Does my scope need colimating?

[ChrisThePuma]

Hi All

I recently flocked my SW 150PL and in the process had to remove both mirrors and everything else.

After the rebuild i set up the scope and checked the colimation roughly and it looked ok (i think) i found a bright star - pointed the scope at it and de-focused. The blur around the star was perfectly central and round.

Does the above point to good colimation? I know my scope is a slow one so not as crutial - the thing is, since doing the flocking, things i look at have a cross coming out from them (like using a 4 point starburst filter) so i am wondering if i did something wrong. could this 4 point star be the secondary mirror spider? Is this normal as i dont recall it being there before?

thanks

chris

[damnut]

Hi Chris,

If you have taken your scope apart, it will need properly collimating not just roughly!. Plenty of guides on line , youtube and Astrobaby has a guide on SGL.

Cheers

[umadog]

The "starburst" is due to the secondary holder. It was always there. If the spider vanes are no longer edge-on (i.e. slightly rotated) then they will appear thicker as viewed from the primary and so will produce more prominent diffraction spikes. You want to check that they aren't twisted.

[Grunthos]

Hi Chris,

If you have taken your scope apart, it will need properly collimating not just roughly!. Plenty of guides on line , youtube and Astrobaby has a guide on SGL.

Cheers

Astrobaby guide to collimation can be found here

[ChrisThePuma]

great - thanks - i will check it out this weekend

[steelfixer]

I would second Umadog's reply with the spider.

Also by flocking it you will have increased the contrast greatly.

[jimmyjamjoejoe]

I would second Umadog's reply with the spider.

Also by flocking it you will have increased the contrast greatly.

Likewise to umadog, and yeah, the added contrast may just be making these diffraction spikes a little more obvious.