Perfect collimation - concenter eyepiece

[lnlarxg]

Want to expose this tool called “concenter” that was introduced to me by @Captain Magenta.   It’s not talked about too much surprisingly, and I cannot find much info on this tool on the net.

Costs £70-ish posted from Germany’s TS-optics.  It is a transformative collimation tool that will get your mirrors about perfectly aligned, if you don’t want to spend £00+ on Howie Glatter or Catseye

Little under 2 years ago I was thrilled to get a 10” F4 Quattro CF reflector from a SGL member, I was very much into imaging already with my 130pds.

Then I hated my 10” Quattro ! I heard it is hard to collimating, but I had plenty of mirror fiddling experience with the 130pds and a big visual dob.   If it wasn’t for its dazzling good looks and girth, I would have sold it by now

Then I was lent the “concenter collimating 2’ eyepiece” to try out.  And immediately realised how bad my collimation was, the concenter revealed every fine-margin errors. That was exciting, with the errors visible, I can correct them.

Concenter is like a Cheshire, but with an acrylic plate at the bottom with concentric circle patterns.  

1st with the primary mirror covered up, i could accurately line up the secondary mirror to the focuser.  Uncovering the primary mirror,  the concentric circle patterns helped lining the primary to the secondary with ease.  And finally tweaking the primary, the centre mark of the primary mirror Is reflected back correctly to the secondary.    If you have seen how a Howie works, basically this tool attempts the same but instead of the convenience of having concentric circles projected onto the mirrors, you look through this tool to see the circles. 

i now love my light bucket photon eating 10” F4 Newtonian. 

think £70+ for this tool is a little expensive for what it is, but with so many DIY astronomers here with a 3D printer, you can fabricate this tool cheap and sell them 

 

Edited May 10, 2020 by lnlarxg

[Neil H]

You should do a video using it if you can looks a great tool

[Captain Scarlet]

3 hours ago, lnlarxg said:

a transformative collimation tool

yes that about describes it!

[alacant]

Hi and thanks for the report.

Is the acrylic with the rings transparent? Is there a 45° cutout a la Cheshire sight tube?

TIA

[RT65CB-SWL]

Can they be used with catadioptics as well?

It says on TS-Optics "...for Newtonian telescopes..."

[johninderby]

I’ve been recommending this tool to many on SGL for ages and consider it one of the best collimating tools. Simple concept but so effective and easy to use. Just circles on a clear piece of plastic really.

Best tool by far in setting up the secondary mirror. Found that using it to set up the secondary first I could set the primary mirror level,by using a small steel rule to make sure the collimation screws were all set the same and it would be very close to having the collimation spot on. Then just fine tune with the laser.

http://apm-telescopes-englisch.shopgate.com/search?s=concenter

 

Edited May 11, 2020 by johninderby

[lnlarxg]

13 hours ago, alacant said:

Hi and thanks for the report.

Is the acrylic with the rings transparent? Is there a 45° cutout a la Cheshire sight tube?

TIA

The acrylic is transparent. There isn’t a 45* cutout , the concept of the concenter tool bypasses the need of one.  But, there is a glow-in-the-dark version of concenter now

[lnlarxg]

13 hours ago, Philip R said:

Can they be used with catadioptics as well?

It says on TS-Optics "...for Newtonian telescopes..."

I won’t recommend it, same way I have never heard a Cheshire eyepiece used on a catadioptric 

[RT65CB-SWL]

9 minutes ago, lnlarxg said:

I won’t recommend it, same way I have never heard a Cheshire eyepiece used on a catadioptric 

Thank you for your reply and clarification. 
I will stick to my artificial star and/or laser.

[tanwir]

I have a question. Once the secondary mirror is centered, the outermost circle starts to skew.

 

If I adjust the outermost circle then the secondary mirror is skewed.

How can I keep everything around the concentric circles?

[AstroMuni]

15 minutes ago, tanwir said:

How can I keep everything around the concentric circles?

Could just mean that your scope has an offset. Several faster scopes exhibit such behavior.

[apaulo]

i found it very good for centering the secondary mirror , but i still use the cheshire and laser for the primary.  downside is its way overpriced about 50p worth of materials. 60 odd quid badly spent. ah well you live and learn. 

[bosun21]

On 10/05/2020 at 15:52, lnlarxg said:

Want to expose this tool called “concenter” that was introduced to me by @Captain Magenta.   It’s not talked about too much surprisingly, and I cannot find much info on this tool on the net.

Costs £70-ish posted from Germany’s TS-optics.  It is a transformative collimation tool that will get your mirrors about perfectly aligned, if you don’t want to spend £00+ on Howie Glatter or Catseye

Little under 2 years ago I was thrilled to get a 10” F4 Quattro CF reflector from a SGL member, I was very much into imaging already with my 130pds.

