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Telescope advice


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I posted this in a different forum, which may help you decide. I've removed the values as they were for a particular telescope, but you can use the formulae to see how suitable your options are:

You need to know the following:
Telescope aperture
Telescope focal length
25.4mm = 1 inch

Recommended maximum magnification for a telescope = Telescope aperture in inches x 50 (or double the aperture in mm)
Recommended magnification is aperture in inches x 25 or the aperture in mm.
This is not cast in stone as atmospheric conditions can reduce it and a better quality telescope can increase it.

Your actual magnification is your telescope focal length/eyepiece focal length
Note that a Barlow multiples the focal length by the Barlow multiplier

Having said this, you also need to be aware of how wide the exit pupil of the eyepiece is, as it needs to be the same as your eye's pupil or smaller.
Minimum exit pupil is recommended at 0.5mm, but this is the smallest and you'll probably want it larger. The suggested 'sweet spot' is 2mm.
Actual exit pupil diameter = telescope aperture/magnification

Note that the Barlow doesn't appear to be much use to you; however, the Barlow effect of multiplying the telescopes focal length is the same effect as reducing the eyepiece's focal length.
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You will get a host of different answers to this...

For visual observing, I don't find I need GoTo. I can read a map okay and if an object is bright enough to see, then it is bright enough to find. But I find GoTo essential for DSO imaging because I normally image things that are too faint to see visually. 

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That's great, thanks for the advice. I don't initially intend to do imaging but may do in the distant future once I've grasped the hobby. Just been out for an hour for a mooch about the sky, oh my days there's some stars you don't see with the naked eye.  :grin: Definitely need an upgrade rapid! Jupiter is still evading me with this travel scope!!!  :embarassed:

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That's great, thanks for the advice. I don't initially intend to do imaging but may do in the distant future once I've grasped the hobby. Just been out for an hour for a mooch about the sky, oh my days there's some stars you don't see with the naked eye.  :grin: Definitely need an upgrade rapid! Jupiter is still evading me with this travel scope!!!  :embarassed:

My son has the Celestron 70mm travel scope and regularly sees Jupiter and 4 of her moons, so it shouldn't be the scope that's limiting the view. The tripod the scope came with was useless, so I got him an EQ2 second hand for Xmas, which has made his viewing a lot better.

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Concerning the "I don't initially intend to do imaging but may do in the distant future once I've grasped the hobby." make the decision now. The "distant future" is usually 3-6 months away when you decide you want people to see what you can see.

There are weekly several people that buy a good visual scope then say "How fo I do AP with this?"

The realistic answer being "You don't! Wrong scope, wrong mount"

So yes a 200P Dobsonian will be a good visual scope, but it is not a scope for imaging in any form. For that be prepared to buy a complete new setup.

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Concerning the "I don't initially intend to do imaging but may do in the distant future once I've grasped the hobby." make the decision now. The "distant future" is usually 3-6 months away when you decide you want people to see what you can see.

There are weekly several people that buy a good visual scope then say "How fo I do AP with this?"

The realistic answer being "You don't! Wrong scope, wrong mount"

So yes a 200P Dobsonian will be a good visual scope, but it is not a scope for imaging in any form. For that be prepared to buy a complete new setup.

Good advice but if you decide you do want to do imaging be realistic about the budget. £300 will get you a reasonable visual instrument with the possibility of webcamming planets (Skymax 127) but it won't even get you started on deep sky imaging unless you make a considerable compromises to both imaging and visual observing. The best scope for visual and imaging is actually two scopes, one for each, because they have very different requirements.

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The 150p and eq3-2 for observing only application makes sense, so does the DOB. For observing only a DOB makes a very good choice. As these are all NEWRs they do need a bit of maintenace from time to time. Go TO is not necessary unless you get into imaging which is a different ball game. For about £400.00 a 200p on an EQ5 is hard to beat .

A.G

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If I knew then what I know now I would have went straight to a dob. But I didn't and my first scope was a Celestron 130SLT. It gives super views of the moon and in good seeing conditions Jupiter is spectacular. My favorite target lately has been M42. Using a 9mm EP the trapezium becomes visible.

