The equatorial instrument is made to improve the shortcomings of the horizontal device.Its main purpose is to overcomeearth rotationThe influence on stargazing.A set of standardAstronomical telescopeOften bytelescope, equator instrument, foot rest and other components.
When using the equatorial instrument, first align its polar axis with the north celestial pole.(Ideally) After the telescope is fully aligned, the declination of the telescope towards any star does not need to be adjusted, but the telescope needs to rotate at a constant speed in the right ascension (or time angle) direction according to the travel speed of the star to keep the star in the field of view of the telescope.
Chinese name
Equatorial
Foreign name
equatorial instrument
Features
Disadvantages of improving the horizontal device
Purpose
Overcoming the influence of earth rotation on star watching
Grading
EQ1, EQ3, EQ5, EQ6, etc
Type
German equatorial instrument, British equatorial instrument, etc
The equatorial instrument is made to improve the shortcomings of the horizontal device.To talk about the equatorial instrument, we should first talk about the horizontal device.The horizontal type device is a common one, which is a bracket with two axes. The telescope is mounted on it, which can easily adjust the direction and height of pointing.For beginnersHorizontal deviceThere should be no problem in finding stars: point where you want to see!Don't know the position of the star you are looking for?Look at the star map.
It is not difficult to find stars through star maps.Of course, the premise is that you should be familiar with some constellations with more bright stars or directional functions throughout the day.For example, bear cub, bear, swan, centaur, scorpio, eagle, lyre, Orion, Pegasus, fairy, dog and lion can recognize other constellations through known constellations, which will be much easier.So I suggest that beginners should find a friend who already knows the constellation to guide them when they begin to recognize the stars.
However, there is an obvious disadvantage when looking at a star with an horizon telescope: it was originally aimed at a star, but after a while, the star "deviated", and the higher the magnification, the more obvious this phenomenon is.This is because every day the stars are doingDiurnal visual movement。In the horizon coordinate, two values describing the position of each star - azimuth andHorizon heightIt changes with time.If the telescope wants to point at a star all the time, it is necessary to adjust the elevation and azimuth of the telescope at the same time.Because the amount of change in the two directions is completely different, it will be quite difficult to track a star with such a device.
Equatorial
Equatorial
So the equatorial instrument came into being.As we all know, it is because of the rotation of the earth that the stars rise in the east and fall in the west.
Knowing the reason, it is not difficult to solve this problem. The earth rotates continuously from west to east, 360 degrees in 24 hours. We only need to design a device to make the telescope rotate at the same angular speed as the earth, but in the opposite direction (from east to west), and then we can eliminate the impact of the earth's rotation.
Theoretically, the coordinate system used by the equatorial instrument isEquatorial coordinate system。It is equivalent to a large grid rotating with stars.Since it rotates with the stars, the two values describing the position of each star - right ascension and right latitude are constant.Generally speaking, the equatorial instrument is a device that tries to make the telescope rotate with the grid.
usage method
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This speed is 360 degrees a day (because the earth rotates once a day).This is called automatic tracking.Of course, if you use a manual equator, you have to adjust the right ascension (or hour angle) knob at regular intervals, and the declination does not need to be adjusted (of course, this is the ideal situation, if the polar axis is not aligned accurately, you should also adjust the declination appropriately).There is no need to adjust both axes at the same time to facilitate tracking, which is the fundamental reason for using the equatorial instrument
Many popular astronomy books will teach you to find stars by calculating the time angle. But according to my experience, it is not convenient to use the time angle when making amateur observations, because when you have to calculate the stars first, you also need to know the right ascension and declination values of the celestial bodies you want to observe.In addition, the accuracy of the time angle disk makes it far more convenient to find stars than to use the star map directly.
Equatorial
Therefore, it has advantages only for those fixed telescopes with fixed bases and aligned polar axes, as well as those unfamiliar with constellations. In addition, it is really difficult to find stars directly with astronomical telescopes, because the field of view of the main mirror is often very small.Therefore, astronomical telescopes usually have a star finder with a large field of view, which is used to help find stars.Of course, it would be much easier to have a binocular mirror to help.This is why many experienced fans suggest beginners buy firstBinocularsBecause of.
