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Help with telescopes


Deadpangod3

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So with a large stash of Christmas and birthday money, I decided I wanted a better telescope then the telestar model 60az-a I already have, my current telescope let's me see Saturn's rings and Jupiter's moons. :) I told my mother I wanted one that allows me to see features on mars like the icecaps and such, and is able to auto track objects in the sky.

she showed me a couple with this being the best one:

http://www.telescope.com/catalog/search.cmd?form_state=searchForm&siteCode=US&keyword=celestron+nexstar+130slt

 

However I have zero knowledge of telescopes, other then how they all work with mirrors and how to use the one I have (read an online instruction manual for nearly an hour before I figured it out) as I obtained mine last year from my brother who hasnt used it since he was little.

So what i'm asking is if you can educate me a bit on all the stats for these telescopes and what they mean because i have zero idea :P

The two main questions I have are 1. When you refer to a telescope being like 30 mm (Mm? MM?) Is that like a measerment of the width of the front lense and basically how distant it can show objects?

The other being are my expectations for a telescope too high? :PP

Any help is apreciated.

Edited by Deadpangod3
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The usual number is the objective diameter. This is the size of the front lens on a refractor, or the primary mirror on a reflector. This determines both the angular resolution of the telescope, and the amount of light it gathers. The smaller mm numbers are generally for the eyepieces, larger is wider field for eyepieces.

Resolution is how fine you can see details, say 2 stars VERY close together, with the naked eye they might appear as a single star, and with a telescope 2 are clearly visible. This eventually becomes limited by the atmosphere, though, without advanced systems like adaptive optics to mitigate it somewhat (something you see on research telescopes in observatories).

Light gathering is how dim you can see... a telescope is a bucket to collect photons, a wider bucket will catch more. Generally speaking, bigger is better.

Tracking is certainly a nice feature, and some can be controlled via bluetooth now from apps as well, but it comes at some cost. Some people chose simpler mounts like dobsonians to spend more money on the glass (bigger scope, but it's less complicated). You can get a fairly big dobsonian (8" (~200mm) for under $500.

For planetary viewing, refractors are actually better. Look for a 3-4 inch (75-100mm) achromatic refractor in that sort of $500 price range if that's what you want. Still, a big reflector will do OK as well.

Where do you live? Not specifically, more like, is it suburban/rural with dark skies, or is it near a city with a lot of light pollution, etc?

 

 

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9 hours ago, tater said:

The usual number is the objective diameter. This is the size of the front lens on a refractor, or the primary mirror on a reflector. This determines both the angular resolution of the telescope, and the amount of light it gathers. The smaller mm numbers are generally for the eyepieces, larger is wider field for eyepieces.

Resolution is how fine you can see details, say 2 stars VERY close together, with the naked eye they might appear as a single star, and with a telescope 2 are clearly visible. This eventually becomes limited by the atmosphere, though, without advanced systems like adaptive optics to mitigate it somewhat (something you see on research telescopes in observatories).

Light gathering is how dim you can see... a telescope is a bucket to collect photons, a wider bucket will catch more. Generally speaking, bigger is better.

Tracking is certainly a nice feature, and some can be controlled via bluetooth now from apps as well, but it comes at some cost. Some people chose simpler mounts like dobsonians to spend more money on the glass (bigger scope, but it's less complicated). You can get a fairly big dobsonian (8" (~200mm) for under $500.

For planetary viewing, refractors are actually better. Look for a 3-4 inch (75-100mm) achromatic refractor in that sort of $500 price range if that's what you want. Still, a big reflector will do OK as well.

Where do you live? Not specifically, more like, is it suburban/rural with dark skies, or is it near a city with a lot of light pollution, etc?

 

 

I live in a small town where I can see a lot of stars at night and if I look very closely I can see what I think is the Milky Way, I can also see most of the planets when their above the horizon. :P

So the larger the telescope the better I guess?

