John Pazmino
 NYSkies Astronomy Inc
 2009 December 26
    At the NYSkies Astronomy Seminars, talks at other astronomy clubs, 
and presentations at conferences, I am commonly asked about my 
slideshows. In years before about 2005 there were built from chemofilm 
pictures -- color slides -- and assembled into a rotary tray for 
projection. Since the mid 20-thous my slideshows are built from 
computer images, which is by now almost the only way to offer shows.
    While i do not take myself to be the master of slideshow 
presenters, I am credited for giving talks that are highly welcomed, 
with requests for a repeat in a future occasion. With my own shift to 
digital photography and computer graphics, I find that my slide shows 
are vastly more specific for the audience to hand and I have orders 
greater selection of prime pictures for them. 
    Yet, and this surprises many in the audience, it is indefinitely 
easier for the lay person to compile a good slideshow with computer 
images than it ever was with chemophotography. 
    I deal here pura mente with slideshows, a sequential display of 
still images, like those of the optical-mechanical slide projector. I 
leave out use of audio and video or interactive techniques here. In 
spite of the increasing availability and ease of these more advanced 
techniques, overwhelmingly as at yearend 2009 an astronomy slideshow 
is a series of still pictures. 
    In the modern means of building slideshows, a slide is just an 
other computer picture. It doesn't HAVE to hold a picture. It can be a 
video or audio file. I just as yet didn't need to include such extra 
bells & whistles in my talks. They are static pictures thru and thru. 
    When the slideshow file is played, you index from slide to slide 
by a keypress at the computer, similar to working a film-based slide 
projector. If you prefer, the host can detail an agent to work the 
computer while you narrate and cue for the next slide. It is common 
for the astronomer to be at the screen, away from the computer, to 
better point out features in his pictures. 
Presentation software 
    Just about every digital slideshow is made in one format, a PPT 
file that plays with Microsoft's PowerPoint. You can build slideshows 
with other applications but they will play ONLY with them. For sure 
they will NOT play on your host's computer. 
    While PowerPoint is THE means of compiling slideshows there is at 
least one workalike. The free software OpenOffice is a set of business 
programs parallel to Microsoft Office. The module corresponding to 
PowerPoint is Impress. It is cosmeticly different from PowerPoint but 
it has all of its features for making and playing slideshows. It 
outputs the finished show as a PPT file for playing on a regular 
PowerPoint host. 
    Office, with PowerPoint, is almost never included with the 
computer as purchased. It is a commercial product that you buy at a 
nasty high price. Newer computers may include a PowerPoint player that 
ONLY plays existing PPT files, those you download or borrow. They can 
NOT create new ones. 
    If you do career-related work at home or field your company may 
issue MS Office to facilitate that work. Install it on your home 
computer, under agreement with your boss, for the occasions you do 
company work there. 
    Colleges may offer MS Office in a slim version on CD with a 
student discount. The school's edition may include templates and forms 
for your work. Some of them may be handy for making slideshows. 
A real kludge 
    In the absolute absence of PowerPoint, Impress, other slideshow 
application, you can give a show with WordPad. This is part of Windows 
as a basic word processor that allows pictures to be included in your 
documents. The effect during projection is untidy, but it does work. 
    Your slideshow is a document consisting of your pictures laid into 
it in the presentation sequence. You manipulate them with the word 
processing features, like cut & paste, scaling, rotating, and so on. 
    The trick is to scale the pictures to be EXACTLY one field high. 
When you do 'PgDn' WOrdPad indexes to the next picture with no overlap 
beyond the screen borders. 
    You have all of the program's Windows dressing on the projection 
screen, which absorbs some of the screen's real estate. In a pinch, 
this method of slideshow honestly does the job. 
    The one crucial factor is that you must build the slideshow on a 
computer that you bring to the host. It is VERY risky to bring the 
slideshow file to play on the host's computer. Oh, it WILL play, but 
the screen resolution, fonts, margins, Windows gadgets, other display 
parameters will surely differ from yours and corrupt your show. 
    All in all, you BETTER get hold of PowerPoint, Impress, other 
program that makes and plays PPT files. 
Digital pictures 
    By the 1990s computers could collect pictures from the first digital 
cameras as computer files. In the early years, cameras tended to use 
proprietary formats for their pictures, requiring the use of their 
special software. Pictures could not be exchanged among computers 
without this software.. 
    This situation quickly vanished when the JPEG standard was 
adopted. Today all digital cameras output their images in JPEG (or 
JPG) form. Picture handling software accept JPG files for easy moving 
around thru electronic means. 
    The opening of the Internet in 1993 for public use broke all 
barriers to exchanging digital images. They were attached to email and 
posted in  websites. My colleagues simply make a file copy of the 
picture I request and send it to me by email. Or they give me the link 
to the picture in their website. 
