Askar 151PHQ Flatfield APO Astrograph - with optical test

Askar 151PHQ Quadruplet APO Astrograph

151PHQ is a long-focal-ratio, flatfield astrograph launched after 130PHQ. Instead of buying extra flatteners, calculating the backfocus of flattener or making tedious connection to match the distance, astrophotographers can simply equip it with any possible imaging devices, make the target stay at the focus, and then the whole optical system is perfect for imaging.

High quality imaging optics:
151PHQ has an aperture 21 mm larger than 130PHQ. The triplet lens with two ED glasses offers excellent control of chromatic and other aberrations. With its self-flattening design, due to the fourth optical element, 151PHQ offers strong advantages in astronomical imaging. It supports a medium frame (for example ASI461MM Pro) 60 mm image circle, has a fine spot diagram with tiny distortion of the peripheral stars, and its central RMS radius is less than 2 microns.

The Askar 151PHQ is a true all-rounder - it is designed as telescope for almost all applications:

Extended objects can be imaged. But equally, fine details of objects can be brought out when cameras with high resolution are used.

The use of different cameras with different flange focal lengths is no problem. Simply focus and you are always at the correct distance. The adapter battle is eliminated.

The focuser has large travel, so you can find the focus without problems.

The working distance or backfocus from the 2" receptacle is long enough to use 2" star diagonals. This turns the flatfield apo into a wide field telescope or even a planetary telescope, depending on the eyepiece used.

Practical features:
151PHQ comes with a telescopic lens hood, a high quality CNC machined and painted tube and attractive decorative parts. The rigid 3.4" focuser comes with 2" and 1.25" adapters and a finder base. When used with the optional 3" 0.7x flat field reducer, the telescope can reach a focal ratio of approx. f/4.9 and a focal length of approx. 740 mm, effectively reducing exposure time. The multifunctional handle comes with a central slot for attaching an M6 screw with an M6 screw hole. Standard Losmandy style dovetail plate, together with sturdy double tube ring, is perfectly suited for viewing and imaging.

The photographic 3.4" rack&pinion focuser deserves a special note:
The CNC focuser is optimized for photography and can handle a load of up to 8 kg. The adjustment range is very generous. The focusing is done via rack and pinion which is decoupled from the bearing of the draw tube. This guarantees fine and precise adjustment even at maximum load. In addition to the 1.25" and 2" receptacle, the focuser also offers an M86 thread for screw adaptations.

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.

Technical Information

Teleskop-Service has collected a lot of helpful information about refractors and provided it in English as a PDF file: refractors.pdf

Safety informations: PDF Download