Jones-Bird - How to Avoid it

[ThomasG]

Hi all: Newbie here. I've read numerous reports that say the Jones-Bird system is to be avoided. I'm researching the purchase of my fist telescope ($250-350 range), but how can I tell if it employs the J-B system?

As well, can you give me some pointers about what t-scopes in that price range might be good.

Thanks. Love this site, although my brain is swimming a bit.

TG

[Steve Ward]

Welcome to SGL .

Can't help with your question myself but rest assured there'll be someone here to answer it . . .

[rowan46]

welcome to sgl as you know the bird jones are short tube newtonians which use a built in barlow and a spherical mirror celestron scopes don't use them as far as I know. A post was here some while ago that all celestron newts use parabolic mirrors. Essentially what you are looking at as an indicator is price and focal length. Many dept store short tube newtonians are likely to be bird-jones design as it's cheaper to make a spherical mirror than a parabolic one. putting a barlow in front of the eyepiece and shortening the tube keeps the costs down in production and distribution. An orion 8" dob is probably the best bang for buck in the usa although at $399 maybe too much outside your budget if you really can't stretch that far then the orion xt6 may be your best bet

http://www.telescope.com/Telescopes/Dobsonian-Telescopes/Dobsonian-Telescopes-with-Free-Shipping/Orion-SkyQuest-XT6-Classic-Dobsonian-Telescope/pc/1/c/12/sc/398/p/102004.uts?refineByCategoryId=398

[E621Keith]

Welcome to SGL

Bird Jones design is most commonly with ebay and online scopes as well as a few department stores. The should be avoided.

If you buy from a reputable specialist astronomy equipment dealer, you don't have to worry about getting those bird jones designs.

Orion US scopes are good beginner instrument. The Starblast range has a good reputation and a Starblast 6 dob will fit your budget (Similar a 150p dob but uses shorter Explorer 150p's F5 optics).

http://www.telescope.com/Telescopes/Reflector-Telescopes/Reflector-Telescopes-with-Altazimuth-Mounts/Orion-StarBlast-6-Astro-Reflector-Telescope/pc/1/c/11/sc/342/p/102011.uts?refineByCategoryId=342

EDIT: The XT6 Rowan46 recommended is essentially US version of the long tube 150p F6 dob, also highly recommended. It will be easier on eyepieces as well.

[Astro_Baby]

The easy way to tell is the scopes stated focal length versus its actual physical lenght. eg if a scope is stated as having a focal length of 1000mm but is physcally only 500mm long then by definition it must be using a bird jones design.

Note here thyat most scopes tubes arent as long as their focal length because the focal length takes into account other factors such as light path to the focuser etc ...Maksutovs are always shorter than their focal length due to the folded light path but on a newt the only way to increase the focal length beyond its physical size is the use of a Barlow which acts as a doubler.

A bird jones has in effect a Barlow at the base of its focuser to double its focal length. Its most often employed on cheaper or more compact scopes.

[Peter Drew]

"Nail on the head" A-B.

[glowjet]

If you are working to a limited budget, then the best bang for your buck is initially going to be a 150mm Dob with a parabolic mirror. You can then invest in an Equatorial mount at some time in the future, with the addition of just mounting rings and a dovetail to convert your scope to an EQ mounted unit, then with motor drives added, if you so desire, will give you the ability to track what you observe in the night sky

John.

[umadog]

There are very few if any dodgy scopes being sold by companies such as Orion (linked to above) and Oceanside Telescope and Photo (google them). I've never seen either of those companies sell Bird-Jones instruments. All their scopes have parabolic mirrors. I agree with the recommendation of something like the XT6 over the StarBlast. Despite being sold as introductory scopes, the StarBlasts have focal ratios in the f/4 to f/5 range* and that has two drawbacks that aren't beginner-friendly. 1. The optics have to be accurately aligned to perform well at higher powers. 2. Scopes of about f/5 and faster tend to be hard on cheaper eyepieces. So you'll see more blurring at the edges of the field of view. There's also an optical aberration known as "coma" which causes pronounced blur at the edges of lower power fields of view at f/5 and below. Coma is much less evident at f/6 and above. So the XT6 will give more pleasing views than the StarBlast, even though both are 6" Newtonians.

*The focal ratio is the telescope focal length divided by the objective diameter. Lower "f" numbers are considered "fast" and higher "f" numbers are considered "slow."

[Peter Drew]

+1 for the Orion XT6, I have one and it is a great performer on the Moon and planets.

[bod00]

I am no expert on the subject but just to touch on what Astro Baby said, i have a Celestron Astromaster 114eq wich i believe is a jones-bird design because a) its shorter than its 1000mm FL and there is a glass lens at the bottom of the focuser!

In summary i have had more than my fair share of issues with the scope after only a few months of use so i would agree with the other SGL users and say avoid these designs!

As a novice i would say make sure you do your homework as i have been slightly disheartened by purchasing the wrong scope so make sure you dont do the same!!

Thanks and good luck!

[umadog]

Yep, that looks like a Bird-Jones. I've got to say, I hadn't realised Celstron made them and it looks like OPT sell them. I take back what I said earlier: even if you buy from a reputable supplier like OPT you will need to do your homework regarding stuff like this.