The goto mount is pretty handy to have starting out if you don't know your way around the sky but most of the cost of the scope goes into the goto mount. If you feel like you could find your way across the sky then I would take the money you'd be spending on the expensive goto and just invest that in more aperture. 

Say an 8 or 10" dob.

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My son has the Celestron 70mm travel scope and regularly sees Jupiter and 4 of her moons, so it shouldn't be the scope that's limiting the view. The tripod the scope came with was useless, so I got him an EQ2 second hand for Xmas, which has made his viewing a lot better.

What eyepieces does he use to view?

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What eyepieces does he use to view?

He only has the 10mm and 20mm the scope came with, but I got him a 2x Barlow for Christmas. There is quite a lot of chromatic aberration with the image, so Jupiter is white with a blue top and a red bottom (or it may be the other way round), but it is still Jupiter and 4 of the moons are really obvious. The equatorial mount has made it a lot easier to track everything, once it has been polar aligned, and this isn't difficult to do.

The max magnification for the 70mm is 140 and the recommended is 70. The 10mm and 2x Barlow put it to 80, so I may get him a 6mm as well. This will increase the magnification to 130, but will also reduce the exit pupil to 0.5mm, but as the planet image quality isn't great and the nebulae and galaxies are very dull, I may decide to wait until he has a better scope. The one thing I don't know is whether to replace all the eyepieces with better quality ones or the scope may not be good enough to benefit from much more being spent on it.

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Hi Gazetilludrop. You could do a lot worse than go for a new SkyWatcher 200p Dobsonian if you're not into astrophotography (yet!). The 200p is widely regarded as the best value scope on the market. It comes with a couple of passable stock eyepieces, and will do everything you want. I absolutely love mine - its my favourite scope. They're easily sellable if you ever decide to upgrade. They're popular for a reason. Bet you there's someone at your local astronomy club that has one and wouldn't mind showing you.

You can spend lots on accessories, but for starters I recommend you consider a cheap pair of 10x50 binoculars (for example http://www.amazon.co.uk/Celestron-Upclose-Porro-Bino-10X50/dp/B006ZN4TZS/ref=sr_1_1?ie=UTF8&qid=1388626777&sr=8-1&keywords=celestron+g2 ) and a paper copy of Turn Left at Orion.

Here's to your enjoyment, whatever you set your heart on.

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If your willing to wait, check websites everyday and buy second hand you will likely get a 200p on an EQ5 within your original budget. This is what I decided to do with a £300 budget.

The 200p Dob will be fine for visual but I prefer the EQ type mounts myself. I'd echo the suggestion above to try before you buy if possible.

Goto is quite expensive and is more of a luxury. In my opinion you would get more from the hobby learning the skies than pressing a button but it would make life that little bit easier if you can afford it :)

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Each to their own regarding goto. I have it on my visual scope and love it. That said, I often push it more or less to where it needs to be and let goto finish off for me as I am getting to know the skies better. But I would echo sentiments from some of the others that a 200p ota is hard to beat. Its weather you go for the dob or EQ mount.

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You will get a host of different answers to this...

For visual observing, I don't find I need GoTo. I can read a map okay and if an object is bright enough to see, then it is bright enough to find. But I find GoTo essential for DSO imaging because I normally image things that are too faint to see visually. 

I wouldnt bother. I understand that for a noob, they're a pig to align and set up, but I can say from having been there, when you 'happen upon' an object you've been after for a while, the thrill of accomplishment is palpable. Almost flattened my scope in my exuberance when I finally bagged M57 f'r'instance... ;)

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Mate,

Consider a Celestron Nexstar 4SE.  Great no nonsense GOTO with GPS and cracking optical performance.  All for under £400 nicker.  Very good accessories to boot!

In budget and excellent (pleasurable) viewing.  Very portable, easy to deploy with outstanding optics.  Cant go wrong

Rick

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