Thursday, March 06, 2008

Finding M41 from inside an urban apartment

A few years back, I can spot M41 on better nights from inside my home. So, I tried again for the last couple of days, they're not the absolute best in terms of transparency, but I just keep trying, I rated them as 5-7/10.

My tools include a pair of Pentax 10x50 PCF III, and a pair of Canon 10x30 IS.

Both couldn't detect it.

However, since the target is so close to Sirius, it then becomes a test for the optical quality of both binoculars. The Pentax has a smaller field of view, despite it's also 10x but it got only 5 degrees true field of view, the Canon is noticeably wider.

The Canon is sharp across basically the whole field of view, but the Pentax despite having a smaller field of view, star begins to show coma near the field edge. The Canon wins here.

The Pentax has a bigger exit pupil, but in urban area where you pupils cannot dilate much, the bigger exit pupil does not translate to a brighter image, but I guess the Pentax will show its edge, I mean the bigger objective, in darker locations.

Finally it's the chromatic aberration. The Canon is simply cleaner, the Pentax has noticeable purple fringe around Sirius.

Since I've been using my Pentax for so many years, I can hold it very steadily, and it approaches the Canon with IS engaged. Without IS, the Canon shakes but the Pentax can be held far more steady.

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