It is often used to install long lens tubesRefracting telescope。The other end of the weft shaft is equipped with a counterweight.
② British
The latitudinal axis is in the middle of the polar axis, and the mirror cylinder and counterweight are located on both sides, which is suitable for lowerGeographic latitude。
③ Yoke or cradle type
Its advantage is that the deformation of the two axes under load does not affect the pointing accuracy.The disadvantage is that the area near the celestial pole cannot be observed.
④ Horseshoe style
It is often used for large telescopes.
⑤ Fork type
Commonly used for telescopes with short lens tubes and those with small declination changesSolar telescope。
classification
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Simple equatorial instrument
This level of equatorial instrument is generally used to call your own self-made equatorial instrument. It has equipment that can make one axis parallel to the earth, and one axis always moves towards stars without field rotation, such as the self-made door plate equatorial instrument.
EQ1 level
This level of equatorial instrument generally refers to the German EQ1 equatorial instrument. Without such things as motor hook, clutch and synchronous gear, it can align the polar axis with the north and south celestial poles. The right ascension rotates around the polar axis to track the stars. The common equatorial instrument is the simplest one. It has only one set of worm gear and worm mechanism, and can only use the adjusting rod to continuously adjust the longitude of the telescope.It is generally compatible with popular astronomical telescopes[1]。
EQ2 level
Equatorial instruments of this level are also common, and an additional set is added to EQ1Worm gearIn this way, continuous adjustment can be made in both directions of right ascension and declination through the adjustment mechanism.It basically meets the regulation requirements.In fact, there is no mention of EQ2 on the Internet. According to the description, the pictures of EQ2 and EQ1 are the same thing.
EQ3 level
On the basis of EQ2, the gears of right ascension and declination are wrapped with iron sheet or something. It is also a common equatorial instrument, which can not only meet the needs of adjustment in both directions of right ascension and declination, but also is much better than the above two equatorial instruments in structure, precision and stability, and is much heavier. It can be equipped with automatic tracking synchronous motor to achieve automatic right ascension tracking,It is generally compatible with telescopes above the mid-range.
EQ4 level
The widely acclaimed NEQ6 equatorial instrument
On the basis of EQ3, the polar axis horizontal fine adjustment screw is added, and the polar mirror, with a single heel, has no ability to install an automatic star searching system. The polar telescope is added to make it easier to adjust the polar axis parallel to the Earth's rotation axis.It is generally matched with large caliber high-grade products.From this model onwards, more advanced ones are equipped with polar telescopes.It is stronger than EQ3. It is a watershed from toys to instruments.
EQ5 level
It has the ability to install an automatic star seeking system, and can be followed by two axes.Polar axis and latitudinal axis are equipped withSynchronous motor, realizing automatic tracking of two axes.
EQ6 level
Another watershed, with higher accuracy than EQ5, and load.
EQ7 level
It is a EQ2 small change equatorial instrument with higher precision than EQ6.
EQ8 level
Higher precision, huge load
EQ10 level
After mass production, the level of small equatorial instrument will be upgraded to a higher level.
Tracking speed
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Equatorial
The general equatorial instrument motor only uses the star speed to track;Some high-end equatorial instruments will include lunar speed, solar speed and even imperial speed to achieve better tracking effect.Stellar velocity: according toEarth rotation speed(1436.5 minutes a day), which is the standard tracking speed of general equatorial instruments.
Moon speed: track according to the revolution of the moon and the rotation of the earth and the speed of the moon moving in the sky.
Sun speed: track according to the revolution and rotation of the earth and the speed of the sun moving in the sky.
Imperial speed: According to the discovery of an astronomer named King, the tracking speed is introduced by the visual tracking error caused by the earth's atmosphere;Suitable for long time tracking and shootingdeep space 。
Design
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AZ-EQ5 equatorial instrument
The picture shows the German equatorial instrument on display in the public hall of the Taipei Municipal Museum of Astronomical Science Education.According to different needs, there are many designs of equatorial instruments, and each design has its advantages and disadvantages.
