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Jan Ströher

Jan Ströher

Posts composed by Jan Ströher

NBX – the new dual nebula filter from IDAS

October 19 2020, Jan Ströher

A new, high quality dual band filter has appeared on the market, in the form of the NBX nebula filter from Japanese company, IDAS.  It is especially efficient for nebula photography using fast optics, like the Celestron RASA, for example. Like the existing IDAS (Astro Hutech) nebula filters, the new NBX is of impeccable quality and workmanship.

The IGAD (Ion-Gun Assist Deposition) coating technology which has been specially applied to astronomical filters by the Japanese manufacturer, Astro Hutech, was originally developed for optical communication, where long-term stability (> 25 years) is required in rough field conditions.

IDAS NBX 48mm nebula filter

This leads to filters with robust coatings and durable spectral stability – even at extreme temperatures and humidity levels. This stability is especially important for bandpass curves with steep sides, such as H-alpha, LPS filters and other narrow band filters. Filters with IGAD coatings almost completely eliminate bandpass shifts of +/- 3 or 4nm, which are typical with standard filters.

The NBX is a dual filter which specifically focuses on OIII and H-alpha lines. The NBX‘s transmission curves in the H-alpha and OIII ranges are very clearly illustrated in these two figures:

Transmission curves in H-alpha


Transmission curves in OIII


You can see that the IDAS NBX filter primarily realises its full potential when used with very fast optical systems and astrographs, such as a Celestron RASA, especially fast Newtonian reflectors with f-numbers between f/2 and f/4 and special devices, such as the Officina Stellare Veloce RH 200 Mark II-AT (Riccardi-Honders).

The NGC 281 “Pacman” Nebula in the constellation Cassiopeia

This dramatically increases the contrast within emission nebulae, which predominantly consist of oxygen (OIII) or hydrogen compounds (H-alpha). Additionally, longer exposure times are no longer required, predominantly due to the use of the above-mentioned, extremely fast optics, but also due to the NBX filter’s special contrast effects. The filter is ideal for use with ‘one shot’ colour cameras and monochromatic CMOS cameras. An IR blocking filter is then no longer required. Additionally, the NBX is parfocal with other IDAS LPS nebula filters.

CEM70 with iGuider – the latest innovation from iOptron

September 23 2020, Jan Ströher

The American company iOptron, which has already built a good reputation for itself in recent years with innovative, efficient and quiet mounts, launched a worthy successor to the popular CEM60 in April this year: the CEM70.

The new CEM70 comes with the characteristic appearance of the proven CEM mounts. CEM stands for centre-balanced equatorial mount. This design allows a particularlyfavourable ratio of load capacity to actual mount weight. In the case of the CEM70, the ratio is 2.3. This means that the mount carries more than twice its own weight! So, the CEM70 is still suitable for mobile applications, but is also a very good mount for observatories.

The stepper motors and the toothed belt drive allow high pointing accuracy in GoTo operation, but most importantly, a very precise tracking accuracy with a periodic error of less than +/- 3.5 arc seconds. All this with the usual welcome quiet operation of all iOptron mounts.

Just like the CEM25P or the CEM60, the new model is perfectly suited for astrophotography. The highlight is a version which comes with iGuider, an integrated autoguider! In addition, both versions of the CEM70 have an ST4 interface, built-in GPS, a sturdy transport case, quiet stepper motors, the proven Go2Nova hand controller, as well as a dual mount saddle for Vixen and Losmandy dovetail plates.

With a maximum load capacity of 31kg, the CEM70 offers great flexibility for different telescopes and the appropriate photographic equipment. All in all, the new CEM70 is an even more portable mount with a wellthought-out design, useful functions and additional features, which also carries a higher instrument load even more safely, tracks quietly and precisely, and thus will never let you down during astrophotography! Both model versions can be found from us here at Astroshop.

Good conditions for observing Venus

January 20 2020, Jan Ströher

In the coming weeks Venus, our “sister planet”, will become a good object for observing. The planet is a bright, easily detectable object in the morning or evening sky, but it is usually located very close to the horizon with corresponding atmospheric disturbance and rather short observing times. This will improve from around the end of January, when Venus will become progressively brighter and visible for longer in the evening sky. Then the planet will be found easily with the naked eye immediately after sunset and can be observed for almost four hours.

Even good binoculars, such as the Omegon Nightstar are suitable for observing. In telescopes with an aperture from around 90mm, Venus can already be identified as a small disc. Just like the Moon, the planet exhibits different phases, although details of the surface remain hidden owing to its very dense atmosphere. The cloud structures can be distinguished very well with telescopes from 130mm aperture. The use of a suitable filter (violet, dark blue, blue) is recommended to improve the contrast.

Credit: EXAME/JAXA/Divulgao, Brazil

Venus is the second innermost planet in our solar system and is a similar size to Earth. Its atmosphere consists of carbon dioxide, nitrogen, sulphur dioxide and various noble gases. This composition, combined with its proximity to the Sun, makes our neighbouring planet a hostile and mysterious world. As it orbits the Sun, Venus rotates backwards, that is in exactly the opposite direction to our Earth. Therefore on Venus the Sun rises in the west and sets in the east. After the Moon, the planet is the brightest object, but, just like Mercury it is only visible in the morning or evening sky – hence it is also given the designation “morning-” or “evening star”.

From mid-January, Venus dominates our evening sky immediately after sunset on the southwestern horizon. Between then and the end of March it changes its position from about 25° to 46° and reaches a brightness of -4.7mag by the end of April. During this period it moves towards the western horizon and passes through the constellations Aquarius, Pisces and Aries. In April it reaches Taurus and can even be found close to the Pleiades (M45) at the beginning of April.

From January to May it’s best to track Venus using a star chart.

Credit: Planetarium Bochum

Have fun observing Venus in 2020!

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