ASKAR FRA500 90 mm Öffnung f/5.6 Quintuplet Flatfield APO Astrograph - with with optical test

ASKAR FRA 500 90 mm f/5.6 Quintuplet Astrograph

ASKAR is the new line of selected telescopes for astrophotography. With these telescopes a high attention is paid to the optical, but also mechanical quality. FRA stands for refractor telescopes with integrated corrector element for a flat and corrected image field. The FRA series is mainly used for astrophotography.

Astrophotographic results obtained with this telescope on Astrobin

Here you can find some astrophotographs made with this telescope model: Link to Astrobin

The ASKAR FRA500 is a 5-element apo according to Petzval with 500 mm focal length, f/5.6 and 90 mm aperture. In the lens there are 2 ED glasses for a good correction of chromatic aberration. The apo is corrected for cameras up to full-frame.

The dew shield also provides good protection against stray light and is retractable. The large focuser holds even heavy cameras and allows clean focusing due to dual speed. The focuser offers a range of connections for all common astro threads. Also included is an adapter to M48x0.75, which is ideal for all cameras with 55 mm working distance. This adapter also has a possibility to screw in 2" filters.

Focusing the camera in the FRA500 apo

The corrector of the apo is permanently installed in the tube. As soon as you have focused the camera, you are also automatically at the correct distance. The laborious search for adapters in the appropriate thickness is no longer necessary.

A photo specialist, but also suitable for observation:

The ASKAR FRA400 is designed for astrophotography. However, due to the comfortable working distance, 2" star diagonals can also be connected. This turns the astrograph into a very nice spotting scope and telescope for astronomical observation and also landscape observation. We will be happy to advise you on the suitable adapter.

Increase of the speed to f/3.9

The focal ratio of f/5.6 is already relatively fast. But often one wishes for even faster optics. With the optional FRA400Red you can increase the speed from f/5.6 to f/3.9, thus halving the exposure time. The focal length is shortened to 351 mm.

This is how we hand over the apo to the stargazer:

Every single apo is checked in our technical department before it is put into storage in order to guarantee consistently high product quality.

The mechanics are tested and the focuser is optimally adjusted.

The lens is cosmetically checked and cleaned. We also check that all counter screws are correctly tightened. These often loosen during transportation.

The optics are collimated and the result is checked on the optical bench. The telescope is given a serial number.

An optical test is carried out, which is enclosed with the telescope (star images and ronchi image on the optical bench in autocollimation).

Only then are the telescopes handed over to the warehouse and prepared for dispatch.

Astrophotographic results obtained with this telescope on Astrobin

Here you can find some astrophotographs made with this telescope model: Link to Astrobin

Safety informations: PDF Download