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% Document Info
\author{MostAncientDream}
\pdfinfo{
  /Title (alvl-p2-telescopes-optional.pdf)
  /Creator (Cheatography)
  /Author (MostAncientDream)
  /Subject (Alvl P2: Telescopes (optional) Cheat Sheet)
}

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\noindent
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    \vspace{-7pt}
    {\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\noindent
        \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}}
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\begin{tabulary}{11cm}{L}
    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{Alvl P2: Telescopes (optional) Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{MostAncientDream} via \textcolor{DarkBackground}{\uline{cheatography.com/168994/cs/42317/}}}
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\noindent
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  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}MostAncientDream \\
  \uline{cheatography.com/mostancientdream} \\
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  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Not Yet Published.\\
   Updated 6th February, 2024.\\
   Page {\thepage} of \pageref{LastPage}.
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  %\includegraphics[width=48px,height=48px]{dave.jpeg}
  Measure your website readability!\\
  www.readability-score.com
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\begin{document}
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\begin{multicols*}{3}

\begin{tabularx}{5.377cm}{x{1.34379 cm} x{3.63321 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Overview}}  \tn
% Row 0
\SetRowColor{LightBackground}
Convex Lens & () - {\emph{*focuses}} incident light \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
Concave Lens & )( - {\emph{spreads out}}* incident light \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
Principle Axis & the line passing through the centra of the lens, 90' to its surface \tn 
% Row Count 7 (+ 3)
% Row 3
\SetRowColor{white}
Real Image & formed when light rays {\bf{cross}} after refraction \tn 
% Row Count 9 (+ 2)
% Row 4
\SetRowColor{LightBackground}
Virtual Image & formed on the same side of the lens, where the rays {\bf{dont cross}} \tn 
% Row Count 12 (+ 3)
% Row 5
\SetRowColor{white}
Power of a lens & a measure of how closely a lens can focus a beam that is parallel to the princple axis \tn 
% Row Count 15 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{1.94103 cm} x{3.03597 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Equations}}  \tn
% Row 0
\SetRowColor{LightBackground}
Lens formula- 1/f & 1/u +1/v -{}-{}-(where u is the d from object to centre of lens, v is image for centre and f is focal length) \tn 
% Row Count 5 (+ 5)
% Row 1
\SetRowColor{white}
Power (dioptres/D) & 1/f \tn 
% Row Count 7 (+ 2)
% Row 2
\SetRowColor{LightBackground}
normal adjustment & fo + fe (focal length till focal point + distance between focal point and distance to eyepiece)) \tn 
% Row Count 11 (+ 4)
% Row 3
\SetRowColor{white}
Anglar Magnication & angle subtended by image at the eye/ angle subtended by the object at the unaided eye \tn 
% Row Count 15 (+ 4)
% Row 4
\SetRowColor{LightBackground}
'' & fo / fe (where angles are less than 10') \tn 
% Row Count 17 (+ 2)
% Row 5
\SetRowColor{white}
minimum angular resolution & lambda / D (diameter of objective lens/mirror) \tn 
% Row Count 19 (+ 2)
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angle subtened & diameter x distance \tn 
% Row Count 20 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{with reference to minimum angular resolution -{}-\textgreater{} the smaller the angle the better the quality/resolution}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Adv of large diameter telescopes}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{{\bf{collecting power}}- a measure of the ability of a lens/mirror to collect incident em radiation (proportional to the area of the objective lens) \newline % Row Count 3 (+ 3)
{\bf{resolving power}}- ability of a telescope to produce separate images of close together objects  \newline % Row Count 5 (+ 2)
-for this to happen the angle between striaght lines from earth to object must be at least the minimum angular resolution 0 = lambda/D \newline % Row Count 8 (+ 3)
-this is also known as the {\bf{Rayleigh Critierion}} which states: \newline % Row Count 10 (+ 2)
{\emph{two objects will not be resolved if any part of the central maximum of either image falls within the first minimum diffraction ring of the other}} \newline % Row Count 13 (+ 3)
{\bf{CCD (charged couple device)}}- array of light-sensitive pixels, which become charged when they are exposed to light via photoelectric effect \newline % Row Count 16 (+ 3)
quantum efficiency-percentage of incident photons which cause an electron to be released \newline % Row Count 18 (+ 2)
spectral range- detectable rang eof wavlengths of light \newline % Row Count 20 (+ 2)
pixel resolution- total number of pixels used to form an image \newline % Row Count 22 (+ 2)
spatial resolution- minimum distance two objects must be apart to be distinguishable% Row Count 24 (+ 2)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
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\begin{tabularx}{5.377cm}{x{1.19002 cm} x{2.10542 cm} x{1.28156 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{3}{x{5.377cm}}{\bf\textcolor{white}{comparing CCD and human eye}}  \tn
% Row 0
\SetRowColor{LightBackground}
quantum eff & \textasciitilde{}80\% & 4-5\% \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
spectral range & IF,UV,visible & visible \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
Pixel res & varies but \textasciitilde{}50 megapixels & \textasciitilde{}500 megapixels \tn 
% Row Count 6 (+ 2)
% Row 3
\SetRowColor{white}
spatial res & 10 micrometers & 100 \seqsplit{micrometers} \tn 
% Row Count 8 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}---}
\SetRowColor{LightBackground}