[Astro_Baby]

Yup, the skywatcher equivalent though is NOT a bid jones design and is quite a sweet little scope. Also has parabolic mirrors and, like the 130P few people have a bad word to say about it.

[bod00]

I am hoping to rectify my error with a purchase of a SW 150pl next week so fingers crossed for clear skies.

I have only been on the forum a short while but i am definitely seeing a trend of people recommending the Sky Watcher range so if that fits your budget and you can get them in your area maybe these maybe worth looking at!

[GyCx]

My first scope was the Skywatcher 130p brilliant small scope I would recommend it.

[Mr Spock]

You can't go wrong with a 150mm Dob. Lot's of quality for very little money and a great starting point.

[Friedberg]

I have the Celestron AstroMaster 114EQ Bird/Jones telescope and can say it has been kind of a pain to remove and reinstall the Bird/Jones lens every time for collimation. This puts a lot of wear and tear on the focuser assembly as it has to be removed and reinstalled over and over again. I have learned a lot from this little reflector but wish I had known about that darn lens at the bottom of the focuser assembly before my purchase and wish there was a loud way to warn everyone that maybe they should stay away from them.

[legbreak]

I'm researching buying my first telescope (but I'm not breaking the advice that Astro_Baby repeats on her very good site because I only spend 59 minutes a day doing it) but it's worth stressing how important it is to be careful with beginners' scopes . As has been pointed out if a Newtonian's OTA appears much shorter than its focal length be wary. I am considering either the Skywatcher 130 or the Skywatcher 114P (light gathering vs. portability, and yes, I have considered the Heritage 130 dob.) and many sites sell the Skyhawk 114 which is similar (and cheaper) than the 114P but which not only has a spherical mirror as a relative drawback, but also incorporates a Bird- Jones design . One astronomy site, which sells both, even has a video suggesting that the cheaper one is the one to go for . I saw in a branch of a store the other day a 102mm 'own brand' reflector with a very sort tube that based on its stated focal length caused me to believe that it is a Bird-Jones design. It was also over-priced but that's another issue. Oh, and I mean no insult as it wasn't his fault, the very honest, polite and helpful assistant hadn't a clue.

[Joanna Sue]

From my own bitter experience I can say that the Celstron Powerseeker 127 is a Jone-Bird type scope. I would not recommend this scope to anyone. It seems like a bargin but it is just an exercise in frustration and disappointment in the long run. I could point out all the faults of this model as their are several but the biggest is the Jone-Bird design aspect of it. About all it really is good for in my humble opinion is to sit in a corner for the uninformed to be impressed by the fact you have a telescope. Better to hold off and spend a few dollars more to get something a bit more useful really.

- Joanna

[Charic]

I have the Celestron AstroMaster 114EQ Bird/Jones telescope and can say it has been kind of a pain to remove and reinstall the Bird/Jones lens every time for collimation. This puts a lot of wear and tear on the focuser assembly as it has to be removed and reinstalled over and over again. I have learned a lot from this little reflector but wish I had known about that darn lens at the bottom of the focuser assembly before my purchase and wish there was a loud way to warn everyone that maybe they should stay away from them.

Friedberg........Why? If the  barlow was designed to be removable, do you think the task would be so difficult! The telescopes sperical mirror does not have an axis or common focus similar to Parabolic mirrors, so the sperical mirror just needs to be centred, not neccessarily tilted, whereas the Parobilic mirror requires centre and tilt adjustments. ( another reason  why there's no centre mark on M1  and nothing to align too, you just need to see the M1 mirror (primary) clips to confirm alignment)  Its the reason they recommended to return the OTA to the factory for "Factory Collimation". I stripped my Powerseeker 127 just for fun, even centre spotted the primary, till I read on forums similar to this, that it was un-neccessary ( its just for effect now) I trust the telescope was no better than before, unless you seriously jarred the telescope, moving the mirror out of centre alignment, or it was stripped down to clean a slightly dusty mirror, then discovered the pitfalls of the Bird=Jones corrector? There is also talk that you cant laser align these telescopes? The laser does not hit the centre of the mirror (no alignment centre spot ~ how do you know where centre is without the mark!) if the mirror is not centred, and the Barlow lens (Bird-Jones) is in the way!

Hopefully by now, you`ve upgraded,  or from now-on,  reduce the amount of times you strip down all the little nuts and bolts  removing the focuser?

I've stripped the focuser out tonight, as a test to see of the B-J-Barlow lens was plastic or glass. Its the latter. So fully cleaned, and installed, fitted an 18mm BST and can clearly see Jupiter and its four moons, but the detail on the Planet isnt detailed enough. Tried the 8mm and washed out ,  too much magnification. I`d have no problems with my Skyliner.

Hope this helps.

[ShaulaB]

The local astronomy club has a 16" Jones Bird. The huge aperture brightens objects tremendously, giving great views of deep sky objects. On planets, the details are not equal to a smaller reflector scope with a better primary mirror.

The picture shows the 16" JB on the right.

Hope you have gotten a scope by now, and are enjoying the sky!

[Astro_Baby]

Its probably worth saying that a Bird Jones executed to a high standard probably works ok but the real issue is the shockingly poor BJ scopes in the budget marketplace where its used to boost a scopes magnification.  The newbie is often misled by magnification factors believing that its all about mag.