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Topic: Arcseconds


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  Cool Cosmos
The angular measure of an object is usually expressed in degrees, arcminutes or arcseconds.
Just as an hour is divided into 60 minutes and a minute into 60 seconds, a degree is divided into 60 arcminutes and an arcminute is divided into 60 arcseconds.
To give you an idea of how small an arcsecond is, imagine the width of a dime as seen from 2 kilometers or 1 1/4 miles away.
coolcosmos.ipac.caltech.edu /cosmic_classroom/cosmic_reference/angular.html   (224 words)

  
  Arcsecond - Wikipedia, the free encyclopedia
A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7.7×10
The symbol for marking the arcsecond is the double prime (″) (
The double prime symbol is also used to denote the inch: this can, in certain contexts, cause confusion.
en.wikipedia.org /wiki/Arcsecond   (150 words)

  
 MCC-1 to TCS
The displacements sss.s arcseconds are with respect to the scan base position when using 1 for argument c, and are with respect to the previous scan position when using 0 for this argument.
The displacements sss.s arcseconds are with respect to the peak base position when using 1 for argument c, and are with respect to the previous peak position when using 0 for this argument.
The displacements sss.s arcseconds are with respect to the autoguider base position when using 1 for argument c, and are with respect to the previous autoguider position when using 0 for this argument.
irtfweb.ifa.hawaii.edu /~sears/Computer.html   (2732 words)

  
 Astronomy Answers: From the Astronomical Dictionary   (Site not responding. Last check: 2007-10-20)
A degree is further divided into 60 arcminutes (also written as 60' or 60 minutes of arc), and an arcminute into 60 arcseconds (also written as 60" or 60 seconds of arc), so one degree is equal to 3600 arcseconds.
It is about equal to 0.13 arcseconds divided by the diameter of the primary entrance of the telescope in meters, or to 130 arcseconds over the diameter in centimeters, or to 5.0 arcseconds divided by the diameter in inches.
Often, the resolution of telescopes is worse than what this formula yields, because the mirrors or lenses are not perfect and because the atmosphere of the Earth tends to blur the images.
www.astro.uu.nl /~strous/cgi-bin/glossary.cgi?l=en&o=angle   (327 words)

  
 Arcseconds Definition / Arcseconds Research   (Site not responding. Last check: 2007-10-20)
A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminuteA minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60) of one degree.
Since one degree is defined as one three hundred and sixtieth (1/360) of a circle, 1 MOA is 1/21600 of the amount of arc in a closed circle, or (π/10800) radians.
The parsec is defined to be the distance from the Earth of a star that has a parallax of 1 arcsecond.
www.elresearch.com /Arcseconds   (283 words)

  
 Polar Drift Alignment
We can calculate the time for a star to drift 1 arcsecond by simply inverting the drift rate.So, if the drift rate is 0.262 arcseconds per minute and we wait for 3.8 minutes, it will move by 1 arcsecond.
The number of arcseconds subtended by a pixel in the STV depends on the focal length of the optical system in front of the STV.
If we are trying to detect drift rates of 1 or 2 arcseconds per minute, this is a bit coarse but for many applications such as CCD imaging using short exposures where polar alignment is not so critical, this may be adequate.
mywebpages.comcast.net /astrophoto/Articles/Polar_Align.htm   (1372 words)

  
 EXSS - Einstein Extended Source Survey
The offset in declination of the aperture 1 detection from the adopted object declination (Dec) found using the technique described in the paper, in units of arcseconds.
The offset in declination of the aperture 2 detection from the adopted object declination (Dec) found using the technique described in the paper, in units of arcseconds.
The offset in declination of the aperture 3 detection from the adopted object declination (Dec) found using the technique described in the paper, in units of arcseconds.
heasarc.gsfc.nasa.gov /W3Browse/all/exss.html   (1013 words)

  
 Deep Impact: Discovery Zone: Mission Challenge   (Site not responding. Last check: 2007-10-20)
" is the angular diameter of the object, in arcseconds*.
The 206265 is a conversion factor that converts from radians to degrees, and then from degrees to arcseconds (it is equal to [360/2
What is the angular diameter, in arcseconds, of a HRI pixel?
deepimpact.umd.edu /disczone/challenge_FOV_A.html   (1081 words)

