First time telescope buyer, need educated advice.

[Arcane]

Hey guys, I have never owned a telescope, but I have always wanted one and this Christmas I am going to buy myself one. The thing is I want to make sure I get something that will allow me to see faint objects in crisp detail without also making me see an empty wallet.

So I am looking at this refelector dobsonian telescope. SkyQuest XT8 Classic... details here http://www.telescope.com/control/product/~product_id=09707/~category_id=classicdobs

Is this a great telescope? I know its on the lower end price wise, but will it get me some great views of planets and galaxies?

Also, what sort of lenses do I need to get started out on the right foot? It comes with two lenses, but are they any good? I also need to buy a Barlow lense correct? Any special brands to get or stay away from?

Any input is greatly appreciated!

Thanks.

[RickJ]

Many have found it a very good starter scope. For the bucks it is a very good buy.

Yes the eyepieces are usable starters compared to many. They are inexpensive Plossls but even inexpensive plossls perform quite well. They give you a rather good low and medium power. You may eventually want to go with better ones with a wider field of view but they do work well with the scope. You might want to next add a barlow to turn the 10mm into a higher power eyepiece. While technically the scope will go to 400x, it is likely this will be very rare as the earth's atmosphere often says "NO WAY!" I'd shoot for around 300x for your higher power and use a barlow to get there rather than a real short focal length eyepiece. Those are expensive with a reasonable eye relief compared to using a barlow and simple plossl to do the same. I'm not a fan of Orion's Shorty barlows however though I haven't used one recently and they may be better now, I just don't know. For the money and if you don't use super wide field eyepieces that cost more than the scope I like the Klee barlow.
http://www.universityoptics.com/barlows.html
Though with the two eyepieces they provide the 25mm becomes a 9mm thus about duplicating the 10mm you have. Though with much better eye relief if you use glasses.

Add money for a star atlas, red LED light to read it, binoculars if you don't already have some and warm clothes if you live where winter resides. It's -25C as I type this here. Burnham's Celestial Handbook, 3 volume set, will give you a good starting point of what to look at. Everything in it is fodder for this telescope.
http://www.tower.com/tower_search/search_1.cfm?keywords=Burnham's%20Celestial%20Hand book

I highly recommend finding a local astronomy club and attending their star parties and meetings. You have a steep learning curve ahead and a good club can go a long way to making it bearable.
http://www.astronomyclubs.com/
http://www.skyandtelescope.com/community/organizations

Rick

[Arcane]

Thanks for the reply and the input. I have another question if you don't mind.

I noticed on that website for the Klee barlows there is a 2.8 and 2.2 version both are 1 1/4". WOuld I get a better/clearer view going with a lower magnification? i.e. the 2.2 VS the 2.8?

Also, there is a 2" 2X ED Barlow on that page. Would I be better off getting a 2" barlow for a wider FOV? Or at least a bigger picture of what I am looking at.

I am going to go ahead and order the telescope, but I am going to keep shopping for Barlows untill I figure out exactly what is best.

Thanks for the input!

[RickJ]

A barlow's power narrows the actual view because the power is increased but the apparent field of view, about 50 degrees for the Sirius Plossls stays the same. A barlow is used to raise power and keep eye relief the same so you get two powers from each eyepiece not 1. Since the field is smaller than before the only thing that gets larger with a 2" barlow when used with 1.25" eyepieces is the hole in your wallet.

You need a power near 300 as that is lacking. the 10mm at 2.2 would be the same as a 4.5mm plossl but with the eye relief of the 10 rather than the much shorter eye relief of a 4.5mm eyepiece. It would give a power of about 264x. The 2.8 would give about 336x.

If you do much deep sky viewing of emission nebula and planetary nebula you will want to add a UHC type filter to the list of must haves (Ultrablock is another name). Then later add the OIII (everyone calls it that) for even higher contrast on some of these objects. I forgot this in my first post.

Rick

[Arcane]

So you are saying a 2" barlow is a waste of money? One would think that the bigger the viewing area the better the picture, I mean a 2" picture of an object seems like it would be better than a small 1.25" picture. But I guess that is not how it works?

It would be great if the viewing area was the same as the telescope diameter with a 12" dob it would be like watching it on TV heh, but I guess that is not possible.

Ok, so I should go with the 1.25" Klee instead of the 2" cheaper brand. Alrighty then.... Thanks a lot for the help.:clap:

[Kaptain K]

It would be great if the viewing area was the same as the telescope diameter with a 12" dob it would be like watching it on TV heh, but I guess that is not possible.
You are confusing linear size with angular size (apparent field of view). A typical Plossl has a FOV of about 50 degrees, which is pretty close to the size of a TV at normal living room distance. 12 inches at the same distance is actually rather tiny.

