Planning
Imaging Sessions with SkyTools 3
The
SkyTools approach to planning an imaging session has three main steps:
-
Select
targets that are appropriate for your equipment and observing
conditions and add them to an observing list.
-
Narrow
the list down to only those objects best observed on a
particular night
-
Once
you choose a target, decide when to start imaging.
Determine the the best order for filters. Etc.
Selecting
Appropriate Targets Ultimately
you want to have an observing list of good targets. If you
have more than one observing project you may want to create a
separate observing list for each. In some cases you may
want more than one list for each project. In that case
create separate observing list groups and place the related
lists within them. Keep in mind this one important rule of
thumb going into planning for a specific night: If you don't
want to observe it, don't put it in the list. In other
words, don't go overboard on the number of objects in your
list. Using
Pre-existing Observing Lists Our
web site offers a wide variety of observing lists for
download. Open the SkyTools Data Manager and select
the Import Shared Data tab. Select the Browse Skyhound
Web Site radio button. Select an appropriate location
to browse, such as Deep Sky observing Lists. To
view the details of a list double-click on it in the
table. When you find one you like select a group for
it and click the Import button. The list will
appear in the Nightly Planner and Real Time tools under the
group you chose to add it to. Copying
Targets from One List to Another You
may want to make your own custom observing list from objects you
find in others. You can copy objects from one list to
another. First open the list with the object you want to
copy. To copy one object right-click on it and select Copy
To... To copy more than one object mark each object
you wish to copy with a red check mark via the check mark
column. Right-click in the check mark column and select Copy
Checked To... Adding
a Target by Designation Suppose
you
see a cool APOD
and decide you want to try to image the same object. Or a
friend suggests a target at a star party. Or you see an
intriguing post on a forum. If you know the designation of
the target use the Designation Search tool on the planner
tool bar. Enter the designation into the Quick Search
field or use the Browse tab to look it up by
catalog. Once you find your object use the area at the
bottom of the diialog to add it to your observing list. Searching
the Database for Targets Open
the Database Power Search tool from the button on the
planner tool bar. This is a powerful tool for searching
the SkyTools databases. Enter your search parameters and
click the Search button. You may copy all or some of the
search results to your observing list. Using
the Nightly Planner Use
the Nightly Planner when you want to plan your imaging session
ahead of time. There will be some cases where you have a
high-priority target, such as a comet or nova, that you want to
get on this night, but in most cases you will have a list of
potential targets from which you want to cull only those best
currently observed. The observing list filters are used to
separate out only those objects, narrowing down your choices for
a particular night. Once you have selected your targets
the planner can help you decide when it is best to image them. Narrowing
Down Your Observing List Open
the Nightly Planner and select Imaging mode.
Select the night, location, telescope, camera, and filter. If
you don't have the observation status and priority columns
displayed for your list use Configure Columns to add
them. Enter a priority level for your objects as
appropriate. Often this means assigning a high or low
priority to only a few objects (leaving the default at neutral
priority for the rest). Clear
the filters by selecting the Reset Filters menu item from
the Observing List menu. Right-click
on the observation status column heading and select Set
all objects to --> not yet observed. Right-click on the observation status column heading
again and clear the check next to Show observed.
The other selections should all be checked. Later, as you observe
each object change the status either to observed or re-observe
by right-clicking in the observation status column. As you mark
targets as observed they will be hidden from view,
further narrowing your list. Now
lets use filters to narrow down our list. Start by specifying a minimum altitude for your objects. I
recommend choosing Above 2X (Airmass) Only or Near
Maximum Altitude. Next specify your sky conditions.
Choose Twilight/Moonlight Ok or Complete Darkness Only
as appropriate. Choose your minimum exposure
quality. I recommend choosing A -- Excellent Only.
You may wish to apply other filters as appropriate. If you
can only observe for a portion of the night grab the red lines
on the extremes of the NightBar. Drag the line on the left
to mark the start of your imaging session. Drag the line
on the right to mark the end. Useful columns to have enabled in your list are: Timeliness
Index (Ti), Start, Duration, Q, Img. Size, and Resolution.
Use Configure Columns to add them if they aren't already
displayed. The Ti column tells us how long the
object is going to be available to observe on subsequent
nights. Ti ranges between 0 and 1. The higher the
value the more timely your observation needs to be. In other
words, a high Ti means to get the object tonight, if possible,
because it is low on the horizon and may not be available the
next time you observe. The optimum sort considers this
value and places the more timely objects higher on the list,
other things being equal. Finally
I recommend checking the
box next to Optimum Sort. This will sort the
list in the best order to observe, taking into account the
altitude of the object, sky conditions, your own priority, and
the observation status of each object. If
you still have a lot of objects displayed you will need to use your own judgment
to pick out the remaining targets you want to go after on this
night, based on the data in the list. Considering
Other Nights in the Coming Weeks/Months In
general you will want to pick the best objects to observe during
your next session from your list, as indicated by the
planner. But sometimes you may want to plan ahead to
determine the best week to observe a specific target. To
do this select your target and open the Exposure Calculator.