    Cameras improved, too, from the clumsy bulky expensive units of 
the 1990s to truly tiny and cheap models today. It is now usual for 
people to carry a digital camera with them all the time, a practice 
only occasionally done for a film camera for its weight and size. Now 
in the 20-thous there is the convergence of mobile computer and 
telephone that includes picture-taking features. 
Camera pictures 
    Considering now the real digital or 'silicon film' pictures, there 
are many sources. First is the camera image. This is a picture you 
shoot thru your camera. 'Camera' is very broad, and becoming broader 
every year. It's any device that 'takes a picture' like a camera. The 
device is small and light enough to carry to the target and capture 
its image. A camera can be en embedded photography feature of an other 
electronic device.  
    It may be a picture of real scenes. It can be a picture of 
television screens, books and magazines, signs, other pictures, 
tabletop mockups, It can be posed like a group photo or award 
ceremony. The image is captured in the usual picture-taking mode thru 
your camera. 
    Be SURE your camera is saving the picture in JPEG or JPG form. 
While this is not the very best way to save a digital image, because 
it throws out detail during its saving process, it is the universal 
format for just about all computer handling. Look thru the camera's 
menus and verify that you ARE capturing JPEG/JPG images. You could be 
in for a real irritating surprise later if the pictures are in some 
cockamamie format that no computer program can decipher. 
Scanned pictures 
    These are pictures scanned of a target. 'Scanner' is here a 
general term for a picture capturing device to which the target is 
brought. It then is placed on or in the device to capture the image. 
    It can be a regular scanner, acting much like a photocopier with a 
glass window, lid, crawling light. You can scan just about anything 
more or less thin and flat. It may be pages from books and magazines, 
postcards, print photographs, small flat artifacts like medals and 
    Other scanners can be a holograph, X-ray machine, sonograph, 
laser, to name only a few. The target has to come to the machine and 
be placed in or on it to get its image. 
    Be sure to capture the picture as a JPEG/JPG file, not something 
else. If this is not among the choices in the scanning process, surely 
BMP is. That's the one to go with. 
Borrowed pictures 
    These are pictures already in computer form that you extract from 
their source. Taking a picture from a digital source is quick and 
simple. If the picture comes on a CD, DVD, or other digital medium, 
copy it to your computer. You may do a copy/paste or drag/drop action. 
    If the picture comes from a webpage or email, right-click INSIDE 
this picture and pick 'save picture as ...' or 'save image as ...'. A 
file handling panel opens in which you shayshay to your target disc 
and enter a filename.
Captured pictures 
    In some cases the picture displayed on screen is embedded in the 
webpage in a way that prevents separating it out for saving. In other 
cases, you may produce a display from a computer program and want to 
keep the display as is from the screen. 
    Grab the scene by pecking 'PrtScr'. This captures the entire 
computer screen into the Windows clipboard. To realize the image, open 
your picture editor, and do 'Edit/paste'. The screen comes up within 
the document panel of the editor. 
    Many astronomy programs have a 'save' option in its menus. The 
program instructions explain what this really means. In some cases it 
means to save the configuration settings as a default for future runs. 
Nothing is saved from the screen into a picture file. 
    In some cases only the steps that produced the picture are saved. 
Play them back later to recreate that scene. You have to study the 
instructions and play with the program to understand what's going on. 
    Other programs do have a real capture function for the screen 
display with all its colors and detail. 
    In the absence of a proper screen capture within the program, peck 
'PrtScr' and realize the image in your picture editor. 
    I make extensive use of 'PrtScr'. It is a powerful means of 
building slides that are, uh, fabulous, so say my audiences. 
    One point to mind is that when you run a DOS program under 
Windows, the 'PrtScr' does not work properly. It may be turned off or 
it may try to, well, print the screen on an attached printer. With no 
printer or one shut off, you can hang up the computer and force a 
three-fingered salute. 
    Remember that 'PrtScr' can hold only ONE image at a time. You MUST 
move it to the picture editor and save it, before cutting the next 
image. There are applications that allow capture of many pictures into 
a buffer. You retrieve the pictures later in any order you want.
Saving and naming 
    To save a picture with the programs own saving function, do 'save 
as ...' and NOT 'save'. 'Save' keeps what ever name the picture had 
before, which you may not know or you forgot. You may have a hassle 
finding the file later without knowing its name. Worse, 'Save' will 
without any warning overwrite a existing file of the same name. You 
could without knowing it destroy a good file, now forever gone. 
    'Save as' presents a file handling panel in which you see the 
proposed file name and lets you key in your own filename. Name the 
picture in some manner to later easily find it. In general, do NOT 
save it under the proposed name and directory. 
    The original pictures will have pretty flaky names. When saved 
that way they are scattered all over your computer and are tough to 
collect later. Purposely enter your own name. 
     I name my pictures after the show and a sequence number, like 
'alcon01', 'alcon02', 'alcon03', and so on. The sequence is that of 
acquiring the pictures. You'll shuffle the images into a presentation 
sequence later. 
