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Σ178: Ram’s Eyes Lite? And just a quick slide down the declination axis away!

I’m sure you can star hop  from the well-known Ram’s eyes to what I would call the “Ram’s Eyes Lite”  – but if your scope is on an equatorial mount life is much, much simpler. All you need to do to mine this pair of evenly matched, 8th magnitude gems is take a quick slide down the declination axis.

Why “lite” – well look at how nicely the numbers compare – in bold are the numbers for the Rams Eyes Lite as compared with Mesarthim -γ  Aries -the original Ram’s Eyes .

Ram’s Eyes             vs  Σ178: Ram’s Eyes Lite
RA: 01h 53.5m                               RA: 01:52m
Dec: +19° 18′                                  Dec: +10° 49′
Mag: 4.5, 4.6                                   Mag: 8.22, 8.20
Separation: 7.5″                               Separation 3.4″
PA: 0°                                                 PA: 204°
Distance: 204 LY                             Distance: 413 LY
Spectral Classification: B9, Ap      Spectral Classification: F1V

OK – maybe you have to study the numbers a bit to see the connection. The Lite version, for example, is far, far dimmer – BUT, the stars are nearly identical in brightness, as are the Mesarthim twins – and that’s what makes both pairs into “eyes.”  Separation, I grant you, is quite different. The fainter stars are twice as close.  But don’t be fooled by the PA. It’s hard when looking at nearly identical stars to decide which is the primary. But with a PA of  0° the Ram’s Eyes line up perfectly on a north-south axis. And, with a PA of 204° the Ram’s Eyes Lite  line up pretty much north south also – well, they favor northeast to southwest a bit, but just a bit.


To find Σ178 start by locating the three brightest stars in Aries. (Developed from Starry Nights screenshot.)

But the most useful similarity is in their Right Ascension – notice they are within less than a minute of one another? (Mesarthim – RA: 01h 53.5m      Σ178 -RA: 01:52m) That means that with an equatorial mount you simply lock onto the very easy to locate Ram’s Eyes (Mesarthim) and having enjoyed that view, just slide down the declination axis about 9 degrees and you’ll be on  the Rams Eyes Lite.

Next, head due south from Mesarthim. (Developed from Starry Nights screenshot.)

Now you can do that all by the numbers, or you can do what I did. I used the following image of the star fields for Struve 178 so I knew what to look for – then I just locked my RA once on the Ram’s Eyes and slid south until I spotted this star field – centered the double, and started cranking up the power. And if you’re star hopping? I suggest you make sure you know the size of your finder’s field – it takes a six degree field to capture the three bright stars of Aries in the same view, so that’s one way to estimate your field. Then all you have to do is know which direction in the sky is south and move about 1-2 finder fields from Mesarthim until you encounter 4th magnitude Omicron Piscium. Treat that as a stop sign. With it at the southern edge of your finder you should see something like the  view that follows. (If directions in the sky – not to mention position angle – leave your head spinning, try the tutorial here.)

Look for this distinctive star field where Σ178 is in the middle of one side of the triangle. (Developed from Starry Nights screenshot.)


When you do find it I must admit it was a bit much for my 60mm refractor with seeing below average. In the 8-inch SCT it split easily, but not in a satisfying fashion. Again, the seeing i the culprit. I’m looking forward to revisiting.  I’m sure on a better night it will split easily witht he 60mm, but probably look best in the 80mm, or maybe the 110.

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