Does the corrected field diameter shrink if the reducer is mounted at say 30 mm from the etalon output? If yes, how much, approximately?
Changing the distance between the TZ and the reducer should have relatively little effect. The design is calculated for about 50mm distance. +-10mm should have no effect.
SolarSpectrum Telecompressors 0.4 / 0.7x
Suitable for all SolarSpectrum H-alpha Filters - with 2" male threads on both sidesPossible adaptations consisting of Baader T-Adapter, Zeiss T-2 changer system, T-2 Prism and Baader Eudiascopic eyepiece f = 30 mm
Solar Spectrum H-alpha filters require parallel light with a ray path of at least f/30. This is achieved by a focal length with our telecentric systems (and possibly also by dimming the lens with the iris). Because of the focal length extension in many telescopes the sun is not completely visually apparent when using eyepieces with f = 30 to 35 mm.
Note: both Baader Solar Spectrum Telecompressors are mounted straight onto the Solar Spectrum body rear end and reduce the f/30 ratio by a factor of 0.4x (#2459260) respectively 0.7x (#2459259). As a result, a much larger portion of the solar surface comes into view, depending on the size of the Etalon mounted inside the Solar Spectrum filter.
A telecompressor is used to adjust the focal length to possibly poor seeing conditions and / or enlarging the field for photographic- or webcam applications.
To attach the telecompressor use our 2″ Universal flange (# 295 8240); it gets attached with four screws directly onto the filter housing (see illustration), the telecompressor is mounted directly into the 2″ thread of the universal flange. The main thread of the compressor also is a 2″ male thread. This can be changed if necessary with parts from our T-2 accessories system either to a T-2 internal or external thread.
Application examples of the 0.7x Telecompressor:
The picture shows one possible combination, consisting of Baader T-Adapter (BTA # 240 8160 Part 21), Zeiss T-2 exchange system consisting of changer and change ring (# 245 6321 Part 6 and Part 7), one of our T-2 prisms and a Baader Eudiascopic eyepiece f = 30 mm.
The astro-images show the effectivness and the enlarging of the field of view with the 0.7x solar spectrum telecompressor on a 6 “refractor at f = 2250mm, dimmed down to 75mm, thus at f/30. The comparisons show the operation of the SolarSpectrum telecompressor. Primary focal length of the photographing lens is 2250 mm, reduced to 1700mm telephoto compressor The advantages: significantly larger field of view and reduce of the necessary exposure times!