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Topic: FWHM

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	FWHM
		The technical term Full-Width Half-Maximum, or FWHM, is used to describe a measurement of the width of an object in a picture, when that object does not have sharp edges.
		An alternative, which better reflects the approximate size of the star's image as seen by the eye, is the width across the profile when it drops to half of its peak, or maximum, value (shown in the graph above).
		In the usual sort of astronomical image, the FWHM is measured for a selection of stars in the frame and the "seeing" or image quality is reported as the mean value.
	www.noao.edu /wiyn/images/fwhm.html (245 words)

	FOCUS TESTS - i' (Site not responding. Last check: 2007-10-14)
		FWHMs were grouped at each focus position and a 3-sigma clipped < FWHM > and sigma were computed.
		For each chip, the < FWHM > and < delta-Mag > as a function of focus were fit with a parabolic function and the focus value at the resulting fit's minimum was recorded.
		Compare the best FWHM plots for image 758036x where the bottom row is the worst with the plots for image 757084x where the top row is the worst.
	orca.phys.uvic.ca /~neill/SNLS/FocusTests (346 words)

	New Page 1
		The lowest FWHM value for star #1 is in image #5, while the lowest FWHM value for star #2 is at image #4.
		The FWHM values have been multiplied by 10,000 in an Excel spreadsheet to get all values on roughly the same scale; this does not affect the relative values in each series.
		FWHM all at the same time in order to decide when best focus is achieved.
	www.newastro.com /newastro/book/C2/chapter2_P5.asp (821 words)

	FWHM curve (Site not responding. Last check: 2007-10-14)
		The inspection of the atmospheric structure and dynamics shows that the principal peak of the observed FWHM curve occurs exactly during the very short phase of the line doubling induced by a shock.
		We should note, however, that the value of the calculated FWHM minimum is not only model dependent, but also depends on the accuracy of the numerical description of the physical conditions in the LFR.
		The discrepancy between the predicted and observed FWHM at this phase is mainly due to the discrepancy in the dynamical characteristics of the model and the real star.
	www.obs-hp.fr /www/preprints/pp118/node4.html (1098 words)

	David's Astronomy - Notes 2002-01-31 (CCD Imaging Performance, 2001-Oct to 2002-Jan)
		FWHM of images taken during last 4 months varies from around 4.0 to 5.6 arc secs, with best of around 3.5 arc secs to date.
		FWHM is calculated in arc secs, by multiplying the 'FWHM_Image' (in pixels) by the image scale (in arc secs/pixel) which is appropriate to the image.
		FWHM values determined will be not only be related to seeing, but also related to focusing, and tracking/guiding errors.
	www.richweb.f9.co.uk /astro/notes-2002-01-31.htm (1088 words)

	FMRISTAT
		Fmrilm: The fwhm of the spatial smoothing of the autocorrelation parameters is now chosen by default to achieve 100 df or 90% of the residual df of each contrast.
		The estimated fwhm of the data is fwhm_data=8.7855mm, and the amount of smoothing chosen for the autocorrelation parameters is fwhm_cor=12.4444mm.
		The random noise in the FWHM is measured by the degrees of freedom of the linear model used to estimate it.
	www.math.mcgill.ca /keith/fmristat (10024 words)

	GONG IRAF help pages (Site not responding. Last check: 2007-10-14)
		The output image may be produced such that nu1, npc and npts match those of some already existing spectrum by setting match to the name of that image.
		Create a spectrum with Nu0 = 3025., FWHM = 1.75, amplitude = 33.5 and no asymetry where the first pixel is at 3000 microHZ, dispersion = 0.05 microHZ and the spectrum is 1024 pixels long.
		FWHM = 1.75, total integrated power = 300., and asymmetry = 0.01 where the first pixels is at 1500 microHZ, dispersion = 0.25 microHZ and the spectrum is 2048 pixels long.
	gong.nso.edu /data/iraf_help/mklorentz.html (382 words)

