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Buying an SCT
On Fri, 21 Jan 2005 22:41:37 GMT, SCT Buyer wrote:
I'm going to buy an 8" SCT in the next month or so, but am undecided if I should buy a Meade or Celestron. Generally speaking, which of the two tends to be better optically and mechanically? I can't afford to buy a new scope very often, so I want my decision to be an informed one. I've owned two SCT's, both 8". The first was a Meade 2080 (circa 1982). The optics were (apparently) exceptional for a mass production SCT. The Encke Division (Minima, for you purists) was visible nearly the entire circumference of the rings. It had an oversized primary, and smooth focusing. Tnen, in the late 1990's, I picked up a used Celestar with StarBright coatings (made around 1992?). Optically, it never performed as well as the Meade, but on occassion, delivered some of the best images of Jupiter I've seen, though not as good on Saturn! And, under dark skies, it provided a very pleasing view of M51. It is unwise to make too much of these annecdotal comparisons because the observations were made years apart, in different locations, under different condition, and are subject to the frailties of human memory. It is my understanding that the newer Meades have stepper motors which make an awful racket under the most peaceful skies. And Celestron's single armed fork isn't stable enough for serious long exposure photography. However, the larger Celestron scopes (esp. 9.25") are rumored to have excellent optics these days. Your best bet may be to buy according to features, from a company which will allow generoust test time and exchange rights. Then, test the dickens out of which ever you choose to see if it lives up to expectation. Cheers, and good luck, Larry G. |
#2
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On Fri, 21 Jan 2005 23:20:12 -0600, Larry G wrote:
It is my understanding that the newer Meades have stepper motors which make an awful racket under the most peaceful skies... Meades use DC servo motor drives (and have for as long as they made DC units, AFAIK). The drive systems perform very well, but are noisy. The newer units are somewhat quieter. The default high slew rates should be slowed down a bit to make operation quieter, and in all likelihood to significantly increase the mechanical life of the scope. _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
#3
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The last time I checked, if you go with a GOTO, the Meade may have more objects
but the Celestron is quieter. I like the packaging better on the Celestron, but this is subjective. Optically and mechanically, because they're mass produced, you have a spread of quality, and the mean or center of the spread is pretty much the same. Personally, my experience with their electronic or computer technical support departments is heavily in favor of Celestron, but others have reported differently. Good Luck ! -- Sincerely, --- Dave ---------------------------------------------------------------------- It don't mean a thing unless it has that certain "je ne sais quoi" Duke Ellington ---------------------------------------------------------------------- "SCT Buyer" wrote in message ... I'm going to buy an 8" SCT in the next month or so, but am undecided if I should buy a Meade or Celestron. Generally speaking, which of the two tends to be better optically and mechanically? I can't afford to buy a new scope very often, so I want my decision to be an informed one. |
#4
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It is my understanding that the newer Meades have stepper motors which
make an awful racket under the most peaceful skies. And Celestron's single armed fork isn't stable enough for serious long exposure photography. However, the larger Celestron scopes (esp. 9.25") are rumored to have excellent optics these days. Both the Meade units, and the Celestrons, use servos. The difference is that on the Celestron NS family, these are professionally made industrial servo systems. On the Meades, the older units used what were basically 'slot car' motors, and mouse encoders for the position, the latter units have retained the mouse encoders, but switched to slightly improved motors. The Celestron motors are more accurate, and smoother/quieter, _but_ they still have the downside, of no working PEC, in the NS units... I posted the following in answer to an almost identical question about 'which is best', on another group, and think it is close to saying it all... It is difficult. I have had a number of scopes from both manufacturers. Generally, in the last few years,I have allways found the Celestron optics to have the slight 'edge' (some of the earlier units were 'dogs'). Apparently this may be down to a fractional difference in the way the correctors are fabricated, giving slightly less chromatic aberration. However on all the modern scopes, both are pretty good. Mechanically, the Meade, has the better external 'finish', with nicer shaped knobs and handles, and surface detailing. Internally, the Celestron has the better drives on the NS models in particular. The Meade has more 'frills' in the hand controller, but in use, both work well, and point to the objects you want, with the NS, being slightly quieter. The Celestron scopes are easier to 'handle' for a given size. The actual lifting handles work, while the Meade ones are poorly placed. Currently, on the Celestron NS models, PEC, still does not work. However their drives are enough better, that tracking is still very good. It is though a very 'silly' missing feature. I 'prefer' Celestron, having had better performance, and experience with servicing from them. However that being said, I'd say that (perhaps unfortunately), it is down to the 'deal' you can get. I suspect you will be able to afford more 'extras' with the Meade, than the Celestron unit. There is also the problem, that these 'bundles', are so cheap, that it makes other routes look expensive. For instance, as a small SCT, with a 'great' mount, I'd say the combination of a third party mount (the GP-DX for smaller scopes, and the G-11 for heavier units), with a Celestron OTA, is really nice, but the price of this type of setup is far above what you can buy a bundled scope, mount, and controller for... Take your time, see if you can actually 'see' the scopes you are considering, before spending your money. Both makes are phenomenal value for money, with an 8" SCT, and mount, with very competent optics, costing less, than I paid to make an 8" Newtonian, with basic clock drive, some years ago. Best Wishes |
