The simplest way to track celestial bodies moving due to diurnal motion is to use an equatorial ritual stand, which is indeed much more convenient than a theodolite. As long as you understand the essentials of use, visual inspection or photography will produce good results. The starry sky at night, centered on the axis of rotation connecting the North and South Celestial Pole, rotates once a day, which is called diurnal motion. On the mount of an equatorial mount, extending the polar axis (or right ascension axis) toward the north celestial pole (or toward the south celestial pole in the southern hemisphere) allows you to simply track the movement of the stars. In other words, make the polar axis of the equatorial mount parallel to the earth's axis. This operation is called polar axis adjustment. When using the equatorial mount, you must not forget to align it with the polar axis in advance.
There are two types of equatorial mounts: those with right ascension and declination micro-rods, and those with polar axis motor tracking. Star tracking with a micro-lever is more convenient than the longitude and latitude platform, but it requires continuous manual operation to continue tracking. If the budget allows, it is best to use a motor tracking type, which will be much more convenient. The overall balance of the declination axis and polar axis of the equatorial mount must be adjusted. If the balance is well adjusted, the lens barrel will remain stationary when the fixing screw is loosened, and the equatorial mount will operate smoothly and be used smoothly.
In recent years, manufacturers have added GOTO functions to advanced equatorial mounts, allowing users to instruct the telescope to automatically point to the observation target. However, it consumes a lot of power, so you need to carry a large battery when traveling in the field.
There are many types of equatorial mounts. There are two types of equatorial mounts most commonly used by amateur astronomers: German-style and forked equatorial mounts. The German style equatorial mount is suitable for refractive, reflective and catadioptric telescopes. The forked equatorial mount is generally used with a catadioptric telescope. The advantage of the fork-type equatorial mount over the German type is that it does not require a balance weight, which reduces the weight of the instrument and facilitates field observation. However, the stability of the amateur-grade forked equatorial mount is not as good as that of the German equatorial mount. The equatorial mount used in the Boguan series of telescopes is a German-style equatorial mount.
Celestial objects visible to the naked eye can be aligned with a finderscope, and the equatorial mount is used for fine-tuning tracking. Deep sky objects must be found using the hour angle and declination disk of the equatorial mount.
The equatorial mount has three axes:
1. Horizontal axis. Perpendicular to the ground plane, the lower end is connected to the tripod stand, the upper end is connected to the polar axis, and has a ground level dial. Rotate around the horizon axis to adjust the telescope's azimuth angle.
2. polar axis. One end is connected to the horizon axis, and the horizon angle can be adjusted by moving the polar axis up and down. The other end is connected to the declination axis at an angle of 90o, and is equipped with an hour angle disk, which is used to adjust the hour angle (right ascension) of the telescope pointing.
3. Declination axis. It is connected to the polar axis at 90o, and the upper end is connected to the main lens barrel at 90o to ensure that the lens tube is parallel to the polar axis. The lower end is connected to a counterweight and equipped with a declination plate, which is used to adjust the declination of the telescope pointing. Step one: polar axis adjustment. Make the telescope's polar axis parallel to the Earth's axis of rotation, pointing toward the North Celestial Pole.
1. The primary mirror is connected to the equatorial mount and tripod, and the leg with the "N" mark is placed due north. Adjust the height of the tripod so that the tripod table is level. 2. Loosen the polar axis (right ascension axis) tightening screw and rotate the primary mirror to the left or right. Loosen the balance weight tightening screw and move the balance weight to balance the telescope and the weight. Turn the telescope back up and tighten the screws.
3. Loosen the horizon tightening screw, turn the equatorial mount so that the polar axis (telescope) points north (compass orientation), and tighten the screw.
4. Loosen the tightening screw connecting the polar axis and the horizon axis, move the polar axis up and down to align the pointer with the geographical latitude of the observation location (for example: the geographical latitude of Jinan is 36.6o, that is, 36.6o north latitude), and tighten the screw.
5. Loosen the declination axis tightening screw, rotate the telescope so that it is parallel to the polar axis (that is, parallel to the local longitude coil), and tighten the screw.
