ASA 20 inch Hypergraph F3.8
All telescope tubes are manufactured of sandwich carbon fibre, and the external view by the high-grade sight carbon fibre workmanship. The tubes are covered inside with black velvet to avoid stray light. The use of carbon fibre makes the telescopes up to 60 % lighter and the focus remains long-term stable in temperature due to the insignificant extension coefficient. Thus neither focus shift nor flexure can affect the performance of the star shape.
ASA Astrographs have a fast focal ratio which helps to collect a lot of data within short exposure times and achieve a good signal to noise ratio.
Based on the uncompromisingly optical design by Dipl. Phys. Philipp Keller, Germany, the lenses which are used correct the field of the largest CCD arrays popular right now.
ASA Astrographs are available in two different Serials:
The H-series Astrographs are differ to the N-Serie basically by using a hyperbolic main mirror. In configuration with a particular calculated corrector this system provides you with the finest spot sizes available with fast systems.
Therefore the H-serial Astrograph will render his performance exclusively in conjunction in use with high-res CCD-cameras. With a fast focal ratio of f 3.0 this Astrograph is the ideal wide-field instrument. Specialists will admire those instruments.
The N-series Astrographs have a focal ration of f 3.8. Given the matching corrector the system can be shortened or be extended with a few movements.
Using the 3" Wynne Corrector (Standard with N-Serie Astrographs) one will achieve a focal ratio of f 3.6. With the 2" or the 3" Reducer a focal ratio of f 2.75 result while with the ASA Barlow Flat Corrector the focal ratio will be f 6.8.
All ASA astrographs have ASA optics of Suprax material with Zygno interferogram with P/V <1/7 lambda wave, 97% reflection.
All flat mirrors offer the same specs. On request we offer premium Sital mirrors by LOMO in configuration with our Astrographs. (longer delivery times) .
The focuser of our Astrographs have been beloaded with 8 kg for successful tests. To attain the weight of 8kg additional weights have to been added, because no camera system available on the market has such a heavy weight.
Basically the essential expose times with the fast Astrographs are at most in the range of 600 seconds for a sub frame. For external Guiding (Guidescope) one has to be attend that the focal length of the Guidescope is in a range of at least of the half of the focal length of the used Astrograph. In exceptional cases if one like to take expose times longer as 600 seconds for an image and in case if no internal guide chip is available, we would recommend an Off-Axis-System for guiding.