Posts Made By: Paul Kammueller

Cool Floyd -- that should be one incredible sharp scope. Can't wait to hear first light report!

There are times and places when pure simplicity rules and this is one of them. Congrats on a very fine family-oriented scope purchase.

This is one of the reasons I built a 6" f/6 dob -- fits in the trunk of a car, kids can easily reach the eyepiece, and setup takes 2 seconds. 8)

If it's f/10 then the math is easy. The light cone narrows proportionally down the tube so:

The 81.5mm baffle should be 815mm from the focal point, or 185mm from the objective.

The 71.3mm baffle should be 713mm from the focal point, or 287mm from the objective.

The 56.2mm baffle should be 562mm from the focal point, or 438mm from the objective.

At f/10 a 1-cm error in baffle placement will only over/under-cut the light cone by 1mm or 1% of aperture (2% at the halfway mark)

I believe the 'corrected to f/4' statement refers to the astigmatism caused by eyepieces themselves at fast f/ratios. This is utterly independent of coma inherent in parabolic mirrors.

Much of the distortion seen at fast f/ratios is not only the coma from the scope but also due to astigmatism occurring in the eyepieces themselves that have a hard time pulling together light coming from such a wide-angled light cone. f/4 is tough on eyepieces.

Those rushing out to thus buy Televue eyepieces will not get major miracles but may get minor miracles -- the absence of astigmatism at the edge of the field from the eyepieces makes the coma inherent in the scope much more tolerable. When I had an f/4.5 dob and a handful of naglers, I found coma unnoticeable -- of course, I wasn't exactly looking for it either.

This is just one of those "what I've heard" things so take it with a grain of salt, but I heard too somewhere that some of the quality differences actually arise from the quality of the glass, the raw material, available at the point of manufacture.

I'll just ditto what everyone else has said and everyone pretty much will say on down the line, is buy an 8" f/6 dobsonian from Meade, Celestron, Orion or Hardin that's cheap and has enough power to keep you busy for years

I preferred the wedge & fork for an eq mount -- seems to me the GEM undoes much of the portability advantage of the SCT.

1/4 to 1/40 is a pretty big leap.

I'd say the money to get from 1/4 to 1/10 wave is probably money well spent. To go from 1/10 to 1/20 is a somewhat more questionable return for the money vs. the alternative of, say, going a step up in aperture instead, but this is still a difference that experienced observers will discern.

To get from 1/20 wave to 1/40 wave, I would bet you've crossed the point of diminishing returns in terms of overall performance per dollar spent.

No idea is so great that politics can't kill it.

Sounds like Europe's prepared to go it alone if talks fall apart.

This is a shame, given the magnitude of what this can do for humanity.

These threads demonstrate how different everyone is. You can pay a certain amount just for the peace of mind of know what you're getting is the best possible. It's like buying a car -- do you go used with the bargains and risks that entails, or pay through the nose to buy brand new, complete with full warranty?

Rule of thumb: if it was worth it TO YOU, then it was worth it. The intangible and psychological effects of a purchase (satisfaction, buyer's remorse, etc.) depend upon the individual and their priorities and are not to be discounted in such decision-making. This is, fundamentally, an individual thing.

How 'rewarding' the purchase is depends upon both the performance of that being purchased, and the psychological comfort one has with the money spent or allocated. For example, I once had some really nice spendy eyepieces. The views were fabulous, especially the expansive deep-sky views in my 14.5" dob at the time.

But as time wore on and my observing focus changed, I realized I could spend the money better elsewhere in my optical system. It got so all I could think about was how much dough I had tied up in eyepieces vs. the rest of the scope. The purchase, while being very very high quality, was no longer 'rewarding'. So I liquidated and re-tooled.

It all depends not just on individual tastes, but even on experiences. Time changes everything.