Did I just seriously damage my scope?

[winsor]

I went to pick up my new dobsonian to move it outside and heard something metal fall and bounce around. Turns out the metal piece on the bottom of my eye piece fell into the scope and hit the mirror. It put a very small scratch, a fraction of an inch, on the mirror. Will this greatly affect my scope? Also, how do I know when to collimate. Sorry for all the newbie questions.

[kookbreaker]

It probably won't hurt it too much, but you don't want to do that very often.

How the <bleep> did your eyepiece base fall off?!

[aurora]

Look for other messages and links here on collimation. Try a search.

One way to tell is to do a star test, which is actually very sensitive. Start by focusing a star, and then racking the focus in and out slightly and see if the shape of the resulting blob is similar on each side of focus. If not, consider collimation.

[winsor]

k thanks a lot guys, i guess the base on the eye piece wasn't screwed on all the way.

[stktos]

I would not think the scratch would do very much at all to the quality of the image.
And the star test aurora suggested is a good way to tell.

[Nick Theodorakis]

If there is an astronomy club in your area, you might want to check the out; they may be able to help you with scope issues such as collimation.

Nick

[steffanie]

Hiya,

Give your supplier a ring to see if it does need collimation, i was told mine needed it and didn't have an iota how to but having rang i was told it was collimated at the shop already. Phew!

[RickJ]

Dobson's need recollimation at regular intervals. How often and roughly they are handled will determine how often this is needed. Some can go a year or two. Shipping nearly always gets them a bit out of factory alignment. At least that's been my experience. Plenty of websites cover this, just google the topic.

Scratches, if deep can scatter light lowering contrast. Most aren't this severe. If one is a dab of flat black paint will cure the problem. Years ago a guy went nuts at McDonald Observatory (janitor not astronomer) and fired a clip from his 9mm into the 107" mirror then when that didn't do much he took a ball peen hammer to it. That caused more damage. They've since bored out those areas and covered them with flat black. Scope is now more like a 106" as he took the hammer to the edges he could reach while the bullets hit well into the mirror. In any case the damage hasn't made much difference. I had a friend who was a grad student there when it happened, even before they ground out the damage he was still using the scope for his thesis work without much problem.

So I doubt your scratch will be much of a problem either. But do search out a local astronomy club. They will be a great help in many respects, not just this one. When I was starting at your level we had no club so I and a few others (including the grad student mentioned above) started one. It helped us greatly. He's now a planetary geologist at Brown University and the designer of the Deep Impact impact probe, another in the club was the head of the optics team that designed Gemini's two 8 meter scopes and now is in charge of the overall design of the proposed thirty meter telescope. You never know where a club can take you! Both say they'd never be where they are today without the help they got from our club. Google "astronomy clubs" for to find a club near you. Without your town and country I can't be more specific.

Rick

[spaceboy0]

my goodness did that crazy guy go to jail? poor mirror

[RickJ]

my goodness did that crazy guy go to jail? poor mirror

I don't remember. I think he was committed to the nut house. At the time he wasn't sane enough to stand trial Don't know if he ever was or what happened. If he went to trial he may have been charged with attempted murder as he did fire one shot at an astronomer. When he missed he went after the mirror, a much bigger target that didn't duck.

Rick