5 replies to this topic

[Corycool]

Is there a big difference in quality between the Celestron Omni 2x barlow and the Explore Scientific 2x Focal Extender? Has anyone done a comparison? Thanks!

[vtornado]

I have not done a comparison.

 

The Omni is a barlow or telenegative.   It is a cemented doublet that diverges the image.

 

The ES is a telecentric.  It two cemented doublets one diverges the image the other re-parallizes the rays. 

 

• The telecentric magnifying factor does not change with the eyepiece distance.  (may not be an issue)
• The telecentric will not increase the eye relief.  (may not be an issue, especially for older design eyepieces with short eye relief)
• The telecentric will not vignette low power eyepieces. (may not be an issue unless you are using with large field stops)

 

A great barlow is nearly invisible in the optical train.  Like TV 2x.  I also have a vingtage long barlow that is also very good.   I used the Omni (GSO) on Jupiter and moon, it was not quite as good as the better barlows but just a whisker behind.

[JoeBlow]

The 1.25" Celestron Omni 2x badly vignettes my 26mm and 20mm plossls. Next time I'll try it with my shorter focal length Plossls.

Edited by JoeBlow, 28 April 2025 - 06:45 PM.

[sevenofnine]

I'm impressed with the views through the sealed ES 2X FE. I like the fact that it doesn't double the ER of the eyepiece being used. The views using AT Paradigm/Agena Starguider ED's are excellent 

[T1R2]

I never used the Omni, but the ES is excellent. I've never noticed any vignetting but I've only used it with a 32mm plossl once or twice. 

[vrodriguez2324]

The 1.25" Celestron Omni 2x badly vignettes my 26mm and 20mm plossls. Next time I'll try it with my shorter focal length Plossls.

I have the 1.25 Celestron Omni 2x and the Celestron Xcel-LX 2x (more like 2.3x)

 

They both vignette my 24mm Panoptic, so I never used them with it because of that reason. 

 

In my 100 degree set (20 Optimus - 13 Ethos - 9 Optimus - 7 APM - 5.5 ES - 4.7 Optimus - 3.6 Optimus) I have tried them with excellent levels of success!  I can't use it with the 20 Optimus for obvious reasons but they work amazing in the 13E and all the way down. If there was any vignetting I didn't notice it. 

 

In my old LER Set (31NT5 - 22NT4 - 17.5M - 14M - 12.5M  - 9M - 6.5M - 4.5M) They did great in all of the Morpheus, which I no longer have  . 

 

I am sure there is better than the OMNI 2x but I was impressed with it. Can't beat the price for sure. The detachable lens cell also affords additional value and options.

 

-Victor

Edited by vrodriguez2324, 01 May 2025 - 09:04 AM.