Having some collimation issues

[Dan13]

Hi everyone, my previous posts have been regarding some stars lifting to the left slightly in my images since obtaining my SW CC (non reducing) 

Had some really helpful feedback regarding sorting out any twisted veins and also drill tapping another screw hole on the main focus clamp for extra stability and also tightening up my focuser. These have all been carried out but havent imaged yet. One thing that's been bugging me is that I always rqd the 130pds is very good at holding collimation and that doesnt seem to be the case with me as it's out everytime I go to do a new imaging session.

I use a laser collimater normally but today while I have time I thought I'd have a look and see what's going on in there with the naked eye! It seems the secondary mirror wasnt aligned properly with the focuser and if I had my eye looking down I would see some of the edge of the focus tube to the right hand side, I'd loosen the mirror screen and put it so it's perfectly in line with no focus edge showing....great....I then as you can see from the pic attached the primary wasnt aligned properly and seemed off to the right so I played with that and got that bang in centre and though great everything looks good! 

I put my laser in just to check everything and as you can guess it's well out! So please can someone advise before tonight's session what I'm doing wrong, I'm guessing I'm right in saying I need no vision of the focuser in my line of sight while looking through ? If that's correct why does the laser not want this ? Is my laser out? 

 

Apologies first of all for wall of text and secondly for grammar...I am English so csnt blame it on that 🤣 I'm just terrible at it.

 

Many thanks 

 

Clear skies 

 

Edit...added pic 

Edited May 28, 2020 by Dan13

[Pixies]

Do you have a collimation cap? It's very hard to get a centered picture with a smartphone camera without one. Here's mine.

Also - have you seen Astro Baby's collimation guide?

[Dan13]

2 minutes ago, Pixies said:

Do you have a collimation cap? It's very hard to get a centered picture with a smartphone camera without one. Here's mine.

Also - have you seen Astro Baby's collimation guide?

Hi pixies, I dont have a cap no, just always used the laser and tbh other then the coma issue before buying the CC I've never had an issue with the centre stars. 

I've always collimated the same but this has puzzled me. 

I havent seen the guide I'll check that out now thank you 

[Ricochet]

If you look into the focuser with the open end of the tube on the left and the primary to the right, your secondsry mirror is way too high. You need a cheshire/sight tube to correct this and align it with the focuser, you can't do it with a laser. 

Once you have that step done you can align the secondary with the primary. Again the Cheshire/sight tube is the best option, but you can use your laser if you have accurately collimated your laser first. 

For the final step of aligning the primary use either a Cheshire or a barlowed laser. Don't use a laser by itself as any error in the previous step will result in double the error in this step. 

[Dan13]

59 minutes ago, Ricochet said:

If you look into the focuser with the open end of the tube on the left and the primary to the right, your secondsry mirror is way too high. You need a cheshire/sight tube to correct this and align it with the focuser, you can't do it with a laser. 

Once you have that step done you can align the secondary with the primary. Again the Cheshire/sight tube is the best option, but you can use your laser if you have accurately collimated your laser first. 

For the final step of aligning the primary use either a Cheshire or a barlowed laser. Don't use a laser by itself as any error in the previous step will result in double the error in this step. 

Oh ok thank you, and theres no way to do this without the Cheshire? I've never had an issue before I used the cc so would it had not been off before hand? 

 

Dan 

[Ricochet]

2 hours ago, Dan13 said:

Oh ok thank you, and theres no way to do this without the Cheshire? I've never had an issue before I used the cc so would it had not been off before hand? 

 

Dan 

Maybe you were lucky and it was pretty well centred under the focuser from the factory. All I can say is in that the photos you've uploaded it looks out now. 

If you don't already have a Cheshire an alternative that might be easier to use in a fast scope would be the Concenter . 

[Dan13]

6 hours ago, Ricochet said:

Maybe you were lucky and it was pretty well centred under the focuser from the factory. All I can say is in that the photos you've uploaded it looks out now. 

If you don't already have a Cheshire an alternative that might be easier to use in a fast scope would be the Concenter . 

Ok thank you. I'm out imaging now and all looks ok so I'll see what one looks like tomorrow. Its imaging in HA tonight and it's hard to tell the stars 

[JOC]

This is the Astrobaby guide http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/ the definitive work on the subject and with this and doing every single step, no matter how odd it sounded. even I succeeded.  It is worth noting that the final pictures of a well collimated scope are NOT perfectly central circles - a slight off-centered-ness might be seen.

[Dan13]

4 hours ago, JOC said:

This is the Astrobaby guide http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/ the definitive work on the subject and with this and doing every single step, no matter how odd it sounded. even I succeeded.  It is worth noting that the final pictures of a well collimated scope are NOT perfectly central circles - a slight off-centered-ness might be seen.

That seems to be what mine was like but I was overthinking! I havent processed my image yet from last night but everything looked great on screen. I think the focusser needed the tensioners tightened up.

Dan