Discovery Astrophotography with ZWO ASTRO

Reason of Field Tilt problems and how to solve it

Applicable Product(s) : For All ASI Cameras

Description: Field tilt problems usually happen in imaging.  Optical axis, flattener lens, adapters, and sensor tilt are all causes of field tilt in images. This post is to help diagnose which issue is causing your field tilt problem.

What do I setup to test?

Your imaging setup is connected to the computer and there are many stars in the field of view.

Q: How do Itest if a tilt problem is caused by my telescope or by my camera

A: Take an image with your camera then rotate the camera 180 degrees (the telescope telescope doesn’t move). Thentake another image of the same field of view.

Analyze the images with software, such as CCDInspector 2.5.3.


If the field has an identical pattern after rotation, then the camera has a tilt problem.

sensor tilt

If the field has the same problem, but it has rotated 180 degrees, the telescope has a tilt problem.

optics tilt


Q: How to make sure tilt problem caused by adapters


  1. Remove suspect adapters, connect the camera directly to the telescope.
  2. Try another adapter.
  3. Take another set of images to test if the problem is gone


Q: I use a field flattener or a flattener/reducer, but I see coma in the corner of image.


  1. Usually this is caused by incorrect back focus (spacing between the reducer and camera sensor). Use suitable adapters make sure your camera is at critical  back focus for that flattener or reducer.
  2. Your image circle for that flattener or reducer is smaller than the camera sensor.




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