Sternwarte am Wallgarten

special projekts (still under work...)

on this page you can find "very special" projects. Whenever you want to start with a similar projekt you can profit from the collected experience.

The necessary working steps are described here with the shortest possible explanations, feel free to contact me for more information:

1) BADDER-FluoritFlatfieldConverter (3x-8x) for CANON EF Lenses (fixed magnification, main application: Astrophotography)

2) BAADER-FluoritFlatfieldConverter (3x-8x) for CANON EF Lenses (variable magnification per servo electronics, main application: Nature photography)

3) Remote control for LHiresIII ( spectrograph with stepper electronics, infrared and serial (per USB) remote control, full integration of the shelyak motorized calibration and flat lamp electronics


Top 1)

years ago i decided to start to work on a special project. Is there a chance to connect a BAADER-Fluorit Flatfield Converter to Canon EF-lenses? And the answer is: yes, you can do it for lenses with enough space at the end of the lens. All lenses with an integrated filter holder at the end of the lens and many more other lenses fullfill this criterion, for example: CANON EF400mm/f2.8 L IS USM (integrated filterholder), CANON EF 100-400mm/f4.5-5.6 L IS USM (no filterholder), CANON EF 70-200/f2.8 L IS USM (no filterholder)...All lenses which can be connected to the standard CANON Extenders III are possible. Dependent on the available space at the end of the lens the maximum magnification factor differs, because at higher magnifications the frontlens of the modified FFC (in reality the new housing of the FFC) will touch the backlens of the CANON lens. And be carefull with zoom lenses: very often the backlens will move and change the available free space at the end of the lens! The next diagram shows the dependence of available space and the reachable magnification:

...diagram will follow

the necessary working steps are:

you must buy a BAADER-FFC, expensive :-(

buy a lens holder tube and lens retaining rings from

1x SM30L20, included is a lens retaining ring M30.5x0.5mm

1x SM30RR additinal lens retainng ring M30.5x0.5mm

1x SM33RR lens retaining ring M33.5x0.5

buy a few astroadapters:

...details will follow

send the lens holder tube and the following two diagrams to an optomechanical expert, for example He will produce a new housing for the FFC lenses, which will partly fit into the CANON lenses. The second diagram is a new adapter for mounting of the modified lens tube:

modifications for THORLABS lens tube

new mounting adapter for modified lens tube

demount the lenses from the original BAADER-FFC (you will loose your guaranty!) and mount the two lenses (every lens is a doublet) into its new housing (the flat side of the doublets is always outside). The inner distance of the two lens doublets must be 19.8mm and you have to adjust the distance with the first M30.5x0.5mm lens retaining ring. If the first retaining ring is in the correct position, put the lens doublet on the retaining ring and fix the lens with the second retaining ring. Take care not to applicate any pressure to the doublets! Much more better it would be to use retaining rings with integrated rubbers, but until this date i have not found this parts). Similar to the original CANON Extenders the new housing will fit into the CANON lens.


TOP 2)

...more information will follow (12/2022)

TOP 3)

...more information will follow (1/2023).