The Swedish FLT

The Swedish Fairly Large Telescope at the Österlen Observatory.

Österlen Observatory is equipped to carry out a wide range of differing types of astronomy from solar observation, monitoring sun spots and prominence activity, to observing the Moon and planets of our solar system. The observatory is also equipped to explore beyond the solar system with powerful deep sky CCD imaging cameras – exciting targets include the every growing list of stars found to have planets (or exo-planets as they are more properly called) and looking at nebulae and supernova remnants within our galaxy and galaxies far beyond the Milky Way.  Keep an eye on Österlen Observatory for new observations and updates and our What’s in the sky this month videos.

The main telescope is a Meade 14” RCX-400, this is an integral fork mounted system and is installed on a British made Astro-Engineering AC282 anti-vibration pier with AC421 pier top and equatorially mounted on an AC400 MegaWedge.

Österlens Astronomiska Observatoriums största och mest sofistikerade teleskop

Meade RCX-400 är det huvudsakliga teleskopet vid Österlens Astronomiska Observatorium

Ritchey-Chrétien optical system

The manufacturer designated the optical system of this telescope a Ritchey-Chrétien design (see picture below). However a subsequent legal battle saw Meade forced to withdraw the use of this designation and indeed, in time, they cancelled the product completely. A triumph for correct nomenclature and the names police? Not really. This is about one set of commercial interests being stopped from using a name that another group of commercial interests had already hijacked.  But a couple of firms of US lawyers both probably drew a good fee from it despite the lack of public good. Some members of the design team at Meade still maintain, in their beer anyway, that the design deserves to be called Ritchey-Chrétien. Messers M. Ritchey and M. Chrétien are not available for comment as they are both spending some time dead for tax purposes.

But it says Ritchey-Chrétien on the tin?

Features of the RCX-400 design. In a way similar to Schmidt-Cassegrain designs, the RCX’s corrector plate supports the secondary mirror and corrects for optical defects. However, although the RC optical system developed by Georges Willis Ritchey and Henri Chrétien reduces much of the coma, in doing so it introduces a measure of astigmatism. Meade engineers re-designed the corrector plate and minimised the residual astigmatism and eliminated the need for the secondary mirror supports. According to Meade, the image contrast and resolution are now noticeably greater than the received RC design. The use of UHTC coatings further contribute to the production of images with maximum brightness and contrast. This Meade Ritchey-Chrétien based technology is optimised for CCD imaging to obtain sharp star images over the whole of the sensor field.

Pontus Österlin observing the planet Venus in daylight

Electronic features. Meade have developed a range of innovative electronic and mechanical features to go with this advance in commercial telescope technology. The optical collimation is electronically controlled using the Autostar controller making it possible for one individual to make the adjustments and see the results of those adjustments instantly at the eyepiece. The relationship between secondary and the primary mirror is set at the factory using an optical laser system. This factory base position of the secondary mirror is permanently stored in the controller memory, allowing it to be recovered in case of collimation adjustment error. The primary mirror remains fixed in the original laser aligned position set up at the Meade factory in Irvine (USA).

Astronomiska Teleskop Observatorium

Inside Österlens Astronomiska Observatorium

An important difference between the RCX-400 and other popular catadioptric systems (both their own and competitor products)  is that the primary mirror is fixed and focusing is achieved by moving the combined secondary-corrector assembly.  The primary mirror rests on a buffered adhesive layer contrived to subject the mirror to the minimum mechanical distortion.

Built in resistance heaters and cooling fan. To combat dewing the RCX has a ni-chrome wire heating element around the corrector. The element is mounted on to the glass to make sure that the heat is applied to where it is needed rather than heating up the tube and cell (as with conventional wrap-around after-market systems)  this thermal efficiency minimises risk of thermal disturbance within the tube and conserves energy.  The anti dewing control system utilises two temperature sensors, one on the corrector and the other situated on the body of the scope for an ambient reading. The system can be set to energise the heater at a specific ambient trigger point and maintain dew free optics for the minimum heat input. To reduce cool-down time a fan is fitted to the rear cell and is controlled via the hand set.

High precision shift-free focus system: Another important RCX400 innovation is the enclosed electronic focus system. The primary mirror remains fixed and the combined secondary mirror and corrector plate moves. This focusing operation is carried out electronically to a precision of one hundredth of a millimetre. The position of the front section is displayed numerically on the Autostar hand controller and nine positions can be stored in memory. This function is very useful when using different optical configurations either with eyepieces or cameras.


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