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How does ALMA produce stable, mutually coherent ~THz local oscillators for all of their dishes?

The ALMA (Atacama Large Millimetre/submillimetre Array) radio telescope's band-10 capabaility is now operational, per this answer. That's confirmed by NRAO's First Science with ALMA’s Highest-...
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4 votes
2 answers
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What would a kHz gravitational wave detector look like? (mountains on millisecond magnetars) How would it differ from LIGO/Virgo?

The abstract of Gravitational waves from mountains in newly born millisecond magnetars says: In this paper we study the spin-evolution and gravitational-wave luminosity of a newly born millisecond ...
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3 votes
2 answers
349 views

Is the difference between LIGO & Virgo and their "Advanced" versions really generational, or were these just planned incremental upgrades?

I just learned the term "third generation gravitational wave detector" in answers to What would a kHz gravitational wave detector look like? (mountains on millisecond magnetars) How would it ...
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8 votes
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Has Hubble photographed Venus in near IR? If so how does it compare to the new and exciting Parker Solar Probe image?

Phys.org's Parker Solar Probe offers stunning view of Venus includes the image below taken by the Parker Solar Probe during it's most recent gravitational assist flyby of Venus as it continues to rid ...
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5 votes
4 answers
612 views

How can Mercury's sodium tail be imaged?

I recently learned that Mercury has a sodium tail. Can this sodium tail be imaged with a ground based telescope? Is so, what is the minimum setup required to be able to take a picture of it? Do you ...
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4 votes
1 answer
166 views

Why does X-shooter use double passes through prisms for Echelle cross-dispersion instead of gratings?

The catchy title Down-the-barrel observations of a multiphase quasar outflow at high redshift: VLT/X-shooter spectroscopy of the proximate molecular absorber at z=2.631 towards SDSS J001514+184212 ...
uhoh's user avatar
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2 votes
1 answer
108 views

Is Sofia a radio telescope proper?

I usually think of SOFIA, the Stratospheric Observatory for Infrared Astronomy as an infrared optical telescope: SOFIA uses a 2.5 m (8.2 ft) reflector telescope, which has an oversized, 2.7 m (8.9 ft)...
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2 votes
1 answer
303 views

What is the large astronomical instrument shown in this 1918 eclipse expedition photo?

This nice video musing about (among other things) the US Naval Observatory's $3,500 expedition to Baker City or at least Baker County Oregon to observe the June 18, 1918 solar eclipse, there is a ...
uhoh's user avatar
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11 votes
1 answer
610 views

Was GRAVITY built to look at one star?

GRAVITY (shown below) is a interferometric combiner of near infrared light from four very large telescopes called The Very Large Telescope in order to make careful astrometric measurements near the ...
uhoh's user avatar
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8 votes
2 answers
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Which JWST instrument modes are compatible with observations of the bright trans-Earth planets Mars, Jupiter, and Saturn? Which aren't?

My comment says: ...answers to the Space SE question Can James Webb take pictures of our solar system? In what ways will they differ from/compliment those from Hubble? suggest that at some point JWST ...
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6 votes
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190 views

What are the pros and cons of different types of echelle spectrograph cross-dispersers?

Echelle spectrographs, operating at high resolving power, typically consist of an echelle grating with a low numbers of lines/mm, used with high diffraction orders (often $n=$50-100). To separate the ...
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6 votes
0 answers
343 views

What would go into the design of a simple sky quality meter, used to measure night sky brightness?

@MCG's answer mentions several methods to classify night sky quality or brightness, and goes on to say: Additionally, you could always purchase a SQM (Sky quality meter) which is a small, portable ...
uhoh's user avatar
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3 votes
1 answer
153 views

Time domain astronomy and fastest eclipsing binary ZTF J1539+5027 (+20 mag, 6.91 minutes): How to measure its minimum brightness?

Per Wikipedia's ZTF J153932.16+502738.8 ZTF J153932.16+502738.8 is a double binary white dwarf with an orbital period of just 6.91 minutes. [...] The light curve shows eclipses. One dip in the light ...
uhoh's user avatar
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3 votes
1 answer
171 views

Are the dispersion directions of the prism and the grating in Hubble WFC3 UVIS G280 perpendicular? Can we call this a "grism"? With cross-disparsion?

Prologue From Into the UV: A precise transmission spectrum of HAT-P-41b using Hubble's WFC3/UVIS G280 grism: The UVIS grism, however, comes with several quirks that make it difficult to observe with ...
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+200

How does the ESPRESSO Echelle spectrograph fold the spectrum so nicely?

The CBC News Technology and Science Q&A This ESPRESSO machine doesn't make coffee but scans the skies for habitable planets includes a nice description of ESPRESSO (Echelle SPectrograph for Rocky ...
uhoh's user avatar
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3 votes
0 answers
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How were "microshutters" or other multiplexed or multi-object techniques first used in Astronomical spectroscopy?

