Why Has It Been So Quiet Here This Weekend?



The sky is blue (and black at night). It has been in the 60s and 70s during the day. I've been lured away from the computer by the beauty of a spring day. Sorry!



This evening I set up to do some astrophotography. (The last roll of film I had Wal-Mart develop was a bit disappointing--I thought I had ASA 100 speed film in the camera, not ASA 800, and everything came out severely overexposed.)



While setting up to do some Moon shots, I decided to see how stable the atmosphere was. As you know, I have been testing an Aries Chromacor and a Baader Planetarium Fringe Killer as solutions to the chromatic aberration problem on my Photon Instruments 127mm refractor. The results for the Chromacor have met my wildest expectations. This evening, the 4mm orthoscopic (287x) was still crisp on the Moon, so I put in a 9mm Orion orthoscopic with a 3x Televue Barlow (382x). Still crisp.



The next step up was a 7mm University Optics orthoscopic (just got it) with the Barlow (492x). The image was no longer crisp, but it wasn't bad, either. Some of the shadows that should be completely black were a very, very dark purple instead (the Chromacor is amazing in what it does, but it won't make an achromat into a true apochromat). The sensation of being less than 500 miles above the surface of the Moon was really quite overpowering.



The last step was the 6mm Celestron orthoscopic with the Barlow (573x). I wasn't seeing any more detail than I could see with the 7mm and Barlow, but I wasn't seeing any less--it was just a bit less pleasing of a image. Yes, I tried the 5mm University Optics orthoscopic with the Barlow (688x), and at this point, I had gone way off the deep end of too much power. I was definitely seeing less detail than the 6mm and Barlow.



Note: the Moon is one of those objects, perhaps because the contrast is so high, that seems to tolerate what amateurs call "crazy stupid" magnification. Jupiter reached the fuzz limit this evening at 229x--although it was still only about 50 degrees above the horizon (and thus impaired by too much atmosphere in the way), while the Moon was just about straight overhead.



UPDATE: Before you ask if I could see the flag (actually, flags, there were at least five Apollo missions that landed on the Moon), do the math, and you'll see why this isn't going to happen. To be perceived as a disc, an object must be about three minutes of arc. (Those of you with really sharp eyesight may see discs at two minutes of arc.) At 573x, it should be possible to perceive objects on the Moon as non-points if they are 600 meters in diameter or larger. To perceive the remaining equipment up there (which is much larger than the flags), you would need at least 16000x, and extraordinarily steady air here. Even then, you would not be perceiving detail, only blobs.