Why won't the Baader Alan Gee Mark II work with my Denkmeier or Tele Vue binoviewer?
The Alan Gee Mark II's optical design requires extremely close spacing to the binoviewer's prisms to function correctly. Most binoviewers have a long optical path (e.g., through a power-switch diagonal) that makes this physically impossible. It is specifically designed for direct, close-coupled attachment to certain Baader, Zeiss, and Celestron models.
Can I use the Alan Gee Mark II for astrophotography?
This telecompressor is not recommended for general astrophotography. It is optimized for visual use and creating a flat field for the human eye within a binoviewer. Achieving the correct spacing with a camera sensor, filter wheel, and off-axis guider is typically not feasible and will result in poor optical correction.
How does the Alan Gee Mark II affect the image brightness in my Celestron 11" SCT?
By reducing the telescope's effective focal ratio, the telecompressor concentrates the same amount of light into a smaller area. This creates a brighter image surface, which is especially beneficial for observing faint, extended objects like the Veil Nebula (NGC 6960). The background sky will appear brighter, but the nebula's contrast against it will increase.
What is the "close coupling" mentioned for the Alan Gee Mark II?
"Close coupling" refers to the minimal physical distance required between the last lens of the telecompressor and the focal plane (or in this case, the prisms of the binoviewer). The optical corrections of the Alan Gee design are only valid at this specific, short distance. Increasing this distance will introduce significant aberrations like coma and field curvature.
Do I need to modify my SCT to use the Baader Alan Gee Mark II?
No permanent modification is needed, but you will need the correct adapters to thread the telecompressor directly to your binoviewer and then attach the entire assembly to your telescope's visual back. It replaces the standard diagonal in your optical train.
Will this telecompressor help me fit the entire Orion Nebula (M42) in the view of my 8" SCT with a binoviewer?
Yes, this is precisely the kind of application the Alan Gee Mark II is designed for. A standard 8" SCT with a binoviewer often cannot frame the full extent of M42's nebulosity. This telecompressor widens the field sufficiently to capture the entire object, from the Trapezium core to the fainter outer loops, in a single immersive view.
