Leica 8x20; Nikon Action 7x35; Vixen Apex Pro 8x42; Orion 15x63; Docter Nobilem 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet
Adam AP Mach 1, Rob Miller TRI36L, Celestron 8" Edge HD Hyperion 17mm, Celestron 40mm Plossl, TMB 7mm & 9mm WO 66, Lunt LS60/B1200 PT, CG-5 Clone STF-8300m Pro Package, Honis-Modified Canon XS, Un-modded T1i, SSAG, TSOAG9, SX Lodestar
Lackawanna Astronomical Society
Quote:So if you have a reflector and want an apo in the 100mm range, just cut up a piece of cardboard. I think you would end up with something like a F/25 apo (if I did the math right).
Quote:The smaller refractor does have a better image but less information in it.
David Cotterell Toronto, Ontario "If an observer actually sees an object, there is no point in referring to a formula to find out whether he ought to see it; and if he fails to detect it, no formula will ensure his success." - W.H. Steavenson 8" f/15.5 TEC Maksutov 16" f/5 Teeter/Zambuto Dob 66mm WO SD AT 65EDQ APO Refractor Astro-Physics Mach 1 GTO Mount iOptron ZEQ25 mount Canon 60Da
I live south of Sydney Nsw, And used to own the Tak 210 mewlon. I found the seeing conditions would always be a problem for my location. I ended up selling and hunted down a Tak FS 128 so happy with that scope.
I find refractors better for me in my area , I do have a very good carbon fiber 9.25 sct for when the seeing is good.
Quote:Coming Sunday I am expecting my new Mewlon 250 CRS - directly from Takahashi, so to speak, as I live just a few miles from the factory.
Quote:Quote:Coming Sunday I am expecting my new Mewlon 250 CRS - directly from Takahashi, so to speak, as I live just a few miles from the factory.
Photos or it didn't happen
Quote: under all circumstances
Quote:"Under conditions of poor seeing, large instruments are relatively disadvantageous because the influence of air currents increases with the square of the entrance pupil diameter."
However, this is just a statement. I am missing an explanation why this should be so. Do you or someone else have an idea?
Why are larger scopes more affected by bad seeing?
Norme 150mm MCT f/13, 31% CO Yellow Zone "People say I'm in denial. I disagree."
Kmart 40mm-Thanks Mom|Jason60mm-Thanks Dad|C80SS-Thanks Wife|C90|C102|C6XLT|AP130EDFGT|C-11XLT EQ-2|EQ-3|CG5GT|Mach 1 & Eagle "For once you have tasted flight, you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return".-Leonardo da Vinci "We're all in the gutter, but some of us are looking at the stars."-Oscar Wilde ~RIP Dad, you were my best friend...Godspeed!~
Quote:The only variable the above leaves out is the wave front error of the objective. If the above 150mm refractor is made to 1/10 wave or better (totally realistic in high end apos) and the 300mm reflector is only made to 1/8 wave or slightly worse, the reflector will certainly be affected more by the seeing conditions than the refractor and this degrades what information can be delivered to the eyepiece. The 1/8 wave reflector goes to barely 1/4 wave diffraction limited, while the refractor maintains 1/5 wave or greater, staying ahead of the diffraction limit and producing a better image. This is why many say that having just a diffraction limited, 1/4 wave scope is not enough.
Clear skies, Erik
Visual astronomer, main instruments:
Matthias Wirth 16" f/5 Takahashi FS-102 NSV on EM-10 Celestron 1983 C5
Zeiss, TeleVue and Celestron eyepieces
Nikon 18x70 IF-WP Zeiss Victory FL 7x42 Zeiss Victory FL 10x32
Quote:The only variable the above leaves out is the wave front error of the objective.
Quote:In addition to the above, consider that 34% CO introduces roughly 1/4 wave abberation to the wavefront entering the telescope. That is why refractors start with an unequal advantage.
Quote:And as I understand it, that CO is beneficial for seeing tight double stars with faint magnitudes by spreading the energy away from the primaries airy disk, reducing its brightness, thus making the secondary star pop into view, but the effect is still a negative when it comes to producing a planetary image.
I ache, therefore I am
Quote:Here is the explanation.
Quote:Would a stopped down 250mm Mewlon would be any worse than a 6" apo? Might be an interesting experiment.Ed
"I like to watch"