TS Optics 2" Concenter

[Barry-W-Fenner]

22 minutes ago, jetstream said:

If you look straight thru the focuser does the secondary look round Barry?

Yeah it does look round jetstream. To my eye anyway.

[jetstream]

Well then I'm puzzled too...

Never used a concenter but I know that the sight tube portion of the Cheshire combo tool works very well. Does it look ok with the cheshire?

Edited November 19, 2020 by jetstream

[johninderby]

Doesn’t matter what circle the secondary mirror matches up with. Move the focuser in or out so one of the circles matches.

 

Edited November 19, 2020 by johninderby

[Jiggy 67]

I know I said this earlier but the egg shape is down to tilt, the mirror is either tilted towards or away from the focuser. You need to rotate the mirror, either by hand or with the three tilt screws to make a perfect circle. You might find that you can centre it in the concentric circles then

Edit: sorry you’re saying the PRIMARY is egg shape.

Edited November 19, 2020 by Jiggy 67

[ian2]

The included instructions aren’t very clear, what I found helped me was to leave the mirror cover on (i have a flextube) and put card on the tube wall opposite the focuser until i got the secondary sorted out, and to use a torch to illuminate and make the rings easier to see. For the last step i use a collimation cap to line up the centre hole with the mirror 🍩 

[Ricochet]

On 18/11/2020 at 15:37, Barry-W-Fenner said:

Hi all.

Back again on this thread. I finally had chance to check the 300p through the concenter today. None of the circles on the concenter line up with the secondary. This is encouraging as my collimation can get better. However it dawned on me that i am not totally sure what circle should be lining up with the mirror. Just to be sure, should the secondary mirror be perfectly circular in the small central spot of the concenter. Or should you be lining up the outside of the mirror with the closest ring.

Sorry to ask again, I just want to be sure. I have currently left the scope in a semi collimated state until I confirm. See attached pic, a country mile off. The primary isa total egg shape. 😁

I don't think the primary is egg shaped. I think that there is some circular edge obscuring your view of the primary. 

Try waving your hand around inside the open section of tube to work out which side of the telescope the obstruction is on in reality (or get someone else to if you can't look through the concenter at the same time). Once you know that it might be easier to spot what is clipping the primary. I would also try looking through the focuser with no collimation tool and a Cheshire if you have one to determine if the clipping is still an issue and also to check whether the secondary looks central under the focuser with no took inserted. Possibly your eyepiece clamp is tilting the concenter and so you're adjusting the secondary to the "wrong" position as a consequence. 

[Greg Shaw]

Hi Guys

I have been following this thread for a while as I bought a concenter so that I could collimate my secondary after stripping the scope down for fitting a new focuser and flocking the tube.

This is what I observed and did to get a successful collimation. Hopefully this will help everyone.

Before reconnecting the secondary I made sure the focuser was collimated and made the required adjustments to the focuser collimation grub screws. I then attached the secondary and made sure it was central by measuring from the centre bolt out to the side of the scope.

Then I created a template out of card and clipped it to one of the spider vanes to block the primary mirror. (which isn't here but its still required to make the observing the secondary easier.) I also added a green card opposite the focuser to create a contrast from the white card.

To be able to see the rings in the concenter I attached a bright light to may chair and pointed it towards the top of the tube.

 

Because I had my focuser attached to a stepper motor I just moved the concenter out of the focuser so that I could get one of the circles close to the secondary.

 

 

This is what I observed. As you can see the tilt of the secondary looks good because it's a circle, but it needs to move towards the primary some more to hit the outer ring. I achieved this by holding the back of the secondary so not to tilt the secondary and then adjusted the central bolt.

 

Once I was happy with the position I adjusted the 3 adjustment screws to lock to hold everything in place. I have recently added bobs knobs this made it very easy because I could adjust whilst still looking through the concenter. As you can see the secondary is now a circle and one of the concenter circles goes all around the edge of the secondary.

 

I then connected the primary to the scope and checked with a cheshire, I needed to adjust the 3 adjustment bolts slightly to apply a very small amount of tilt to get the primary all in within the secondary. I then adjusted the primary to get the donut to match the cheshire cross hairs. Once this was complete I added the two templates again and rechecked the secondary with the concenter, to make sure it was still a circle and centered under the focuser.

So I learnt that the concenter is great for getting the secondary centred and round under the focuser. But still use a cheshire to apply the correct tilt to the secondary to get all of the primary in view and to adjust the primary to get the donut lined up correctly.

Edited November 20, 2020 by Greg Shaw

[Mark at Beaufort]

That is  very nicely done Greg. I particularly liked your primary mirror block with the attachment to the veins. I always push a white piece of paper down the tube - yours is a much better suggestion. I also agree its good to have a contrast colour card opposite the focuser.

