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I am new to astronomy and have been looking at a number of telescopes. Can
someone please advise : What is the definition of "Rich Field Refractor" ie what does it mean. I havn't been able to find out on the web. Sorry if this is a dumb question. Regards AB |
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"Alan Buttivant" wrote in
: I am new to astronomy and have been looking at a number of telescopes. Can someone please advise : What is the definition of "Rich Field Refractor" ie what does it mean. I havn't been able to find out on the web. Sorry if this is a dumb question. Regards AB It usually refers to a short focal length refractor, which provides a wide field of view using moderate focal length eyepieces. They are therefore used for general scanning of the sky (a bit like giant binoculars) and (unless very expensive) will not be so good for high magnification planetary or lunar observing. Orion used to sell a scope called the ST80 which would fit the bill. Rgds Llanzlan. |
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"Alan Buttivant" wrote in
: I am new to astronomy and have been looking at a number of telescopes. Can someone please advise : What is the definition of "Rich Field Refractor" ie what does it mean. I havn't been able to find out on the web. Sorry if this is a dumb question. Regards AB nod, Orion still sells the Orion-ShortTube80(ST80), i found 1 on EBay with several other accessories & tripod for 205.00, its does a fair job for the money, of course refractor purists will prob bad-mouth it, i really like the view thru a refractor, presently have it mounted on my LX200, thumb-screw removable nice quik ToGo scope, one of these days i'll force myself into justifying the cost of a higher quality refractor, until then i'll be satisfied with my MCT http://www.GasRecovery.org |
#4
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![]() "Alan Buttivant" wrote in message ... I am new to astronomy and have been looking at a number of telescopes. Can someone please advise : What is the definition of "Rich Field Refractor" ie what does it mean. I havn't been able to find out on the web. Sorry if this is a dumb question. Regards AB They are Okay for general sky viewing, but they come up short for some of the cooler stuff.... I have a 120mm Refractor from Orion, with a focal length of 1000mm. Fun scope to run around with. Last night I locked it in on Saturn and it great... rings and all, with a 10mm lathium.... Then I dropped in a 25mm and the Orion Nebula was easily in view... I have one comment on the Skyview Pro 120... I get a bit of haloing at higher magnifications... but a V filter took care of that easily.... You might want to consider a 120mm "long tube" with a 35-50mm lens instead... |
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Thanks all for your advice. I guessed that a rich field refractor was a
scope that did not have the power of some other refractors and was perhaps smaller/lighter. I bid for a tal 100R on ebay and did not win the bid. A few days later I saw one for sale in a shop locally and was surprised by the size of it. Given its weight and size I wondered how I would have got it into the garden. I need something smaller/lighter but with sufficient power to keep my interest going and not too expensive. Any suggestions (direct to me if you prefer) would be appreciated. Regards AB "Alan Buttivant" wrote in message ... I am new to astronomy and have been looking at a number of telescopes. Can someone please advise : What is the definition of "Rich Field Refractor" ie what does it mean. I havn't been able to find out on the web. Sorry if this is a dumb question. Regards AB |
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![]() "Alan Buttivant" wrote in message ... Thanks all for your advice. I guessed that a rich field refractor was a scope that did not have the power of some other refractors and was perhaps smaller/lighter. I bid for a tal 100R on ebay and did not win the bid. A few days later I saw one for sale in a shop locally and was surprised by the size of it. Given its weight and size I wondered how I would have got it into the garden. I need something smaller/lighter but with sufficient power to keep my interest going and not too expensive. Any suggestions (direct to me if you prefer) would be appreciated. Regards I have an ORION.. but that is me.... Before you go shopping, search the groups and the net for reviews of ones you are interested in, then go to the shop... nothing beats that hands on approach. The Mount is just as important as the tube, a shaking tripod is just going to make you frustrated and it will spend more time in the closet than in the garden. With that in mind, it is alos going to be the heaviest part of the scope. In the time you take researching and shopping, learn all you can about the mounts, the different optics and how to use them. I know this helped with me... If you want something you can just pick up and go out into the garden and scan the sky, think about a Dobson mount. I got one for a friend, and he gets alot more sky time than I do, becasuse he can just drag it out of the closet and plop himself down in chair and enjoy.... I have to level and align my mount, get the tube on, check the tracking, let the optics cool.... then I get to play... Come to think of it... maybe I should get a dobson... The Plus's of a refractor is that you can also use it for land observation... I am a journalist and I take mine out and used it during the big fires here in California, I mounted my Nikon on it and got some great shots... all in relative safety... When I worked for a surfing magazine.. (LOOOONG time ago) we did the same thing, |
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A "rich field" refractor is a refrector that has a focal ratio of f/5 and
lower. Focal ratio is the Focal Length divided by the the aperture. For example, a scope with a 1000mm focal length (FL) and a 254mm (10") aperture, has a focal ratio of 4 (3.93 really), written as f/4. Charles Nashville, TN USA "Alan Buttivant" wrote in message ... I am new to astronomy and have been looking at a number of telescopes. Can someone please advise : What is the definition of "Rich Field Refractor" ie what does it mean. I havn't been able to find out on the web. Sorry if this is a dumb question. Regards AB |
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Alan Buttivant wrote:
I am new to astronomy and have been looking at a number of telescopes. Can someone please advise : What is the definition of "Rich Field Refractor" ie what does it mean. I havn't been able to find out on the web. It is a refractor which has been developed to provide wider fields of view at lower power than other long focal length "planetary" refractors. Usually, there is not a strict f/ratio definition, but you will often find simple 2-element objective refractors with f/ratios of f/6 and lower termed "rich-field" instruments. Their performance at very high power isn't quite as good as with some of the much longer f/ratio refractors, although they can often still provide at least passable high power performance. I have a 100mm f/6 refractor and it provides some of the best wide-field views of the night sky I have ever seen, although its high power performance would definitely put in the "rich-field" class. The Apochromatic refractors (3-element or more objectives) like the TeleVue 101 are more "all-purpose" instruments than rich-field despite their shorter f/ratio. This is mainly due to the high quality of their objectives which allows good to excellent performance at just about any power, and over wide fields of view as well. Clear skies to you. -- David W. Knisely Prairie Astronomy Club: http://www.prairieastronomyclub.org Hyde Memorial Observatory: http://www.hydeobservatory.info/ ********************************************** * Attend the 11th Annual NEBRASKA STAR PARTY * * July 18-23, 2004, Merritt Reservoir * * http://www.NebraskaStarParty.org * ********************************************** |
#9
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Charles wrote:
A "rich field" refractor is a refrector that has a focal ratio of f/5 and lower. Focal ratio is the Focal Length divided by the the aperture. For example, a scope with a 1000mm focal length (FL) and a 254mm (10") aperture, has a focal ratio of 4 (3.93 really), written as f/4. Well, there probably isn't a specific f/ratio cutoff point for a refractor to be termed "rich-field". The term can also apply to a 2-element refractor like Orion's 100mm f/6. It provides good wide-field performance, but not as good high-power performance as a long f/ratio "planetary" refractor. Thus, this characteristic shows the instrument is best considered a wide-field "RFT" rather than a planetary refractor or an "all-purpose" instrument like an Apochromat. Clear skies to you. -- David W. Knisely Prairie Astronomy Club: http://www.prairieastronomyclub.org Hyde Memorial Observatory: http://www.hydeobservatory.info/ ********************************************** * Attend the 11th Annual NEBRASKA STAR PARTY * * July 18-23, 2004, Merritt Reservoir * * http://www.NebraskaStarParty.org * ********************************************** |
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