Collimation fustration!!!

[NIGHTBOY]

Right please clarify.....

Skyliner 200p. Cheshire collimation tube.

Centre screw - To get big black circle in the centre of collimation tube crosshair.

3 Allen head bolts - To get slightly smaller silver circle in the centre of collimation tube crosshair.

3 Screws at bottom of scope - To get tiny black dot in the centre of collimation tube in crosshair.

After I've got the first two perfect I go to adjust the tiny black dot by the bottom screws and it messes the other two up?!!

[wookie1965]

http://www.andysshotglass.com/Collimating.html

http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

http://www.schlatter.org/Dad/Astronomy/collimate.htm

Have a look at these this is how i learned to do it especially the last one.

[NIGHTBOY]

Yes now, even after following that video....

When I've used the centre screw to for the left/right adjustment of the first black circle and got it dead centre, I find that the 3 allen bolts that should be adjusting the second circle can pull the first one back off centre??

[NIGHTBOY]

This is as close as I can get it....

http://i118.photobucket.com/albums/o100/ddd_099/IMG_2116_zps989ea6a6.jpg

[bingevader]

You may need to go back and fore several times 'til things are spot on.

Did you check the 2ndary is central on the spider vanes too?

It can be very frustrating to begin with.

[saturn4me]

http://www.andysshotglass.com/Collimating.html

http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

http://www.schlatter.org/Dad/Astronomy/collimate.htm

Have a look at these this is how i learned to do it especially the last one.

Me too!

[wookie1965]

Yes it can be a bit fiddly the first time just take your time took me 3 hours and when you get it right you wont need to touch secondary again. Every time i tried to adjust the 3 collimation screws the mirror would twist i had to back the screws off then line the mirror up then one by one turn the screws in until they just touched then look in Cheshire to line up and hold mirror to stop it twisting while i adjusted tilt. In the end i borrowed a laser collimator to do this part which made it easier because i could line the laser up in the doughnut from the front.

[NIGHTBOY]

So how would you rate my pic?? Good/fair/bad??

[wookie1965]

So how would you rate my pic?? Good/fair/bad??

That does not look too bad at all best thing to do now is a star test only thing is you need a clear sky. By the way my sons a plasterer.

[NIGHTBOY]

[wookie1965]

I got the picture up second time like i said it doesnt look bad looks fine to me you need do a star test though.

[triton1]

I have had this with my 200p.My problem was resolved by dismantling the secondery mirror and using a polishing stone or emery cloth on a flat surface smooth the back of the mirror holder.You will notice there are score marks where the three Allen bolt have have been tightened against the holder.This means when you adjust for collimation it will jump back into the previous setting.After stoning the back of the holder I put a washer with three dimples(just spotted them through with a drill that fitted thru the Allen bolt holes and drilled about 1.5 mm deep)This will keep the Allen bolts in the same place and stop them scoring the back of the sec mirror holder,and to make things even sweeter place a washer made out of a plastic milk carton or Teflon between the washer and sec mirror holder.I,ve never had a problem since and collimater every time I use.Only takes a minute.Hope this helps

All the best Jonn.

[NIGHTBOY]

Ahh thanks Wookie. Yes I was just reading about that. So you put an eye piece in, centre a star then wind it out of focus and the shadow of the secondary should appear in the centre of the star???

The thought of trying to collimate outside in the dark terrifies me, its bad enough inside!!!

Also, is it always best to collimate when the scope is at outside temperature???

[wookie1965]

I collimated mine inside more than likely the secondary will be in the right place it will be the primary that will need tweaking which is very easy, once the secondary is in position dont touch it again as long as you dont bump the scope that will not move the primary will need tweaking from time to timehttp://starizona.com/acb/basics/using_startesting.aspx have a look at this.

[NIGHTBOY]

Funnily enough I was just reading that. So I'm looking for defined rings that stay the same wheather inside or outside the focus. Got it.

[NIGHTBOY]

Can I just ask what you do if the star test isn't a success??  Go back and re-collimate???

[wookie1965]

You can try and just tweak your primary just a bit shine a torch down it check, other than that yes recollimate  have you not got a astro society near you you could take your scope to there would be some one there who would have a look for you.

[NIGHTBOY]

Not that I know of...

[wookie1965]

http://www.astronomyclubs.co.uk/Clubs/Default.aspx?CountyId=55

Any of these close by.

[NIGHTBOY]

Ahh yes they are!! Many thanks!!!

Now surly this cant be far off perfect?!! I want to get this down to a fine art!! (hard taking a pic with my I phone)

[Carl Reade]

High heres a pic of mine what you should see with your eye also Astrobabys site has an excellent guide to do it.

Carl

[wookie1965]

Ahh yes they are!! Many thanks!!!

Now surly this cant be far off perfect?!! I want to get this down to a fine art!! (hard taking a pic with my I phone)

That looks near perfect apart from the mirror clamps you can usually see them if your focuser is right out try taking a picture with it in if your primary is held in with 3 clips you should be able see all 3.

[NIGHTBOY]

Now I am confused? That looks different and out of line to me??

[NIGHTBOY]

That looks near perfect apart from the mirror clamps you can usually see them if your focuser is right out try taking a picture with it in if your primary is held in with 3 clips you should be able see all 3.

2 secs...

[NIGHTBOY]

This is with the focuser wound right in....