\mymulticolumn{3}{x{5.377cm}}{CCD are more useful for detecting finer details and producing images which can be shared and stored}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}---}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Astronomical Telescopes}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{tba% Row Count 1 (+ 1)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{\textasciicircum{}Ray diagram for a refracting telescope in normal adjustment (c-PMT)\textasciicircum{} \newline  \newline Normal adjustment- when the distance between the lenses is the sum of their focal lengths  \newline    this means the principle focus for these two lenses is in the same place}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{More Telescopes}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{Refracting telescopes have two converging lenses \newline % Row Count 1 (+ 1)
- {\bf{objective lens}} used to collect light and create a real image of a distant object \newline % Row Count 3 (+ 2)
   \textgreater{} should have long focal length, large area to collect as much light as possible \newline % Row Count 5 (+ 2)
-{\bf{eyepiece lens}} used to magnify the image produced. it produces a virtual image at infinity since the light rays are parallel reducing eye strain. \newline % Row Count 8 (+ 3)
{\bf{collecting power}} is directly proportional to the square of the radius of the objective lens% Row Count 10 (+ 2)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Reflecting telescopes}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{Cassegrain Reflecting Telescope: \newline % Row Count 1 (+ 1)
- involves a primary concave mirror and secondary convex mirror \newline % Row Count 3 (+ 2)
Mirrors in relfecting telescopes are a thin coating of aluminium/silver atoms that are deposited onto a backing material \newline % Row Count 6 (+ 3)
- this allows the mirrors to be smooth and minimises distortion \newline % Row Count 8 (+ 2)
\textasciicircum{}need to know how to draw a diagram of cassegrain.\textasciicircum{} \newline % Row Count 10 (+ 2)
\textasciicircum{}points to note:\textasciicircum{} \newline % Row Count 11 (+ 1)
\textasciicircum{}- mirror curves are clearly shown\textasciicircum{}  \newline % Row Count 12 (+ 1)
\textasciicircum{}- add the eye piece at the end \textasciicircum{} \newline % Row Count 13 (+ 1)
\textasciicircum{}- rays have arrows and start parallel\textasciicircum{}% Row Count 14 (+ 1)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Comparing refracting/reflecting telescopes}}  \tn
% Row 0
\SetRowColor{LightBackground}
disadv of refracting & adv of reflecting \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
glass must be pure, free from defects (hard for large diameters) & mirrors are unaffected by chromatic aberr, spherical can be avoided using parabolic mirrors \tn 
% Row Count 6 (+ 5)
% Row 2
\SetRowColor{LightBackground}
Large lens can bend/distort under their own weight & mirrors are not as heavy as lenses therefore easier to handle and manoeuvre \tn 
% Row Count 10 (+ 4)
% Row 3
\SetRowColor{white}
affects by both chromatic and spherical aberration & though chromatic aberr can affect eyepiece, it can be solved using achromatic doublet \tn 
% Row Count 15 (+ 5)
% Row 4
\SetRowColor{LightBackground}
large magnifications require very large diameter obj lens with very long focal lengths & mirrors that are a few nm thick can be made and give esxcellent image quality \tn 
% Row Count 20 (+ 5)
% Row 5
\SetRowColor{white}
lenses can only be supported from the edges which is diffocult as they are heavy and large & large primary mirrors are easy to support from behind as you dont need to see through them \tn 
% Row Count 25 (+ 5)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
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\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Aberration}}  \tn
% Row 0
\SetRowColor{LightBackground}
Chromatic- & Spherical- \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
for a given lens the focal length of the red light is greater than the blue light meaning the y are focused at different points & the curvature of a lens/mirror can cause rays of light at the edge to be focused in a different position to those near the centre (outside has shorter focal legnth) \tn 
% Row Count 10 (+ 9)
% Row 2
\SetRowColor{LightBackground}
this can cause a white object to produce an image with coloured fringing & this leads to image blurring and distortion \tn 
% Row Count 14 (+ 4)
% Row 3
\SetRowColor{white}
as its caused by refraction it has little effect on relfecting telescopes and only occurs in the eyepiece lens & as its most pronounced in lenses with a large diameter it can be avoided completely by using parabolic objective mirrors \tn 
% Row Count 20 (+ 6)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Achromatic doublet}}- a way of minimising spherical and chromatic aberration in lenses  \newline  \newline - consists of a convex lens made of crown glass and a concave lens made of flint glass cemented together to bring all rays of light into focus at the same position \newline  \newline (imagine convex next to concave)}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Telescope types-}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{{\bf{radio}} \newline % Row Count 1 (+ 1)
- lowest energy,longest wavelength, can travel through dense interstellar clouds and allow to see motion of cold gas \newline % Row Count 4 (+ 3)
{\bf{infrared}} \newline % Row Count 5 (+ 1)
- used to see through cold dust in order to study warm gas/dust and relatively cool stars as well as molecular absorptions \newline % Row Count 8 (+ 3)
{\bf{visible}} \newline % Row Count 9 (+ 1)
- most stars emit the bulk of their em energy as, hotter-blue, colder- red \newline % Row Count 11 (+ 2)
{\bf{UV}} \newline % Row Count 12 (+ 1)
- emitted by the hot glow of the stellar nurseries and indentifies hottest/most energetic stars \newline % Row Count 14 (+ 2)
{\bf{X-ray}} \newline % Row Count 15 (+ 1)
- come from hottest gases that contain atoms, emitted from neutron stars or clouds of gas heated to millions of degrees including superheated material around a blackhole \newline % Row Count 19 (+ 4)
{\bf{gamma}} \newline % Row Count 20 (+ 1)
- highest energy, smallest wavelength, come from free electrons and stripped atomic nuclei accelerated by powerful magnetic fields in exploding stars, colliding neutron stars and supermassive black holes \newline % Row Count 25 (+ 5)
- also used to observe gamma ray bursts, quasars and black holes \newline % Row Count 27 (+ 2)
types of GRB: \newline % Row Count 28 (+ 1)
-{\bf{short lived}} \textgreater{} last between 0.01 and 1 second (associated with merging neutron stars/neutron str falling into a black hole) \newline % Row Count 31 (+ 3)
} \tn 
\end{tabularx}
\par\addvspace{1.3em}

