Question on Refractors
Posted 25 April 2013 - 09:52 AM
Posted 25 April 2013 - 10:08 AM
Posted 25 April 2013 - 10:23 AM
I would sell the 127 and replace it with something like a decent 10"-12.5" dob.
I agree with Jason's recommendation.
Posted 25 April 2013 - 10:29 AM
Posted 25 April 2013 - 10:57 AM
I have a Meade 127mm APO triplet and a FS-102. Just curious if anyone thinks I should keep the 127mm. It of course does not have the quality visually that the Tak has but it does have 25mm of extra aperture. Just trying to see what the consensus might be.
What does you experience tell you? You have the scopes, you know how they compare, you know what you like to do.. Is the 127mm Meade redundant? Does the FS-102 provide similar views? Do you find that you use the FS-102 every night and the 127mm Meade once a year?
I can tell you what I would do but your experiences with these two scopes, the quality and detail they provide at the eyepiece, the ease of use... these are things only you can know.
Posted 26 April 2013 - 11:02 AM
I would sell the 127 and replace it with something like a decent 10"-12.5" dob. A high quality 4" APO and a big dob compliment each other very well and will really expand the versatility of your scope line up. If you like driven mounts such as I do, a larger SCT would also make a nice compliment to your Tak.
Posted 26 April 2013 - 11:50 AM
Other manufacturers make telescopes that are as good or better than the Taks from a quality perspective?
Here is a Vixen scope that is on par:
Vixen Vs Tak
And Meade may have stepped up, but we don't know for sure. Many of these smaller optics are being cut by new computerized machines capable of spitting out near perfect optics time after time after time. Look at the Skywatcher/Orion/Synta optics. They are coming off the line with superb quality.
Maybe the Meade is too.. How do you know it is not?
Also, just because the optics may not be perfect in the Meade, an extra 25mm of aperture can make up for a lot of shortcomings in optical quality.
Unless you need the true field of the 4" scope, I would keep the 5" scope.
Here is an MTF for a 5" scope with 1/6th wave of spherical aberration (not great, but not bad) and I even threw in a little bit of higher order spherical aberration just for fun.
Red line would be a perfect 5" aperture. Dashed red would be a 127mm aperture with only OK optics (and remember, the Meade may be much better than this).
The green line is a perfect 4" aperture.
it is easy to see that unless the errors are severe, the larger aperture can still perform better on contrast, and it will also provide brighter or larger scale images.
Or, you could just choose to believe that quality trumps everything, and hey, I get that.
But the laws of diffraction are usually in the camp of the larger aperture when the scopes are otherwise quite similar in design (ED or Achromatic refractors).
Unless you have some objective reason to suspect that the Meade's optics have a serious quality issue, then you are just going on what other peoples opinions and have not really analyzed the physics of it.
I like aperture, and regardless of the type of scope, in general, the bigger that's scope has been (little refractor vs big refractor or little SCT vs Larger SCT), the better it has performed.
The exception has been big achromats, which I find to be poor instruments for demanding applications.
I would not be so quick to dismiss the benefits of aperture though. Bigger and brighter images and contrast that may be at least as good, and likely better.
I have danced the dance with 4" refractors for a decade and a half, and in the end, I find that the bigger a refractor is, the more I have enjoyed it. I enjoyed my less than perfect Meade 152 ED almost as much as my near perfect AP 6' scope. One had to work a bit to see that the AP was better. In no way did the very subtle differences ever jump out, and in fact, I may have a placebo effect from the AP brand. The Meade 152ED was the refractor that finally made me love refractors.
Posted 28 April 2013 - 01:36 AM