focuser tube position when colimating?

[tingting44]

one thing ive never really been sure of and dont seem to be found any where i can find, is where are you suppose to put the focuser tube when colimating? by this i mean do you have the focuser all the way in/focused out to the middle or all the way out? as i have noticed you get some change in the tube depending where the focuser is?

[triton1]

I always have the focuser fully out.

[DrRobin]

You should try checking it with the focus tube all the way in, in the middle and fully out.  The collimation shouldn't change.  If it does, it means the focus tube is not correctly aligned, or possibly the secondary is misaligned. 

There will always be a slight difference due to slop in the focus mechanism and the better quality the less there will be.  I would suggest get it as good as you can across the whole of the range and then fine tune it for the normal position you use the most.

Robin

[tingting44]

thanks guys all taken in to consideration, where i have no mount for the time being might aswell give my scope some loving care

[RichM63]

No Mount !  Best of luck, just make sure it does not roll off the table. Why not also consider flocking if you can't use the scope at the moment.

As per the others, I'm a bit like that annoying dance at parties, you rack the focuser out, you rack the focuser in, in, out, in, out, it slops all about. Oh Skywatcher collimation........ 

Knees bent, back cricked, and start it all again.

Cheers,

Rich

[Moonshane]

generally when collimating I put as much as I can in the approximate position of use. e.g. I have the focuser where the bulk of my eyepieces focus and the scope at approximately 45 degrees. this mimics the conditions when in use and therefore you have a better chance of getting to a point where the scope works more effectively.

if there's a difference between collimation when the focuser is all the way in and all the way out then I'd think it's either slop in the focuser/drawtube, bending of the OTA wall itself or possibly a focuser that's a little off square.

if it's when you move the scope from vertical to horizontal, it could be these factors or your spider vanes might need tightening a little/primary cell needs adjustment in some way depending on design.

hope this helps.

[John]

I follow the same approach that Shane does - focuser in approx the position it's in during use.

[AlexB67]

If there is a quite a difference between eyepieces, for example my orthoscopic has a rather different focus position compared to the wider high power angle eyepieces, If I am going for planetary lunar detail for example with the ortho and I want to observe with the focuser in that position for a good while, I tend to check collimation in that position and tweak on the night once cooled.

Given a choice it is probably and arguably better to match collimation for highest power eyepiece that you'll end up using most, rather than low power if you happen to find there is quite a bit of slop and difference between focus postion of said eyepieces. It may just bag you that extra craterlet in a moment of good seeing, can't say that has actually happened mind you

[tingting44]

thanks guys think ill go with the approach of putting it in the position i use to colimate then, i dont really do any visual, all AP so i will get it close enough with my chesire then ill do a star test to get it bang on, all though ive never felt the need it needs doing with my 130-pds since i got it.

mhh flocking...... lol i have seen loads of topics about flocking but never read up on it, seems a bit scary lol

edit, thinking of getting these to keep me going till i get a mount again

http://www.microglobe.co.uk/pentax-10x50-pcf-wp-ii-water-proof-porro-prism-binocular-p-2603.html

[RichM63]

A decent pair of binoculars will become one of your best friends.

I cart mine all over the place, day and night.

And the kids will also be able to see through them.

How are you going to do a star test un mounted (serious question)?

Best,

Rich

[tingting44]

A decent pair of binoculars will become one of your best friends.

I cart mine all over the place, day and night.

And the kids will also be able to see through them.

How are you going to do a star test un mounted (serious question)?

Best,

Rich

yeah ive been wanting my own bino's for ages now, so thought why not get em now to keep me going till i can use my scope again

as for the star test i was going to put the scope on my shoulder and aim at a star while trying to adjust the primary...........................      ......................only kidding loooool, the star test will wait till i have got my lovely new HEQ5

[RichM63]

as for the star test i was going to put the scope on my shoulder and aim at a star while trying to adjust the primary........................... :color:

Yeah, that would work....

Snag is, I've never seen too many RPG7 scope alignement procedures.

LOL/

[laser_jock99]

The purpose of collimation is to align the optics to the axis of the focuser tube. In theory (assuming the focuser is linear) position shouldn't matter.

Since 'real life' mechanics don't live up expectations, collimate at your normal working distance to be safe.