Need help to reassemble Baader VIP barlow

[Chrb1985]

Hi guys!

Im unsure where this post belongs but I'll start her.

Im currently finishing my new setup and I took almost everything apart and cleans it and now I'm in the process of cleaning my ZWO RGB filters and my Baader VIP barlow. My problem is that I can remember Wich  order the lenses go.. I only took out one lens from one side (I think). But when I look in closely it seems like there is dust and or scratches one step further in.. so I guess I'll open it up tonight and clean again, but this I want to make sure that the order is right.

I can't seem to find any blueprints or info online on how to do this. And I'm unsure what that particular Barlow lens technology is called.. seems to me that there is 3 lenses. 2 of the are round/concave and the third I'm not sure of yet.

Pleas help me guys.

I also want to ask what is acceptable amount of dirt/dust and scratches on filters and Barlow. And how do I clean them and with what. Right now I have microfiber cloth, brush and different types of glasses cleaners/clots and some hand desinfection fluid. 85% alcohol.

Please help 

 

[Louis D]

Here's the only diagram I know of for a 3 element Barlow:

As far as dust and dirt, random specs of dust have practically no effect, so leave them be.  A deposited film of atmospheric grime can lead to decreased contrast.  Scratches near the center can be very detrimental, but there's really nothing you can do about them.  Simply moving a bright object like a star around the field until the spiking disappears or is minimized can mitigate the effects.  Microscratches across an entire lens from overzealous cleaning can also decrease contrast by scattering light.  Again, nothing can be done about them.

[Piero]

I took a couple of pictures of my VIP Barlow. Mine was heavily modified but the lens direction is the same of course.

Lens facing the eyepiece:

 

Lens facing the focuser:

 

In its original configuration the VIP Barlow is as follows:

- 1.25" to 2" reducer adapter

- 2x 15mm T2 spacers

- VIP element screwed onto a 1.25" nosepiece

- the 1.25" nosepiece

 

It's a great barlow. One of the very best.

[JeremyS]

There is a diagram here: https://www.firstlightoptics.com/barlow-eyepieces/baader-vip-modular-2x-barlow-lens-125-and-2.html

[Louis D]

Yep, there even appears to be a cross-section of the optical section labelled Barlow Element that might help with the original question:

[Chrb1985]

On 06/09/2023 at 23:42, Piero said:

I took a couple of pictures of my VIP Barlow. Mine was heavily modified but the lens direction is the same of course.

Lens facing the eyepiece:

 

Lens facing the focuser:

 

In its original configuration the VIP Barlow is as follows:

- 1.25" to 2" reducer adapter

- 2x 15mm T2 spacers

- VIP element screwed onto a 1.25" nosepiece

- the 1.25" nosepiece

 

It's a great barlow. One of the very best.

Hi! Thank you so very much for good pictures!

So from what I can see here the round side is face outward on both sides. Right? 

[Piero]

41 minutes ago, Chrb1985 said:

Hi! Thank you so very much for good pictures!

So from what I can see here the round side is face outward on both sides. Right? 

Hi,

The orientation of the VIP element cell is "up" (towards the eyepiece) where those two opposite circles are. See my first image. I would imagine you played with them to take the cell out from the 1.25" nosepiece.

Louis' diagram above ( https://stargazerslounge.com/topic/413443-need-help-to-reassemble-baader-vip-barlow/?do=findComment&comment=4411253 ) is very clear. 

 

Also, in that diagram, #29 is a ring which I did not include in my post above. That ring allows one to screw a 2" filter right at the bottom of the 2"-to-1.25" reducer. It works as 2" to T2 adapter.

 

Edited September 8, 2023 by Piero

[Piero]

I assume you did not take apart the VIP lens element from its cell, right? 🫣

Edited September 8, 2023 by Piero

[Chrb1985]

On 08/09/2023 at 13:10, Piero said:

I assume you did not take apart the VIP lens element from its cell, right? 🫣

I'm sad to say that yes I did. I don't know how. But some way it had gotten dust inside. But realise I should not have opened it up.. anyway. If you could check your VIP and see if the glass "bow" is pointing in or out? And please check both the eye side and the telescope side. It's hard to see in the images Wich way the lenses are mounted..

