Intermediate instrument between the TSA-102, of which it takes again the main features, and the TOA-130, TSA-120 refractor replaces the famous FS-128. The TSA-120 is characterized by its simplicity, its versatility and his exceptional quality/price ratio.
TSA-120 features the specifications of the TSA-102S: an apochromatic objective with triplet ED, a retractable dew-shield, great mechanics and versatility of use, both visual and photographic. Moreover, TSA-120 is extremely light, it weights only 6.7 kg. Even when TSA-120 is fully equipped for CCD imaging, EM-200 will easily holds it. No extra heavy mounts will be required.
This refractor can be equipped with the same optical accessories as the TSA-102, including the focal reducer TOA-RD #18, the field corrector TOA-FL35 and ED 1.5x and TOA 1.6x extenders. The specific system-charts will help you to specify the necessary configurations.
| Spec. | TSA-120 |
|---|
| Optical design | Triplet Super Apo |
| Optical mounting | Air spaced |
| Glass types | ED et Crown |
| Optical coatings | Multicouche BBAR (BroadBand anti-reflection) |
| Aperture | 120mm |
| Standard |
|---|
| Focal length | 900mm |
| Focal ratio | F/7.5 |
| Resolution | 0.97" |
| Visual limiting magnitude | 12.1 |
| Light grasp | 293x |
| Image circle | NA |
| Photo field | NA |
| With TOA35-FL field flattener |
|---|
| Focal length | 882mm |
| Focal ratio | F/7.3 |
| Image circle | 40mm (60% non-vignetted) |
| Photo field | 2.6° @ 40mm image circle |
| Spot sizes | 7µm RMS @ center of field
7µm RMS @ 10mm off-axis
7µm RMS @ 20mm off-axis |
| With TOA35-RD reducer |
|---|
| Focal length | 672mm |
| Focal ratio | F/5.6 |
| Image circle | 40mm (60% non-vignetted) |
| Photo field | 3.4° @ 40mm image circle |
| Spots size | 4µm RMS @ center of field
6µm RMS @ 10mm off-axis
13µm RMS @ 20mm off-axis |
TSA-120 - Longitudinal view (lengths in mm) of the rack-and-pinion focuser
Specifications
| Spec. | TSA-120 |
|---|
| Tube length (mini/maxi) | 990mm |
| Tube diameter/dew-shield diameter | 125mm/160mm |
| Tube weight | 6.7 kg |
Optics
The TSA-120 is equipped with an apochromatic objective with triplet ED lenses of 120mm of diameter (F=900mm, F/7.7), 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-120 is proposed with a retractable dew shield.
Mechanics
The short tube of the TSA-120 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-120 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-120. The addition of the optional field corrector allows imaging at prime focus with the F/7.5 default focal ratio. The TOA-RD reducer (F/5.6) 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 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.
Spots 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.
ALTERNATIVE PRODUCTS
