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Equipment Discussions >> Equipment

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sin
member


Reged: 09/01/10

Loc: Toronto, Canada
Finderscope or telrad
      #5692705 - 02/21/13 01:00 PM

Hi,

Iíve been using my Orion XT6 with the supplied red-dot finder but I would like to upgrade to something better.
Red-dot is good for bright objects that are easy to find but with anything else itís just frustration.

I did some research and my alternatives are a 9x50 finder-scope or Telrad.
What do you think would be a better alternative?

Telrad is cheaper than a good finder-scope but then again itís just a variant of the red-dot finder. What do you use more often?


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David Knisely
Postmaster
*****

Reged: 04/19/04

Loc: southeastern Nebraska
Re: Finderscope or telrad new [Re: sin]
      #5692801 - 02/21/13 01:47 PM

Quote:

Hi,

Iíve been using my Orion XT6 with the supplied red-dot finder but I would like to upgrade to something better.
Red-dot is good for bright objects that are easy to find but with anything else itís just frustration.

I did some research and my alternatives are a 9x50 finder-scope or Telrad.
What do you think would be a better alternative?

Telrad is cheaper than a good finder-scope but then again itís just a variant of the red-dot finder. What do you use more often?




Get BOTH a Telrad and an optical finderscope. As for the Telrad being a variant of the red-dot finder, that is incorrect. The Telrad is one of the best known commercial finders. It is a reflex-type finder which puts an unique three-ring reticle of adjustable brightness in the viewer's field. These rings are 0.5 degrees, 2 degrees, and 4 degrees in diameter on the sky, and are most useful, not just as a simple bulls-eye, but as a "pattern maker", for star hopping. By using overlays which resemble the Telrad's reticle pattern on star atlases, and centering the target object's chart location in the overlay, star patterns and alignments with the Telrad rings in the area around deep-sky objects can be worked out which can then be duplicated by looking through the Telrad at the night sky. The Telrad rings can also be used as measured "steps" in extended star hops. This can make finding even faint non-naked eye objects much easier than with the simple "dot" finders. Those people who insist on downplaying the Telrad's usefulness based on merely using the unit only as a "bull's-eye" centering finder like the "dot" sights do not really understand how to use a Telrad! It is the pattern making or stepping-off field size which makes it a truly valuable finding device for the telescope. Indeed, I have both on my 14 inch Newtonian and use the Telrad about as much as I do my 9x50 RACI finderscope. Some people with really large Dobsonians even get away with *only* a Telrad as their finder, which shows just how valuable they really can be. Clear skies to you.

Clear skies to you.


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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: Finderscope or telrad new [Re: David Knisely]
      #5692825 - 02/21/13 02:00 PM

My Telrad gets me in the ballpark, my finderscope shows me home plate.......

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drbyyz
sage
**

Reged: 11/04/12

Re: Finderscope or telrad new [Re: csrlice12]
      #5692834 - 02/21/13 02:06 PM

Quote:

My Telrad gets me in the ballpark, my finderscope shows me home plate.......




Pretty much how I use mine as well. Gets me to a nearby bright star very easily and quickly and no questions about whether I have the right one in the finder or not. Then the finder or large EP takes it from there. I'm also learning to use it in the way Dave spoke of for starhopping, etc. I use the SkySafari app and it will overlay Telrad circles onto the map for you, pretty cool and useful.


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wirenut
Pooh-Bah


Reged: 09/21/06

Loc: m'dale Pa
Re: Finderscope or telrad new [Re: csrlice12]
      #5692869 - 02/21/13 02:30 PM

Rigel's quick finder is a good option too instead of a telrad. they are a little smaller and can be a better fit for a small scope. I have a telrad and 50mm optical straight finder but never use the optical finder it's a pain to use on a dob. what I do is use a low power wide field EP to zero in on my target.

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sin
member


Reged: 09/01/10

Loc: Toronto, Canada
Re: Finderscope or telrad new [Re: wirenut]
      #5693027 - 02/21/13 04:08 PM

Thank you for your replies.

