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Rich Field Refractor?



 
 
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  #1  
Old November 13th 03, 09:13 PM
Alan Buttivant
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Default Rich Field Refractor?

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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  #2  
Old November 13th 03, 10:17 PM
Llanzlan Klazmon The 15th
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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.
  #3  
Old November 14th 03, 10:15 AM
Joseph Schmosovich
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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  
Old November 15th 03, 07:27 PM
Chain Rule
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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...




  #5  
Old November 15th 03, 09:36 PM
Alan Buttivant
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Default

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




  #6  
Old November 15th 03, 10:39 PM
Chain Rule
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Posts: n/a
Default


"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,




  #7  
Old November 17th 03, 02:46 AM
RingPlane
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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




  #8  
Old November 17th 03, 05:28 AM
David Knisely
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Default

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  
Old November 17th 03, 05:32 AM
David Knisely
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Default

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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