Celestron G-5


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Subject: Re: vote by xxx.xxx.69.8
By: webmaster
Date: 01/15/2002 03:09:17 pm PDT
>
>Unless you can afford it, and the time to maintain it, don't buy a telescope.
>

You should perhaps qualify your statement a bit more...

Like most products out there, there are different tiers of telescopes: from the $5,000+ APOs to the garage sale Tascos you can get for maybe $5. And like most products, you should buy the one that suits your interest in the hobby.
People seem to get on a whole trip of "my telescope is better than your telescope". If you're one of those people, and you don't have wads of cash to spare (or lots of time), then maybe its not for you. But for those who just simply like to see stuff in the night sky, a cheap telescope might just work.

I'll bet the telescopes that Gallileo or Sir Isaac Newton used aren't half as good as some of the "junk" that's out here now. Yet look at what they were able to see in them? Likewise, even the most expensive APOs and Takahashis usually can't compare to proffesional observatorys and in turn those can't compare to the Hubble.

On the other hand, with all the Hubble pictures and proffessional CCD or long exposure pictures floating around, sometimes people do have unrealistic expectations from their telescopes. There are other things that people don't think about when buying a telescope like how to find objects in the sky, how cold it gets sitting out in the dark for extended periods (depending on time of year and where you live of course), and how much of a pain it can be to lug a large telescope around. By and large, these are better reasons NOT to buy a telescope, although some of the newer GO-TO scopes like the ETX alleviate some of these burdens (finding objects and lugging around).


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Subject: Re: vote by xxx.xxx.69.8
By: Anonymous (xxx.xxx.81.46)
Date: 12/12/2002 02:51:19 pm PDT
Hey, nice language. You don't need a telescope. You need a good counselor. How about not clogging this site up with incessant whining. JCD.
>The first time ever in the history of histories that I have seen someone say out loud, loud and fucking clear that telescopes are basically run by a bunch of businessmen making money out of the unprepared. Do you need to be prepared? What is this, a crash course in flying without a parachute?
>
>Unless you can afford it, and the time to maintain it, don't buy a telescope.
>
>The fact that the events themselves are 1 in 100 at any one point on the surface of the planet, pretty much makes me see that unless - as the last author has stated - you can afford a Takahashi or AP, you're in for a rough ride with support. I've never seen ANY scope come to what you SHOULD expect from this detracted industry. If hubble can't build enough interest in the fucked-up world we live and present it to us, you think the garbage being made is going to make a difference? It sure isn't making much of a stance on my interpretation of it.
>
>It's definitely a self learning curve and stuff you if you have problems (seen from the perspective of the manufacturer).
>
>I was tempted to move in astronomy, I'm getting grey hairs for starters, but right now, I don't have time for this "churn out the crap" for budding astronomers with less than 10,000 in their bank account to actually spend in one go.
>I know of one individual who is hooked on it - I understand this, so does everyone else, I know why you all do it too - but the subjective aspect to it is that it's kind of like being unable to pull away from the idea that you could "see so much more" if you "just shove this thing onto it", having paid several thousand on it just for the OTA.
>
>The whole thing is a bloody minefield.
>
>In 5 years, I'll definitely consider something like a Takahashi. I've looked through one directed at Saturn, and it's fair to say that it "changed me" in a way I can't describe. As ludicrous as it may sound.
>
>I didn't get that from ANY telescope I've encountered so far.
>
>This is the problem with atronomy. Unless you're incredibly rich, you are basically blind to it. Unless you are also incredibly patient and don't care about money, it'll also make you very small and poor.


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Subject: Re: vote by xxx.xxx.31.82
By: Anonymous (xxx.xxx.96.200)
Date: 11/29/2003 07:09:05 pm PDT
>Postscript to my comments of 8-25-00 about the G-5 - The ota went back to Celestron where the corrector was pretty nuch properly centered. The other work done was "cleaning and collimating". The scope still has very noticeable sherical abberation. Jupiter and Saturn barely tolerate 100X and even that is marginal. Cassini's division is only suspected most of the time and is never clear. BUYER BEWARE: It appears that Celestron's definition of "diffraction limited" has changed recently.


