Can't think of a practical way to check for tilt indoors. My first test after I got my rig up and running was a star field test. I found a nice rich field in Cygnus and took some exposures with which to check that my field was flat and to check for tilt. I thought I had tilt but it ended up being a backspacing issue, which was easily corrected with a couple shims.
I don't think a manufacturer's certification for "straightness" is practical. It would drive the cost of components up to add additional testing and tighter tolerances than they already provide. And given the wealth of third party components we mate together it would be a difficult task to tell which component of an imaging train is the culprit for tilt.
I think most people have success with camera tilt adapters to fix the issue.
See post 4 & 10 of this thread for a way to test for camera sensor tilt indoors.
CCDer described an apparatus that makes adjusting for sensor tilt indoors using a laser and some plexiglass.
I checked and corrected for tilt on a new camera indoors using a similar technique without needing to build an apparatus. It worked so well I will repeat it here so hopefully it may help others:
1.) I used a Glatter laser, though any red laser will do. Place the laser with ample space underneath a sturdy piece of flat and clear glass/plexiglass (glass table, small aquarium, etc). In my case I first used an empty aquarium flipped on its side with the laser standing inside pointing at the opposing wall above it, and later used a glass plate placed on a tall wire closet shelf with the laser at floor level pointing up to it.
2.) Align the laser beam such that the beam is reflected back onto the source. This can be done with any kind of shim, paper, or you can think of a better way to adjust tilt. In the end the laser beam just needs to hit the flat glass and fold back onto itself and stay there, so achieve this any way you can.
3.) Place the camera with spacers/oag/etc attached on top of the glass such that the beam passes through the glass and hits near the center of the sensor. Assuming your camera has a tilt plate you will be using it to adjust out the tilt, if not then you will need to use a tilt plate in the imaging train.
4.) Use a (silver) sharpie to draw a ring on the glass around the bottom of the imaging train pressing against the glass (spacer in my case) and a tick mark on the spacer and glass such that you can place the imaging train back down in the same spot after picking it up to adjust the tilt screws.
5.) Adjust the tilt plate until the return spot off of the sensor is reflected back onto the laser source. This part can be a little tedious with the push pull tilt plate but it is certainly much easier and convenient than spending a night outside in the dark iterating on star shapes or tilt models.
The return beam off the glass will have diffraction rings, and the return spot off of the sensor will be bloated, so you can only be so accurate, but it worked well enough to solve all tilt issues I was having at the time with that new camera.
Edited by Poynting, 27 September 2021 - 07:56 PM.