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You should read up on the differences between refractor and reflector telescopes. Generally speaking, I'd suggest a dobsonian, though it lacks the tracking functionality, and requires you to just point and look. You can get pretty good at this after a while. I of course really see the value in a clock drive with the computer control, though. A lot depends on how you see yourself using it. 

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In my view the most important thing is ease of use. That comes primarily from the mount, which needs to move when you want it to and stay still when you don't! Remember 50, 100, 200 times magnification means every little shake is also magnified 50, 100, 200 times. If you buy a Newtonian reflector, where the eyepiece comes out the side of the tube, then I advise an alt-azimuth mount, one where the scope points up and down, left and right. Newtonian reflectors on equatorial mounts tend to point the eyepiece in stupid directions as you move the scope around. If you're considering a computerised "GoTo" scope, you also need to think about how easy it is to get set up and use the computer control, as well as battery life - you're usually best off with a rechargeable battery pack because most of them guzzle batteries otherwise and the scope can't be aimed manually without damaging the mount. Also consider size and weight, it's not much good having a telescope that's just too darn big and heavy to drag outside.

The next most important thing is aperture, the width of the main lens or mirror. More aperture means seeing fainter objects and more detail. Useful maximum magnification is 50x per inch of aperture, but know that most observing is done at low and medium magnification anyway. A 3 inch scope will show the basics. 4 or 5 inches is better, but still considered a small scope. 6 or better 8 inches and you're into "large telescope" by amateur astronomer standards. 10 inches and above starts to get heavy, bulky, and expensive.

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Yeah, my gut says a bigish dobsonian. I have seen packages for around his budget (mid-$400 up to $500) that come with everything, and have an 8 inch objective. 

I had a small refractor as a kid---it was in the house, and one night I found out we had it, and took it outside... what a surprise! I had no idea what I was looking at, I just pointed it all over, and when I saw something interesting, it was a feeling of discovery.

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I found a classic Celestron Super C8 last year on Craigslist for $300.  It came with everything but eyepieces.  It was about $1400 new in 1981.  One heck of a nice scope with great optics and great form mount with drive.  

For someone new, I would recommend a used, but nice scope without "Go To".  Just get one with a drive that will track the sky after being polar aligned.  That way, you will learn how to find objects by starhopping and using charts/books.  That is something you will not learn using a goto scope.

 

Check the classifieds at Cloudy Nights for used scopes and accessories and to see the market value of used scopes.

 

Most scopes sold today are junk, or are way more expensive that $500.  Look for a Dobsonian, SCT, or Newtonian in the 6" to 10" range.  Your budget should be large enough to get you some pretty large aperture.

 

Good Luck!

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Great advice here. I have an Orion very similar to what you are looking at. I also have an 8" Dobsonian. The Dob is definitely easier to set up, and slowly slewing by hand becomes second nature rather quickly. It is kind of big when hauling in a car. I will say, finding objects is a steep learning curve much like learning KSP. Avoid an equatorial mount. They are extremely frustrating to learn. I trashed mine. Alt/Az is so much easier. GOTO is nice once you get it level and aligned (different every time you use it). The Orion doesn't gather as much light and is more limited on magnification than the dob but honestly in our viewing conditions both work well. I think you would be happy with the 130. Just know it is not a planet killer. As mentioned, you need a good refractor for that. The trade off is the field of view is extremely narrow, limiting how much sky you see at once. Many deep sky object are surprisingly pretty big. All that said, my personal favorite way to observe is a decent set of binoculars. Mine are Oberwerk 15x70, so the lens is bigger than your present scope. This is at (or over) the upper limit of what most people can use hands free. When I want a steadier view I mount it on a tripod. Scanning the Milky Way is way fun with binos.  Quick scan on Amazon prices these at $159. I paid $99 back in the day. Finally, the best advice I can offer is find a local stargazer club and attend a star party or two. You'll get to look through several scopes and see for yourself and learn a lot from the experience.

