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Old 30-11-2007, 08:18 PM
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Astro Lens for DSLR

what wide field lens would you camera gurus recommend for astro work with a Canon 400D with an approx $2000 budget? thanks.
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Old 30-11-2007, 08:24 PM
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Whoo there are a lot of good lenses out there Mick.

See Widefield Lenses on a budget
especially Terry Lovejoys input about half way down.

Me...I love my 135mm. Maybe not a true widefield but a lovely lens non the less. I think my next purchase is a 17-40 like Mikes.
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Old 30-11-2007, 08:44 PM
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Mick, as Paul mentioned the Canon135mm F/2.0L lens is a stunner, I have one of those, and also the 17-40 mm F/4.0L you will not go wrong with either.

leon
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Old 30-11-2007, 08:48 PM
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thanks guys, would something up to 200mm f/4 still be regarded as widefield?
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Old 30-11-2007, 09:01 PM
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Quote:
Originally Posted by mick pinner View Post
what wide field lens would you camera gurus recommend for astro work with a Canon 400D with an approx $2000 budget? thanks.
Instead of getting a canon lens, why not get a televeue 60 is

Paul
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Old 30-11-2007, 09:23 PM
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Probably not Mick, though I guess its a matter of perspective. The 135mm really isn't a wide field either which is why I'm looking at the 17-40. Ideally I'd like the 17-40 (true wide field), an 85 (still in the widefield range), 135 (starting to get a bit tight but does a fantastic job of those wider nebula areas in scorpius, sag etc) , and a TAK 60 with focal reducer (definately not widefield ) .

Which reminds me I'd better get tomorrow lotto in.
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Old 01-12-2007, 02:42 AM
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Have you considered a fixed focal length lens, I don't know about Canon but I got a really nice 50mm F1.8 for mi Nikon and a sub $300 price for a New Nikkor Digital Autofocus lens. The trouble with the zooms is that they are all f4.5 or smaller.

Roger
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Old 01-12-2007, 07:36 AM
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Hi Roger. Canon have a number of 50,, lenses. The standard one is f1.8 (~ $135) and stopped down a bit it makes a great astrolens for the price. They then have the f1.4 (~$600-$800) which is brilliant apparently and then the f1.2 ( ~ ) which is also very good as well

I concur about the zooms though the 17-40 is f/4 and by all acounts is a cracker of a lens. My biggest issue with zoom lenses is preventing the zoom ring from moving accidentally when focusing. Personally of the few lenses I've used I much prefer a fixed length lens.

Oh and Mick, the canon 85mm f/1.2 is supposed to be the pick of the crop but at around $2500 -$3000 you'd hope it would be. A comparison review of the f/1.2 and f/1.8 (not astro though) can be found here http://www.wlcastleman.com/equip/reviews/85mm/index.htm
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Old 01-12-2007, 11:35 AM
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Quote:
Originally Posted by [1ponders] View Post
>snip
I concur about the zooms though the 17-40 is f/4 and by all acounts is a cracker of a lens. My biggest issue with zoom lenses is preventing the zoom ring from moving accidentally when focusing. Personally of the few lenses I've used I much prefer a fixed length lens.
>snip
That is a good point Paul. My old Vivitar Series 1 80-200 zoomed by sliding the barrel in and out, a bit like a trombone action, and gravity used to make it slide down when pointing skywards. I fixed this with rubber bands a dodgy solution really.

I am not expecting the same issue with my Canon zooms, as they zoom by twisting the separate zoom ring rather than trombone-ing.

Cheers

Dennis
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Old 01-12-2007, 11:49 AM
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The trouble with the zooms is that they are all f4.5 or smaller.

Both Canon and Nikon offer 24-70mm f/2.8 lenses. Also, Canon has a 17-55mm f/2.8 EF-S but it basically has L level pricing. Yes, I am aware that all lenses mentioned here cost as much as a decent APO.

I need to try my Sigma 15-30mm f/3.5-4.5 piggyback one of these days. It does quite well in daylight, and is very inexpensive but seems decently solid as compared to a lot of other Sigma offerings. They also offer a 10-20mm, which would be truly wide (86x128 degrees according to CCD calc).

Eric
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Old 06-12-2007, 03:38 PM
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Surprised no-one has mentioned the 35/1.4

it pretty much makes the 17-40, the 16-35, and the 24-70 quite silly at 35mm

and it's not that pricey either
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Old 06-12-2007, 08:04 PM
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and it's not that pricey either
I guess I need your budget
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Old 06-12-2007, 08:32 PM
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Interesting topic.

Found this site with MTF curves for Canon lenses:

http://www.pbase.com/samirkharusi/canon_mtf_curves

Best to select 'large' or 'original' size images to download.

Don't miss the first image which gives some idea of how to read the MTF graphs.

Also note you only need to read the results out to 13mm from the axis for APS-C sized sensors (e.g. the 400D).
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Old 06-12-2007, 10:08 PM
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Thanks for that, it was interesting to compare some of my lenses and find out which lens will be sharpest in a given scenario.
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Old 10-12-2007, 07:51 AM
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Interesting info on Canon lenses can be found here:
http://www.canon-europe.com/Support/...ork_iii_en.asp
However, my personal approach to the "problem" of ideal astro lens would be quite different..... simply because I can not possibly afford what Cannon is offering (apart from 400D or whatever body of course). Besides, for astro work AF, IS etc etc... are not needed.
The only essential things the astro lens must have are good, flat MTF curve (that means sharpness at reasonable aperture, to have shorter exposure times), not too much geometrical distortions (however this is not important for "pretty picture" at all, it may be important only if someone wants to do positional astrometry but I doubt anyone on this forum really wants to do this) and reasonable CA, which usually shows most severely at the image corners.
There are many alternatives out there for 1/10 of a Canon price or even lower, while results are the same (or almost the same), so all those Canon k$ are impossible to justify to my ministry of finance :-)

Last edited by bojan; 10-12-2007 at 09:06 AM.
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Old 10-12-2007, 12:34 PM
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Thanks for the Canon Europe link Bojan.

When you say there are alternatives "for 1/10 of a Canon price" are you talking about lenses, and if so, what are these alternatives?
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Old 10-12-2007, 12:46 PM
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Quote:
Originally Posted by okiscopey View Post
Thanks for the Canon Europe link Bojan.

When you say there are alternatives "for 1/10 of a Canon price" are you talking about lenses, and if so, what are these alternatives?
Yes, I was talking about lenses....
For instance, russian made Tair-11A ( I have it for years, I can send you some sample images if you want to compare) is comparable in performance with equivalent Canon at f5.6, it seems, maybe only slightly worse.
It is available on ebay for US$70 or so.
Also, APO Telezenitar 135mm is excellent, according to people who use it, and for ~US$260 it is 1/10 of the price for Canon 135mm, absolute bargain (it is manual of course). I intend to buy this one as soon as my budget allows :-)
Currently I am playing with Tamron 200mm, it seems to be very good (using eyepiece, I still need adapter to fit in on 400D).

Last edited by bojan; 10-12-2007 at 01:07 PM.
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Old 10-12-2007, 01:01 PM
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Also a good one is the old Canon FD mount glass, or the old Nikon AIS glass. Personally I'd probably prefer that to the old russian stuff.

That stuff is dirt cheap on ebay, and you just get a cheap $20 mount adapter. You won't have AF or metering, but you won't need that pointed to the sky.
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Old 10-12-2007, 01:38 PM
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Also a good one is the old Canon FD mount glass, or the old Nikon AIS glass. Personally I'd probably prefer that to the old russian stuff.

That stuff is dirt cheap on ebay, and you just get a cheap $20 mount adapter. You won't have AF or metering, but you won't need that pointed to the sky.

The Canon FD lenses on an EOS won't give focus at infinity with a straight-through adapter - which really is what we want after all with astro stuff!

The distance between the end of the FD lens and the film-plane (or sensor-plane? is not enough, so even a glass-less adapter of zero thickness will not allow focussing to infinity - what you end up with is a macro lens.

You can get an adapter with glass that allows the use of FD lenses on an EOS body and infinity focus, but the image quality is severly degraded. Its OK for family shots or holiday snaps at f5.6 - f11, but that's about it. I got one from http://www.bhphotovideo.com/c/produc...for_Canon.html

I have a FD 35 F2.8, FD 50 f1.4 and a fantastic FD 100 F2, but they are of no use whatsoever for astrophotography when mounted on my 40D.

I have thought about pulling one of then apart to see if I can shorten the mount and use it, but I don't know if I can be bothered.

You can get a adapter for almost any other lens to EOS - I had an Olympus to EOS, a Contax to EOS and Pentax M42 to EOS and they all were really good and I used them with a Contax (Carl Zeiss) 50 mm f1.4, and a Olympus 400 mm f6.3. Until someone stole my camera bag....

I now use a Canon 28 F1.8 and Canon 50 mm f1.4 and they are very good lenses. I also now have a Canon 400 f5.6.

So if you want a 'cheap' but good lens and don't care about autofocus, then I would say have a look for a Contax, Leica, Nikon or Pentax SMC M42 lens. Probably the cheapest out of these would be the Pentax SMC M42, but many of these lenses were, and still are, as good if not better than any new lens. They are also often very cheap, especially the ones that have gone yellow - the Lanthanum in the glass makes the glass yellow with age, but if you just stick it in the sun for a few days, the UV will bleach the glass.

If you want autofocus and so on, just stick with a good canon lens - for wide field, I think the 28 f1.8 is a very good lens and it also acts as a 'standard' lens on a 300/350/400/20/30/40D. Otherwise the 50 mm f1.8 is optically very good and very cheap - but mechanically not the best. The 50 f1.4 is a very good lens, but a lot more money.
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Old 10-12-2007, 02:18 PM
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I have thought about pulling one of then apart to see if I can shorten the mount and use it, but I don't know if I can be bothered.
I believe the price difference is definitely worth the effort....
Possibly it can be done by drilling couple of mount holes into the cheap M42-EOS adapter and then screwing it on the back of the lens :-)
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