17.5" f4.1 Manual Discovery Split Tube Dobsonian (Love 100 AFOV and wide TFOVs).
Denk II Dual Power Switch 3x3=9 powers x3 OCS = 27 power options per eyepiece pair.
2.3x40 to 25x100 Binos (and many in between).
Jeff -----TEC 140, Stellarvue SVR90T, SV115T20 and AT65EDQ refractors,Webster D14, C11 EdgeHD Lunt LS60THa solar scope double stacked with LS60FHaTelevue Pan 41; Ethos 21, 17; Nagler 31T5, 9T6, 7T6, 5T6, 3.5T6; Delos 10, 12, ES25, 14, 9Astro-Physics 900GTO with Rob Miller Tri36M TripodDM-4 Mount-Extension-Tripod w/ Sky CommanderDM-6 Mount-Losmandy Adapter/Extension-Berlebach Planet w/ Argo Navis
Vixen ED114ss Custom Nikon ED50
Quote:I will defer that opinion until I have a chance to try them both out in the Obsession 20F5. That would give me a better idea of how it works in a faster scope. When I was trying identify smaller galaxies the additional magnification with the ES 25 was apparent. I didn't have a chance to look a extremely wide objects such as the North America or Veil nebula.
Quote: Do you think there is any advantage in trying to sell 3 T4s as a set?
"You're not afraid of the dark, are you?" - Riddick "The best scientists are humble. They seek to understand, not to ensure their legacy, but merely to understand." - Mori
Paul 16" Starstructure f/4 w/AN-SC and Zambuto optics Celestron Edge HD 1100 Lunt LS60DS Orion 8" imaging newt Explore Scientific ED127 CF Apo Astro-Tech AT65EDQ Astro-Physics 1100 mount Celestron AVX mount Mallincam Xtreme Denk Binotron
Quote:What do you mean when you say field curvature offset coma?Field curvature slowly defocuses the star images, but they stay round. Coma stretches the star images radially into fan shapes.Field curvature can defocus coma, too, making the comatic image slightly larger and out of focus, but it doesn't reduce coma. It can only make the appearance of it worse.So what you say cannot be reconciled.I notice a slight amount of astigmatism near the edge, and depending on which side of focus you sit, this could appear to reduce the radial width of the comatic star (while stretching it circumferentially). On the other side of focus, it would make it worse.I got a quick glance at the Perseus Double Cluster with the eyepiece in a Paracorr II, and the star images displayed a trace of astigmatism, but no obvious coma or field curvature. Since the Paracorr corrects the last two, it's not surprising what I saw. Without the Paracorr, it displayed the normal amount of coma for an f/5 scope and a 100 degree field, i.e. a lot.However, if the eyepiece actually corrected coma, it would display coma in the Paracorr, and it did not.Once again, current eyepieces do not correct for coma. If they did, they'd only be useful in short f/ratio newtonians.Edit:It just dawned on me that what you are calling field curvature is actually rectilinear distortion (wherein straight lines appear curved near the edge of the field, so ||| becomes )|( in the eyepiece.Yes, the eyepiece has a lot of that, as do other 100 degree eyepieces.The correction of RD is impossible in a widefield eyepiece without leaving in tons of Angular Magnification Distortion (AMD), which is considered to be the more deleterious form of distortion in astronomical viewing.RD is more noticeable when panning quickly, but usually doesn't bother most observers. AMD, on the other hand, distorts images terribly, so most modern designers opt for RD over AMD.Field curvature is when the focal plane is curved toward or away from the eye at the edge and it results in out of focus stars. I don't think that was what you were talking about.
22" f/4 Sayre Monocular, Tom Osypowski Equatorial Platform (since 1995), Assorted small telescopes 76-152mm; 25mm ES100°, 20mm ES100°, 13mm Ethos, 9mm ES120° (serial #18), 9mm ES100°, 8mm Delos, 6mm Ethos, 4.7mm Ethos, 3.7mm Ethos SX, 2.5mm Nagler Type 6, 2" 2X Powermate, 2" 1.5X Proxima Barlow, 2" GSO Coma Corrector, 18mm BCO, 10mm BCO, 6mm BCO and other 1.25" eyepieces. Zhumell 8x42 Nova Phase-coated ED Binoculars, Burgess 25x100 Binoculars
Quote:I am not trying to decide on which one to keep. For me, the ES 25mm 100 AFOV is a keeper along with the 21 Ethos and 31T5 Naglar. I think it is finally time to put my T4 Naglars on the market. I really like the 22T4 and 17T4, less so the 12T4. These were my first 3 Televue eyepieces. I just can't fit them all in my case. It is also getting to be a bit heavy. I may buy a Paracorr type II with the proceeds from selling the T4s. Do you think there is any advantage in trying to sell 3 T4s as a set?--------------------Jeff
10" F/4.7 Modified Skywatcher Reflector, 38mm Orion Q70, 17mm Modified Ultima LX, 10mm TeleVue Delos, 7mm Pentax XL.
Two eyeballsAP 5.1" f/6 on a GM-8 -- The Instrument10" f/4.8 Newt on a Dob -- Marcia!! Marcia! Marcia!!!12.5" f/4.5 Portaball -- The CojoneLunt LS100FHaBinotron 27Fujinon FMT-SX BinosBlack & Green Glass
Hauppauge, NY -
RMSP, NY -
Remember to have your clouds spayed or neutered, contrails included.
Quote:So far I've only been able to use the new EP for about an hour and my initial gut feeling is that I won't be using the ES25100 as a daytime EP. Reason being is that during this short time I already think that the distortion will more than likely be too great for me to overcome. Normally I can handle distortion very well but the amount in the ES25100 is pushing it for me. I felt that I got a bit light headed after viewing with it so no matter how good the EP is if it makes me sick I won't be using it. Hopefully I will get use to looking through a fishbowl without loosing my lunch.
Quote:I will defer that opinion until I have a chance to try them both out in the Obsession 20F5.
Fred StarStructure LE Series 18" f/4.3 (Zambuto & Nexus/ServoCat/Skytools3 Pro) Celestron 8" SCT w/Starlight Feathertouch Microfocuser; Celestron 102mm f/9.8 refractor Stellarvue SV80ST f6 Triplet APO Tele Vue & EarthWin binoviewers Enough Eyepieces and Accessories to put my Scopes to Good Use Free-Turn Q HalfHitch, CG5-ASGT(2), Astro-Tech Voyager mounts
Quote:Has anyone determined the Paracorr setting for the ES 25mm 100°? I fiddled with it some in a friend's 16" f/4.2 as I haven't had a chance to try it in my own scope, yet. Seemed the C or D setting was getting it close. I think B was best for my ES 9mm 100°. Comments?
Quote:Thanks, Don. That's what I did, but perhaps it's the rectilinear distortion of the EP (plus my own slight astigmatism) that's having me waffle between C and D. I used a 24mm Pan set to D and focused before inserting the ES 25mm. I should be able to spend more time on it Wednesday night when I'm out with my 18".
Quote:BTW, I REALLY like the 25mm. I believe it will be my most used wide field ep. Same TFOV a my TV 31mmNT5 but with a more comfortable exit pupil, slightly better contrast with darker background.
Homemade 14.5" f4.3 Truss Dobsonian
"I'd like to remind you at four in the morning my world is very still, The air is fresh under diamond skies, makes me glad to be alive." Randy Bachmann "Blue Collar"
“A mind is like a parachute. It doesn't work if it is not open.” ― Frank Zappa