Orion Vs., Celestron.. which brand?

[karthikrr]

Hi, Im a beginner looking to buy my first scope... I am currently eyeing a 6" Dobsonian, which seems to be the best scope for a beginner such as myself... Would you agree with that???

And what brands are good??? I have only heard of Orion and Celestron, and the Orion site was very helpful.... I am looking at the

SkyQuest™ XT6 Dobsonian Reflector
http://www.telescope.com/shopping/product/...add=yes#tabLink (http://www.telescope.com/shopping/product/detailmain.jsp?itemID=365&itemType=PRODUCT&iMainCat=4&iSubCat=9&iProductID=365&relateInfo=3&add=yes#tabLink)

and the SkyQuest™ XT6 IntelliScope™
http://www.telescope.com/shopping/product/...add=yes#tabLink (http://www.telescope.com/shopping/product/detailmain.jsp?itemID=14854&itemType=PRODUCT&iMainCat=4&iSubCat=8&iProductID=14854&relateInfo=3&add=yes#tabLink)

I think the only diff b/w the two is the computer controller thingy... I'll prolly skip that and just invest that saving into future upgrades such as eye-pieces and filters... whats your thoughts on this???

Also, we have a local maker here in India, called Galileo telescopes ... Any of you ever hear of them??? They are offering a 6" Newt Reflector on a tripod for bout $370 ... They claim to use some of the finest optics in the world and claim to offer personalised guarantee and service... But, I dunno if I should invest that much cash in somebody who might not be very good... $370 is quite an amount, in Indian Rupees... :)

Anyways, I primarily want to know if a 6" Dob is a good buy, and which manufacturer is more reputable, and whether the models I mentioned above are good ones... Thanks in advance for all the help,
Cheers.
Karthik

PS - I also considered building my own, but decided against it just coz it seems too much work, and I dont really have that much time to spare... but, would it be any cheaper to get it built??? I have a friend who owns a timber factory, and who also has a furniture building house... so, if I could get good details on the construction, I could just get it done by them, for a decent rate... But, Im not too sure bout the mirrors and the lenses and stuff... do u think its worth it?

[karthikrr]

ooops, I forgot to say what aspects I was interested in... basically, some deep space objects, more than just observing the planets... and I live in a small little city, without too much light pollution, but I would prefer if I could lug it around, so that I coulo get away to a totally dark and clear campsite or something... The Orion Reflector fits my budget perfectly, but if you think the 8" reflector is REALLY worth the price difference, I MIGHT be able to squeeze a bit more cash out... But, being a TOTAL beginner, who has never used a scope before, would it be worth it???

And no fear of me 'ditching' astronomy... I have always been and always will be fascinated by the topic, and nothing can prevent me from gazing at the sky... :)

[Dave Mitsky]

Karthik,

The jump from 6 to 8 inches of aperture is the single most cost effective one. Do it if you can.

A digital setting circle can come in very handy but if you want to get the most out of amateur astronomy I suggest you learn how to star-hop.

You should also consider Discovery Telescopes. Their telescopes have the best mirrors of any of the entry level Dobs.

It might be best to not consider the other brand you mentioned.

Dave Mitsky

[karthikrr]

Hey Dave,

Thanks a lot for your response... Discovery, I'll take a look at them too... and maybe I'll get an 8", if its not TOO much of a price difference... And star-hopping, yup, better learn things the traditional way... :)

What bout the constructing my own scope angle??? Another person told me that it was well worth it, to build my own... He claimed that it wasn't really as intimidating as it seemed, and that it was pretty easy and could be completed in just about two weekends, if I sat down to it... Any opinions?

Thanks again,
Karthik

[karthikrr]

ok, I checked out the Discovery Range, and the 8" DHQ model looks good and affordable... But, I was wondering, there are two models, f/6 and f/7 ... which ones for me??? ANd tube lengths, if I recall right, the longer the tube, the lesser the field of view, right??? So, for dso's, I need to get the shorter tube, and for planetary views, I need the longer tube, yes? Im not too sure if thats right, so feel free to set me right... :)

oh, and eyepieces, exactly how dies that work out? Smaller ones offer better magnification? better resolution? what? and should I be investing in a Barlow lens (I didnt get what they do, but apparently they help doubling the magnification...?) ... Orion, I think offered a Barlow lens too, with their stock package, but thats not so with Discovery... HELP!!! :)

