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KiannJames

If you are looking for a scope dont buy the Powerseeker 127EQ!!

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To beginners out there: If you are looking for a scope to buy dont buy anything out of the Celestron Powerseeker series, the Powerseekers are cheaply-made low quality scopes I have used a 127EQ and it had the worst views i have seen through a telescope of that aperture, this is due to the fact that its a Bird-Jones type reflector this means that the mirror is spherical, good reflectors usually have parobolic mirrors and  if you are looking for a cheap scope the Celestron Firstscope or the Skywatcher Heritage 76 are good scopes at around £50, if you are looking to spend around £200-£300 i would say the Skywatcher Skyliner 150P or 200P would be good or you could get the Orion Skyquest XT6, if you are looking to pay maybe £100-£200 the Orion Starblast 4.5 would be pretty good although you would need a sturdy table to place it on. Also dont expect NASA-Class views from your scope, with galaxies you can expect a tiny smudge and with nebula you will only see a grey to Green smudge also with planets expect tiny dots with detail depending on the size of your scope.

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What in heck is a "bird Jones" scope and why do people hate em lol, spherical mirror?? you mean like a ball? i struggle picturing a spherical mirror in a scope. Why "bird jones" was that the name of the guy who invented it? and, why was he allowed to market such a bad design? someone should have a talk with bird jones.

Edited by Sunshine
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13 minutes ago, Sunshine said:

What in heck is a "bird Jones" scope and why do people hate em lol, spherical mirror?? you mean like a ball? i struggle picturing a spherical mirror in a scope. Why "bird jones" was that the name of the guy who invented it? and, why was he allowed to market such a bad design? someone should have a talk with bird jones.

Bird Jones design is not a bad design. It is probably poorly executed design (more times than other designs).

Spherical mirror is just a segment of sphere, like parabolic is that of parabola. Both mirror shapes have aberration associated with it.

Spherical mirror creates spherical aberration, while parabolic - coma. Many designs have spherical mirrors in them - SCT and Maks for example - and employ corrector plate to counter spherical aberration of primary mirror.

Bird Jones design is similar in that it uses spherical mirror and corrector - but corrector is sub aperture corrector located inside focuser. Knowing this you can see why it can be poorly executed design - cheap telescopes come with cheap and flimsy focusers that tilt easily. There is also matter of figuring corrective lens properly - that also costs money. Just take a look at decent 2" field flattener - things cost anywhere from 150euros upward.

Can you expect whole scope to perform well for the same amount of money?

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People hate them because they are harder to collimate and the corrector lens will absorb and scatter some of the light and it also introduces some Chromatic aberration.

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I want a "Bird Jones", with which to putter and tinker, as I'm not a beginner; and I will have one eventually, either the Meade or Celestron.

However, those first starting out would be ill-advised in the getting of one; run away, and as far as you might.

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Rutten & v.Venrooy show these spot diagrams. For a fair comparison, look at the marked spot diagrams. Both are for 200mm f/6 systems. At the top is the Newtonian parabolic mirror, at the bottom a spherical mirror with Bird Jones corrector. The B-J has hardly any coma, but a whole lot of field curvature, hence the big out of focus blur 10mm off the optical axis. The radius of curvature for a 200mm f/6 B-J is 72mm.

The B-J in this example is perfectly collimated. In practice, collimating a B-J is very difficult, and results as here are difficult to obtain.

Young eyes can to an extent compensate for the field curvature. Older observers stand no chance.

newt-vs-BJSpher.thumb.png.c25b0b4f09f234216c966c420a63c5e4.png

Oh. The B-J has three sets of spot diagrams. That's for red, green and blue. It looks as if the corrector will not introduce any perceptible chromatic aberration.

Imagine the excellence of an f/12 Newtonian! Also, observe how an f/8 Newtonian improves on an f/6 one. 

 

 

 

Edited by Ruud
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1 hour ago, Alan64 said:

I want a "Bird Jones", with which to putter and tinker, as I'm not a beginner; and I will have one eventually, either the Meade or Celestron.

However, those first starting out would be ill-advised in the getting of one; run away, and as far as you might.

Oh, get this one and do a review, please :D

https://www.teleskop-express.de/shop/product_info.php/info/p685_TS-Optics-Megastar1550---150-1400-mm-beginner-telescope-on-EQ3-1-mount.html

It's F/9.33 scope and 6" one - that's got to be good :D

I just love the look of that short tube, sort of reminds me of this one:

image.png.9f6bc2ba0db1eff3824ff9eea7163c38.png

Do you think they would perform about the same?

(btw, as far as I know epsilon also employs sub aperture corrector but with hyperbolic mirror - apparently very good execution of that design)

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Just now, vlaiv said:

Oh, get this one and do a review, please :D

https://www.teleskop-express.de/shop/product_info.php/info/p685_TS-Optics-Megastar1550---150-1400-mm-beginner-telescope-on-EQ3-1-mount.html

It's F/9.33 scope and 6" one - that's got to be good :D

I just love the look of that short tube, sort of reminds me of this one:

image.png.9f6bc2ba0db1eff3824ff9eea7163c38.png

Do you think they would perform about the same?

(btw, as far as I know epsilon also employs sub aperture corrector but with hyperbolic mirror - apparently very good execution of that design)

That one, in yellow, is reminding of a Takahashi astrograph; perhaps it is in fact.

Oh, I've seen that TS "Bird Jones" before, and waxed poetic over the prospect of actually owning it.

