Quote:
Originally Posted by jase
Its all relative Paul. I'm not going to deny that the US and European manufacturers are expensive, but they are also spending at least six to eight fold in time to build scopes compared to the Chinese or Taiwanese counterparts. As you say, the latter is mass produced, quantity over quality philosophy. Robotic arms instead of flesh and bones driving greater profit, but improved quality? hmmmm maybe with time?
So who wins? You buy one of these scopes, have to spend more money and commit your time to resolving matters which should have technically been addressed through R&D and QA. You've had your fair share of troubles as have others and I'm sure this has come at a cost. Alternatively, you pay more for an established instrument and get close to a turn-key imaging solution, be it minor tweaks to get it humming along. If the Chinese or Taiwanese manufacturers spent a similar quantity of time as the others, prices would climb, so its a trade off.
For the money that is out laid, the results are what I would expect and as such I'd be happy. Obviously everyone has different expectations. Whether they are realistic and obtainable is another discussion. With such a vast difference in quality between budget, mid spec and top end RC's, one can only compare results of a similar breed RC, so my previous post in reference in the 10" RCA is moot. The RCA series and those from deepsky instruments are mid spec instruments as opposed to the budget RC's coming out of China or Taiwan. What I was attempting to allude to however is that paying that bit extra can yield vastly different (superior?) results.
I want to be clear that I'm not attempting to put people off purchasing budget RC's. In many cases, they'll probably meet your goals and you will be happy with the output. There is a strong market for such instruments which will thrive with time. I do however suggest people review the facts and manage expectations. Comparing the differences between a 4k and 12k instrument can be the difference between night and day, no matter how much time and money you sink into getting the 4k instrument working. Its putting lipstick on a pig.
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I think that some of the points made here deserve closer scrutiny. The "quality" of images depends on much more that the quality of the optics. Firstly we should define what we mean by quality of images. There are some measurable parameters which I generally grade images, in particular sub-exposures for inclusion or exclusion in a final image.
The first thing I look at is the roundness of the stars. This is mainly influenced by the tracking of the mount. Barring any optical faults the roundness of stars on RC's af any brand are really good. The GSO RC has excellent roundness all the way to the edge of the field of my ST-10. I don't have an expensive RC to compare with, but there are many images to which I can compare. The quality of the optics are relatively unimportant wrt star roundness.
The FWHM of the stars, particularly a change between the centre and edge of the field. This can be influenced by many things, focus is king though, if the GSO is in focus I believe that it will produce stars with the same FWHM as any expensive RC. By far the greatest influence is your local seeing. The quality of the OTA will influence focus, as if the camera can be easily skewed, or the focuser is not up to taking the weight of the camera then this will make focus difficult to obtain and then hold. This is easily remedied by an aftermarket focuser, so add $500 to the cost of the GSO. If you know beforehand this is no big deal. I would not expect any of these problems with an expensive RC.
Optical defects can occur in any scope. They should not be allowed out of the factory, whether that be a big or small factory, obviously the more you make the more likely that one will slip through. GSO have proven to be very good about taking returns of defective scopes and replacing them. Astigmatism and field curvature are properties of the design, not how well the optics are made. The Strehl of the expensive scopes is almost certainly higher than those of the GSO scopes, but how high do you need to go?
Image depth is certainly one area that the optical quality of the scope can influence. Do the images produced by the expensive RCs have greater contrast? Is this more likely to be due to more longer, deeper subs from dark skies? I say yes and yes to both of these questions. I find that when the image contrast of a picture is greater than mine the photographer has taken more or longer subs. The scopes vary from refractors to various reflectors. The main problem with comparisons is that owners of $10k+ scope generally have them at dark sky sites on super mounts, not like the rest of us from a suburban location on a not quite so good mount.
I'm not saying that the expensive RC's are a waste of money, but for 5-10 times the money of the GSO variety they should be like chalk and cheese. They are not.
For the money you can't do better IMHO, bring on the 10", I can't wait, then the 12" version. If they are rubbish we'll know soon enough and I'll just have to make do with the 8" version.
Cheers
Stuart (Smearing lipstick on Bacon)