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Hi,

I got a 130p and it never needed alignment.

I transported a Skywatcher 200P F5 over our marvellous pot-hole ridden roads and it needed to be adjusted as soon as I got it home!

I didn't have any fancy tools. Lacking this I pressed ahead with my little collimation cap. I followed what i thought were the instructions and started with the secondary. Since all the main circles looked concentric, but I couldn't see one of the clips at all, I tweaked a couple of the three screws in the secondary until I could see them all about the same. Then I adjusted the spider to line up with the very centre circle by twiddling the primary adjusters. After going the wrong way once, it was soon lined up.

I have attached a picture of what the result was. I am a bit concerned about the fact that the first black ring is offset when everything else is lined up. Also, I can't see the mirror holders at all with the focuser pulled back so that the drawtube is clear of the image. Is this normal?

I tried the scope out on a distant chimney (1/2 a mile or so) and it seemed sharp and clear, but I'm not sure if this was a good enough test. I could see the steel boltheads clearly enough. If it stays clear tonight I'll find out, but I'd rather it was right before then. rather stupidly, I didn't look at the same target before I started. If I could have seen an improvement, I guess I'd have my answers.

If what I've done is right, is visual collimation good enough, or do you really need a Cheshire?

post-33691-0-22330500-1390830643.jpg

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It's not all supposed to look concentric. See here: http://www.cloudynights.com/item.php?item_id=2677 So what've you drawn looks good.

Don't worry about the mirror clips. Here's the deal with the clips. If you can't see the mirror edge when your eye is one focal length from the primary then you might be losing a little light. No big deal. Likely it will be less than 5% and you'd never notice. If you can see the primary's edge at the 1 focal length distance then you pull back a bit and it disappears: doesn't matter. That's not the position at which you'll be observing from. To be fully accurate: remember that your eyepiece will be situated at a distance of eyepiece fl + telescope fl from the primary (assuming you have normally corrected vision).

The alignment that really matters for getting sharp views is the primary tilt and also the secondary tilt (but primary tilt matters more). Whether all of the primary is visible in the secondary will affect brightness, not sharpness. Don't get too fussed about the brightness. At lower powers the edges of the field aren't using all of the mirror anyway and I bet you've never noticed.

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As Umadog says that looks fine, the secondary in a 200p is offset slightly so it won't be exactly concentric

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Hello. I have collimated my DIY 8" f5.8 with a cap for years. I have recently bought a cheshire, and it makes a big different. A minimum error in the collimation and you will see it clearly. In fact, if I collimate with the tube vertical, it will not be perfectly collimated if tilted. I think this cannot be seen with a simple cap. Now I collimate the tube at 45º. To be honest, I have not seen a big difference at the eyepiece so probably a cap in enough for a relative slow tube. Regards

Javier

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Thanks folks.

Sorry i took so long to get back to you...I wasn't stargazing, that's for sure. It's been so flipping cloudy.

Hello. I have collimated my DIY 8" f5.8 with a cap for years. I have recently bought a cheshire, and it makes a big different. A minimum error in the collimation and you will see it clearly. In fact, if I collimate with the tube vertical, it will not be perfectly collimated if tilted. I think this cannot be seen with a simple cap. Now I collimate the tube at 45º. To be honest, I have not seen a big difference at the eyepiece so probably a cap in enough for a relative slow tube. Regards

Javier

Maybe i ought to consider it, then.

The main thing at the moment is that I don't seem to have messed things up. The other problem is that I can't get a few minutes of clear sky to find out!

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