... and still the best wife I could wish for!
SkyMonsters - http://www.skymonsters.net
GSO RC8/Takahashi FSQ85ED Canon 450D/QSI583wsg
Takahashi EM-200 GEM/Vixen Super Polaris
Its true - in any hobby - that someone can do things better than you. However, not to do something because you aren't the best would ignore the value and satisfaction of the journey.(TimN)
Quote:Pretty cool paper. And while I'm pretty pleased with my new 11" Edge HD, the one deficiency it has compared to my 11" NexStar GPS is that it doesn't have enough focus range. I only just discovered this a couple of days ago. I just bought a binoviewer and while it works great with my Denkmeier PowerXSwitch and the GPS, I can't reach focus with the reducer on the Edge HD. The mirror doesn't move nearly as far. I realize this is most likely due to the sweet spot for the Edge optics, but it's still disappointing, especially given the incredible results I'm getting with the binoviewer (should have bought one a LONG time ago!) and the NexStar GPS. Beo
Quote:It's a pity they haven't produced a focal reducer for the 800 and 925. Still I don't understand why.
Deep Space Products
Quote:Nice white paper on the EdgeHD design, production etc available for those that are interested. Lots of good info on the Focal reducers too.http://tinyurl.com/c4n69wnunder the more info button. (Celeston Webpage)These are cool/capable scopes.
Quote:For those interested in Roland Cristen's thinking about the Edge and ACF scopes, you can find it here:
"The heavens declare the glory of God; the skies proclaim the work of his hands." Psalms 19:1
Quote:The image is being reflected off of several mirrors and thru a lens, several lenses if the FR is also being used. Does this effect the brightness of the image in a noticable way?
Quote:Second, is a whole host of images ... taken with a Meade 12" ACF bare (no reducer/flattener, etc.).
Quote: Quote:Second, is a whole host of images ... taken with a Meade 12" ACF bare (no reducer/flattener, etc.). +1.Just check images posted to 'CCD Imaging & Processing' forum by Rick J. The practical impact of the field curvature of the R/C and the ACF on the quality of pretty pictures is insignificant.
Quote:The blur radii given at the edge of the f/10 coma-free scope in the Celestron white paper (which may or many not be the actual spot sizes of the Meade ACF scopes), are smaller than 2 arc seconds - the common limit of seeing for long-exposure photography. So, nearly all of the size of the smallest stars isn't coming from either diffraction or field curvature, it's coming from the atmosphere.
Quote:Two things keep me from accepting such analyses. First, the standard professional scope type is the R/C, curved field and all. Yet, they use flat sensors and get scientifically-valid results from those instruments.
Quote:Quote:Two things keep me from accepting such analyses. First, the standard professional scope type is the R/C, curved field and all. Yet, they use flat sensors and get scientifically-valid results from those instruments.Another is the R/C design as it relates to astrometry. The inherit aberration in an RC is astigmatism, however this has one nuance that means it will have no effect on use in measuring positions in that the star centroid is always in the same spot relative to the blur of the spot plot. That is the reason the RC design was chosen for this role. Field curvature will not affect that (other than reduced sensitivity, as I understand it).As for how images look in scopes with field curvature, it's hard to tell how they were focused as well. Could be going for a midway point to try to average things out (little less focused at center, more at the edge). This is often what people suggest to do with standard SCT's and visual observing. I find it just looks "soft" everywhere.
Quote:And it confirms what another forum member told me a couple of weeks ago, which is that the formula for the EdgeHD scopes had changed (f/1.9 primary).
Lance 1X binoviewer
C9.25 (because 1X just doesn't get it done)
C11 Edge CGEM DX Gary Honis Modified T3i ASI120MC http://www.astrobin.com/users/astroricardo/
Quote:I still think the C9.25 Edge is priced too high vs. the others. $1000 more for HD! And you can always say "less glass".
“I am the only person to ever ace a 1951 USAF resolution test. My 'to observe' list says 'done'. I do not use charts or atlases when I starhop; men do not use maps. One of my sketches won an SBIG deep sky imaging contest. I am the life of star parties I have never attended. I never say anything looks like a faint fuzzy - not even a faint fuzzy. Pilots aim green laser pointers at me. Don Pensack proofreads my CN forum posts.” - The Most Interesting Astronomer in the Universe
Quote: And way to go Celestron for waiting how many years after the HD came out to really explain this? Even their marketing made it look like an imaging instrument. Oh well, at least I have a telescope again.
Quote:What an awesome document. I ordered a Edge HD 800 and can't wait for delivery. Got a deal on an open box sale from a well known supplier and saved $300. Just got the UPS delivery notice for delivery on 12/5. I can't stand it so much I already added it to my signiture!!
G11/Gemini-2/OPWB Canon 60D (unmodified) with 18/55mm kit lens and "nifty fifty" lens Assorted M42 screw mount lenses (28mm thru 300mm) Celestron 102GT refractor (Costco special) 8/10 inch astrograph someday. DeepSkyStacker 3.3.2 StarTools 1.3 http://www.astrobin.com/users/StarGale/ http://everettastro.org/
Quote: The C9.25 is the best corrected on axis, with even the spherochromatism reduced to below the airy disk.
Quote:And because blue rays are strongly concentrated inside the Airy disk, the 8 inch EdgeHD is diffraction limited in blue light.