Term
| one key difference between equitorial and horizen cooridanate systems is....? |
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Definition
with the horizen system changes with time
the equitorial coordiante system does not change with time |
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Term
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Definition
| the HA of the vernal equinox |
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Term
How do you determine the LST at any point on earth?
aka LST=? |
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Definition
| LST=UT@Greenwich-Longitude+Delta(T) |
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Term
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Definition
| Delta T is there to to cancel out the solar time interval, so when using delta T is is crucial to change it to Sidereal time |
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Term
| If an object has an hour angle which is negative, what does that imply? |
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Definition
| Thats implies that the object is east of the meridian |
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Term
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Definition
| Amount of EM radiation (energy) from a celestial object |
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Term
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Definition
| Photometry is the science of measuring the amount of flxs from celectial objects |
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Term
Photometry has high....?
low....? |
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Definition
High flux calibration
low wavelength resolution |
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Term
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Definition
| combination of high flux calibration and good wavelength resolution |
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Term
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Definition
Good wavelength resolution
poor flux calibration |
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Term
| equation relating magnitudes and fluxes |
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Definition
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Term
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Definition
| Represents the total amount of energy put out by an object over all wavelengths |
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Term
Bluer objects have ? (B-V) magnitudes
Redder objects have ? (B-V) magnitudes |
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Definition
bluer have smaller B-V
redder have larger B-V |
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Term
For a Cssigran Telescope
the primary mirror is ?
the secondary mirror is ?
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Definition
Primary is Parabolic
Secondary is Hyperbolic |
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Term
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Definition
| the objects closer to the edge of the image produced are blurred (not sharp) due to lights rays entering the telescope off axis and not focusing with others to make a clear image |
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Term
RC telescopes
primary mirror?
secondary mirror?
whats special? |
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Definition
Hyperbolic primary and secondary mirror
no coma aberration |
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Term
| Scale (of an image) is proportional to ? |
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Definition
| scale is proportional to focal length |
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Term
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Definition
= f/206265
where f is focal length |
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Term
Resolution of a Telescope = ?
aka alpha = ? |
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Definition
| alpha =2.1E5(wavelength/Diameter) |
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Term
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Definition
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Term
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Definition
| mb-mv=m2-m1 from the magnitude luminosity relationship |
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Term
| A yellow star (B-V=0.63) has ? wavelengths as flux increases |
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Definition
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Term
| A blue star (B-V=-0.33) with increasing flux has ? wavelengths |
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Definition
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Term
| If you want to add magnitudes, what must you do to obtain the answer? |
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Definition
| Add the fluxes and then solve for a single magnitude from the added fluxes. |
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Term
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Definition
| the distance from the lens to the image plane |
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Term
| A telescope with a low F-ratio is said to be what? |
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Definition
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Term
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Definition
| wavelengths interferring destructivly at certain points, think single aperture with a point source of light. |
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Term
Full Width Half Maximum
(FWHM) |
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Definition
| the angluar size of the star image at half the peak level |
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Term
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Definition
| the fraction of photons falling on a CCD that are actually detected |
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Term
| why do thick CCD's (front illuminated) has bad QE in the blue wavelengths? |
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Definition
| the electronic layers the light has to pass through to get to the silicon abosrb much of the blue wavelengths. |
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Term
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Definition
| If you allow a CCD to integrate without any light, the there is still a noise read out due to thermal excitation of the electrons in the CCD. this noise is the read out noise |
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Term
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Definition
Exposing the CCD to uniform light, by doing this one can correct any non-uniformity in the CCD.
nonuniformities can be caused by varying thickness in the silicon, telescope optics, ect |
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Term
| List the zodiacal constellations in order starting from the autumnal equinox meridian one. |
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Definition
Libra
Scorpio
Sagittarius
capricorn
aquarius
pisces
Aries
Taurus
gemini
cancer
leo
virgo |
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Term
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Definition
| when electrons are emitted (escape their atom homes) due to the absorbtion of the right amount of EM radiation |
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Term
| Describe how a CCD works. |
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Definition
| photons hit silicon. Photoelectric effect occurs, and the free electrons are collected in a pixel. Exposure ends and voltage potential is applied, moving the individual pixels across the CCD to the output register. Collected charge is measured in Voltage and converted to an output digital # |
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Term
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Definition
| The amount of voltage(collected Electrons/recieved photons) needed to produce 1 ADU |
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Term
| draw back of surface channel CCD's? |
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Definition
| some of the transferring electrons are caught in the gate structures (due to imperfections in the CCD) |
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Term
| Buried channels are good because? |
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Definition
| They elimate gates catching electrons. |
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Term
down side of back side illuminated CCD's?
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Definition
-Shallower pixel wells
-Greater chance of non-uniform surface
-more expensive |
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Term
| How do you try to over come the low QE of blue light in CCD's? |
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Definition
Coating more sensitive to blue light
back illuminated CCD |
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Term
| Explain the Charge Transfer in CCD's |
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Definition
row of pixels is shifted off array to serial register
each pixel is SR is shifter to readout amplifier
charge in each pixel is read as a voltage and amplified
an ADC converts the voltage to ADU's |
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Term
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Definition
| detected photons/incident photons |
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Term
what are some reason photons
would not be detected? |
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Definition
pass through
absorbed in gates
reflected off |
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Term
Define Charge Tranfer Efficiency
(CTE) |
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Definition
| amount of charge succesfully tranfered to next pixel during readout |
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Term
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Definition
| the number of electrons introduced during readout time |
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Term
| Define Full Well Capacity |
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Definition
| the amount of electrons each pixel can hold |
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Term
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Definition
| Full Well Capacity / Largest ADU output from AD converter |
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Term
| For N* in the CCD equation, the units come in the form of e-/ADU, what do the units have to be in? |
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Definition
| they should only be in e-, so multiply out by how many e-/ADU there are. |
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Term
What does Npix stand for
in the CCD equation? |
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Definition
| N pix is the number of pixels used in the aperture |
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Term
| To turn a number, say N* in to the units required, you need to multply it by...? |
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Definition
| by the gain, which is in units of e-/ADU's |
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Term
| using the S/N equation, how do you determine the uncertainty magnitude? |
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Definition
| Flip the equation, so instead you have the N/S equation |
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Term
| what units is gain measured in? |
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Definition
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