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Celestron Luminos 2" 2.5x telecentric barlow

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#26 Starman81

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Posted 27 March 2015 - 09:46 AM

Any magnification increase observed from increasing the distance of the eyepiece from the standard ep position in the barlow? That's a characteristic of a Barlow and not a TeleXtender/powermate type design. 

 

 

Syed,

Thanks for you report! Nice to hear it's optically good.

 

Im also wondering if it works like a telecentric focal extender or it's a telenegative Barlow?

Thanks.

 

I would say that it is not a telecentric, though I cannot claim that as fact. The reason I would say that is that the eye relief was clearly increased when using it with the 13 Ethos. I use the Ethos with the DioptRx accessory and I have to get in pretty close to it to take in the entire FOV so this makes me acutely aware of even very minor differences in eye relief. I have a few telecentric design barlows (TV 2" 2x Powermate, TV 1.25" 2.5x Powermate, ES 2x, ES 3x) and when using them I can tell that in use, they do not increase eye relief of the eyepiece that they are used with. 

 

I would guess that this Luminos barlow is a 3-element apochromatic design. Being so lightweight and yielding 2.5x magnification makes me think that it is the 2" version of the GSO 2.5x apochromatic barlow, which shares the same characteristics but in a 1.25" format.



#27 Peter Besenbruch

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Posted 27 March 2015 - 12:54 PM

I would say that it is not a telecentric, though I cannot claim that as fact. The reason I would say that is that the eye relief was clearly increased when using it with the 13 Ethos. I use the Ethos with the DioptRx accessory and I have to get in pretty close to it to take in the entire FOV so this makes me acutely aware of even very minor differences in eye relief.

 

...I would guess that this Luminos barlow is a 3-element apochromatic design.

 

Celestron advertises it as a 4 element Barlow. What's interesting are the lack of telecentric claims. I would guess you can have a 4 element Barlow that isn't telecentric in design.



#28 russell23

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Posted 12 June 2015 - 09:42 AM

Any more observing updates on the performance of this barlow? 

 

Dave



#29 Usquebae

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Posted 17 June 2015 - 10:03 AM

I am no keen tester of optics, but I have enjoyed mine.  My other two 2" Barlows are GSO 2x and Antares 1.6x.  I found the GSO doesn't play nice with some EPs and shows significant lateral color.  Antares has only been a joy to use and Luminos quality looks same so far.  I did see some ghosting on Jupiter but not severe.

I would caution owners that the upper lens of this Barlow is convex and seated rather higher in the housing than one might expect - just a little bit below the bottom orange ring you can see on the outside of the housing.  So anything extending beyond the rim of a 2" EP barrel may hit the glass.  The 2"/1.25" adapter sits nice and high, so there seems to be ample clearance to use two standard filters with a 1.25" EP, but both of my dual barrel EPs with the fixed protruding 1.25" barrel look as though they will smash the glass.

 

Magnification increases with distance from EP so not telecentric it seems.  My scale shows 10 3/8 oz with adapter, 7 1/4 oz without.     


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#30 Scanning4Comets

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Posted 21 September 2015 - 08:40 PM

I am also curious about this barlow since I needed a 4mm eyepiece again and can use it with my 10mm Pentax XW.

 

:grin:

 

Any more reports would be greatly appreciated !!!



#31 Scanning4Comets

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Posted 10 November 2015 - 03:41 AM

Bump....

 

More reviews on this one with a bit more info would be great !!!! 

 

:grin:



#32 Starman81

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Posted 10 November 2015 - 04:29 PM

I do have one and have used it on a few occasions, but not very much. That's not to say it isn't good, it is just that my use case for this specific barlow doesn't come up very often. I use the Luminos 2" 2.5x barlow exclusively for barlowing my 13 and 10 Ethos to give 5.2mm and 4mm equivalents.

 

Being a normal barlow and not telecentric, I appreciate the increase (though slight) of the eye relief since I use DioptRx on my Ethos eyepieces. The pupil behavior is still comfortable overall and there are no negative aberrations, such as EOFB, lateral CA or astigmatism that I can see added by the barlow. No issues with contrast or anything of the like.