British equatorial instrument
The system of the British equatorial instrument is like a cross.Both ends of the right ascension axis (polar axis) are supported by brackets, and the "right ascension axis" is installed near the center.The telescope is mounted on one end of the latitudinal axis, while the other end is equipped with appropriate weights to maintain balance.
German equatorial instrument
The original form of the German equatorial instrument is like a huge T-shaped, with the right ascension axis on a base perpendicular to the ground, and the built-in polar telescope aimed at the celestial pole according to the tilt of the geographical latitude.A bearing is arranged at the junction of the T-shape to make the right ascension shaft connect with the base and rotate.The latitudinal axis is placed vertically near the center of the latitudinal axis.The improved German equator instrument moved the axis of the equator from the position close to the center to the other end of the axis of the equator.
The telescope is fixed on one end of the latitudinal axis, and a counterweight (or other things such as sandbags) of appropriate weight is installed on the other end to maintain balance and prevent damage to the tracking device.The German equatorial instrument is the most commonly used telescope (for observation or astronomical photography) by astronomers. It ranges from a 6 cm (2.4 inch) refractor to a 35 cm (14 inch) Schmidt Kaseglin typeCatadioptric telescopeThese equatorial instruments are mostly used.
Yoke equator
The yoke equator instrument makes the right ascension axis into a frame, and supports it with brackets at both ends. The right ascension axis is installed near the center of the frame.The telescope is completely placed in the frame and covers the latitudinal axis (some do not, such asMount Wilson Observatory2.5 mReflecting telescope）。Unlike the German equatorial instrument, the yoke equatorial instrument does not need additional parts for balancing.
Because the original "yoke equator" telescope is placed in the frame, it is not conducive to observing celestial bodies near the celestial pole.For example,Haier telescopeOfFork equatorial instrumentWe will change the north end into a huge horseshoe shape so that we can observe the celestial bodies near the North Celestial Pole.
work
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Equatorial instruments rarely use electricity as the power source for automatic tracking. Japan has sold winding products.Manual mode, because it allows you to use the rotation of the handle to determine the approximate angle of movement, it is particularly easy to find some dark stars.
hearPolitical UniversityThe reflecting equatorial instrument of the Astronomical Society has also done the work of modifying the manual handle. In terms of the development of the society, it is really unique.Although I don't understand these motors and electronics, I still have some experience to put forward.Some colleagues who use the equator will suddenly find that it can't adjust the rotation speed, so they should first check whether the rotation axis (including polar axis and latitudinal axis) is not locked;In addition, the clearance between gear sets will also have a great impact, mainly in the phenomenon of "delayed action".Some people used to reduce the effect of backlash by reducing the distance between gears. Although such a practice would not affect its average speed, wear, instantaneous maximum and low speed deviation may change, which is a topic worthy of research for high school students.Of course, it is unknown whether the products of these small Japanese factories are really worth our attention.
The positions of axis locks of equatorial instruments are different, some are stationary, and some are mobile. It is very important to find a handy equatorial instrument.If the magnification is more than 70 times, it is a good idea to find someone to help you lock the equatorial instrument, because when you find the target, you may escapeviewHas.The motors of some equatorial instruments are of the same level as VOLVO 960, and there will be a phenomenon of "aftershock" similar to the violent shock. According to the same good practice as familiar with the motors, it is necessary to remake a more sophisticated control box, which not only has digital display, but also rapidly reduces the speed step by step when braking at high speed, just like the ABS of a car.
