I'm sure that every newbie and his brother has asked this on this forum, but...

What kind of scope is good for just starting out? (I've been using some borrowed 10x50 binoculars and want to save up for something NICE)...

What do I want to see? In particular, planetary and deep-space objects are a must. The moon and Sun would be pretty cool too, and binary stars as well so... everything!

From what I've been reading, a Newtonian Dob will be the best buy, so in that spirit, I have been getting opinions on a few prospective buys...

I live in a suburban neighborhood, and I have some clear nights, but there's some light pollution of course (The star across from Pegasi Β is just barely visible w/o aid...)

I'm looking at the Orion XT8 8" scope, and the Celestron StarHopper 8 8" scope... or maybe a 10?

But because of the pollution, I want to be able to move it around as well... But I've heard baaaaaad things about similarly priced cadiotropic scopes...

So, in short:

1. Orion or Celestron, aperture being equal, which is better?
2. What is a "Diffraction-limited" or "1/4 wave" scope?
3. How long are these scopes, and would they fit into a mid-size car (my car is about 65 inches wide)
4. What kind of accessories should I pick up? I think that I at least want a Barlow lens, and the Solar and Lunar filters...

1. Orion Dobsonians are most often recommended. I have never heard of the Celestron Dobs being recommended.
2. Limited diffraction probably means that there is a smaller central obstruction do to the spider.
3. Orion Dobsonians are all about 45 inches long.
4. I'm not an expert, however, I hear telrad finders are a necessity for Dobsonians.

I always find that things are larger than I think they are in a picture. A 10" Dobsonian is rather large. The main mirror and optical tube diameter are about the size of a dinner plate and the height of it including mount will come up to around your shoulders when pointing straight up. 8" Dobsonians are, of course, smaller and therefore easier to move around.

If you're going to pick up a solar filter you should also get a Hydrogen-Alpha filter as well. It brings out a lot of surface detail of the sun.

Diffraction Limited and 'wave' is how precisely the mirror is ground. Wikipedia tells me that the definition of Diffraction Limited is "An optical system with the ability to produce images with angular resolution as good as the instrument's theoretical limit is said to be diffraction limited." I believe lower wave numbers mean the mirror is more precisely ground. From what ive been able to gather its how much imperfections there are in the mirror and how large they are. I think its in relation visible wavelengths (Around 550nm +/- 200nm) so 1/4th wave should mean that there are no imperfections larger than 137.5nm (550*(1/4)). Im not sure about the whole wave thing, so I could be horribly wrong.

Edit:
I just did some more research on this 'wave' thing. I checked out a book from the library, "The Backyard Astronomers Guide" by Terence Dickinson and Alan Dyer (ISBN 0-921820-11-9, Pages 51 and 269). Its short for wavefront error. For the most part I was correct, it measures surface defects of a mirror in relation to green light (~550nm). There is no agreed upon standard for measuring wavefront error (So one company could be measuring 1/20th wave on their mirror and another company could measure 1/10th wave on the same quality mirror) and most commercial telescope makers wont tell you wave numbers because its a measure of true optical quality. The wavefront error adds up in telescopes with multiple mirrors. If both the telescopes primary and secondary mirror is 1/8th wave then it adds up to a total of 1/4th wave over the entire optical system. 1/4th wave is usually considered the minimum to achieve perfect star images. According to the book 1/4th wave means diffraction limited. From what I've been able to make out professional astronomy optics typically have a wavefront error of 1/20th or less.

there is many kinds of scopes you can get, it all depends on what you want to do with it, do you want to take up astrophotography and what is your budget. a 200 mm is not to bad , its not to heavy and takes about 5 mins or so to setup.
now if your gona do astrphoto you need a motordrive for alt and dec
and a polor alingment tool, they go for arounf 175$ or so. eather for the price you can get a a good scope for around 700$ with tripod from skywatcher maybe even cheaper, for deep space its a good scope 8 inches is good enough for deepspace the Faintest Steller Magnitude is 14.2 and Highest Practical Power 400x basically its about 50x per inch depending on the seeing ,it can go higher like 65 if the waether permits it. its a fast scope at f/5 so for planets and moon close ups its good enough.
then you could always get a wbcam and do a few pics of the planets and moon , but that all depends what you want to do with

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I owned the Orion XT8 scope for a few years and have since upgraded to the XT10. The XT10 is only slightly less portable than the 8". The mount is a little larger and heavier, the tube is as well; though it isn't much longer than the 8" tube. If you don't have any trouble moving the 8" around, IMO you should consider the XT10. Both scopes fit fine by laying the tube across the back seat in a Mazda 626 and a Subaru Legacy GT (both could possibly be considered as 'mid sized'). I don't think either of them had a 65" wide rear seat.

As far as accessories, I recommend a replacement eyepiece for the 10mm plossl that ships with the scope. The 25mm that ships with the scope is pretty good. I have the 9.5mm Orion ED-2 eyepiece, which is a nice upgrade over the included 10mm and isn't too expensive. I'd also recommend a barlow and a 7mm or so eyepiece for high power observing (when the atmosphere allows) as well as a 30 - 32 mm low power eyepiece for low power scanning. I have the Orion Stratus 30mm which is nice since it's a 2" eyepeice, you can take advantage of the 2" focuser. Speaking of focusers, I upgraded my focuser to this one: http://www.telescope.com/shopping/pr...oductID=228559. I don't know if Orion is shipping this focuser standard on the XT scopes now or not; if not, this focuser is much smoother and a lot less sloppy than the standard focuser.