[Barry-W-Fenner]

Hi all.

Thanks for all the input in this thread. With the pictures and info provided I have almost got the secondary mirror alined with the focuser. Just a few more small tweaks required to get the circle perfect. I'm not going to lie this stage has been a long, patient process for me. However once the full process is complete I will be confident of a perfect collimation.

My only slight concern is that I have had to tighten the secondary bolt almost to the maximum to bring the mirror to where I need it. Is that normal?

Another interesting point is I was initially struggling to get the secondary mirror and draw tube lined up. I ended up swapping the badder click lock and 2" extension over to the standard 1.25 adapter. This made things much easier..

Baz

 

On 19/11/2020 at 17:25, jetstream said:

If you look straight thru the focuser does the secondary look round Barry?

Yeah it does look round jetstream. To my eye anyway.

[Greg Shaw]

Hi Baz

When you are adjusting the secondary bolt have you loosened the three collimation grub screws as well?

Also, something to remember once you have the perfect circle of the secondary with the concenter and remove the paper blocking the primary it is likely not to look like a circle again. This is an optical illusion and is just telling you that the primary and secondary are not lined up. This is when the three collimation grub screws on the secondary come into play.

[Barry-W-Fenner]

1 hour ago, Greg Shaw said:

Hi Baz

When you are adjusting the secondary bolt have you loosened the three collimation grub screws as well?

Also, something to remember once you have the perfect circle of the secondary with the concenter and remove the paper blocking the primary it is likely not to look like a circle again. This is an optical illusion and is just telling you that the primary and secondary are not lined up. This is when the three collimation grub screws on the secondary come into play.

Hi Greg.

Thanks for the assistance.  So far I have been lining the secondary mirror up in the concenter circle with a combination of the holder bolt and the 3 adjustment screws. I am only a fraction off and aim to finish this stage later. However I am conserned that when I take the paper off the primary, the secondary will need tweaking to line up to the primary with the 3 screws and this will take my back off line with the draw tube??

Regards

Baz

 

[Greg Shaw]

Hi Baz

When I did mine I tried the approach of slacking the main centre screw and adjusting each of the three screws the same number of rotations so to push the secondary further down the scope in a straight line to align with the concenter. But in the end I found this not as easy because I was using bobs knobs rather than an allen key.

So I ended up slackening off the three screws and used the main centre screw to adjust the depth of the secondary. I controlled the tilt with my hand by holding the back of the secondary. Once I was happy I tightened the three screws to hold the secondary in place.

Dont worry about having to adjust the three screws to line up the primary it will be very slight. You should always go back and check the secondary once you have adjusted the primary. You might have to back and forward several times, each time making smaller and smaller adjustments.

This was what my secondary looked like just after the first adjustment in lining up the secondary to the focuser

This is what it looked like after I had made some adjustments to the secondary to get the primary aligned, as you can see its pretty much the same.

Just looking down the focus tube this is what you can see

 

This is what it looks like when using a collimation cap

This is what it looks like with a cheshire (hard to take this because the camera tries to focus on the wires in the cheshire)

 

 

 

 

[Jameslincs]

anyone have any thoughts on if this could be used for a Ritchey Chretien 8" telescope?

[Second Time Around]

I've just ordered another Concenter, this time a 1.25 inch one.  Carriage from Germany always seems to be astronomical (pun intended).  However by going direct to the makers,  Spheretec, I was charged only 10 Euros via UPS plus 69 Euros for the Concenter.  It was dispatched the next day.

To order from Spheretec email them at info@spheretec.de .

[Mark at Beaufort]

12 hours ago, Second Time Around said:

However by going direct to the makers,  Spheretec, I was charged only 10 Euros via UPS plus 69 Euros for the Concenter.  It was dispatched the next day.

To order from Spheretec email them at info@spheretec.de .

This type of collimator seems to be getting more popular. I wonder whether @FLOmight consider this product by going straight to the manufacturer?

[Corpze]

Not my intention to hi jack the thread, but I made a video on how I am using the concenter eyepiece, and also try to explain in PowerPoint how to move the secondary mirror in order to get it properly aligned.

Here is the video:

 

[CCD-Freak]

I was looking for a supplier for the TS Concenter tool in the US since the shipping from Europe was prohibitively expensive.  I was not having any luck so I was talking to a buddy of mine and he made me one to try out.  His uses a laser etched skylight filter and T-threaded extensions along with a nice compression holder for the "peep hole" which make it very flexible.   I have just started to experiment with it but it looks like it will work great for all my Newts and RCs.  He calls it the "SMAT"  (Secondary Mirror Alignment Tool) 🤪  

He made a few extra so if there is anyone on the US side of the "Pond" that wants one drop me a private message and I will get you hooked up with him.

Edited March 5, 2021 by CCD-Freak