T-Adapter-C90 and Barlow T-Adapter 1 1/4 inches and T-ring for Canon EOS and Canon 40D

This post is the first part of a small series showing how to connect a Canon EOS DSLR to the Celestron NexStar 4SE for prime-focus astrophotography. Before assembling anything, here are the individual components you need: the T-Adapter-C90, Barlow T-Adapter 1¼ inches, a Canon EOS T-ring, and the Canon EOS 40D camera body.

Photographing the parts separately helps beginners understand how each piece looks and where it will eventually fit in the optical path. Later posts in this series will show the full assembly and the final connection to the telescope.

T-Adapter-C90, Barlow T-Adapter 1 1/4 inches, T-ring for Canon EOS, Canon 40D - Astrophotograpgy adapter setup for Celestron 4SE 

Components Shown in the Photo

• Canon EOS 40D DSLR camera body
• Celestron T-Adapter-C90 (93635-A)
• Barlow T-Adapter 1¼ inches (Celestron 93640)
• Canon EOS T-ring

This post only shows the individual pieces. In the next steps, you will see how these parts combine into a full optical train for prime-focus imaging or higher-magnification setups using the 1¼-inch Barlow T-Adapter. By understanding the components first, it becomes much easier to follow the later assembly photos and the final telescope-to-camera configuration.

Assembly Series: Connecting a Canon EOS Camera to the Celestron NexStar 4SE

• Part 1 – Components: T-Adapter-C90, Barlow T-Adapter 1¼", T-ring, Canon 40D (this page)
• Part 2 – NexStar 4SE with T-Adapter-C90 and Canon EOS 40D
• Part 3 – Assembled configuration with Barlow T-Adapter and Canon EOS 40D
• Part 4 – 4SE telescope with Barlow T-Adapter 1¼", Erect Image Diagonal, and Canon EOS 40D

4se Celestron with Barlow t-Adapter and Canon EOS 40D

This post shows the second assembled configuration for attaching a Canon EOS DSLR to the Celestron NexStar 4SE. In this setup, the camera is mounted using the 1¼-inch Barlow T-Adapter (93640), providing additional magnification while still operating in true prime-focus mode.

This configuration follows the first assembled setup using the T-Adapter-C90 on the rear port. While both deliver native prime focus, the camera is attached to a different optical output port of the telescope.

Second assembled configuration: 4SE with Barlow T-Adapter 1¼", Canon EOS T-ring, and Canon EOS 40D on the top optical port

How This Assembly Differs from the First Assembled Configuration

In the first assembled setup (Part 2), the camera attaches to the rear threaded photographic adapter. In this second configuration, the camera attaches to the top diagonal barrel, the same position normally used by the finderscope bracket.

• Rear port (Part 2): Camera inline with optical tube.
• Top port (this post): Camera faces upward for easier LCD viewing and better weight balance.

Both positions are true prime focus, only using different light output paths.

Understanding the Two Camera Attachment Points on the Celestron 4SE

The Celestron NexStar 4SE includes a built-in Flip Mirror Control that allows light to exit through either:

• Rear threaded photographic port (used in Part 2)
• Top diagonal port (used in this Part 3 configuration)

Switching the flip mirror determines which port receives the light. This second assembled configuration simply uses the top port + 1¼-inch Barlow T-Adapter for increased magnification and easier access to the camera screen.

Equipment Used

• Celestron NexStar 4SE Maksutov-Cassegrain
• Barlow T-Adapter 1¼" (93640)
• Canon EOS T-ring
• Canon EOS 40D DSLR

Assembly Series: Connecting a Canon EOS Camera to the Celestron NexStar 4SE

• Part 1 – Components Only (all adapters and camera shown separately)
• Part 2 – First Assembled Configuration: T-Adapter-C90 on Rear Port (Prime Focus)
• Part 3 – Second Assembled Configuration: Barlow T-Adapter on Top Port (Prime Focus)
• Part 4 – Third Assembled Configuration: Barlow T-Adapter + Erect Image Diagonal

Blue Moon November 21 2010 Celestron 4se Canon 40D

This Blue Moon from November 21, 2010 was photographed in Brooklyn using a Canon 40D and Celestron NexStar 4SE telescope, showing how different white balance settings reveal natural lunar colors.

Color full moon, blue moon, Canon 40D, Celestron 4SE

A blue moon can refer to the third full moon in a season with four full moons. The earliest recorded English usage of the term "blue moon" was in a 1528. In 2010 Blue Moon was November 21.

Equipment Used

• Canon EOS 40D DSLR
• Celestron NexStar 4SE Telescope

Color-Enhanced Blue Moon

1. Neutralize the colors (the median of the values of R, G and B is the same).
2. Create two duplicated layers.
3. First layer set as luminosity
4. Saturate the second layer.
5. Make invisible main background layer.
6. Play games with best parameters
So those colors are real, and the only difference is that they've been exaggerated a bit :)

Blue Moon - White Balance: Tungsten light

Blue Moon Celestron 4SE Canon 40D Brooklyn Astronomy

White-Black Moon - White Balance: Cloudy, twilight, sunset

Full Moon Celestron 4SE Canon 40D Brooklyn Astronomy

Yellow-Red Moon - White Balance: Shade

Full Moon Celestron 4SE Canon 40D

Related Astrophotography Posts

• NexStar 4se telescope with T-Adapter-C90 (93635-A) and Canon EOS 40D
• RegiStax 6 - Astrophotography Saturn - Testing new version v6
• The Solar Eclipse of April 8, 2024: An HDR Revelation of the Sun's Corona from Westport, New York
• Removing Light pollution Astrophotography Urban Astronomy
• Rainbow of the Milky Way and the Eternal Baobab — Tarangire, Tanzania

This Blue Moon project remains one of my favorite lunar imaging sessions. Using simple backyard equipment, the Celestron 4SE and Canon 40D can reveal a surprising range of natural lunar colors through different white balance settings.