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Celestron "PowerSeeker" 127EQ

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#426 b_bafford

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Posted 15 April 2021 - 08:53 PM

I’m curious if the corrector can be replaced with a lens from a 2x Barlow with the same dimensions and have good optical quality. I’m simply concerned that someday my corrector could possibly need replacement and how I would go about replacing it. Has anyone tested this yet?

#427 iamfurgus

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Posted 16 April 2021 - 02:47 AM

I’m curious if the corrector can be replaced with a lens from a 2x Barlow with the same dimensions and have good optical quality. I’m simply concerned that someday my corrector could possibly need replacement and how I would go about replacing it. Has anyone tested this yet?

You will probably be onto another scope before the corrector needs replacing.  Even Skymuse assessment suggested the optics quality isn't that bad at all, so it wouldn't be worth changing.  I don't think its exactly the same as a barlow either, so not sure a straight swap out will work anyway tbh.



#428 kel123

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Posted 16 April 2021 - 04:40 PM

You will probably be onto another scope before the corrector needs replacing. Even Skymuse assessment suggested the optics quality isn't that bad at all, so it wouldn't be worth changing. I don't think its exactly the same as a barlow either, so not sure a straight swap out will work anyway tbh.


I don't think anyone will tell you that the optical quality of a cheap bird Jones scope is not bad at all. He had to significantly tinker with it before it became useable for him. Stay away from a bird Jones scope if you can.
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#429 iamfurgus

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Posted 17 April 2021 - 12:58 AM

Despite all the tinkering he never changed the glass that's my point. Also it's not helpful to say 'avoid' when the poster clearly already has it. I had a of of fun with mine and learnt a lot, but it is a project scope for sure.
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#430 Dana in Philly

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Posted 17 April 2021 - 11:36 AM

I don't think anyone will tell you that the optical quality of a cheap bird Jones scope is not bad at all. He had to significantly tinker with it before it became useable for him. Stay away from a bird Jones scope if you can.

 

I'll tell you that. I have an AstroMaster 114mm bird jones, which is my grab 'n' go scope. The real deficiency with these entry level bird jones scopes isn't the optics, which are not bad at all (although the corrector does make collimation a bit more involved). The deficiency is the plastic focusers, and the undersized mounts and tripods.


Edited by Dana in Philly, 17 April 2021 - 11:38 AM.

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#431 b_bafford

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Posted 25 April 2021 - 07:29 AM

The reason I’m concerned about the corrector is because the included Barlow lens is plastic. If the corrector is as well then damage is likely to happen to someones corrector at some time. I don’t believe the corrector is plastic but I didn’t really inspect when I had it out. So I’d like to know if replacement with another cheap glass Barlow is possible. I appreciate suggestions that it won’t be necessary but I’d like to know if it’s possible. If anyone knows that please speak up.

#432 Mitrovarr

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Posted 25 April 2021 - 10:04 AM

The corrector isn't a barlow lens.

The lens in the focuser of a Bird Jones scope is a correcting element that also slows the scope down. If you replace it with a barlow, what you'll have will be a F 4.4 newtonian reflector with a spherical mirror and a barlow. It's going to be horrible because of the speed of the primary element and lack of parabolization (which the actual Bird Jones corrector lens tries to correct for).

Edited by Mitrovarr, 25 April 2021 - 10:08 AM.

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#433 Star Geezer

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Posted 25 April 2021 - 09:39 PM

That would be true if the Powerseeker 127 or similar scopes was actually a Bird Jones. An actual Bird-Jones uses a corrector between the primary and secondary mirrors usually attached to the secondary. The lens inside the focuser is nothing more than a simple Barlow. The problem with replacing it is finding a Barlow lens with the same diameter and thickness.


Edited by Star Geezer, 25 April 2021 - 09:40 PM.


#434 Mitrovarr

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Posted 25 April 2021 - 11:51 PM

Surely it can't just be a barlow, can it? With a F/4.4 spherical primary the optical quality would be atrocious! And I've played with one and it wasn't that bad.

Even though it is not a true Bird Jones as you say, the lens has to be more than just a barlow.
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#435 Star Geezer

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Posted 26 April 2021 - 07:44 AM

I own the Powerseeker 127; I don’t think the view is bad at all. I also have a long tube 4.5” f/8 with a spherical primary and the view is not bad in it either. The Barlow effectively extends the focal length of the Powerseeker to a focal ratio of 8. What would be the difference?

 

Comparing the Powerseeker Barlow to my 2x shorty by holding each a foot away from my eye looking at a light bulb appears identical. I observe no indication it does anything more.



#436 Mitrovarr

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Posted 26 April 2021 - 09:37 AM

A F/4.4 scope with a 2x barlow isn't the same as a F/8.8 scope. Basically, since a barlow comes after the primary in the optical chain, the effect on the scope's speed doesn't affect the primary. So it doesn't reduce the need for parabolization at all.

Correction is subtle, you probably wouldn't be able to see it naked eye. I mean, naked eye, you can't even tell a SCT corrector isn't just a flat window, but if you replace it with a flat the scope is completely ruined.

#437 Sky Muse

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Posted 29 June 2021 - 04:45 AM

I'll tell you that. I have an AstroMaster 114mm bird jones, which is my grab 'n' go scope. The real deficiency with these entry level bird jones scopes isn't the optics, which are not bad at all (although the corrector does make collimation a bit more involved). The deficiency is the plastic focusers, and the undersized mounts and tripods.

Squaring and truing the draw-tube to the focusser's housing, replacing the rubber-grommets with metal-springs within the primary-cell, is all that's needed to successfully collimate the telescope, and for sharp, pleasing images at the higher and highest powers of which a 127mm aperture is capable.  The included 4mm produces 250x with this telescope.  That's only 50x-per-inch of aperture, to be readily expected from any reflector, and so I have happy realised with this one.  It will be pushed further than that, in time.

 

I'm not done testing this telescope, no; nor with this thread.  Once the renovation of my new EQ5-class equatorial is completed, also motorised, I expect even more wondrous observances to be forthcoming, and with afocal-shots to document.


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#438 xvariablestarx

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Posted 12 July 2021 - 08:53 AM

You almost make me want to rebuy one these Powerseekers 127 eq, just to best it, after it bested me on my first encounter with it. Well done on the mods, it was immensely entertaining reading about them,


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