LogFormDescription.tex

\section{Description of the form}
\begin{itemize}
\item \textbf{The title} carries the common name of the object (if
  any) and the primary catalog number
\item \textbf{The subtitle} specifies the \emph{type} of the object
  (eg: Planetary Nebula, Galaxy etc) and the constellation in which it
  lies.
\item \textbf{Icons indicating observability} are shown on the right
  of the page.

  \renewcommand{\arraystretch}{2.2}
  \begin{longtable}{c p{5in}}
    \begin{minipage}[c]{0.6in}
      \includegraphics[width=0.5in]{\binocularicon}
    \end{minipage}&
    Objects that are expected to be visible from dark sites with small
    binoculars (eg: $10 \times 50$) are indicated with this binocular
    icon. \\
    
    \begin{minipage}[c]{0.6in}
      \includegraphics[width=0.5in]{\eyeicon}
    \end{minipage}&
    Objects that are expected to be visible to the naked eye from dark
    skies ($\sim$ Bortle 3) are marked with this eye icon. \\

    \begin{minipage}[c]{1in}
      {\center
      \vskip 10pt
      \includegraphics[width=0.5in]{\cityicon}~
      \includegraphics[width=0.2in]{\telescopeicon}
      }
    \end{minipage} &
    Objects that are expected to be visible from city sites with smaller
    telescopes (eg: $4'' \sim 6''$) are indicated with this city skyline
    icon, accompanied by a small telescope icon. \\
    
    \begin{minipage}[c]{1in}
      {\center
      \vskip 10pt
      \includegraphics[width=0.5in]{\cityicon}~
      \begin{minipage}[c]{0.22in}
        \includegraphics[width=0.2in]{\binocularicon} \\ 
        \includegraphics[width=0.2in]{\telescopeicon} \\ 
      \end{minipage}
      }
    \end{minipage} &
    If the object is also expected to be visible in binoculars from city
    skies, a tiny version of the same binocular icon is displayed just
    above the telescope icon, next to the city skyline icon. \\

    \begin{minipage}[c]{1in}
      {\center
      \vskip 10pt
      \includegraphics[width=0.5in]{\cityicon}~
      \begin{minipage}[c]{0.44in}
        \hspace{0.22in} \includegraphics[width=0.2in]{\eyeicon} \\
        \includegraphics[width=0.2in]{\telescopeicon} \hspace{0.22in} \\
      \end{minipage}
      }
    \end{minipage} &
    If the object is also expected to be visible with the naked eye from
    city skies, a tiny version of the same eye icon is displayed next to
    the city skyline icon. \\
    
    \begin{minipage}[c]{1in}
      {\center
      \vskip 0.3in
      \Huge \textbf{--}
      \vskip 0.3in
      }
    \end{minipage} &
    If no icon is displayed, it indicates that the object most likely
    requires a telescope from dark skies, or data is unavailable about
    its visibility. Note that this should not discourage more advanced
    observers to attempt the object from city skies or with
    binoculars. Please consult various online forums for more
    information. Cloudy Nights
    (\url{http://www.cloudynights.com/ubbthreads/ubbthreads.php}) is one
    such forum.\\
  \end{longtable}
  \renewcommand{\arraystretch}{1.0}

\item \textbf{The data table} lists some useful data about the
  object.

  The first two rows list the RA and Dec, first current as of the date
  of compilation, and then J2000.0.

  The ``Size'' field lists the size of the object in
  arcminutes. Imagine fitting the object into a rectangle in the
  sky. The larger (usually first) dimension, called the \emph{major
    axis} specifies the length of the rectangle. The smaller dimension
  (\emph{minor axis}) specifies the breadth of the rectangle. For
  example, $8' \times 3'$ means that the object will roughly fit into
  a rectangle with a length of $8$ arcminutes and a breadth of $3$
  arcminutes in the sky.

  The ``Position Angle'' field specifies the orientation of the major
  axis of the object (the ``length'' of the rectangle mentioned
  above). It is measured in degrees, from North towards East. If it
  says $90\circdegree$, it usually is invalid / unknown.

  The ``Magnitude'' field specifies the magnitude of the
  object. Usually, this is the visual magnitude and not the blue
  (``photographic'' magnitude), except for some objects, usually
  indicated in the preface. Note this carefully, because the visual
  and blue magnitudes may differ somewhat substantially.

  The ``Other Designation'' field carries an alternate catalog
  designation of the object when available.

\item \textbf{The sky chart} shows a map of the sky around the
  object.

  \textbf{North is upwards} in the map.
  
  The circle in the center represents a \textbf{circle of $1\circdegree$
    diameter} on the sky.

