6 replies to this topic

[Victor Martinez]

Hi,
I have verified that the 2.6X GPC installed directly between the 2" Nosepiece and the Baader Maxbright II, focuses on my Newton telescope. Since these GPCs are designed for use in refractors, could anyone tell me if the GPC would introduce any optical aberration to the image provided by the Newton telescope?.
Thank you.

[Astrojensen]

They're not designed for refractors per se. They are designed to partially or fully eliminate the light path length through the binoviewer, as well as correct for the spherical and chromatic aberration introduced by the prisms in the binoviewer. 

 

 

Clear skies!

Thomas, Denmark

[vkhastro1]

For Newtonian reflectors Baader specifically makes a 2” Newtonian 1.7X Coma Correcting Glasspath Compensator.

It works perfectly with my Baader Maxbright binoviewer.

[Victor Martinez]

They're not designed for refractors per se. They are designed to partially or fully eliminate the light path length through the binoviewer, as well as correct for the spherical and chromatic aberration introduced by the prisms in the binoviewer. 

 

 

Clear skies!

Thomas, Denmark

I understand then that the quality of the image is not affected in any way, right?

[Victor Martinez]

For Newtonian reflectors Baader specifically makes a 2” Newtonian 1.7X Coma Correcting Glasspath Compensator.

It works perfectly with my Baader Maxbright binoviewer.

Thanks, I already use one

[Eddgie]

I understand then that the quality of the image is not affected in any way, right?

The GPC improves the quality of the image. The faster the telescope, the more affect it has.

 

The opposite is true as well. The slower the telescope, or the slower the effective focal ratio, the less the GPC helps.  At f/10, there really isn't any need for a GPC, and if you use a 2x Barlow in an f/5 scope, it will do almost as much as the GPC would do to improve the image. 

 

The reason the GPC or a Barlow improves the image is that the steeper that the light cone is, the more spherochromatism error will be induced by the prisms in a binoviewer. If the light comes in completely color free, as it passes through the prisms, different colors in the spectrum will have more and more spherical aberration. The green will have a small amount, but the red and blue will have much more.  Since the eye is not very sensitive to red, you may not see this, but you start to see the blue fringe on planet and lunar detail, and this lowers contrast. Double Stars will not be shown in their true color because the blue component is taken out of the Airy disk and makes a glow around the star.

 

If a fast scope does not need a GPC to reach focus and the error does not bother one, then there is nothing wrong with using it that way, but I recommend that a Barlow or GPC be used for high resolution observing (solar system objects and double stars).  

[Victor Martinez]

Thanks Eddgie