    Use TWO digits for the number because you WILL collect in your 
preparations of a show more than ten pictures. Two digits allows up to 
100 pictures as your fount for the show. If you happen to run over 
that, as I did for AlCon's Coney Island show, continue with hex 
notation: 'A0, A1, ..., A9, B0, B1, ...'. That's a LOT of pictures to 
choose from for a thirty-slide presentation! 
    Pictures you come onto will prevalently be in JPH form, but BMP 
and GIf are common. All three can be used as is in the slideshow 
program. Be careful to leave the filetype alone when saving. It's in a 
separate input box near the one for the filenmae. As long as it's one 
of the three JPG, GIF, BMP, you're set. 
    Renaming the pictures makes them all gather together in one zone 
in the file listing of your target disc. You may make a new directory 
with a germane name to save the pictures into. My pictures for the 
2009 Astronomical League convention were held in directory 'alcon09'. 
    Chemofilm has a thin layer of chemical made of microscopic grains. 
The blending of these grains to the bare sight makes up the complete 
picture. The grains are randomly dispersed in the film and are 
impossible to reference or modify individually. 
    A digital picture also has microscopic grains, called picture 
elements or pixels. They are arrayed in a grid like tiles. They, 
unlike film grains, can be addressed individually for manipulation by 
the picture editor. Each pixel has an X-Y coordinate, like on a graph, 
by which the editor knows which is which. 
    When light impinges on a pixel in creating the picture, the pixel 
acquires a value or count. This corresponds to the transparency or 
density of a grain in chemofilm. Most digital pictures work with a 
range of value from 0 to 255. O is darkest; 255, lightest 
    Actually each pixel has FOUR values, one for white, red, green, 
and blue. The mix of these values makes the pixel show the correct 
color and luminance in the scene. Besides showing the image on screen, 
the picture editor can display the values for any pixel by setting the 
cursor on it or keying in its coordinate. This information is very 
useful when manipulating the image and is a faculty entirely wanting 
in film pictures. 
    Because of the grid arrangement of the pixels, a picture is often 
dimension by the number of X and Y pixels, like '640 x 480'. This 
menas there are 640 pixels on the X-axis and 480 on the Y-axis. 
Image manipulation
    Unlike chemophotography, it is easy to manipulate a digital 
picture. You need an image or picture editor. Paint comes with Windows 
but you may want something more full-featured. Photoshop or Photoshop 
Elements are the top dogs in picture editing. There are many other 
good editors. 
    I personally use Paint Shop Pro, a commercial program with lots of 
features, all simple to get at and use. GIMP is a new other favorite 
one and it's free for download. Being more complex, it is harder to 
    You are free to modify your pictures to suit your presentation. 
When modifying a borrowed picture, note that it is adapted from its 
original source'. 
    Examples of manipulation are:
    * altering overall brightness 
    * altering overall contrast 
    * altering color balance
    * negating colors 
    * altering highlights 
    * erasing sections 
    * removing blemishes 
    * erasing sections 
    * adding text 
    * combining pictures
    * converting picture formats 
    Before working on your slideshow pictures familiarize yourself 
with the picture editor's features and operations. Experiment with 
scrap picture. Give yourself plenty of exercise with the program. One 
evening isn't enough for a program newly unpacked.. 
    Look for and learn to use the 'Undo' feature! This undoes the last 
operation and restores the picture to its previous state. Many editors 
can undo only the very last operation, so you MUST pay attention to 
your work to avoid horrible irrecoverable mistakes. 
    It is well at the start to work on a COPY of the original picture. 
If things go too wrong, junk the picture and cut a fresh copy. 
    Make intermediate saves. That way you don't have to reconstruct 
all the previous steps if you have to junk the picture. Pull back the 
last saved one and continue from it. 
Altering overall brightness 
    The original picture, such as one taken at night with your camera, 
may be too dark. The picture editor has tools to lighten (or darken) 
the image. All parts are changed by adding a certain count of 
brightness steps to each pixel in the scene. 
    There's a limit to how bright or dark to make the picture. When 
the pixels start to saturate, reach their upper or lower limit of 
count they stop brightening or darkening. Further effort to apply 
light/dark distorts the brightness regime of the picture. 
    A few editors may add this count in a proportional manner to 
prevent saturating pixels already at a high count. Reverse thinking 
for darkening a picture to prevent saturating near value 0.. 
    Too much brightening can also veil details in the brighter areas. 
Too much darkening conceals details in the shaded areas. 
    In general apply bright/dark to highlight the important parts of 
the picture. 
Altering overall contrast
    An editor has many ways to change contrast, some with strange 
names and concepts. Here I explain the usual sense of contrast, what 
happens when you turn the contrast knob on your [old] picture-tube 
television or computer monitor. The scene details are muted or 
exaggerated and shadings are accentuated. 
    Extreme high contrast makes the scene black or white all over. Too 
low contrast gives an overall gray cast. 
    Some where in between you may capture all the texture in the scene 
with a pleasing range of dark and light shades. 
