Using High End Telescope for lens.

Hello all!

Just had the lens (EF 800mm f/5.6L IS) loaned out to me. I'm currently testing it against a few lenses.

One lens combo that is popular would be the 600/4L IS + 1.4x for a little over 800mm. The 800 f/5.6L EF IS showed MUCH MUCH better color correction than the 600/4L EF IS + 1.4x combo, and not by a small amount either!

I didn't get a chance to do a 2x + 400 2.8L EF IS combo. They didn't have one in the shop to try out.

Something that did disappoint me though - when shooting a Great Egret against a dark background, the egret (which is white) showed a good amount of CA wide open. This is not acceptable for a 12,000 dollar lens. I'll try the test again, but it's in focus and I'm still getting CA.

The only two optics that I've tested that showed little to zero CA would be my two telescopes that I use for nature photography, an Astro Physics and a Takahashi. These are the standard bearers for pretty much all telephoto, refractive type (glass...not mirror) optics.

Impressions of build quality - quite good. Weighs less than 10 pounds, and you can actually handhold the shot with good bracing if the situation needs it. Typical Canon build quality, which as you know, is already highly impressive. Rotating collar moves smoothly, no binding or roughness. The dual tripod screws on the bottom are a nice touch, one for 1/4x20 and the other for 3/8th. Beefy. The 600/4 weighs a bit more.

I was very surprised how much more CA was present with the 600/4 + 1.4x combo.

Will post the pictures later.

For that range, Sam, you are going to struggle with any camera lens.

Look into getting an astro refractor, pairing it with a couple of TCs and an SLR for prime focus photography. It'll be manual focus but you can get effective focal lengths of >4000mm this way. I've been doing some research into this myself and will be testing it out.

You can get started with <$1000 worth of kit (astro gear = lot better priced and optically a lot better than camera gear). Fast-moving action will be difficult, but with good light, you should be able to get some good shots... much better than what you could accomplish with an 800mm tele.

Keep in mind that at those distances, atmospheric haze (even under normal conditions) is going to affect your image quality substantially.

Vandit

You will find that the high end refractors from Takahashi, TEC and Astro Physics will outperform the 800 f/5.6L EF IS lens by a HUGE margin. That's the tests that I'm running right now. Literally day and night difference. Color correction, sharpness, contrast, etc. And at equivalent focal lengths.

Remember that Canon doesn't check for any zoning errors, perfect tip/tilt centering or 1/10th PV or 1/50th RMS error in figure. What you pay for is the durability and the build quality of the mechanics and focusing as well as the IS features. For Canon to make the lens sets as critical as the names mentioned above would cause the prices to skyrocket tremendously and wait times to be much longer than they are.

Stick with the refractors. NO REFLECTORS as the aluminum and it's structure will definitely cause loss of contrast, scatter, etc. At equivalent focal lengths and focal ratios, the refractor (lens based) will far outperform the reflector (mirror based) by a huge margin.

If anyone is interested in prime focus photography using refractors, check out this thread:
http://www.birdforum.n​et …hread.php?t=100​519&page=1

Lots of useful info there and some really amazing shots considering the absurd focal lengths that they are being taken at (4000mm or so for some of them). And some of those shots have been taken with a sub-$400 Celestron 80ED refractor... making it the best value in focal length/$ today.

PM01 - we are putting together a testing methodology for comparing different scopes and setups (see the last few pages of that thread). If you have a refractor and are doing prime focus work, please jump in with your thoughts and participate in the testing.

I'm getting a Televue 85 for precisely this purpose myself.

Vandit

Is that a bazooka?

Actually that's a fairly small telescope, but it does have very good optical qualities. Smaller than a 400 2.8L EF IS lens, but I'm willing to bet that the optics will blow the 400 2.8L EF IS out of the water.

I'm not kidding.

The telescopes that I'm using right now are the Takahashi FSQ106 w/1.6x Extend Q and the Astro Physics 130EDT w/reducer. Both are outstanding. Strehl ratios of the FSQ generally are in the .95+ region while the AP scopes are always nudging the .99 region.

A "diffraction limited" optic would be in the .8 region. 1.00 is considered a perfect optic.