The phenomenon of "afterstroke" is closely related to the control box and gear setStepping motorHas fewer associations.I don't want to go deep into it. It's good for unprofessional people to know about it anyway, but the equatorial meters that can "recoil" may not be of middle or low level, and some of the high-end products may also be available. It's unknown whether all of them are available. You just need to know well what kind of high speed rotation your equatorial meters will recoil at, and properly avoid such a situation[2]。
function
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The greatest feature of the equatorial instrument is that one of the rotation axes (right ascension axis) is parallel to the earth's rotation axisfixed starWhen the speed of the day rotates from east to west, the influence of the earth's rotation can be offset, so that the image of the target celestial body is fixed in the field of view for easy observation and shooting.The right ascension axis is also calledPolar axis。
Since the equator is used to track stars, the telescope also follows the star sky to "rotate around the target object", and there will be no relative movement (including rotation) between the field of view and the objects in the field of view. When using the theodolite to track, only the target object is fixed, and other stars in the field of view will rotate with the target star, which will affect the shooting;This is also an important function that the equatorial instrument cannot be replaced by the theodolite.
Pushing device
Before the invention of electric power, equatorial instruments were usually operated manually and pushed by mechanical devices such as hydraulic rotating clocks or clockwork rotating clocks.After the invention of electricity, motors were used.Because the sun, the mooncometThey all move relative to the background stars, so the modern equatorial instrument can adjust the motor speed, so that the equatorial instrument can adjust the speed (acceleration or deceleration) to lock these celestial bodies.
Single and double axis electric heel
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Single axis heel features
Electric tracking cannot be used to correct declination drift. At this time, the operator's requirements for precise polar axis will be greatly improved.
Features of dual axis heel
OnPolar axisIf you are slightly biased and misaligned, during the tracking process, ideally,Right ascensionThe offset of is very small (ignoring the periodic error caused by worm shape error, etc.).But in the high power visual guide star ortime exposureIt is easy to find that the star drift south or north.This is the time to useDeclinationThe axis electricity follows to correct.
Difference between the two
Single axis can onlyRight ascensionTracking, for offsettingearth rotation, tracking celestial bodies, declination cannot be adjusted (can be adjusted manuallyDeclination）Because rightPolar axisThere are errors, so you need to fine tune the weft axis from time to time, and you will have a dual axis heel. But if you want to use a dual axis heel, you need to configure itStar guide mirrorThe star guide mirror and the software automatically adjust the right ascension axis and the right latitude axis, so as to achieve the goal of tracking objects for a long time without error.The popular point is that the single axis can only track horizontally, and the vertical axis must be manually adjusted. The double axis plus star guide mirror can automatically track horizontally and vertically.
use
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instrument
The simplest way to track the celestial bodies moving due to the diurnal movement is to use the equatorial ritual platform, which is much more convenient than the theodolite.As long as you understand the essentials of use, visual observation or photography will produce good results.The night sky revolves once a day around the axis of rotation that connects the northern and southern celestial poles, which is called the diurnal movement.
On the platform of the equatorial instrument, extend the polar axis (or the right ascension axis) to the north celestial pole (to the south celestial pole in the southern hemisphere), and you can simply track the movement of stars.In other words, make the polar axis of the equatorial instrument parallel to the earth's axis. This operation is called polar axis adjustment. When using the equatorial instrument, never forget to align it with the polar axis in advance.
The platform of the equatorial instrument can be divided into two types: those with right ascension and right latitude micro levers, and those with polar axis motor tracking.It is more convenient to track stars with inching rod than that of theodolite, but it must be continuously manually to continue tracking. If the budget permits, it is better to use motor tracking type, which will be much more convenient.The balance of the equatorial axis and polar axis must be adjusted.If the balance state is well adjusted, the mirror cylinder will stop when the fixing screws are loosened, and the equatorial instrument will run smoothly and smoothly.
In recent years, manufacturers have added the GOTO function to advanced equatorial instruments, so users can instruct the telescope to automatically point to the observation target.However, it consumes a lot of electricity, so you need to carry large batteries when watching stars in the wild.
There are many kinds of equatorial instruments.There are two kinds of equatorial instruments most commonly used by amateur astronomers: German and fork equatorial instruments.The German equatorial instrument is suitable for refracting, reflecting and catadioptric telescopes.The fork type equatorial instrument is generally used with the catadioptric telescope.The advantage of the fork type equatorial instrument over the German type is that it does not need a counterweight, reduces the weight of the instrument, and is convenient for field stargazing.However, the stability of the amateur series fork equatorial instrument is not as good as that of the German equatorial instrument.The equatorial instrument used by the Boguan series telescopes is a German type equatorial instrument.