Click the Night Back/Ahead button to quickly progress to
the next night. Look at the results under Calculate
SNR for Exposure for each night. How much SNR is
available this night? And the next? It should become
apparent fairly quickly on which nights you want to observe this
object. Over the course of a month the primary variable is
going to be moonlight. Planning
When to Start Your Exposures Start
by highlighting your first target from near the top of the
list. Have a look at the NightBar graphic at the top of
the window. Pay particular attention to the blue
line. This is the relative quality of exposure (Q)
line. Q compares the current conditions to the optimum
conditions for your equipment and location. If near the
top, conditions are optimum, which is generally when you want to
expose. For M79 below the best opportunity is just after
twilight ends. As the target sets lower in the sky the
quality decreases until the moon rises at around midnight.
At that time the moonlight will degrade the image even more. 
The
program automatically chose a window in time during which
it is best to expose on this night, defined by the Start and Duration
columns. Note that the exposure window for M79 is pretty
short in the example--only 105 minutes. The Q column
summarizes the quality of the exposure window in terms of letter
grades, with A meaning excellent. These should all
be grade A because we filtered out all the others. The SNR
column estimates the maximum total Signal to Noise Ratio
available during the exposure window (if you exposed the entire
time). Brighter objects will reach a higher SNR in less
time. In this case of M79 above an SNR of 100 would be
fine, so we have plenty of time, assuming we are not imaging in
multiple filters. The
Img. Size column tells us how many pixels the object will
cover on the image. If too large to fit into one frame this
column lists the minimum number of frames required. The
final step is to refine your plan with the
exposure calculator. Using
the Real Time Tool Use
the Real Time tool when you are already at the telescope and
want to image a target right now. The observing list filters are used to
separate out only those objects best observed right now.
The Optimum Sort puts the best available targets at the
top of the list. Narrowing
Down Your Observing List Open
the Real Time Tool and select Imaging mode.
Select your location, telescope, camera, and filter. If
commanding the telescope, open the connection to the
mount. If
you don't have the observation status and priority columns
displayed for your list use Configure Columns to add
them. Enter a priority level for your objects as
appropriate. Often this means assigning a high or low
priority to only a few objects (leaving the default at neutral
priority for the rest). Clear
the filters by selecting the Reset Filters menu item from
the Observing List menu. Right-click
on the observation status column heading and select Set
all objects to --> not yet observed.
Right-click on the observation status column heading
again and clear the check next to Show observed.
The other selections should all be checked. Later, as you observe
each object change the status either to observed or re-observe
by right-clicking in the observation status column. As you mark
targets as observed they will be hidden from view,
further narrowing your list. Now
lets use filters to narrow down our list.
Start by specifying a minimum altitude for your objects. I
recommend choosing Above 2X (Airmass) Only or Near
Maximum Altitude. Choose your minimum exposure
quality. I recommend choosing A -- Excellent Only.
You may wish to apply other filters as appropriate. Useful columns to have enabled in your list are: Timeliness
Index (Ti), Start, Duration, Q, Img. Size, and Resolution.
Use Configure Columns to add them if they aren't already
displayed. The Ti tells us how long the
object is going to be available to observe on subsequent
nights. Ti ranges between 0 and 1. The higher the
value the more timely your observation needs to be. In other
words, a high Ti means to get the object tonight, if possible,
because it is low on the horizon and may not be available the
next time you observe. The optimum sort considers this
value and places the more timely objects higher on the list,
other things being equal. Finally
I recommend checking the the
box next to Optimum Sort. This will sort the
list with the best current targets at the top, taking into account the
altitude of the object, sky conditions, your own priority, and
the observation status of each object. Picking
a Target Start
by highlighting your first target from near the top of the
list. Have a look at the NightBar graphic at the top of
the window. Pay particular attention to the blue
line. This is the relative quality of exposure (Q)
line. Q compares the current conditions to the optimum
conditions for your equipment and location. If near the
top, conditions are optimum, which is generally when you want to
expose. For the Cigar Galaxy below the best opportunity is
from after
twilight ends until the moon rises just after 2 AM. The
yellow vertical line is the current time (23:56). We only
have about 84 minutes to expose before the moon
rises. 
The
program will automatically choose the current window in time for
your exposure. This period began with the time in the Start
column. The Duration
column tells you have much time is left before the end of the
exposure window (from the current time). The Q column
summarizes the quality of the current exposure window in terms of letter
grades, with A meaning excellent. The SNR
column estimates the maximum total Signal to Noise Ratio
available during the exposure window (if you exposed starting
now for the Duration). Brighter objects will reach a higher SNR in less
time. In this case the maximum SNR is 58, again assuming we
started right now and exposed for the Duration. The
Img. Size column tells us how many pixels the object will
cover on the image. If too large to fit into one frame this
column lists the minimum number of frames required. The
final step is to refine your plan with the
exposure calculator. When started from the Real Time
tool the Exposure Calculator will automatically select the
current window, starting from the current time. Refine
Your Plan with the Exposure Calculator The
Exposure Calculator provides a laboratory within which to
experiment with different start times, exposures, filters, etc.
The data in the observing list summarizes what the Exposure
Calculator can examine in detail. To open the Exposure
Calculator right-click on a target object and select Exposure
Calculator from the menu, or highlight the target and press the
"e" key. The Nightly Planner/Real Time tools helped
you decide which objects to observe and gives you an idea of the
order. The Exposure Calculator will help you finalize the
details of your imaging session for each object. Next
topic: Using
the SkyTools Exposure Calculator
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