Hows my collimation?

[JR1987]

Ive been trying all night for the first time ever collimating. 

I've used a homemade collimation cap to do it. I've got it probably the best i think I can. i can't seem to get that offset circle in the middle straight. 

its hard to see in the picture but the dot from the eye hole is directly in the donut.

 

[Dave In Vermont]

If your scope is a  'fast' Newtonian - F/4, F/5, thereabouts - the offset is normal. Nothing to be concerned about. I realize most publications on collimation don't mention this, leading to confusion. But a member here has written an excellent guide to collimation which does put this fact in print. I can only wonder how many fast Newt-owners have hurled themselves in front of locomotives over this little faux pas.....

http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

Stop the Train!

Dave

[Charic]

One of the hardest things is to confirm  collimating results just  from a photograph alone.

If in the final view when observing, things look ok, then leave it alone.

If you carry out a Star test and the Airy disk is concentric, that will prove your setup. 

Try the tool, AlsCollAidV11.zip from here. http://www.iceinspace.com.au/files.html

You can overlay this tool over your own photograph to help check any alignment issues you think you may have?

[Jason D]

Ive been trying all night for the first time ever collimating. 

I've used a homemade collimation cap to do it. I've got it probably the best i think I can. i can't seem to get that offset circle in the middle straight. 

its hard to see in the picture but the dot from the eye hole is directly in the donut.

Your collimation looks good -- not perfect -- but really good.

The offset looks good too. Interestingly, I see a shiny arc around the secondary reflection. Is the surface of your secondary mirror fully aluminized? That is, does your flat surface of your secondary mirror includes a rough non-reflective perimeter?

Jason

[Peter Drew]

Good point Jason, well worth blackening the secondary edge.    

[happy-kat]

There is a brilliant little windows app that puts circles over an image so you can work out if it all lines up or not, but I don't have a link to it using my tablet.

[JR1987]

Ah nice little image attached there, gives me an idea of how much fine tuning it needs.

The secondary had a rough edge yes, I think the shiny arc is there because I had a light from my phone shining in there to show up the centre point of the collimation cap.

Just as a note my scope is a SW200PDS which is f5.

[Dave In Vermont]

I believe the program suggested for overlaying a photo/image on is Al's Collimation Aid - it's from Australia it appears:

http://www.iceinspace.com.au/forum/showthread.php?t=62696

You'll find the details on the link provided - from IceInSpace, an Australian forum much like this one.It's a nice little app.

Enjoy!

Dave

[JR1987]

Thanks for all yor help guys. I've adjusted the secondary mirror and I'm pretty sure I have it central now.

I have a laser collimatior and it's very almost collimatied but it is still creating a slight circle when rotated. But I was wondering, because I just plonked it into my focuser (now I feel I have it correctly collimated) the focuser has a little play and I've found that if I push it so the laser is centred in the donut then it moves into the target centre on the collimator, does this confirm my collimaton?

[happy-kat]

The laser could be out, there is a test you can do to check that it is collimated I gather.

I only use the collimation cap.

[Moonshane]

You may have done it now but in your pics it looks like the secondary needs rotating a little - top towards you. It is pretty close though.