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The Takahashi TSA-102 refractor has became the worthy heiress of the mythical FS-102. The apochromatic objective of 102mm of aperture (F/8) forsook its classical optical design with Fluorite doublet for a ED triplet set in a simple barrel, whose results are quite as flattering. The TSA-102 remains the most general-purpose telescope of the Takahashi range, adapted not only for planetary high-resolution observation but also for deep sky imaging, while still being easily transportable.

As usual with Takahashi, the TSA-102 profits by a very vast range of accessories, adapted to all amateur uses. Moreover, many amateurs have made the proof of its versability in fields as varied as planetary observation or deep sky imaging.

The TSA-102 is available in two versions, offering the same optical and mechanical characteristics. The S version has a retractable dew shield, making it possible to gain in volume, while the N version is equipped with a fixed dew shield.

Optical specifications

Mecanical specifications

Longitudinal view (lengths in mm)

Optics

The TSA-102 is equipped with an apochromatic objective with ED triplet of 102mm of aperture (F=816mm, F/8), set in a simple barrel. This barrel ensures a good stability of the opto-mechanics chain against the usual constraints of transport and against the important variations of temperature of use. The TSA-102N is proposed with a fixed dew shield while the TSA-102S has a retractable dew shield.

Mechanics

The short tube of the TSA-102 (717mm without the delivered extension tube) facilitates its transport. It allows also the use of many kind of accessory assemblies, especially for those using important length (230mm of backfocus, see the Specifications section). The assemblies of screwed accessories, recommanded by Takahashi, are still possible (see System-charts section). However, the standard 50.8mm adapter universalizes the TSA-102 without option, even if the use of the optional camera angle adjuster (CAA) is highly recommended.

Accessories

The reading of the system-charts gives a good idea of the sphere of activities of the TSA-102. The addition of the optional field corrector allows imaging at prime focus with the F/8 default focal ratio. The TOA-RD reducer (F/6) gives to it more ease in wide field astrophotography. All the assemblies fulfill the requirements of rigidity and flexibility needed by the new imaging devices, such as the SLR/DSLR or CCD cameras.

Optical design and TSA-102/FS-102 compared chromatic correction

Optical design and TSA-102/FS-102 compared chromatic correction
Takahashi has developed an air-spaced ED triplet objective (3 lenses in 3 groups). This triplet consists of a lens of ED glass (S-FPL53) laid out between 2 crown lenses air-spaced by a mean chock. Alike the TOA objective, optics have been designed and calculated according to the high requirements of the current numerical imaging.
The change of optical design between FS-102 and TSA-102 has no spoiled the chromatic correction, on the contrary. This new ED design shows its full effectiveness, including in the intransigeant planetary imaging use.

Spot diagrams
The spot-diagrams give a good idea of the results obtained on the image circle, whether it is at prime focus or behind optical accessories. The 35-FL field corrector shows all its effectiveness in wide field imaging with DSLR cameras, for example.