	Resolution
		FWHM measures how much the light is spread out at half the maximum counts for the star.
		FWHM is a measure in pixels across the graph at one half the height of the peak.
		In this activity students practice calculating FWHM using three images of the ring nebula, taken with a 2 inch, 6 inch, and 24 inch telescope aperture.
	hou.lbl.gov /~vhoette/Explorations/OpticalPowers/8-resolution.html (2477 words)

	FWHM in CCD Images
		FWHM (Full Width at Half Maximum) in CCD Images and the Detection of pixel defects
		The "Curve of Growth" plot (on the left) shows a rapid drop in the number of spots found when the FWHM threshold is raised from 1.0 to 1.2.
		Above a FWHM threshold of 1.2 nearly all the pixel defects have been excluded and most of the stars are still found.
	www.geocities.com /openmindxx/fwhm.htm (805 words)

	Temperature variations inside the dome
		The mean FWHM in a half-night interval is written simply as FWHM, and the standard deviation is written as sd(FWHM).
		In some cases, the FWHM increases by as much as 0.1 arcsec when sd(dT_xy) is increased by 0.5 deg (for example, see dT_13).
		It is also interesting to note that FWHM increases as a function of dT_01 and dT_02, but decreases as a function of dT_03.
	www.cfht.hawaii.edu /~kamson/seeing/temp_variations.html (688 words)

	3.2. int_fwhm
		For each one of the arc image, a mean value of the FWHM and the standard desviation is obtained from the different FWHM values.
		These outfiles contain the FWHM values of the gaussian fits for the different emission features whose coordinates are in P_file.
		A mean value of the FWHM and the standard desviation for each one of the arc image is showed too.
	www.iac.es /project/integral/red_man/node11.html (301 words)

	fwhm man page (Site not responding. Last check: 2007-10-14)
		For each plane in the input cube, it com- putes the fwhm in x, y, and an average of both measurements, around a single user-provided peak (see options -x and -y) or an automatically detected list of peaks (see options -d and -s).
		For a data cube in which the peak is offseted a lot from image to image, increase this value.
		The method which is used to determine bright objects in an image is the same as in detpeak.
	www.eso.org /projects/aot/eclipse/man/fwhm.html (471 words)

	[No title]
		The measured FWHM can be decomposed into two parts, one that represents the rocking curve normal to the crystal surface, and one that is parallel to the crystal surface.
		The FWHM that is normal to the surface represents edge dislocation, while the FWHM that is parallel to the surface represents screw dislocation.
		The surface normal FWHM is also called the twist component because the edge dislocation creates a slight angle in the lattice, causing a twist in the structure.
	www.phy.ilstu.edu /~intreu/marcusProj.htm (1273 words)

	HETGS Resolution, 2/27/01
		The resolution of the spectrometer is specified by the FWHM of the core and the core plus wings are relevant to accurate line flux measurements.
		The discrete FWHM measurements (of the MARX simulation data) that were used to generate the polynomial fits are shown by the asterisk and diamond symbols.
		These FWHM values are in the range between the values derrived from the pre-flight expectations for optimistic and conservative E/dE, as shown by the dashed and dotted lines in the plots.
	space.mit.edu /HETG/technotes/ede_0102/ede_0102.html (1106 words)

	Measurement of Action Potential-Induced Presynaptic Calcium Domains at a Cultured Neuromuscular Junction -- DiGregorio ...
		The gaussian curve (solid red), yielding an FWHM (arrow) of 0.86 µm, was fitted to the data points between, and including those, enclosed in cyan circles.
		The FWHM of 0.68 µm (arrow) was obtained from linear interpolation between data points.
		The open circles represent FWHMs obtained from simulations using the same sizes of Ca entry sites, except that the x-dimension of the detection volume was set to 0.1 µm.
	www.jneurosci.org /cgi/content/full/19/18/7846 (7668 words)

