Collimation issue?

[tom33pr]

Hi there,

I've decided to check my SW 130p for collimation.

Last night when I pointed the scope at a bright star and magnified it the secondary looked to be dead in the center of the bright, defocused star image - happy days!

Today I used the cheshire and the secondary looks perfectly aligned with the eyepiece (I inserted a wee bit of white paper between the primary and secondary so the judgment was more accurate), offset looks fine too...

The only thing that worries me is that I can see the outside screws (see the first photo) of the secondary reflected in the primary when looking through the collimator cap. It doesn't show it on the second photo because the image is too small, but I can see them... they are tiny but still...

Is this correct or should I consider tuning the secondary?

Thanks for looking in this.

[Bizibilder]

That looks OK. I suspect that the secondary holder is quite large on a small scope like the 130P so you can see the secondary screws - it wont matter. It has to be that size simply to fit all the screws in!

[John]

If the star images look good - it's all fine - you could end up making then not look fine by getting paranoid about adjusting things that don't need attention !.

It's so easy to get twitchy about adjusting everything, especially when it's cloudy

[Astro_Baby]

I'd stand to be corrected on this one but I think that would be normal to be honest on a 130. I cant ever see them on my 200 but thats because the secondary obscures them more completely.

The 130 on the other hand has almost the same sizze of secondary holder but a much smaller secondary mirror. I am sure its ok myself and would leave it alone especially as star testing is ok and the view through the cheshire is fine as well.

[tom33pr]

Guys, thanks a lot for the prompt reply.

Astro_Baby - great article on collimation!

One more question for the future reference - how often will I have to collimate the scope - considering it is handled gracefully

[Bizibilder]

It can vary quite a bit! I have a reflector in my observatory that has stayed in collimation for months. If you move your scope around then you will need to collimate more frequently - maybe every time you use it.

The secondary should stay in collimation unless you bash it. It would be the primary that may need a little "tweak" from time to time.

[Astro_Baby]

It varies - its most often related to the size of the scope and its design. A solid tube will usually do better than a truss tube and a smaller scope will do better than a bigger one. A 130 if its handled carefully should keep collimation almost forever. The secondary should almost never need it with just the odd tweak to the primary.

Even my 8" almost never has its secondary messed with (unless I am bored). The primary needs a quick tweak just after transport and set-up.