M42 and friends.

[Hugh]

Wow ~ that's lovely. The diffraction spikes give the picture a nice 'twinkle'!

Pareidolia strikes and I can see a large-winged grey bird flying away from me. 

Hugh

[RobertM]

Hi Robert,

I suspect that there might be tilt (differential focus across the field of view) but I do not know how to check for it.

John

If you have a 2" diagonal, 2" nosepiece for your camera (or m48 extension tubes, laser pointer and a piece of wood 4" x 14" x 1/2" then you are well on your way - a bit low tec but surprisingly effective. I made one recently, will post a picture a bit later.

Edit: added pic of rig for sensor alignment:



Robert

[NoelC]

Robert
How do you use it?
Noel

[RobertM]

Here are some instructions, I hope they make sense !

This is a slight mod to the rig used by Starlight-Xpress. In this case the Camera is attached to a 2" nosepiece (or any M48 fitting) and placed in the Star diagonal. Placing the camera vertical allows the diagonal adjustment screw to take out all the slack so the camera can be rotated smoothly without any lateral movement. The laser pointer position is adjusted to maximise the parallax angle to the reflected return beam; this comes back past the laser and onto a wall (or other flat surface). The brightest spot should be, if the ccd has AR glass, the return beam from the sensor cover glass.

Rotate the camera in the diagonal and the reflected beam will describe a circle on the wall. Now adjust the camera collimation screws to remove any movement; I turned the camera till the one set of the camera adjustment screws was in line with the laser and furthest away from the wall. Adjustment depended on whether the laser spot needed to go up or down. If the spot was too high then the back of the camera needs to be raised slightly and vice versa if too low.

I used a weak laser beam of less than 5 milliWatt @ 532nm (green) to eliminate any chance of burning out any pixels on the sensor.

Note that this is the routine I used to adjust the sensor on my ASI2600MC and it should work on any camera but... disclaimer - you follow this at your own risk.