Fun with Globulars

Given the time of year, one might wonder why a post about globular cluster observing comes now. There are 2 good reasons. First, it's a good time to plan observing projects that start in a few months. Secondly, I've done a bit of research lately on the Terzan globulars. There is confusion in the astronomical community about the identification of some of these objects. I believe I have this sorted now - results available in the Plan Library. But I digress, slightly...

Globular Cluster M 22 - Photo by Mark Lang

Observing globular clusters can be a very interesting pursuit. If you observe carefully, you'll notice that they all appear just a bit different. Not only in size and star colors, but notably in how many stars you can resolve, and the pattern of concentration. You can also observe globulars in neighboring galaxies.

Deep-Sky Planner provides a number of resources to help. You can search various catalogs in the database, and you can download several plans from the Plan Library that contain specialized lists of globular cluster. Current these include:

• Astro League Globular Clusters
• RASC Globular Clusters
• Palomar Globular Clusters
• Terzan Globular Clusters.

The AL and RASC lists are designed to educate the observer about observing globulars. They provide a nice sampling of objects and helpful information in their respective publications*. Either is a worthwhile project.

The latter two lists are designed for imagers and observers with large telescopes. The data for these lists are taken from the SIMBAD astronomical database and are supplemented with magnitude and color information gathered by W.E. Harris of McMasters University in Canada.

These are small, faint clusters so you will likely want to download and view DSS images of these objects. Although these clusters have been studied for many years, magnitude and color information is missing for many of the objects.

*AL Globular program material: https://www.astroleague.org/al/obsclubs/globular/globular1.html

*RASC Globular program material: Edgar, James S. Observer's Handbook 2017, Toronto: Royal Astronomical Society of Canada, 2016, p312. Print.

Deep-Sky Planner 7.1 Release

A free update to Deep-Sky Planner 7 has been released. It contains bug fixes, enhancements and new features. The list of changes is available in the release notes that can be viewed in the Deep-Sky Planner 7 Community (Software Updates page), and in the Readme file that accompanies the update.

This release has some important changes that require some explanation. First, support for ASCOM weather stations has been added. I tested with both the BlueAstro Stickstation and the Astromi.ch MeteoBox. As you may know, the developer of the Stickstation, Per Frejvall, died unexpectedly in July. I had corresponded with Per and worked out communication issues before he passed. I have since worked with Martin Ingold at Astromi.ch on support for MBox. Both Mbox and StickStation are working well with DSP7.1.

MeteoBox (MBox)

Deep-Sky Planner 7 was released with internal support for high resolution displays. The user interface was sufficient where Windows scaling was 150% or less. Because the user interface was not sufficient where scaling was above 150%, I have elected to make internal support for high resolution displays an option within Deep-Sky Planner. I will improve internal support for high-resolution displays as Windows and development tools improve support for high res displays.

Lastly, the database has been updated with new cross reference information for NGC globular clusters. There were incorrect references between NGC and GCL catalogs for globular clusters. If you have created any observing plan documents that include GCL objects, you may want to be sure that the object information is correct. Please look for a new Terzan Clusters plan and an updated Palomar Clusters plan in the Plan Library in a few days. My thanks go to Owen B for reporting this issue.

Generating a Horizon Model for Deep-Sky Planner

A Deep-Sky Planner user has contributed a method for creating a highly accurate horizon model for his suburban imaging location. The location has many obstructions that often interfere with imaging projects. Knightware thanks Deep-Sky Planner user Mark L. for contributing the following method.

At your observing location, set up a camera with a wide angle lens on a tripod.  I used a DSLR and an 18mm lens.  Make sure the date/time is set correctly on the camera.

Level the tripod, then set the altitude of the camera so that the local horizon can be seen in all directions.  This makes the process easier since you don't have to readjust the altitude on each shot.

Determine a proper exposure time.  I used 10 seconds at f/2 and ISO 800 in a fairly light polluted area (NELM 4.8).  I got magnitude 5 and 6 stars with these settings.

Take an exposure, then move the azimuth of the camera about 30 degrees and expose again.  Do this until you have covered the entire horizon around the camera's location.

At your computer, start up your planetarium program setting the date/time to match the photos you just took. I used TheSky6, but other planetarium programs can also be used.

Star information from TheSky6

Examine each photo, looking for a star that can be seen just above key points on your horizon.  Find that star on the planetarium program.  Click on the star to get the azimuth and altitude, then record these values using a plain text editor such as Notepad.

It is important to record the data in azimuth, altitude order with a comma separating the values because this is the format that Deep-Sky Planner expects. TheSky6 produces data in degrees, minutes, seconds format, so I wrote a script that turns the data in the text file into decimal degrees format for Deep-Sky Planner.

Python scripts are available to convert the data taken from TheSky (either TheSky6 or TheSkyX) to Deep-Sky Planner format. You can download these and sample input and output files at http://www.knightware.biz/community/public/dsp6/kb/article-31.htm

Python script that converts data from TheSky 6

Repeat the examination process for as many points as possible around your horizon. The more points you record, the more accurate the model.

Import the list of Az/Alts into Deep-Sky Planner. Open the location in the Location Manager that you want to attach the horizon model to in the Location Editor. Click Import to open the Horizon Model Import dialog box. Choose the Input File that contains your horizon model data, choose Comma Separated Azimuth/Altitude format, and enter a name for the new model. Click Import to pull the horizon into the Deep-Sky Planner database.

Horizon Model Import dialog box

Save the original data file or Export the horizon model to a .horizon data file using the Location Editor in case you need to import the model again in the future.