Iíve seen that they have a variant of the finderscopes with illuminated cross-hair. They are somewhat more expensive. Do you think itís worth it?


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mitaccio
professor emeritus
*****

Reged: 03/17/09

Loc: Oahu, Hawaii
Re: Finderscope or telrad new [Re: sin]
      #5693139 - 02/21/13 05:04 PM

I recently purchased the Stellarvue F60 finderscope. I think it was the best purchase I have made (besides my scope). I use it like has been said before "to find home plate" along with my telrad. Works with my 1.25" eyepieces and allows for various magnifications (within reason) and also makes a great low power telescope.

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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Finderscope or telrad new [Re: csrlice12]
      #5693140 - 02/21/13 05:04 PM

Quote:

My Telrad gets me in the ballpark, my finderscope shows me home plate.......




The value of the Telrad depends on the darkness of the sky. If the skies are dark and clear, then for most objects in most telescopes, a Telrad will do the job, not only get me up to the plate, but around the bases to score.

If light pollution is considerable, can't see the Milky Way, then a Telrad alone won't cut it and a magnifying finder is more useful.

For an XT-6, balance is going to be a problem. I use straight through finders on my Newtonians, I am looking in the direction the scope is pointing, I can find my initial guide star by keeping both eyes open and looking through the finder.

Jon

Edited by Jon Isaacs (02/21/13 05:34 PM)


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Gary Riley
sage


Reged: 12/01/11

Loc: White Bluff, TN
Re: Finderscope or telrad new [Re: Jon Isaacs]
      #5693149 - 02/21/13 05:09 PM

+1 for using both a finder scope AND Telrad.

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DonsDob
member
*****

Reged: 05/21/12

Loc: CT
Re: Finderscope or telrad new [Re: Gary Riley]
      #5693210 - 02/21/13 05:42 PM

Another + for both the finder and either a telrad or rigel. I have a 9x50 RACI finder and a telrad on the XT8i. The telrad can be a little awkward sighting along the tube. I recently purchased the 2" riser for it but have not yet had a chance to try it out. Be sure to align both the finder and the reflex sight with the main scope.

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sin
member


Reged: 09/01/10

Loc: Toronto, Canada
Re: Finderscope or telrad new [Re: David Knisely]
      #5693333 - 02/21/13 07:03 PM

Quote:


Get BOTH a Telrad and an optical finderscope. As for the Telrad being a variant of the red-dot finder, that is incorrect. The Telrad is one of the best known commercial finders. It is a reflex-type finder which puts an unique three-ring reticle of adjustable brightness in the viewer's field. These rings are 0.5 degrees, 2 degrees, and 4 degrees in diameter on the sky, and are most useful, not just as a simple bulls-eye, but as a "pattern maker", for star hopping.




Sorry, but I don't get it with degrees in diameter on the sky. Doesn't that depend how far back you are behind the Telrad? If your eye is closer you will see bigger part of the sky through the same cicrcle. Or am I missing something?


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sin
member


Reged: 09/01/10

Loc: Toronto, Canada
Re: Finderscope or telrad new [Re: Jon Isaacs]
      #5693341 - 02/21/13 07:07 PM

Quote:

The value of the Telrad depends on the darkness of the sky. If the skies are dark and clear, then for most objects in most telescopes, a Telrad will do the job, not only get me up to the plate, but around the bases to score.

If light pollution is considerable, can't see the Milky Way, then a Telrad alone won't cut it and a magnifying finder is more useful.





I think that's a good point. Night sky around Toronto is quite washed out.


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Finderscope or telrad new [Re: sin]
      #5693353 - 02/21/13 07:12 PM

Quote:


Sorry, but I don't get it with degrees in diameter on the sky. Doesn't that depend how far back you are behind the Telrad? If your eye is closer you will see bigger part of the sky through the same cicrcle. Or am I missing something?




I am not quite sure why it works the way it does but diameter of the Telrad Circles is independent of how far from the finder you are. With a tall scope that requires a ladder, the observer might be standing on the ground and the Telrad might be up next to the focuser, 3 or 4 feet away.

