First I would like to say that BA is without a doubt, the only site that has sucked me into a morass of non-productivity since I found fark.com. I have never really thought about astronomy much but this site has really got me curious about things.

I have absolutely no clue whatsoever about how to find things in the sky. Well I can point out orion and ursa major, but thats about it. I would like to purchase a telescope that would allow me to see as much as possible. From nearby objects to possibly deep objects.

So I am considering purchasing a telescope. I like the Meade ETX-90AT, However several people have recommended a Dob.

Here is my question. what is a preferable mount. Alt-Az, or Equitorial.

The Meade has a GoTo feature (which really appeales to me) and can be used in either Alt-Az or Equitorial. The Dob's seem to be Alt-Az only (I may be wrong).

I have found a lot of information on how to locate stellar bodies using RA/DEC coordinates, however as I understand is alt-az coordinates are rarely used in star charts.

So here is my question. What is the best mount to have on a telescope for a complete novice who would actually like to see something besides the moon?

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Eagle Eye Observatory

Short answer: equatorial mounts are more practical, but they are heavier and require setup time before you can start observing. Alt-az mounts are light (especially Dobs) and have no setup time, but you'll have to track the objects yourself. (There are dual-axis drives that can do this as well, but they also need setup, plus, they're heavy)

There are GoTo options for both kind of mounts, so pick whatever you feel like. As always, a good way to find out what kind of scope to buy is to visit an astronomy club and try out a few different kinds.

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"We do not require reality to conform to the expectations of the ignorant"

Thanks for the reply. I do not mind setup time. I live in Austin and am less than an hour from some fantastic spots for viewing the sky. I would like a scope and mount system that will take me from a completely ignorant newbie to possibly an amature with a clue. I am really being pulled toward the ETX-90AT, but I will take your advice and visit a few local star parties and then decide.

I do not want to rush into a decision I will regret later, so I am really doing my homework before making a regretible decision.

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Eagle Eye Observatory

One of the greatest things about a scope like the ETX-90 is that it is so portable, and quick to set up. That old adage, the best scope is the one you use the most, applies. You can pick it up and carry it with you easily. I used to carry one on airplanes as my carry-on. But that was pre-9/11, I'm not sure what would happen to it nowadays.

The local Asronomy club is having a stargazing event this sunday, so I am hoping to attend and pick some brains.

The more I research things, the more I am liking that particular 'scope (ETX-90AT). I should be able to get good visibility from my backyard (after they turn off the lights at the baseball field).

One other question you might be able to help with. As far as accessories go, would you have any recommendations on Eyepieces and filters? I have noticed there are light pollution filters and that various colored filters will enhance viewing of bodies. As far as eyepieces go, I am clueless. I would like to be able to see planets in as much detail as possible and even deep space bodies. any advice here?

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Eagle Eye Observatory

Plossle's are widely considered the best eyepieces (ep's) for the price. Lots of companies make them. Meade offers a set that perform very well. That said, what size you buy is directly linked to the magnification you wish to achieve. Magnification is calculated by dividing the focal length of the scope by the focal length of the ep. Hence, a 2000mm FL scope with a 40mm ep yields 50X. As far as magnification goes, you don't want to go over 50 times the scope's aperture in inches (2X in mm). Due to the principles of light, any more mag than that is just not possible (for all practical purposes). So, for the 90 you're looking at, max. mag. should be considered no more than 180X. Not sure what the focal length of that scope is though, so not sure what size ep would yield 180x.

Bottom line, magnification isn't your prime goal anyways. What you strive for is clarity. Very seldom is this achieved at high power. Most viewing is done in the 50X to 150X range. I often get my best views of Jupiter and Saturn at 76X in my 8" scope. Wally

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That's a good start. Both can be used as references to find other constellations and stars. The "handle" of the Big Dipper points to Arcturus in Bootes (three sylables -Bo-Oh-Tess) - "follow the arc to Arcturus" and Spica in Virgo - "Speed on to Spica". Orion's belt points to Sirius in Canis Major to the left and Aldeberan in Taurus on the right.
Alt-Az coordinates are location and time dependent, so they are useless for star charts. RA-Dec coordinates are time and location independent. They are the same for all observers. If I tell you that an object is at RA 5h22m, Dec +20d45m, anybody can find it (assuming it is above your horizon).
Both, neither, depends, all of the above.
A Dobsonian scope is (by definition) a Newtonian on an Alt-Az mount. Orion (among others) makes Go-To Dobs.

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T. Anderson

The Meade is a good little scope. But I agree that it is a good idea to go to an atronomy club event to try out different scopes before you buy. This is a great time to get to a star party. This is the weekend for Messier Marathon star parties, and I am sure that the Austin Astronomical Society austinastro.org(your local astronomy club) will be having an event. Usually large numbers of people with an incredible variety of instruments attend. Lets you see the pros and cons of each type.
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the ETX-90AT is a Maksutov-Cassegrain and has a focal length of 1250mm with a 90mm apeture.

