Three Fathom Observatory
Stewart Yeung








Current Special Feature       

Special Feature in July 2008

Image Quality of the Lumicon LG1080 Focal Reducer


Threaded in the nosepiece of ST-10XME and inserted into an Eye-Opener 2" adapter, this focal reducer achieve a focal ratio of F/5.8.

The reducer is placed in juxtaposition to the baffle tube.

From the photos taken with the two setups below, it seems  that the resultant image quality is comparable to that of the native F/10 system.

M13 at F/5.8

M15 at Native F/10

Download original TIFF files :

M13                                    M15



M27 at F/5.8

M27 at Native F/10

Download original TIFF files :

                                                                                                                                              M27                                  M27


M16 at F/5.8

M22 at Native F/10

Download original TIFF files :

M16                               M22


A perturbing sign is the oval stars in the 3rd and 4th quadrants in both setup.


Thanks to Stan Moore for his feedback. Update on 6 August :

1.    More short-exposure images in sharper focus have to be shot for further analyses.

2.    Future investigation should be directed towards collimation, perpendicularity of the optical components

(focal reducer, connection adaptor tubes, camera nose-piece).

3.    Rotation of the camera assembly will give more clues.