Altering color balance
    For graphical images, illustrations, cartoons, graphs and plots, 
charts, you better leave the colors alone. For photographs the color 
rendition can be badly skewed by the ambient lighting to yield an ugly 
picture. You can to some extent correct this imbalance of color by 
applying more or less of the three primary colors to the image. 
    Programs differ on the means of doing this. They in general tell 
you what portion of red, green, and blue is in the picture and you 
change this mix. The program may use the subtractive colors of cyan, 
yellow, and magenta, but the concept is the same. 
    As a first cut, note the color that's in excess, like red for a 
picture taken under incandescent lighting. Reduce the portion of red 
(or increase that of cyan) and assess the result. Here's a guide to 
the relation of the primary colors to help select the ones to play 
                               /   \ 
          (minus green) magenta     yellow (minus blue) 
                              |     | 
                           blue     green 
                               \   / 
                             (minus red) 
    Each color is the blend of its two adjacents and is the negative 
of its opposite. To increase one, you may decrease its opposite or 
increase its adjacents. 
    A more complete chart includes a radial component for brightness, 
from black in the center to white around the edges. 
    Just how much fiddling with colors you do is pura mente a matter 
of personal taste. It also depends on your acuity of color perception, 
which tends to weaken with age. If you're squeamish about messing 
around with the colors in your picture, it's better to leave them 
alone. Have the 'Undo' button handy. 
Negating colors
    This a very welcome feature of my slideshows. Time and again I and 
others are annoyed by the blast of white space on the projection 
screen in a darkened room. The picture a white page with black or 
colored lettering, like charts, diagrams, graphs, text. Many of us 
find it hard to read the lettering against such a harsh background. 
    A scene with dark background and light lettering is vastly easier 
to read and is orders more comfortable to view in the dark. For 
graphics, charts, plots, other line work, I routinely negate the 
colors before saving the picture. 
    The dark lines and letters are now white (or light color) and the 
field is black (or dark color). For such pictures the exact colors 
often don't matter. They were arbitrarily chosen for the original with 
no peculiar meaning. 
    There may be a caption that refers to the original colors. 'the 
red curve is ...'. You have to remove this caption with the erase 
feature, explained later. 
    I use negative colors for starcharts, too, if the original has 
black stars on white field. Apart from the ease and comfort factor, 
the scene looks more real compared to the sky. 
    The picture editor has a feature for 'negative' ,'inverse', 
'reverse', 'complementary' colors. It takes the count of each pixel in 
the four colors and subtracts it from the maximum value of 255. A 
pixel with count 25, a darkish one, becomes one of 230, a bright one. 
A pixel of count 240, a bright one, becomes one of value 16, dark. 
Altering highlights 
    This is a tricky subject but it's like applying contrast to just 
the bright, dark, or intermediate areas. This is usually done by 
specifying the ratio of each segment in turn. 
    There seems to be no common method across programs for what the 
numbers mean. You got a lot of playing around to do. The idea is to 
judge that certain parts of the picture are good while others need 
enhancing. You then apply highlight to those parts as part of a high, 
middle or low lighted zone. 
    The trick is that if you enhance one feature in the scene, you 
also enhance other features within the same lighting category, how 
ever the program defines that. It may not matter or it can upset 
previous alterations you did. 
    A curious feature of highlight is that some program do not act in 
a linear manner with the numbers. If you alter one zone, its new base 
value may also be changed, so you can not obviously backtrack to the 
previous state by adjusting the numbers manually. You better know how 
to pull the 'Undo' cord.
Extracting sections
    This takes a delineated section of one picture and keeps just it 
as a new picture. Do this when there is a particular part of the 
picture you need in your show without distractions from unwanted 
    One major application is to trim a screen-capture image. The 
picture has the Windows dressing around the edges and all you really 
want is the scene inside one of the panels. 
    This is a two-step process. First delineate the desired section 
with the 'Box' feature. This turns the cursor into a rubber band that 
when dragged over the picture ropes in a rectangular section. The 
usual instruction is to start at the upper left or lower right corner 
of the desired section and sweep to the opposite corner. 
    When the mouse is released a marquee, a line with chaser lights 
running around like on a theater sign, is left behind. If you continue 
the extraction procedure, the area inside this marquee will be 
captured into a new image. 
    You have the chance to back out, like with a right click or the 
'Escape/cancel' button, and try again. When satisfied you got the 
correct selection, invoke the capture. Do study the program's 
    The selection will appear in a new picture panel, ready for you to 
continue working on it. It's wise to first save this picture in case 
you goof up and need to start again. You fetch a copy of this new 
picture and not go thru the extraction steps all over again. Save 
within the naming system of your other pictures. 
    Your program may have other selection shapes, like a circle or a 
lasso. These I find poor methods for making slides, which must be 
rectangular in shape. On the other hand, a circle could be useful to 
extract a section that is then pasted into a 2nd picture. See the 
section on combining picture later. 