In contrast, the commercially available mirror based optics are usually in the .4 to .6 region. A difference of .1 is VERY notable and easily noticed with the trained eye.

I've already written up an article and it should appear in Nature Photographer magazine sometime soon. The editors were completely floored to the optical quality and pureness of the pictures. And they've seen lots of Canon / Nikon / Leica gear and their results, but nothing as good as the ones shot by a high end telescope.

When that is published, any chance you can post a link?

Yep. Will do. That's if it makes the cut. They had me word the article so that it doesn't compare camera lenses - just so that I didn't offend any vendors. But, the article does show the amount of detail that is present with a high end telescope - amazing detail, amazing saturation and incredible color correction.

Put it this way. If you think the 800 f/5.6L EF IS is good (it is!), just increase those attributes by a factor of close to 10. It's that much of a difference.

The one problem with using a refractor for photography is that you are limited to good light and portraits only. Action shots aint really happening with it. Worth considering. I'd use an astro scope for specific types of photography (long range shots) but would not have one replace my regular lens.

Vandit

That's also why I use the 200 1.8L EF and the 300 2.8L EF as well as other lenses for fast action. For any of the slower objects, at far distance, I will always prefer the refractor. Lugging around the 16+ pound tube assembly is worth it at the end of the day when you're looking at the final images.

PM01 wrote in post #5825290
Yep. Will do. That's if it makes the cut. They had me word the article so that it doesn't compare camera lenses - just so that I didn't offend any vendors. But, the article does show the amount of detail that is present with a high end telescope - amazing detail, amazing saturation and incredible color correction.

Put it this way. If you think the 800 f/5.6L EF IS is good (it is!), just increase those attributes by a factor of close to 10. It's that much of a difference.

Ok, I'm sold -- when I can understand it, I'll go in that direction!

PM01 wrote in post #5828637
That's also why I use the 200 1.8L EF and the 300 2.8L EF as well as other lenses for fast action. For any of the slower objects, at far distance, I will always prefer the refractor. Lugging around the 16+ pound tube assembly is worth it at the end of the day when you're looking at the final images.

Hey, I agree with you. My Televue 85 should be arriving in a couple of weeks. (WOOHOOO!!!). I just wanted to point it out, in case someone is reading this and expecting to replace all his long teles with a refractor.... (you never know).

Have you tried the Televue Ethos eyepieces? 100 FOV... I am drooling in anticipation. My only worry is that I wont be able to go back to my regular spotting scopes after this.

What tripod/head are you using? I am going to use the Gitzo 1548 and may get an RRS head or the big Arca to support the OTA.

Vandit

The setup of scopes like that confuses me -- Does anyone happen to have a few links which describe exactly how it gets connected to the SLR?

It's actually very easy. You just need a t-ring and a nosepiece adapter. The t-ring mounts on your camera and the nosepiece attaches to the t-ring. Nosepiece goes into the telescope. You just need a steady tripod to support the telescope.

The nosepiece adapter that I'm using is the one from Astro Physics. PFCT. Cost is around 40 dollars. They make VERY nice and durable adapters.

I'm using a CF1325 Gitzo tripod and a 3047 3 way axis head. Works great. Also using the mark 3 camera.

vkalia - your televue will waste the Canon lenses in terms of optical quality. You'll be STUNNED. Now if you have someone that has a newer model AP or Tak...you'll be in shock.

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The Ethos EPs are QUITE good from all the feedback that I've been getting. Haven't looked through one yet.

Uncle Al makes good stuff.

switching gears...

800 f/5.6L EF IS - IT NEEDS WORK. I've shot some pictures of a great egret in it's natural surroundings. The color correction is good, but the flaring / glare around the bird is UNACCEPTABLE for a 12,000 dollar lens. It literally looks like a halo around the bird.

I spoke to a military optics specialist and he comments that the lens needs additional baffles. Some of the baffles that they have in the lens are in an angle that is reflecting light INTO the light cone. The flocking material that they use helps slightly, but not nearly enough to cut down on the flare/glare.

Will have to dig up the picture, but it's not worth the 12 grand.

My AP and Tak scopes will waste the 800 f/5.6L EF IS, and by a huge amount. Zero flaring, pretty much zero CA and it costs less than 12 grand.