 

However, I did not test the barlowed combinations head-to-head with any other eyepieces, barlowed or not to see if there are "better" options out there. For my needs, it works well while being practically transparent in the optical chain. 

 

One other plus is that it is nice and lightweight when used as a 2" barlow. A negative as that if you use the 1.25" eyepiece holder I found that the compression ring in it grips some 1.25" securely but not others, which was strange and something I have never come across in my experience when using any 2" to 1.25" reducers. This can be mitigated by using a different 2" to 1.25" reducer, of course. 

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  • 13 Ethos in Luminos.jpg


#33 Scanning4Comets

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Posted 10 November 2015 - 07:47 PM

Great new info Syed!

Thanks a lot for that! 

 

Two quick questions:

 

1. How far in is the lens from the top of the barlow housing?

2. How much "in focus" or "out focus" is needed when adding the barlow to your 10mm XW?

 

I need to know #2 the most as I would be using it with my 10mm XW, and I parfocalize my barlows as well.

 

#1 was a concern because I could use another EP in 2" more, (like the LVW's), and it would stick in further down the housing of the barlow.



#34 Starman81

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Posted 11 November 2015 - 12:59 AM

Great new info Syed!

Thanks a lot for that! 

 

Two quick questions:

 

1. How far in is the lens from the top of the barlow housing?

2. How much "in focus" or "out focus" is needed when adding the barlow to your 10mm XW?

 

I need to know #2 the most as I would be using it with my 10mm XW, and I parfocalize my barlows as well.

 

#1 was a concern because I could use another EP in 2" more, (like the LVW's), and it would stick in further down the housing of the barlow.

 

1. I have double-checked the barlow and contrary to usquebae's report, the upper lens in my Luminos barlow is not convex but is instead flat. That means that basically the full of 47mm from the top of the barlow housing down to the upper lens (when used in 2" mode) is usable. As you can see in the picture, the 13 Ethos dual-barrel is easily acommodated with 5-6mm to spare. 

 

2. Mark, I do not have an XW 10 anymore, but I do have an XW 20 and XW 7... I guess I could try with those next time out (?). 

Attached Thumbnails

  • 13 Ethos and Luminos.jpg


#35 Scanning4Comets

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Posted 11 November 2015 - 01:49 AM

 

Great new info Syed!

Thanks a lot for that! 

 

Two quick questions:

 

1. How far in is the lens from the top of the barlow housing?

2. How much "in focus" or "out focus" is needed when adding the barlow to your 10mm XW?

 

I need to know #2 the most as I would be using it with my 10mm XW, and I parfocalize my barlows as well.

 

#1 was a concern because I could use another EP in 2" more, (like the LVW's), and it would stick in further down the housing of the barlow.

 

1. I have double-checked the barlow and contrary to usquebae's report, the upper lens in my Luminos barlow is not convex but is instead flat. That means that basically the full of 47mm from the top of the barlow housing down to the upper lens (when used in 2" mode) is usable. As you can see in the picture, the 13 Ethos dual-barrel is easily acommodated with 5-6mm to spare. 

 

2. Mark, I do not have an XW 10 anymore, but I do have an XW 20 and XW 7... I guess I could try with those next time out (?). 

 

 

Excellent news Syed!

 

The 7mm XW would suffice as I have that as well and it is pretty much parfocal to my 10mm XW. Let me know what the "in focus" or "out focus" is with the 7mm XW after using it by itself, then with the barlow.

 

Thanks Syed,

 

This is so kind of you to let me know.

 

:waytogo:

 

-Mark



#36 faackanders2

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Posted 11 November 2015 - 08:30 PM

I did take receipt of it. Haven't tried it out with all the clouds recently, even got skunked for the triple transit :(.

 

I can confirm that it is very lightweight for being a 4-element 2" barlow. 11oz sounds right but no scale on hand to confirm. Comparable to the Antares 1.6x in weight (9 oz), except you get a 1.25" adapter, which adds that couple ounces, I'm sure. 4-element but no claims of 'telecentricity' anywhere on the box. Celestron does claim it is 'apochromatic'. 

