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Very quick collimation question


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My scope is collimated (so do not panic;)) - When I put in my cheshire eyepiece do I tighten the thumbscrew? Doing this moves the alignment slightly.

I have assumed that I need to because I tighten it for an eyepiece, but I may be missing something:icon_scratch:

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I've collimated my telescope today (for the first time) and I tightened the thumbscrew too. Seems to make sense like you say, I do it with an EP.

Just did a quick star test too, and it looks like I've done it correctly...which is nice :)

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My scope is collimated (so do not panic;)) - When I put in my cheshire eyepiece do I tighten the thumbscrew? Doing this moves the alignment slightly.

I have assumed that I need to because I tighten it for an eyepiece, but I may be missing something:icon_scratch:

I thought the same when I collimated mine for first time. However, if you finish the collimation, then undo the thumbscrews, see if the eyepiece moving makes any difference. I found it to be very little difference.

I then went one further and moved the Cheshire eyepiece around to find what seemed to be the centre, tightened based on that position and then finished collimating.

In the end it didn't make a great deal of difference.

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i thought the same thing. i collimated so that it looked ok to me, but given that i don't really know what i'm doing, i always wonder whether "good enough for me" is really "good" or not? you know, could it be loads better?

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personally I agree with your logic in that you should generally collimate to match your normal observing circumstances. as such I tighten the thumbscrew and also have the adapter thumb positioned opposite the 2" thumb as I feel this has a better chance of centralising the eyepiece. I also tend to collimate with the scope at about 45 degrees; although make sure you always have control of the secondary if you do.

some imagers collimate every time they move to a new target as the mirror does move a little during observations, especially larger mirrors.

for visual though there's a little latitude with collimation and if you are a little off it's not too critical unless your scope is very fast. if you are well of you'll see it at the eyepiece and as you probably know, the primary adjustment has more effect upon the image than any other single component. thankfully this is also the easiest adjustment!

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...the primary adjustment has more effect upon the image than any other single component. thankfully this is also the easiest adjustment!

I collimated my dob with the help of my good lady wife. Usually this sort of thing leads to arguments as I can be really bad at explaining what I'm doing and how she can help. This time though we discussed collimating the telescope, and even drew pictures for each other on what we were seeing through the cheshire. The final stage of 'chasing the doughnut' turned out to be quite easy.

My wife rocks :)

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I thought the same when I collimated mine for first time. However, if you finish the collimation, then undo the thumbscrews, see if the eyepiece moving makes any difference. I found it to be very little difference.

I then went one further and moved the Cheshire eyepiece around to find what seemed to be the centre, tightened based on that position and then finished collimating.

In the end it didn't make a great deal of difference.

That's the genius of the Cheshire. Unlike a laser collimator, it loses very little accuracy through focuser slop. Tighten or don't tighten, it makes no real difference. With a laser, any small shift makes a big difference.

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