	CPET - Reconstruction Filters, Image Resolution, ROI size, etc. (Site not responding. Last check: 2007-10-14)
		N=1 is an ROI whose width is identical to the PSF FWHM, N=2 is an ROI whose width is twice the PSF FWHM, etc. These ROIs are drawn inside the phantom and plotted at arbitrary heights to give you a feel for how big (x-dimension) they are relative to the actual phantom.
		Note, however, that even with a small ROI whose width equals the FWHM of the PSF, there is only a very restricted range of locations on the image where the ROI will correctly reflect the activity levels in the original source.
		Of course things become more complex when your source is surrounded by other sources of activity since they may artificially extend what you think is the 100% level region if their activity levels are the same as those of your target source.
	www.nucmed.buffalo.edu /rcnflt1.htm (2873 words)

	Intrinsic Seeing at the WHT Site
		It is important to note that the observed image FWHM will be equal to that predicted by this equation only if there is no contribution to image width from other sources such as telescope focus or tracking errors.
		The principle of the DIMM is to measure the variance of the differential centroid motion for images of a star produced separately from two apertures of known separation within the entrance pupil of a telescope.
		The DIMM FWHM prediction assumes that the spatial spectrum of wavefront aberrations is well described by the Tatarski structure function.
	www.ing.iac.es /Astronomy/development/hap/dimm.html (1186 words)

	Focus Analysis for Gratings, etc.
		It has 1-D FWHM's of 37-38 microns and an encircled fraction of 63.8% (.ps,.gif) in one arcsecond (relative to 10 arcseconds = 1.00) for energies between 0.73 and 1.13 keV and nominal grade set, 02346.
		The focus data sets were analyzed for the FWHM in the dispersion direction by rotating the sky X,Y coordinates by 220 degrees to put the jet at the position angle it has in the TDET coordinates.
		The FWHM of this projection is measured as 2.35 times the best-fit Gaussian sigma.
	space.mit.edu /HETG/technotes/acis_fwhm_focus/acis_fwhm_focus.html (611 words)

	Powder diffractometers performances as estimated by the Rietveld method
		A good equilibrium between FWHM and Rp is essential not only to refine a structure but also to determine a structure ab initio from powder diffraction data.
		Finally, the results on FWHM and Rp proposed in the posting were from data measured on a Siemens D5000 with variable incident and scattering slits set to V6/V6 (6mm), Peltier cooled Si(Li) detector.
		The Scintag results on the point of view of FWHM are fine, they are the best at large angle, however, Rwp is really too high (may be the reason is not only difficulties in profile fitting, very poor statistics may have also such a consequence).
	www.cristal.org /powdif/low_fwhm_and_rp.html (3805 words)

	Sampling Saturn
		This is generally taken to mean that there should be two or more pixels per FWHM (Full Width at Half Max) of the diffraction disk, though there's differing opinion that it should simply be more than 3 pixels per FWHM.
		When we use a window (pixel width) that's half the FWHM we find that the reduction in contrast is actually quite small (from 95% to 90%).
		It now becomes very obvious that sampling with one pixel-width per FWHM is very destructive of contrast but that two pixels per FWHM is still very much in the running.
	www.geocities.com /ultimaoptix/sampling_saturn.html (1134 words)

	CfAO - Astronomical Adaptive Optics Demonstrator - Experiments
		The first number is the FWHM in the X-axis, while the second number is the FWHM in the Y-axis.
		We made a plot of the FWHM versus aggressiveness for all 20 exposures (Graph 2.1).
		We determined the X FWHM for a star in each exposure and made a bar graph of the data (Graph 4.1).
	www.ucolick.org /~aodemos/labs/labs.html (2203 words)

	Turbulent velocity variation (Site not responding. Last check: 2007-10-14)
		peak may probably be the result of underestimation of FWHM due to certain nonadequacy of the description of this very fast phase of model pulsation.
		), for the observed FWHM is a result of integration of the flux over the whole LFR.
		A characteristic feature of RR Lyrae atmospheres is that at the compression phase, the deeper layers are more accelerated by gravity than the upper ones due to considerable extention of the atmosphere.
	www.obs-hp.fr /www/preprints/pp118/node5.html (321 words)