 

Did the bright wall test with the 13 and 10 Ethos and found the preliminary findings to be good with regards to exit pupil behavior but won't really know until the barlow + eyepiece combo is plugged in a scope. 

 

Clear aperture is listed as 28mm, but I tried it with the 22T4 Nagler (31.1mm field stop) and could not see vignetting. I guess it was there but slight? Anyways, I don't have plans to use it with long f/l eyepieces. 

Triple transit required low power to fit them all in same FOV.



#37 Usquebae

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Posted 13 November 2015 - 11:46 PM

1. I have double-checked the barlow and contrary to usquebae's report, the upper lens in my Luminos barlow is not convex but is instead flat. That means that basically the full of 47mm from the top of the barlow housing down to the upper lens (when used in 2" mode) is usable. As you can see in the picture, the 13 Ethos dual-barrel is easily acommodated with 5-6mm to spare.

 

Weird!  I double-checked my own and the upper lens is seriously convex, reaching approximately to the top of the "L" in Luminos on the outer housing.  Apparently there are multiple types floating around out there.  I got mine from B&H.  It looks the same as your picture except that the screw juts out directly over the "S" in Luminos.  Btw, I have same issue with the 1.25" adapter.


Edited by Usquebae, 13 November 2015 - 11:58 PM.


#38 Starman81

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Posted 14 November 2015 - 01:53 AM

 

1. I have double-checked the barlow and contrary to usquebae's report, the upper lens in my Luminos barlow is not convex but is instead flat. That means that basically the full of 47mm from the top of the barlow housing down to the upper lens (when used in 2" mode) is usable. As you can see in the picture, the 13 Ethos dual-barrel is easily acommodated with 5-6mm to spare.

 

Weird!  I double-checked my own and the upper lens is seriously convex, reaching approximately to the top of the "L" in Luminos on the outer housing.  Apparently there are multiple types floating around out there.  I got mine from B&H.  It looks the same as your picture except that the screw juts out directly over the "S" in Luminos.  Btw, I have same issue with the 1.25" adapter.

 

 

Wow, your upper lens reaches the TOP of the "L" in Luminos??! That is pretty wild. Can you post a couple pics of your version one of the outside and one of the inside of the barlow? 



#39 Usquebae

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Posted 14 November 2015 - 02:36 AM

http://www.cloudynig...0482-luminos03/

http://www.cloudynig...0481-luminos02/



#40 Starman81

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Posted 14 November 2015 - 05:33 PM

 

That is quite telling. How did you even unscrew the barlow? Mine will not unscrew and believe me I tried!


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#41 Usquebae

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Posted 14 November 2015 - 08:24 PM

Unscrewing is a bit stiff - I think there's a gasket in there - but not difficult.  So, lenses and body are different.  I wonder if they function the same.  Mine has produced nice images but I haven't actually tested its power.  Will do so and report back.



#42 Scanning4Comets

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Posted 15 November 2015 - 01:39 AM

Unscrewing is a bit stiff - I think there's a gasket in there - but not difficult.  So, lenses and body are different.  I wonder if they function the same.  Mine has produced nice images but I haven't actually tested its power.  Will do so and report back.

 

Excellent! :waytogo:



#43 russell23

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Posted 02 June 2016 - 10:38 AM

Well I finally purchased one of these but have only had a couple chances to test it.  I was very impressed with how well baffled it is.  The barlow does not introduce any EOFB - which I was worried about because of the 19mm Luminos.

 

So it seems to be a very good barlow but I need to put it through more testing.


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#44 Scanning4Comets

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Posted 02 June 2016 - 11:23 AM

Well I finally purchased one of these but have only had a couple chances to test it.  I was very impressed with how well baffled it is.  The barlow does not introduce any EOFB - which I was worried about because of the 19mm Luminos.

 

So it seems to be a very good barlow but I need to put it through more testing.

 

This will be a great piece of info as I was quite interested in this barlow, but hesitated to get it due to no reviews out there. :grin:




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