APM 105/650 Travelling Visual Observer
Orion XT12i with Swayze-refigured primary/Protostar secondary
Televue NP101 refractor
William Optics Megrez 90 refractor
Universal Astronomics Deluxe Mounts
Orion ED80 - AT Voyager with TNT,pier ext.,Vixon steel tray and Manny's mod.
Omni 120 cg4 with Orion pier ext. and RA drive
Orion XT10(Original F/5)
Jason Constellation Model 311(Modified with 1.25"Crawford Machine focuser & rings)
Binotron-27 (25mm & 17mm Sterlings)
Quote:I'm pretty sure that the 60mm SV finderscope that FirstSight mentioned can be had with a 2" focuser so this might be the widest.
But the view is not pretty and I disregard f/3.7 finders and binocular objectives as being acceptable telescopes. My 80mm UO finder has a focal length of 300mm and could provide an 8 degree Tfov but its messy at 5 degrees with well corrected eyepieces.
Quote:What is the widest TFOV refractor, and how would it compare to binoculars of same aperture?
Leica 8x20; Nikon 7x35; Vixen 8x42; Orion 15x63; Docter 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet
Quote:The widest or I should say fastest objective I've ever seen is the 155mm (6.1") diameter air spaced achromatic triplet objective with a focal length of 195mm (f/1.25) that is sold on surplus shed. One could make a extremely fast refractor with it.The Tak FS60 in conjunction with the Tak 2" adapter is also a good wide TFOV refractor. Borg also has some pretty wide refractors as well.
Quote:Quote:What is the widest TFOV refractor, and how would it compare to binoculars of same aperture?If they have the same aperture, the binocular's view will be noticeably brighter because you're using both eyes. It will also be brighter than using a binoviewer on the refractor.If you use a high quality binocular, the weakest link in your viewing system will be your eyeballs, in particular the optical correction of your eye lenses at their wide open setting. This also affects the view through the refractor if it operates at the same exit pupil, largely eliminating the benefit offered by its sharper optics.My personal view on the question is that a high quality binocular will have the benefit of a brighter image with better contrast (speaking of the same low magnification and equally large exit pupil in both instruments). The refractor will have the advantage of being able to use highly corrected large-AFOV eyepieces so you can reach a wide TFOV view at a smaller exit pupil, reducing the influence of eye aberrations (i.e. a sharper view), but at the expense of brightness. But the increased magnification would also show more detail, which is an important advantage.So it would seem for a given TFOV the choice is between image brightness (the binocular) and sharpness + detail (the refractor). On this basis alone, I'd pick the refractor. In practice however, the handling and ergonomics of the two instruments are so completely different that this cannot be ignored.
Quote:If a binocular type instrument is simply two "refractors" strapped together then my 2.4x40 Russian gallieans with a 27° afov would not be too shabby.But, more along the line of the OP, I have a 50mm f/4 decent quality achro (bino objective) that can do 5X with a 2-in 40mm eyepiece resulting in a 14° afov. Obviously the exit pupil is 10mm but what did Uncle Al say... Incidently, this objective also can provide decent images above 40X.
Quote:How low (and wide) can you go? Brings to mind the old "Limbo" song.As others have said, you can get very low powers and wide fields of view if you reduce focal length and have the capability of using a 2" (or larger) focuser that does not obstruct the light path either with or without a diagonal.I have a nice Zeiss (West Germany) copy lens scope that I have fitted with a 2" focuser and I can use it with a 2" diagonal. One of my monster eyepieces is a Jaegers 38mm in a specially machined adapter. The clear aperture of the field lens is 48 mm and the focal length of the objective (54mm aperture) is 300 mm. So I have a 54 mm f/5.6 telescope giving me 7.89x (6.84 mm exit pupil) with a 9.17 degree field. Edge correction is about equivalent to what I see in my Fujinon FMT-SX 7x50 binoculars (and that is pretty good). The true advantage of this setup is the eye lens of this eyepiece is huge! You literally fall into "space". Plus the scope was cheap to make.Barry Simon
Binoculars: Miyauchi Saturn III - 33/39/50/71/150x100, WO22x70ED, Fujinon 16x70 FMT-SX Pentax 10x50 PCF-V, 10x43 DCF-SP, 6.5x21 Papilio
Nikon 10x35 EII, 7x35 E, 8x30 EII, 8x23CF AS Diplomat
B&L 7x26 Custom
Scopes: C9.25, TMB130SS/FT, SV80S-LOMO 80/480
Quote:SOMEONE ABOVE commented that the SV-60 is capable of being configured with a 2" focuser, which unfortunately I doubt is true.
Quote:Wide and picture perfect views: Takahashi FS-60CB.
Quote: I wonder why they don't make finder scopes with 2" eyepieces for wider views? Since this is what alot of your proposals are starting to look like.
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:Stellarvue 50mm f/6.6 refractor. 8.48 degrees FOV with a 41mm Panoptic.
Quote:Uses an SCT thread. Comes with a compression ring 1.25” visual back. Focus travel is 2 5/16”.
Quote:hat about WOrion ED80T CF Triplet Apochromatic Refractor and 40mm 70AFOV 2" eyepiece as a wide TFOV finder?
Bill The opinions expressed herein are solely mine as an amateur astronomer hobbyist & consumer. Information herein was correlated from experience, discussions with others, & research from multiple sources freely available at time of posting. All reasonable care & skill was used, but no warranty is made as to accuracy, & liability cannot be accepted for errors/omissions. This is for information only and not intended nor implied to be a substitute for professional advice.
My eyepieces are made from the waste product of exploding stars. 10XTi 102XLT ST80A(2" Focuser) XW: All; XO: 2.58 Televue: Naglers-T1 Smoothside-full set, 17T4,12T4,Ethos 17,4.7; plossels-40,32,20,17,&7.4mm; Pans-22,24mm; Delos-6,8,12,17.3mm ES100: 5.5,9*,14,20 ES82: full set ES68: 16,20,24,34 NLV: 5,9,10,15 Ortho: HD-7,9; OPS-9,12 Meade RG 7mm Other: Pentax 12.5K(.965), 10mm Parks Zoom: Nag3-6 *=on b/o DAS Dark Site
Quote:Using a 30mm Leitz Astroplan 88°eyepieceit is possible to get a 11° field with my 60mm F4 Stellarvue finderscope and 2 " helicalfocuser with 8x magnification,a 7.5° field with my 80m F4 Finderscope with 11x magnificationand a 4.4° field with 120mm F5 Synta Refractor and 20x magnification.