  
 2Mass Tile vs Reconstructed Positions   (Site not responding. Last check: 2007-10-20)
The nominal tile declinations were defined as the tile declination listed in the tile database plus 6 step distances (82.8 arcseconds per step is the value used for May observations) toward the equator on one end and the file database declination plus 6deg poleward on the other end.
Distances on the plots are in arcseconds, computed by subtracting the reconstructed position from the nominal tile position.
Tile declination at the edge farthest from the equator was calculated by adding 6 degrees to the declination given in the tile database for comparison to the corresponding scan declination.
spider.ipac.caltech.edu /staff/ldf/tile.html   (266 words)

  
 Anacortes Telescope & Wild Bird
That is, the size of a star's image in arcseconds when measured at half the maximum value for that star in a long exposure.
In this example the individual pixel field of view should be on the order of 1.3 to 0.86 arcseconds per pixel for an optimum balance of extended object sensitivity to resolution of fine detail.
If you aim for a pixel FOV of about 1 arcsecond per pixel through a given focal length, then you should be fine for the majority of typical sites and imaging requirements.
www.buytelescopes.com /container.asp?dest=/promo/Resolution.htm   (628 words)

  
 MAXIM Pathfinder
The problem is that to achieve adequate fringe magnification the beams must cross at a very low angle as shown in Figure 2.
To magnify 1 nm waves to 100 micron fringes requires a cross angle of about 2 arcseconds, which implies that L will be large.
The approach is to use a modest size Wolter telescope with arcsecond resolution (possibly a Chandra spare shell).
maxim.gsfc.nasa.gov /pathfinder.html   (2664 words)

  
 SLA_AFIN - Sexagesimal character string to angle
The first three ``fields'' in STRING are degrees, arcminutes, arcseconds, separated by spaces or commas.
If the arcseconds field is absent, the arcminutes is expected to be 0-59.9999...
The arcseconds field is expected to be 0-59.9999...
www.hartrao.ac.za /nccsdoc/slalib/sun67.htx/node15.html   (279 words)

  
 Measuring Angles in the Sky
To convert radians to arcseconds, multiply the radians by 206265 (thus 0.02 radian = 0.02 x 206265 = 4125.3 arcsec).
Conversely, to convert from degrees to radians we must divide by 57.295, and to convert from arcseconds to radians we must divide by 206265.
If we were to observe that star at six-month intervals, we would be looking at it from two points in space that are separated by the diameter (twice the radius) of the Earth's orbit.
www.geocities.com /angolano/Astronomy/PIinSky.html   (1381 words)

  
 Optimal tiling geometry for ALFA surveys
The average beam is itself an ellipse with average minor and major axis of 204 and 232 arcseconds, these are generally aligned with the same direction as the ellipse defined by the outer beams.
Keep in mind that the size of the "circles" in Figure 5 is 256 arcseconds in the vertical axis and 219 arcseconds in the horizontal axis, which is slightly larger than the half-power axis of ALFA's beams (232 and 204 arcseconds respectively).
Keep in mind that the size of the "circles" in Figure 6 is 221 arcseconds in the vertical axis and 190 arcseconds in the horizontal axis, which is slightly smaller than the half-power axis of ALFA's beams.
www2.naic.edu /~pfreire/tiling   (1725 words)

  
 The 2.5-meter Telescope
The ray trace image sizes are less than 0.6 arcseconds RMS over a three-degree field at the design wavelength, and are less than 0.7 arcseconds RMS in any of our filter passbands over the imaging wavelength range of 3500 to 9300Å.
The bottom panel shows the images as delivered by the design optical system; the top as convolved with 0.8 arcsecond Gaussian seeing, which we believe will be the worst seeing we will have to cope with in the photometric part of the survey (see Chapter 1).
Greyscale PSFs for the field angles in the table are shown in Figure 2.4, and convolved with 1.5 arcsecond Gaussian seeing; the images are 6 arcseconds apart in the mosaic, and the circles are three arcseconds in diameter, the input diameter of the fibers.
www.astro.princeton.edu /PBOOK/telescop/telescop.htm   (8813 words)