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6 minutes ago, Alan64 said:

That one, in yellow, is reminding of a Takahashi astrograph; perhaps it is in fact.

Yes indeed it's Takahashi Epsilon - I tried to make a joke by extreme contrast :D - probably did not work as well as I expected

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1 hour ago, Alan64 said:

I want a "Bird Jones", with which to putter and tinker, as I'm not a beginner; and I will have one eventually, either the Meade or Celestron.

 My first was the 127EQ, cost about £30 but very quickly discovered that I needed something different/better.
I  did eventually tinker, clean, setup,.........did everything but to no avail? the scope was still as useful as a chocolate fireguard!, couldn't even give it away,  but eventually sold it to a high street cash converter store, who even deducted a few notes because the tube had a slight dent? I  think I got my monies worth back, I'd need to check?

The scope itself gave me my first telescopic view of the moon, I also learnt basic collimation, which is not really needed on such a scope! It also helped me understand  about equatorial settings and setting-up.

Image quality was not the best, and the continuous tinkering with the controls was simply time wasting. I learnt something from the scope, enjoyed the four new books that also came with my scope, but as for recommending this scope.........................................? sorry, No!

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2 minutes ago, Charic said:

 My first was the 127EQ, cost about £30 but very quickly discovered that I needed something different/better.
I  did eventually tinker, clean, setup,.........did everything but to no avail? the scope was still as useful as a chocolate fireguard!, couldn't even give it away,  but eventually sold it to a high street cash converter store, who even deducted a few notes because the tube had a slight dent? I  think I got my monies worth back, I'd need to check?

The scope itself gave me my first telescopic view of the moon, I also learnt basic collimation, which is not really needed on such a scope! It also helped me understand  about equatorial settings and setting-up.

Image quality was not the best, and the continuous tinkering with the controls was simply time wasting. I learnt something from the scope, enjoyed the four new books that also came with my scope, but as for recommending this scope.........................................? sorry, No!

Being mass-produced, there are going to be quite a few duds, in regard to the quality of the figuring of the mirrors and lenses, at that price-point.  It's a gamble, which is why I'll be looking for just an OTA, and at a price I can live with.  Incidentally, I have read of a few amateurs who have realised decent performance out of one, therefore I want to see how I might fare, but it's going to require a bit of DIY.  It's an economical alternative to a Schmidt-Cassegrain, which may be part of the draw to it by those first starting out, albeit unwittingly, but its obvious attractions are its compact size and low price...and much to our dismay.

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General rule of thumb:

Don’t buy anything with POWER or superlatives in the name. ?.

Unless you enjoy fixing stuff or proving that the product is neither usefully powerful, super, mega, max, ultimate etc etc.

Paul

ps. Before the pedants start glaring down their Powermates  at me. I did spot that exception!

Can anyone think of any others?

 

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The Takahashi epsilon is not at all like a Bird Jones. The epsilon has a  hyperbolic primary, whereas the Bird Jones uses a spherical primary.

The Takahashi epsilon is very fast, has a flat field and is very costly.

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1 minute ago, Ruud said:

The Takahashi epsilon is not at all like a Bird Jones. The epsilon has a  hyperbolic primary, whereas the Bird Jones uses a spherical primary.

The Takahashi epsilon is very fast, has a flat field and is very costly.

 

52 minutes ago, vlaiv said:

(btw, as far as I know epsilon also employs sub aperture corrector but with hyperbolic mirror - apparently very good execution of that design)

 

42 minutes ago, vlaiv said:

Yes indeed it's Takahashi Epsilon - I tried to make a joke by extreme contrast :D - probably did not work as well as I expected

Contrast part covers, price, focal length, usage and performance :D

 

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2 hours ago, Paul73 said:

General rule of thumb:

Don’t buy anything with POWER or superlatives in the name. ?.

Unless you enjoy fixing stuff or proving that the product is neither usefully powerful, super, mega, max, ultimate etc etc.

Paul

ps. Before the pedants start glaring down their Powermates  at me. I did spot that exception!

Can anyone think of any others?

 

Exactly!  If its advertised as powerful dont buy it.

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2 hours ago, Charic said:

 My first was the 127EQ, cost about £30 but very quickly discovered that I needed something different/better.
I  did eventually tinker, clean, setup,.........did everything but to no avail? the scope was still as useful as a chocolate fireguard!, couldn't even give it away,  but eventually sold it to a high street cash converter store, who even deducted a few notes because the tube had a slight dent? I  think I got my monies worth back, I'd need to check?

The scope itself gave me my first telescopic view of the moon, I also learnt basic collimation, which is not really needed on such a scope! It also helped me understand  about equatorial settings and setting-up.

Image quality was not the best, and the continuous tinkering with the controls was simply time wasting. I learnt something from the scope, enjoyed the four new books that also came with my scope, but as for recommending this scope.........................................? sorry, No!

Yeah it was also my first scope, the views almost put me off astro but i searched the internet and realised that it was just that type of scope that was bad.

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That is too general and unfounded as spherical mirrors are fine and often used well on slower telescopes.

However it would be more appropriate to say be careful of choosing a reflector telescope that has a focal length that far exceeds the telescopes physical length.

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16 minutes ago, happy-kat said:

That is too general and unfounded as spherical mirrors are fine and often used well on slower telescopes.

However it would be more appropriate to say be careful of choosing a reflector telescope that has a focal length that far exceeds the telescopes physical length.

So you mean buy a refractor ?

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Maybe we ought to have a 'sticky' for prospective telescope owners which lists models with reasons for beginners to avoid.

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