Few questions about collimation.

[smulx]

Just wondering a couple of things before I order all my equipment. I was going to get a Cheshire, but I think I've changed my mind. The scope is quite big and there isn't anyone I could get to help me collimate it. Also, my area is light polluted so I'll want to travel to a darker site when I can, and I'm guessing a Cheshire is no good in the dark..

Firstly, does the SW Skyliner 250PX have a marking in the centre of the primary? I hope so, as I really don't want to have to take it out.

Unfortunately I can't stretch the budget to a HoTech, so it will have to be a Skywatcher or Baader. Due to their irregular shape, I'm not sure which one will be easiest to check the collimation of? I'm not worried about actually collimating it as FLO seem eager to replace any that aren't perfect upon delivery, which is good. So any recommendations? The Baader looks like it's better as it has a slightly more expensive look, but obviously that's not a good way to compare their functionality.

Last thing I need to know before I place my order. Hope someone can help!

[smulx]

oh, and do I still need a seperate collimation cap to line up the secondary?

[smulx]

and one more thing.... how well do lasers hold their collimation? Obvioiusly it's best to have one that I can recollimate myself if needed, without voiding the warranty.

[Moonshane]

a Cheshire is in my view BEST used in the dark. I actually prefer to collimate my primary with my red torch held at the 45 degree face and this gives a great red light to collimate with.

my scopes are 1600mm focal length and it's really a doddle to collimate (although easier as I have tool free collimation). it's a case of look at it, move a bit, look at it move a bit etc until correct. a tiny turn makes quite a big difference.

I prefer to do the secondary during the light as this won't be affected by cooling and scarcely needs to be touched anyway. I use a home made collimation cap.

lasers are good if barlowed. I got a revelation astro one from scopes n skies I think or telescope house which has little grub screws to collimate it - I don't this this is possible with baader but may be wrong.

[xboxdevil]

I'm pretty sure that you'll have the centre mark, I think it is standard now for skywatcher reflectors. Don't worry about collimating the scope in the dark or on your own with a cheshire, so long as you have a torch you will be fine. Generally you will only be tweaking the thumb screws on the primary, so a bit of trial an error and you will be fine.

For the few occasions that you need to adjust the secondary I'd recommend replacing the three allen key grub screws - I'm not sure if yours will be the same, but these fitted mine perfectly: 10 M4 X 25 FINE KNURL METAL THREAD THUMB SCREW KNOBS on eBay (end time 20-Oct-10 16:43:44 BST)

For the secondary it is easier using a collimating cap - I tried to use an old film canister cap, but I didn't get the hole quite central, so I redid one from a 4 pint milk bottle that works well enough.

[smulx]

Thanks for the advice. I just went with the Cheshire in the end.