Detailed advice on newtonians - help needed.

[Aenima]

I have a 130p SW Explorer/650mm-fl and having persistent issues with collimation/image quality and as i'm new to collimating I really dont know which is the greater problem.

First, with collimating, I have got a basic cheshire and am pretty much guessing by lining up the mirror donut with the reflection of the cheshire hole (As in the intstructions). There still seems to be alot of room for errors, as well as being reluctant to fiddle with the secondary as its very delicate and I dont know for sure what to do with it.

Also the star test is difficult as the focuser imposes on the image creating a straight edge (small but noticable) when defocused and again I dont know for sure what to do while startesting with the adjustments and angles etc.

I really have been trying to get my scope collimated for months now and need help as i'm out of ideas, and my image is suffering in quality especially at high magnification (BTW with a 130p what is the highest magnification I can get ie 4mm plossl or 5x barlow? Or other combinations?) because it gets blurry at high power and also in a medium power something like venus has a kind of multiple ghost-like image, like replicas grouped around the main, brightest, image.

I really feel a little out of my depth now, could use the expert advice of a kind, knowledgable astronomer out there. Any help would be greatly appreciated!

Regards,

Jay.

[umadog]

Collimation involves fiddling with the secondary. If you only adjust the primary then you can't achieve collimation. You have to get over your fear and just do it. Here are a load of useful links: Rob Campbell's Home Page

Pay particular attention to the first three links. Read them carefully. Ask here if you have questions.

The reason your star test looks as it does is because you haven't adjusted the secondary.

Your 4 mm is quite high power so views will look blurry unless everything is bang on.

[Welrod50]

If I were in your position, and been trying to sort this for such a long time, I would consider taking it somewhere and have them do it for you. I can understand your reluctance to fiddle with it. I have a 130 SW and it is fine, but if it were in need of collimating, I would probably take it to me nearest store (whereever it may be).

That way, you're covered if anything goes wrong and it should be done quickly and correctly.

Good luck

Scott.

[knobby]

Jay, try a club near you, I'm sure someone could help you there

Good luck

[Islander]

If you adjust the secondary, make sure you keep the tube horizontal so that if you accidentally drop a tool it won't crash into the primary

This site gives you a detailed description of collimation:

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

[Aenima]

Umadog, that's an interesting idea, thank you. Appreciate the advice.

As I havent had the scope long I assume the secondary - having not been knocked or wrongly adjusted by me - is okay and the problem was probably in the way the scope is put together, ie focuser tube would always intrude slightly. But when I look into the open focus tube the secondary looks relatively central, and also through the cheshire it is difficult to see exactly how the image is not right, however the pics make it look I cant seem to get that perfect symmetry on mine.

I wonder at the accuracy of my collimator, the cross wires are just out of focus when seen through the eyehole as well as slightly off center as a crosshair. Also the ring that marks center on the primary could be a little off, I dont know how to tell for sure.

I will save up for a laser now, though, as it gives me yet another reference point and hopefully make the job less uncertain.

A good question to start a thread would be how to collimate a collimator....?

Anyhoo, Thank you to those who left me tips and advice, your patience is gratefully appreciated.

Clear skies and collimated scopes.....

J.

PS. I'm not using the 4mm with 5x barlow, those were only examples, but I did wonder about the short focal length and whether the high power eyepiece is better than normal eyepiece + 5X barlow. The barlow increases the focal length doesn't it?