#5
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Based on experience, I would give the nod to Meade for excellence in
service alone. Matthew Ota SCT Buyer wrote: I'm going to buy an 8" SCT in the next month or so, but am undecided if I should buy a Meade or Celestron. Generally speaking, which of the two tends to be better optically and mechanically? I can't afford to buy a new scope very often, so I want my decision to be an informed one. |
#6
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Hi,
Could you expand on this comment with further detail ? "The Celestron motors are more accurate, and smoother/quieter, _but_ they still have the downside, of no working PEC, in the NS units..." And how Meade apparently has a working PEC? I jsut bought a N11GPS so I am interested in your further discussion on this subject. Thanks TMT |
#7
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"Too_Many_Tools" wrote in message oups.com... Hi, Could you expand on this comment with further detail ? "The Celestron motors are more accurate, and smoother/quieter, _but_ they still have the downside, of no working PEC, in the NS units..." And how Meade apparently has a working PEC? I jsut bought a N11GPS so I am interested in your further discussion on this subject. Thanks TMT The motors in the Celestron, are industrial servo systems. These are quite expensive assemblies with armatures designed to minimise 'cogging', and give smooth responses. They are about 10* the price of the motors used in the Meade scope!. They are quieter, and smoother than the Meade units. However the biggest error for short durations on any scope, is surface errors on the main gear, and the worm. A tiny misalignment of the shaft, or a small error on the surface finish, translates into several arc seconds of movement. The error in earlier gears in the drive is reduced by the gear ratio after the gear. It is the final drive worm (because of it's small diameter, relative to the main gear), which ends up introducing the biggest error. Fortunately, the largest part of this error is 'periodic', repeating each time the gear turns. In order to improve this, scopes generally apply 'periodic error correction', where the movement of the worm, is fractionally 'tweaked' to adjust for the errors. This feature, has never (yet) worked on the Celestron NS scopes. However their 'uncorrected' error is typically a little less than on the Meade units, and fortunately quite smooth (which allows guiding to correct it fairly well). This is the cause of quite a bit of 'annoyance' to imagers wanting to use the scope for long exposures, without having to rely too much on the guiding. It is important to realise the difference about PEC, versus correcting this with the guider. The guider is allways 'reactive', it can only correct for an error that has occured. PEC, can be 'proactive', correcting for the expected error as it occurs. Best Wishes |
#8
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Could you expand on this comment with further detail ? "The Celestron motors are more accurate, and smoother/quieter, _but_ they still have the downside, of no working PEC, in the NS units..." Hi: The Celestron uses high-quality Pittman servos, though the lower quality motors of the LX200 GPS certainly don't seem to hurt it. They do seem a wee bit noisier. But the LX200s are quite accurate indeed. As for PEC, no, Celestron's PEC is NOT working correctly. They are aware of the problem, and are supposedly working it. I doubt it's a front burner thing, though, as most folks seem to have got away from PEC and are tending to either autoguide or stack short exposures, both of which are techniques that make PEC a little less needed. Peace, Rod Mollise Author of _Choosing and Using a Schmidt Cassegrain Telescope_ Like SCTs and MCTs? Check-out sct-user, the mailing list for CAT fanciers! Goto http://members.aol.com/RMOLLISE/index.html |
#9
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Rod Mollise wrote in message ... Could you expand on this comment with further detail ? "The Celestron motors are more accurate, and smoother/quieter, _but_ they still have the downside, of no working PEC, in the NS units..." Hi: The Celestron uses high-quality Pittman servos, though the lower quality motors of the LX200 GPS certainly don't seem to hurt it. They do seem a wee bit noisier. But the LX200s are quite accurate indeed. As for PEC, no, Celestron's PEC is NOT working correctly. They are aware of the problem, and are supposedly working it. I doubt it's a front burner thing, though, as most folks seem to have got away from PEC and are tending to either autoguide or stack short exposures, both of which are techniques that make PEC a little less needed. Peace, Rod Mollise well, Celestron calls those Pittman servos "high quality". As far as industrial grade servos, they're as lame as the Meade using Mabuchi toy motors. They're low end motors, nothing high quality in them. Higher quality than Meade due to metal gearhead instead of plastic , that's about it. Same size but high quality servos would cost several hundred dollars apiece , would be brushelss or coreless , the Pittmans are $10 each, the Meade are $2 each. best regards, matt tudor |
#10
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Rod Mollise wrote in message ... Could you expand on this comment with further detail ? "The Celestron motors are more accurate, and smoother/quieter, _but_ they still have the downside, of no working PEC, in the NS units..." Hi: The Celestron uses high-quality Pittman servos, though the lower quality motors of the LX200 GPS certainly don't seem to hurt it. They do seem a wee bit noisier. But the LX200s are quite accurate indeed. As for PEC, no, Celestron's PEC is NOT working correctly. They are aware of the problem, and are supposedly working it. I doubt it's a front burner thing, though, as most folks seem to have got away from PEC and are tending to either autoguide or stack short exposures, both of which are techniques that make PEC a little less needed. Peace, Rod Mollise well, Celestron calls those Pittman servos "high quality". As far as industrial grade servos, they're as lame as the Meade using Mabuchi toy motors. They're low end motors, nothing high quality in them. Higher quality than Meade due to metal gearhead instead of plastic , that's about it. Same size but high quality servos would cost several hundred dollars apiece , would be brushelss or coreless , the Pittmans are $10 each, the Meade are $2 each. best regards, matt tudor |
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