  The black dots are stars. The green / red symbol in the center of
  the $1\circdegree$ circle represents the object. An effort is made to
  represent the size of the object accurately.

  The lines connecting stars are constellation lines, and help you
  visualize the constellations. Note that these are not standard and
  may differ across star charts. Always look up the name / designation
  of the star (or the RA/Dec of the object) to match against other
  charts.

  The fainter jagged, but solid, lines are the boundaries of
  constellations as defined by the IAU.

  The broken / dashed lines running up-down are lines of constant
  right ascension, just like longitudes on a map of the earth.

  The broken / dashed lines running left-right are lines of constant
  declination, just like latitudes on a map of the earth. If you see a
  thick horizontal line that extends through to the ends of the map,
  that represents the celestial equator. The celestial equator line
  has numbers marking hours of right ascension.

  The text in all block capitals (dark green) are the name of the
  constellation. Many a time you may see the text crossing a
  constellation boundary line -- the \textbf{name always refers to the
    constellation to the right side} of the name.

\item \textbf{A DSS image} is provided to give you a rough idea of
  what the object looks like. The appearance through your equipment,
  of course, could be drastically different depending on its
  capabilities! The DSS Image is an actual photo of the object taken
  with a fairly large, professional astronomical telescope. It is
  usually good to get a rough idea of what features may be visible and
  what may not be. Of course, it takes practice to realize which
  features in a DSS image you may actually expect to see through your
  telescope!

  The dimensions of the region of the sky in the image (in arcminutes)
  are specified below the image (eg: $30' \times 15'$). The first
  dimension is the width.

  Most of the time, blue POSS2/UKSTU DSS images are used. Red DSS
  images are used when the blue plates are unavailable. Blue plates
  will usually provide a better estimate of the observability of
  objects than red plates, as the eye is more sensitive to blue when
  in night-vision mode (``scotopic'' vision). However, it should be
  borne in mind that DSS images are not really calibrated. The letters
  `B', `R' and `I' in the caption of the DSS image, alongside the
  dimensions, indicate that the image is blue, red and infrared
  (respectively).

  In the DSS images, \textbf{north is upwards}, as with the map.

\item \textbf{The Observation Log} is where you log your own
  observations. Fill out the details as per your wishes. If you are
  using this logbook to earn a certification from some organization,
  please look up the organization's guidelines for logging. Sometimes,
  the log form may indicate fields that are required by the certifying
  organization -- but please double check the organization's
  guidelines to be sure.

\end{itemize}

\section{Using the form}

\subsection{Wide-field Charts}
To use these forms, you will need to have wide-field star charts
showing the constellations handy. Preferably the chart should have RA
and Declination markings.

If you do not have a star atlases, you may purchase several
commercially available star atlases, or print out the Free Mag 7 Star
Atlas hosted at
\url{http://www.cloudynights.com/item.php?item_id=1052}.

You could also use the wide-field star charts for the month, generated
by this website: \url{http://skymaps.com/}.

Note that some of the wide-field star charts are designed to be held
above your head and used -- the cardinal points on the map may align
up correctly only if you hold them above your head.

You may alternately also use computer software to obtain wide-field
views. There are several free, open-source options, the most
recommended for this purpose being Stellarium. Stellarium may be
obtained for a variety of operating systems at
\url{http://www.stellarium.org}. Other recommended options include
KStars -- \url{http://edu.kde.org/kstars} and SkyChart --
\url{http://www.ap-i.net/skychart/start}, which also run on a variety
of operating systems.

\subsection{Visibility of Objects}
To check if an object is visible at your latitude, you could find the
lowest declination you can see by the formula
\begin{equation}
\mathrm{Lowest\,Observable\,Declination} = 90\circdegree -
\mathrm{Observation\,Latitude}.
\end{equation}
Substitute your latitude without the sign, irrespective of whether it
is northern or southern. In the southern hemisphere, you'll get the
lowest northern declination visible. In the northern hemisphere,
you'll get the lowest southern declination visible.

If the object is in the opposite hemisphere to where you are
observing, check that its declination is closer to zero than the
Lowest Observable Declination you calculated above.

Often, you cannot observe objects that are too close to the
horizon. The atmosphere itself limits your observations somewhat to
about 5\circdegree above the horizon (this is a very ballpark
figure). Light-pollution domes can make things worse. Just subtract
the number of degrees you lose near the horizon from the Lowest
Observable Declination you calculated, to make your estimate more
practical. High altitudes can sometimes help lower the horizon, so
observing from a high altitude could add a few degrees to the Lowest
Observable Declination.