	DeepZoom (Site not responding. Last check: 2007-10-14)
		This is because with better seeing (smaller FWHM) the photometry signal aperture circle can be smaller, and since it will include fewer pixels, the thermal (stochastic) noise from the smaller number of pixels will be smaller (and proportional to the square-root of the number of pixels in the signal circle).
		The ratio of my FWHM to that for the HST was 11.1 (for this particular observation).
		I've also used a value for the HST's FWHM is 0.24 "arc which I derived from an image I downloaded, and my FWHM measure varied with brightness and star color.
	www.brucegary.net /deep_zoom (1494 words)

	NICMOS IHB for Cycle 14 (Site not responding. Last check: 2007-10-14)
		The FWHM is defined as the intersection between the transmission curve and the half-maximum-transmission value.
		Since the transmission curve shape is strongly affected by the DQE (particularly for the broad filters), the measured FWHM will change with temperature.
		This is NOT the FWHM value returned by the bandpar task.
	www.stsci.edu:8082 /hst/nicmos/documents/handbooks/current_NEW/Appendix_A.html?printable=1 (490 words)

	AUTOFWHM (Site not responding. Last check: 2007-10-14)
		This is most easily done by using echelle_over.pro to produce a format plot that nearly matches the image.
		This emission lines that you identify in this step are the ones whose FWHM will be measured in the next step.
		I recommend identifying only those lines that are relatively strong, well separated, and not very close to either end of each order.
	hires.gsfc.nasa.gov /stis/software/autofwhm.html (741 words)

	Correlations with other parameters? (Site not responding. Last check: 2007-10-14)
		We test this claim by looking at the FWHM as a function of time relative to the beginning of the night, which we fix to be at 8pm HST.
		We find that FWHM generally increases by about 0.1 arcsec towards the end of the night, contradicting our original expectation.
		Initially, we suspect that this effect is correlated with temperature fluctuations inside the dome, such as the primary mirror warming up the temperature of its surroundings.
	www.cfht.hawaii.edu /~kamson/seeing/other_param.html (397 words)

	IDL Help
		;+ ; NAME: ; ; FWHM ; ; PURPOSE: ; ; Interactively measure the full-width-half-max of a region of a ; curve that has been previously plotted.
		To use FWHM with a non-interactive ; graphics device, range MUST be supplied.
		The region is highlighted, and the ; fwhm is labelled.
	www.astro.washington.edu /deutsch-bin/getpro/library08.html?FWHM (706 words)

	[No title]
		For emission lines where only an upper limit on Flux and EW is available, no values for the VPeak are quoted as the position of the line was fixed at the line's expected wavelength.
		Also, the FWHM value in this case was set to the median value for the LBQS sample (see Table 3, Paper~II) with no associated errors.
		In addition to this, a two letter designation is used for the spectra indicating that the spectra are from a post-COSTAR observation (o) and whether there is more than one spectrum of the same object (a-z).
	hea-www.harvard.edu /~pgreen/Papers/postcos.tablenotes (267 words)

	CSO Heterodyne Receiver Beam Efficiency Measurements
		FWHM Beam Size on Mars: 33.4" (Same for 3/01 and 3/99)
		Beam Effieciency: 69.8% (32.5" FWHM beam from 3/01)
		Beam Effieciency: 50-53% (16.5" FWHM beam on 3/99)
	www.submm.caltech.edu /cso/receivers/beams.html (170 words)

	[No title]
		The syntax of the UNIX call is thisprog {glb} fwhm [range]
		The second command line argument 'fwhm' must be a floating point number larger than zero, which is used as the full width at half maximum of the instrument function.
		The standard output does not contain the comment lines of the input or any characters that were following the original pair of input data.
	www.strw.leidenuniv.nl /~mathar/progs/convol.c (672 words)

	SIGNAL - ING exposure-time calculator (Site not responding. Last check: 2007-10-14)
		The calculations can be carried out for point sources, with specified FWHM and apparent magnitude; or for extended sources, with specified apparent mag per square arcsec.
		The image FWHM (seeing convolved with object size) is now used to determine both vignetting by the slit and the number of pixels over which to integrate for point-source observations:
		The slit-width is now used both to determine the intensity of the signal from (uniformly) extended objects, including the sky, and to calculate vignetting (for point sources).
	www.ing.iac.es /~crb/signal.html (1808 words)

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