Cheers,
Karthik

[karthikrr]

ok, I just checked, and Orion does not offer Barlows with their 8" ... but, its priced bout $50 less, and that works out to a saving of nearly Rs. 2500 for me... Are the Discovery Optics THAT superior to Orion's??? BTW, Discovery, I cannot afford their PDHQ range, which seems to be the one with the specially made optics... Just the regular baseline DHQ models...

aaaaaah, Im gettin confused now!!! :)

[mvbenz]

:blink: I am a newbe and got an Orion XT8 Intelliscope Dob for xmas. It is easy to setup and use and has gotten great reviews. So far I have seen the Orion Neb, Saturn, Jupiter and the moon but I am still learning my way around the skys. I would recommend you get a Barlow lens with whatever scope you decide on. I just got the Shorty Plus 2x 3 element lens from Orion. Haven't had a chance to try it tho as it has been over cast all week.

Mike...

[fleetwizard]

kathikrr,

IMO the dob style scope is absolutely the best for beginners. And forget the Intelliscope option. You can add it later if you want it, and if you are just beginnging, it's better to use the classic model to learn the sky first. I agree with Dave in that the 6" to 8" jump is probably the most cost effective, but, if you can, teh 10" is even better. Although, going bigger than the 8" also starts to get into the realm of travel problems. I personally have an Orion XT-10, so I am kind of biased towards the Orions.

Meade also makes dobs, but I think they have quit marketing anything smaller than their 12.5". I picked the Orion over the rest of them for two reasons. The biggest is that it is the only one, or was when I bought mine, that uses a metal tube. The rest use a sonotube, which is a fancy word for painted cardboard. The other was an article by Sky and Telescope, which compared the top 8 or 10 dobs and they concluded that the Orions were the best. I think that article was in January of 2002. Or maybe 2001.

As far as Galileo goes, I didn't know they made a dob. The only one of theirs that I'd ever heard of was a refractor. But, it is a cheap, department store model which you probably wouldn't be able to see much with.

As far as the eyepieces go, yes, the smaller the EP, the higher the magnification. To a point. Each scope has a magnification limit. About 50x the primary mirror diameter, or in the case of a 6" scope, about 300x. However, that is based on absolutely clear, perfect skies. A better rule of thumb is about 25x the primary diameter. Or, again for a 6" scope, about 150x. So, basically any EP that goes above those limits is a waste of your money. To find the magnification of any given EP, divide the focal length of the scope, in mm, by the focal length of the EP, again, in mm. For example, my dob has a focal length of 1200mm. If I use a 30mm EP with it, that gives me 40x magnification. If I go to a 10mm EP, that raises my magnification up to 120x.

The Barlows are definitely worth the money. They bascially double the number of EP's that you have for the cost of one EP. Or triple for the cost of 2 if you get the 2x and the 3x Barlows.

I hope this helps you some. What it boils down to is this, I would get a dob. Up to 10", the larger the better. But, I would go for a smaller aperture and more EP's and a Barlow than limiting myself with the larger scope to start.

And as far as building your own scope goes, I don't really think you will save much these days. Orion does, however, sell just the optical tube assembly if you wanted to try and build your own dob base, which is really nothing more than a lazy susan with sides to put the altitude bearings in. You can download the manuals for the Orion dobs from their website or there are a few dob building websites around the web.

Again, I hope some of my ramblings help somewhat. I do go on and on, don't I? :rolleyes:

Ken

[mvbenz]

:blink: I just read your post on lenses. The smaller the number on the lens the more powerful it is. A 2x Barlow lens will double the rating on your lens, Ex. a 10mm lens used with a Barlow will make it a 5mm lens. I just got the Orion Shorty Plus which is a 3 element Barlow. A Barlow will in effect double the number of lenses you have in your collection saving you money in the log run.

As far as which brand, it is a matter of opinion. I joined a few news groups on Yahoo for telescopes and made up my mind on the Orion Dob. Not that it is better but it fit what I was looking for and got great reviews. I was also thinking of building my own but I bought one first to see if I would stick with it before attempting to build one. Building one is not any cheaper than buying one and can, in some cases, be more expensive.

Mike...

[karthikrr]

hey, thanks alot for the responses, mike and ken.... :)

Really helped a lot... I think Im going in for the 8" Dob then.... Without the intelliscope bit, prolly use the cash to get me a cpl Barlows...

