16 replies to this topic

[MichaelBrock]

I just received an Antares 1.6x Twist-lock 2" barlow.    However, neither my one 2" eyepiece or my 1.25"/2" adapter fits into it.   They go in about 1/2" and hit the grey plastic compression ring.  That ring is free-floating just under the twist-lock ring and even when the ring is tightened down, it moves freely.  It looks like screwing down the ring should force the split plastic ring inwards to hold the eyepiece in place but it is not making contact with it.   I emailed Antares customer support but I'm waiting to hear back from them.  Has anyone with this Antares barlow experienced this problem before?

 

I have attached an image showing the gray plastic ring in question.    I can't help but think I'm missing something.

 

 

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[junomike]

Try removing the plastic ring and gently spreading it apart.  It most likely has been over-compressed and lost it's ability to "spring back"

[MichaelBrock]

Try removing the plastic ring and gently spreading it apart.  It most likely has been over-compressed and lost it's ability to "spring back"

That was it!  I took out the plastic ring and heated it under hot water and gently spread it into a larger radius and that did it.  Because it wasn't "springing" against the sides it was able to slip down too far into the tube.  Working now.

 

thanks!

[junomike]

[John Huntley]

Glad you got the eyepiece to fit into the 1.6x barlow.

 

Reaching focus with the combo is the next challenge - the Antares 1.6x in the later forms does need a load of inwards focuser travel !

[MichaelBrock]

Glad you got the eyepiece to fit into the 1.6x barlow.

 

Reaching focus with the combo is the next challenge - the Antares 1.6x in the later forms does need a load of inwards focuser travel !

While researching it I did run into some reports that this was an issue. I posted here asking about how much inward focus was needed and got a few replies with some some rough numbers. I was still in the planning stages for my 10" dobsoninan at that point so I moved the focal plane out a bit.  We'll see if it's enough!

[25585]

Glad you got the eyepiece to fit into the 1.6x barlow.

 

Reaching focus with the combo is the next challenge - the Antares 1.6x in the later forms does need a load of inwards focuser travel !

Is that due to the twist lock's extra height do you think? 

Edited by 25585, 26 January 2021 - 12:12 PM.

[John Huntley]

Is that due to the twist lock's extra height do you think? 

I think that, and also that the optical element seems to have been moved a little further up inside the 2 inch chrome barrel to allow a 2 inch filter thread to be cut into the end of the barrel. The optical element of the Mk 1 Antares 1.6x barlow was very close the end of the barrel.

 

I guess Antares were reacting to two areas where it was felt that the original design could be improved, ie: moving from set screws to compression fit and including provision to fit 2 inch filters to the barlow but in their execution of those improvements, focal plane position seems to have been adversely affected, unless your focuser has lots and lots of inwards movement to spare.

 

It's frustrating really because the optical performance of the 1.6x unit is very good and it seems to work with hyper-wides like the Ethos very well.

 

But if you can't bring the thing to focus ......

 

If I came across one of the Mk 1 units I might be tempted. I don't use filters on the end of barlow lenses and I could replace the set screws with nylon ones.

Edited by John Huntley, 26 January 2021 - 06:14 PM.

[MichaelBrock]

Do you have a rough idea of how much inward focus is necessary?

 

I think that, and also that the optical element seems to have been moved a little further up inside the 2 inch chrome barrel to allow a 2 inch filter thread to be cut into the end of the barrel. The optical element of the Mk 1 Antares 1.6x barlow was very close the end of the barrel.

 

I guess Antares were reacting to two areas where it was felt that the original design could be improved, ie: moving from set screws to compression fit and including provision to fit 2 inch filters to the barlow but in their execution of those improvements, focal plane position seems to have been adversely affected, unless your focuser has lots and lots of inwards movement to spare.

 

It's frustrating really because the optical performance of the 1.6x unit is very good and it seems to work with hyper-wides like the Ethos very well.

 

But if you can't bring the thing to focus ......

 

If I came across one of the Mk 1 units I might be tempted. I don't use filters on the end of barlow lenses and I could replace the set screws with nylon ones.

 

[John Huntley]

Do you have a rough idea of how much inward focus is necessary?

I borrowed one of the latest Antares 1.6x barlows a few months ago to see if the slightly revised design would reach focus when used with my Ethos eyepieces in my 12 inch dobsonian. It did not. The focuser ran out of inwards travel but I didn't perform measurements. At a guess I'd estimate that the barlow requires around 40-45mm of inwards travel ?. That is roughly how much of the drawtube is extended when I am at focus with my 8mm Ethos with no barlow in place.

 

Sorry that I can't be more precise. This is the latest design that I tried:

 

Edited by John Huntley, 27 January 2021 - 05:13 AM.

[25585]

Visual Back?!  Mine is like this and has thumbscrews. 

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Edited by 25585, 27 January 2021 - 07:45 AM.

[junomike]

Not sure if the "Visual Back" was intentional or a communication error with the Manufacturer.

Either way, this Ad explains the difference uses and also states the required 55mm Back-focus.

[MichaelBrock]

Not sure if the "Visual Back" was intentional or a communication error with the Manufacturer.

Either way, this Ad explains the difference uses and also states the required 55mm Back-focus.

55mm is a lot.  Does anyone manufacture a focuser with that much travel?  It seems to accommodate the antares barlow I would need to plan things so that I need extensions to get most eyepieces into focus. 

[Echolight]

I thought it needed more inward travel? 
 

I guess the back focus number provided is for DSLR use, on a refractor with no diagonal maybe.

 

I was wanting to use one with a zoom on a C8. But I hate the idea of turning that focuser any more than I have to.

Edited by Echolight, 27 January 2021 - 10:11 AM.

[John Huntley]

Visual Back?!  Mine is like this and has thumbscrews. 

That was the first type that I owned, about 10 years ago. That type did come to focus in my scopes OK. The later designs need somewhat more inwards focuser travel, unfortunately.

 

I should have held onto my first one

[RickM.]

Visual Back?!  Mine is like this and has thumbscrews. 

That’s the version I have too.  I really like it.

Edited by RickM., 27 January 2021 - 10:35 AM.

[pal77]

Spreading out the plastic ring didn't work for me when I tried it years ago. I was so frustrated with my eyepieces not fitting into the twist lock that I removed the plastic ring and tapped two holes into the top and added thumbscrews.