For all amateurs of astronomy but especially for those who are just entering amateur astronomy, or if they have given you a telescope and you have no idea how it works, today we will explain how to use a telescope, always talking about non-professional astronomical telescopes. use of amateurs
The first thing to do if the telescope is new is to assemble it. For that, you have to follow the instructions that are different depending on the model, once assembled in the correct way we identify three controls:
- Star finder: Used to search for objects in the sky. The first exercise in learning how to use a telescope is to align the search engine, and you should always check its alignment before starting an observation.
- Eyepiece: It is where the eye is placed to observe, depending on the diameter of the eyepiece, we can have a greater or lesser enlargement. The eyepiece fits on the eyepiece and may have other accessories depending on the quality of the telescope.
- Focus: In observation, it is essential to adjust the center once the objective has been focused. Moving the focus knob seeks to improve the sharpness of the image as best as possible.
Now that we know the parts of the telescope and how to handle them, we must find a place to start observing the sky. It is always better to look for a home away from the lights of the city, but if this is not possible, we should find a high place – perhaps the roof, terrace, or balcony – to avoid the reflection of lights that will diminish the power of the telescope.
Once mounted on the tripod and well located where we will do the observation, we look for an object with the star finder moving the telescope and without moving the tripod. Once we have centered the objective, we remove the protective cap of the main tube, observe through the eyepiece and focus.
How to adjust your telescope with the method …
Participating for several years in astronomy forums, I found that among the issues that come up most often, there is that of the setting of optics, the famous “collimation.” Beginners are often drowned in the information (several methods exist), and we forget all too often to talk to them about the overall process. To set an instrument is not to place a laser in the eyepiece holder and turn the screws until the small red spot is centered. This is just a step after some essential preliminaries. I propose to talk about the overall process: check, adjust.
Warning: There are a lot of methods. What matters is not to adopt the technique but to understand it. I am not looking here for the hyper-sharp alignment of planetary imaging specialists since I am primarily speaking to beginners. I guess the telescope is Newton-type (the glasses are rarely adjusted, for other optical combinations can be adapted …)
Last thing: what takes 185 sentences to explain often takes 3 seconds to do (I barely exaggerate).
1 / The basic rules
These rules are to be known by the heart. A written interrogation will take place at an indefinite date. Any score below 10/20 will result in the confiscation of the instrument! (In short, these are fundamental rules).
R1 – To set a telescope, it is to realize two things: 1 ° to correctly place the optical elements, 2 ° to align the visual elements.
Do not try to align the optical elements if they are not placed correctly!
R2 – It is forbidden to adjust the optical elements if they already are; in other words: we check first, then change.
Do not start by collimating your telescope: it was perhaps already, you will disrupt everything!
To check is like thinking: only the drunkards act before thinking. And here is not the paragraph “set the telescope like nags” …
That said, if you master the process, you have every interest in tweaking. But you were always checking first.
R3 – If the image is blurry, it is not necessarily a problem of alignment.
It’s not because a dozen unimaginative Internet users push you to redo the alignment that they are right. If the image is blurry, it can come from a multitude of reasons. We must first find the cause (think, check) and then only rectify (act). So check the alignment (among others).
R666 – There are several methods for aligning optics. There is only one method to check alignment: on a star.
This is the most important rule.
We do not check the alignment with a laser; for example, it’s not made for that; it’s done to align optics when they are in place.
2 / The three acts of complete adjustment
Act 1: we check the placement of the optical elements.
-> It’s essential the day you receive your telescope.
Or? Warm, at home, by day. If there ever was a shock during the transport, if we have a telescope completely removable, if we have a doubt or if we checked everything and the image remains unclear, we can, of course, check it on the ground. But usually, it’s not helpful if you did it before you left.
When? Rarely. Usually, once it is well positioned, it does not move too much. But if you have a doubt, do not hesitate.
How? Looking at the telescope.
Warning: it is forbidden to skip act 1. If you proceed to the alignment of your optics without having checked their placement, do not be surprised to galore … If the images are blurred, start by looking first if the optics are well placed, it is useless to make a sharp check while the problem may jump in the eyes if you look at the telescope.
(Remember the Chinese proverb: when the nag shows the fuzzy star, the exact first looks at his telescope.)
Act 2: we check the alignment of the optics.
Or? Cold, on the ground, at night. Preferably after letting the telescope warm up.
When? At each observation session.
How? Pointing a star.
If the optical elements are well placed, we can check with a laser. But if there is a problem, it is forbidden (because the problem can come from the laser, or a lousy manipulation of it …), it must be done on a star (v. R666).
Act 3: If necessary, we realign the optics.
“If necessary” depends on the observer. An experienced observer may be more demanding; a planetary imaging specialist will always re-align. It also depends on the turbulence: if the sky is stable, we can achieve an exact alignment, useless if the sky is turbulent …
Or? Cold, on the ground, at night. (No need to align your telescope at home with a crazy precision if it is then to carry it in your car and cross speed bumps …)
How? There are several methods.
But let’s detail all that …
3 / Act 1: we verify the placement of optics
From time to time, especially the first time, do the necessary checks (I always assume that we are dealing with a Newton):
– Is there a primary mirror? Is it placed at the bottom of the telescope more or less flat? Is it in good condition?
– Is there a secondary mirror? Is it attached to the spider’s support, pointing to the hole in the eyepiece holder? If we look in the empty eyepiece, do we see the secondary? Is it in good condition?
– Did you find the eyepieces, do you know how they are used? (This is to check that the observer is well adjusted …)
Well, now we will check that the optical elements are placed opposite each other. It’s sort of a rough alignment. If we do not do this, we will be too far from the precise adjustment to be able to use the methods of Act 3 effectively.
3.1 The spider
Logically, the support of the spider is centered concerning the tube. The secondary mirror is stuck on this support. If the F / D of the telescope is weak, it may be glued off-center, it is then normal (and calculated). But the support is usually centered.
Check it by measuring the branches of the spider, or comparing their length with a compass. Usually, this setting is made at the factory and does not move. If there is an offset of a few millimeters, do not change anything: this setting is not critical. It is only if there is a noticeable delay that the support of the spider must be replaced. But it would be weird … (you have a simple Newton, huh?)
3.2 The eyepiece holder
The eyepiece holder should be perpendicular to the tube. Check it approximately. If this is not the case (it can happen, for example, if there is a bump on the machine), replace it perpendicularly with its adjustment screws. If it is 89.9 ° instead of 90 °, it does not matter, for now, we just check that there is not a big problem.
3.3 The secondary mirror
Take a look at the empty eyepiece holder (no Barlow, eyepieces, etc.) Usually, the secondary mirror should be visible in front of the eyepiece holder, not to the side, and should point roughly to the eyepiece.
Two adjustments are to check (and possibly redo): translation and rotation. In the following drawings, the telescope points to the left. Only the eyepiece holder and the secondary mirror seen in it have been shown.
Place the tube horizontally. (Attention: any other position entails, in case of manipulation, the possible risk that the secondary falls to the bottom of the tube, to his chagrin and the great damnation of the primary over the market …)
One warning: Never look at the Sun through the telescope without the proper filters; it can seriously damage your eyes.