Erasing sections 
    Erasing in digital image manipulation really means overwriting a 
section, like painting over a wall. The trick is to choose a color 
that blends with the surrounding area so the work does NOT look like 
you painted over a wall. 
    This method is for small extraneous bits of an image that can 
distract your audience, like a lamp in a shaded area that doesn't mean 
anything for the slideshow. You want to erase the lamp and leave a 
uniform dark area. You may for a graphic want to erase the labels or 
caption to later add in your own. You may have to erase parts of the 
whole picture that protrude into a new selection you extracted. 
    The editor has some way to pick up the color of a point in the 
scene and show that it's picked in a color patch some where in the 
margin of the screen. Look carefully at the area you want to erase. If 
the color around it looks smooth and uniform, your work is simplified. 
use the pickoff feature to grab the color of a point next to but 
outside of the erasing area.
    Then with the eraser, airbrush, mop, spraycan tool, go and 'paint' 
over the erasing area with this color! Be very gentle at the edges of 
the erasing area so the tool strokes don't show. Use short bursts from 
the spraycan, for instance. 
    If the color graduates around the erasing area, you must do the 
erase process in several stages. First erase around the point where 
you picked off the color. When you move to a part where there is a 
shift in color, stop. Pick off a new color from near this next spot 
and continue. The spraycan can help blend the erased portions to make 
a smooth transition around the erasing area. 
Removing blemishes 
    This is a finer version of erasing sections. There may be a couple 
pixels out of order in the picture that should be removed. They could, 
for example, be dirt on the paper you scanned or on the window you had 
to shoot thru with your camera. 
    First pick up the color next to, but not within, the rogue pixels. 
Then use a pencil or pen tool to 'dab' or 'peck' at the pixel. It will 
turn into the new color and blend into its surrounds. 
Adding text 
    Among the best manipulations of a picture is adding titles and 
labels and captions. You may want to name parts of the scene and 
attach a date or location note. You may want to point to certain parts 
and mark certain points. All of this is done thru the editor's 'text' 
and 'draw' features. 
    Choose a simple open typestyle. Fancy, thin, condensed styles are 
tough to read from a distance. My own runaway favorite is 'Comic sans 
serif' that resembles handwritten block lettering and is extra clear 
and legible. 
    I myself stay with horizontal text, not trying aligned or rotated 
text. This leaves the audience upright in its seat. The thing to mind 
is the color of the text on the background it sits on. Some programs 
will automaticly make the text a contrasting color, like the negative 
of the base color, while others use a fixed color that you choose. 
    I and others are routinely frustrated by text, on webpages and 
slideshows, that plain disappears over some parts of the background. A 
compromise method is to use 'shadowed' or '3D' text. This is text 
written with a shadow behind each letter or a raised shape with 
shadowed sides. 
    This text is legible over just about all backgrounds, from light 
to dark. I uss it for labeling photos of the Moon, where the text can 
fall on maria and terra alike. For text on a uniform background, like 
the sky in a starchart, I use flat text of a light color. 
    You have the chance to see your text in the scene before dropping 
it into place. Each program has a 'hot spot' where the text will sit 
when let go in the picture. Study the instructions. 
    Pay attention to the size of the text! It has to be legible from 
th audience seat several meters from the projection screen. It can not 
be tiny lettering you can read with your nose against the computer 
screen. it also can not so large it overwhelms the scene like a 
    Size the text by importance and possible obstruction of other 
features of the scene. I use a large size for a title and a smaller 
one for labels within the scene. 
    You probably noticed how on my starcharts the labels don't 
interfere with each other and hardly ever cover important stars? 
That's because I do NOT let the planetarium program insert its own 
labels. Most are ineptly placed and sized. I manually label each and 
every star, cluster, planet in my charts. 
    I label only the items I need, leaving every thing else blank. i 
place the labels so they don't interfere or obscure other parts of the 
chart. If the label is too long for a single row of text, enter it 
piece by piece on separate rows. You do have to gauge the row spacing 
and centering. 
    Use leaders to attach a label to its target. This may be a couple 
dashes, hyphens, like I do for my starcharts. The front and back 
slashes are also good leaders. In some cases it's best to draw a short 
line with the 'line' tool from the target to an empty area and then 
attach the label to it. 
Combining pictures 
    This can be useful when you want to have a small inset within a 
larger picture, like a detail of a starfield to one side of a 
constellation picture. The exact process is unique for each picture 
editor, so studying the instructions and experimenting is a need. 
    Open both the main and inset pictures. Note the shape and 
proportion of the inset picture. Do 'copy' on the inset. 
    Select in the main picture an area, usually in one corner, of the 
desired size and of the same proportion as the inset. This is done 
with the 'Box' feature to enclose the desired area. 
    Now do 'paste'. The program may ask if you want to paste into the 
selected area. The inset is bunged into the main picture within the 
selected area. 
