I have the following: Baader 2" glass path corrector for refractors, SC and other systems. Extension factor 1.8x.
I have tested it with various diagonals and in 3 high quality refractors with my Mark V Binoviewer.
Everything looks good in my 180mm F7 and 101mm Petzval F5.4 refractors. But in my 140mm Petzval F5 refractor the stars appear out of collimation on regular stars as well as on an artificial star tested indoors. When I replace the 1.8X GPC with the smaller 1.7X GPC or 2.6X GPC everything looks good. The scope has perfect collimation. However, when I use the 1.8X GPC something is out. It doesn't really make sense so I am wondering if you know what might be the problem. Perhaps F5 is too fast for the 1.8X GPC. Is that correct or could it be something else I am overlooking?
The 1.7x version (2" GPC only) is designed to correct the coma of Newtonian telescopes and work down to f/3.5.
The 1.8x model is designed to work perfectly with refractor telescopes from f/8 to f/6. The design dates back to the days of Carl Zeiss APQ-Apochromates and was done by the APQ-designer, Dr. Pudenz.
We are sorry that the 1.8x (Refractor-)GPC does not perform to your expectation at f/5, but this is the fate of every specialised design, made to perform 100 % at the target application.
For example, a 1,25x or 1,70 GPC on top of the 1,7x newtonian GPC with a Mark V binoviewer. That would give a nice flexibility.
The GPC for Newtonians corrects the coma as well as the color aberrations of the prisms inside of the binoviewer, the other GPCs correct onla for the color aberrations.
The disadvantage is that you must use the T-2 Maxbright mirror diagonal (#2456100) and can't use different GPCs to achieve different magnifications with only one pair of eyepieces.
On the other hand, you gain the most back focus – about 80 mm instead of 20-65mm with the smaller GPCs.
I probably haven't explained me well. I wanted to say what difference is there between these two elements:
I am wondering if I can use the 1.8x glass path in front of the Baader T2 Zeiss prism + maxbright binoviewer? I see it is just recommended to be used in front of the mirror diagonal, not sure if it will perform worse in prism diagonal?
EAN Code 4047825011114 Manufacturer Baader Planetarium SKU (#) 2456305 Weight (NETTO) 0.263 Inner Connection (lens sided) Thread, M48 Outer Connection (lens sided) Barrel, 2" (50,8mm) Outer Connection (eyepiece/-camera-sided) Thread, T-2 (M42 x 0,75) Magnification (x) 1 : 1,80 Outer Diameter 54 mm Barrel Size (in) 2" Optical Design Glaspath Corrector compatible telescopes Refractors, Schmidt-Cassegrain
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