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Tutorials on the most common tasks you may perform in Observer Pro.

Finding DSOs to add to your Observing List

Observer Pro provides several tools for finding the objects that you want to observe. Sorting, catalog filters, visibility charts, and reference photos all come together to help you decide how to spend your time at the eyepiece. If you already know the name or catalog number of the object you are interested in, you can swipe down on the Catalogs screen to reveal a search bar. To search by catalog number you only need to enter the number and the relevant objects will show up in the search results.

Five different sorting schemes are provided in the catalog listings and the Favorites list. These are: Name, Magnitude, Time of Transit, Size, and Constellation.

Sort by Name

Sorting a list by name sorts the objects in the list by their catalog numbers. For example, in the Messier List, M 1 would be listed first and M 110 would be listed last. If an object has a common name, that will be displayed in place of the object's catalog number even though it is still placed according to its catalog number. Use the index on the right side of long lists to instantly jump to a specific section of the catalog (the index list is present in all sorting modes if the list has more than 200 entries).

Sort by Magnitude

Objects can also be sorted by their visible magnitude. This is a measure of the total apparent brightness of the object. The brightest objects are listed first in the list. If no magnitude is defined for an object then it is placed at the bottom of the list.

Object magnitudes are always displayed in the catalog lists regardless of sorting mode. It's displayed in the square brackets after the object name (right after the object type abbreviation).

Sort by Transit Time

An object's transit time is the time that the object crosses the local meridian, an imaginary line that runs from due South to due North. This also happens to be the time that the object is highest in the sky and positioned for best viewing. When sorting by transit time, Observer Pro groups objects into one-hour sections starting at noon on the current date and ending at noon the following date. Within each of these sections, objects are sorted by how high in the sky they get. For example, you can tap '10pm' on the index to go to the section of objects that will transit between 10 and 11 pm. Within each 1-hour section objects are sorted by minimum zenith distance so objects that are closest to zenith (overhead) during that time period are listed first.

Sort by Size

Sorting a catalog by object size arranges the objects in order of their maximum dimension in arc-minutes with the largest objects at the top of the list. This is a great tool for finding objects that will fit nicely in your CCD's field of view or your favorite eyepiece.

Sort by Constellation

Sorting by constellation groups objects by the constellation they are located in. The sections are sorted alphabetically by constellation name.

Catalog Filters

In the Settings Screen (accessed by tapping the wrench icon on the Main Menu screen) filters can be applied to the catalog listings. By default, only objects that can get above the horizon at your location are shown. This can be toggled off to see objects that are not visible from any of your observing sites. The other filters let you set a minimum and/or maximum magnitude for objects. For example, if you set the maximum magnitude at 13.0 then only objects with brighter than 13th magnitude will be shown in the catalog listings. These filters do not apply to the Popular list or your Favorites list.

Visibility Charts

The Simplified 24-hour Visibility Charts shown in the catalog listing screens are a great aid to finding the best objects to observe for your location and the date. As you scroll through the lists, it's easy to see which objects are up and which will be highest in the sky. These charts all factor in your Local Horizon if you have provided one. Look for objects with the thickest green visibility windows. See below for more on Interpreting the Visibility Charts.

Reference Photos

While the reference photos don't necessarily reflect what you will see through the eyepiece, they do help to identify prominent features or discover photogenic targets for imaging. A larger version of the reference photo can be viewed by tapping on the object's row to bring up its detail screen.

Adding objects to your Observing List

Objects can be added to your Observing List by tapping on the action button in the top right of the catalog lists and the object detail screens. If you are currently viewing a list screen then you will be able to select multiple objects to add. The same procedure is used to add objects to your Favorites. Objects that are in your observing list, but do not have observations logged, will show a dark green check mark. Once an observation has been logged on an object, the checkmark will display in bright green. This makes it easy to see which objects you have previously observed while scrolling through the catalog listings. Objects that are in your Favorites list are displayed with a yellow star icon.


Logging Observations

Objects do not need to be in your Observing List to log observations on them. You can log observations from any of the catalog screens as well as from the object detail screens. In both cases, observations can be logged by pressing the action button in the top right. If you are currently viewing a list screen, then you will be able to select multiple objects to log. Once an observation has been logged for an object, a bright green checkmark is displayed next to it in the listing screens. The object is also displayed under the date observed in the Observing History screen.

When you log observations, the object name and date observed are sent to a central database. This information is used to generate the Popular list. This is the perfect place to see what others are observing as it's based on actual observations logged by Observer Pro users.