6. Use a telescope (or a finderscope with the optical axis adjusted) to see if Polaris is in the center of the field of view. If there is a deviation, you need to make fine adjustments to the azimuth and altitude of the polar axis until Polaris is in the center of the field of view. No more movement.
7. Turn the hour angle dial to align the pointer with zero hour (0h); turn the declination dial to align the pointer with 90o (some have been fixed at 90o or 0o at the factory). At this point, your telescope is completely parallel to the Earth's axis of rotation and the meridian of the observation point. No matter how the earth rotates, the telescope is always pointed towards the North Star. Special reminder: After the polar axis is adjusted, the tripod, polar axis azimuth angle, and altitude angle cannot move at all, otherwise it will have to be readjusted. The North Celestial Pole does not completely coincide with Polaris, but is tilted 1° toward Beta Ursa Minor.
Step 2: Calculate the local sidereal time at the observation point. Example: Calculate the local sidereal time of Jinan at 19:00 Beijing time on May 1, 2002. 1. From the astronomical almanac of that year (one published annually by the Beijing Planetarium), it was found that the local sidereal time of 0h Greenwich on May 1, 2002 was: 14h35m00s.
2． From relevant data, it is found that the geographical longitude of Jinan (observation point) is 117o east longitude, which is converted into hour angle 7h48m00s (15o=1h, 1o=4m, 1’=4s).
3. Use the following formula to calculate s=So (m north -8h λ) (m north -8h)*0.002738 where s is local sidereal time, the hour angle of the vernal equinox γ measured at the observation point So universal time 0h Greenwich local sidereal time m north Beijing local normal time λ Geographical longitude (hour angle) of the observation point 8h Beijing time is the East Eighth Time Zone standard zone time 0.002738 Conversion coefficient (1/365.2422) Substitute the known data into the formula S=14h35m00s (19h00m00s-8h 7h48m00s) (19h00m00s-8h )*0.002738 =14h35m00s 18h48m00s 00h1m48s =33h24m48s Because the result is greater than 24h, we need to convert 24h into one day and subtract 24h. S=43h25m13s-24h=19h25m13s Answer: The local sidereal time in Jinan at 19h00m00s Beijing time on May 1, 2002 is 09h24m48s on May 2.
Step 3: Calculate the hour angle (t) of the observed celestial body at the time of observation. t: Starting from the local meridian circle, the entire circle is divided into 24 hours from east to west (each hour is equal to 15o). Example: M65 (extragalactic galaxy) in Leo.
1. The coordinates of this celestial body on the celestial sphere were found to be: right ascension α=11h18m00s; declination δ=13o13’. Right ascension α: The longitude of a celestial body on the celestial sphere. Taking the longitude and latitude passing through the vernal equinox γ as the 0 point, the circle is divided into 24 hours from west to east. Declination δ: The latitude of a celestial body on the celestial sphere, with the celestial equator as 0o, positive to the north and negative to the south, each divided into 90o.
2． Use the formula to calculate t=s-α t=09h24m48s-11h18m00s= -1h53m12s
Step 4: Operate the telescope to align it with the celestial body.
1. Loosen the declination axis tightening screw, rotate the main mirror, first align it with the celestial equator (declination disk 0o), then rotate δ=13o13’ north, align it with the declination disk pointer, and tighten the screw.
2． Loosen the polar axis tightening screw, rotate the telescope eastward around the polar axis (hour angle t is negative), align the hour angle -1h53m12s of M65 with the hour angle dial pointer, and tighten the screw.
3. First observe m65 with a low magnification lens. If it is not in the center of the field of view, use the right ascension and declination fine-adjustment handwheel to adjust the celestial body to the center of the field of view. Due to the rotation of the earth, the target will gradually move out of the field of view, so you must constantly use the fine-tuning handwheel to track it. If it is an automatic tracking equatorial mount, just turn on the switch.
Special reminder: When the celestial body is observed again the next day, due to the rotation of the earth, the hour angle of the celestial body will increase by 3m56s and become -1h49m16s.