\vfill
\columnbreak
\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Telescope types- (cont)}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{-{\bf{long lived}} \textgreater{} last between 10 and 1000 seconds (associated with a type 2 supernova-death of a massive star)% Row Count 3 (+ 3)
} \tn 
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\end{tabularx}
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\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Telescope types- Radio and optical}}  \tn
% Row 0
\SetRowColor{LightBackground}
similarities & differences \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
function in the same way- intercept and focus incoming radiation to detect its intensity & as radio is larger than visible, radio telescopes have to be larger in diameter to achieve the same quality/resolving power (as they have larger diameter they will have larger collecting power) \tn 
% Row Count 11 (+ 10)
% Row 2
\SetRowColor{LightBackground}
both can be moved to focus on different sources of radiation/to track a moving source & construction of radio is cheaper and simpler as a wire mesh is used instead of a mirror (mesh size must be less than lambda/20 to avoid refraction and reflect) \tn 
% Row Count 19 (+ 8)
% Row 3
\SetRowColor{white}
parabolic dish of radio is similar to objective mirror of reflecting optical & a radio must move across an area to build up an image unlike optical \tn 
% Row Count 23 (+ 4)
% Row 4
\SetRowColor{LightBackground}
both can be built on the ground since both waves can pass through the atmosphere & radio experiences large interferance from man-made sources, optical is only natural sources eg weather, light pollution \tn 
% Row Count 29 (+ 6)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}


% That's all folks
\end{multicols*}

\end{document}