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SW190MN collimation screws


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Hello everybody. HEELP!

I have never collimated a scope before. Is there anyone out there who can explain what all those screws does and how i use them if I need to adjust the secondary mirror on my 190maksutov newton?

I unscrewed the center cap on the front lens on my SW190 maksutov newton as i think I need to collimate the scope, and i found 5 screws under the cap. I also pushed my lasercollimator in to the focuser and found the red dot to be a bit missaligned. I found that stars are not pinpoint sharp out at the edges of the wiew when observing with the baader 8-24mm mark III-zoom eyepiece. It doesn`t do any difference in any of the 2-24 settings with the zoom, the stars looks a little like small comets to me. Also I do not own any other eyepiece to test with at the moment. Can this be related to the zoom eypiece or is it a result of missaligned-mirrors?

Then I tried to focus on a star and then unfocus a bit as the manual says and.. strange, as far as I understand the scope was well collimated when testing that way! So maybe the scope isn`t so badly out of align after all? But after all the stars isn`t perfect at the edges.

Gunnar

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Hi Gunnar

The screws for collimating are the three at 120°. The centre one holds the secondary in place, you don't want to be touching that one.

The 4th one is the locking screw. This needs to be slackened slightly about an 1/8" turn at a time until the collimating screws can be adjusted under tension. Once collimation is finished it's retightened.

Have you tried collimating with the focuser draw tube at different positions, with the OTA at different rotations etc. This can sometimes show up any slop in the focuser train. This is evident if the laser dot presents itself at different places on the laser face.

My MN190 shows about the same misalignment on my laser as yours, yet it is perfectly collimated. A star test is the real tester.

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Hi

Those 3 protuding screws are your collimation screws for the secondary, from looking at your pic, the secondary actually does look even tilted underneath the focuser properly, but it's hard to tell with the reflections.

This maybe of some help.

http://www.telescope.com/assets/product_files/instructions/29370_07-09.pdf

Nadeem.

Hi Nadeem!

Thanks! I googled for two hours last evening for the instrucion manual with out finding no such one. And now you saved me, just what I was looking for. I was missing that manual as Skywatcher din`t enclose any for this scope!

Looks like Skywatcher and Orion is exactly the same scope then, Isn`t it!

Thanks

Gunnar

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Hi Gunnar

The screws for collimating are the three at 120°. The centre one holds the secondary in place, you don't want to be touching that one.

The 4th one is the locking screw. This needs to be slackened slightly about an 1/8" turn at a time until the collimating screws can be adjusted under tension. Once collimation is finished it's retightened.

Have you tried collimating with the focuser draw tube at different positions, with the OTA at different rotations etc. This can sometimes show up any slop in the focuser train. This is evident if the laser dot presents itself at different places on the laser face.

My MN190 shows about the same misalignment on my laser as yours, yet it is perfectly collimated. A star test is the real tester.

Hi Tony!

That makes all clear for me about those screws, so that one is a locking screw!

Yes Tony. I have tried collimation with the traw tube in different positions and yes I have also noticed that the focuser does have a small amount of slop. But mostly the laser dot is precented (with about 3-5 milimeters variation) on about the same area each time on the laser face. I did the construction of the laser collimator by my self and turned it out from solid aluminum in my lathe while I was waiting for the scope to arrive! Of course I did adjust the laser too so i now the laser it self is well and perfectly collimated! :eek:

Last night I took the scope out again and did some more star tests (note! I have not yet touched any collimation screws since i got the scope deliveried by the FedEx courier) and the scope seems to be perfect collimated during star test. So if I adjust the laser to the centre now, will it do no good? Shall I ignore the laser misalignment you say and leve it as it is?

Gunnar

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Hi Gunnar

I thought I couldn't recognise the collimator, looks like a sweet piece of kit. I love to see the schematic for it.

If it was my scope I'd use it as it is for the time being. The star test is good so that's a positive result to begin with. Take some images of star fields and compare the extreme edge stars with the inner ones for similarities.

You may find after all that a tweak may be needed that will bring the laser dot central...or not. What you don't want to be doing is chasing the dot around. Hope that doesn't sound patronising.:eek:

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Hi Tony

Thanks, I will use the scope as it is to begin with. Soon it doesn`t get any dark here at night. I wont buy a camera for this scope until the dark nights returns in the end of august. So I have lots of time to figure out wich camera!! :eek: Might be a canon.

Gunnar

Edited by Gunnar
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