  
 Telescope Optics & Pixel Size
Mountaintop observatories often have 1 arcsecond (or better) seeing, whereas typical backyard observing sites at low elevations in towns or cities might have 3 to 5 arcsecond seeing.
A good rule of thumb to avoid undersampling is to divide your seeing in half and choose a pixel size that provides that amount of sky coverage.
For example, if your seeing conditions are generally 4 arcseconds, you should achieve a sky coverage of 2 arcseconds per pixel.
www.ccd.com /ccd113.html   (977 words)

  
 Is Pluto An Ethane Fuzzball
Subaru also obtained spectal signatures for the two bodies that clearly reveal a very different make up for the two distant and highly eccentric bodies that are suspected by many as been super Kuiper objects.
At this distance, Pluto and Charon had apparent diameters of 0.08 and 0.04 arcseconds, respectively.
Although these CISCO observations are among the best ever taken from the ground (with a resolution of about 0.35 arcseconds), they are not sharp enough to show the true disks of either Pluto or Charon.
www.spacedaily.com /news/pluto-99b.html   (541 words)

  
 Sacramento Peak: Glossary   (Site not responding. Last check: 2007-10-20)
It is about equal to 0.13 arcseconds divided by the diameter of the primary entrance of the telescope in meters, or to 130 arcseconds over the diameter in centimeters, or to 5.0 arcseconds divided by the diameter in inches.
A parsec (abbreviated pc) is the distance at which a star or other object shows a parallax due to the motion of the Earth around the Sun of one arcsecond.
The proper motion of a star or other celestial object is its motion along the sky, measured in units of angle per time period (e.g., arcseconds per year).
www.sunspot.noao.edu /PR/zoo.html   (8728 words)

  
 Earth Rotation and Equatorial Coordinates
For the purposes of pointing a telescope to one-arcsecond accuracy, we need not worry about shape and surface feature changes, but changes in the orientation of the earth's rotation axis are very important.
The RORF is stable to at least 0.020 arcseconds per century, and this is improving with better observations and a longer time base.
Because of internal motions and shape deformations of the earth, an axis defined by the locations of a set of observatories on the surface of the earth is not fixed with respect to the rotation axis which defines the celestial pole.
www.cv.nrao.edu /~rfisher/Ephemerides/earth_rot.html   (2028 words)

  
 Spring Double Stars: The Three Leaps of the Gazelle
The components of nu are magnitudes 3.8 and 10.0, separated by 7 arcseconds.
This easy triple system's A and B components of magnitudes 4 and 9 are 22 arcseconds apart; the magnitude difference is enjoyable.
100 arcseconds from the A star is the magnitude 10.5 C star.
www.theskyscrapers.org /content2097.html   (421 words)

  
 Will It Fit on the Chip?  Pixel Scale   (Site not responding. Last check: 2007-10-20)
Students understand that pixel scale is an angular measure of sky subtended by the telescope/CCD system and is dependent upon the actual size of the pixels and the focal length of the telescope.
For the purpose of this activity where we are not attempting to determine the actual size of the object, just the angular size, it is more convenient to have answers in arcseconds or arcminutes.
In the case of determining pixel scale, the amount of sky subtended by the pixel is equal to the width of the pixel (D).
hou.lbl.gov /~vhoette/Explorations/OpticalPowers/9a-pixelscale.html   (1594 words)

  
 BMWHRICAT - Brera Multi-scale Wavelet (BMW) ROSAT HRI Source Catalog
In the original table this was given in J2000 equatorial coordinates to a precision of 0.1 arcseconds.
For each HRI event file, the catalog authors extracted and separately analysed 4 concentric images at increasing rebinning factors of 1, 3, 6, and 10, corresponding to pixel sizes of 0.5, 1.5, 3 and 5 arcsec, respectively, in order to follow the instrumental PSF and to avoid the analysis of unnecessarily large images.
The sigma of the source extent as derived from the fit procedure, in arcseconds.
heasarc.gsfc.nasa.gov /W3Browse/all/bmwhricat.html   (2466 words)

