I am wanting to get a decent scope from orion, and am wondering how much larger aperture will benefit me. The 8" is $360 and the 10" is $530, while the 12" is $870. So, I am mostly looking for brighter objects, Messier and the best NGC stuff, planets out to neptune. This past winter I bought a 4.5" EQ mount from orion, but I don't like the mount and I need to get a real spotting scope for it. I figure I should cut my losses with it and go with the bigger scope. So the question is, is there that much that an 8" would have problems with that would jump out in a 10"? Or from 10" to 12"? Are we talking about seeing a lot more random field stars for the bump up in aperture, but not a lot of extra "cool" stuff?

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I make my living selling beans which repel ogres, goblins, and sand worms. I eat a bowl a day and have never been attacked!

Big difference between 8" and 12". I have an Orion XT 8 and two home made 12.5" and where the difference really shows is with nebulas and galaxies. However, the only time I have ever seen the central star in the Ring Nebula was with the 8". Seeing was really good that night. Whichever one you buy,do your neck a favor and buy the 9 x 50 right-angle finder right off.

Bear in mind portability - or lack of it. A 12" scope is a lot harder to move around. If you have good dark skies at home, and an easy way to get the scope out, I'd go for the 12". 12" for $870 is pretty much unbeatable value. But if you have to drive to a decent site, that big heavy tube is going to become a real hassle pretty quickly.

If transportation and storage won't be a problem, get the 12". The way to see the faint stuff is with aperture, and the light-gathering ability of a 12" is more than twice that of the 8" and almost half again that of the 10".

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The ether of general relativity therefore differs from that of classical mechanics or the special theory of relativity respectively, in so far as it is not 'absolute', but is determined in its locally variable properties by ponderable matter.

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Aperture is always king. The old rule of thumb is to get as much aperture as you can afford. That aside, you should temper that advice with get as much aperture as you can lug around.

When I have a chance to view, time or a hole in the sky, I grab the scope that I can drag out there and use. It is usually the 6 inch f10. I can grab it, set it up and can be viewing in five minutes or less. I have an 8 inch f10.5 truss that takes about 15 minutes to set up and I have had some of my best views with that scope. M13 just sparkles with the 8 inch and a 39mm Erfle. But it is a pain to move. In fact I use it so little I offered it to a friend that was looking for a scope, so it may be going away.

I think a scope should be tough and simple, but I live in the Northwest on the coast and observing sessions are spontaneous affairs.

David Davis
Toledo, OR 97391

It might help you to decide knowing that 12" (12.5") is widely considered to be the aperture where deep-sky objects generally begin to exhibit good detail, as much as those words can be attributed to observing DSOs.

Dave Mitsky

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If portability is an issue, go with the 10". I upgraded from an 8" to a 10" (both Orion XT dobs) and noticed a significant increase in detail in DSO's (more than what I was expecting). Also, the tube length of the 10" is almost the same as the 8". IMO, the 10" is almost as portable as the 8", but you get more performance from the 10". The nice thing about the 10" is that I can still remain seated for viewing any object, even at zenith. If portability is not an issue, 12" all the way!

Remember also that your Dob will require continuous nudging to keep an object in the FOV. That was one of the factors that pushed me towards a GEM. Since I'm not an imager, I don't need a platform with exceptional error correction (PEC), just reliable tracking for visual observing. I prefer to look at one object for a while than many objects for a short time, and the GEM allows me to find said object, put it in the center of the FOV and forget about everything except looking at it.

Edit: typo

On the other hand, if you have a short attention span, there is no quicker way to star-hop than with an alt-az mount!

I have an XT12 and do not regret it. I have modified my pick up by putting a top over the bed to allow more room. I find very little problem transporting it around. The carrying bag that I bought to go with it has the handle slightly toward one end. That is the end I put the mirror end in and it balances well as I walk it out to my truck.

Great views of DSOs. Nice detail and everything is much easier to find. Not having a clock drive is offset by the large aperture. It takes a while before the object goes out of view. Last Saturday I went from my scope to talk to someone for a few moments and after returning I found M13 was still in the field of view. I need sunglasses to look at the first quarter moon..I am getting a binoviewer to go with it and can't wait..

Anyway, it's your money.

I should update this one. There is an 8" dob now in my garage. Any guesses as to the weather conditions here since it arrived? If this one works out, I will probably upgrade to the 12" next year, otherwise if the manual tracking gets to be an issue, I will get something with an electric drive. I will be thrilled to see the Andromeda galaxy, M13, and the various wonders in scorpius. I'll be able to see M4 in the finderscope with Antares in the same view, right? Star hopping sure is easier when a bright star is right next to the DSO, like M42!

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I make my living selling beans which repel ogres, goblins, and sand worms. I eat a bowl a day and have never been attacked!

Depends on the finder, but it isn't really necessary. M4 is the nearest bright object to Antares.

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T. Anderson

If you get a Telrad or red dot finder on the scope, then there are a lot of objects that are quick and easy to find because a naked eye star hop is possible.

(imagine someone with a laser pointer at a summer star party)

The Ring Nebula, for example, is right between those two naked eye stars at the bottom of Lyra.

M13 is along that west side of the keystone in Hercules, two thirds of the way toward the longer side of the keystone.

Alberio, the double star, is the head of Cygnus the swan.

(lather, rinse, repeat)

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"Arrrgh, the laws of physics be a harsh mistress!" -- Bender

I really disliked the red dot finder on my 4.5" reflector, so when I ordered the 8" I also ordered a 9X50 finder to replace the smaller one the 8" came with. I had enough time to look at Jupiter for five minutes or so before the clouds rolled in; that was a couple nights ago.

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I make my living selling beans which repel ogres, goblins, and sand worms. I eat a bowl a day and have never been attacked!

You have room for both kinds of finders on an 8 inch Dob.

But if you can use your 9x50 to quickly point your Dob to a spot in the sky you can see naked eye, then you don't need the red dot or a Telrad.

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"I'm as accurate as any psychic. And I'm a cartoon!" -- Squidward

"Arrrgh, the laws of physics be a harsh mistress!" -- Bender