Interpreting the Visibility Charts

At the heart of Observer Pro are its Visibility Charts. They take on many forms, but they all convey the same basic information.

Simplified 24-hour Visibility Chart

Simplified 24-hour Visibility Chart

The Simplified 24-hour Visibility Chart is shown in the object listing screens (such as Catalogs, Favorites, and Observing List). This chart gives you a simple representation of the object's visibility over a 24-hour period that starts at noon on the currently set date and goes to noon the following date.

The primary aim of the Simplified 24-hour Visibility Chart is to get a view of when the object is above your local horizon and when it is positioned for good visibility (more on what is considered 'good' below). The orange part of the chart represents the object while it is visible (above your horizon) and the green section displays the window of good visibility. The thickness of the orange/green visibility band represents the object's zenith distance (how close the object is to straight overhead). This makes it easy to see which objects get high in the sky and which ones only graze above your horizon. The background color of the chart shows the brightness of the sky over the chart's 24-hour period. In all Visibility Charts, a vertical red line represents 'now', your device's set date and time.

Standard 24-hour Visibility Chart

Standard 24-hour Visibility Chart

When an object's row is tapped, the Detail Screen for that object is displayed. This screen gives access to the object's detailed properties, a larger image, and the other, more specific, Visibility Charts.

The Standard 24-hour Visibility Chart shown here corresponds to the Simplified 24-hour Visibility Chart shown above. This chart plots the object's altitude within the current 24-hour period (the start-date and end-date are displayed in the top corners of the chart). This is the solid orange line. Also displayed is the Sun's altitude (yellow dashed line) and the Moon's altitude (gray dashed line). These altitude curves provide a reference for the object's Visibility Curve which is also shown in this chart.

The object's Visibility Curve represents the object's contrast with the background sky. Many complex factors are included in this calculation. An object's contrast (and therefore visibility) can be good either because the sky is dark (night time, no moon) or because the object has an inherently high surface brightness. The thin horizontal green line in this chart shows the contrast threshold that determines whether the object has good visibility or not (Optimum Visibility Threshold). By default the threshold is 10% contrast, but it can be changed in the Settings Screen. If the object's contrast is above this threshold, then its Visibility Curve is drawn in green. This also corresponds to the green part of the Simplified and Standard 24-hour Visibility Charts shown in the catalog listings.

Month and Year Visibility Charts

Month and Year Visibility Charts

The Month and Year Visibility Charts summarize the information contained in the 24-hour Charts into a view of the current month and year. The Month Chart displays the number of hours that the object is above the Optimum Visibility Threshold ('in the green') for each day of the month. The Year Chart shows the average number of hours per day that the object is above the Optimum Visibility Threshold for each month.

The effect of the Moon on the object's visibility is easy to see in the Month Chart. This particular month Full Moon was on the 13th.

Horizon Obstructions in Visibility Charts

All of the Visibility Charts, including the Month and Year Charts, are computed using your Local Horizon (if you have provided one). Below is an example of the Standard 24-hour Visibility Chart for the same object as shown in the above Visibility Charts (which happens to be M27) at an Observing Site that has obstructions (in this case my house and backyard trees).

Standard 24-hour Visibility Chart with obstructions

Sky Map

The Sky Map is accessed by tapping on the object's photo on the Detail Screen. The same color-coding convention used in the Visibility Charts is also used in the Sky Map for the object of interest. The Sky Map shows a wide view of the sky, your Local Horizon, the object's location and current position, and the path that the object will take through your sky.

Sky Map


Measuring, exporting, and importing your Local Horizon.

If your device has a magnetometer, gyroscope, and location services are enabled for Observer Pro, the Observing Site detail screen has an option to measure your horizon. While measuring your horizon, hold your device in a landscape orientation (with home button on the right) and rotate at a slow and steady speed. This allows the compass reading to keep up with your movements. You can always go back over any part of your horizon if the result seems to be off.

If your device does not include a magnetometer or gyroscope, or you already have a measurement of your horizon, you can import a horizon data file into Observer Pro. The file should end with '.hzn' and contain pairs of values separated by a comma (only one pair per line). The first number is a heading value and the second number is the corresponding horizon altitude. Observer Pro will interpolate between the heading values in the data file so you do not need to provide a line for every heading value. To import the file into Observer Pro simply email it to yourself and open it in Mail on your device. The file will have an Observer Pro icon and when tapped iOS will provide the option to open the file in Observer Pro.