Objects that do not qualify the criterion you calculate above can
never be seen from your latitude, unless you fly pretty high above the
ground! So you can eliminate such objects from your observing list, or
save them for a cross-continental trip to the other hemisphere (or a
long trip to a more tropical region).

Other objects, while visible from your latitude, may not be visible at
the given time of the year etc. The best way to determine whether an
object is visible at a given time from a given latitude is to use
astronomy software. That is why knowing constellations is very helpful
-- so you can quickly figure out if a certain object is visible by
checking if the constellation in which it resides is
visible. Wide-field star charts generated for a given night (you need
one for the evening and one for the early morning next day) will be
able to help you quickly check up on visible constellations, so you
can plan your observation.

If you like rough estimates, you can make one by knowing the RA of the
sun. Block off 1 hour after sunset and before sunrise. 1 hour of time
(almost exactly) corresponds to 1 hour of RA so if the object's RA
lies outside this twilight zone, you are likely to be able to observe
it. This kind of an estimate does not work well at high latitudes, at
times away from the equinoxes. The use of computer software is
strongly recommended.

\subsection{Locating the Constellations, finding a reference star}
First, make sure you are aware of the cardinal directions around
you. 

In the northern hemisphere, an easy way to identify north is to look
for the Big Dipper, a famous asterism of 7 stars, that is part of the
constellation Ursa Major. If the Big Dipper is not visible, Cassiopeia
is a good alternative. The constellation has the shape of an M,
$\Sigma$, W or \reflectbox{$\Sigma$} depending on the orientation.

In the southern hemisphere, you may look for the Southern Cross (Crux)
to identify south.

Once you have identified north / south, also identify east / west and
find out if your wide-field chart is designed to be held above your
head and used.

Use your wide-field star atlas to identify the constellation patterns
in the sky. Remember that the constellation patterns differ across
various sky maps.

Prominent patterns that are easy to identify are the Great Square of
Pegasus, Cassiopeia, Orion, the head of Taurus the bull, Auriga, the
Southern Cross, the Big Dipper, Corvus, Scorpius, the Teapot in
Sagittarius. Use these as landmarks to find your way around the sky.

Identify a bright star (the bigger the circles, the brighter the stars
they represent), which we will refer to as the \emph{reference star},
within the finder chart embedded in the log. Locate the star in your
wide-field charts, and thereby locate it on the sky.

\subsection{Finding the object}

Once you have located the reference star, recalling that the sky maps
have north on the top, orient the book correctly to map what you see
in the sky with the sky chart in the logbook.

Then, a variety of options are at your disposal. One is to try to find
the location of the object in the sky precisely, by using a bunch of
stars, and point the telescope / binoculars to that location. For
example, if you see on the chart that the object is exactly between
two stars, you could just point your telescope exactly to that
location on the sky, using the two stars for reference. Another
technique is \emph{star hopping} -- work a route from the reference
star to the object using various other stars as landmarks.

Many an internet resource can help explain these techniques better.

Finally, you may need to pan the telescope a bit, or move your
binoculars around a bit to actually locate the object.

Remember that many telescopes and some finder scopes produce inverted
or mirrored images. Some people often find it useful to identify
unambiguous patterns that have directionality to them of stars and
just position relatively. Others like to orient the map correctly, and
then account for the reflection or inversion of their telescopes in
their head. If you would rather have an erect field, there are
erecting prisms available from many vendors for standard (1.25'' and
2'') telescope focusers.

If the object is rather faint, you may need to precisely zero in on it
by using the star field around the object. To see the star field
around the object, the easiest way is to use software. The DSS images
may occasionally help you in this regard.

\subsection{Observing the object}

\emph{Averted vision}, also known as \emph{peripheral vision} is an
important observing technique. Use internet resources to understand
and master this technique.

Note that the magnitude is not a true indicator of the brightness of
the object as seen with a telescope. A large object ``A'' with the
same magnitude as a fainter object ``B'', will appear much fainter
than ``B'' because the light is spread over a larger area.

In the description provided in the logging form, for some objects, you
may notice a number of abbreviations specified. These constitute J L E
Dreyer's description of the object, and these descriptions are very
helpful to get a feel for what the object actually looks like. Note
that J L E Dreyer had larger telescopes and was observing from dark
skies when making these descriptions. However, the descriptions are
more apt than magnitudes when determining how bright an object
is. Many resources on the internet have explanations for the
abbreviations used in Dreyer's descriptions. Here is one such
resource: \url{http://spider.seds.org/ngc/des.html}.

%% TODO: Add a section on logging observations, in general