Our HORIZON ULTRA and POLARIS models have a combined dip and index adjustment on the drum screw. On the BOBBY SCHENK, only the index error can be corrected at the drum screw.
The index error, which can also be adjusted on the horizon mirror, can be corrected on an extra scale on the drum screw. It means that this error does not have to be taken into account in the calculations.
Same applies to the height of eye (dip) adjustment. With this scale, the height of eye can be preset independently of the index error and does not have to be taken into account in the calculations e.g. the value for zero has to be selected in the table.
In practice, the height of eye (dip) is rarely adjusted, e.g. for observations on a particular ship or voyage.
In the case of the combined adjustment the left scale is for adjusting the height of eye (dip), and the right scale is for correcting the index error.
It is important to note that the adjustment of the height of eye (dip) must be carried out before the index error correction.
The example shows a combined adjustment at the drum screw for the following values:
- Height of eye (dip) = 3 Metres
- Index error = -4'
| 1.) Height of eye (dip) adjustment | |
 | Loosen the screw to be able to turn the ring with the two scales |
 | Set the white dot to the third line (3m) on the left scale |
| | Fasten the screw to fix the ring with the two scales |
|
2.) Index error adjustment | |
 | Loosen the red drum screw (by holding the black drum part in the right side with the other hand) |
 | Turn the vernier scale and set the white line to -4' on the right scale |
 | Fasten the red drum screw to fix the vernier (by holding the black drum part in the right side with the other hand) |
 | Final setting for 3m height of eye (dip) and in index error of -4' |
