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2 votes
1 answer
83 views

What are the reference signal(s) for a closed-loop space-based adaptive optical system?

Closed-loop control systems in general have the following form: Here the controller seeks to eliminate or minimize the difference between a given signal (this can be either a constant signal of the ...
3 votes
0 answers
460 views
+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 ...
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 ...
13 votes
2 answers
2k views

What on-site equipment is installed with radio telescopes?

I hope this question isn't too broad. I'd like to know something about radio telescopes, precisely what equipment they have. When I search "radio telescope control room" in image search ...
9 votes
3 answers
1k views

At the intersection of engineering and astronomy in its structure as a scientific discipline

Astronomy is the comprehensive study of what lies beyond the Earth. Modern astronomy (I relied on classifications from here and here) is divided into a large sections (astrophysics, astrogeology, ...
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 ...
5 votes
3 answers
683 views

What is the detection threshold of gravitational waves for LIGO?

Since now two neutron stars have been detected merging via gravitational waves, I was wondering what is the current detection threshold that the LIGO detectors can achieve. Considering that the first ...
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 ...
2 votes
0 answers
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 ...
3 votes
1 answer
86 views

Why is plasma used to deposit aluminum on the VLT's four large mirrors?

In Tim Scott's October 2, 2023 video "The largest telescope that will ever be built*" (note the asterisk, link below) there is a discussion of the "re-silvering" of the four main ...
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 ...
6 votes
1 answer
5k views

How to calculate luminosity in g-band from absolute AB magnitude and luminosity distance?

How can I calculate the (non-bolometric) luminosity $L$ of a galaxy (or a star for that matter) over a given band from its AB apparent magnitude $m_{AB}$ over that band and its luminosity distance $...
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 ...
7 votes
1 answer
157 views

SKA 101: How will it "perform the most precise tests of Einstein's theories" and Australia & South Africa arrays be "made to work seamlessly together"

The BBC's December 7, 2022 SKA: Construction to begin on world's biggest telescope includes the following: It will perform the most precise tests of Einstein's theories and The first major ...
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 ...
1 vote
0 answers
79 views

Ritchey–Chrétien telescope with a short back focus

I have an observing project that requires a 30 -- 40 cm (12 -- 16 inch) diameter primary and no refractive/transmissive elements (i.e. lenses). Telescopes like this Ritchey–Chrétien has a back focus ...
3 votes
1 answer
67 views

Is "monochromatic source" different than "monochromator" in astronomical instrumentation?

I got a comment to replace "monochromator" by "monochromatic source" for a paper on an astronomical instrument. The latter seems less specific for no reason. Is there an agreement ...
5 votes
1 answer
195 views

What leads an observer to choose a narrow slit over a wide one (and vice-versa) when observing?

In spectroscopy, a wide slit will lead to lower spectral resolution while too narrow of a slit will reduce incoming flux from the object. From what I read, it appears as though there is always a ...
6 votes
0 answers
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 ...
6 votes
1 answer
122 views

How do astronomical spectrometers measure spectra from single stars separately, without contamination from all of the nearby stars?

I am currently looking into light spectrometers, and I noticed that the ones I found had a similar problem; when the light reaches the spectrometer, it mixes giving a broad range of light wavelengths. ...
2 votes
0 answers
106 views

Different types of line broadening in stellar and galactic spectra

When analyzing stellar and galactic spectra with spectrographs, the spectral lines get broadened from the instrument. Why do the spectral lines get broadened after the light moves through the ...
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 ...
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 ...
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 ...
11 votes
1 answer
767 views

How exactly did JWST take a "selfie" of its own primary mirror, and what is the real purpose of this capability?

CNN's Webb telescope's first test images include an unexpected 'selfie' says only: The mirror selfie was captured by a special lens inside NIRCam that can image the primary mirror rather than what ...
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 ...
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 ...
8 votes
2 answers
1k views

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 ...
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 ...
1 vote
1 answer
85 views

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 ...
2 votes
1 answer
103 views

What telescopes used 1000+ pixel Microwave Kinetic Inductance Detectors (MKIDs) for multispectral, single photon counting (time + energy of photons)?

This excellent answer to What would “the next GAIA”-like instrument be like? Could it simply be a 3 to 5x scaled-up version of the same beautiful system? is worth a thorough read-through, but it and ...
1 vote
1 answer
61 views

What is a photoelectric scanner?

I am reading this article by Wing, Peimbert and Spinrad, where they mention the use of a photoelectric scanner. By searching online, I find that photoelectric scanners are used to scan punchcards, ...
3 votes
0 answers
67 views

What exactly causes very bright sources, such as supernovae, to appear as large circles in photographs?

Consider images such as those in https://hubblesite.org/contents/news-releases/2021/news-2021-007, which show bright supernovae embedded in their host galaxies. No matter which telescope and which ...
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 ...
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 ...
0 votes
1 answer
48 views

What is Hubbles WFC3 "UVIS 47 G200" filter? What is it used for? How to find an example?

Extensive reading for 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? led me to ...
1 vote
1 answer
93 views

How to determine the color term for a filter with a systematically bluer offset than the standard

This is a hypothetical scenario in an attempt to test my understanding of the color term when performing photometric calibrations: Imagine we are observing stars through a B filter with an offset ...
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 ...
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 ...
1 vote
0 answers
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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 ...
4 votes
2 answers
278 views

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 ...
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 ...
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 ...
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)...
2 votes
0 answers
62 views

What happens to the Fourier Transform of the Measured Spectrum?

What happens when you double the width of the entrance slit of a spectrograph, in turn letting in twice as much light, would there be an improvement in the Fourier transform of the measured spectral ...
0 votes
1 answer
73 views

Hypothetical CMB space telescope design problem, received power from extended thermal source versus receiver front end NEP?

Consider the example of a large radio dish antenna in space equipped with a heat shield protecting it from the Sun. Let's say the amplifiers front-end effective temperature (for purposes of noise ...
8 votes
1 answer
478 views

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 ...
7 votes
1 answer
804 views

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 ...
3 votes
1 answer
135 views

Number of lenslets in wavefront sensor array

I have to do a short calculation, but, quite frankly, I have no idea how to even start... Suppose you have a 10-m telescope (f/10) with an infrared camera that observes at 10 micrometer. The seeing is ...
6 votes
1 answer
290 views

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-...