When Lunar Calculator starts up with its factory defaults, you will see a "low power naked eye view" image of the Moon, from my backyard in Edmonton, Alberta, Canada:
If you do not have the Lunar Calculator or Clementine CD-ROM (or the image data on your hard drive), the software will still be able to simulate a realistic "USGS-Clementine blended" view, but at a maximum resolution of 3.0 km or 1.8 mi per pixel.
Before you end your first session, you will want to modify the settings to fit your location and time zone (see the end of this chapter) but for the moment, let's explore!
You can re-size the window with the standard "click and drag" of a corner; you can also maximize by using the middle of the 3 buttons on the upper right of the window bar. You can also choose to create a large image (up to 2000x2000 pixels). Click here for more info.
The information on the left stays in place. The image window will remain square, with the width of the image controlled by the width of the main window. The calculate button turns yellow to remind you to re-create the image before moving on after re-sizing.
You can toggle grid and crater overlays on and off with the buttons at left. The grid color and crater brightness can be changed in the settings window.
The white dot, visible only at “low power”, shows which limb of the Moon is tilted towards earth. From our earthbound perspective, the Moon seems to slowly rock from side to side and up and down by a few degrees. This so-called libration is an important parameter to the serious lunar observer because it tells them when features near the limb are in a good position.
There are 4 main ways that Lunar Calculator portrays the Moon. There is a simple "wire frame" view that displays very quickly. The Clementine spacecraft view shows the Moon under high solar illumination, that is, away from the terminator. Another view uses the classic USGS (United States Geological Survey) shaded relief "texture" map, which shows craters and highlights with a "morning solar illumination" which is great for the evening terrestrial observer. The best overall view is with the USGS-Clementine blend, because it more closely approaches the view in a telescope, with craters near the terminator and "albedo" features farther away. The dynamic shading of the USGS relief map ensures that the simulation on days following full phase is more realistic, that it doesn't suffer from sunlight coming the "wrong way".
The Moon has a "dual personality": craters and shadows are easy to see near the day/night line called the terminator, but farther away or at full Moon, they can be invisible! Features or areas which have dark/light contrast zones, like rays, are the opposite: easy to see at full Moon, but almost invisible at crescent phase. Most lunar atlases or charts depict the craters with shaded relief and also try to show the rays, with varying success.
One of Lunar Calculator's strengths is the ability to zoom in on a real image of the Moon, a mosaic of images taken by NASA's Clementine spacecraft. One of the results from Clementine was a (nearly) complete photographic coverage of the moon at constant illumination, and full moon was chosen with the sun as high in the lunar sky as possible. At full moon, many craters disappear because there are no shadows.
Clementine was not able to provide 100% coverage of the moon at full phase. To keep the dataset pure, the scientists decided not to merge in low resolution or low sun angle data. More information can be found in the Clementine section.
For more information, see the detailed section on Clementine images.
Yes, you must use the Contrast/Brightness window, which you access through the Edit menu.
Zoom: You can use “left-click and drag” to create a “zoom box”. If the zoom box is less than 5 pixels across, I assume that you made a mistake and don’t want to zoom in that much. You can also choose the “magnifying glass” (on the toolbar at the top of the image, or on the left side) and click on the place that you wish to be in the center of the zoom. You can modify the various zoom factors to suit your taste.
Ctrl-o = zoom out by a constant factor
Ctrl-i = zoom in on center of image with a constant factor
Ctrl-m = zoom in with your preferred magnification (configurable; factory default 350x)
New with version 2.3 is a navigation window. When you zoom in, a box shows your location.
You can change the color of the box (in settings), resize the window, place it anywhere on your screen and it will return there the next time you start up Lunar Calculator (assuming you save on exit).
Magnification: by clicking on the magnification,
you can directly enter a value then move your mouse to the point that you want in the center and click. , You can also choose magnification from a drop down list (configurable). Zoom and magnification are tied together. Zoom of 1 = 50x; Zoom of 3 = 150x; Zoom of 10 = 500x.
You can change the zoom settings through the "Edit" menu. For more information, see the detailed section on Zoom and magnification.
NOTE: the Clementine imagery on this CD-ROM has a maximum resolution of 0.5km/pixel, or 0.3 miles/pixel. You can zoom in more, but there will be no more added detail.
Center: right-click and choose “Center” to put the clicked spot in the middle. There is no change of magnification. You can also center with the icon on the toolbar.
When you move the mouse over a crater, the name shows up in a “pop-up” label, as well as at the upper left in the information column. You can choose to always have the “pop-up” label on or off, via the “Edit” menu. There are over 7000 features in the database, so to avoid overcrowding, Lunar Calculator automatically filters out the smaller features at lower levels of zoom. You can change this under Edit --> Settings.
Right click to identify: if you see a feature that interests you but no name shows when the cursor is on it, you can right click and choose identify. This pops up a window with a list, starting with the closest object in the complete 7000+ feature database. You can use the arrow keys to scroll through the list, and the pointer/cursor will jump to that feature on the moon. There is an "Identify" help section.
Ctrl-f (or Menu --> Search) allows you to search for an object by name in the full feature database (including mons/recta/vallis/rima etc). Click on the object of choice, then click OK. More detailed information can be found in the "Find" section.
More detailed information can be found in the Information section [LINK].
