I have been busy tweaking my new system to iron out all the bugs. One problem I had was image train flexure. This is very sensitive at F3!
This has been solved by the construction of an image train stabiliser. See image one below.
Here are two images about 5MB each.
http://d1355990.i49.quadrahosting.co..._08/41000_.jpg
http://d1355990.i49.quadrahosting.co..._08/42000_.jpg
They were 60s exposures in green with a Bahtinov Mask 1000 steps of the Atlas focuser apart. 1000 steps is 85 micron.
The image 42000_ is at focus in the centre brighter stars and at the bottom centre are also in focus. This means the sensor is orthogonal to the optic axis in the vertical.
But if you look at the RHS centre there are two brighter stars which are out of focus.
If you then look at these same two stars in image 41000_ they are then in focus! This means the RHS of the image is 85 micron closer to the front of the optic.
This of course means that the sensor is 85 micron closer on the LHS. So I need to shift the ITS to the right.
This is a very simple way to see what is happening visually to align any sensor. Like all simple elegant methods they are blindingly obvious in hindsight!
In fact if you suspect image train flexure this is a simple way to see if it varies depending on mount orientation with your system.
Here is deeep image.
This is 10x16 minutes of 3nm NII of NGC6334 and NGC 6357.
http://d1355990.i49.quadrahosting.com.au/2012_07/ngc6334&6357_ITS.jpg
The image is at the native resolution of the PL16803 camera.
Bert