Posts Made By: Alan French

http://www.npr.org/templates/story/story.php?storyId=111583873&sc=fb&cc=fp

If you've ever been thinking about a nice telescope for a youngster just starting out, check out Jay's PortaBowl at
http://home.comcast.net/~jayscheuerle/PortaBowl.pdf

I saw it at Stellafane and it works very well. I may have to make one even if I can't think of a youngster who needs a scope!

Clear skies, Alan

http://www.cnn.com/2009/TECH/science/09/10/changing.arctic.temps/index.html

http://news.bbc.co.uk/2/hi/europe/8251914.stm

I spent some time over two nights doing some comparisons between the Canon 15x50 and 18x50 IS binoculars. The first night clouds rolled in so I only got a little time with them. Last night stayed nice and clear. At first I envisioned a rather detailed comparison, but decided the main question was whether there was any obvious advantage to the 18x version.

First a few figures on the two...
Weight: 1200g/42.3 ounces (w/out batteries) [the same for both]
True Field: 15x - 4.5 degrees; 18x - 3.7 degrees [Canon figures]
Exit Pupil: 15x - 3.3mm; 18x - 2.8mm
Cost: 15x - $1000; 18x - $1200 (prices vary, but the difference is usually about $200)
Visibility Factor (Bishop): 15x - 750; 18x - 900
Adler's Index: 15x - 106; 18x - 127

The bulk of my comparisons were done from 10:30 to 11:30 PM EDT time on Saturday, September 19. From our semi-rural skies the Milky Way is nicely visible.

The first target I observed on both nights was M31, the Andromeda Galaxy. In both pair the galaxy was very well seen. In the 18x pair its companions, M32 and M110 were more obvious. M32 was more obviously not stellar and M110 appeared brighter at 18x. It wasn't a huge difference, but it was certainly quite obvious.

My second target was M33 in Triangulum. It showed well in both binoculars, but appeared brighter at 18x. Again, it was not a large difference, but there was no question the 18x view was better.

The third target was M27, the Dumbbell. It was easy in both pair, but the apple core shape was slightly more obvious at 18x.

My final target was M57, the Ring Nebula. Both pair clearly showed the Ring was not stellar, but this was easier at 18x.

When I bought a pair of IS binoculars for birding, I picked the 12x version over the 10x version. As long as I had selected the IS option I figured I'd take advantage of it as much as possible without moving up to the much heavier versions. For astronomy I think the same way. I've decided I'd rather have an IS binocular and avoid the complications of needing a mount. If we only had one pair, I'd pick the 18x for their improved reach.

There are certainly considerations beyond how much they will show. The larger field of the 15x pair might be attractive to people just starting to learn the sky, or simply because a wider field is desired. The $200 cost savings can also be a factor.

I think any serious skygazer who has tried and decided they like the IS binoculars would be quite happy with either version. I strongly recommend anyone considering either try at least one version of IS binoculars before buying. While many amateurs really enjoy the IS feature, some people find it disagreeable. Most of the people we have showed it to like it, and several - five I can think of right now - have gone out and bought their own.

Clear skies, Alan

Note: Bishop's Visibility factor is simply the magnification times the aperture (in mm). Adler feels magnification is more important, and his index is magnification times the square root of the aperture (in mm).

http://www.nytimes.com/2009/09/28/opinion/28krugman.html?bl

Flourite before final processing.

Clear skies, Alan

There are idiots of all flavors, liberal, conservative, agnostic, Christian, short, tall, overweight, anorexic, and so on. When you use the label - in any context - it really means you don't give a red rat's ass what anyone of that particular persuasion thinks or believes and you have no intention of paying any heed to anything from that source. In which case, why bother with any type of discussion.

It also implies a black and white view of an often very gray world. In reality people are far, far more complicated than the terms "liberal" or "conservative" imply, but I guess some people don't relish living in a world of complexity.

Clear skies, Alan

http://www.realclimate.org/index.php/archives/2009/11/the-cru-hack/

http://www.nasa.gov/topics/earth/features/20100108_Is_Antarctica_Melting.html