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So I read the wikipedia pages (or part of) about refractor and reflector telescopes and from what I gathered, the difference is one can make images blury, and the other needs to be larger to get the same size but is sharper? Correct me if I'm wrong.

Also I dont know if I'm not seeing anything in the thread, but what's a Dobsonian? I'm rapidly typing this in before bed and can't Google it ATM

Also, I can tolerate still having to manually point the scope, I mean, it'd be nice to have it be able to stay pointed at what I'm looking at by itself but its not an absaloute neccesity.

The entire reason I'm getting a new one is primarily to be able to see Mars's icecaps and other features, because in my current scope it only shows as a reddish dot 

Sorry if I completely misread everying thing in this thread and now sound like an idiot 

I got completely stumped with the "equatorial mount" and  things, I admit I'm not the best at understanding things.

Also last year there was some astronomy events I went to and the guy had a gant telescope on a wheel base that let us see things like the ring nebula and some globular clusters as blurry dots but i think it had a wider field of view.

 

Edited by Deadpangod3
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Why did you attribute the above quote to me?

Dobsonians are a very simple mount system. 

220px-Red_dobsonian.jpg

They allow changes in altitude (vertical), and azimuth (horizontal rotation). Equatorial mounts align the part that rotates with the equator, then can have a motor that counter-rotates the telescope so that it remains pointed at the same spot in space as the earth rotates. The one your mom suggested is a slight equatorial variant with a motor on both axes, and the computer uses your a setup algorithm to determine your position, and then it moves the scope as needed in both directions to counter the earth's rotation.

Refractors vs reflectors is complex. Bottom line is that at the same aperture, refractors are going to be better for planetary observing. Generally speaking, I think a reflector is probably a better bet for you. The one you linked is fine, and a dobsonian would also be fin---and for the same money, it would be bigger (bigger is better), but it lacks the perks of clock drive, etc.

Here's a dobsonian to look at:

http://www.telescope.com/Telescopes/Dobsonian-Telescopes/Dobsonian-Telescopes-with-Free-Shipping/Orion-Limited-Edition-SkyQuest-XT8-Classic-Dobsonian-Bundle/pc/1/c/12/sc/398/p/101452.uts?refineByCategoryId=398

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odd, aparently the forums on mobile put what i typed into a quote, strange, will fix.

so Dobsonians are the mount things on some telescopes, the one at the stargazing event I went to last year had a mount like that :)

Ill take a look at that telescope, thanks :)

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Another picture of a Dobsonian:

XT8intelliscope366500.jpg

And this is a Newtonian reflector, same aperture I think, on an equatorial mount:

post-3933-14073284792888_thumb.jpg

The equatorial mount has its advantages, but you can see how overall more cumbersome it might be.

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This is a 6" with a computer control, but still dobsonian mount:

http://www.telescope.com/Telescopes/Dobsonian-Telescopes/IntelliScope-Dobsonians/Orion-StarBlast-6i-IntelliScope-Reflector-Telescope/pc/1/c/12/sc/27/p/102026.uts?refineByCategoryId=27

Slightly larger than the Celestron you linked, but basically the same features in a more compact mount.

 

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So I've decided that this one http://www.telescope.com/Telescopes/Dobsonian-Telescopes/Dobsonian-Telescopes-with-Free-Shipping/Orion-Limited-Edition-SkyQuest-XT8-Classic-Dobsonian-Bundle/pc/1/c/12/sc/398/p/101452.uts?refineByCategoryId=398 is the best of the ones I've looked at, but is 64x magnification good enough for seeing detailed views of mars?

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Not really. But all good telescopes take standard interchangeable eyepieces, so you can buy additional ones, and most amateur astronomers acquire a collection to cover various magnifications and tasks. With an 8-inch Dobsonian 200x shouldn't be a problem. More is possible, but it can get tricky to keep nudging the scope.

