question on collimation on my SCT

[radioactive]

collimation of my C 11 SCT I would like to know two really can you as in is it okay to collimate it with a focal reducer 6.3 still being in line 2. Is their an optimal eyepiece value to use bearing in mind its Focal length 110" /aperture/ 11"/f10 if you get what I mean

[cygnusx1]

Honestly, my C9.25 was shipped half way rounf the world and I didn;t need to collimate it.

Unlike reflectors SCTs normally keep their collimation very well.

You sure it really needs it?

[radioactive]

Well Kev its a long story I have been getting on with finishing off the Obs including fitting another Losmund style bar to the C11 see picture I had clunked the scope a few times in the process also fitted the Antares 80mm last night I made sure everything all looked at the same area at the same time I did a good job on that the 80 the C11 the right angled finder and the Telrad all pointing pretty much spot on together well I thought being as It had been knocked about quite a bit in the process of being finished off painting roof knocking the mount several times with my head and so on and so forth during finishing the Build

So I decided to tweak the bobs knobs see if I could better the Collimation as it must have suffered well its suffered since I tried to better it will have another crack at it again tonight after I have read up on how to do it again :shock:

gunna post more pics of the build under a different post name

[Astroman]

It is not ok to collimate with a focal reducer inline. In fact, you should actually collimate without the diagonal as well, just to be sure. Do that, then insert other optical elements and recheck collimation. I once had my C8 diagonal knocked out of kilter and thought it was the scope until I checked.

[AstroTiger]

i hv been giving this some thought, since fitting the bobs knobs to my telescope, it is also out of collimation

but would a normal collimation laser not work as well for collimation. i mean surely as long as the beam is rtned to the central part of the collimation target then tht should be all?

Do we really need to use outfocussed stars?

if u do need an unfocussed star for collimation, how does one avoid the issue of ur hand getting in the way wen ur need to adjust the knobs?

AT

[radioactive]

i hv been giving this some thought, since fitting the bobs knobs to my telescope, it is also out of collimation

but would a normal collimation laser not work as well for collimation. i mean surely as long as the beam is rtned to the central part of the collimation target then tht should be all?

Do we really need to use outfocussed stars?

if u do need an unfocussed star for collimation, how does one avoid the issue of ur hand getting in the way wen ur need to adjust the knobs?

AT

yes you can only do it using a star to be correct have a look at this

http://legault.club.fr/collim.html

[radioactive]

then there is this one too

http://www.samirkharusi.net/collimation.html

[Astroman]

I actually use the interference shadow of my hand to determine which knob I need to turn.

[Kai]

I actually use the interference shadow of my hand to determine which knob I need to turn.

Same here

[radioactive]

I actually use the interference shadow of my hand to determine which knob I need to turn.

Same here

this is where you use your finger as a pointer to the crunched up area of the disk you are seeing and look at which screw is nearest to to where your finger is and tighten that one or is it the slack area you point to and turn that screw?

[Trevor]

I found this useful when collimating an SCT

Especially when using a CCD camera to collimate, always re-centre the image after making small adjustments.

Hope it helps.

Trev.

[radioactive]

Nice one Trev That's a great way of sorting out Collimation for imaging purposes

would those views be mirrored ones through the camera ?

or can this be the same for using the eyes?

[Trevor]

Martyn

That’s the visual one, the collimation screws are as seen from looking at the front of the scope, and the discs as seen through the eyepiece.

I will have to do one for the CCD if this rain ever stops.

[radioactive]

Martyn

Thats the visual one, the collimation screws are as seen from looking at the front of the scope, and the discs as seen through the eyepiece.

I will have to do one for the CCD if this rain ever stops.

Whoops sorry mate a case of engaging the fingers without assistance from the brain a common occurrence when you get like me still strong in the arm but weaker in the head Lol

that's great then I can use that to practice with only way to learn