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Equipment Discussions >> Refractors

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DRodrigues
super member


Reged: 08/08/11

Re: image erectors new [Re: SteveSMS]
      #5756838 - 03/25/13 07:10 PM

45º prisms are ok for low power viewing. If you want >70x you should get a Vixen erector lens or a Nikon FSA-L2 - have a look at http://www.pt-ducks.com/cr-telescopes.htm#Test%20of%20image%20erectors
I use my TMB92 for birding but I'm not an astro fellow - just an occasional one...


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ScottAz
Fleet Navigator
*****

Reged: 02/06/05

Loc: Kenosha, Wisconsin
Re: Who uses an apo for birding and astro? new [Re: SteveSMS]
      #5756863 - 03/25/13 07:30 PM

Nice red tailed hawk, Steve!

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azure1961p
Postmaster
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Reged: 01/17/09

Loc: USA
Re: Who uses an apo for birding and astro? new [Re: Lane]
      #5756947 - 03/25/13 08:16 PM

Quote:


The reason you don't want to use a 45 degree diagonal is because most if not all of them will noticeably degrade the image. For terrestrial use I think you are ok




Very true and what's funny is the birding/spotting camp in reviews and forums have made claims that no other group of observers is more discriminating of optics than they - lol - yes as they gaze through their amici's. I've tried a couple times here and there to sway them away and mentioned astronomy and do on and I was written off as naive.

Pete


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curiosidad
sage


Reged: 06/09/11

Re: Who uses an apo for birding and astro? new [Re: SteveSMS]
      #5757585 - 03/26/13 07:15 AM

Fabulous shot!!

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Mark Harry
Vendor
*****

Reged: 09/05/05

Loc: Northeast USA
Re: Who uses an apo for birding and astro? new [Re: curiosidad]
      #5757598 - 03/26/13 07:24 AM Attachment (32 downloads)

I use this for terrestrial, limited astro, and wildlife. Can even follow airliners handheld. Cheap, 80X700 achro; homemade OTA that's very well corrected.
M.


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Who uses an apo for birding and astro? new [Re: MAURITS]
      #5757717 - 03/26/13 08:52 AM

Quote:

Maybe off topic, but why are there so little " 45° erecting prisma's" used for astronomy viewing?

I believe the view's are not upside down, is this the better way to go, or I am wrong?




A standard star diagonal erects the image, it is reversed left-right. 45 degree prism have a complicated light path, actual there are two paths and at high powers this invariable results in obvious aberrations. Also, the clear aperture of the prism is another issue..

I use a star diagonal night and day.

Jon


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Whoapiglet
member


Reged: 08/07/12

Loc: Denver
Re: Who uses an apo for birding and astro? new [Re: Jon Isaacs]
      #5762489 - 03/28/13 02:14 PM

Just a thought... IF you were considering a 72mm ED scope AND a 102 for astro, you might look at the celestron regal 80 F-ED spotter. I have one, and the optics are very nice. probably FPL-51 or similar. its an 80mm ED spotter that accepts most 1.25 astro eyepieces.

I brought mine down to Mexico a few weeks ago wrapped in some clothes in my carry on- its armored and waterproof, so no case needed.

they run less than $500 with a decent 20-60x zoom lens, I brought along a 13mm nagler and a 5mm TMB and had a ball. just used a manfrotto tripod and it was just fine for scanning around. weird seeing everything "backwards"

certainly a 80-90 APO with a diagonal and heavier mount would be a nicer picture (mostly due to the extra prisms vs diagonal), but for a good mix of spotting scope and astro scope it worked well. and probably on par with a 70mm ED astro scope.

one down side is low power wide views like a 24 panoptic vignette on the prisms.

Ed


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DRodrigues
super member


Reged: 08/08/11

Re: Who uses an apo for birding and astro? new [Re: Whoapiglet]
      #5762873 - 03/28/13 06:18 PM

If money isn't a problem the Kowa LensScope and the Swarosvky 95mm module of the new X system might be interesting. I'm trying to test the Swaro but still didn't...
The advantages of these system are internal focus, low weight and dedicated erector systems. The Swaro X system has the advantage of weather proof of the objective module but don't know if CA is at the level of a Apo triplet... Is on my wish to test list...


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Who uses an apo for birding and astro? new [Re: DRodrigues]
      #5763172 - 03/28/13 08:54 PM

Quote:


The advantages of these system are internal focus, low weight and dedicated erector systems.




Do you consider these advantages? They can be for birding, probably not for astro. The biggest disadvantage I see to birding scopes, they are limited to 1.25 inch eyepieces. The thing an 80mm does best is provide widefield views that a larger scope cannot.

Jon


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OldManInHawaii
member


Reged: 03/12/12

Re: Who uses an apo for birding and astro? new [Re: Jon Isaacs]
      #5763505 - 03/29/13 01:17 AM

I bought my ES ED102 APO partly with the intention of terrestrial & astronomical use, but ended up using it only for astronomical use. We have migratory whales here but it was hard to spot them with even binoculars. And there are wild cockatoos & green parrots which fly between the tall trees where I live, but they are too quick to even spot visually. Perhaps I'm not alert enough, or maybe my eyes aren't keen enough, or maybe my reflexes are just too slow...whatever.

In any case, I'm glad I bought this ES scope vs. the Celestron Regal 100mm ED spotting scope because it's better suited for astronomical use.