[Dave Mitsky]

So you are saying a 2" barlow is a waste of money? One would think that the bigger the viewing area the better the picture, I mean a 2" picture of an object seems like it would be better than a small 1.25" picture. But I guess that is not how it works?


A 2" Barlow lens won't provide any larger true field of view with a given 1.25" ocular (and a 2" adapter) than a 1.25" Barlow lens will. The difference is that you'd be able to use 2" eyepieces, which have the capability to provide larger true fields of view than 1.25" eyepieces, with the 2" Barlow.

Burnham's Celestial Handbook is a classic but dated work. There are many more useful observing guides available, particularly for beginners. Terrence Dickinson's Nightwatch is generally considered to be the best. Phil Harrington's Star Watch is very good as well. The best deep-sky object observing guide currently on the market is The Night Sky Observer's Guide (http://www.astromart.com/articles/article.asp?article_id=283).

Dave Mitsky

[RickJ]

So you are saying a 2" barlow is a waste of money? One would think that the bigger the viewing area the better the picture, I mean a 2" picture of an object seems like it would be better than a small 1.25" picture. But I guess that is not how it works?

It would be great if the viewing area was the same as the telescope diameter with a 12" dob it would be like watching it on TV heh, but I guess that is not possible.

Ok, so I should go with the 1.25" Klee instead of the 2" cheaper brand. Alrighty then.... Thanks a lot for the help.:clap:

By that reasoning a 8" scope has a wider field of view than my 7x20 binculars yet they have a 9 degree FOV and your scope with that 25mm eyepiece will have about a 1.2 degree field of view.

Remember your eyepiece is 1.25" in diameter. Putting a larger barlow in front of it can't possibly change that. Without a barlow you will see the whole moon with a 25mm eyepiece. The image the scope forms of the moon is smaller than the inside diameter of your eyepiece so you see it all. Add a 2.8x barlow, no matter the size, and the moon will now be 2.8x larger and thus too large to fit in that 1" hole (assuming 1/8" walls). You can't see it all. A larger barlow won't help one iota, the image scale is the same whether it is a 2" barlow or a 1.25" barlow. In either case the moon is exactly the same size, that is, too large to fit and you'll see only part of the moon but at higher power depending on the barlow's "power factor". Match the barlow diameter to the eyepiece diameter. Larger gains nothing as I said earlier.

This mistake and likely many others you are making or will make are quickly erased by a session or two at a local club's star party. You can see what happens when you try these various things and thus avoid the costly mistakes nearly all beginners, who don't go this route, make.

If you are looking at a 2" barlow and it is cheaper than the 1.25" then it is very likely much lower quality with far less color and aberration correction. Larger lenses of the same quality cost more and the cost goes up with the square of the diameter in most cases. I've seen some 2" barlows with lenses no larger than those that would fit in a 1.25" tube. Since 2" is less than twice 1.25" and most are at least 2x they lose no field of view doing this! It's done only to fit 2" eyepieces.

What is the secondary size in the scope you are looking at? I don't see it given in the Orion catalog. Most 8" f/6 scopes use a secondary SMALLER than 2" yet the light cone is larger at the secondary than at the eyepiece. If so, you couldn't begin to fully illuminate a 2" eyepiece or barlow. Larger secondaries reduce image contrast but increase the fully illuminated field of view so secondary size is a trade off. Most makers choose about 1.85" for the secondary in a scope of your size. To fully illuminate a 1" field of view at 6.5" from the secondary you'd need a 2" secondary. So it is likely this scope won't even fully illuminate the field of view possible in a 1.25" eyepiece. Though the loss at the edges would be too little to notice that wouldn't be the case with a 2" eyepiece! Yet another reason to stick with 1.25" eyepieces and barlows.

Rick

[Arcane]

Ok, thanks for the input guys, realy appreciated.

I wasn't implying a 2" would give a wider FOV, or wasn't trying to imply that even though it may have come off that way, I was just thinking that the picture would be bigger. Kind of like watching a 65" TV vs. a 32" TV, you see the same picture (FOV), but it is just bigger on the 65" TV.

I will definately take your advice and stick with a good 1.25" Barlow though. I'm going to grab the Klee that you suggested Rick.

Thanks!

[Dave Mitsky]

The Klee is a fine Barlow lens. If you'd like to step up to an even higher, but much more costly, level of performance, consider a 2.5x Tele Vue Powermate, which is parfocal and doesn't cause vignetting or exit pupil throwout.

http://www.televue.com/engine/page.asp?ID=42

Dave Mitsky

[Arcane]

I found a televue 2.5x barlow for $170 on amazon.com but that is a bit out of my price range at the moment, but thanks for the suggestion.

