Hi, I have just received the Catseye Auto collimating kit from Catseye
I just have one interesting question in regards to the instructions they mention about the secondary mirror on the Dobsonians.
Firstly, my Dobsonian is the Skywatcher 16' collapsible version with goto
In the instructions provided by Catseye, they talk and recommend moving the secondary mirror away from centre, they talk about moving it away from the eyepiece.
They give you a table that has the the size of your secondary mirror and the f/no of your scope, find these numbers and then it tells you how far to more the secondary away from the eyepiece, ( tells you how far to move it off centre ) in my case it works out to be 0.224"
So going by that i need to move the secondary 0.224" off centre away from the eyepiece.
So to make that a bit clearer, the instructions say:
For optimal "Axial" positioning of the secondary using the TLETUBE XLS/TELECAT XLS I highly recommend that you consider first setting the corresponding ( and aqual ) vertical offset away from the focuser.
Refer to the Offset cross-reference table on the last page and locate the nearest value to your secondary mirror size ( minor axis length ) in the left hand column; then read across to the f/no of your telescope listed across the top. The appropriate offset value is in inches.
The proceed to to set the vertical offset in a direction AWAY FROM THE FOCUSER by adjusting the spider attachment screws. Ultimately the difference from the focuser side to the secondary will be longer than the opposite side distance to the Secondary by twice the offset vaLue, The side to side distance should remain equal.
So after all that, for those that have used the Caytseye equipment, dose it read a seam correct to actually move the secondary away from the focuser.
I did some measurements and if i did this, although it isn't far, i don't have much thread left on the focuser side of the spider vanes.
Is it worth moving the secondary away from the focuser? will i gain much by doing this?
Just to me reads a tad odd as everything i have read about collimating the Dobsonians, everything says to make sure the secondary is dead centre of the scope and make sure the foucuser is square with the tube.
Where Catseye are saying to move the secondary off centre.
Any advice or information on this would be greatly appreciated.