Selection of star guide mirror

In fact, you don't need a star guide mirror with too long focal length, especially if you use an automatic star guide. If the magnification is too large, your automatic star guide will track the errors of sight, wind and equatorial plane. Therefore, a short tube of 8 cm or wo66 is a good star guide. The long cylinder version is a bit too much. The same hobby is to use the Maksutov lens of C90+defocus lens, and he also got a good star guiding effect.

The old rule of thumb is that when shooting with bottom shot, the star guide mirror should at least reach 1/2 of the main mirror system, and when guiding the star manually, you need it to be equal to or better than your main mirror system. You also don't want the error of the guiding star to be higher than the width of the guiding star, so as to avoid the star dragging the line. However, when CCD was popularized in amateur astronomy, this rule disappeared as quickly as a negative film.

Most tourists in astrophotography will buy a star guide mirror with twice the focal length of the main mirror. The ability to shoot different focal lengths and image measurements will give you great versatility, which means that you can customize your itinerary for two situations and/or celestial bodies. Therefore, it is usually recommended to buy a high-quality, short-focus apo as a star guide. It can also be used to shoot large objects such as m3 1 and Galaxy, or it can also be used when the night wind has a great influence on telephoto images.

However, there is also a phenomenon: if a good equatorial telescope is used, even a small star guide mirror like pecial borg can successfully guide the stars, so remember: the first thing to guide the stars is that the essence of the equatorial telescope is good, and almost any guidance is accurate.

However, there is no need to be discouraged without a good equatorial telescope! It is good to know more about how to adjust the parameters of equatorial plane and guide star. According to the above article, if the economy does not allow it, just buy a guide star with a short focal length of 8 cm, and a guide star with a large caliber is easy to find, so there is no need to make coarse adjustments and fine adjustments.

Moreover, the erection of the star guide mirror is still the most stable with double rings! But it is also a difficult way to adjust. However, it's not too difficult to adjust, that is, sometimes you need to hold the lens barrel by hand and practice more, and you will find it very useful.

When using micro motion pan/tilt, especially when using springs, please note that the spring bracket will be slightly displaced. Over time, it is necessary to check whether you have relaxed.

Mainly depends on the jump value of the guide star. Usually, no matter what focal length is used, it is best to keep it steady without correction, which depends on the personal alignment of the polar axis, the adjustment of balance, the adjustment of the meshing between the motor and the gear, and what I found before: it is really bad to put some lubricating oil between the gears! There is less noise when guiding the stars, which is smoother. It may be that its viscosity counteracts some vibration, and the friction between gear metals is smoother!