Monday, January 31, 2005

7-Jan-2001: Night 21:45-21:50, Home Kitchen

The sky is clear tonight, but there is strong haze. Originally, we planned for a short observation trip but it is cancelled due to the excessive haze. I heard that when transparency is terrible, the seeing could be excellent at the same time. I look out from my Kitchen window, and I see no star with naked eyes. I take my binoculars out and I can see a bright orange star there but no more.

Taking out my Ranger, I want to test the zoom eyepiece in the sharpness department. People said the sharpness drops below 12mm or 10mm. I want to verify it myself. Scanning the sky first reveal many many stars, and it proves to me that the Ranger with 20mm more aperture actually show more, regardless of the night in the High Island Reserviour. It also confirm me that if it's not the dew, the Ranger can actually deliver amazing views under darker skies.

I point my Ranger to the orange star. Strange. I guess my Ranger has pinched optics at first, I also guess that it might be due to the relatively cold weather. The star looks triangular!!! I never noticed that before. My mind is confused and I begin to blame my Ranger again (You know, I'm considering to switch to a Tak FS60C!).

No matter how, I turned my zoom to make it at 8mm, i.e. 60X with the Ranger. Hey! I see two stars!!!! It's not pinched optics, it's excellent resolution!

A familiar view! I saw that in the High Island Reservior!!! It's the Almach, Andromeda Gamma! I can't imagine that the small viewing windows (approximately 10x20 degree at most) can actually show me something!!! Especially in a real urban sky!!! Clear dark sky separate the two stars. The blue star is pinpoint, and the orange star shows it's diffraction pattern nicely, round and clear.

In order to test my zoom, I insert my 5x Powermate to the optical chain. At 100x (24mm), the double split nicely. I dialled all the way to 8mm, refocus. Hey! The stars are separated by a huge gap of absolutely pitch black sky!!! Both stars show diffraction pattern nicely. You know, it's already 300x!!! The little 70mm aperture is showing at more than 100x per inch, I consider myself crazy!!! (Okay, I didn't try to stack my 2x barlows in) Of course, in this setting, the sharpness drops but the image still didn't break down.

I tested my Ranger with the 20mm Tele Vue Plossl as well, the Almach splits clearly during better seeing. Careful observation helps. With the zoom, it also splits at around 18 to 20mm.

I love my Ranger again. I love my zoom as well, it stands up well against the fixed power Tele Vue Plossl.

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