Vixen 140mm Neo-achro, 2" AP Maxbright diagonal, 40mm Orion Optilux, 35mm, 30mm, 18mm, and 15mm Ultrascopic/Ultima, 28mm & 20mm ES 68, 19mm TV Panoptic, 5.5mm Meade UWA, 2.4x 2" Dakin barlow (prototype barrel),1.6x Antares barlow.
"I have been paddling in the shallows of a great ocean of knowledge." - Sir Isaac Newton * * 15" F4.55 Starsplitter Dob & a Denk II binoviewer * * http://peaceofsky.wordpress.com/ Pacheco State Park Fremont Peak
Quote: I haven't used a Siebert telecentric but I do have a 1 1/4" 1 1/2X barlow and I'd rate it optically as good as my TV Powermate and barlows. Light transmission and sharpness are excellent, it's like it's not there. David
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.
Quote: I have found that Telecentrics have little if any advantage, so don't need the extra glass or the extra costs.
Quote:There will be a difference (physics) as the telecentric design is 4 elements in 2 groups whereas the barlow design is 2 elements in 1 group. So very very slightly better transmission and scatter characteristics with a Barlow. However, as real as these differences may be, from a practical standpoint they would more than likely be either below the visual threshold or would only rear their head as being noticable under very narrow circumstances. I also have both a Siebert Barlow and Telecentric. Like them both and both very sharp and transparent. However, unless you are looking to use them on a longer focal length wide field type of eyepiece, the Telecentric/Powermate options I feel are of little use. I generally tend to use these add-ons for eyepieces of 20mm or shorter focal length and in this range I have found that Telecentrics have little if any advantage, so don't need the extra glass or the extra costs.
Quote: Quote: I have found that Telecentrics have little if any advantage, so don't need the extra glass or the extra costs. In my case i wasn't even planning on a 2.5x amplifier, but spotted the 2" Siebert Telecentric for an amazing *used* price! But now that i have it, its come in VERY handy for larger 2" EPs, and has given some amazing hi-power views when coupled with a 12mm T4 Nagler in my Dob (361x).
Quote: ...input on telecentrics flattening the field and eliminating the need for a paracorr.
Quote: I see OPT has one of these same Barlows in their "used" section.
Quote: Those UO 2-inchers sold for $55 new in the late 90's. They pop up now and again on AM for about $50.