This needs collimation, right?

[szymon]

After a quick google, it looks to me like these thumbscrews will be good:

http://www.wdsltd.co.uk/product/3403/thumb-screw-thermoplastic-with-steel-zinc-plated-screw-wds-8168

8168-227, M4 25mm long.  Any thoughts?

-simon

[Moonshane]

you are over thinking it   . basically the answer is yes but you look through eyepieces when you observe not a collimation tool. put the tool in the same way you'd put in an eyepiece, get the collimation about right and then enjoy the scope.

personally, I'd start from scratch as your secondary needs moving up the tube still based on your last pic. you cannot get the other things right until this is right. then adjust your secondary so the reflected donut is central to the fuzzy cross hairs, then get the black dot in the donut through the Cheshire. if you do these three things you won't be far wrong.

[szymon]

Sorry, to confirm by "up the tube" you mean further away from the primary, right?

Sent from my iPhone using Tapatalk

[Charic]

.......yes. Clock wise on the adjuster. You will have to relieve the adjusters first, by unscrewing them. Dont give up. your almost there. You just gotta get that secondary circle 'perfect' in the focuser tube. Eveything else will  come together.

[Moonshane]

Quite right Charic

up - away from primary

down - toward the primary down

collimation is one of those things that drives you mad at first but when it clicks you wonder how on earth you didn't understand it from the start.

Once your secondary is set you may (literally) never have to touch it again but do check it every now and again. Check the primary every time though it matters more

[RichM63]

For the secondary concentric circles as mentioned by Charic, you can download a nice little utility called AlsCollimation Aid. It allows you to overlay a series of accurate scaleable concentric circles over the image.

In my example, as the circles are concentric then any error will stand out,  The coloured card is placed opposite the focuser and also behind the spider to block out the primary.

This was what I used to correct my S/H 200P f5 when I first bought it.

hth

Rich

[Charic]

Good detail in that image, having a clear defined image to work with is a bonus. Quite often using a mobile, only the lens can see inside the focuser, and no light? Take Al's Aid now and place it over picture 05 Sep 11:04PM and the collimation appears closer ( my alignment not critical) but shows a little rotation in the secondary may be required?

[wookie1965]

Just used it on mine and it mine looks slightly wrong.

[Charic]

.......is your camera dead-on axis?  The outermost circular image outside Al's Aid  'frame' looks distorted. Who said any of this was simple, and remember, the link supplied by RichM63 is just an aid. 

[wookie1965]

.......is your camera dead-on axis?  

Took it with a mobile phone so that probably had something do with it.

[Moonshane]

How's the collimation going?

[szymon]

Well, I left it as it was for the time being because my days were full with work, and I wanted to get some astrophotography done during the clear nights ;-).  But I will probably get back to it on the weekend.  I am going to start again from scratch, and get this to the point at which I'm happy.  I then have the dob to do too!

[Moonshane]

As I say in my notes, first thing to do is 'nothing' as a check may reveal nothing to do.

[szymon]

Heh, indeed :-)

I'm pretty convinced though that, as per multiple comments here, the secondary mirror is a little further down the OTA than it should be.  I think starting again should help with that.

-simon

[Moonshane]

definitely.