how to know if SCT needs collimating?

[resonator77]

I have been bewildered with the question by looking at the planets and stars with my 8" SCT if it needs collimation or blame weather and seeing for bland views of celestial objects.

Can anyone advice as to how to find out if collimation is off?

So I ve read several posts on the net, and most of them offer star collimation.

Can it be collimated daytime? and what is the best way to check collimation?

Many Thanks in advance for any input and advice.

[barkis]

Collimating the SCT Telescope is not difficult, but have a look at this link, it will help I hope. Planetary detail will suffer if the scope is out of collimation, and near enough is hardly good enough either. It needs to be spot on, so persevere. Follow the advice carefully, it will make a lot of difference to you viewing.

Ron.

http://sctscopes.net/SCT_Tips/Maintenance/Collimation/collimation.html

[resonator77]

Barkis

is it good idea to invest in bob' knobs?

to find a tool that fits Meade SCT collimation screw is difficult:(

[barkis]

Bobs Knobs are pretty much essential for collimating, especially in the dark, where you would probably be putting the final touches to collimation by doing a star test. They are easy to get hold of in the fingers, wheras not only is an Allen Key awkward, it could result in scratching your corrector plate feeling for the socket in the screws.

They are not expensive, so buy them. You will be pleased you did.

When you get them, just remember to to fit them one at a time, otherwise, your secondary mirror could fall out.

Full instructions are supplied with them anyway.

Ron.

[skye at night]

Apparently Meade are bringing out a new SCT next year that will tell you when it is out of collimation...

Steve

[skye at night]

Oh! All Right.. i made that up.. but it sounds like the sort of thing they'd try to do!

Steve

[John]

Apparently Meade are bringing out a new SCT next year that will tell you when it is out of collimation...

Steve

Actuallly what it says is "it's not my fault, it's the lousy seeing conditions in this county ....... take me to Hawaii :("

John

[Sparrow]

I definately agree with the recommendation for Bob's Knobs - a well worth while investment and not really very expensive.

I perfected a daytime method of collimation which gave me excellent results:-

Get a bright LED torch (a small one will do - get some dark (preferably black) insulation tape and ***** a tiny pin-***** hole in it. Puit the tape over the LED lense - it should now just shine a very tiny pinpoint of light. This is where a reasobnabe amount of room is needed - put the scope as far away from the torch as possible (I had the torch at the far end of my living room which was darkened, and the scope at the opposite end of the conservatory) - enough to achieve focus anyway. You should now be able to look at what looks just like a bright star as you focus on the pin *****. Now all you need to do is follow the procedure for a star collimation but with the ease of being able to see what you're doing in daylight.

[red dwalf]

you can get a close collmination in daylight by doing this,

Stand in front of your scope about the same distance as the focal length of the scope with the scope facing you, now look in the center of the scope and you should see a number of rings, if the rings are more to one side or the other adjust them so they all line up and look on top of each other, this will only give you a rough collmination, after this you will need to tweek it with a star test to get it bang on.

[resonator77]

RED Dwarf, SParrow

thank you for very useful advice:)

one with LED bang on day time collimation procedure

[TheThing]

I***** a tiny pin-***** ... focus on the pin *****.

Don't you just love the rude word censor?

Seriously though, that's a pretty darned good idea! The thing about astronomy is that the simplest idea are often the best.

[resonator77]

can anyone advice as to how to find out if collimation is off?

[Merlin66]

The easiest way is to image either the artificial star ( or better a real star!) remove the diagonal and focus so you get a bright circle of light with a dark core. By moving the focus the diameter of this circle will expand and contract. The dark core should appear exactly in the centre. Try different eyepieces and different focus positions to confirm.

Collimating the SCT just brings this dark core to this centre position.

I find a webcam, set-up in the focuser gives the best results! You can see the bright circle on the screen and measure the position of the dark core in pixels from the edge to see what has to be moved where....

( Doing this with the diagonal in place may cause you to try and collimate any errors in the diagonal rather than the telescope!)

When you're finished you can replace the diagonal, keep your finger's crossed, and hope it still looks collimated...if not, you have a dud diagonal.

[red dwalf]

it`s easy to find out, just locate a bright star in the middle of the eyepiece, brighter the better, adjust the focus until it`s out off focus and the white disc gets bigger, then you will see and circle in the middle of the white disc, if it`s not smack in the middle of the big white disc it needs collminating.

[red dwalf]

merlin66 has explained it better.

[NickH]

Hotech laser after doing the star collimation will then enable you to return to precise collimation very quickly..

Great bit of kit

[resonator77]

Merlin, Red Dwarf, Nick

cheers for the info:icon_salut: