Canon 200/2.8 for astrophotography

orly_andico · Post by **orly_andico** » Tue Dec 28, 2010 10:05 am

hi all (and particularly Stuart [smilie=cool.gif]

)

has anyone used this lens for astrophotography?
this review..
http://www.zodiaclight.com/equipment/lensCanon200mm.htm

states it's very good at f/3.2 but has aberrations in the center of field at f/2.8 (need to stop down to f/4.5 to get perfect results).

I currently have a WO 70mm ED with the WO Flat II giving 336mm and f/4.8, and f/2.8 is my interest (almost 2 stops faster) because 2 stops faster = 1/4 the time and I won't need as fancy a mount.

But if f/2.8 is "unusable" and f/4.5 is needed, then I see little benefit over the WO Zenithstar (although I could use the lens at the zoo..)

here's a shot at f/2.8 (by the guy who wrote the above review)

there are those fan-shaped stars all over the place.. is that coma?

cloud_cover · Post by **cloud_cover** » Tue Dec 28, 2010 10:15 am

Yup, that's coma, I think. I get the same thing with my lenses when I use them wide open.
I'm sure your telescope with flattener will provide better stars. Could the money saved from getting the 200 f/2.8 then be used for a better mount which can tolerate your 9.25?

orly_andico · Post by **orly_andico** » Tue Dec 28, 2010 10:23 am

Kevin,

the 200/2.8 is a particularly cheap lens (under $1k SGD used, it's the 2nd cheapest red-ring lens, after the 70-200/4).

I can't get a decent mount for my 9.25 for anywhere close to that amount..

cloud_cover · Post by **cloud_cover** » Tue Dec 28, 2010 10:28 am

That cheap huh?

I'm no expert on Canon lens and pricing, or course.
Having said that, if you switch to canon DSLRs, then its also a good lens to use, esp for portraiture and nature. I love the way f2.8 makes the background all dreamy. My wife complains though that it looks photoshopped!

Post by **weixing** » Tue Dec 28, 2010 10:29 am

Hi,
IMHO, most decent APO telescope are sharper than most camera lens especially you had a field flattener.

Anyway, I see no point of changing unless the colour correction of the lens is better than your WO 70mm ED. Of course, if they had the same colour correction and sharpness (lens stop down), then you might consider the change if you want to use the lens at zoo.... but you'll lost a portable wide field scope...

Conclusion: get both... ha ha ha [smilie=victory.gif]

Good luck and have a nice day.

orly_andico · Post by **orly_andico** » Tue Dec 28, 2010 11:55 am

The WO is f/6.2 native and f/4.98 with the Flat-II (which was designed for the WO66, maybe that's why it did badly on your ZS80).

I haven'd had the chance to try it out since getting the reducer because of weather. But without the reducer it has eye-popping egg stars on APS-C, unusable (DSS couldn't even find stars for the plate-solving/stacking!)

I already have a Canon DSLR so the Nikon 180/2.8 would be out of the running for me..

Bergkamp_ · Post by **Bergkamp_** » Tue Dec 28, 2010 12:29 pm

=x i think is the review by people ba.. i also saw alot of review that flat 2 is very gd with 66..

orly_andico · Post by **orly_andico** » Tue Dec 28, 2010 2:23 pm

hi stuart,

actually WO's description is that the Flat 2 is ".. for 66-90mm refractors." i must've read (somewhat) that it was specifically for the 66mm.. i also assumed this because it has an SCT thread (which the 66mm in various guises have, instead of a 2" visual back).