  
 CARA Science: Seeing: Optical and Infrared
Both differential image motion observations and direct measurements of turbulence show that the seeing during the winter at the South Pole is approximately 1.7 arcseconds at visual wavelengths at a height of 12 meters above the snow surface.
Almost all of the turbulence causing the seeing is located in the lowest 200 meters of the atmosphere, where wind velocities are typically less than 7 meters/sec when the sky is clear.
The data show that the turbulence causing the seeing is strongly concentrated in the lowest few hundred meters of the atomosphere, as expected from the altitude profiles of temperature and wind shear.
astro.uchicago.edu /cara/research/site_testing/seeing.html   (899 words)

  
 LEDAS: ARNIE5 Database Search
The density of such objects within x arcseconds of the radio detections is compared with their whole-sky density, and the same for the X-ray detections.
The angular distance from the HRI detection to the optical object, in arcseconds.
The correctness of the technique is seen with any number of spot checks, such as the HRI NGC 3628 field US700009H.N1 which has been shifted in RA by +5.8 arcsec (where positive means eastwards) and in declination by -14 arcsec (negative is southwards) to become well-aligned with 5 known quasars in the field.
www.ledas.ac.uk /arnie5/arnie5.php?action=help&catname=qorgcat   (4131 words)

  
 Digitized Sky Survey - Wikipedia, the free encyclopedia
They scanned plates using one of two Perkin-Elmer PDS 2020G microdensitometers.
The pixel size was 25 or 15 micrometres, corresponding to 1.7 or 1.0 arcseconds in the source material.
The scanning resulted in images 14,000 x 14,000 or 23,040 x 23,040 pixels in size, or approximately 0.4 and 1.1 gigabytes each.
www.wikipedia.org /wiki/Digitized_Sky_Survey   (544 words)

  
 Debunking the Moon Hoax
Astronomers refer to angular size in "arcseconds." There are 3600 arcseconds in a degree.
The moon moves across the sky at a rate of 0.5 arcseconds per second due to its orbit around the Earth.
The Hubble telescope is not programmed to correct for that motion, and any pictures of the moon are blurred a bit because astronomers have to make a guess as to how to tell the telescope to move while taking a picture.
www.ucolick.org /~robin/moonhoax.html   (566 words)

  
 Effects of Mars Rotation on Planet Imaging
Image smearing is dependent upon the arcseconds of planet movement from first to last image and the imaging equipment’s resolution in arcseconds of per pixel.
Using the below table there was approximately 0.217 arcseconds of planet movement or about three pixels of planet movement at the center of Mars over the six minutes of images.
The second assumption is using the Sin function to calculate the arcseconds of movement as seen from Earth.
www.stargazing.net /david/mars/marsrotation.html   (581 words)

  
 how to determine encoder resolution
For example, == if we wanted a position accuracy of 0.1 arcseconds, how may counts == per arcseconds is required by a servo system (standard PID servo = controller)?
The higher the better and at 2.777778e-005 it would be absolute resolution of +/- 0.05 arcseconds per BIT in count, if I did this right.
For example, if we wanted a position accuracy of 0.1 arcseconds, how may counts per arcseconds is required by a servo system (standard PID servo controller)?
www.ee-one.com /new-5317797-4307.html   (1627 words)

  
 2.
While there is no absolute answer to how many arcseconds a pixel should span for deep sky imaging, a good starting place is about 2 arcseconds per pixel for moderate size amateur scopes.
Most amateur instruments and observing sites would be doing quite well to achieve an FWHM of 3 arcseconds in long-exposure images, so a pixel resolution of 1.5 arcseconds per pixel is usually more than satisfactory.
If the imager can manage it, a system designed with a modest degree of oversampling (e.g., one arcsecond per pixel) is ready for those nights of exceptional seeing and provides more useful data for some image processing algorithms, such as deconvolutions.
www.ghg.net /akelly/telescop.htm   (1394 words)

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