rustigsmed
25-01-2017, 11:40 AM
hi,
been very relaxed on collimation over the years - but want to nail it now.
my process:
all spider vanes equal in length to centre.
I seem to be getting the secondary in line with the focuser ok and appearing circular (also tape measure middle of focuser to front of scope, front of scope to approximate middle of secondary).
then adjust to seeing all 3 clips of the primary on the secondary (1.25" sight tube cannot see the outer perimeter of the secondary - so I had to eyeball it through the 2" focuser).
barlow laser used to adjust secondary tilt to centre spot on primary.
primary adjusted to align with secondary.
go back to first step and the three clips of the primary have moved so that they are not so central sometimes one disappearing or being on the cusp of disappearing.
I have spent hours on this and have it so that the laser is all aligned and that I can just see all 3 clips although its just on view.
is there a simple cause? I am missing something?
ie do I need an offset at f4?
is it because my secondary is undersized (and therefore the third clip isn't such an issue? secondary is 88mm and primary 303mm
is it that much of a problem?
attached below is
- view down the sight tube after 'collimation' (note you cannot see any clips when using the sight tube) - it looks ok.
- view through the 2" focuser showing the clip layout at the end of the process (with clip at around 1- o'clock now missing - not so ok).
tips appreciated.
rusty
been very relaxed on collimation over the years - but want to nail it now.
my process:
all spider vanes equal in length to centre.
I seem to be getting the secondary in line with the focuser ok and appearing circular (also tape measure middle of focuser to front of scope, front of scope to approximate middle of secondary).
then adjust to seeing all 3 clips of the primary on the secondary (1.25" sight tube cannot see the outer perimeter of the secondary - so I had to eyeball it through the 2" focuser).
barlow laser used to adjust secondary tilt to centre spot on primary.
primary adjusted to align with secondary.
go back to first step and the three clips of the primary have moved so that they are not so central sometimes one disappearing or being on the cusp of disappearing.
I have spent hours on this and have it so that the laser is all aligned and that I can just see all 3 clips although its just on view.
is there a simple cause? I am missing something?
ie do I need an offset at f4?
is it because my secondary is undersized (and therefore the third clip isn't such an issue? secondary is 88mm and primary 303mm
is it that much of a problem?
attached below is
- view down the sight tube after 'collimation' (note you cannot see any clips when using the sight tube) - it looks ok.
- view through the 2" focuser showing the clip layout at the end of the process (with clip at around 1- o'clock now missing - not so ok).
tips appreciated.
rusty