Mars is in any event one of the most difficult targets, bear that in mind. Sketches like this one give you an idea of what you might get:

 

img2009121401_MarsUFlg.jpg

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Magnification is going to be the focal length of your scope (1200mm for the one you linked) over the eyepiece focal length. The specs for that scope say the best  useful magnification is 300X, which is a 4mm eyepiece for that scope (1200/4=300). 2" eyepieces are better, but more expensive. The nice thing is that you can keep eyepieces to use with whatever telescope. They'll get expensive with quality, it's like buying lenses for cameras.

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For a typical 8-inch Dobsonian a good eyepiece lineup would be something like so.

Low magnification. About 30mm, giving about 40x. Use for finding all things, and viewing larger deep-sky objects. The scope you linked has this covered well with both its eyepieces.

High magnification. About 200x, which means a 6mm eyepiece. Use for viewing planets in good conditions. This is one I think you should buy, at least if you want to look at planets, and I suggest a wide angle eyepiece with good eye relief. Wide angle means less needing to nudge the scope, while eye relief is how close your eye needs to be to the lens - too short and it's uncomfortable to use. If your eyes have significant astigmatism and you want to wear glasses while observing then eye relief is especially important because you need space for your glasses between eyepiece and eye.

Then some in-between magnifications. The Barlow lens included with the scope you linked will double the magnification of any eyepiece and that will give you 70x and 100x which are good for most deep-sky objects and for seeing the whole Moon at once. Barlow lenses give mixed results though, sometimes they work well but often they give poor quality views.

100x to 200x is a bit of a gap, and depending on what you observe you might want to fill it in future. Then again, you might be fine.

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And the 2' mount lenses will generally give better eye relief. The only real issue become cost... It's like you're buying a DSLR camera body that comes with a general purpose lens... if you want a good image stabilizing lens for your camera, the glass will cost more than the camera did.

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The barlow on this is a 1 1/4" so it can only be used with 1 1/4" eye pieces. I tend to like a 12mm ep with the barlow to get the equivalent of a 6mm, although more glass between you and the mirror can mean poorer viewing. To me the ease of viewing makes it a good trade. The smallest plossl eyepiece I am comfortable using is a 9mm. With the barlow that is 267x That's about the limit most nights around here anyway. 

Nice scope by the way. 

 

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4 hours ago, tater said:

And the 2' mount lenses will generally give better eye relief.

The big benefit of 2" eyepieces is the larger field stop permits a wider true field of view. That means they tend to be most useful in the longer focal lengths, while shorter focal lengths are fine with 1.25" eyepieces.

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On 4/16/2016 at 4:49 PM, Red Shirt said:

The barlow on this is a 1 1/4" so it can only be used with 1 1/4" eye pieces. I tend to like a 12mm ep with the barlow to get the equivalent of a 6mm, although more glass between you and the mirror can mean poorer viewing. To me the ease of viewing makes it a good trade. The smallest plossl eyepiece I am comfortable using is a 9mm. With the barlow that is 267x That's about the limit most nights around here anyway. 

Nice scope by the way. 

 

whats barlow?

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A Barlow lens. It goes into the focuser and then the eyepiece goes into it, and it increases the magnification. Combined with a suitably-selected set of eyepieces, a Barlow will increase your magnification options for less money.

Good Barlows *just* increase the magnification. Bad ones increase the magnification and make the view look like rubbish. So keep that in mind.

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whats barlow?

http://www.telescope.com/Accessories/Barlow-Lenses/Orion-Shorty-125-2x-Barlow-Lens/c/3/sc/41/p/8711.uts

Simply put a piece of glass between the eyepiece and the mirror that in this case doubles the magnification. The odd thing here is orion includes one 2" eyepiece that cannot be used with the shorty barlow. Maybe the 2" ep has a 1 1/4" adapter. Didn't look that close. If not you'll have save the shorty for another day.

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