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Pages: 1 | 2 | (show all) astro_que sage Reged: 11/11/09 Re: Questar vs TV 85.... [Re: Erik Bakker]       #3674410 - 03/11/10 11:27 AM Edit   Reply   Quote Quick Reply   Clive, I called Jim Reichart this morning. He called the coating shop, they put their heads together, and he just called me back. The official figure for light transmission through a BB scope, "all surfaces", is 96%. It is calculated in this way: 1. Mirrors: 1% per surface. These are the finest dielectric enhanced silvered mirrors money can buy, bar none. 2. Control box prism: 1% per surface. 3. Corrector: negligible loss. The official, Questar sanctioned figure for QE, end-to-end, all surfaces, for the 90 degree port, is 96% Through the axial port, the quantum efficiency is 98% Post Extras:       NeilR super member Reged: 02/18/08 Re: Questar vs TV 85.... [Re: astro_que]       #3674455 - 03/11/10 11:47 AM Edit   Reply   Quote Quick Reply   One of the charms of owning a Q is Jim Reichert, who does things like this all the time. Post Extras:       Brent super member Reged: 11/18/04 Loc: NE Missouri Re: Questar vs TV 85.... [Re: BDS316]       #3674462 - 03/11/10 11:51 AM Edit   Reply   Quote Quick Reply   Quote: This is my first post on the questar forum so try to take it easy on me...I'm researching my 50th birthday present. Hi Bryan, We'll go easy on you -- even if we do like to pick nits with each other. Either scope would, I think, make a wonderful birthday present. And either would make a fine companion to the XT8 you already have. I can't speak directly to a comparison between the TV-85 and the Questar, but having both small refractors and the Questar, I'll offer the following (which you probably have already considered anyway). If I, personally, liked deep sky observing more than solar system AND would be observing most often under dark skies, I'd go for the TV-85. If I preferred solar system observing, I'd get the Questar (the images would be comparable, but the convenience of the Q would decide the issue for me). If I liked both types of observing -- or perhaps regardless of which I liked better -- AND would view most of the time from light polluted skies, I'd probably go for the Q. I like all types of observing, but deep sky is my first love. When I drive out to a dark sky site, I usually take the NP-101. But if I'm just setting up for some observing in the yard (solar system or bright fuzzies), I'll usually set up the Questar. Images in the NP-101 are contrastier, and crisper and brighter than in the Questar. But the Questar images are really close enough that for observing in my light-tainted yard, the convenience makes the Questar the scope of choice most nights. In sum: for truly dark skies I prefer my refractor; if my observing is going to be limited by light pollution anyway, I'll use the Questar. I assume this might hold true for scopes still more evenly matched in aperture. Just my two cents. happy birthday and what a wonderful quandry, Brent Orton Post Extras:       GR1973 super member Reged: 09/29/07 Re: Questar vs TV 85.... [Re: NeilR]       #3674467 - 03/11/10 11:53 AM Edit   Reply   Quote Quick Reply   Hi Neil...I read this disscusion I am relatively new to Questar family (Late 2007 new BB).. I read older posts in Questar yahoo group...they have the best answers for chronic repeated questions....This is the URL for this disscusion: http://tech.groups.yahoo.com/group/Questar/messages/12286?threaded=1&m=e&var=1&tidx=1 message : #12286 to #12314 My advise to all new members to read older posts in our yahoo group. Best regards Post Extras:       Clive Gibbons Mostly Harmless Reged: 05/26/05 Loc: Oort Cloud Re: Questar vs TV 85.... [Re: astro_que]       #3674535 - 03/11/10 12:30 PM Edit   Reply   Quote Quick Reply   Quote: Clive, I called Jim Reichart this morning. He called the coating shop, they put their heads together, and he just called me back. The official figure for light transmission through a BB scope, "all surfaces", is 96%. It is calculated in this way: 1. Mirrors: 1% per surface. These are the finest dielectric enhanced silvered mirrors money can buy, bar none. 2. Control box prism: 1% per surface. 3. Corrector: negligible loss. The official, Questar sanctioned figure for QE, end-to-end, all surfaces, for the 90 degree port, is 96% Through the axial port, the quantum efficiency is 98% If that's the case, you might do them a favor-- call Jim R. back and inform him that the info posted by Questar at the website doesn't add up. Post Extras:       Steve C. sage Reged: 01/24/08 Loc: Sugar Land, TX Re: Questar vs TV 85.... [Re: Clive Gibbons]       #3674539 - 03/11/10 12:33 PM Edit   Reply   Quote Quick Reply   The only real solution is to buy both. Post Extras:       greedyshark sage Reged: 10/31/05 Loc: 3rd Rock Re: Questar vs TV 85.... [Re: Steve C.]       #3674631 - 03/11/10 01:03 PM Edit   Reply   Quote Quick Reply   Quote: The only real solution is to buy both. Great answer, Steve! CS, Charles Post Extras:       Fomalhaut scholastic sledgehammer Reged: 08/16/08 Loc: Switzerland Re: Questar vs TV 85.... [Re: Steve C.]       #3674970 - 03/11/10 03:42 PM Edit   Reply   Quote Quick Reply   Quote: The only real solution is to buy both. => One more for looking at and the other one more for looking through ... Chris Post Extras:       Clive Gibbons Mostly Harmless Reged: 05/26/05 Loc: Oort Cloud Re: Questar vs TV 85.... [Re: Fomalhaut]       #3674986 - 03/11/10 03:50 PM Edit   Reply   Quote Quick Reply   Yup, those TV-85's are sure pretty sitting in the den. Post Extras:       Eric P sage Reged: 04/04/05 Re: Questar vs TV 85.... [Re: BDS316]       #3679495 - 03/13/10 09:53 PM Edit   Reply   Quote Quick Reply   Quote: Has anyone done a direct comparison between these 2 fine scopes? thanks I have a late 60s Q3.5 quartz and a TV85. I've compared both side by side with the same eyepieces and overall prefer the views in the TV85 (especially wide field when coupled with a Panoptic 24). Of course my Q is at a disadvantage with its 40+ yr old coatings, so I don't know how a modern one would fare. That said I prefer using the Questar to any other scope I own or have owned. The mechanical nature of it, the well thought out design and the superb quality of the construction makes my heart go a 'flutter every time I extricate it from its finely stitched English leather crypt. Post Extras:       Edwin Quiroga professor emeritus Reged: 01/31/08 Loc: Miranda, Venezuela Re: Questar vs TV 85.... [Re: astro_que]       #3680318 - 03/14/10 01:11 PM Edit   Reply   Quote Quick Reply   Quote: (...) 2. The focal length of the Questar is much longer than the Televue, making it perform well with eyepieces of classical orthoscopic design,and the Brandons. The reputation for fabulous detail may in part be due to this. Because the TV-85 has a short focal length, modern eyepiece designs with 6 or more elements and integrated barlow are required to get diffraction limited resolution. Orthoscops will not work well with it, and the Plossl eyepiece design is diffraction limited only in a zone 30% from the center. (...) Sorry, that's not what my eyes have seen. The Plössl that comes with the TV85 (TV 20mm) and the XO 2.58 that I have are really sharp and beautiful until the edge. The same with good plössl and "super plössl" (5 elements) eyepieces that I have probed in this 2 years with the TV85. The same with my former RKEs 15mm in binoviewing mode. Post Extras:       astro_que sage Reged: 11/11/09 Re: Questar vs TV 85.... [Re: Edwin Quiroga]       #3680378 - 03/14/10 01:53 PM Edit   Reply   Quote Quick Reply   Edwin, regardless of what your eyes have seen, it's an optical fact. Quoting from Chris Lord's eminent treatise, "Evolution of the Astronomical Eyepiece", page 31, "However, unlike the Abbé Orthoscopic and its derivatives, where longitudinal spherical correction is zero on axis, the assymetric form of the Plössl leads to a zonal correction and the sharpest imagery does not occur on ax is but some 30% towards the edge of the field of view. At low to medium powers this is of no consequence, but it is noticeable at highpowers (exit pupils less than 1.5mm)." You may download this excellent treatise at http://www.brayebrookobservatory.org/BrayObsWebSite/BOOKS/EVOLUTIONofEYEPIECES.pdf In this article, http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/PageMill_Resources/Comparison%20test%20of%20TVPlossl%20vs%20Brandon.pdf Chris Lord found that inexpensive GSO Plossls outperform your Televues. Quoting from page 10, "However by far the best value is the GSO Plössl. It consistently outperformed or rivalled the TV Plössl at roughly half the price, even less if bought cased via Amazon. Not only does the GSO Plössl represent the best value, it ranks overall a better planetary eyepiece than the TV Plössl, exceeded only by the Brandon which costs almost ten times more." Post Extras:       Edwin Quiroga professor emeritus Reged: 01/31/08 Loc: Miranda, Venezuela Re: Questar vs TV 85.... [Re: Erik Bakker]       #3680392 - 03/14/10 02:00 PM Edit   Reply   Quote Quick Reply   Despite how much I like the Questar design and how much I enjoy reading this Questar forum, I feel my duty to point out some points about our fellow Erik`s statements regarding the TV85. Quote: 1. the Questar 3 1/2 is a portable day and night observatory, the TV 85 is an OTA. Enter a good mount and the prices are roughly the same. The weights and sizes