suitti (suitti) wrote,

These three things

Tuesday night, three big things happened in astronomy that were very important. Important to me, anyway. First, when i got home from work, there was a package waiting for me. It was my new 2" Q70 eyepiece on sale at Orion. I'd done my homework. My scope has an aperture of 254 mm. My eye's pupil dilates to 6 mm (measured with hex wrenches against Sirius). So the optimal wide field magnification is 254 / 6 = 42x. The focal length of the scope is 1200 mm, so the optimal wide field eyepiece focal length is 1200 / 42 = 28 mm. This is similar to my 25 mm eyepiece, so i could just stick with it. So, i'm done, right? I don't have to buy anything. However, i want a wider field of view. If i have to toss a little light away, that's not a big deal. The Q70 has a 70 degree apparent field of view (AFOV). My 25 mm has a 52 degree AFOV. So that's a 34% bigger field of view (FOV). Then it's 38 mm instead of 25 mm, so that's 52% lower magnification. Combine these: 1.34 * 1.52 = 2 times the FOV. The magnification is 31.6x, and the exit pupil is 8 mm. Well, when i do outreach, some of the kids are bound to have an 8 mm dilated pupil. So while i may only detect 55% of the light, some of these kids will get it all.

The second interesting thing was that, in a break with tradition, it was a clear night. Normally, if you get some new toy in the mail, then the skies are opaque or worse. But the skies were crystal clear.

Third the Ford club had an outreach program. Kids between about 3rd grade and 6th grade (i'm just guessing) got treated to a quick introduction to astronomy, and we showed them a few objects in our telescopes. The flood lights in the parking lot were pretty rude, and i wasn't able to get a good alignment on my scope's computer. I had trouble finding Rigel in my finder scope, due to the glare. But i showed the kids M42 - the Great Orion Nebula. And i showed them M45, the Pleiades star cluster in the new Q70. No, the Q70 does not have enough FOV to show the entire cluster. And, i didn't get a chance to do an A/B comparison with my 25 mm eyepiece. Another night.

It was very cold, and i've no idea if my electric socks were working or not. I'd let my feet get wet, which is always a bad thing to do. Just 12 degrees F, but no wind. All in all, a great event, and lots of fun.
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