Lens test 500mm Mirror Vs Canon 250mm zoom

[Pyrofer]

I bought a cheap 500mm f8 Mirror lens on Amazon and decided to compare it with my Canon 250mm zoom lens at f9.

Here is the result, mirror on the left Canon on the right. The Canon one is the 55-250 EF-S IS lens.
The mirror lens is by Opteka and bought cheaply on Amazon. I think the Canon wins

[baggywrinkle]

Interesting to see such a side by side comparison.

What did you use to image the Moon with the 500mm mirror?

What were the settings on the Canon.

[Pyrofer]

Same Canon Camera used for both, a T2 adapter fitted the 500mm lens to the Canon 500D Body.

All the settings were pretty much the same, I think I had to drop the ISO a bit and increase the shutter speed for the Canon zoom lens as it was F5.6 I think and the mirror lens was F8.

I had hoped the 500mm Mirror Lens would be great for Astronomy, possibly it is ok. However due to the low detail when zoomed in it is no use for astro-photography. The Canon 250mm Lens easily out performs it.

The Canon Camera was on manual so nothing other than iso and shutter speed changed between the two images.

Settings for the Canon lens were Shutter speed 1/400, f5.6, iso 100 and 250mm focal length.

Settings for the MIrror lens were 1/160 f8.0 and 500mm I think.

I had intended to match the settings a bit more by stopping down the Canon lens to f8, but I simply forgot.

[RT65CB-SWL]

I recall the ads... "If anyone can Canon can." 

[mikehab]

I think a lot depends on the make/brand and f-ratio of the 500mm mirror lens.  I have the Samyang 500mm f/6.3 mirror (which is still a budget mirror lens - I got mine for <£80) and it's much better than the Opteka.  Here's a shot of the moon I took with the Samyang 500mm f/6.3 mirror...

Cheers,

Mike

[jgs001]

Interesting.. were these tripod mounted ? If not, then unless you had a suitably high shutter speed, I'd expect the 55-250 to win due to it's IS. The AF mechanism on the 55-250 is also pretty good, whereas with the mirror lens, it's going to be manual. Manually focusing on the full moon at shorter focal lengths is very tricky. The higher ISO used (although I can't read the EXIF) will also reduce the dyanmic range of the image for the mirror lens.

I'd suggest.. making sure that the camera is tripod mounted, use ISO100, set the 55-250 to f/8, that means the shutter speed should be about the same for both and repeat the test. Take extra care in focusing the mirror lens. I'd have expected the 500mm mirror lens to have produced a better result than the 55-250 when presented at the same image scale, assuming the same conditions apply to both lenses. Unless the collimation of the mirror lens is out of course, which, if it was posted and/or second hand it may well be. 

[Pyrofer]

I am disturbed by the quality and after seeing the Samyang (which I almost bought) am considering returning the opteka as I think it may be faulty.

It WAS posted but was brand new. Problem is I have had it quite a while before I finally got around to testing it properly.

That Samyang image is much more what I expected. I did use a Tripod and spent ages trying to get focus perfect so don't think it was that.

I wonder if it's possible to fix the collimation?

[baggywrinkle]

The Samyang looks like a good lens. I have been considering a longer telephoto lens.

[baggywrinkle]

They also have an 800mm..

http://www.samyang-lens.co.uk/samyang-lenses.html

[baggywrinkle]

I bit the bullet while I was in Singapore and bought the 800mm. Seems OK terrestially, I am off to Kazakhstan on Monday so I am taking it and my GF5 Panasonic with me and seeing if I can get any darker skies than I get in Shanghai.

[Okeydokey]

I have to say... whatever you are doing with your lens Mikes moon is a nice photo using budget gear.  Might come down to knowledge, experience and skill in the end?

[mikehab]

I have to say... whatever you are doing with your lens Mikes moon is a nice photo using budget gear.  Might come down to knowledge, experience and skill in the end?

Thanks :-)   More like a combination of a little bit of all 3, but more-so a large amount of luck, good seeing conditions and good stacking software I think.

Here's another shot taken with the Samyang 500mm.... both this one and the previous one are multiple subs (9 and 10 respectively) stacked using PIPP.  

Will be interested to see what kind of results baggywrinkle gets with the 800mm version.

Cheers,

Mike

[RikM]

Just to lob something into the mix, here is a single frame (can't remember the settings) Canon 1000D at prime focus on a 250PX manual solid tube Dob. I think for the small size and cost, those mirror lenses do a fantastic job.