This answer to How will microshutter arrays be used in the James Webb and future space telescopes? explains how multiple objects can be selected so that the throughput of a spectrometer can be ...
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1 vote
1 answer
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Did astronomers ever use photographic plate rotation along with alt-az mounts?

The video Earth's Rotation Visualized in a Timelapse of the Milky Way Galaxy - 4K (linked below) and discussion below this answer to Why does a timelapse video of a stationary Milky Way make the ...
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14 votes
1 answer
463 views

How do radio astronomers avoid having their receivers burned out by ground-imaging radar from satellites?

After about 34:00 in the 9th press conference of AAS 235, radio astronomer and NRAO's spectrum manager Harvey Liszt talks about Radio Astronomy in a New Era of ...
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11 votes
3 answers
1k views

Why (the heck) is the basic angle of GAIA 106.5°?

This answer to Why does the Gaia space telescope have two main mirrors says: According to the GAIA FAQs which does an excellent job: http://www.cosmos.esa.int/web/gaia/faqs: Why is there an angle of ...
uhoh's user avatar
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8 votes
3 answers
406 views

Is there a limit to the distance of detectable gravitational wave events?

This is somewhat a follow up question to this one. This article indicates that the binaries detected have a distance between 320 and 2840 Mpc. With the current technology, is there a limit to the ...
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7 votes
1 answer
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How could a 20 inch space telescope "be able to make out Earth-size planets" orbiting Alpha Centauri?

The NY Times article Telescope to Seek Earthlike Planet in Alpha Centauri System describes a proposed effort to put a telescope into orbit fairly quickly with a narrowly defined purpose - to look for ...
uhoh's user avatar
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7 votes
1 answer
209 views

Did they ever figure out why Parker's WISPR cameras were able to see the surface of Venus? Mischaracterized filter, or unexpected atmospheric window?

Credit: NASA/Johns Hopkins APL/Naval Research Laboratory/Guillermo Stenborg and Brendan Gallagher Also refer to the technical material cited in the Space Exploration SE question How brightly does ...
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6 votes
1 answer
143 views

Do circa 1 THz radio telescope front end amplifiers actually down convert before amplifying? At what frequency does amplification become untenable?

A discussion of how astronomers view where "radio" ends and "infrared" begins under What does the celestial sphere look like in thermal IR? led me to wonder just how high of a ...
uhoh's user avatar
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4 votes
2 answers
245 views

Formation of spacecraft instrumentation [closed]

List of spacecraft instruments are selected to meet a mission's science goals. Let's take New Horizons as an example and study the composition of Pluto's atmosphere, the shape and geological ...
ayr's user avatar
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3 votes
2 answers
343 views

What is an "Off Rowland-circle Telescope"? Are there "On Rowland-circle Telescope" as well?

The NASA Goddard news item NASA to Demonstrate New Star-Watching Technology with Thousands of Tiny Shutters says: The technology, called the Next-Generation Microshutter Array (NGMSA), will fly for ...
uhoh's user avatar
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2 votes
1 answer
116 views

How does IXPE measure polarization, and why does it have three identical X-ray telescopes?

From The Observatory: Anyone who missed any of the AAS 239 press conferences can see them on the AAS Press Office's YouTube channel! Here's the full program. From there I found the Monday, January ...
uhoh's user avatar
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2 votes
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165 views

Are astronomers still using photomultiplier tubes for optical photometry?

In Time domain astronomy and fastest eclipsing binary ZTF J1539+5027 (+20 mag, 6.91 minutes) How to measure it's minimum brightness? I've written A logarithmic magnitude scale might tend to show ...
uhoh's user avatar
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2 votes
1 answer
125 views

What was the first use of time-delay integration in Astronomy? Are there instances before GAIA?

In the context of GAIA, time-delay integration is the clocking of a CCD's charge shift register at a frequency such that it matches the linear speed across the focal plane of the actual image. So even ...
uhoh's user avatar
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2 votes
1 answer
178 views

How many science instruments can be used in parallel with the Hubble Space Telescope?

The Hubble Space Telescope offers a parallel obervation mode. Observing programmes such as CANDELS and CLASH use WFC3 and ACS in parallel fields. These are also the only instruments of which I have ...
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1 vote
0 answers
42 views

Astrophysical particle spectroscopy; narrow-line particle sources (charged or uncharged) for things other than photons? Have any been detected?

Is Cosmic Ray Astronomy a thing? Is there an equivalent of the red shift effect for cosmic rays? have got me thinking and under this answer I've commented: That's a good point; there aren't as many ...
uhoh's user avatar
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0 votes
1 answer
56 views

Instead of a five-element corrector for arced drift trajectories, why didn't the ILMT just use CCDs fabricated w/ slightly non-cartesian pixel layout?

Phys.org's New Indian telescope identifies its first supernova links to the recent arXiv Follow-up strategy of ILMT discovered supernovae. The International Liquid Mirror Telescope is no ordinary ...
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