Askar 140APO 1.0x Full Frame Flattener User Guide

Quick guide from the manual

The Askar 140APO 1.0x Full Frame Flattener is a dedicated optical accessory designed specifically for the Askar 140APO telescope. Its primary function is to correct field curvature, ensuring that stars remain sharp and round across the entire field of view, including the corners of full-frame sensors. This flattener maintains the native focal length of the telescope (1.0x magnification).

Installation

To install the flattener, ensure your telescope focuser is retracted. Remove the dust cap from the rear of the telescope focuser. Thread the flattener securely onto the telescope's focuser drawtube. Ensure the connection is tight and square to prevent image tilt. Once the flattener is attached, you can connect your camera imaging train to the rear of the flattener using the appropriate adapters.

Back Focus Requirements

Achieving the correct back focus is critical for the performance of the flattener. The standard back focus distance for this unit is typically 55mm from the rear shoulder of the flattener. If you are using a dedicated astronomy camera, you will need to calculate the distance of your camera sensor, filter wheel, and any other spacers to ensure the total distance equals 55mm. Deviating from this distance will result in distorted stars at the edges of the frame.

Camera Connection

The rear of the flattener usually features standard M48 or M54 threads to accommodate various camera adapters. Ensure that your imaging train is securely fastened. If using a heavy camera setup, ensure that the focuser drawtube is locked or tightened sufficiently to prevent slippage during long exposures.

Maintenance and Care

Keep the optical surfaces clean and free of dust. Use a high-quality lens blower to remove loose particles. If cleaning is necessary, use a specialized optical cleaning solution and a microfiber cloth, wiping gently in a circular motion from the center outward. Always replace the dust caps when the flattener is not in use to protect the glass from scratches and environmental contaminants.