2 " collimating cap

[ultramol]

Could anyone tell me if it would be better using a 2" collimating cap over  a 1.25" . My thinking being it would show more of the primary mirror or would I be wrong in thinking that?. The reason I ask is when I collimate with my 200p I can only just get the three mirror clips in view at the same time, just seeing the very edges of the clips...Regards..Geoff

[RichM63]

I use a 1.25" on my 200P.

If you can see the mirror clips at all you are doing well.

I can't see that a 2" cap would make any difference, you are after all only looking through a tiny hole in the center.

A cheshire type collimator would help.

Have a look at this guide, Astro Baby Guide to Collimation you will not go far wrong.

Cheers,

Rich

[NGC 1502]

Hi Geoff, yes, agree with Rich in post # 2.   As a collimating cap only has a tiny 2mm ( approx ) hole in the centre to look through, it would offer no advantage to have a 2" collimating cap.

Is your focuser racked fully out when using the collimating cap ?   That should allow you to see as much of the primary as poss, but if you can see all the mirror clips, you should be ok.

Regards, Ed.

[andyman]

I insert colli cap in to a low profile twist lock adapter which enables you to see the primary mirror clips easily

[bingevader]

The reason I ask is when I collimate with my 200p I can only just get the three mirror clips in view at the same time, just seeing the very edges of the clips...Regards..Geoff

Hopefully, that should be to your advantage. If you could see more of the clips or none whatsoever it would make collimation trickier. By only being able to see the same thickness of the edge of each clip, you know you have a pretty precise alignment.

[ultramol]

Thank you all for your help. It is much appreciated....Kindest regards....Geoff

By the way what is a low profile twist lock adapter ?

[andyman]

A twist lock adapter is a adapter that holds the eyepiece in place by twisting instead of having to fumble about with grub screws that is on a standard 2" to 1/14" adapter.it is supposed to centre the eyepiece better than a standard adapter...and with some being low profile when used with a colli cap the primary mirror clips become more visible

[ultramol]

Thanks again....Geoff

[Charic]

Could anyone tell me if it would be better using a 2" collimating cap over  a 1.25" . My thinking being it would show more of the primary mirror or would I be wrong in thinking that?. The reason I ask is when I collimate with my 200p I can only just get the three mirror clips in view at the same time, just seeing the very edges of the clips...Regards..Geoff

ultramol........As the folk above have already said, that's a perfect situation to have, just able to see the clips.  If you used your  2" eyepiece adaptor,  with  its cap drilled in the centre by 1-2 mm  it  should be possible to see more of the mirror clips if you searched for them and moved your eye about at a set distance from the cap, but the centre hole in either cap is purely just to align your eye (left or right) to the centre axis of the eyepiece, so its probably unlikely that a 2" would be of any benefit.  

Try fitting the 2" adaptor and punch a 1-2mm hole in its dust cap and see if it works. if there's no difference, just cover the peep hole with tape, or a rubber grommet!  If there is an improvement, maybe others will follow!

[ultramol]

Great help and advice as usual, thank you all for your help....Regards....Geoff

[Peter Drew]

The size of the secondary mirror or the distance of your eye from it determines how much of the primary mirror is seen reflected in the secondary.