[Chrb1985]

Kinda feel this is right. The "telecentric focal extender". So that the two outer lenses are facing outwards like in this picture.

looks right? 

[Don Pensack]

That drawing is correct if the negative lens is flat on one side.

If it is bi-concave, it could be in either direction, though only one direction would be correct.

[Don Pensack]

I just looked at one, and it appears the outer surfaces are both concave, but the lens facing the eyepiece is more concave than the one facing away from the eyepiece.

I did not dismantle the lens assembly to see the orientation internally, however, if there is more than one lens.

[Piero]

8 hours ago, Chrb1985 said:

I'm sad to say that yes I did. I don't know how. But some way it had gotten dust inside. But realise I should not have opened it up.. anyway. If you could check your VIP and see if the glass "bow" is pointing in or out? And please check both the eye side and the telescope side. It's hard to see in the images Wich way the lenses are mounted..

 

5 hours ago, Don Pensack said:

I just looked at one, and it appears the outer surfaces are both concave, but the lens facing the eyepiece is more concave than the one facing away from the eyepiece.

I did not dismantle the lens assembly to see the orientation internally, however, if there is more than one lens.

I just checked mine and the lens facing the eyepiece seems more concave than the one facing the telescope as Don suggested.

I had to check this several times as it is not obvious. Both lenses are concave.

I have never dismantled the element of mine (and never will!), but I would imagine that some retaining rings are in place in the cell so that the combinations for assembly the lenses should be very few if not just one. 

 

Why don't you contact Baader to confirm the exact order?

[Chrb1985]

Hi again.

I'm not sure om making myself clear here. I don't have time tonight to open it up again. But my main problem is remembering if the concave side "the bowe" is pointing bow to the eye or bow away from the eye. And the same question for the other side.

In the image I attached both lenses are pointing bow to the eye and the other side of Barlow pointing bow to the telescope. 

Like this:

eye side (==) telescope side

if that made any sense...

I'm attaching some pictures of my Barlow and I hope it can help you guys understand me. I understand I'm real bad at explaining.

But the way it sits right now is at the eye side the bow is pointing away from the eye. And on the telescope side the bow is pointing to the telescope.

Like this:

Eye side )==) Telescope side.

Never ever thought I'd use ASCII to explain something in 2023 🤣😂

 

 

 

[Piero]

As far as I can tell, mine is

eyepiece = ).( = telescope.

 ")" , facing the eyepiece, seems more concave than "(" , facing the telescope.

[Chrb1985]

7 hours ago, Piero said:

As far as I can tell, mine is

eyepiece = ).( = telescope.

 ")" , facing the eyepiece, seems more concave than "(" , facing the telescope.

Okay thank you. But when you touch the lens. Is the concave going inwards in the Barlow. Or do the bulge. Go in towards the eye? In the drawing the bulge goes outwards on both side of the Barlow. Damn I wish I could make myself more clear..

[Piero]

They go inwards on both sides.

[Chrb1985]

4 hours ago, Piero said:

They go inwards on both sides.

Thank you so much buddy! Your a life saver!

[Mandy D]

@Chrb1985 Think about it like this: Concave is like a "cave": goes inwards. Now look at a magnifying glass: this converges light and brings it to a focus and it's two surfaces are convex (opposite of concave). The job of a barlow lens is to diverge the light rays to create a larger image, therefore you need the opposite situation of a magnifying glass, hence both outer surfaces must be concave.

[Chrb1985]

17 hours ago, Piero said:

They go inwards on both sides.

Thank you so much buddy! Your a life saver!

[Chrb1985]

So I guess that's it than. All clean and reassembled in the right order. Hope this turns out good. Fingers crossed. Thanx so much for the help!

[Piero]

15 minutes ago, Chrb1985 said:

So I guess that's it than. All clean and reassembled in the right order. Hope this turns out good. Fingers crossed. Thanx so much for the help!

 

@Don Pensack mentioned that If it is bi-concave, it could be in either direction, though only one direction would be correct.

I have no idea whether the VIP element cell accepts only one direction or both. It would be good to test your current assembly (e.g. in day and night time) to see whether the barlow works as expected.

[Louis D]

Luckily, with so few elements, the number of combinations to try to find the best correction isn't too vast.  Some combinations probably won't even allow the lenses to fit back into the holder with retaining rings.