Posts Made By: Steve Lathrop

I can't compare refractors with reflectors, but can add something on the refractor aperture/apo/achro question. At the end of last summer I did a side-by-side with a Stellarvue 80/9D achro and a Televue 102.

First, I was mightily impressed by the Stellarvue, which gave exciting views of the moon, the south polar cap on mars, M27, and the ring nebula. In each case the view through the Televue was noticeably, but not hugely, better. I don't think it would have taken an expert to see the differences, but it might have taken a connoseur to want to pay for them.

However, there was one target, M13, where the difference was large. On a night of above-average seeing under mag 4.5 skies the 80/9D showed the globular as a condensed ball of light with a very few resolved stars at the edges. As usual, the TV-102 resolved stars all the way across the face of the globular. It was a big difference and anybody would have noticed it.

With such small apertures I don't even try faint fuzzies unless I can get to a dark site, but my guess is that the differences I noted in brightness and resolution on M13 would apply as well to almost any galaxy observations done with these scopes.

Hope this helps.

Steve

One great resource is dpreview.com. Maybe the most comprehensive and reliable information on digital cameras. Note that each camera reviewed is accompanied by numerous images which can be downloaded at full resolution and then examined with Photoshop. This gives you the chance to really see what you are going to get.

Canon has announced the upcoming 20D. Take a good look at that one.

Hope this helps.

Steve

I had a wonderful Triumph Trident motorcycle. English measure throughout, except the carbeurators, which were metric. Except certain other parts, (I forget which) which were Whitworth. Three sets of wrenches mandatory. Not great in that respect.

HOWEVER, I remain a fan of English measure for building things. A lot of building is done by dividing stuff in half. Half of 6-7/8 is 3-7/16, instantly. Probably have to calculate it in metric.

Also, tolerance of plus or minus 1/16th is pretty manageable. Plus or minus 1 mm is too fussy, and 2 mm is often too sloppy.

Steve