Celestial objects visible to the naked eye can be aligned with a star finder, and the equatorial instrument is used for fine tuning and tracking.Deep space objects can only be found by using the time angle and declination of the equatorial instrument.
The equatorial instrument has three axes:
1. Horizon axis.It is perpendicular to the ground plane, the lower end is connected to the tripod platform, and the upper end is connected to the polar axis, with a horizontal height dial.Rotate around the horizon axis to adjust the horizon azimuth of the telescope.
2. Polar shaft.One end is connected with the horizon axis. Pull the polar axis up and down to adjust the horizon height angle.The other end is connected with the latitudinal axis at an angle of 90o, and is equipped with an angle disc for adjusting the hour angle (right ascension) pointed by the telescope.
3. Bare weft shaft.It is connected to the polar axis at 90o, and the upper end is connected to the main mirror cylinder at 90o to ensure that the mirror cylinder is parallel to the polar axis.The lower end is connected with the counterweight, which is equipped with a declination disk for declination adjustment pointed by the telescope[3]。
Alignment observation
Step 1: Polar axis adjustment.Make the polar axis of the telescope parallel to the earth's rotation axis and point to the north celestial pole.
1. Connect the main mirror with the equator and tripod, and place the leg marked with "N" in the north.Adjust the height of the tripod to make the tripod table level.2. Loosen the fastening screw of the polar axis (right ascension axis) and rotate the primary mirror to the left or right.Loosen the fastening screw of the counterweight and move the counterweight to balance the telescope and the hammer.Turn the telescope back to the top and tighten the screws.
2. Loosen the horizontal tightening screw, turn the equator to make the polar axis (telescope) point to the north (compass orientation), and tighten the screw.
3. Loosen the fastening screw connecting the polar axis and the horizontal axis, pull the polar axis up and down to align the pointer with the geographical latitude of the observation site (for example, the geographical latitude of Jinan is+36.6o, that is, north latitude+36.6o), and tighten the screw.
4. Loosen the fastening screw of the latitudinal axis, rotate the telescope to make it parallel to the polar axis (that is, parallel to the local warp coil), and tighten the screw.
5. Observe whether Polaris is in the center of the field of view from the telescope (or the star finder with the optical axis adjusted). If there is any deviation, fine adjustment shall be made to the horizontal azimuth and horizontal altitude of the polar axis until Polaris no longer moves in the center of the field of view.
6. Turn the hour angle dial to align the pointer at zero hour (0h);Turn the declination dial to align the 90o pointer (some have been fixed 90o or 0o when leaving the factory).At this point, your telescope is completely parallel to the earth's rotation axis and the meridian plane of the observation point.As the earth rotates, the telescope is always facing the Polaris.Special note: After the polar axis is adjusted, the tripod, polar axis azimuth angle and height angle cannot move at all, otherwise it needs to be readjusted.The North Celestial Pole does not coincide with Polaris completely, but deviates 1 o toward Beta Minor.
Step 2: Calculate theLocal sidereal time。Example: Calculate Jinan local star time at 19:00 Beijing time on May 1, 2002.1. From the astronomical almanac of that year (published annually by the Beijing Astronomical Museum), it is found that the local star time at 0h GMT on May 1, 2002 is 14h35m00s.
2. From relevant data, it is found that the geographic longitude of Jinan (observation point) is 117o east longitude, and the time angle is 7h48m00s (15o=1h, 1o=4m, 1 '=4s).
3. Use the following formula to calculate s=So+(mBei-8h+λ)+(mBei-8h) * 0.002738 local star time, the time angle of the vernal equinox γ measured at the observation point So Universal Time 0h Greenwich local star time m North Beijing local peacetime λ The geographical longitude (time angle) of the observation point 8h Beijing time is the eastern eighth time zone standard 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. Since the result is more than 24h, 24h should be converted into a day and 24h should be subtracted.S=43h25m13s-24h=19h25m13s Answer: Jinan local star time at 19h00m00s Beijing time on May 1, 2002 was 09h24m48s on May 2.
