BRRRR! Cloudy, overcast skies. Sub-freezing temperatures. Snow, sleet, and freezing rain. This is not the stuff that star parties are made of. During winter, many amateur astronomers develop a serious case of eyepiece time deprivation. The more serious amateurs may have access to an observatory, or perhaps they even brave the cold and setup their telescope for a night of eyepiece time. For the more casual observers (like myself), this option seems daunting, and sitting outside shivering at the eyepiece can zap the joy out of even the most enthusiastic stargazer.

If you are the type to brave the winter and set out to stargaze during this season’s star-filled clear nights, I truly admire you. I will also venture out and enjoy the majesty of Orion on the occasional mild winter night, but sadly, my stargazing nights dwindle drastically during the cold months.

What to do? Winter is a great time to catch up on my astronomy reading and TV shows, but what about when I need some actual eyepiece time? Here is what I do when that craving gets unbearable during those long, cold, overcast nights.

Star parties are as much about atmosphere as they are about observing. I turn off the TV, head for the computer room (den), and turn on only one lamp with a red light bulb. (Yes I have that ready just for this purpose. You may laugh now.) I then start up my planetarium software. I use either Hallo Northern Sky or Stellarium, but any planetarium program will work just fine. I set it up for tonight’s sky, about an hour after sunset. Then, I go through the program’s settings to emulate the night sky as closely as possible: I turn off the coordinates grids, and set it up to display stars to about magnitude 7. I usually leave brighter star name labels on, and I set it up to faintly display constellation lines. This helps me find my way around the sky – even the best programs don’t quite simulate the sky well enough to pick out star patterns as easily as in the real night sky. The faint constellation lines also give me the sense of scale that comes naturally when I look at the real sky. Keep the lines faint if your software will allow it – this helps the sky look more real, while giving you the sense of scale that you will need to star hop. Also, zoom in or out so that you see about 50 to 60 degrees of sky.

Once I get my planetarium program set up as realistically as I can, I then turn to my observing list. Just as I do before going to a real star party, I prepare a list of objects to observe tonight. If you do not already have a list prepared, you can use my famous monthly observing lists posted on River Bend Astronomy Club’s website, at this link: http://riverbendastro.org/resources/. Then, just as I do when out under the real sky, I have a list of objects ready to find and observe.

At the beginning of my indoor observing run, I start with Solar System objects (the Moon, planets, and comets). If the Moon is up, I usually observe it first, and practice navigation with the planetarium program. You should be able to navigate either manually or by using a search function. To move around the sky manually (to simulate a Dobsonian, for example), most programs let you click and drag the sky, or simply use the arrow keys on the keyboard. For example, once you find the Moon, use your program’s zoom function to simulate binocular or eyepiece views. Look around the perimeter of the screen for all the observing readouts – you are looking for “field of view” or simply “FOV.” When you zoom in, stop somewhere around a FOV of 6 degrees – this simulates the view through 10×50 binoculars. The Moon and surrounding sky should appear quite like the view through most binoculars.

Now, drop in a virtual low-power eyepiece by zooming in on the Moon until the FOV reads about 1 or 2 degrees. If you know the actual field of view of some of your eyepieces, you can simulate those views by varying the zoom as needed. Stellarium has a cool feature that allows you to overlay the view under a circular matte, which is even better for simulating the view through an eyepiece. Move to a higher-power eyepiece by zooming in until the FOV reads about 0.3 degrees. This will simulate the actual field of view visible in an 8-inch SCT with a 12.4mm Plossl.

Before moving to another object, make this simulation as realistic as you can. Remove the circular matte and zoom back out until your FOV is about 50 degrees. This is about the amount of real sky that you can take in with your eyes. Now, navigate to the constellation that contains the next object you wish to observe, and “star hop” as best you can to the object. Take your time – remember, you are at a star party!

If you have trouble finding a deep-sky object, you can use your software’s search function. This works much like a go-to telescope. If you do not have a go-to telescope when you go to a real star party, this is your chance to “try it out.” Of course, you can opt to star-hop no matter what, if that is what you normally do out under the real sky. The choice is yours!

Once you locate a deep-sky object, zoom in on it to simulate binocular and eyepiece views. Remember to turn on the circular matte view if your software has this option. Your software may or may not actually display an image of the deep-sky object itself, but at the very least should show a marker where the object is located in the sky. You may need to turn this option on, and you may need to tweak it so that deep-sky objects down to a certain magnitude appear. I find that if I adjust it to display deep-sky objects down to about magnitude 10 or 11, most of the objects I set out to find are displayed. You don’t want to adjust this too faint, otherwise the program will display so many objects that your screen will appear cluttered with labels and markers. You may need to play with this setting during your observing run to turn markers on and off as needed.

I have found that both Stellarium and Hallo Northern Sky can display nice images of all the Messier objects. Zooming in on them to simulate an eyepiece view is a real treat, and the programs do quite well to simulate the view through an amateur telescope at a dark site. You will have to go into your program’s setting and turn on “display nebulas” or “display deep-sky objects,” and move the magnitude slider to about the middle position. If a faint object seems to be missing, move the slider a little to the right to display fainter objects. Both programs can also display images of some NGC objects, although usually not near all of them. You may find double stars and open clusters are displayed nicely since they are simply stars, but fainter galaxies and nebulae in the NGC catalog most likely will not have images to display. This is where an actual star party still rules! We have to save some excitement for the real thing, right?

During my indoor star parties, I will usually hunt down about a dozen deep sky objects. I star-hop whenever I can, just to keep my knowledge of the night sky fresh. I also keep my planetarium program following actual time (and date), so I really do have to consider whether or not an object has risen yet or if it has already set. If the object is not up in the sky, I don’t observe it, just as at a real star party!

Sometimes I listen to music during my indoor observing runs. A good pair of studio headphones works well to isolate you from other noise (spouse watching TV, kids, etc.). A cup of hot cocoa also helps to set the mood, especially on very cold nights.

This is the best part: When the indoor star party is over, I exit my planetarium program, turn off the music, take off my headphones, turn off the red light, and I get up and head into the living room. Then I tell my wife, “I am home from the star party!” I get home from my “dark sky site” in 15 seconds flat!

So, next time you are stuck inside on a cold, overcast winter’s night, have yourself an indoor star party and keep those observing skills sharp!

Here are links to both programs mentioned in this article, Hallo Northern Sky and Stellarium. Both programs are free.

Hallo Northern Sky: This program runs fast and even runs great on older PCs. It is also great for creating star charts to print.
http://www.hnsky.org/software.htm

Stellarium: This program gives a very realistic stargazing experience. It is larger than Hallo Northern Sky and requires a somewhat newer computer. It also has a Macintosh version.
http://www.stellarium.org/

Clear Skies,
Bill Breeden

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