3
Selecting an object in StarTrak
To select an object, press the long 'spacebar' at the bottom of the keyboard. This will then prompt you for the name of an object, so type in the object name (in either upper-case or lower-case letters - it doesn't matter) and press the Enter key (at the right-hand side of the keyboard).
Figure 3.1
The object name you supply might be a Messier number (e.g. m42) or an NGC number (e.g. ngc1976) or some other name (e.g. orion nebula). You can save yourself some typing by using the asterisk 'wildcard' character - for example,
ori
* (followed by Enter)
Figure 3.2
will find M42 (NGC1976) - the Orion Nebula. Similarly, if you were to type
and
* (followed by Enter)this would find the Andromeda Spiral galaxy.
When you use a wildcard () character in this way, StarTrak finds the first object with a name which matches. This may not be the object you want - for example,
alpha
*finds Altair (Alpha Aquilae); if you wanted Arcturus (Alpha Bootis) you would need to type
alpha b
*or possibly
arct
*or
Arct
*(Remember, you can type in upper-case or lower-case.)
Listing the objects in the database
You can list the objects in the StarTrak database. To do this, select the List option from the ‘Object’ menu. You will then be prompted for a ‘wildcarded’ object name, for example,
*
matches all objects, *neb* will list all the nebulae, *Ursa Maj* will list those objects belonging to Ursa Major, and so on. When you have a list of such objects on your screen (up to 6 can be displayed on one ‘page’ of screen), you can press Enter for the next (or previous) page of matching objects. When you see an object of interest, use the up or down arrow keys to move to that object, and press Enter. StarTrak will then display the details and position of that object. This gives another way of choosing an object, in addition to the method described at the start of this chapter.
Setting up your telescope (details for a Dobsonian telescope)
If your telescope has a Dobsonian mount, the azimuth circle will probably be made from a thin circular sheet, mounted horizontally between the rocker box and the supporting base. This azimuth setting circle will have a central hole to accommodate the telescope's azimuth pivot (this hole should be a good fit with the azimuth pivot), and three cut-outs to accommodate the telescope's PTFE azimuth support pads. These three cut-outs should be generous, to permit some rotation of the azimuth setting circle when setting up. On the rocker box there will be a pointer which (as the telescope is turned) sweeps over the degree markings on the azimuth setting circle.
On the altitude pivot there will be an altitude scale (in degrees from zero to 90). Typically this will be in the form of a 0-90 scale fixed to the inside surface of the pivot tube, with a pointer attached to the body of the rocker box.
To set up your telescope for observing, assemble the Dobsonian mount with the azimuth setting circle in approximately the correct position (precise alignment comes later). The telescope base should be horizontal - use a spirit level if you have one. Point the telescope at a star which you can easily identify - Polaris is the obvious choice if you are in the Northern hemisphere. Use StarTrak to find the exact azimuth value for that star, and rotate the azimuth setting circle relative to the telescope until the star's azimuth value on the setting circle is aligned with the pointer on the rocker box. The azimuth circle is now precisely aligned.
Pointing the telescope (details for an altazimuth mount, such as a Dobsonian)
To find a star, use StarTrak to obtain an altitude and azimuth readout, as described earlier. Rotate the telescope so that its azimuth angle matches the azimuth readout from StarTrak. Remember that the azimuth angle increases in a clockwise sense.
Adjust the inclination of the telescope so that its altitude angle matches the altitude readout from StarTrak.
The telescope is now pointing at the object.
As the Earth rotates, you will need to track the object with the telescope if the object is to remain in the field of view. If you are away from the telescope for a few minutes, when you return you may find that the object has moved out of the field of view. If this happens, you can take the latest azimuth and altitude readings from StarTrak (remember, StarTrak will be updating these for you every second) and redirect the telescope accordingly.
Esc key
A reminder: if you press the Esc key (at the top left of the keyboard) partway through an operation in StarTrak, this will abandon that operation. For example, if you are partway through the steps above (to change the object you wish to view), if you press Esc then the screen will return to showing you the previous object.