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SS Cygni: The Brightest Dwarf Nova

One of the most famous variable stars in the entire sky, and possibly the most observed, is a faint star named SS Cygni. It's an excellent example of a dwarf nova -- a type of star that regularly (every few weeks) brightens almost 50 times in just a few hours. Once it brightens, it remains at peak brightness for a day or so before gradually falling back to its normal faint state.

Normally at a magnitude of around +12, it brightens to about +8 on an irregular schedule (typically once every month or two). Even with significant light pollution, observers with an 8 inch telescope will be able to observe it throughout its variations. Experienced observers, or people with good, dark skies, will probably be able to follow it continuously with a 4 inch telescope. At maximum SS Cygni will be visible even with small binoculars -- it is not far below the naked-eye limit under dark skies when it's at its brightest.

Suggestion: Along with these charts, download AAVSO finder charts for SS Cygni. Although the charts I give are adequate for finding, the AAVSO charts have comparison star magnitudes and a generally lower magnitude limit (around +12.5 in the vicinity of SS Cygni).

AAVSO "b" scale (3° wide; finder or very low power)

AAVSO "d" scale (1° wide; low-to-medium power in small scopes)

Be aware that the AAVSO charts are rotated 180°, so that south is at the top, to match the view in a typical telescope. The finder charts below have north at the top.

The easiest way to find SS Cygni is to start at Rho Cygni, a 4th magnitude star often visible from places with moderate light pollution, particularly when Cygnus is high (late summer and fall evenings are good from the United States and other mid-northern-latitude locations):

Cygnus with Rho Cygni labeled

Once you've found Rho, it's a fairly simple star hop to SS Cygni. There's a very conspicuous pattern of 8th and 9th magnitude stars near Rho that looks a little like an oddly bent hockey stick. You should be able to follow the "stick" in your finder from all but the most light-polluted sites. Even if you can't find it in the finder, if you have a smallish scope, or one with a very wide field of view, you can try following it at low power. I've had little trouble finding it with 55x in a 10" reflector. At the very end of the "blade" of the "hockey stick" is a bright (5th magnitude) star. Once you have that star in your field of view, you'll be able to hop to SS Cygni's home, a triangle of 9th and 10th magnitude stars.

The "Bent Hockey Stick" and SS Cygni's Home

Once you've found the triangle where SS Cygni is, you'll probably want to get out the AAVSO "d" scale chart. The "triangle" has 3 stars (magnitudes 8.5, 9.6, and 9.9) with SS Cygni just inside one of the sides of the triangle. Normally, SS Cygni will be much dimmer than the three "triangle" stars; during a typical minimum it will be closer to the magnitude 11.8 and 12.3 stars inside the triangle. During a maximum it will outshine the corner stars!

Closeup of SS Cygni's Home

So, go outside and find out what SS Cygni is up to tonight!

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