Time/Date: when the cursor/pointer is not on the moon, the Lat/Lon information disappears, and the time information appears. “Current time” inputs the time from the computer clock and calculates an image. When you change any part of the date, the “Calculate” button appears. Click it to re-calculate for the new date/time.
Loc/UTC: You can choose (via menu Edit --> Settings) if the time used is UTC or local time. Note that western time zones are negative! You must also choose what your offset to UTC.
Lat/Lon of the cursor/pointer: You can choose between decimal degrees and deg/min/sec. The extra precision needed at high power is automatic! The chart number refers to Antonin Rukl’s “Atlas of the Moon”. When the mouse pointer is close to a crater, the name, lat/lon, and size are displayed. If “Crater label” is checked (menu Edit Crater label) a “pop-up” label with the crater name appears. Click on the menu item to toggle it on and off.
Solar Alt/Az: the altitude and azimuth of the sun is calculated as seen from the current lat/lon.
Sunrise/Sunset: this displays the upcoming sunrise/sunset (in local or UTC) for the point in question. This will be an estimate because it assumes a flat lunar surface, and we all know that mountain peaks get sunrise first and sunset last compared to the lower terrain around it.
Colongitude: when the pointer is not on the moon, the colongitude is displayed. This is the lunar (selenographic) longitude where sunrise is occurring. Although lunar longitude, like earth longitude in the ISO system, is positive eastward (and west negative), the colongitude is opposite, increasing positively westward. This is one of the most important numbers for the lunar observer, because it pins down the sunrise longitude quite accurately, unlike the age of the moon.
Future colongitude: to find future dates when the moon has the same illumination, click on the colongitude value/button.
Solar latitude: this is the latitude on the moon for which the Sun is overhead. It is analogous to the Sun's declination on Earth. Interestingly, the Moon’s axis is only 1.5 degrees inclined to the ecliptic, so the Sun is always close to the Moon’s equator.
Illumination: the percentage (by area) of the Moon's disk in sunlight.
Libration Topocentric/Geocentric: libration is how much the Moon’s axis is tilted towards or away from Earth. The value displayed here is the total sum of the optical and physical components. If you had chosen geocentric (menu Edit Settings) , then geocentric values will be displayed. Normally you will want topocentric because it shows the Moon from your location. Both north/south and east/west components are displayed, along with a position angle and amount. See the libration section for more details. You can check the amounts of physical and optical libration separately (menu Output --> Display data).
RA & Dec: the equinox 2000 coordinates of the Moon are for your location (topocentric), unless you have chosen geocentric. If you want to compare the values to ephemeris tables, then choose geocentric. Remember when doing comparisons to set your time to UTC, and switch to JDE or TT if necessary.
Alt & Az: the altitude and azimuth of the Moon at your site.
Rise and Set: The rise and set times for the Moon are listed for your time zone for the calendar day (or UT if you are in UT mode). If there is only one event that day, then the time is listed for the event on the following day, including the calendar day added on the front to avoid confusion.
Age: the number of days since new Moon. If you want an easy way to find young or old Moons, check out the Crescent Search (Young/Old Crescent Search, http://www.) section.
Show Craters/Grid/Clear: these buttons allow you to toggle the grid and crater overlays on and off. In wire view, craters are on all the time.
% earthshine: For realistic images, you can set the % earthshine to suit your taste.
Directions/Orientation: This icon shows the current orientation of the lunar image, in celestial coordinates, not lunar coordinates. This way, at the telescope you should not get confused that lunar east is celestial west. You can flip/invert the image from the menu item View.
Zoom: how much relative to the start you are zoomed in. Zoom and magnification are tied together. Zoom of 1 = 50x; Zoom of 3 = 150x; Zoom of 10 = 500x.
Field: the true field of view of the width of the window, in arcminutes and arcseconds.
Magnification: an approximate value of the magnification you would see at your telescope. If you click on the magnification button, you can set the window to whatever value you wish. You can configure the pre-set choices via the Edit menu.
Custom Zoom buttons: there is a panel containing 6 zoom buttons. You can increase/decrease the magnification by fixed amounts. For example, if you were at 400x, you could click on the 1/2x button instead of clicking on the magnification button and entering 200x. The values are configurable via the Edit menu.
As you saw above, there are "hot keys" available for zooming. There are others, including find/search and libration graphs. For details, see the hot key section.
You should enter your location and time zone right away. You can set preferences such as visibility of grid and crater overlays, size of craters for specific magnifications etc. Click OK to use these new settings. A detailed explanation on settings is available.
You MUST still save these changes when exiting the program! You can always change any setting at a later date by clicking on the "Edit" menu item and choosing "Settings".
Just below the main menu bar, you can find a row of "speed buttons" that help minimize the number of clicks. They take you directly to where you want to go:
From left to right, they are:
Normal pointer, go to low power, zoom in, zoom out, re-center, libration graph, and libration search.
If you have kindly supported my efforts, you will have been provided with a "security key" that unlocks various features in Lunar Calculator, including accessing high resolution images and complete time flexibility. To enter the security key, click on File:
A small window pops up, you type in the code (CasE iS iMpoRtaNt!), hit okay, and you will notice the "Lite" disappears from the title bar. Don't forget to save when you exit, so the code will be placed in the configuration file ("LUNARCAL.CFG").