Collimation

[Adam J]

20 hours ago, Jazzo111 said:

Update.. tried a teleacope shop no joy and done my own research and found out secondary mirrors on fast telescopes are purposely off centre which makes things even more difficult

I did try a local astronomy centre phoned  no answer and only have meetings on certain days next one being late june.. any advise on how to focus a secondery mirror back in the exact spot? Putting in under the focuser is one thing but how do i work out the offset? 

Does a vt8 telescope have a slightly offset secondary mirror? I tried to email the manufacturer and didnt get a email back

If they could not help you colimate a dob then your local telescope shop is not actually a telescope shop....

Follow the astro baby guide.

 

[Jazzo111]

Some are with the cap with the hole in the middle and the chershire tube.. i turned the mirror towards the focuser...

Going  by the images i think the secondary may be off maybe needs turning more tawards the focuser 

[Jazzo111]

[Jazzo111]

[Jazzo111]

[Jazzo111]

[Jazzo111]

[Jazzo111]

Look ok guys?

[JOC]

@Jazzo111 have you looked at the pictures in Astro baby's guide yet - you should be able to compare then with what you are seeing.  As I mentioned above it is acceptable for one aspect to appear to be slightly off centre.  I would urge you to visit the web-site and scroll down to look at the pictures - you may find them remarkably similar to some of your own.

[Trikeflyer]

3 hours ago, Jazzo111 said:

You see the black rectangles in the picture of the mirror, they all need to be the same size. In your case the one is way bigger than the others meaning that the secondary is not centred on the primary. Thus needs fixing. You should try adjusting the three screws that alter the secondary and see if you can get the primary clips (the black rectangles) equal in size. Then work on the primary alignment. 

Hope that helps.

Steve. 

 

[Ricochet]

40 minutes ago, Trikeflyer said:

You see the black rectangles in the picture of the mirror, they all need to be the same size

I think you'll find the large one is the focuser. 

To the OP, follow the astro baby guide. It will show you how to block the reflection of the primary so that you can start by getting your secondary centred under the focuser and appearing circular. 

[Trikeflyer]

29 minutes ago, Ricochet said:

I think you'll find the large one is the focuser. 

To the OP, follow the astro baby guide. It will show you how to block the reflection of the primary so that you can start by getting your secondary centred under the focuser and appearing circular. 

Thanks for the correction. Sorry if I’ve thrown the op off track 🤐. Yes now I can see it. The secondary doesn’t look centred in the focuser. As you point out, it’d be easier to obscure primary to sort out secondary. 

Steve 

[wookie1965]

Put some coloured card in the tube opposite the focuser. have another piece folded in half making a L shape a different colour  put this in front of your secondary mirror, so it blocks the primary mirror reflection off.  Once you have done this you will be able to centre the secondary correctly under the focuser so it is as round as you can and the space around it is even. 

You may have to tighten the centre screw so the secondary moves into the tube or unscrew it to gain the desired space around the secondary mirror. Lightly do the 3 collimation screws up to hold the secondary in place. 

Take the L shaped card out use the 3 collimation screws to see the mirror clips evenly remember to back one off and tighten a different one to get the desired result. Then you can go to the primary tweak that then remove coloured card from opposite the focuser job done. 

[Jazzo111]

1 hour ago, Trikeflyer said:

You see the black rectangles in the picture of the mirror, they all need to be the same size. In your case the one is way bigger than the others meaning that the secondary is not centred on the primary. Thus needs fixing. You should try adjusting the three screws that alter the secondary and see if you can get the primary clips (the black rectangles) equal in size. Then work on the primary alignment. 

Hope that helps.

Steve. 

 

I tbought that black regtable was the focus tube meaning it would be bigger.. i seem to be making it worse now

[Trikeflyer]

Just now, Jazzo111 said:

I tbought that black regtable was the focus tube meaning it would be bigger.. i seem to be making it worse now

See the posts after this one. Apologies if I’ve sent you off Track. 😬

[cletrac1922]

I use laser collimator 

Have on lowest power setting

Align secondary, so on dot, middle of the primary, then adjust primary

Takes a couple of minutes

I am out couple of times per month, with my club, doing school/scout group presentation, as well as monthly club meet

Very rarely need to touch collimation

If only using Dob at home, then never be a need to touch, unless you bang the Dob against door or something else

Pic taken at a recent public viewing night

John

 

[Jazzo111]

[Jazzo111]

3 minutes ago, Jazzo111 said:

Moved secondary still messed it up even used card to block the reflection 

[Jazzo111]

3 hours ago, Trikeflyer said:

You see the black rectangles in the picture of the mirror, they all need to be the same size. In your case the one is way bigger than the others meaning that the secondary is not centred on the primary. Thus needs fixing. You should try adjusting the three screws that alter the secondary and see if you can get the primary clips (the black rectangles) equal in size. Then work on the primary alignment. 

Hope that helps.

Steve. 

 

I tbought that black regtable was the focus tube meaning it would be bigger.. i seem to be making it worse now

[Jazzo111]

Right i have made it way worse i cant do it cant centre the mirror cant even colimate the secondary to face the primary cause its so far off.. may have to sell it i cant do it, anyone interested in a dob?

[Geoff Barnes]

On ‎29‎/‎05‎/‎2019 at 05:37, Jazzo111 said:

I did try a local astronomy centre phoned  no answer and only have meetings on certain days next one being late june.

The way things are going Jazzo I think this may well be your best option, if you can wait 4 more weeks, they will almost certainly be able to get it sorted for you in no time.

[Jazzo111]

1 minute ago, Geoff Barnes said:

The way things are going Jazzo I think this may well be your best option, if you can wait 4 more weeks, they will almost certainly be able to get it sorted for you in no time.

Thats if i dont smash it through the floor before then... my celestron xtl 150 is simple no issue at all.. 

[wookie1965]

First time I did I was crying in anger it took me a solid day and a half trying get it right. It took me that long but once I got it right it was so easy after.

[Adam J]

1 hour ago, Jazzo111 said:

Thats if i dont smash it through the floor before then... my celestron xtl 150 is simple no issue at all.. 

Once you have done it once you will find it only takes 5 mins for ever after.

Someone close to you should be able to help. What part of the country are you in?

[Jazzo111]

3 minutes ago, Adam J said:

Once you have done it once you will find it only takes 5 mins for ever after.

Someone close to you should be able to help. What part of the country are you in?

South wales swansea.. if anyone can look at it that will be great i am considering selling it and buying another one that doesnt have a secondary mirror issue, Seems the only way at the moment. I can collimate mine easily... its this xt8 i just cant align the secondary in the right position in this focuser