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Celestron X-Cel Barlow 2x magnification or Celestron X-Cel LX eyepiece 5 mm for 250P Dobsonian Sky-Watcher Telescope

An eyepiece designed for high magnification will always give a better image than a Barlow. That's just a crude (but clever) kludge -- a negative lens shoved into the optical path.
Miss_Understands's user avatar
1 vote

Difference in field of view between JWST and Euclid

Mechanically, the difference between JWST and Euclid is that JWST has a focal length of 131.4 m, while Euclid has a focal length of 24.5 m. Telescope focal length doesn't directly control field of ...
Mark's user avatar
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11 votes

Difference in field of view between JWST and Euclid

The exact field of view (FOV) of a telescope is often not a unique number, but depends on the instrument in use. For JWST, the FOV is a typically few arcmin (1/60 of a degree). Here you can see the ...
pela's user avatar
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2 votes

Vera C. Rubin's LSST's ginormous camera's shutter; why does it open/close 1000 times a night & is this typical for large-format survey telescopes?

why does it open and close a thousand times a night? The other answers, while correct and fascinating, are completely irrelevant. The CCD readout time is important to the designers, but irrelevant to ...
Miss_Understands's user avatar
2 votes

Vera C. Rubin's LSST's ginormous camera's shutter; why does it open/close 1000 times a night & is this typical for large-format survey telescopes?

Supplemental, re-explaining answer post for those like me who are not so familiar with CCDs. I find the video below very helpful. Of the five readout systems illustrated, the two relevant here are: ...
uhoh's user avatar
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16 votes
Accepted

Vera C. Rubin's LSST's ginormous camera's shutter; why does it open/close 1000 times a night & is this typical for large-format survey telescopes?

The "sequence" of a CCD exposure might be to flush the CCD to get rid of all charge on the silicon, with the shutter closed; open the shutter; expose the CCD to astronomical light; close the ...
ProfRob's user avatar
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24 votes

Vera C. Rubin's LSST's ginormous camera's shutter; why does it open/close 1000 times a night & is this typical for large-format survey telescopes?

From Technology of the LSST focal plane: LSST’s survey efficiency depends on the telescope’s ability to rapidly move from field to field on the sky during a night’s observing. The mount has been ...
John Doty's user avatar
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6 votes

Given our current level of a technology, how far could we send a signal that we could detect?

While radio signals have a somewhat limited range due to scintillation in the interstellar medium where plasma refracts them; obviously some radio emissions get through fine since we do extragalactic ...
Anders Sandberg's user avatar
-1 votes

Given our current level of a technology, how far could we send a signal that we could detect?

There's no theoretical limit to distance. Bandwidth is limited by signal to noise ratio, but, given enough time, you can send any message. Search on Shannon-Hartley Theorem.
stretch's user avatar
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