I also recommend a Telrad. I use one and have since removed the standard finder scope.

There used to be an "XT users" group on Yahoo, you ought to join if it's still there. There are a lot of easy mods you can do to the XT. On mine I've done the following:

1) Telrad instead of the standard finder scope.
2) Flocking paper inside the tube
3) Plastic washers cut out of a milk jug around the bolt that holds the ground board to the mount, makes azimuth motions smoother
4) Cooling fan for the primary mirror
5) New focuser mentioned above
6) Added pads to the mirror cell to better support the mirror.
7) Verified the primary mirror clamps aren't too tight.

For the record, both the optics and the optical tube for the Celestron and XT8 are made by the same company in China. I can say from personal experience that in the past that company complained to Orion that we were being too finicky about the mirror quality when compared to Celestron (this was over other telescopes...not dobs as Celestron was not making Dobs at this point).

That same company now owns Celestron, and I have no idea if they are giving their best stuff to them to sell, but I doubt it. The company is capable of producing good stuff when motivated, but the old Celestron owners weren't giving them reason to be motivated. That may be different now, but I kinda doubt it.

As for other factors: The Celestron dob base is made in China, wheras the XT base was US made. I think that may have changed recently. Why is that important? Well, if you saw the crap bases they were sending Orion you would wonder (again they might have improved). Not all particle board is created equal folks, and China has struggled with softwood furniture tech at times (its not as easy as you might think). Even IKEA has trouble with them now and then.

The intelliscope bases were being made in the US when I left. This should still be the case.

If you want a better quality 8" Dob, albeit at a higher price, you may want to consider a Discovery PDQH. Discovery, unlike Celestron, is still an American company.

http://www.discovery-telescopes.com/discovery/pdhq.html

Dave Mitsky

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Hi all,

Thanks for your replies!

Sorry I haven't been here much, I've been ... busy.

Anyway, I have a few questions about the discovery telescopes:

1. They're about 3x as much as Orion ones, are they 3x as good as far as quality?
2. It does come with a telrad, is this a "must have"?

I do like the idea of buying something American made, but I do need to justify the price increase...

Your questions indicate you haven't even been to a local club's star parties. Do so. This will answer many of your questions and put you in a far better position to buy the right scope for you with the right accessories for you. Just because a scope and accessories are right for me is no assurance any of it is right for you. Scopes are too personal.

Also I prefer to think of a scope as an investment. Unlike your car or a can opener, it will be just as useful 50 years from now as it is today.

So my answer to the first question, is it worth it depends on how you look at the scope. The Chinese ones are quite useful but in the can opener way. They do the job and are then discarded. Average optics are fine for the beginner but as you progress you will grow to where they aren't so acceptable. You'll notice they have lower contrast even on a perfect night and on nights of poor seeing the top optics will seem to be much sharper showing much more detail than the average ones. The real difference comes years down the road. The top notch one will have appreciated, sometimes greatly, in value while the average one will have decreased greatly as there are just so many of them. I have two Cave scopes with Alika Herring mirrors. I paid $380 for the 10" f/8 tube assembly from Cave. I've been offered $6000 for that OTA with a signed Alika Herring mirror and seen them go for far more. Top quality optics are very good investments that you don't just look at in the safe deposit box!

So the answer to that question depends on what you want and expect from a scope and the best way to answer that is attend a few star parties and start to get some idea of what you want yourself, right now I doubt you really know.

As to the second question, a Telrad is a type of finder. It has no magnification or light gathering power. It displays a reticle of known size on the sky like a jet fighter pilot's heads up display. Some swear by them, some swear at them. I use one as my only finder on my permanently mounted 14 LX200R but I use that with computer control so rarely use it. It's there for emergencies like one night when the cat walked across my keyboard and managed to resync the mount to a totally wrong piece of sky!

My portable visual scopes, including those two 10" Cave's I mentioned, use both a Telrad and optical (at least 50mm) finders. I have other scopes without a Telrad at all. There are other types of finders that project a reticle on the sky. Most use just a red dot (gunsight) which, to me, is less useful. But others prefer them. Again which type is best for you, only you can answer and only after trying them in a real setting. There's that star party again. The optical finders standard on most scopes are 30mm and just too small for all but the brightest deep sky objects. Most replace them or at least augment them with something else. A Telrad is one, but certainly far from the only, option.

So find a local club and attend a star party or two to find out what you really want. No one can tell you what you want, only what they want or like.

As I keep harping on in my posts, most beginners in our club buy their scopes then attend our star parties. That usually results in what we call "The V-8 moment" when the see other equipment far better suited to them than the one they bought, often but not always, at a lesser cost. Either way it can be a very expensive moment!

http://www.astronomyclubs.com/
http://www.skyandtelescope.com/community/organizations
http://www.astronomy.com/asy/community/groups/

Rick

enigma, you should also read http://scopereviews.com/begin.html