I did have another question though about the Klee's. I am not sure whether to get the 2.8x or 2.2x. The 2.2x is more expensive, but it seems like it would be better for planet and moon viewing because it would allow for a brighter picture right? I know the more you increase magnification the dimmer the object gets. Of course I guess that depends on the size of the EP as well.

Everything I have read about it online suggests the 2.8 is the way to go, but not knowing how old most of these reviews are may suggest that the 2.2 was not even available at the time.

I dunno, I guess I will go with the 2.8, it should be just fine and its a bit cheaper than the 2.2.

[Kaptain K]

I was just thinking that the picture would be bigger. Kind of like watching a 65" TV vs. a 32" TV, you see the same picture (FOV), but it is just bigger on the 65" TV.
You are confusing true field of view (FOV) with apparent field of view (AFOV).

A barlow affects FOV - the higher the magnification, the smaller the FOV. It's like watching football on TV. They show you the whole field, then they zoom in (barlow) to show the snap.

AFOV is inherent in the design of the eyepiece. A typical Plossl is about 50 degrees. An Erfle (the original "wide field" eyepiece) is around 70 degrees. Modern wide field eyepieces are around 80 degrees. The ultimate "window on the universe" is the new 100 degree Nagler Ethos which will set you back over $600! :eek:

[RickJ]

I wasn't implying a 2" would give a wider FOV, or wasn't trying to imply that even though it may have come off that way, I was just thinking that the picture would be bigger. Kind of like watching a 65" TV vs. a 32" TV, you see the same picture (FOV), but it is just bigger on the 65" TV.
Thanks!

Apparent field of view is what you are talking about. That is determined by eyepiece design. A barlow can't change that. To double the diameter of the apparent field of view of a Plossl you'd have to buy and Ethos, a very different eyepiece design. It's the only one with a 100 degree apparent field of view, comes in only one focal length so far, 13mm. It weighs in at 1.25 lb, yes pounds not ounces! It retails for a paltry $620 (lowest price I found).
http://www.televue.com/engine/page.asp?ID=311
Note, its field stop is 22.3mm and thus would work just fine with a full barlow that fits in a 1.25" format though most have lenses smaller than that, including the Klee and PowerMate. Before this eyepiece larger lenses weren't necessary. So I'd use it with a 2" PowerMate -- another $257 if I were to use it with a "barlow" which I wouldn't do anyway. Technically, while a PowerMate does the same thing as a barlow, it is a very different optical design with very different optical properties. Nor is it a new design as some think. I have a 50's era Bausch & Lomb 60mm refractor with a PowerMate type "barlow" so the general design is nothing new. But for a beginner it is overkill as those differences are immaterial for general viewing with standard eyepieces.

I remember sometime in the 60's when a long defunct outfit offered a lens to go over an eyepiece that doubled the power and the size of the apparent field of view. It actually did, sort of, but the distortions and fuzzy image quality made it worthless. It died a well deserved death but not before many bought it. Word didn't get out fast back then so they likely made money off the scam. And they never did claim the view would be usable, just that it would be double the size in all respects. I didn't fall for it but probably only because others in the club did and I learned from their mistake. Can something like that be designed today? I don't know but since no one is I assume it would be very expensive and thus not cost effective even if it did work. Since each type of eyepiece and even each in a series have different distortions that would be amplified by such a system I doubt it can be made to work very well no matter the cost.

A 50 degree field of view of a plossl is actually quite wide. About like sitting a bit over 4 feet (53.6") from a 50" diameter round TV screen but clearer than HDTV. Far wider than the size of your sharp vision. Many eyepieces that come with scopes are of a modified Ramsden design often with less than half the usable field of view that the Sirius Plossls provide. With those you do feel like your view is restricted. With a Dob an extra wide field is helpful if it is also fully corrected (an expensive if) as you can watch longer before moving the scope. Dob's move so smoothly I've never found much need for a wider field of view, even when using high power. Others disagree. That's something to deal with after your budget recovers and you have a better idea of what you want. For now, the plossl design will serve you well.

Rick

[Siguy]

I don't use plossl eyepieces, but I know that they work very well. The 50 degree field of view is pretty good, but not the widest. They're usually packaged with scopes due to their high performance and low cost.

