How to Use a 2x Barlow Lens for Planetary Imaging

By Cloud Break Optics | Published: 2026-10-28

Category: How-to Guides

Learn how to use a 2x Barlow lens effectively for planetary astrophotography. This guide covers setup, focusing, and common mistakes to avoid.

Quick answer

To use a 2x Barlow lens for planetary imaging, insert it between the telescope and camera, extend the focal length to double magnification, and refocus carefully. This guide walks you through each step.

Why a 2x Barlow lens for planets?

A 2x Barlow lens effectively doubles your telescope's focal length, increasing magnification without swapping eyepieces. For planetary imaging, this lets you fill more of the camera sensor with the planet, capturing finer detail—provided the atmosphere cooperates. The trade-off is a dimmer image and greater sensitivity to poor seeing conditions, so use it on steady nights.

Choosing the right Barlow

Not all 2x Barlows are equal. A quality unit with multi-coated optics, like the Takahashi 1.25" 2x Barlow (TKA00597), minimizes aberrations and maintains contrast. Cheaper models can introduce chromatic aberration or softness, which defeats the purpose of higher magnification. Stick to reputable brands for reliable results.

Step-by-step guide to using a 2x Barlow for planetary imaging

Attach the Barlow to the telescope: Remove the eyepiece or camera from the focuser. Insert the Barlow lens directly into the focuser drawtube, then attach your planetary camera to the Barlow's barrel. Ensure the connection is snug but not over-tightened. Common mistake: Using a Barlow with a camera that has a long nosepiece can shift the focal plane—check that the camera reaches focus.
Focus on a bright star or planet: Point the telescope at a bright star or the planet itself. Use a Bahtinov mask or focus aid in your capture software to achieve sharp focus. A 2x Barlow reduces depth of field, so focusing is more critical than without it. Checkpoint: If focus seems impossible, the Barlow may be too far inside the focuser—try moving it out slightly.
Adjust exposure and gain: Because a 2x Barlow dims the image, increase exposure time or gain in your camera software to maintain a histogram around 70-80%. Keep exposure under 30 ms to avoid blur from atmospheric turbulence. Common mistake: Over-gaining introduces noise. Use the lowest gain that still gives a usable histogram.
Capture a video, not a single frame: Record 60-90 seconds of video at the highest frame rate your camera supports. The Barlow magnifies atmospheric wobble, so stacking many frames helps average out the blur and reveal sharp details. Checkpoint: If the planet drifts across the sensor during capture, enable tracking or manually re-center between clips.
Process the video in stacking software: Load the video into software like AutoStakkert! or Registax. Select the best frames (typically 30-50% of the total) and stack them. Apply sharpening cautiously—the Barlow already provides high magnification, so over-sharpening can create artifacts. Common mistake: Stacking too few frames leaves noise; stacking too many includes blurry frames. Stick to the recommended percentage.

Product facts

1.25" 2x Barlow (TKA00597): The Takahashi 1.25" 2x Barlow (TKA00597) is an astrophotography accessory from the Takahashi brand. Its optical quality helps preserve image sharpness at double magnification, reducing the risk of soft planetary images.
1.25" 2x Barlow (TKA00597)