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Thread: Just for fun.... Telescope test

  1. #1
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    Default Just for fun.... Telescope test

    Finally got a set of T adapter and T mount to couple my D1X to ETX90 telescope. Here are some shots with increasing focal length to demonstrate the magnification power of a telescope. I started with standard SLR lenses from 24mm to 200mm, and then mounted the camera to the telescope for the last shot.

    1. 24mm (36mm equivalent due to 1.5x cropping factor on D1X)

    The red arrow points to an air vent on the roof of the house behind the slope. That is the subject that I will be zooming in on:



    2. 50mm (75mm equiv)



    3. 85mm (127mm equiv)



    4. 200mm (300mm equiv)




    And finally...
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    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

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    5. 1250mm (1875mm equiv)



    All pictures have been processed slightly in PS (levels, USM, resize), but not cropped.

    Hope you have enjoyed viewing this.

    Thanks!

    Roy
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

  3. #3

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    WOW! Image quality is still rather good at full tele. This would make a good voyeur's tool....

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    Quote Originally Posted by Zerstorer
    WOW! Image quality is still rather good at full tele. This would make a good voyeur's tool....


    By the way this is the setup:

    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

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    Whats the effective aperture? Seems to be quite attractive for doing sports.

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    Wow indeed!

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    Amazing.......

    Did you use a diagonal with the setup, or is the T-adaptor meant to be right angle from the axis?

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    beautiful...no CA somemore
    We are HDD of PC & FT are MB add to storage;
    so PC never hangs with enormous storage capacity - LKY

  9. #9

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    cool...
    Is there any min focusing distance? I have check the internet and it is about 100USD only. Wow nice alternative for zoom lens!

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    Quote Originally Posted by MoriMori
    Whats the effective aperture? Seems to be quite attractive for doing sports.
    The focal length of the ETX90 is 1250mm.
    The diameter of the Primary mirror is 90mm.

    So the theoretical aperture should be 1250/90 = f/13.8.

    The effective aperture might be smaller (larger f number) because of obstruction caused by the secondary mirror. Furthermore, the 1.25 inch mounting might have further reduced the effective aperture, because I notice some slight vignetting.

    I don't think this setup will be useful for sports because you will have a hard time tracking the moving players. I believe it is more suitable for wildlife and astrophotography.
    Last edited by roygoh; 17th August 2003 at 03:56 PM.
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    Quote Originally Posted by frisky
    Amazing.......

    Did you use a diagonal with the setup, or is the T-adaptor meant to be right angle from the axis?
    The ETX series telescopes have a flip mirror system. So the diagonal is essentialy built into the scope. I could have bought the dedicated T-adaptor from Meade that threads into the rear port so that the camera will be in line with the scope, and I just need to flip the mirror out of the way to shoot in that mode.

    However, I bought a standard T-adaptor, so I have to use it via the 90 degree port for eyepiece mounting. This arrangement, though looks a little strange, is actually better for both astro and terrestrial photography because it is easier to view into the camera's viewfinder.
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

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    Quote Originally Posted by Azure
    Wow indeed!
    Quote Originally Posted by Wai
    beautiful...no CA somemore

    Thanks!
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

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    Quote Originally Posted by E-Lim
    cool...
    Is there any min focusing distance? I have check the internet and it is about 100USD only. Wow nice alternative for zoom lens!
    I am pretty sure it can focus down to shorter than 20 feet, but I am not sure where is the actual limit. If you look at my setup you will notice that I have included the extension tube of the T-adapter. This works like a normal SLR extension tube by extending the total optical track to reduce the minimum focus distance.

    When using a telescope as a camera lens, you will not get any zoom and the aperture is fixed. It just work like a prime super-telephoto lens.

    100USD? That's a very good price. I got mine a year ago for 179USD. Where did you find that price from?
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

  14. #14

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    oops, my bad I was looking at the hardcase for ETX90. You are right it's 179USD http://www.buytelescopes.com/product.asp?pid=5158
    How does the focusing works with this setup. AF/MF?

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    if u use afocal coupling, the magnification is even higher

    E-Lim, u definitely need to use MF, there are also tricks like cut out 3 holes on the scope cover, so that when these 3 holes merged together, the object is in focus. but even i use afocal coupling, i still prefer to use MF + view the photo at 100% with a laptop for best accuracy, of cos a good focuser will helps a lot too.
    Last edited by Wai; 17th August 2003 at 05:52 PM.

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    Quote Originally Posted by roygoh
    However, I bought a standard T-adaptor, so I have to use it via the 90 degree port for eyepiece mounting. This arrangement, though looks a little strange, is actually better for both astro and terrestrial photography because it is easier to view into the camera's viewfinder.
    no point to get the flip mirror system, in the end u still need to focus thru the viewfinder...best is to get a secondary scope and mount on the main scope...one for photography and one for viewing + tracking

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    Quote Originally Posted by roygoh
    100USD? That's a very good price. I got mine a year ago for 179USD. Where did you find that price from?
    I believe that is excluding shipping?
    How much did the shipping adds up to?

    I saw the ads mentions a building RA motor drive.
    Are you able to put it into use for tracking purpose?

    Also this scope uses 1.25" eyepiece?

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    power sia....

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    Quote Originally Posted by frisky
    I believe that is excluding shipping?
    How much did the shipping adds up to?

    I saw the ads mentions a building RA motor drive.
    Are you able to put it into use for tracking purpose?

    Also this scope uses 1.25" eyepiece?
    Yes, $179 does not include shipping. I remember vaguely that the shipping cost was $10 for within USA, and I am not sure if that shop ships overseas (www.sightandsoundshop.com). THey are selling the same scope for $169 now.

    The reason for the very low price is because this scope has been discontinued by Meade. It is the "RA" version, so it cannot be upgraded to electronic control (EC) and the AutoStar controller with Goto function.

    I have not used the RA motor for tracking before, as I have been mainly shooting the moon since I got the scope.

    And finally, yes, it uses 1.25" eyepiece.
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

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    Quote Originally Posted by Wai
    no point to get the flip mirror system, in the end u still need to focus thru the viewfinder...best is to get a secondary scope and mount on the main scope...one for photography and one for viewing + tracking
    Well so far I have been shooting the moon only, so the miserable little finder scope has been quite OK, and I have not tried the tracking function yet.

    I actually have the parts to build a small scope to couple to the ETX90 but have not got the time to actually build it.
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

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