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KWB
Postmaster
*****

Reged: 09/30/06

Loc: Westminster,Co Elev.5400 feet
Re: Who uses an apo for birding and astro? new [Re: OldManInHawaii]
      #5763549 - 03/29/13 02:15 AM

For me when choosing a dual purpose ED scope, a must have is the capability of using a 2 inch,90° star diagonal for astronomical use. This is an invaluable asset IME,for maximum TFOV capability and viewing comfort. No stiff neck viewing when viewing high in the sky as opposed to using a setup with a 45° diagonal and sometimes being on my knees trying to locate a celestial object.

This same configuration works perfectly well for me when it comes to viewing wildlife. I dislike a correct image diagonal for celestial viewing as per the above mentioned reasons,and could care less which direction a bird is "facing" when I'm viewing it in terrestial observation.


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JKoelman
professor emeritus


Reged: 05/16/11

Loc: Bangalore, India
Re: Who uses an apo for birding and astro? new [Re: KWB]
      #5763719 - 03/29/13 06:24 AM

Quote:

I dislike a correct image diagonal for celestial viewing as per the above mentioned reasons,and could care less which direction a bird is "facing" when I'm viewing it in terrestial observation.



It is a bit counterintuitive though, to have to steer your scope to the left when the bird is flying to the right.


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Who uses an apo for birding and astro? new [Re: JKoelman]
      #5763791 - 03/29/13 07:55 AM

Quote:

Quote:

I dislike a correct image diagonal for celestial viewing as per the above mentioned reasons,and could care less which direction a bird is "facing" when I'm viewing it in terrestial observation.



It is a bit counterintuitive though, to have to steer your scope to the left when the bird is flying to the right.




At first it's probably counter-intuitive but if one is used to the left-right reversal, it soon becomes intuitive and the "correct image" is confusing.

One thing to consider, with a scope, you are usually pushing the back of the scope, not the front. With Binoculars you move the front of the binos left to follow a bird moving to your left.

In a scope, a bird that is moving to the left appears to be moving to the right. If you move the back of the scope to the right to follow the bird, the scope will actually be moving to the left, just like the bird.

With both the binos and the scope, you move in the left-right direction that the bird appears to be flying. Up-down, that's a different story.

Jon


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DRodrigues
super member


Reged: 08/08/11

Re: Who uses an apo for birding and astro? new [Re: Jon Isaacs]
      #5763984 - 03/29/13 09:25 AM

Quote:

Quote:


The advantages of these system are internal focus, low weight and dedicated erector systems.




Do you consider these advantages? They can be for birding, probably not for astro. The biggest disadvantage I see to birding scopes, they are limited to 1.25 inch eyepieces. The thing an 80mm does best is provide widefield views that a larger scope cannot.
Jon




Jon,
Yes, these are more important for birding but the first 2 are also useful for astro use.
With the Kowa LensScope you can use 2" eyepieces for astro use. For birding my Nikon FSA-L2/Ethos combo should work directly if you have the version for Nikon cameras...
My Swaro option interest is larger aperture, lower weight, weather proof and lower cost (at least in Europe). Still don't know if it will vignette with 2" since still didn't test one and it's design is only for birding...


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Who uses an apo for birding and astro? new [Re: DRodrigues]
      #5764140 - 03/29/13 10:28 AM

Why do you consider internal focus an advantage for astro? The ones I have used are slower than a good rack and pinion with a two speed.

It would have to have very large prisms to avoid vignetting with an eyepiece like the 31 mm Nagler. Balance and mounting are issues too when using those big, well corrected eye pieces.

Jon


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aa6ww
scholastic sledgehammer
*****

Reged: 10/23/11

Loc: Sacramento, Calif.
Re: Who uses an apo for birding and astro? new [Re: SteveSMS]
      #5768015 - 03/31/13 01:51 AM Attachment (8 downloads)

Ive been using my TV-85 with a William Optics 2" erect imaging diagonal. Its very sweet and very light weight, and the lens on the TV are very crisp and lack chromatic aberration when you look at tree edges against the sunlight and bright objects.
Ive tried my TSA-102 a few times but the sweet size of the TV-85 is really ideal for birding even at long distances till the heat waves take over.
Ive also tried my Orion 100mm F/6 but the TV wins because of the better glass.

...Ralph


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DRodrigues
super member


Reged: 08/08/11

Re: Who uses an apo for birding and astro? new [Re: Jon Isaacs]
      #5769361 - 03/31/13 05:53 PM

Quote:

Why do you consider internal focus an advantage for astro? The ones I have used are slower than a good rack and pinion with a two speed.



I consider it an advantage in terms of comfort, although It depends on your observation habits and material... In my case I observe with my glasses resting on the eye-piece and when I zoom my bino combo http://www.pt-ducks.com/cr-telescopes.htm#CR-binoviewing I have to move my head - those that use Denk power-switch or Siebert PMW, know what I mean - again in my case, from low to high zoom limits with the bino combo I need almost 50mm focus travel.

Quote:


It would have to have very large prisms to avoid vignetting with an eyepiece like the 31 mm Nagler. Balance and mounting are issues too when using those big, well corrected eye pieces.
Jon




If you had followed my previous Nikon FSA-L2 link you would noticed that it works with the UWA 2" 30mm without vignetting. By the way, it uses lenses instead of prisms - results longer but allows >3x zoom factor
After your comment I remembered to add the Celestron Axion 31 contact info on the http://www.pt-ducks.com/cr-telescopes.htm#Test%20of%2082%C2%BA,%20100%C2%BA%20and%20102%C2%BA%20AFOV%20zooms - note that the ES82 30mm didn't work well with my combo.

You are right when mentioning that balance and mounting issues appear with these large eps but is doable although I would prefer a much shorter combo...


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