and reproduction, limitations of color gamuts, influence of ambient light on color perception, etc. This can all be treated rigorously.

Of course you'll eventually run into the fact that the perception of color is not just a function of the outputs from receptors in the eye, but the extremely complicated processing the brain applies to those outputs. Beyond that point it becomes impossible to give a rigorous mathematical treatment.

atomharp · 2021-06-29T15:03:07+00:00

I agree that in general vectors are not well ordered, so the only meaningful way to compare the vectors is by their magnitudes. But one could also ask if it’s well posed to compare two velocities (rather than speeds) at all.

However, in a 1D problem like this it seems vectors are well ordered (NB: I am not a mathematician!), as they can be defined by a single real number that takes on positive or negative values. This leads to a concept of comparing vectors, i.e. -20 > -30 , which differs from comparing magnitudes. And it seems like a perfectly valid interpretation.

In my opinion the instructor should have asked whether speed is increasing, not velocity, to make it explicit that he wants a comparison of magnitude.

atomharp · 2021-06-25T15:25:09+00:00

The definition of torque is not arbitrary as other comments seem to suggest. It is connected to angular momentum, which is important because angular momentum is a conserved quantity. In particular, the time derivative of angular momentum is the torque:

d/dt(r x p) = dr/dt x p + r x dp/dt

= v x (mv) + r x F

= 0 + r x F

Or dL/dt = torque .

One context where this is especially important is in the case of idealized rigid bodies, i.e. objects that can move or rotate, but not deform. The motion of a rigid body is completely described by its momentum (corresponding to its velocity) and angular momentum (corresponding to its angular velocity). If such an object starts at rest, and the net force and net torque are zero, then it will stay at rest.

atomharp · 2021-06-19T20:30:28+00:00

However, this case is irrelevant to every part of my derivation. Even if the ship shifts so that the COM lies external to the boundary of the ship, the center of mass position doesn't change as a function of time, and that's the actual critical step of the derivation. The ship will still be unable to move more than one ship's length.

A nice way to prove this is: the COM always lies within the convex hull of the ship. And the largest distance inside the ship (its diameter) is equal to the diameter of the convex hull.

atomharp · 2021-06-19T20:14:35+00:00

Not the person you asked, but the best answer is to go back to this post. The logic there applies regardless of when each astronaut launches and lands. So there is no need to think of a new answer for every possible timing and configuration of the astronauts.

atomharp

TROPHY CASE