Diagonals

Hello Group - I'm in the market for a 2" diagonal for my SCT. Its not a matter of money,
but getting the best bang for my buck. Meade, has a 5000 series 2" diagonal with 99% reflectivity, and
dialectic coatings. I saw them new, on Ebay for around $139. Now Televue, has about the same
advertised type of diagonal - - 99% reflectivity with the dialectic coatings for $284, double Meade's price.
Has anyone ever done a comparison on these diagonals? Am I buying a "name" with Televue, or is it really
twice as good as the Meade? I would like your opinion, before purchasing.
Thanks
Mike L.

Yeah - I did an exhaustive comparative study of 15 star diagonals - measured alignment, wavefront, spectral throughput, etc. Most were deficient. Of the two Meades, one had terrible angular alignment and one had fairly low strehl (but measured over the whole diam so probably still fine when used in traditional way). Of the two TeleVues, one had a slightly low strehl and the other was very nice indeed. Here's a copy of the summary sheet. I can send anyone the entire paper if they like. If I had a web site I would put it there. Final comment - it you are doing polarization studies the dielectrics can induce phase changes that could screw up your measurements of IQUV (Stokes Parameters) or the Jones Matrix ... but Very Few here would be doing that kinda stuff! Tom

Attached Image:

Here's the summary sheet - Tom

Attached Image:

Some good data here but I would like to hear from some as to actual observational results. I recently took an extended trip out west with telescopes, and got in some observing, but not as much as I wanted! While enjoying a very good night in the Badlands, SD, I did a short comparison of some diagonals on my C 9.25. The celestron 1.25 prism, a Baader 1.25 prism, a Williams 99% 2" and a Antares SCT 2" that was marked 98%. After an hour or so viewing two open clusters (double cluster and NGC 7789) with all the diagonals and 2 different Explore Scientific ep's, I could not see ANY differences in sharpness, light levels, vignetting, etc. Now admittedly I was not using instruments, just my surgically enhanced eyeballs. I am 73 and recent cataract surgery has restored the eyes of my youth 8) Well, almost! But the point, at least in my limited abilities, I really could see little to no difference in the views. I honestly was a little disappointed, especially after paying for the Baader. I really concentrated on seeing a difference between it and the Celestron 1.25 that came with the scope. There was none that I could detect.

Comments/examples would be appreciated.

Walt