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Planning Imaging Sessions with SkyTools 3

     

The SkyTools approach to planning an imaging session has three main steps:

  1. Select targets that are appropriate for your equipment and observing conditions and add them to an observing list.

  2. Narrow the list down to only those objects best observed on a particular night

  3. 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