Adjusting Tilt in Astrophotography | Methods & Software Tools

Adjusting tilt in an astrophotography camera and telescope system is crucial for achieving sharp, well-corrected images across the entire field of view.

Tilt refers to a misalignment between the camera sensor and the optical axis of the telescope, which can cause stars to appear elongated or out of focus in certain areas of the image.

Thankfully, many software tools allow you to measure the amount of tilt in your imaging train, and even dedicated devices such as a TiltPrecision instrument.

Adjusting tilt in your astrophotography system can be tricky to diagnose and correct – but it’s worth it.

Why Tilt Matters:

Field Flatness & Focus Consistency – If the camera sensor isn’t perfectly aligned with the telescope’s focal plane, different areas of the image will have varying focus levels. This leads to one side of the frame being sharper than the other.
Star Shape & Aberrations – A tilted sensor can exaggerate optical aberrations like coma, astigmatism, and field curvature, making stars appear stretched or misshapen, especially at the edges.
Optimal Performance with Flatteners & Reducers – Many astrophotographers use field flatteners or focal reducers to correct optical distortions. A tilted sensor can make these corrections uneven, reducing their effectiveness.
High-Pixel-Density Sensors Are Less Forgiving – Modern astro cameras with small pixels demand precise optical alignment. Any tilt can be more noticeable in high-resolution images, revealing flaws that might be hidden with a lower-resolution sensor.

Cloudy Nights user Chen posted his tilt results using the William Optics Cat 91 (9% tilt across the image field).

How to Adjust Tilt:

Use a Tilt Adapter – Many astrophotography cameras and filter wheels include an adjustable tilt plate, allowing fine-tuned sensor alignment.
Test with Star Field Images – Capture test shots of a dense star field and analyze whether stars are evenly sharp across the frame.
Collimate & Align the Optics First – Ensure the telescope is properly collimated and the imaging train is securely connected before making tilt adjustments.
Adjust in Small Increments – Fine-tune tilt adjustments in small steps, taking test shots and evaluating results after each change.

The William Optics Image Plane Tilt Adjuster for the RedCat 51 (version 1).

Personal Experience:

I ran into tilt issues with my ZWO ASI2400MC Pro and William Optics RedCat 71, which took some trial and error to resolve. At first, I kept tweaking the tilt plate and analyzing my images to chase down the issue.

But I quickly learned that overanalyzing can sometimes make things worse. If you’re not careful, overcorrecting can introduce new tilt problems.

Sometimes, a slight imperfection is better than endless fine-tuning that throws everything out of balance.

Proper tilt adjustment is often the final step in optimizing an imaging system. It ensures crisp, well-focused stars across the entire field. It can be a tedious process, but once dialed in, the difference in image quality is significant.

The aberration inspector tool in PixInsight is a great way to assess tilt in your camera and telescope.

Tools to Help You Measure Tilt

There are several software tools that can help analyze and calculate sensor tilt in your astrophotography imaging train.

These tools allow you to diagnose tilt issues by evaluating star shapes, field curvature, and focus consistency across the frame.

Here are some of the most popular options:

1. PixInsight (Aberration Inspector & Image Analysis Tools)

PixInsight offers tools like Aberration Inspector and FWHMEccentricity, which help analyze field curvature, star sharpness, and sensor tilt.
The Dynamic PSF (Point Spread Function) tool can measure FWHM (Full Width at Half Maximum) across the field to check for inconsistencies.

2. ASTAP (Astrometric Stacking Program)

ASTAP includes a Tilt Indication Tool, which measures star sharpness and focus consistency across the image.
Provides a numerical tilt percentage and a visual representation of tilt across different image quadrants.
Free to use and works with FITS image files.

3. CCD Inspector (Paid, but powerful for tilt analysis)

One of the most widely used tools for sensor tilt and field curvature analysis.
Provides a 3D curvature map and measures star eccentricity to highlight tilt issues.
Can analyze multiple images over time to track changes in your imaging train.

4. N.I.N.A. (Nighttime Imaging ‘N’ Astronomy) (Hocus Focus Plugin)

The Hocus Focus plugin for N.I.N.A. provides advanced autofocus metrics and a dedicated tilt analysis tool.
Uses multi-region autofocus to detect tilt across different areas of the frame.
Free and open-source, making it a great choice for users of N.I.N.A.

5. Sharpcap Pro (Sensor Analysis Tools)

The Sensor Analysis tool in Sharpcap Pro can help measure sensor tilt and backfocus issues.
More commonly used for planetary imaging but still useful for deep-sky sensor alignment.

6. Prism (Advanced Observatory Control Software)

Prism has a Collimation & Tilt Measurement Tool that can help diagnose tilt in your optical system.
More commonly used in professional observatory setups but still available for amateur astrophotographers.

There are varying opinions of the usefulness and value of CCD inspector (Cloudy Nights Discussion).

DIY Method: A Laser Pointer

The following video walks you through the process of testing tilt in your optical system using a DIY laser pointer, a simple camera mount, and a screen.

The detailed instructions to build this setup can be found here. This method has worked for many amateur astrophotographers who have trouble with tilt in their astronomy cameras.

How to adjust tilt in your CMOS astronomy camera (EXO Photography).

No matter which method you use to adjust the tilt in your astrophotography system, it will involve some trial and error. I wish you the best of luck in diagnosing and correcting your tilt issues, and I hope you learned something new about your equipment.

Trevor Jones is an astrophotographer and a valued member of the RASC. His passion is inspiring others to start their astrophotography journey on YouTube so they can appreciate the night sky as much as he does. His images have been featured in astronomy books & online publications, including the NASA Astronomy Picture of the Day (APOD).