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I can't adjust my secondary?

pipnina

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pipnina

pipnina

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After looking through my home-made (home made ≠ inaccurate, I did make it with construction lines and measured it after) collimating cap, I noticed the secondary mirror was not reflecting light into the ep correctly. By a fair margin I thought.

This is roughly what I saw: http://i.imgur.com/Kpp7NjB.jpgIt looks a lot like the image is reflecting to the EP's bottom left (hence the dark area in the secondaries top right).

So, naturally, I tried to adjust it. The secondary didn't have any screws so I tried alan keys. None of the alan keys I have will cause any change to the orientation of the secondary mirror, however. I'm wondering if there's something I forgot to do when i set the scope up for the first time or if something wasn't included...

Here's an image of the secondary support: http://i.imgur.com/58d1pDA.jpgIt looks like there are threads in the three empty adjustments. Should there have been screws there?

I'm not sure how much of an effect this slight mis-alignment is going to have on my so-so f/ratio scope (f/6.92~). But it's bugging me never the less!

Help greatly appreciated!

    ~pip

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pipnina

pipnina

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Looks to me like there should be 3 collimation screws in those 3 holes. Those would allow you to tilt the angle of the secondary mirror.

Yes I agree with John.

Usually there is three collimation screws, and the one in the centre. You are missing the three collimation screws.

Regards

Ant

Oh dear. Should these have arrived with the telescope (in say a plastic bag) or already in the screw holes? Will I be able to use any kind of screws? It's very odd to me that they aren't present...

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John

John

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They would have been already installed. Any kind of screw that will fit that thread should do. They need to be long enough to push against the secondary mirror holder so they can tilt it slightly in 3 diractions. The movement does not need to be a lot.

Don't unscrew that central bolt much by the way because your secondary holder and the secondary mirror will fall off and could get damaged or damage your primary mirror.

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NGC 1502

NGC 1502

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Hi Pip.

Image #1   the collimation may be good enough for a F6.9 scope, how are the views ?  You could try a out of focus star test at medium/high power - with the slightly out of focus star the rings should look concentric when in the centre of the field of view, and not skewed to one side.

Image #2  there may well be allen head screws deep within the 3 holes, have a close look. You will likely need to loosen the centre screw to release tension on the 3 adjusters.

But I'd try a the star test first before adjusting anything.

Good luck, Ed.

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pipnina

pipnina

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They would have been already installed. Any kind of screw that will fit that thread should do. They need to be long enough to push against the secondary mirror holder so they can tilt it slightly in 3 diractions. The movement does not need to be a lot.

Don't unscrew that central bolt much by the way because your secondary holder and the secondary mirror will fall off and could get damaged or damage your primary mirror.

I'll see if I have any screws of that size. But only if NGC 1502's suggestions don't work.

Hi Pip.

Image #1   the collimation may be good enough for a F6.9 scope, how are the views ?  You could try a out of focus star test at medium/high power - with the slightly out of focus star the rings should look concentric when in the centre of the field of view, and not skewed to one side.

Image #2  there may well be allen head screws deep within the 3 holes, have a close look. You will likely need to loosen the centre screw to release tension on the 3 adjusters.

But I'd try a the star test first before adjusting anything.

Good luck, Ed.

I thought the views were fairly sharp with the 25mm, less sharp with the 10mm and a blur with the 10mm+ barlow (but that did give me 180x mag, way too much, also the barlow is awful)

I will try a star test, then if I see it's not right I'll try and make some adjustments with the alan keys again after loosening the main screw (while the scope is pointed downward, of course). (although previously I haven't been able to make out the airy discs, but always worth a shot)

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pipnina

pipnina

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Ok, a bit of an issue here. My secondary's main screw seems to be glued in place. I tried turning it left (that's normally loose right) and it eventually caused my screwdriver to bend (It used to have interchangable screw heads, but now that one is stuck there forever).

Well, at least this means it won't get more out of alignment? :huh:

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NGC 1502

NGC 1502

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Ok, a bit of an issue here. My secondary's main screw seems to be glued in place. I tried turning it left (that's normally loose right) and it eventually caused my screwdriver to bend (It used to have interchangable screw heads, but now that one is stuck there forever).

Well, at least this means it won't get more out of alignment? :huh:

The centre screw needs to turn anti-clockwise to loosen.   Did you confirm that there are allen head screws deep within the 3 holes ?  Try loosening those (anti-clockwise) to relieve pressure on the centre screw.

That's if you are sure that collimation is actually necessary.

Hope you make progress, some Skywatcher screws are ridiculously tight.........

Good luck, Ed.

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VikkiFord

VikkiFord

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And Skywatcher metal is notoriously soft

I believe that metal is called cheesium.

As to adjustment. I read (and use this method) that you leave the centre bolt alone unless you are adjusting the rotation/height of the secondary and to adjust the mirror angle you would slightly slacken one grubscrew before tightening another. Which you would slacken and which you would tighten depends which way you want to adjust the secondary. If you just go straight into tightening one you are stressing the parts. I think that is in the manual come to think of it.

Think of it as being similar to adjusting the alt and azi bolts on an EQ mount where you slacken one slightly before tightening the other.

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Earl

Earl

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Its worth spending some time and making your secondary easy to adjust, Bobs Knobs, a washer for the bolts to go into with counter sunck holes and a teflon ring (or milk bottle top trimmed to fit.) between the washer and the mirror really make an improvements and dont cost the earth,

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Sirius Starwatcher

Sirius Starwatcher

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Its worth spending some time and making your secondary easy to adjust, Bobs Knobs, a washer for the bolts to go into with counter sunck holes and a teflon ring (or milk bottle top trimmed to fit.) between the washer and the mirror really make an improvements and dont cost the earth,

https://www.youtube.com/watch?v=MUE8fxqH3Qc

Good advice Earl I did this mod and it makes a really big difference

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