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General Astronomy >> Beginners Forum

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MawkHawk
sage
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Reged: 08/23/09

Loc: SE Michigan, USA
Re: Telrad question new [Re: ensign]
      #5636721 - 01/22/13 11:47 AM

I do have a Telrad and a RA finder but I prefer a straight thru finder. Keep both eyes open with 1 eye at the finder and the other eye to "guide" you. A Telrad helps me only somewhat, mostly because I have not taken time to learn how to use it properly. A right angle finder alone on a scope is a crime against humanity, IMO. I would either replace it with a straight thru finder or add a Telrad.

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Tony Flanders
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Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: Telrad question new [Re: Jon Isaacs]
      #5636785 - 01/22/13 12:24 PM

Quote:

When using a straight-through finder, you are looking in the direction the scope is pointing, this is much more intuitive.




Not for me. If anything, I find the RA finder more intuitive because I look down into it at the same angle that I look down into the main eyepiece -- and down at my charts, too.

Mind you, I have no trouble at all using straight-through finders as far as matching them up with my charts is concerned. And they certainly have the virtue of eliminating the need for a unit-power finder to get the initial fix on the sky.

However, any way you slice it, looking upward through a telescope requires a certain degree of contortion, especially when the scope is pointed high in the sky. There's a reason that almost everyone in the U.S. who owns a refractor or SCT uses a star diagonal!

I don't mind the contortion for getting a quick fix, as when looking through a Telrad, or sighting on a planet with a straight-through finderscope. But when working out a complex multi-minute starhop to a target that's not directly visible in the finderscope, I find the (literal) pain in the neck entailed in using a straight-through finderscope to be a major obstacle to mental concentration.

That's why my favorite combination, assuming no other constraints, is a Telrad plus a right-angle correct-image finderscope.


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panhard
It's All Good
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Reged: 01/20/08

Loc: Markham Ontario Canada
Re: Telrad question new [Re: Tony Flanders]
      #5636794 - 01/22/13 12:28 PM

I am with you on that one Tony.

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SteveG
Post Laureate
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Reged: 09/27/06

Loc: Seattle, WA
Re: Telrad question new [Re: panhard]
      #5636806 - 01/22/13 12:34 PM

I use a green laser exclusively, but I've kept my Telrad for star parties. My smaller scopes have RDF's but I use the laser on all of them (fits a standard finder shoe). From there it's straight to a low-power eyepiece. I've given up completely on optical finder scopes.

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csrlice12
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Reged: 05/22/12

Loc: Denver, CO
Re: Telrad question new [Re: SteveG]
      #5636829 - 01/22/13 12:46 PM

Who's gonna come out with a finderscope where the "eyepiece" can flip up to become either right angle or straight thru?????

I love the Telrad, especially in dark skies. It will get you "very close", at the very least, the object will be in your finderscopes FOV. That being said, in heavy light pollution, you won't use it. But with even some darkness, it is useable and I would not want to be without one at the dark site. Oddly enough, I moved my straight thru finder from my refractor as I've found I prefer the RACI on the refracor--and actually finding out I like the straight thru on the dob--I seem to find it easier to use. However, if something is high in the sky, the RACI would still be best as I'm getting too old to play Twister anymore.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Telrad question new [Re: Tony Flanders]
      #5636844 - 01/22/13 12:53 PM

Quote:


However, any way you slice it, looking upward through a telescope requires a certain degree of contortion, especially when the scope is pointed high in the sky. There's a reason that almost everyone in the U.S. who owns a refractor or SCT uses a star diagonal!




There is no doubt that a star diagonal is nearly as necessity with a refractor or SCT, the eyepiece is at the bottom of the scope so straight through viewing is very awkward. But a Newtonian finder is at the sky end of the scope so it is not such an issue.

The irony:

The Right Angle Finder forces the use of a Telrad which is a Straight Through Finder. If a straight through finder is awkward and uncomfortable, the Telrad is equally so.

For me, the keys to using any finder comfortably, in particular a straight through finder, are an easily adjustable chair that allows me to set the seat height where I want it, and placement of the finder of the OTA. I generally place the Telrad and the magnifying finder side by side so I can easily switch between them. But finding that right place, it is not necessarily easy, a few inches make a big difference. To use it, I just position the seat, lean over and look through the eyepiece, looking directly at my target. It wouldn't seem to require a contortionist, there are not too many 220 lbs 6 foot tall contortionists, particularly ones who are 64 years old...

