This post shows the third assembled configuration for attaching a Canon EOS DSLR to the Celestron NexStar 4SE. In this setup, the camera connects to the rear port of the telescope, but instead of attaching the DSLR directly, this configuration uses an Erect Image Diagonal (94116) between the telescope and the 1¼-inch Barlow T-Adapter.
This places the DSLR in a horizontal orientation, which becomes especially convenient when the telescope is pointed around 45° above the horizon. Even as the optical tube tilts upward, the camera remains easy to reach, focus, and frame. Although the diagonal changes the direction of the camera, the configuration still operates in true prime-focus mode.
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| Celestron NexStar 4SE with Erect Image Diagonal (94116), Barlow T-Adapter 1¼", and Canon EOS 40D. |
How This Configuration Works
The Erect Image Diagonal attaches to the rear threaded port, and the 1¼-inch Barlow T-Adapter is inserted into the diagonal’s eyepiece holder. The Canon EOS T-ring and 40D DSLR attach to the Barlow adapter.
This provides a comfortable horizontal camera position, ideal when the telescope is pointed toward objects at mid-altitude angles (~45° above the horizon). Because the telescope’s native focal path is preserved, this remains true prime-focus astrophotography.
When This Configuration Is Most Useful
This setup is especially effective when photographing targets located around 45° above the horizon. At these angles, the telescope tube is tilted upward while the DSLR remains horizontal, making focusing and framing much easier.
All three assembled configurations in this series have their own advantages and limitations. Depending on the altitude angle of your target — low, mid-altitude, or near zenith — you can select the configuration that offers the most comfortable and stable camera position.
Comparison With Earlier Configurations
- Part 2 – First Assembled Configuration: Straight-through rear port using T-Adapter-C90
- Part 3 – Second Assembled Configuration: Top port via flip mirror with 1¼" Barlow T-Adapter
- This Part 4 – Third Assembled Configuration: Rear port + Erect Image Diagonal + Barlow, DSLR horizontal — ideal for ~45° elevation
Equipment Used
- Celestron NexStar 4SE Maksutov-Cassegrain telescope
- Erect Image Diagonal (94116)
- 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
- Part 2 – First Assembled Configuration (Rear Port, T-Adapter-C90)
- Part 3 – Second Assembled Configuration (Top Port, Barlow T-Adapter)
- Part 4 – Third Assembled Configuration (Rear Port, Erect Image Diagonal + Barlow)
Comparison of the Three Assembled DSLR Configurations on the Celestron NexStar 4SE
| Configuration | Camera Port Used | Camera Orientation | Best For (Altitude Angle) | Advantages |
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Part 2 – Straight Rear Port T-Adapter-C90 + Canon EOS |
Rear Threaded Photographic Adapter | Inline with telescope tube |
Low altitude (near horizon) Best mechanical stability. |
• Shortest optical path • Strong support • Best for Moon, planets, low-angle objects |
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Part 3 – Top Port via Flip Mirror Barlow T-Adapter 1¼" + Canon EOS |
Top Diagonal Barrel (Flip Mirror Output) | Camera facing upward |
High altitude (70–90°) Ideal near zenith. |
• Very easy LCD viewing • Weight close to mount arm • Excellent for objects high in the sky |
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Part 4 – Rear Port + Erect Image Diagonal Diagonal → Barlow → Canon EOS |
Rear Threaded Port → Diagonal | DSLR horizontal via diagonal |
Mid-altitude (~45°) Most comfortable orientation. |
• Camera stays horizontal • Very ergonomic focusing • Great for clusters and mid-altitude targets |
Each configuration has its own strengths, limitations, and ideal angle ranges. By choosing the correct setup based on the altitude of your astrophotography target, you can achieve the most comfortable camera position and the best mechanical stability with the Celestron NexStar 4SE.
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