    An inset may also be round, if it was extracted with the 'circle' 
function. The target area to paste this inset into has also to be 
    You may with the 'line' and 'text' features point to the region in 
the main picture covered by the inset with a suitable label. 
    It may be good to outline the inset with a border using a thick 
line with the 'line' tool. Or do a proper 'border' on the inset before 
copying it. 
    Save the picture under a new name, because you may want the 
unaltered main picture for some other purpose later. 
    Usually only one picture fits well onto an other. Trying to make a 
collage can be messy. The standard application is the inset detail for 
a region in the main picture. 
Converting picture formats
    It may be necessary to convert a rogue picture format into one 
that PowerPoint can accept, notably JPG, GIF, and BMP. The easiest way 
to do this is to open the picture in the picture editor and then save 
it into a file of the other format. 
    This assumes you have an editor that accepts many different 
formats. Some take in only a few kinds of picture, leaving you with no 
way to work with the rogue one. 
    With the picture open on screen, do 'File/save as'. In the file 
handling panel that opens, you must change not only the filename to 
your numbering scheme, but also the filetype. This is in a picklist 
near the filename. Select JPEG or JPG. 
Assembling the show 
    Having acquired, manipulated, saved all the pictures you may need 
for your show, you must now arrange them in the presentation order. 
One way is to print the pictures one by one and then write on each its 
filename. This last step is vital because many programs print pictures 
without their filename. With no name right on the picture you will 
never be sure which picture you're holding in your hand during the 
sorting process. 
    To save paper you may print two or four pictures per sheet. More 
than four pictures are too small to see well what they are. Label and 
cut out the pictures. 
    With the pictures properly labeled, shuffle them into order. The 
order WILL NOT be the same as the acquisition sequence. When you 
actually build the show you must pull up the pictures in the 
PRESENTATION order by calling for them by their ACQUISITION number. 
Got that straight?
    Recite the show while looking at each picture. Is this picture 
really needed? Is its features already part of an other picture? Is 
there something missing that needs a new picture? Is the text clearly 
legible at arm's length (to simulate a back-row seat)? 
    Try not to duplicate scenes. One or two of a given scene is 
plenty. Each picture should have its own internal value to support the 
show, not just to give more examples of the same point. 
    Just do NOT throw up pictures for the hell of it. Maintain a flow 
of thought or theme so the pictures link together. Think of the awful 
slideshws you saw before. Why were they so terrible? Then avoid those 
features in your show. 
    In this winnowing process you'll set aside many of the pictures 
you gathered. You may even set aside some you manipulated in the 
picture editor. Keep these for possible future shows or to customize a 
show for other audiences. Leave them in the show's directory. 
Fire up PowerPoint
    I use PowerPoint, as does virtually every one else. First thing I 
do is choose a background for my slides. I find that a plain one-color 
field is best. I do not use a wallpaper background or one with a 
design on it. After picking a soothing color, I tell PP (short for MS 
PowerPoint) to keep this background for all the slides in this show. 
    I make my first slide by doing 'Insert/new slide/insert (again)/ 
picture/from file'. I shayshay to the show directory where I stored my 
pictures and scroll to the first one in the presentation order. 
    This is the first one in my stack of printouts. from the hand 
written label on that picture I know which of the files to call up. 
Let's say this is alcon07.jpg. It's the 7th picture I acquired but the 
first in the show. 
    Alcon07.jpg is bunged into the background on the slide panel. To 
the left of this panel is a list showing slide #1 in progress. As each 
new slide is built it's added to this list. You can view any slide by 
clicking it on this list. 
    In general the picture will be way off sized to fill the whole 
panel. It has handles around it by which to pull and drag it into the 
largest size that fits within the panel. I like to fill the panel and 
leave a thin border of background around the slide. Gauge the margins 
top/bottom, left/right. The top and bottom may be unequal but the left 
and right should be the same. 
    When satisfied with the arrangement, I move the cursor off of the 
panel and do 'Insert/new slide/insert/picture/from file' for slide #2. 
I repeat the fetching, sizing, aligning process all over again for 
slide #2. This slide is also placed into the list on the left. 
    I work thru all of the slides to complete the show. Along the way 
I save the show, in case of computer or power glitch, under the name 
of the presentation, like 'alcon.ppt'. If I have to give the show to 
the host to play thru his computer I name it 'pazmino.ppt'. That makes 
it easy for the host to fetch when it's my turn to speak. 
    Having done all of the slides and packaged the show, I switch to 
'View/slide show' and try it out. I usually find that a slide is out 
of place or I forget to put one in.
    I switch to 'View/slide sorter'. This lays out the slides like the 
chemo ones on a backlighted table. By drag and drop I rearrange the 
slides into proper order. Where a slide is missing I note between 
which two it belongs. In the 'View/Normal' mode, where the slide show 
is compiled, I scroll to the place to insert the missing slide and do 
'Insert/...'. The new slide is inserted between the others. 