Ken, u DON'T ramble on... ok, maybe a lil, but I like ramblers... I tend to ramble too... :) That was VERY informative.... I don't have the cash for a 10" atm, but I can manage n 8" ... btw, have u actually HEARD of Galileo, as in the telescope makers from India??? Coz I got in touch with them, and they claimed that Orion used optics that were mass produced in China, while they used their own optics, which were superior to Orion's ... And since its a local company, it woulda helped in after sales support too, and I had almost decided to give them a go, until I realised that they don't sell Dobs, and that their EQ 8" Reflector was priced at $600 !!! That was a BIT too much for me.... I asked them about this, and they said that even with the Orion, after all the import duties and stuff, i'd end up paying the same amount... Im not sure yet, but I doubt its gonna go THAT high... anyways, for now, its DEFINITELY the SkyQuest for me... and I gave up on getting the OTA and making my own dob, coz it doesnt come with EPs and stuff, and that meant Id have to make more decisions... :) Just go for the package, I decided...

Mike, that shorty Barlow u spoke about, Im assuming thats the best option for me too? I dont want to think about it anymore... Just want to make a decision and buy... :)

Oh, and another question... what the hell does the f/7, f/6, etc., indicate???

Thanks a lot again,
Karthik

[Dave Mitsky]

If you want the Orion Intelliscope system you have to get one from the get-go. From the Orion web site, "The IntelliScope controller is NOT compatible with other encoder systems or other computerized telescopes. Previous SkyQuest versions or other Orion telescopes cannot be retrofitted for IntelliScope compatibility." Of course, you could always add traditional optical encoders such as the Sky Wizard to a regular XT Dob but it will cost more in the long run.

The material a mirror is made of (soda-lime glass versus Pyrex for instance) is mainly an issue when it comes to athermalization (cool-down). The most important thing optically speaking is wavefront error (1/8 wave is considered "diffraction limited") and here the general consensus is that the Discovery mirrors are a bit better. (Discovery used to supply the mirrors for the old non-Chinese Orion Dobs and the Celestron Dobs.) However, my girl friend owns an XT6, which I've used on numerous occasions. It is a very capable instrument and would be a good choice as well.

The Meade Dobs are plagued by the fact that the mirrors are mounted directly to a hunk of metal and therefore never reach thermal equilibrium properly. They do have a reputation for having good optics, however.

I very strongly doubt that you could grind, polish, and figure an 8 inch mirror on your own without prior experience over the course of two weekends let alone construct the support structure for a Dob. If you bought a commercially ground mirror then perhaps it could be accomplished. You may not save much money by building your own telescope but the chances are you will end up with one that is superior optically and mechanically to entry level commercial units.

F/ratio is simply the focal length of the telescope divided by the aperture. A 10" (.25 meter) aperture with a focal length of 50" (1.25 meter) has an f/ratio of f/5. It is a telescope urban legend that fast (f/ratios below f/6) are inherently better for deep-sky observing. I observed over half of the Astronomical League's Herschel 400 (400 of William Herschel's original catalog) using a 17" f/15 classical Cassegrain with a focal length of 6477mm! You do trade off field of view with a slow telescope (f/ratio greater than f/10) but that can be counteracted somewhat by having a 2" focuser and using 2" wide-field eyepieces. Keep in mind that there are fewer than 100 deep-sky objects of large apparent size but many thousands of small globular clusters, planetary nebulae, and galaxies that are visible to the amateur astronomer.

Another common myth is that deep-sky objects should be viewed only at low power. Increasing magnification improves the "contrast" between a DSO and the background field, particularly under light polluted skies. In addition, objects that are made larger in size by high magnifications are easier to detect by virtue of the physiology of the receptors in the retina. It's a good rule to routinely use a variety of magnifications while observing a DSO. Of course, there is a point where things become too dim and fuzzy and the observer has to return to a lower power.

A third point of confusion is the fact that a telescope can not increase the surface brightness of an extended (non-stellar) object. Telescopes make things bigger but they can't violate thermodynamic law by making them brighter than they are to the unaided eye.

When it comes to visual use telescopic resolution is determined solely by aperture. A large telescope has greater resolving power than a smaller one. Light grasp is also a function of aperture.

Telescopes with superb optics and without central obstructions such as extremely expensive apochromatic refractors typically outperform somewhat larger but far less expensive Newtonian reflectors and somewhat less expensive catadioptric telescopes, Schmidt-Cassegrains in particular.

You may find the information at http://www.televue.com/engine/page.asp?ID=140
and http://www.televue.com/engine/page.asp?ID=141 helpful.

Dave Mitsky

[karthikrr]

Dave, WOW! That was great buddy... Thanks a lot...

