NorthStar Navigation Echo Sounder NorthStar 491 - Manual (Page 23)

491 Echo Sounder Operations Manual Page 19
When using the zoom feature (which also splits the screen
into halves), both sides of the screen always display the same
frequency.
Zooming in and out
On the ECHO screen, the echo sounder’s zoom feature
expands a portion of the echoes. You can examine closely any
part of the water column, to determine the composition of the
bottom or look at the echoes of fish, rocks, or wrecks. When
fishing, the zoom function is useful for showing a detailed
view of any echoes below the vessel.
Choosing the zoom
scale
Press IN to zoom in and increase the magnification of the
echoes you see below the top edge of the marker. Press OUT to
zoom out and increase the amount of water seen.
You can choose from any of six depth scales for the magnified
echoes. These scales cover the same depths regardless of the
scale of the original echoes.
The available scales are: 15’, 30’, 60’, 120’, 240’ and 480’ when
using units of “feet.” Similar scales are available for the other
depth units.
NOTE:
When zoom is in use, only a single frequency is displayed.
Unzoomed echoes are on the right, and the same frequency is
shown magnified on the left. Whatever frequency was previously
shown on the left is replaced by a magnified view of the right side.
NOTE:
You cannot zoom out to a scale that shows more water than the
original picture. For example, if the original picture is set to a scale
of 50’, the only zoom scales available will be 15’ and 30’.
Choosing a zoom
mode
Press ZOOM on the ECHO screen to cycle through the four
zoom modes (and choose the one you want):
• bottom zoom
• bottom lock
• bottom lock/center