Step 3: calculate the time angle (t) of the observed celestial body at the observation time.t: Starting from the local meridian circle, the whole circumference is divided into 24 hours (15o per hour) from east to west.Example: m65 in Leo（Extragalactic galaxy）。
1. It is found that the coordinates of the celestial body on the celestial sphere are: right ascension α=11h18m00s;Declination δ=13o13 '.Right ascension α: the longitude of the celestial body on the celestial sphere, taking the longitude and latitude passing through the vernal equinox point γ as 0, and dividing the circumference into 24 hours from west to east.Declination δ: the latitude of the celestial body on the celestial sphere, which is 0o based on the celestial equator, and is positive to the north and negative to the south, with each score of 90o.
2. Use the formula to calculate t=s - α t=09h24m48s-11h18m00s=- 1h53m12s
Step 4: operate the telescope to aim at the celestial body.
1. Loosen the fastening screw of the latitudinal axis, rotate the main mirror, first align it with the celestial equator (the latitudinal disk 0o), then rotate δ=13o13 'northward, align it with the pointer of the latitudinal disk, and tighten the screw.
2. Loosen the tightening screw of the polar axis, rotate the telescope around the polar axis east (the time angle t is negative), align the time angle of m65 - 1h53m12s with the angle dial pointer, and tighten the screw.
3. First observe m65 with a low power mirror. 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.As the earth rotates, the target will gradually move out of the field of view, so it is necessary to keep tracking with the micro adjustment handwheel.If it is an automatic equatorial tracking instrument, turn on the switch.
Special note: when observing the object the next day, the time angle of the object will increase by 3m56s to - 1h49m16s due to the earth's revolution.
effect
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The function of the equatorial instrument is relative toTheodoliteFor example, although we should have known it, there is one thing that deserves our common understanding, that is, it is a kind of gantry that is "more convenient to track" than the theodolite, and only needs to turn one axis.However, such convenient tracking will cost a considerable amount. At the same time, the more requirements, the greater the cost will be.As for the German equatorial instrument, which has accompanied many older Taiwanese colleagues to spend most of their lives since the Japanese occupation, it is troublesome enough that it can't use the heavy hammer to see the stars;Even so, the fork equatorial instrument has no such problem, but it is still not favored by most of Taiwan's colleagues. It really needs to be made clear.
Although the dead angle of the fork equatorial instrument in the south and north pole of the celestial sphere is worth mentioning, at least it does not affect the operation of the equatorial instrument. If the German equatorial instrument rotates, it will get stuck on the mirror frame, which is more fatal.Therefore, it seems not a good argument to use the "dead angle" theory to avoid the use of the forked equator.It's funny to say that, in fact, my guess is that this phenomenon is mainly caused by the "polar axis".Before the return of Halley's Comet, the number of peers was very small, and there was not much astronomical photography. In the eyes of these peers, the polar axis of the "dial method" was quite accurate.
Since the introduction of Takahashi's P-type equatorial instrument, it is expected to become the equipment of German equatorial instrument year by year. Even the fork equatorial instrument cannot be dispensed with such optional accessories.Several years after Taiwan's early P-2, TS-90, MARK-X equatorial instruments entered Taiwan,Halley's CometIn return, some people will know the polar axis correction method such as "dial method". Even if they want to do it intentionally, they may not find the required scale on the equator. Anyway, it is not very accurate.
When it comes to polar axis alignment, it is necessary for photographers to know that "polar axis alignment". The reason why German equatorial instruments are easy to align polar axis is that they are easy to install polar axis inside, and that they can allow a longer polar axis is also one of the reasons. In contrast, the commercially available fork equatorial instruments need to be installed outside, which increases the possible error,Its polar axis is very short, which is also the difficulty of mechanical structure[4]。
