Crescent Moon -- Refractor vs. Reflector

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Tonight's crescent moon made for a great photo subject, and a perfect opportunity for me to test a recent purchase of mine, a Tamron 55BB SP 500mm f/8 against a tried-and-true old refractor I own, a manual aperture T-mount Century Precision Optics 500mm f/5.6. I've had very good results shooting images of the moon with my CPO 500, several of which I've posted here, but tonight's the first time I've tried shooting the moon with my Tamron. In fact, this is the first time I've ever done any sort of critical comparison with it.

Honestly, I figured that, despite its age, the CPO 500 would show the superiority in contrast and sharpness that's almost always the case when a refractor is compared to a reflector. But as the two following photos show, the differences are much less than I would have thought. No sharpening was done with either image, although I did adjust contrast somewhat, mostly to the CPO's photo.

CPO 500mm f/5.6 @ f/8


Tamron 500mm f/8


I've combined the two images so it's easier to compare the two optics:


In retrospect, I probably should have left the contrast alone with the CPO's image because it does show to be contrastier than the Tamron's. But I took the CPO's photo earlier, when the skies were quite a bit brighter. I should have reduced exposure also. You'll note that there's some burn-through in the CPO's image along the edge of the moon. The image as shot was rather gray looking so I adjusted it by bumping up the contrast until the skies were about the same level of darkness as the Tamron's. The difference in skies also accounts for the difference in colors seen. The CPO's has a bit of a yellowish tinge, which was caused by the sky's sunset colors. By the time I shot with the Tamron, the moon's colors were dominant.

As you can see, sharpness wise, the two images are very close. The CPO just barely edges out the Tamron in sharpness. Take a look at the crater toward the bottom of the photos that has a small peak in the center. This crater has a double wall, which is well defined in both photos, but is just a bit better defined in the CPO's photo. Nonetheless, I was really surprised by just how much detail I was able to capture with the Tamron. And even though the Tamron mirror has almost a 360 degree throw to its focusing collar, its focusing is still very touchy at infinity. So given this touchiness, it is very possible that I may have missed optimum focus by just a bit, so who's to say?

Which lens is the sharper? Welp, I must conclude that this test is not conclusive enough to say. So, I'll have to do a retest. Oh, goody!

[iangreenhalgh1]

Nice shots, I do prefer the CPO one, probably more because it's more coloured than anything else as they are very close in IQ.

[s58y]

Nice shots. I've always have a hard time getting the best focus on moonshots. Atmospheric turbulence makes the details you're focusing on move around in magnified liveview, so you never know quite where to stop.

[IAZA]

I thought you have not god copy of Tamron 500, you mentioned in earlier post after you bought that tammy.
or I miss something?
the CPO shot is great, butI like result of tamron too

[Smoli4]

with camera did you shot with? cause i have two russion mirros, and i can crop to the same resulution , and compare one of my moon shots.

[yinyangbt]

It seems to me that the CPO is sharper . The tamron seems less contrasty and softer .It doesn't seems to me that you lost something in that slightly burned edge of the moon , at least the tamron image doesn't show some more detail there.

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[strudelj]

Nice moon shots. I would agree with others that the CPO is sharper. But I am biased; I exclusively prefer refractors over reflectors.

But really, most of all shooting something through kilometers of atmosphere is like shooting something through couple of meters of water. I would say that the sharpness of moon images depends more on seeing and atmospherics disturbances, than on quality of the lenses which both seem very good.

Another very important thing, CPO has a surprisingly low CA, especially for a fast f5.6 refractor. Was it stopped down?

[NewStuff]

First shot is the winner for me! Much prefer the overall look it presents.

I need to get my Benbo back, and run off a few moon shots.
Pentacon 300/4+2x TC should do the trick! (My current tripod runs screaming from this combo!)

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[NewStuff]

My Benbo is, I think, the MK1, with the 4 way head (I've seen a few trekkers, but never another 4way. I assume they are not common).

I've had it for 5 or so years, the previous owner had it from new, and still enquires about it to this day. He sold it after selling his *big* glass (the 600mm L was something to behold). It';s also dubbed the "Comedy Tripod" because of my propensity to lug it around abandoned buildings, asylums and slate mines, where you are far more likely to find someone using a Slik Mini or similar.

The feet have not cracked, but I do need to repair one of the tightening knobs on the legs. It's the best Macro tripod I have ever owned, and will likely be that way for as long as I can carry it. I wouldn't swap it for the world.

[cooltouch]

Good on ya. Mine came with an original ball head. I was over at the Paterson site, and determined that mine is most likely a Trekker because of the leg length. The bottom sections are only about 20" long or so. The ball head is what Patterson calls their Compact Ball & Socket Head, which was available with the Trekker models, but it is sturdy enough to support a long telephoto and a fairly heavy camera/motordrive combo.