Dob view

[bosun21]

2 minutes ago, wookie1965 said:

Thank you for that I knew last night it still needed a tweak I will get the concentre on it later after my hospital appointment. 

Great idea as once you get the secondary correct and locked up tightly with the Concenter you can virtually forget about it. A tweak to the primary and you’re in business.

[John]

1 hour ago, wookie1965 said:

It was the washing line lol 

I've seen a similar effect caused by observing something that is not far from the edge of a roof or building as well. It's easy to loose track of your local issues when concentrating on the view through the eyepiece.

My experience of out of collimation newtonians is that the symptoms are a lack sharpness / resolution and contrast which are all improved when the collimation is more accurate.

I can't say that I have seen stars turned into streaks though collimation errors  

Edited September 6, 2023 by John

[wookie1965]

24 minutes ago, John said:

I've seen a similar effect caused by observing something that is not far from the edge of a roof or building as well. It's easy to loose track of your local issues when concentrating on the view through the eyepiece.

My experience of out of collimation newtonians is that the symptoms are a lack sharpness / resolution and contrast which are all improved when the collimation is more accurate.

I can't say that I have seen stars turned into streaks though collimation errors  

I checked the mirror clips undid the second one and saw a visible shimmer across the mirror so had tightened the mirror clips too much. 

[wookie1965]

Here Spile does this look better. 

[wookie1965]

Well I bought a laser collimator from moggi1965(Morris) to make collimation easier. 

Wondered why kept slipping back into the same place took the secondary off and low and behold three indents. 

So rubbed it down cut out a piece of milk carton and found a 1mm thick washer so now the three collimation bolts won't be digging in anymore and collimating the secondary was a breeze. 

Hopefully check it out again tonight. 

[Spile]

8 hours ago, wookie1965 said:

Here Spile does this look better. 

I will take look tomorrow but it would be a lot easier if placed a piece of paper behind the focuser so that I could see all the edge of the sight tube.

[wookie1965]

10 hours ago, Spile said:

I will take look tomorrow but it would be a lot easier if placed a piece of paper behind the focuser so that I could see all the edge of the sight tube.

I will take another picture with the yellow card in  for you and thank you really appreciate you taking the time to check it for me.

[Spile]

Correct the offset error by moving the secondary towards the primary so that a=b, getting rotation as good as you can. Then adjust tilt/rotation.

[wookie1965]

I have not touched the vanes at all just put yellow card in now and the secondary looks miles out. 

Going to strip it down this afternoon and start again.

Do you know what size bolt holds the secondary on please. 

[wookie1965]

Ok stripped down put back together looks better now laser dead center and collimation looks better. 

[Spile]

Here you go...

[wookie1965]

I had tweaked it after I took this picture when I tried the laser and it was slightly off. 

This is the result still think it's a tad out but not by much. 

[wookie1965]

Just gave it a tweak. 

[wookie1965]

And another tweak. 

[wookie1965]

Hopefully this time it's right. 

[Spile]

 

A little bit of tilt should do it.

[wookie1965]

7 hours ago, Spile said:

 

A little bit of tilt should do it.

Thanks Spile really appreciate that

 

[wookie1965]

Tweaked 

[Spile]

Its a lot better...

[wookie1965]

7 hours ago, Spile said:

Its a lot better...

Thank you really appreciate it, don't think I can get it much better than that looks nearly spot on. 

[dweller25]

On 09/09/2023 at 17:00, wookie1965 said:

Tweaked 

That looks spot on to me 👍

[Spile]

On 10/09/2023 at 13:44, Spile said:

Its a lot better...

I agree. I’d just check the primary with a cap to make sure it’s centred.

[bosun21]

Last couple of tweaks has sorted out your secondary mirror 👍. Make sure you nip up the secondary screws . Just double check with a cap that the primary doughnut is perfectly centered with the hole in the cap. Well done @wookie1965. Persistence does pay dividends.

[wookie1965]

9 hours ago, bosun21 said:

Last couple of tweaks has sorted out your secondary mirror 👍. Make sure you nip up the secondary screws . Just double check with a cap that the primary doughnut is perfectly centered with the hole in the cap. Well done @wookie1965. Persistence does pay dividends.

I have the donut dead center using the cap that was the easy part. 

As said hardest part was the secondary when first started it kept clicking back in position it was only when I took it off I found the three indents in the holder. 

After putting in the washer and the milk carton washer it was much easier. 

Thank you all for your help. 

Paul 

 

[Spile]

I am pleased that you have sorted your mirrors. I also found that loosening the whole secondary assembly allowed me to actually visualise the intended result.