are not. Look and feel of both scopes (mounted) is very different. My TV85 with a very sturdy Manfrotto legs, Telepod Head does not reach $ 2,500. Maybe you are talking about an EQ mount. Some adequate EQ mounts are around 350 $. The cheaper Questar is... 4.250$? Quote: 4. The Questar is an APO, the TV85 a semi APO. In despite the minimun color that the TV85 can show in very bright objects SOME nights (the most time due to atmospheric conditions) call it semi-apo is not correct, IMHO. Semi-apo was, for example, the Pronto. Quote: 5. The Questar can reach unbarlowed magnifications of 100-180 x with ease with a 12mm Brandon, the TV 85 needs 3-6mm zoom to do that. You can reach 170x-240x with the TV85 with COMFORTABLE eyepieces plenty of eye-relief like Pentax XW 3.5, Radian 3, Nagler 2.5... There are several eyepieces with very short FL suitable for this scope. Quote: 7. The Questar is unparalelled in it's total observing experience, easily providing many hours of comfortable seated (high power) observing any night. This is a very subjective opinion. I have spent many whole nights (from dusk to dawn) sitting comfortably with my TV85. You can talk to me about the Questar magical observing experience. I could refer to you about the "magic of the TV85". Quote: 8. Cooldown for the TV 85 is ca 1/2 hour, for the Questar ca. 1 hour if taken outside from a living room to say 0 degrees C.. A half hour? This is a valid consideration only in very high or low latitude. In fact, at my home (25ºC year average) my TV85 is ready and full cooldown in barely 5 minutes or so. Best regards! Post Extras:       Edwin Quiroga professor emeritus Reged: 01/31/08 Loc: Miranda, Venezuela Re: Questar vs TV 85.... [Re: astro_que]       #3680427 - 03/14/10 02:15 PM Edit   Reply   Quote Quick Reply   Quote: Edwin, regardless of what your eyes have seen, it's an optical fact. Quoting from Chris Lord's eminent treatise, "Evolution of the Astronomical Eyepiece", page 31, "However, unlike the Abbé Orthoscopic and its derivatives, where longitudinal spherical correction is zero on axis, the assymetric form of the Plössl leads to a zonal correction and the sharpest imagery does not occur on ax is but some 30% towards the edge of the field of view. At low to medium powers this is of no consequence, but it is noticeable at highpowers (exit pupils less than 1.5mm)." You may download this excellent treatise at http://www.brayebrookobservatory.org/BrayObsWebSite/BOOKS/EVOLUTIONofEYEPIECES.pdf In this article, http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/PageMill_Resources/Comparison%20test%20of%20TVPlossl%20vs%20Brandon.pdf Chris Lord found that inexpensive GSO Plossls outperform your Televues. Quoting from page 10, "However by far the best value is the GSO Plössl. It consistently outperformed or rivalled the TV Plössl at roughly half the price, even less if bought cased via Amazon. Not only does the GSO Plössl represent the best value, it ranks overall a better planetary eyepiece than the TV Plössl, exceeded only by the Brandon which costs almost ten times more." My friend,I have seen many authorities and popes opinions and statements that frankly, is no married with my own experience. For example, small apertures is not suitable fof DSO observing. I will not discuss whether or Televue Plössl or GSO represent a better value because it is not what is being discussed now. I only commented that I have seen with a 20mm Plössl (30x in my telescope) and RKE 15mm (40x). I do not see such severe distortions, such as your statement seems to suggest. Well ... The center is sharper than the edge? About that sin is guilty most of the eyepieces. Whether because the 20mm plössl or the RKE 15mm are not giving much magnification on the TV85 or because the focal ratio is not so short (f/7) I can not be agree with your statement. Best! Post Extras:       Erik Bakker Carpal Tunnel Reged: 08/10/06 Loc: The Netherlands, Europe Re: Questar vs TV 85.... [Re: Edwin Quiroga]       #3680642 - 03/14/10 03:59 PM Edit   Reply   Quote Quick Reply   Hi Edwin, Relax. I love the TV85. As I stated, I love both my Q and my fluorites. My 70 mm fluorite doublet is somewhat comparable to the TV85, with the TV85 being brighter and with more resolution of course. It's good to hear about your passion for the magic of the TV85. Clear skies, Erik Post Extras:       Edwin Quiroga professor emeritus Reged: 01/31/08 Loc: Miranda, Venezuela Re: Questar vs TV 85.... [Re: Erik Bakker]       #3681987 - 03/15/10 09:42 AM Edit   Reply   Quote Quick Reply   No problem, my friend! I really enjoy your observing reports with your wonderful Q7! Best! Post Extras:       Pages: 1 | 2 | (show all)

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