Author Topic: Reducing focal plane by moving primary mirror back?  (Read 195 times)

stancacoho

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Re: Reducing focal plane by moving primary mirror back?
« Reply #15 on: January 30, 2018, 09:50:37 AM »
If you can see the whole primary at once with your eye at the focal plane and about in the center of the eyepiece tube, you should be okay. You may have to re-collimate the scope also.

Lawrence Paez

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Re: Reducing focal plane by moving primary mirror back?
« Reply #16 on: February 02, 2018, 08:30:53 PM »
Ok cool thanks yeah it's all collimated I have glatter tools i actually have clear skies here tonight i actually secured the extension of the tube with two hose clamps chained together works really good won't budge lol

soecolerfe

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Re: Reducing focal plane by moving primary mirror back?
« Reply #17 on: February 02, 2018, 11:32:17 PM »
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Ok cool thanks i moved the primary Back 2 and 1/4 inches I couldn't see the whole primary in the secondary at the focal plane now I can so what I did was necessary right?

That means you stopped the scope down to a smaller diameter.
With your eye at the focal plane, you should see the entire primary and a little around the edges.
That is, you want the primary to fully illuminate the center of the field and about 1/4" on either side of it.
Another way to say that is that, with your eye at the focal plane, you should be able to move 1/4" each way from the center before you see the primary start to get cut off at the edge of the secondary.

ransgesislu

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Re: Reducing focal plane by moving primary mirror back?
« Reply #18 on: February 03, 2018, 02:22:49 AM »
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Ok cool thanks i moved the primary Back 2 and 1/4 inches I couldn't see the whole primary in the secondary at the focal plane now I can so what I did was necessary right?

If you are saying that previously you could not see the entire primary but after you moved the mirror back 2.25 inches you can, then yes, it was necessary.

This assumes you have the focused at the focal plane and that you are peeping through a pin hole. If the eye/head is free to move, the secondary still maybe too small.

Jon

tradunjuwa

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Re: Reducing focal plane by moving primary mirror back?
« Reply #19 on: February 09, 2018, 10:37:15 AM »
Yes i can see the primary completely at the focal plane with room to spare now