Then I hated my 10” Quattro ! I heard it is hard to collimating, but I had plenty of mirror fiddling experience with the 130pds and a big visual dob.   If it wasn’t for its dazzling good looks and girth, I would have sold it by now

Then I was lent the “concenter collimating 2’ eyepiece” to try out.  And immediately realised how bad my collimation was, the concenter revealed every fine-margin errors. That was exciting, with the errors visible, I can correct them.

Concenter is like a Cheshire, but with an acrylic plate at the bottom with concentric circle patterns.  

1st with the primary mirror covered up, i could accurately line up the secondary mirror to the focuser.  Uncovering the primary mirror,  the concentric circle patterns helped lining the primary to the secondary with ease.  And finally tweaking the primary, the centre mark of the primary mirror Is reflected back correctly to the secondary.    If you have seen how a Howie works, basically this tool attempts the same but instead of the convenience of having concentric circles projected onto the mirrors, you look through this tool to see the circles. 

i now love my light bucket photon eating 10” F4 Newtonian. 

think £70+ for this tool is a little expensive for what it is, but with so many DIY astronomers here with a 3D printer, you can fabricate this tool cheap and sell them 

 

I found that it is great for your secondary alignment only. I prefer using a cap/cheshire for my primary and finished with my Hotech laser.

[newbie alert]

Can it be used with a RC?

[tanwir]

58 minutes ago, bosun21 said:

I found that it is great for your secondary alignment only. I prefer using a cap/cheshire for my primary and finished with my Hotech laser.

Are you saying I use my first picture where the secondary is perfectly under the circle and then use other tools such as laser to adjust primary mirror?  

[Skyline]

I have been using the 2" version for years as a sight tube including on my quattro 150p.  I use a good quality Cheshire for primary alignment.

I think there is a 2" version now which the concentric rings now are glow in the dark?

[bosun21]

1 hour ago, tanwir said:

Are you saying I use my first picture where the secondary is perfectly under the circle and then use other tools such as laser to adjust primary mirror?  

In your top picture your secondary is out of alignment, in the bottom picture you appear to have corrected it and you should then use a Cheshire/laser to centre your primary donut. When my 8” dobsonian is collimated it is offset to a certain degree resembling your bottom photo.

[bosun21]

You said that your secondary is askew in your bottom photo! No it isn’t. What you are thinking is your secondary is actually the reflection of the centre of your con center. The large circle that you can see with the three mirror clips on it is your secondary showing the reflection of your primary. You should put a piece of colored paper behind your secondary and focuser as this will help sort out the reflections you are seeing.

[Spile]

The dark reflection 2 of the secondary should be offset.

[alacant]

15 hours ago, tanwir said:

How can I keep everything around the concentric circles?

Hi

One way would be to swap to a f8 or slower Newtonian. I'd guess the examples you posted are from a faster ratio.

To simplify the procedure, perhaps best to lose the concentre and use instead a Cheshire sight tube throughout. One with cross-hairs, even better.

Remember that apart from reflection, the secondary has no optical properties. It's just a flat piece of glass. Get it somewhere close. Then leave it. By far the most important alignment is that of the primary.

Be sure to read Telia's collimation myths and Seronik's no nonsense guide, both of whom outline the simplicity of a much misunderstood procedure.

Cheers 

Edited November 17, 2022 by alacant

[Mr Spock]

I use a concentre and a laser (perfectly collimated laser). This is with a 12" f5.

Step 1) Measure the secondary vanes to ensure the secondary holder is in the centre of the tube.

Step 2) use the concentre to align the secondary's position under the concentre only. Make sure you have something light under the secondary so you can see its outline clearly.

• Note: if you have measured your vanes correctly and you find your secondary consistently off to one side, you may need to collimate your focuser.

Step 3) use the laser to align the secondary with the primary by arranging the laser dot on the primary so it's in the centre of the doughnut (or whatever centre mark you have).

Step 4) align the primary with the laser in the usual way. Repeat this step before each session with the scope in place. Easier to do in the dark and from the bottom of a long tube with a laser.

Step 5) star test to fine tune the primary. I generally find when I use the first four steps the star test is spot on.

[Mr Spock]

A note about offset.

Unless you are making the secondary holder yourself it isn't something you should worry about. The manufacturer will already have taken this into account when designing the scope.

A little diagram to show what it is and why it's needed:

[tanwir]

Looks like it's getting better but secondary is still off a little.

[AstroMuni]

8 hours ago, Mr Spock said:

A little diagram to show what it is and why it's needed:

The picture explains it beautifully 👍🏾

[AstroMuni]

5 hours ago, tanwir said:

Looks like it's getting better but secondary is still off a little.

Do a star test and get the airy disk to tell you how good or bad your collimation is. Small alignment differences wont make much of an impact to your images anyway. BTW what scope do you have?

Edited November 17, 2022 by AstroMuni