You have a defective scope. Either the mirrors are figured wrong or the corrector plate is improperly matched. Send it back to Celestron, scream, rant, and rave....and they will fix it to near perfection.
I have owned over 60 scopes, and the only 3 with "bad" optics were all premium refractors. Two AP Travelers (YES Travelers) and one Meade 127ED. One Traveler needed to be refigured, and the other needed to have the lens remounted and re-oil spaced. The Meade needed to have an element replaced. Out of the 3 C5s I owned, all were gems!!! You were just unlucky, that's all.
The moral of the story is...Buyer beware, no matter from whom you buy....


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Subject: Re: Celestron C5 performance
By: Anonymous (xxx.xxx.213.5)
In Reply to: Anonymous (xxx.xxx.96.200) (Original Message)
Date: 12/23/2003 09:46:02 am PDT
>>Postscript to my comments of 8-25-00 about the G-5 - The ota went back to Celestron where the corrector was pretty nuch properly centered. The other work done was "cleaning and collimating". The scope still has very noticeable sherical abberation. Jupiter and Saturn barely tolerate 100X and even that is marginal. Cassini's division is only suspected most of the time and is never clear. BUYER BEWARE: It appears that Celestron's definition of "diffraction limited" has changed recently.

I own a C5 which also gave poor performance, after a quick star test it appeared it was out of collomation. However despite tweaking I was un-able to fully cure the problem. After reading comments posted in a Sky and Telescope review, I relised that the corrector plate was not centered.
I loosened the ring that holds this plate and centered the corrector (being carefull NOT to rotate it!) and re-collomated.
This has totally fixed the problem. With this scope not only is cassini division sharp and crisp, but I can also see the crepe ring. It must be noted that when re-tightning the corrector, not to do it up too tight, or you will suffer from pinched optics.
(just tight enough to hold it in place)
I am aware that you got Celestron to collomate you scope, but shipping (or even a trip in a car) often affects alignment.

I have noticed **some** (a tiny amout) of spherical abberation with this scope, and also a **tiny, tiny** amout of surface roughness, but not enough to really affect the view. I am not really qualified to say, but It does appear to perform like a difraction limited scope, when one considers it has a ~40% obstruction.

One more note, the amout of spherical abberation with this design does depend on the distance between the eyepiece and the rear cell. (source = sky and telescope) Are you performing the test with the eyepiece directly in the visual back? This might be the problem. Also a naff diagional, eyepiece or even eyeball can make a scope look aberrated.

Hope this helps

Andy Knight


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Subject: Re: vote by xxx.xxx.31.82
By: Anonymous (xxx.xxx.109.210)
In Reply to: Anonymous (xxx.xxx.96.200) (Original Message)
Date: 01/10/2004 07:32:28 pm PDT
>>Postscript to my comments of 8-25-00 about the G-5 - The ota went back to Celestron where the corrector was pretty nuch properly centered. The other work done was "cleaning and collimating". The scope still has very noticeable sherical abberation. Jupiter and Saturn barely tolerate 100X and even that is marginal. Cassini's division is only suspected most of the time and is never clear. BUYER BEWARE: It appears that Celestron's definition of "diffraction limited" has changed recently.
>
>
>You have a defective scope. Either the mirrors are figured wrong or the corrector plate is improperly matched. Send it back to Celestron, scream, rant, and rave....and they will fix it to near perfection.
>I have owned over 60 scopes, and the only 3 with "bad" optics were all premium refractors. Two AP Travelers (YES Travelers) and one Meade 127ED. One Traveler needed to be refigured, and the other needed to have the lens remounted and re-oil spaced. The Meade needed to have an element replaced. Out of the 3 C5s I owned, all were gems!!! You were just unlucky, that's all.
>The moral of the story is...Buyer beware, no matter from whom you buy....



Belated post-postscript - Yes, Celestron replaced the optics and the scope is now (barely) diffraction-limited. While the new optics generally are unimpressive, they accassionally show some real merit, so the scope is my keeper "grab & go" scope. No, I would not buy another 5" Celestron sct.


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