Canon super tele L series lenses for astrophotography.

[cataclysm]

Just out of curiosity, anyone out there ever used such lenses for astrophotography? Lenses such as EF400 f2.8L, of even EF500/600 f4L telephoto. Such lenses employ elaborated multi elements to achieve near perfect corrections for terrestrial photography; their MTF charateristics is way off the chart. Besides costing an arm and a leg just wonder if they have any useful applications on astrophoto. Just for discussion sake.

[weixing]

Hi,
IMHO, most telephoto lens are better than most telescope for astrophotography, because they are very well corrected. The only problem is that they are just too expensive even if you compare to a top brand telescope.

Have a nice day.

[wucheeyiun]

The other thing to consider is that you will need to get a scope convertor...to convert the tele-lens to a telescope.

In fact i was about to confirm a used Nikon 400mm IF-ED manual focus f3.5 for $2500 before deciding on the flt 110, i saw a good deal in Clubsnap.

My consideration is that Rigid mounting is not readily available, and retrofitting filters is a consideration. There is a variety of EP you can use for the Telescope while the scope convertor is only 10mm.

At the end, a really good apo is the best choice, look nice on any EQ mount, and more usable.

[mrngbss]

I saw a setup using the Canon lens.

http://www.astrosurf.com/buil/elecfinder/test.htm

[ariefm71]

Use Mandel adapter: http://www.galaxyimages.com/ccdwidefield.html

[denebman]

In fact, the manufacturing tolerance of a camera telephoto lens is not as high as a good telescope objective, let along its ptv, rms and strehl ratio. The usefulness of a telephoto lens is for wide angle, low power and flat field imaging; if they are barlowed or coupled with an eyepiece to use at high power, the results is always frustrating when compared to a cheaper ED/apo telescope. In terms of on-axis sharpness, color correction contrast or more profound MTF (or SCF), I think a good apochomatic telescope lens is still the best, the camera lens falls far behind.

[MCYM]

I have mixed sentiment about canon L telephoto lens.

IMHO, there are no better way to image below 200mm fl without resorting to telephoto lens as telescope don't go this wide.

With quality in mind, L lens would be the perfect partner for canon DSLR users. However, what goes into such high-end lens are plenty of fancy stuff we don't in the realm of Astrophotography.
They are namely:
1. IS
2. USM (Ultrasonic Motors)
3. Correction for near focus.
4. The extra glass needed to attain (3 and 1)
5. Auto focus

what we need for AP.
1. Excellent field correction at infinity focus
2. UD elements for CA (Canon), ED (Nikon)
3. Fast focal ratio
4. Manual focus capability

The few lens the author mentioned (400, 500, 600mm) are largely replaceable with convention telescope (reflector/APO) costing much less and offer greater versatility.
Avoid IS if possible as they have a tendency to screw up starfields with non orthogonal corrective position.

Personally i have tried the 70-200mm f/4 and f/2.8 (non IS) both are good contender for widefield imaging.

Matthew

Off topic a little; Read in Canon tech papers, they appear to attained APO like performance using Diffraction Optics (low cost fresnel lens). With blessing of patent loopholes, I hope this technology would soon find its way to small scale scope manufacturer & benefitting astro community at large. (Pg 61)
http://www.canon.com/technology/pdf/tech2005e.pdf

[kayheem]

How about this:

http://www.superwasp.org/

Kay Heem

[MooEy]

I do not think these lens have any value in the astrophorography community, unless one can get it for some dirt cheap price. Last time i check the price for the 300/2.8 and 400/4 lens is somewhere in the 9k range. For that price, one can get the Pentax SDF4 and be very happy with the perfect performance on 6x7 film, and maybe have enough cash left over to buy a camera body or a mount.

For those who are interested in the performance of the L lens, try reading this website. http://www.astropix.com/HTML/M_DAP/M004/M004.HTM

From the above website, the author state his unhappiness about the performance of the lens. This however doesn't mean that the lens sucks or anything. The 400/4 and 600/4 lens are still greatly valued by bird shooter. For bird shooting, a 1.4/2x tc would normally be used with the lens, resulting in a f/ratio of 5.6 or 8. On iso 400, that would mean a shutter speed of merely 1/500 or even worst 1/250. That's where the IS comes in nicely, giving the user steady shots.

On the subject of DO lens. I do agree that these lens are much shorter and lighter than normal lens with ED glass. However one should notice that the image quality of DO are still inferior to the normal lens. Let's hope manufacturing becomes better and DO optics with 3 grating start coming out.

~MooEy~

[weixing]

Hi,
Hmm... very surprise to see that camera lens perform so badly on astrophotography... Hmm... So, they wasn't that well corrected as I thought after all.

Anyway, I had seen quite a number of astrophoto taken by camera lens and they are very good... Hmm... just wonder why??

Have a nice day.