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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.
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.
- how much approximately would the 1.7x factor increase;
- would that additional lightpath negatively affect the coma-correcting properties?
A moderate chang in the distance of some cm (like 4 cm for a T-2-prism) doesn't harm the image quality too much.
The backfocus determines only the distance between the end of the focuser and the camera/eyepiece.
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|Net weight (kg)||0.26|
|Inner Connection (lens sided)||Thread, M48|
|Outer Connection (lens sided)||Barrel, 2" (50,8mm)|
|Inner Connection (eyepiece/-camera-sided)||Dovetail ring clamp, T-2 (M42 x 0,75)|
|Outer Diameter||54 mm|
|Optical Design||Glaspath Corrector|