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2" or 1.25" TuBlug with Farpoint 2" laser?

Collimation
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#1 mnemonic

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Posted 25 January 2022 - 11:39 PM

I've searched the forum and it seems my Farpoint 2" laser won't work in a 2" Tublug due to length without using a 1.25-2" adapter, and even then I think only one of the two set screws would engage. So is there any downside to using a 1.25" TuBlug instead of adapting the laser to work with the larger TuBlug? All else being equal, buying the smaller TuBlug will save me a few $$.

 

Thanks for any advice. I seldom post but lurk here regularly and benefit immensely from the information exchange.

 

- Matty

 



#2 Starman1

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Posted 26 January 2022 - 12:21 AM

I've searched the forum and it seems my Farpoint 2" laser won't work in a 2" Tublug due to length without using a 1.25-2" adapter, and even then I think only one of the two set screws would engage. So is there any downside to using a 1.25" TuBlug instead of adapting the laser to work with the larger TuBlug? All else being equal, buying the smaller TuBlug will save me a few $$.

 

Thanks for any advice. I seldom post but lurk here regularly and benefit immensely from the information exchange.

 

- Matty

1) remove the aperture stop so the laser inserts farther (the aperture stop is not necessary in the Tublug).

2) Only one screw against the body of the laser is fine.  You don't need more.

 

A Farpoint Laser is compatible with the 2" Tublug.  The 1.25" Tublug will work fine, too.  Again, remove the aperture stop when using the Tublug.

 

The problem with using a 1.25" Tublug is the possibility of misregistration of the adapter or of the Tublug in the adapter.  For that reason, I advise the use of the Howie Glatter Parallizer if

a 1.25" tublug will be used in a 2" focuser.


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#3 sanbai

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Posted 26 January 2022 - 07:28 AM

For the Farpoint laser I went with the 1.25" tublug and the Parallizer. I can't tell the results because I don't have yet the dob, but it should work.

For the alignment of the secondary mirror you can use the laser directly in you focuser in 2" mode (with the aperture stop).

For the collimation of the primary you put the parallizer in your focuser, then the tublug, then the laser without the aperture stop.

For the primary the tublug should have the correct registration; that's ensured by the Parallizer. In that case, the registration of the laser in the tublug is not important. Removing the stop allows to have a brighter image and makes the laser fit better in the Parallizer (which is a bit short).

Parallizer + 1.25" is about the same price of the 2" tublug (IIRC), but you get something more compact and an adapter with zero out-travel. Also, you can collimate mini-dobs with 1.25" focusers.

Santiago

Edited by sanbai, 26 January 2022 - 07:28 AM.

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#4 CowTipton

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Posted 26 January 2022 - 10:18 AM

I use the Farpoint 1.25/2" laser with a 2" tublug.

 

As Don (Starman1) said just remove the little black aperture stop at the tip of the laser.  It unscrews easily.

One screw is fine for securing it in the Tublug.

 

You can also use an adapter if you wish but it's not necessary.



#5 Jon Isaacs

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Posted 26 January 2022 - 10:20 AM

1) remove the aperture stop so the laser inserts farther (the aperture stop is not necessary in the Tublug).

 

 

On the other hand, the Tublug works just fine with the aperture stop in place. It just needs to illuminate the center spot and a little more. The image is dimmer but that's about all. I have one of the older 2 inch Glatter collimators and the constant threading and unthreading of the aperture and stop and self Barlow wore out the threads so I need to be careful... 

 

I can attest to the fact that it works just fine with the 1mm aperture stop in place, even with scopes with focal lengths of 8ft and 10 feet.  If one is trying to collimate in broad daylight, then the brighter image would be handy.  My back up laser is an 20 plus year old Howie Glatter 1.25 inch.  Back then, the aperture stop was not removable. It works with the Tublug. 

 

As far as the 1.25 inch versus 2 inch Tublug.  I would go with the 2 inch, it's one less interface.  With the 1.25 inch Tublug, you have the adapter, then the Tublug, then the Collimator.  With the 2 inch Tublug, it fits directly in the focuser, it's a nice "slip fit".

 

I remove the bottom nylon set screw because the collimator in the Tublug is like a piston in cylinder, it builds up pressure if that bottom screw is in place.

 

Jon



#6 Starman1

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Posted 26 January 2022 - 10:30 AM

On the other hand, the Tublug works just fine with the aperture stop in place. It just needs to illuminate the center spot and a little more. The image is dimmer but that's about all. I have one of the older 2 inch Glatter collimators and the constant threading and unthreading of the aperture and stop and self Barlow wore out the threads so I need to be careful... 

 

I can attest to the fact that it works just fine with the 1mm aperture stop in place, even with scopes with focal lengths of 8ft and 10 feet.  If one is trying to collimate in broad daylight, then the brighter image would be handy.  My back up laser is an 20 plus year old Howie Glatter 1.25 inch.  Back then, the aperture stop was not removable. It works with the Tublug. 

 

As far as the 1.25 inch versus 2 inch Tublug.  I would go with the 2 inch, it's one less interface.  With the 1.25 inch Tublug, you have the adapter, then the Tublug, then the Collimator.  With the 2 inch Tublug, it fits directly in the focuser, it's a nice "slip fit".

 

I remove the bottom nylon set screw because the collimator in the Tublug is like a piston in cylinder, it builds up pressure if that bottom screw is in place.

 

Jon

That technique works with a 2" laser.  However, leaving the aperture stop in place on a 2"/1.25" dual-size laser results in a precarious amount of inserted 2" body into the 2" Tublug.

It works OK IF the aperture stop is removed.

I've suggested to Starlight Instruments that they lengthen the insertion tube on the 2" Tublug, but that was back when Wayne was there and John was still alive.  

 

Using a Parallizer eliminates any registration errors and also gives you a great 2" to 1.25" adapter as a bonus.


Edited by Starman1, 26 January 2022 - 10:31 AM.


#7 Jon Isaacs

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Posted 26 January 2022 - 10:54 AM

I've suggested to Starlight Instruments that they lengthen the insertion tube on the 2" Tublug, but that was back when Wayne was there and John was still alive.

 

In my mind, the tube needs to be as short as possible to eliminate the bending forces on the focuser applied by a relatively heavy 2 inch collimator.  It shouldn't be any longer than is absolutely necessary.  I think that's where it is right now, barely long enough for the 2 inch Howie Glatter. 

 

The 2 inch Tublug should not be compromised so that a 1.25 inch/2 inch Collimator can be used more easily.   It should be optimized for use with a 2 inch collimator and from my perspective, it is.  Howie did it right.

 

Jon



#8 Starman1

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Posted 26 January 2022 - 11:47 AM

In my mind, the tube needs to be as short as possible to eliminate the bending forces on the focuser applied by a relatively heavy 2 inch collimator.  It shouldn't be any longer than is absolutely necessary.  I think that's where it is right now, barely long enough for the 2 inch Howie Glatter. 

 

The 2 inch Tublug should not be compromised so that a 1.25 inch/2 inch Collimator can be used more easily.   It should be optimized for use with a 2 inch collimator and from my perspective, it is.  Howie did it right.

 

Jon

Jon,

I suggested they add 1/4".

In most of the recent 2" Tublugs, even the 2" doesn't insert all the way without pushing the blug forward.

That would happen if you left the aperture stop on, in your case.

Somewhere along the way, they shortened the top of the Tublug for no particular reason.


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#9 mnemonic

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Posted 26 January 2022 - 12:57 PM

Thanks to everyone for the discussion. I just ordered the 2" Tublug from Don's shop before it disappeared. I think it's the only place on the planet with one in stock.

 

- Matty


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