Skywatcher Skymax-90 on EQ1 - 90/1250 mm Maksutov Cassegrain

Skywatcher Skymax-90 on EQ1 - 90/1250 mm Maksutov-Cassegrain

The compact Maksutov with 90 mm aperture is suitable for almost all applications in hobby astronomy and also in nature observation. Being only 25 cm long, it fits into any air luggage and with its low weight the Maksutov can be carried by compact mounts or even good photo tripods.

Hardware

The telescope optics: The highly portable Skymax-90 EQ1 is ideal for the observation of double-stars, and the surface detail of the Moon and bright planets. Despite its small dimensions, it packs a powerful punch. Its high-resolution, long focal length optical system is multi-coated to maximise contrast and image sharpness. Even collimation (adjustment of the optics) is possible, but rarely necessary.

The telescope mount: Skywatcher´s smallest equatorial mount already corresponds to the larger models. You can adjust and track the object in the telescope by using the flexible shafts. For fast movement you can release the clamps on the axes.

A special feature of this mount is that you can also use it like an altazimuth mount and so you can easily use it on terrestrial objects.

As an optional accessory, a motor drive for the right ascension axis is also available for this telescope mount - helpful to keep the objects in the field of view.

Usage

Observation: No matter if you observe animals in the wild or the stars in the sky, the BKM 90 will convince in all areas. 90 mm aperture collect enough light for many hundreds of nebulae and galaxies, but the true strength lies in the observation of objects in the solar system. The image has no colour fringing and therefore there is enough contrast to view the moon and planets with high sharpness. Under ideal conditions you can magnify up to nearly 200x.

With the optional 8-24 mm zoom eyepiece you can completely cover the magnification range useful for observing the moon with this telescope. At 24 mm the natural earth satellite does not completely fill the field of view, but to a pleasantly large extent, while 8 mm is close to the instrument´s calculated maximum magnification. Of course, you can also use other types of eyepieces, like Plössl or Planetary HR.

An objective solar filter combined with the 25 mm eyepiece results in a safe solar telescope with a very pleasant view, while the zoom eyepiece mentioned above allows a maximum magnification adapted to the air turbulence. Here, too, the object of observation fits completely into the eyepiece set to 24 mm, while small sunspots can be observed at 8 mm eyepiece focal length.

For earth observations a 45° Amici prism is recommended, because then the object can be seen in natural orientation. This gives you a spotting scope with high possible magnification. Please note, however, that you also magnify the air turbulence, which has an increasingly distracting effect, especially at greater distances.

Photography: The BKM 90 has a direct T2 connection thread. This allows you to mount your SLR camera easily via a matching T2 ring. Also the connection of mirrorless system cameras is possible without any problems. The Skymax is comparable to a high-quality telephoto lens with a focal length of 1250 mm and a focal ratio of f/13.9. Note: Vignetting will definitely occur with full-frame and APS-H sensors because the illuminated area is too small.

Light astro cameras with 1.25" connector, for example the items TSSSI (linked under accessories) or TSTCD300, can be plugged directly into the eyepiece holder. Create planetary videos or stack the single frames to get sharp planetary images. Of course, lunar craters are also a worthwhile target.

Special suitability as an entry-level or travel telescope

A good entry-level/travel telescope must

be easy to use without any particular technical experience (please follow the instructions anyway)

very versatile, i.e. useful for any type of astronomical observation

be easily expandable, especially with motorized tracking - useful for photography

be light and compact for traveling by plane or train

The Maksutov on the EQ1 meets all these requirements. The whole unit is very light, weighing less than 10 kg, and very compact. These are the ideal conditions for a life-long "friendship".

The mount EQ1 carries the only 1.4 kg light tube with decent stability, even slight wind or focusing does not cause any disturbing vibrations.

Setting up the telescope with mount from the individual components only takes about a quarter of an hour, even with the optional motorization, so you can start observing quickly and still enjoy the convenience of electric tracking. You observe more often, therefore: ?The best telescope is the one that is used the most.?

Practical and background information from Teleskop-Service - the Maksutov-Cassegrain system

A Maksutov-Cassegrain offers an image quality that is very close to that of a classical refractor, but with a very short construction. The image is clearly better than that of fast achromatic refractors with the same aperture, because a Maksutov-Cassegrain has no disturbing chromatic aberration.


The Maksutov-Cassegrain is therefore an interesting alternative for amateur astronomers who value a sharp and high-contrast image while using a compact instrument.

However, a Maksutov-Cassegrain is relatively slow, the focal length is relatively high in relation to the aperture. Therefore a Maksutov is a very good instrument for observing the moon and planets. It is also a good performer for stellar clusters, nebulae and galaxies but it does not offer a particular large field of view. Very extended objects as the Pleyades cannot be seen all at once.

The optical system (see image): Light enters the system through the front end meniscus lens before hitting the spherical primary mirror. The latter collects it and reflects it to the front again, this time to the secondary mirror.

The secondary mirror reflects the light back through a hole in the middle of the primary mirror while extending the focal length.

Right behind the hole of the primary mirror there is a holder for an eyepiece, a star diagonal mirror or an Amici prism. Here you can observe, but you can also attach a camera via an adapter and thus take pictures.

The remaining error caused by the spherical shape of the two mirrors is corrected by the front meniscus lens. This results in a well corrected image on the axis and in the field. A further advantage is that the front end lens seals the tube. A sealed tube is less sensitive for temperature changes.

Focusing: Focusing is achieved by moving the primary mirror using a micrometric screw. This type of focusing has strong advantages, as a standard focuser is not necessary and the focusing range is very large. Nearly every imaginable part of equipment will get into focus with this Maksutov-Cassegrain.

The biggest disadvantage of the primary mirror focusing is mirror shifting, the disturbing wandering of the image when focusing, especially in photography. This problem, caused by the tilting of the mirror, practically does not occur with the Skymax-90!

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