Quote: It depends on your pupil size during dark adaption.
Quote:The readily available 2" 55mm Televue Plossl will give you 28X.
Quote:Yeh it would be crazy to use in that scope, but it does give the lowest mag.
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
Quote:If your pupils can get to 7mm, I would get the 31 nagler without a paracorr
Quote:A final consideration is that very low powers used in conjunction with an obstructed telescope can cause the appearance of a shadow in the middle of the fov when looking at the Moon. It's a mystery to me why this only happens at very low powers but it does. JimC
Tom Karpf (tkarpf) Vice President, Astronomical Society of Greater Hartford www.asgh.org
Selsi 60mm f/13 Lunt 35mm Solar Scope Stellarvue SVR70ED
Astronomy Technologies AT6RC Home-built Dobsonian with home-made mirror -
8" f/6.8 Unistar Deluxe on a surveyor's tripod
Quote:The lowest magnification possible for any telescope has been traditionally determined by the human eye, with its maximum dilated pupil opening of about 7mm.
Orion XT12i with Swayze-refigured primary & Protostar secondary
Televue NP101 refractor
William Optics Megrez 90 refractor
Universal Astronomics Deluxe Mounts
Quote:Quote:A final consideration is that very low powers used in conjunction with an obstructed telescope can cause the appearance of a shadow in the middle of the fov when looking at the Moon. It's a mystery to me why this only happens at very low powers but it does. JimC
The black dot is the secondary mirror (seen from the back).
It's because it's only at low powers that it's big enough to be noticed. If your scope has a 20% obstruction, than that black dot is 20% of the exit pupil size; not so visible when you have a high powered eyepiece (0.5mm exit pupil, 0.1mm black dot), but much more with a lowe powered eyepiece (7mm exit pupil, 1.4mm black dot). With compound scopes (SCT, MCT, RC, etc.), the obstruction percentage is greater and so the black dot is bigger.
14" f/4.8 Obsession Clone w/ ServoCat/ArgoNavis Apogee RA-88 Binocs
Quote:jtrevino- My DOB is almost identical to your's- 14", f/4.8My favorite ep is the Nagler 31mm- this gives me 57 power. The fov is wide enough that even with a Paracor in place, the entire Pliedies is in view. Since I'm strickly visual and love DSo's, this combo practically lives in the focuser.
Celestron C11+EQ6, skywatcher /Zambuto 12"dob,watchhouse tracking platform, 16"/Zambuto lightbridge , Ethos's 6,8,10,13,17,21. Naglers 31,26. Lieca ash zoom, televue 2.5 powermate,2"2x powermate .Paracorr type2. Howie glatter 2" laser & Tublug. Lumicon 2" UHC, 03, H-Beta,Televue smoothies ( all of em) , Meade 4000 smoothies ( all of em). That'll do for now.
Quote:I can just fit the Pleiades in my 12" , F5 , focal length 1500 mm, scope with a Meade 40 mm super wide , and it fits very nicely in my 55 & 56 mm plossls , I can also look at the moon without seeing the secondary shadow.
David W. Knisely . . . . . . "If you aren't having fun in this hobby, you aren't doing it right." Hyde Memorial Observatory http://www.hydeobservatory.info Prairie Astronomy Club http://www.prairieastronomyclub.org
Quote:Quote:I can just fit the Pleiades in my 12" , F5 , focal length 1500 mm, scope with a Meade 40 mm super wide , and it fits very nicely in my 55 & 56 mm plossls , I can also look at the moon without seeing the secondary shadow.
With a 46mm field stop, your scope will provide a 1.75 degree TFoV. Whether that fits "all the Pleiades", it's close.
As far as seeing the shadow of the secondary when viewing the moon, do you see it when viewing the moon during the day? I don't always see it when viewing at low magnifications but I do see it sometimes.
Quote: one good thing about the 55 & 56 mm plossls is to be able to see the veil in my F10 C11 with a filter on ,on that scope it's hard to see it even with a 40 mm eyepiece.also I quite like viewing with the big plossls in my 12" dob just scanning the skies at night to sweep big areas , I don't see the central obstruction and maybe it acts like a smaller aperture but I can't say I notice it and its a totally different view from what the skies normally look like , so I say forget about exit pupils and lowest practical powers and enjoy it , they are nice eyepieces to have and use.