Rate my collimation

[Kon]

I have a Skywatcher 200P Dob for just over a year and it had heald collimation from the factory very well, until my son kicked his soft ball at it. I noticed on a star test and Cheshire eyepiece that it was off. I have never done it and I followed astrobabys website. Pretty straight forward and it seemed my secondary was far more off than my primary. I used a Cheshire eyepiece with side view.

As a first attempt how does that look until the skies clear for a star test? I found it hard to hold my mobile square to the focuser but that's the view from the Cheshire eyepiece. Prior to collimation the primary mirror clip at 8oclock was hardly visible.

 

Edited January 10, 2022 by Kon

[PeterStudz]

I’m far from an expert but I have the same telescope and that looks like mine when it’s collimated. Although it can be hard to tell with camera angles like this. Proof will be in the observing.

As I you might know my 200p was kindly gifted to me, but it came without a base, which I’ve now constructed. There were other issues too which I’ve slowly dealt with. And I’ve had both mirrors out, bobs knobs & milk bottle mod added to the secondary.

Today I’ve taken the thing to bits in order, amongst other things, to flock the tube. At the moment it’s just a bare tube. I’ll try and do the flocking tomorrow- scary stuff! I just hope I can get it all back together!

[Kon]

Thanks @PeterStudz. I feel it looks similar to what I had before but good to get the thumbs up from others. Star test might be possible tomorrow night.

I love your base you made for your Dob, I have seen your thread. Scary staff to take the whole lot apart but I am sure it will be worth it.

What is the milk carton mod for the secondary, I am not sure I have heard it before.

[PeterStudz]

@Kon it’s been mentioned quite a bit on this forum in the past but was originally suggested by a guy on CloudyNights. Basically a couple of washers cut from a plastic milk carton and fitted under the secondary adjustment screws.

https://www.cloudynights.com/topic/446178-secondary-mirror-milk-jug-washers/?p=5775875#entry5775875

My understanding is that It’s supposed to make adjusting the secondary screws smoother and prevent the screws digging pits into the back of tree secondary holder over time. 

[Spile]

I see a little offset error a<b so secondary needs moving towards the primary. Followed by a tilt correction. As per https://astro.catshill.com/collimation-guide/

[Kon]

1 hour ago, Spile said:

see a little offset error a<b so secondary needs moving towards the primary. Followed by a tilt correction. As per https://astro.catshill.com/collimation-guide

I had another go this evening and I think it is better. I did a star test and all looks good, primary is tad off but I can live with it until seeing is more stable to correct.

Edited January 11, 2022 by Kon

[PeterStudz]

If at all possible I check collimation before every session. For me it’s the norm for the primary to require a little tweak before I take the telescope outside. It only takes a couple of minutes. 

[Spile]

I'd be very happy with that.

 

Edited January 13, 2022 by Spile

[Kon]

1 hour ago, Spile said:

I'd be very happy with that.

Thank you!! Star test last night looked great and  I also finalised my primary as well and it is dead centre as well.

I think I have a much better feeling/undertsanind over collimation now as a result of playing with my secondary's movements; I think beginners like myself should be advised to 'play' with the secondary so they can feel how everything moves. The primary adjustment was just a piece of cake as everybody else says.

In the end I got the FLO Premium Cheshire and it made huge difference not having the play in the focuser.

[Pitch Black Skies]

It looks like the secondary could move just a tad more towards the primary.

Other than that, it's an excellent job mate 👏

[Kon]

4 minutes ago, Pitch Black Skies said:

It looks like the secondary could move just a tad more towards the primary.

Other than that, it's an excellent job mate 👏

Thanks, it will be on my to-do list for the next cloudy night 

[Pitch Black Skies]

23 minutes ago, Kon said:

Thanks, it will be on my to-do list for the next cloudy night 

Won't be long 😄

I have that same Cheshire sightube you have. It's a great piece.

[Kon]

2 minutes ago, Pitch Black Skies said:

Won't be long 😄

Don't jinx it, last night was amazing seeing! 🍀🍀🍀🍀

Yes it made life a lot easier.

[Spile]

8 hours ago, Kon said:

Thank you!! Star test last night looked great and  I also finalised my primary as well and it is dead centre as well.

I think I have a much better feeling/undertsanind over collimation now as a result of playing with my secondary's movements; I think beginners like myself should be advised to 'play' with the secondary so they can feel how everything moves. The primary adjustment was just a piece of cake as everybody else says.

In the end I got the FLO Premium Cheshire and it made huge difference not having the play in the focuser.

I agree. Once you realise how the secondary moves it is so easy but takes so many words to explain. The cross hairs of the Cheshire eyepiece and sight tube combination tool make life so much easier.

[Spile]

8 hours ago, Pitch Black Skies said:

It looks like the secondary could move just a tad more towards the primary.

Other than that, it's an excellent job mate 👏

That red circle showing ideal placement in my post show the same but I would not worry about correcting it.

[Pitch Black Skies]

7 minutes ago, Spile said:

That red circle showing ideal placement in my post show the same but I would not worry about correcting it.

I'd correct it.

Just for peace of mind if anything 😄

[Spile]

23 hours ago, Pitch Black Skies said:

I'd correct it.

Just for peace of mind if anything 😄

Fair enough but it is well within the 6-8mm error tolerance for the secondary.