Jon

Edited by Jon Isaacs (01/22/13 01:01 PM)


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kenrenard
Carpal Tunnel


Reged: 12/13/12

Loc: Dunmore, PA
Re: Telrad question new [Re: Jon Isaacs]
      #5636857 - 01/22/13 12:57 PM

I own a Telrad and never knew much about it. I do love the simplicity of it. After reading this post I looked at the Telrad charts and came across some history. See the cloudy night post below. Interesting read!


http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3026880/page...


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Tony Flanders
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Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: Telrad question new [Re: Jon Isaacs]
      #5636936 - 01/22/13 01:42 PM

Quote:

If a straight through finder is awkward and uncomfortable, the Telrad is equally so.




No, I don't agree at all.

The difference is eye relief. With a finderscope, you need to press your eye right up against the eyepiece. With a Telrad, you can have your eye close to the Telrad, six inches back, or even six feet back. That extra degree of freedom makes a huge difference as far as comfort is concerned.

I do know some people who use rifle scopes, which tend to have much longer eye relief than conventional astro finderscopes. But still nothing like Telrads.


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csrlice12
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Reged: 05/22/12

Loc: Denver, CO
Re: Telrad question new [Re: Tony Flanders]
      #5636987 - 01/22/13 02:09 PM

"there are not too many 220 lbs 6 foot tall contortionists, particularly ones who are 64 years old..."

and there are countless 220lb barely over 5'6" 64yo's who already have problems bending over (did lose a lot of the weight though in the last year, now down to 165 aunaturale.)

Looking thru scopes is a lot of work (fun, but work). That being said, who knew "Twister" was an astronomy prep class..........and why did I not get college credit??


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neotesla
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Reged: 11/18/10

Loc: Canada
Re: Telrad question new [Re: csrlice12]
      #5637061 - 01/22/13 02:38 PM

I have Telrads on our SCT's, and an invaluable attachment is the mirror/dew cover. Keeps the dew off when in one position, flip it open and use the mirror for viewing without contortion.

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Mike4242
Pooh-Bah


Reged: 11/02/11

Loc: Memphis, TN
Re: Telrad question new [Re: neotesla]
      #5637064 - 01/22/13 02:40 PM

Quote:

invaluable attachment is the mirror/dew cover. Keeps the dew off when in one position, flip it open and use the mirror for viewing without contortion.




Very true. They dew up fast -- I just cover mine with a plastic ziploc bag when it's not in use.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Telrad question new [Re: Tony Flanders]
      #5637072 - 01/22/13 02:45 PM

Quote:



The difference is eye relief. With a finderscope, you need to press your eye right up against the eyepiece. With a Telrad, you can have your eye close to the Telrad, six inches back, or even six feet back. That extra degree of freedom makes a huge difference as far as comfort is concerned.




Tony:

As I tried to stress in my previous post, when using a finder, in particular a straight through finder, the placement on the OTA is important. Just a few inches can be the difference between a comfortable, easy to use finder and an awkward, unpleasant experience. When I was finishing up my 16 inch, what took it to the next level was moving the finders, it was a small change, maybe 6 inches closer to the focuser but the difference transformed the experience. I think often finders are just put where they are most easily put, not put in the place that makes them most usable.

A good quality adjustable observing chair is also important. A typical straight through finder has about 15mm of eye relief, sufficient for comfort but there is not a lot of freedom there. An observing chair such as the Starbound, provides that degree of freedom that you attribute to the Telrad.

Positioning is best done by trial and error but I find that if the finders are close to the focuser and maybe just a few inches closer to the mirror end, changing the seat height is often not necessary.

That said, certainly RACI finders have their advantages and the fact that the eyepiece be an easy distance from the main scope's eyepiece is handy. My point is that a straight through finder can be used in relative comfort.

Jon

Edited by Jon Isaacs (01/22/13 02:52 PM)


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lamplight
Carpal Tunnel
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Reged: 09/18/12

Loc: western MA, U.S.
Re: Telrad question new [Re: csrlice12]
      #5637286 - 01/22/13 04:26 PM

Quote:

Who's gonna come out with a finderscope where the "eyepiece" can flip up to become either right angle or straight thru?????




You ask, they make :
Stellarvue 60mm finders

I have the 60mm raci on my SCT and just bought the straight through version for my DOB , appears I can swap the EP's.

Or get the raci and the $50 straight through replacement. Oooh.


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