Telescope Reviews: EdgeHD White Paper, A Must Read.

And a followup to my note.

The reason I felt so compelled to comment on this is because I believe Celestron took a bold step in presenting this information.

I believe that manufacturers have been hesitent to provide spots in the past because people with no experinece with them might infer something negative about how a telescope could perform based on the fact that perhaps not all spots would fall into the circle represented by the Airy Disk (and I am not speaking here about the poster of the note I responded to, becuase this was not really intended for him, but rather for people that do not have much experience with spot diagrams).

Now that Celestron has published spots for these instruments, we the consumers should do our due dilligence to study how spots are generated and distributed so that we can better assess the meanings.

Not picking on the poster. What he said is 100% correct. My intention was solely to say only what I said... That the spots in this case might suggest to someone that did not know how spot diagrams work that the other SCTs would somehow be inferrior to the C9, and that really isn't the case because as Celestron says, the instrument was still diffraction limited even in blue light.

We should all applause Celestron and demand this data from other manufacturers, but we should also do our own due dilligance to make sure that we know how to use this data properly.

I would be very sad that someone would think that the EdgeHD 8" or any of the other EdgeHD scopes that don't put all of the dots of one color into a circle represented by the size of the Airy Disk and it resulted in their feeling that the EdgeHD scopes are in some way inferrior to other types.

And that is why I think manufacturers don't want to publish spots.

And my guess is that the on axis spots from any number of ED refractors would look scary as compared to these...

The book "Telescope Optics," (a book that I can't praise highly enough) spends several pages discussing how spot diagrams are produced (there is actually a lot to it) and the effect that the number of spots can have on how the distrubution looks.

Our own web sites and media (astronomy magazines and such) tend to ignore this kind of important info but to really get the best use from spots, it is important to study the topic a bit to get a decent understanding of how to read them.

And finally, one more time to say that the person I responded to was 100% correct. The C9.25 shows the best spots.

But the varience between it and the other scopes (at the center of the field) is so small as to be totally meaningless in terms of performance differences. And that was my point. You can't just "look" at the dots. You have to know the distribution to see if enough dots fall outside of the circle to make a meaningful difference. And the fact that Celestron said it was still diffraction limited suggests that it was a tiny fraction of all of the dots that were plotted.