As far as the Intelliscope goes, I only thought I could add one, coz Orion was advertising them separately as add-ons... Truth betold, I doubt Id ever buy it anyways... I've decided on the Orion XT8, primarily because it seems to me to be gerat value for money, and a very capable all-round telescope... Granted that the optics might not be the best in the world, but hey, Im just beginning... this is only my first scope, and Im sure many will follow.... :)

And the guy who told me bout making one over two weekends, he did not grind and polish the mirrors himself... And I feel that Im better off owning one, and learning exactly how it works first, before I attempt to make my own...

So, I think Im going to be getting the Orion XT8, with that 'shorty' Barlow that Mike mentioned up there... Thanks a lot for all the help guys, really appreciate it... I'll be back when I get my hands on the scope... will prolly take some time, coz Im sitting in India, and have to contact somebody in the US, and get them to buy one, and then arrange for shipping... I doubt its wise to package it and Fedex it or something, prolly better to have somebody bring it along... So, I need to wait until somebody flies down... but, it'll happen in the next two months... Can't wait... :)

Thanks again,
Karthik

[Dave Mitsky]

The optics in the XT scopes are rather good considering their prices. I'm sure you won't be disappointed.

Dave Mitsky

[Planetwatcher]

Ok, on Barlow lenes I understand greater numbers are better, (3X over 2X and so forth).
But what I'm wondering is, if one can use two or more Barlow lenes to increase the scopes power.
Or would such an attempt result in to much distortion to ever hope to focas the thing?

[karthikrr]

Hopefully, I will get a piece that has good optics... I dont think my luck can be bad enough to ensure that I get the ONE bad piece in the lot... :)

I dont understand Barlows, Im just going with Mike's recommendation of the 'shorty' there... :)

[Dave Mitsky]

Originally posted by Planetwatcher@Feb 22 2004, 11:50 PM
Ok, on Barlow lenes I understand greater numbers are better, (3X over 2X and so forth).
But what I'm wondering is, if one can use two or more Barlow lenes to increase the scopes power.
Or would such an attempt result in to much distortion to ever hope to focas the thing?
A 3x Barlow lens is not necessarily "better" than a 2x. It all depends upon the focal length of the telescope involved, the focal lengths of eyepieces owned, the viewing preferences of the observer, and the quality of the local seeing (i.e., atmospheric steadiness).

Two Barlow lenses can certainly be used together. From time to time I "stack" my 2x Celestron Ultima Barlow lens with my 2.5x Tele Vue Powermate.

Dave Mitskky

[fleetwizard]

I observed over half of the Astronomical League's Herschel 400 (400 of William Herschel's original catalog) using a 17" f/15 classical Cassegrain with a focal length of 6477mm!

Dave,

All I can say is WOW!!! How do you lug that monster around? Or do you have it permanently mounted in an observatory somewhere.

The two best I've ever used were a 16" Meade LX-200 that is permanently mounted in an observatory dome (Echo Valley Observatory) just outside Hamilton, Ontario. I loved that one, and it was very cool to be in the dome!

But, the biggest, so far, has been when I was at a Stars and Parks night at Cherry Springs State Park, PA, last August. One of the locals had provided a 17.5", I think it was an Obsession, truss type scope. The views through that were just awesome! And yes, it's on my list of things I wanna get once I can afford it. :D

[Dave Mitsky]

Originally posted by fleetwizard@Feb 24 2004, 11:09 PM
I observed over half of the Astronomical League's Herschel 400 (400 of William Herschel's original catalog) using a 17" f/15 classical Cassegrain with a focal length of 6477mm!

Dave,

All I can say is WOW!!! How do you lug that monster around? Or do you have it permanently mounted in an observatory somewhere.

The two best I've ever used were a 16" Meade LX-200 that is permanently mounted in an observatory dome (Echo Valley Observatory) just outside Hamilton, Ontario. I loved that one, and it was very cool to be in the dome!

But, the biggest, so far, has been when I was at a Stars and Parks night at Cherry Springs State Park, PA, last August. One of the locals had provided a 17.5", I think it was an Obsession, truss type scope. The views through that were just awesome! And yes, it's on my list of things I wanna get once I can afford it. :D
The 17" is pier-mounted in an ASH dome (no relation to ASH the astronomical society). See http://www.astrohbg.org/gallery2/Tour-of-Naylor


If the telescope you mentioned was an Obsession then it was an 18" aperture. Perhaps it was a 17.5" Discovery?

I go to CSSP fairly regularly. Browse http://dvaa.org/Photos/DaveMitsky/ to see some photos I took there (summer Milky Way, the Great BFSP 2002 Aurora, H-alpha solar, star trails, etc.). You should try to be there when Tom Whiting brings his 30" Dob.

Dave Mitsky