Telescope advice

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Telescope advice

Postby rhys_k » Sat Jun 27, 2009 12:10 am

I'm looking to buy a telescope and can't decide between 2 telescopes, the telescopes are the Skywatcher Explorer 150PL on the EQ3-2 mount(£300) and the Skywatcher Explorer 200 on an EQ5 mount(£420). I would just like to know if the visual difference between the 2 scopes is worth the extra money, also would it be better to buy the 200 with the EQ5 mount now rather than buy a new mount later?. Portability/Weight is not a problem for me.
Thanks.
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RE: Telescope advice

Postby philipc » Sat Jun 27, 2009 8:46 am

[quote]I would just like to know if the visual difference between the 2 scopes is worth the extra money[/quote]

I'm no real expert, but this question is pretty straightforward, since both scopes are well-regarded and easilly compared.

The 200mm gathers over [u][i]fifty percent more light[/i][/u] than the 150mm as follows:

(150mm*150mm) / (200mm*200mm) * 100 = 56.25% more light-gathering ability.

So if portability/weight is *genuinely* not an issue, then the 200mm is the clear choice, and the standard rule is "always go with the sturdiest mount you can afford."

Also, don't forget that you'll want to buy additional eyepieces in future if you haven't already got some - and eyepieces are very expensive.
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RE: Telescope advice

Postby ronin » Sat Jun 27, 2009 6:13 pm

The gathering is as said the ratio of the squares of the 2 mirror radai or diameters. But it is (200/150)**2 so is 1.77 times as much light gathered by the 200 as by the 150, not 1.56. Even better.
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RE: Telescope advice

Postby philipc » Sat Jun 27, 2009 11:13 pm

[quote]The gathering is as said the ratio of the squares[/quote]
Yes - I got it the wrong way around (apologies)
My maths shows how much [i]less [/i] light gathering the 150mm has relative to the 200

Ronin's is the correct formula to use.
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RE: Telescope advice

Postby ronin » Sun Jun 28, 2009 10:20 am

GB: When I looked at it I had to think twice, then write it down. I find I do the same as you did many times, looking at getting a 72mm to back up the 90mm I have. Have to think twice when the 72 comes out as getting more light then the 90. [8|][8|]

It is too easy to picture the equation as (R1**2/R2**2) and put the small scope as R1.[:@][:@]

Then oddly I cannot use the 1/x key to simply invert, I have to go through it all again.[:D][:D]
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RE: Telescope advice

Postby rhys_k » Mon Jun 29, 2009 6:50 pm

I went to a Telescope shop today and the shop assistant there suggested another scope for me to look at. He suggested the Celestron C6-NGT which is a 150mm Newtonian on a GOTO GEM mount. I was wondering if the quality of the Celestron was similar to the Sky-Watcher. Would this mount be strong enough if I wanted to upgrade to a 200mm in the future?
Thanks.
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RE: Telescope advice

Postby philipc » Mon Jun 29, 2009 11:50 pm

In case you didn't already know, Sky-Watcher and Celestron are both part of the same parent company now.

At the cheaper end of what the companies produce, there's probably not much between them, and some individual component parts are almost certainly identical units used by both companies.

At this level, you're not likely to get a [i]significantly [/i] better product than the Sky Watcher ones at the same price - so it's not really worth agonising over.

When it comes to eyepieces however, people seem to go for brands other than SkyWatcher - whether that's fair or merely based on predjudice due to the low-grade ones that come with their scopes, I can't say...

Bear.
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RE: Telescope advice

Postby stephen bastyan » Tue Jun 30, 2009 2:16 pm


[quote]ORIGINAL: rhys_k

I went to a Telescope shop today and the shop assistant there suggested another scope for me to look at. He suggested the Celestron C6-NGT which is a 150mm Newtonian on a GOTO GEM mount. I was wondering if the quality of the Celestron was similar to the Sky-Watcher. Would this mount be strong enough if I wanted to upgrade to a 200mm in the future?
Thanks.
[/quote]

The GT designates GoTo so if you want a computerised telescope this is the one to go for. Celestron sell the CG-5 GoTo mount with an 8" telescope (and bigger) on so yes it can be upgraded later if you wish. With the 6" it is still fairly portable. You will find the Celestron CG-5 mount slightly superior to the SkyWatcher as it has ball bearing on both axis, and 2" steel legs (as sold with the EQ-6).

The C6-N GT is great value currently as you can save £211.00 in the Celestron Spring Sale ....
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RE: Telescope advice

Postby sxinias » Wed Jul 01, 2009 4:56 pm

I have both Skywatcher and Celestron products which as someone said are owned by the same company. Both are good but the Celestron seems a little more refined as if that's worth anything ... less issues such as loose nuts, etc., superior shippment packing, better manuals, etc. but where the rubber meets the road, I suspect similar products between the two companies are very comparable.

None of us can tell you which telescope to purchase. Telescopes are rather personal. What pleases one person is unacceptable to another.

If you can afford 400+ pounds, it seems to me that your choices are between the Celestron C6 NGT amd the SkyWatcher Explorer 200 on an EQ5 mount. If you live in a light polluted area, a GOTO mount is almost, if not, a requirement if you want to see much at all. If the Computer GOTO is more attractive than the advantages of extra aperture, then choose the C6. If you have dark skies and star hopping and seeing as much detail as possible are more important take the Explorer 200. SkyWatcher will be veery happy to sell you a GOTO conversion kit if later on you decide you want one. At 25 kilograms or so, while transportable, neither one of these two telescopes will be grab and go. If 300 or so pounds is your limit, then the Skywatcher Explorer 150PL on the EQ3-2 mount. However, SkyWatcher you may want to consider the SkyWatcher SkyLiner 200P 8" Dobsonian that goes for 300 pounds if you want the most aperture for the money and tracking is not important.

BTW, the CG5 mount is solid as a rock, a definite overkill for the C6, and is used by Celestron for larger scopes. With the C6 it should be solid enough to allow you to do some serious astrophotography if you should ever want to go that route.

If you go with the 150 mm SkyWatcher and later want a GOTO capability, you may be able to put it on the SkyWatcher SynScan Alt/Az GOTO Mount. I've put a Celestron C6S SCT on one. The mount takes the weight and aperture with no problems and probably can take more than the 5 kg C6S but not more aperture. However, the mount's lightweight tripod is definitely at or past its limits. The combination is a nice grab and go viewing scope with sufficient aperture to really start seeing some details but obiviously not as much as with a 200mm scope.

Like you, I thought that the size and weight of a larger scope would not be an issue until I noticed my C6S seldom got used and my smaller Meade 2045 SCT on a DS2000 goto mount remained my workhorse. The little 4 inch Meade SCT was so easy to grab in one hand and out the door to a dark spot, set up and start observing especially during the late spring and early summer with is short nights. Since I do no photography at the moment, the rock solid CG5 mount offered me little. I put the C6S on the SkyWatcher SynScan AZ GOTO mount and now my little Meade sits in a corner waiting for my grandson to age a little more. My CG5 mounts waits until I've mastered the some more astronomy skills as I do want to attempt to photograph some of the objects I'm seeing.

Joe

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