If you want cheap wide apparent field eyepieces, I suggest the Orion Expanse. They're cheap and they perform well, at least for me so far. They also have nice eye relief (how far away you have to hold your eye from the eyepiece).
http://www.telescope.com/control/product/~category_id=eyepieces/~pcategory=accessories/~product_id=E0006

University optics also sells an 80 degree ocular for $60. But the eye relief is only 9mm. So if you wear glasses, like I do, you'll have to take them off to look through the eyepiece.
http://www.universityoptics.com/125inch.html#80

Keep in mind that the magnification of the telescope is the focal length divided by the eyepiece focal length, that the eye relief of an eyepiece typically goes down with the focal length, that you're typically limited to 300x magnification, and that a 100 degree 13mm ethos will show you just as much sky as a 50 degree 26mm plossl, but it will be bigger.

But don't listen to me, I haven't been using telescopes long enough to know.

[Arcane]

Thanks a lot for the input guys, I guess I will just have to wait until my telescope and Barlow arrive (Sometime this week) and play with them a bit before I get into any more discussions on what I do or don't need heh.

I am sure you will be hearing a lot from me around here. I have always had a huge interest in astronomy and all the sciences that go with it, but I just never took the plunge and bought a good telescope, I really do feel like a 6yr old on Christmas morning waiting for this thing.

Thanks again. :dance:

[RickJ]

Actually the effect is quite noticable up here. More so than when I was in Nebraska due to the added loss of contrast due to sky glow and, in winter, fine ice crystals in the air. I'd expect with lake effect snow so strong near Duluth it may be even worse. I don't know.

Larger exit pupil does lower contrast and it is noticable. The darker the sky the more you notice it. Al Nagler talkes about it pushing his super expensive Ethos eyepiece. Scan down half way to the photos of the double cluster. The darker one is at half the exit pupil size of the smaller one. With binoculars you run into the inability of holding them steady so there's a limit on how much you can raise power and keep the lens size large enough. That's about 8 to 10x for most folks. So you can't double things as in this link but the effect is the same. Sky is brighter at 7mm than at 5mm with the same objective size. The higher contrast makes a big difference when you go for faint things like the outer parts of the Rossette or seeing the Cone Nebula at all or Barnard's Loop etc.
http://www.televue.com/engine/page.asp?ID=311

But Kaptain K is right. A beginner won't be looking for what I am! And in no way does this detract from the quality of the Orion binoculars. They are of very high quality and certainly worth their price tag. I just wish they came in a 10 power version for a 5.6mm exit pupil size. Those who can hold 10x steady would actually see more in about any sky conditions.

Rick

[Maksutov]

[edit]Is this a great telescope? I know its on the lower end price wise, but will it get me some great views of planets and galaxies?...It should provide some decent views of Venus (the phases), Mars (polar cap and some surface detail such as Syrtis Major), Jupiter (cloud bands, GRS, and the Galilean satellites), and Saturn (rings, with Cassini division, a few cloud bands, and Titan), as long as the seeing is good, the planet is well up in the sky, and you keep the image centered in your field of view. The Moon will be spectacular and, as it approaches full, may require a filter to diminish the brightness.

For galaxies, they're all (except the Milky Way) going to look mostly like fuzzy clouds of various shapes. You need a really large light bucket (talking 24+ inch objective mirror diameter) and really dark skies before you start picking up spiral arm detail with your eye. Time exposures would show some of this detail with an 8", but that would require a computer-controlled and/or equatorial mounting.

For planetary nebulae, open and globular clusters, double stars, etc., it will provide some really nice views. As mentioned earlier, a good bargain for a starter scope.

[eagle]

I'm looking to buy my first telescope, any opinions which would be best for lets say no more than $250 bucks. Thanks.

[aurora]

I'm looking to buy my first telescope, any opinions which would be best for lets say no more than $250 bucks. Thanks.


Start by reading the threads that are already here where people have already asked similar questions and gotten lots of great advice (including links to other sites with online articles that are aimed specifically at beginners).

There are lots of types of telescopes, no one can tell you what to get without knowing a lot about you.

One thing to avoid, though, is the so called department store telescope, a 60 mm refractor on a shaky equatorial mount.

[Kaptain K]

Second what aurora said! There are just too many variables involved for a blanket recommendation.

[Veeger]

Yeah. I can recommend you forget about magnification and all such claims and instead focus on quality optics and a quality mount. Read and research as the others have already advised. A quality scope can always be enhanced by accessories later, but a poor scope is still a poor scope no matter what accessories you buy.

Good luck,
-Veeger

[Kaptain K]

$250 is pretty much on the border line. There are a few quality scopes below that, but you can easily spend more and still get a poor scope!

It's been said before, but it bears repeating: The best starter scope is a pair of binoculars!