Equinox Systems GEMINI Manuel d'utilisateur télécharger pdf (Page 40)

Gemini Users Manual 35

with some type of reticle, and watching for the star to drift north or south as the mount

tracks in RA. Depending on where the star is in the sky and whether it drifts north or

south, you can determine which way to move the mount in elevation or azimuth. You

then repeat the process until you see no drift for 5 to 15 minutes. The longer you can go

without any north/south drift, the better polar aligned you are.

Of course, stars used for drift aligning are also subject to refraction. Using a star near the

eastern or western horizon aligns the telescope to a pole that is shifted slightly toward the

zenith (as proposed in the King method.) Experienced astrophotographers recommend

that a star you choose for drift alignment be near the object that is to be photographed.

There are many good references on the web to give you detailed instructions on how to

do drift alignment.

3.4.2.3 Gemini Polar Alignment Tools

Gemini provides two tools to help you achieve fairly accurate polar alignment. They are

“Polar Align Assist” and “Polar Axis Correction.” Both are available as submenus of

“Align Telescope.”

You can use the Polar Align Assist to get close to polar alignment when you first start the

system, especially if you cannot use a polar alignment scope. You can then use Polar

Axis Correction to refine your polar alignment after you have built a good pointing model

using several “Additional Align” commands.

Polar Align Assist

After you have cold started and completed the first “Align Telescope→Synchronize,”

select the “Align Telescope→Polar Al. Assist” menu item. You will be in the menu of

stars you can use for polar alignment.

You will need to select 2 stars for this alignment process. The first one should be near

the celestial equator (Dec. near 0) and within about 20° of the eastern or western horizon.

The other star should be near the meridian (such as Polaris in the northern hemisphere).

Use the DEC buttons to scroll through the list of stars and select the first one by using the

RA+ button. Gemini will display “Calculating…” briefly and then once again display the

menu of stars. Scroll through the list and select the second star.

After you use the RA+ button to select the second star, the mount will slew to the first

star. Once it reaches the star, “center object” will appear on the display. If the star is the

one near the meridian, center the star only using the mount’s elevation adjustment knob

(ignore azimuth). If it is in the western or eastern part of the sky, center the star using

only the mount’s azimuth adjustment knob (ignore elevation). Having done this,

completely center the star in both RA and Dec. using the Hand Controller.

Press the MENU button and the telescope will slew to the other star. Center it using the

procedure described above. Repeat this about 3 times, each time pressing the MENU

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 136 137

Pas de commentaire

Equinox Systems GEMINI Manuel d'utilisateur Page 40