about 16 feet focal length. Spot spectra taken with this instrument

1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z
1928MNRAS..89..178Z