Extra functions 
    PowerPoint has a wide selection of slide transition. This is the 
way one slide changes to the next. I so far haven't used anything 
fancy. I stay with the click! of the old slide projector. The 
transitions can add interest but please don't make a show just for 
    PowerPoint allows adding video and audio to the slideshow. These 
are treated like any other slide, except that its content is sound or 
movie. I haven't needed this facility yet. 
    You can also make evolving slides where its text comes up bit by 
bit with each advance to the next slide. This is done by making the 
slide with the first bit of text. Pick THIS SLIDE as the next new 
slide and add the next bit of text. Repeat until all the text is 
displayed. You really have several slides but they are in register 
except for the new lettering on each successive one. It looks like the 
one slide magicly adds text as you speak. 
Modifying existing shows
    Occasionally you'll find a PPT file ready to show as is. If the 
show is a good one, you may show it to your audience, just like you 
show paper albums, posters, films which obviously you didn't make 
yourself. The title or closing slide usually gives the attribution. 
    However, as in my case for both epsilon Aurigae and LCROSS shows 
at the NYSkies Seminars in summer 2009, the original slideshow was too 
shallow for our astronomers. I modified them by adding slides from 
other sources and omitting some of the original ones. I noted in the 
title slide that this show is adapted for NYSkies. 
    Open the existing PPT file and then work with it just like for a 
new one. If you do this, be SURE to add text to the attribution slide 
that this peculiar show is adapted for your talk. This is essential if 
your show is preserved in the meeting procedings. 
Testing the show
    It may take a couple iterations to get the show into final form. 
One crucial thing to mind well is that the show has to fit within the 
time slot for your talk. If this is 20 minutes, you have to show and 
narrate your slides within 20 minutes and no longer. Have a clock in 
front of you to mind the time. A sports watch is good because you can 
zero it at the start of your talk. 
    Recite the chow, aloud if you must, at a slow and steady pace. 
Don't rush. Don't mumble. Say each word clearly and audibly. As you 
flip to each slide state what is shows and point out its features. 
    You save lots of time by leaving out noise words like 'Here is a 
slide of ...', 'The next picture is of ...', 'I took this picture to 
show ...' . Just state the substance of the picture and you'll be 
amazed how easy it is to keep within your time allotment. 
    If you interrupt the show and have to resume, start the slideshow 
again. Right-click in the first slide. On the popup menu pick 'go' or 
'go to slide' and then scroll to the slide where you left off. This 
resumes the show from that point. You do not have to go thru the show 
all over again from the beginning. 
    Save the final show on your computer and on the medium needed for 
the presentation. This is typicly a storage card, stick, CD. Label the 
medium with your name and meeting so the host returns the right one. 
    That's all there is to it!
Working the computer
    I offer assorted tips and hints for giving your slideshow at the 
presentation session. Here are several relating to the computer. In 
the next section are some for the delivery process. 
    If you have your own laptop with the show loaded on it, you must 
know how to work it in the dark. Laptop keys can be hard to read in 
the dark. Place bits of masking tape on the critical keys. Mark the 
alt/F4 keys to close PowerPoint and then your computer after your 
talk. The light colored tape stands out in the dark and its texture 
gives tactile clues to press the right keys. 
    Have with you the video cable to attach your laptop to the host's 
projector. The host should have this, but it can go missing or, yes, 
the previous speaker took it away by mistake. You also need the power 
brick, specific for your laptop, to prevent low-battery problems 
during your show. You will also need it for using the machine else 
when nd where during the meeting. 
    Know how to turn on the video socket for an external display. Some 
computers always echo the screen to the video output socket. Others 
require some queer key combo to turn on the socket. The host's 
projector NEEDS the signal from your computer to project your show. 
Because you may not have used this feature before, you have to study 
the computer manual. 
    If possible sit down next to your computer to minimize blocking 
the projection screen from the audience. If you have to stand or 
there's an obvious zone of blockage, advise the audience about it. 
Offer that it can shift seat for a clear view. 
    You may attach a remote control for the computer, using an 
infrared connection. Be sure this works by actual test and keep a 
clear sightline from the wand to the sensor on the computer. This is 
one way to let you walk around by the projection screen and still 
operate the laptop by yourself. 
    Do NOT count on a wireless Internet connection during your talk. 
In all places I went to, the signal strength wavered all day with 
frequent dropouts, languid speed, and dead spots. To show what a 
webpage looks like, make a slide of it from a PrtScr capture. The 
image is a static one, but that's better than getting tripped by a 
lazy signal or slow service during your talk. 
Giving the show 
    Inspect the floor for wires, then avoid that area to the max 
during your talk. Stepping on wires can unplug equipment, sometimes 
not noticed until they are next needed. Tripping on wires can injure 
you in a fall. The host should try to gather the wires into a side 
space, cover them with hunks of rug, or station an agent to deflect 
people away. 
    Put any glass of water, a common courtesy for speakers, away from 
the computer and projector. You do not want to spill water on them. 
One trick is to take a drink before the meeting and leave the rest for 
after the talk. 
