off-collimated

[Dom1961]

My scope seems to be producing some pretty decent images, but when I look through the collimation Cap it looks like this? When I measure the vanes they are all the same. Any ideas why?

[Gutross]

it looks like you need to adjust the primary mirror some. but i am by far no expert in this

[dweller25]

I suspect the rotation on your secondary is not right

[Laurie61]

As you can see all three mirror clips on the primary mirror I would think its the primary that's in need of tweaking.   

[faulksy]

As you can see all three mirror clips on the primary mirror I would think its the primary that's in need of tweaking.   

+1 primary is out, do you use just a colimation cap

[Dom1961]

No, I use a slightly off laser collimator( I'm in the process of searching for a mall enough Allen key to adjust it xD

[-Aldebaran-]

It does look a little of-set but it shouldn't affect the views all that much, I think some manufacturers have a design that requires a little off-set placement. How much have you used the scope since purchase, and have you already collimated it yourself?

[Dom1961]

I've used it loads, and I've collimated it a view times aswell

[dweller25]

Dom, can you take another photo down the drawtube with a bit more light, need to see if the secondaty is central to the drawtube....

[Dom1961]

How's that?

[Moonshane]

That helps. Agree that primary needs tweaking.

[dweller25]

How's that?

20150602_075653.jpg

Ah yes as others have said you need to tweak the primary to move the grey disk in the direction of the red arrow until the image of the paper circle on the primary is central....

so it ends up like this ......

[Dom1961]

Okay then, so the secondary isn't supposed to be off-set? AOL I managed to cellmate my laser, but when I rotate It in the actual focused it still moves?

[dweller25]

You have centered the secondary under the focuser so it's fine

[Dom1961]

I'll have to finish collimating tomorrow, going to A&E because I got plastic in my eye whilst trying to make my DIY collimation cap a bit bigger hole

[dweller25]

Oh dear

[faulksy]

Okay then, so the secondary isn't supposed to be off-set? AOL I managed to cellmate my laser, but when I rotate It in the actual focused it still moves?

that means its still not colimated or you are not clamping it each time you rotate it, best to colimate it on a v block over at least a 10 foot distance

I'll have to finish collimating tomorrow, going to A&E because I got plastic in my eye whilst trying to make my DIY collimation cap a bit bigger hole

hope your ok buddy ?

[Dom1961]

Yeah, they put dye in my eye so they can see if it's cut my eyeball but they couldn't see anything. I already collimator it on a v block and it seemed to stay still? I moved the secondary slightly to try to get the laser inside the circle and now it's miles off xD I'll try again tonight

[faulksy]

Yeah, they put dye in my eye so they can see if it's cut my eyeball but they couldn't see anything. I already collimator it on a v block and it seemed to stay still? I moved the secondary slightly to try to get the laser inside the circle and now it's miles off xD I'll try again tonight

at least your eye is ok

[coulthamst]

If I remember correctly,the secondary of a short F ratio 200mm reflector requires an offset due to the unequal focal lengths at the oposite sides of the light path due to the use of a 45 degree secondary of around 5mm for best results, and Skywatcher build the appropriate offset into their design as supplied. As you have measured the lengths of the vanes, all should be well. It certainly looks like the view down the 200mm flextube I used to own.

[Dom1961]

So it was fine when it was offset?

[Dom1961]

I have finally managed to align the secondary with the focuser again so that I can see the three mirror clips, but when I put the laser in, it doesnt hit the center circle, Is my collimator still out? I am collimating it over a 4.5 meter distance, Is that too short? I am seriously thinking of selling my laser and buy a cheshire as they seem a lot easier to use. How much would a laser sell for? It's a revelation one.

[BritAngler]

I only use a collimating cap and Cheshire eyepiece when sorting my 'scope and find it simple to do. Unfortunately a lot of people think that a laser collimator will be the bees' knees simply because it has the word 'laser' in it, but they often cause more problems than they solve. If your laser thing is perfectly collimated (4.5 meters should be fine for that), you can still use it for checking on any movement of the primary mirror when tightening up the locking screws.

[Dom1961]

The laser came with my scope when I bought it second hand, I've always thought whether or not to sell it to buy a cheshire. 

[coulthamst]

The acid test is star test on a mag 2 star at 200x or more on a night of good seeing. If the Airey rings are concentric, complete, and with no perceptible deformation etc both inside and outside of focus, the collimation is good. More information is available on several websited.