Jon


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sin
member


Reged: 09/01/10

Loc: Toronto, Canada
Re: Finderscope or telrad new [Re: Jon Isaacs]
      #5693364 - 02/21/13 07:18 PM

That is strange. I'll have to look it up.

Thank you.


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csrlice12
Postmaster
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Reged: 05/22/12

Loc: Denver, CO
Re: Finderscope or telrad new [Re: sin]
      #5693440 - 02/21/13 08:00 PM

Weird as it sounds, that's the way it is......

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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Finderscope or telrad new [Re: sin]
      #5693766 - 02/21/13 11:23 PM

Quote:

That is strange. I'll have to look it up.

Thank you.




It is strange. While it seems you are looking at a reticule projected on the sky, what you are really doing is looking at an image of an optical system focused on the reticule. It is like looking through a telescope, the size of the image, the magnification, does not change just because you are further from the eyepiece.

Jon


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David Knisely
Postmaster
*****

Reged: 04/19/04

Loc: southeastern Nebraska
Re: Finderscope or telrad new [Re: sin]
      #5693893 - 02/22/13 01:15 AM Attachment (29 downloads)

Quote:

Quote:


Get BOTH a Telrad and an optical finderscope. As for the Telrad being a variant of the red-dot finder, that is incorrect. The Telrad is one of the best known commercial finders. It is a reflex-type finder which puts an unique three-ring reticle of adjustable brightness in the viewer's field. These rings are 0.5 degrees, 2 degrees, and 4 degrees in diameter on the sky, and are most useful, not just as a simple bulls-eye, but as a "pattern maker", for star hopping.




Sorry, but I don't get it with degrees in diameter on the sky. Doesn't that depend how far back you are behind the Telrad? If your eye is closer you will see bigger part of the sky through the same cicrcle. Or am I missing something?




Nope, the reticle is basically projected as an image at infinity by a lens inside the Telrad system, so it appears on the sky with the rings having a 0.5, 2, and 4 degree field diameter no matter how far back or how close your eye is to the glass plate. It is like a "heads-up" display for your finder. Below is how I find the faint 12th magnitude core galaxy NGC 1272 near the center of the great Perseus Galaxy Cluster using *only* the Telrad and stars in the area down to about 5th magnitude:


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David Knisely
Postmaster
*****

Reged: 04/19/04

Loc: southeastern Nebraska
Re: Finderscope or telrad new [Re: Gary Riley]
      #5693904 - 02/22/13 01:27 AM Attachment (60 downloads)

Here is the setup on the upper tube assembly of my 14 inch f/4.6 Dobsonian. The optical finderscope is an Orion 9x50 Right-angle Correct Image (RACI), and is mounted on a dovetail mount next to the Telrad which has an Astrosystems orange plexiglass dew shield on it:

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sin
member


Reged: 09/01/10

Loc: Toronto, Canada
Re: Finderscope or telrad new [Re: David Knisely]
      #5694086 - 02/22/13 06:54 AM

Quote:

Here is the setup on the upper tube assembly of my 14 inch f/4.6 Dobsonian. The optical finderscope is an Orion 9x50 Right-angle Correct Image (RACI), and is mounted on a dovetail mount next to the Telrad which has an Astrosystems orange plexiglass dew shield on it:




Wow, that looks cool. My XT6 looks like a dwarf compared to it.
Thank you for your explanation of the Telrad. I didn't know it's such an advanced contraption
That 9x50 RACI is quite big. It's comparabale in size with Telrad.


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fishuntime53
journeyman
*****

Reged: 09/14/12

Loc: Missouri
Re: Finderscope or telrad [Re: sin]
      #5714696 - 03/05/13 03:27 PM

I have an 11" SCT with Celestron's standard 9x50 finder. I would like to replace this finder with a 'straight-thru' similar to the Stellarvue F50 to give me a real focuser and enabling me to use 1.25" eyepieces. What do readers suggest?

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