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Bobs Knobs for 10"LX/GPS

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19 years 3 months ago #10694 by Dougal
Bobs Knobs for 10"LX/GPS was created by Dougal
Guys,
Over the weekend I got a bit adventureous and decided to install the Bobs Knobs that I had for my 10" LX200GPS.

What a mistake.

To begin, the scope was in perfect collimation for the day I bought it, never had to touch the secondary with that little allen key, but I figured these Bobs Knobs were supposed to be the Bees Knees so I put them in.
Turns out I made a Bobs Balls out of my scope.
Now cant's get decent collimation on the thing at all! I'm getting this stupid flare/ tail on the stars no matter how much tweeking of the knobs I do, I can't get rid of it. I was looking at Jupiter on Friday night (or trying to) and there was no detail at all, I might have just been looking at some non-descript star, but with a tail. I've done the whole "out of focus doughnut rings" thing, but still no use.

I also have the precision steel gears kit for it, but the only place I'm going to put those is in the bottom of my neighbours pond, after this experience.

Did any of you go through this pain?

Seamus :cry:

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19 years 3 months ago #10695 by dmcdona
Replied by dmcdona on topic Re: Bobs Knobs for 10"LX/GPS
Seamus - that's a real bummer. I went through a similar situation with a Newtonian when I decided to move the secondary. It took me three nights to get it back to collimation.

I'm not intimately familiar with Bob's knobs or the LX200. I'd try and do a search for an LX200 group - there must be one out there and I'm sure someone has a solution for you.

Another thing you could try is remove Bob's knobs and go back to the original scope setup. Then try and re-collimate.

Hope it works out for you...

All the best

Dave McD

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19 years 3 months ago #10697 by michaeloconnell
Replied by michaeloconnell on topic Re: Bobs Knobs for 10"LX/GPS
Seamus,
First and second thing: Don't panic. It can be rectified.

Firstly, lighten tighten all three bob's knobs screws so as to ensure the secondary mirror is secure and won't fall out. Needless to say, don't over tighten them either.

When looking into the eyepiece, note the direction the flare appears to point. If it goes from say 3 o'clock to 9 o'clock, look at your screws and see which one is at 3 o'clock or 9 o'clock. As there's only 3 screws arranges in a triangular manner, it should be easy decide which one to choose.

Now, unscrew this screw by 1/4 a turn and tighten the other 2 screws by 1/4 a turn, or as far as they can tighten (using gentle force obviously). Now take a look in the diagonal and see if there's any improvement. If not, repeat a few times.

Give this a try and report back on what happens. If it doesn't cause any form of improvement whatsoever or appears to amke it worse, let us know. You can use this then to actually do the complete opposite.

Let us know how you get on.

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19 years 3 months ago #10698 by michaeloconnell

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19 years 3 months ago #10699 by Dougal
Replied by Dougal on topic Re: Bobs Knobs for 10"LX/GPS
Thanks Michael.
The flare seems to be heading off at about 1 O'Clock - I'll try what you suggested if is clear tonight. I was hoping I wouldn't have to buy a collimating eyepiece, hope fully I'll get away with it.

The killing thing is, this scope was shipped from Irvine to Minneapolis and from there to me, and it never, ever had to be touched even after all that lugging around.

Anyway, hopefully with your and the rest of the group's help I can sort it out.

I've learned my lesson though.. If it's not broken don't fix it. :?

Seamus

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19 years 3 months ago #10706 by dave_lillis
Replied by dave_lillis on topic Re: Bobs Knobs for 10"LX/GPS
Hi Seamus,
I own a 12" LX200 and got the bobs knobs last year, I have to say I was skeptical about them but I was very impressed when I started using them, makes collimating much more convienent.
Can I ask, have you ever collimated the scope yourself before.
If this is your first time doing it, then there is no need to worry.

Collimating SCTs can be difficult and is best done on a star.
If its even slightly out, then comet images are the result.
Remember the primary mirror is a F2.!!

alternatively, but less likely,

You might have over tightened one of screws and distorted the secondary mirror, just make sure that none of them are tight, but not so loose that the mirror falls off. :shock:

Do let us know how you get on.

Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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