    If you prefer standing by the projection screen, away from your 
computer, ask the host for an agent to run the computer. The taped 
keys will make his life a whole lot easier when faced with an 
unfamiliar keyboard. 
    When speaking, look at the audience, not the computer. Speak 
slowly and carefully because the audience in the dark no longer has 
visual clues to your words. 
    Where spelling is important, say the letters with the phonetic 
alphabet. The universal standard is the NATO system, but the ham radio 
system is still common in the US. You may use any unique distinct 
words that clue the audience to the initial letter. Make sure the 
words are indeed unmistakable. 
    do NOT fiddle with paper notes! You will mix up the sheets, drop 
them. They rattle and crinkle in the microphone.You look down at them, 
not at the audience, they may be hard to read in the dark. By testing 
your show before your talk, you know the sequence and content of your 
slides. The image itself is the clue to your narration.
    Electronics are wonderfully, when they in fact work. It can happen 
that your computer, the host's machine, the projector, cables, power 
cords, fail. You slideshow is killed, along with perhaps many others.
    There is an insurance policy you can take out. After you arrange 
your pictures in the order for the show, get a printout of them on 
viewgraph sheets. These are clear plastic sheets that go thru the 
printer like paper and take up the picture as a see-thru image.
    The sheets MUST be compatible with your printer to prevent 
kaboshing it with melted or shredded plastic. Read the package label 
carefully before buying the sheets. 
    Stack the sheets in the show order, with blank paper sheets in 
between. You may use the preliminary printouts of the slides so you 
picture on paper clues you to the next image in your show. Put the 
stack in an envelope or folder with strong bands to prevent a 
disastrous spill. 
    Ask the host to have at ready a viewgraph project, also called an 
overhead projector. If the electronic gear konks out, have the 
overhead machine rolled out for you. 
    You give the slideshow by placing the see-thru pictures on the 
window, like a photocopier, right side up and top toward the back of 
the window. An arrangement of lamps, mirrors, lenses projects the 
picture onto the screen. 
    The set of pictures, in presentation order, sits on one side and 
the spent pictures go in a pile on the other. Your narration has to 
louder and clearer to hear above the fan noise in the projector. You 
must also stand to one side to avoid blocking the beam from the 
    The viewgraphs will be of lower quality than the digital slides 
and may be only in gray-scale, depending on the printer. In a 
contingency they'll save your show from being called off. 
Laser pointers 
    Please use a GREEN pointer. A red one often is too weak. Its dot 
gets lost in a busy scene. It is further more surprising how many 
people's eyesight is only weakly responsive to red! To them red is 
perceived as a dim dark tint. 
    Laser pointers come in several colors, but so far red and green 
are far and away the most easily available, Go for the green, even if 
it costs a little more. 
    Be EXTREMELY CAREFUL with your pointer! 
    NEVER aim the beam at or near other people or into a space 
occupied by people. 
    NEVER sweep the beam into the audience by accidently holding the 
trigger between slides. LET GO OF THE TRIGGER instantly the laser is 
taken off of the projection screen. This is a real problem in meeting 
halls with mirrors or other shiny surfaces and fixtures. 
    NEVER horseplay with a laser to play tag or sci-fi warrior. 
    NEVER attract a person's attention by 'dotting' him. 
    NEVER leave your pointer loose where innocent people can play with 
it, specially children. When not in use, keep the pointer out of 
    NEVER experiment with the pointer from your hotel room or open 
field to determine its range. From safely-conducted tests, the 
ordinary green laser pointer sends back a visible reflection off of 
stone or brick out to about TEN KILOMETERS away. The beam is still 
easily noticed after a twenty kilometer round trip and absorption by a 
dull wall. Now that you know, there's no need to experiment. 
    Let only competent persons borrow your pointer and then only under 
your immediate supervision. You really don't want liability by 
reckless application of your pointer behind your back. 
    A good strategy is to treat the laser pointer like a firearm and 
apply its safety principles. In fact, an ordinary commercial green 
laser pointer IS a weapon that is used in crimes. Apart from the 
headlines of firing at aircraft, the pointers are used to dazzle or 
distract sports players, vehicle drivers, farm and zoo animals, kids 
and gang members, neighbors, and police in chase. Being caught 
misusing a laser pointer can earn you deep time, fines, civil 
penalties, and professional and public disgrace. 
    Presenting slideshows was always a part of an astronomer's skills. 
From chemophotography the method is by the 20-thous just about 
completely shifted to digital imaging. Apart from the form of the 
prime images now being on silicon rather than film, there are now many 
more ways to obtain the prime images. 
    Once having these pictures, you may manipulate them in useful ways 
with ordinary picture editors. They allow for extensive customization 
of the pictures to accommodate your audience. 
    Assembling the slideshow is done on computer with PowerPoint or a 
workalike, taking about as much time as it did to assemble a film-
based slideshow. Once compiled, the show is saved to digital medium to 
bring to the presentation host.