Now you have the telescope collimated, it’s time to take some images to check the rest of the system. You
need to take one image at focus and another just a little bit out of focus.
FRONT LENS ADJUSTMENT
Now look at the out of focus image. If the stars appear deformed then there is too much stress on front
lens from mechanics. This could be caused from a prior poor adjustment and/or a big temperature
change after adjustment. While you can collimate the telescope using the collimation screws on the back
(as noted above), the front lens can also be adjusted with a very different effect. The front lens will
control the stars shape roundness and can remove or introduce aberrations (most common one is
astigmatism).
For example, if the stars look like the two below, that means you have the front lens under too much
tension which is introducing astigmatism and needs to be fixed.
If you get round stars like the ones below then you shouldn’t touch the front lens.
NOTE
:
to check the front lens, images must be taken in intra-focal position and always in the center,
meanwhile collimation is done with extra-focal stars.
To adjust the front lens, take the allen screws provided and follow instructions in next page.
Stars are deformed:
the front lens is tensioned