So using your math, if I understand it correctly I would need a 25mm ep to achieve 50x (1250 / 50) and an 8.3 mm ep (1250 / 150) to achieve 150x?

The info I am reading on it says that maximum practical visual power is 325x

/Edit Looks like it comes with a Super Plössl 26mm eyepiece

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Eagle Eye Observatory

You're right on with your magnification calculations. The 26mm Plossl that comes with the scope will give you 48X. An ep around 12mm will give you 100X.

The "practical" limit of 325X is what is known as "diffraction limit" of the scope and really only applies if you were using the scope on the moon (or anywhere without a turbulent atmosphere!). The "2 time aperture" rule is pretty steadfast. Again, don't get too caught up in magnification. The key is to find the mag. that gives you the best image. That is rarely above 200 to 250X or so, even in bigger scopes.

the Meade 4000 Super Plossl's (which the 26mm that comes with that scope is one of) are held in pretty high regard for their price. I've got several of them, and have no complaints whatsoever.

If you want a cheaper alternative to a scope, lots of us started out with a good pair of binoculars. These are a great investment, as the wide field of view can't be matched by any scope. I've got a pair of 10x50's from Orion that I love. They come out with me every time. (the "10" is the magnification, and "50" is the combined aperture of both "tubes"). You'll be amazed on what you can see with binoc's. It's a great way to learn the sky.

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. . . My moustache is touching my brain!!!!

Well, I have binoculars They aren't fantastic, but they work. I feel I'd like to just jump in with a scope. As far as learning the sky goes, I have found a really good link here. And with the software available and making sure I have a GoTo on whatever scope I buy, I'll do ok I believe. I am just trying to noodle out the details for what EXACTLY I want to get.

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Eagle Eye Observatory

Are you sure about that? I was pretty sure the 50 was for each lens, so the combined aperture would be sqrt(2)*50?

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GhiaPet Home Page

The '50' is per tube.

skrap, you'll change your tune once you get a decent set of binoculars. Don't discount the possibility that your current attraction to astronomy is the equivalent of a crush...you have yet to know whether it is true love. A good book (I recommend Philip Harrington's 'Touring The Universe Through Binoculars'), a decent set of binox (I'll assume you're at least a hale and hearty teenager of normal stature, so 10x50's are a good start -- www.telescope.com and www.bigbinoculars.com are excellent sources), a cheap lawn chaise lounge, an army blanket (it gets cold on occasion), some bug spray, and a couple months of observing are enough to determine whether you've got a mild interest or that deep feverish desire. Put that time in before you drop lotza bux on a scope. Besides, you'll have learned the sky, there will have been opportunity to try out other folks' scopes/eyepieces/filters at your local astro-club, you'll have picked your fellow stargazers' brains on numerous occasions, and you won't have wasted your money in error.

Trust yer ol' Unca Charlie on this one...these are the mistakes we have all made over'n'over'n'over'n'over again, and we don't want you making the same ones.

Binoculars have nice wide fields of view that work well on seeing entire star fields of Messier objects, yet provide more than enough magnification to see the Moon. In addition, there are things you can do with binos that are tough to do with scopes. Ask anyone who's tried tracking a satellite or the ISS with a scope. But I've done it a couple times with binos...it's yer basic cheap thrill. And it's easier to transport/set up a book, a pair of binos, and a lawn chair, than it is a scope.

Yes, you've already got a small case of aperture fever...the immediate shock cure is a dose of reality. If it turns out that this hobby really isn't your heart's desire, it's one heckuva lot easier to get your money back out of a pair of binoculars than it is a secondhand scope. Sorry to be so chillingly pecuniary, but the truth is cold.

Thus endeth this channeling of The Voice Of Experience...

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Charlie in Dayton, A.AsC.

Personally, I have an 8" Celestron Nexstar with all the bells and whistles on an equatorial mount. Good scope, good mount, good exercise!
-Kevin

scrap, ol boy, the Charlie guy is not steering you wrong. Binoculars are way cool. I have a fancy scope, and love lookin at stuff with it, but listen to the others: "Good scope, good mount, good exercise! " They arent kidding. This subject comes up regular like clockwork. Setup is THE problem for travel setups. If you live an hour away from the site you want to observe from then your are at least three hours away from good peeping. ( cool down, alignment, etc.....). Lets ask a fellow board member how he is enjoying wonker aperature. (I know that an etx is a good grab 'n go)

I think I am going ot have to attend a few star parties. theres a great spot I heard about where locals meet every friday.

I went to an asrronomy store and looked. I am now leaning heavily on an Orion Dob with a computer.

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The More I learn, The More Ignorant I Become

Eagle Eye Observatory