3x Barlows - TeleVue and Explore Scientific

[Mr Spock]

TeleVue and Explore Scientific x3 Barlows. Has anyone used these or can compare the two? I can see the ES is a lot shorter, but more chunky than the TV; the ES has 4 elements, the TV 2. But are there any image quality differences?

[Don Pensack]

My use was on deep sky, not the Moon.  Some people who have used the ES on the Moon report some light scatter.  I did not see that because I did not use it on the Moon.

I thought stars were sharp in both.

The ES required some in travel at the focuser with a few eyepieces.  The TeleVue did not.  If you are near a focuser limit, that could matter.

I think the TeleVue is designed to be parfocal with eyepieces that have their focal planes slightly below the shoulder, like most TeleVue 1.25" eyepieces.

Mechanically, the ES is beefier and might do better with a very heavy eyepiece.  It's quite a bit heavier than the TeleVue, if that matters.

Note: the TeleVue is only available in a 1.25" size, while the ES is also available in a 2" size.

Also, 3X is a lot of magnification, and might result in having the magnification go too high for seeing conditions.  2X Barlows are more likely to be usable a higher % of the time.

In your scopes and with your eyepieces, a 2X would be more useful, though I wonder why a Barlow since you have eyepieces down to 2.5mm.

 

[Mr Spock]

Simple reason - I like to use my LVWs on the moon. With a x3 I can use the 22mm at x207, the 17mm at x268 and the 13mm at x351.

With a x2 I have to use the 8mm and there is too large a gap between the 8mm and 13mm - x380 and x234, with the 17mm at only x179.

The other night, in steady conditions, I was up around x397 with no loss of sharpness and picking up craters in the 1km - 1.5km size. It was usable at x447 too.

I have a Meade 140 Apo which measures at x2.35 (supposed to be x2) - which is where the x397 comes from (9mm ortho).

[Don Pensack]

Sounds like you could use a "kit" of Barlows: 2x, 2.5x, 3x, and maybe 4x?

[Ricochet]

I've got the old Meade version of the 2x ES. There are (were) reflections off the inside of the barrel between the two lens groups. This was solved by flocking between the two sections. 

[Mr Spock]

Simple solution for now. I experimented with the Meade, lifting the eyepiece out of the tube until I got x3 then measured the gap. I've found a short extension tube, £19.99 from Amazon, will provide the necessary extension to give exactly x3. Sorted for 20 quid 

[Louis D]

And that exact amount would be, what????  I get exactly 3x using the Meade 140 nose piece on my Arcturus binoviewer, so probably 100mm or so of separation.  By itself as originally packaged, I get 2.4x.  Both of these measurements were with a 14mm Pentax XL that focuses pretty close to its shoulder.

[Mr Spock]

Across a range of eyepieces I get an average of x2.35 with the Meade alone. Adding 45mm gets to x3 as measured.

[Mr Spock]

Here we go. Not the best images ever - hand held iPhone and a bit shaky...

22mm LVW on its own

22mm LVW plus Meade 140 plus 45mm

The top one measures 16.6mm, and the bottom 5.5mm, with a ratio of 3.02 

[Louis D]

Interesting.  I just measured the Meade 140 distance from the bottom of the chrome tube to its insertion shoulder and got 85mm.  Thus, if I'm seeing 3.0x in my binoviewer, and it takes an additional 45mm extension to get to 3.0x, my binoviewer must have a 130mm optical path length.  That's a 30mm longer than I had guessed, probably because I have to screw the nose piece into the BV's insertion barrel filter thread since it uses a nonstandard thread size to attach to the BV body.

[Mr Spock]

The other thing you'll notice with the Meade is there's no loss of sharpness or contrast. LVWs are already sharp to the edge and it continues with the Barlow. I wish they had made a larger range. I always wanted a 10mm...

[NGC 1502]

Vixen really should recommence production of the LVWs.  Unless I’ve missed something, Vixen have the SLVs, deservedly well thought of. But their premium range SSWs seem to have disappeared, and stopped at 14mm with nothing lower powered.

C’mon Vixen…we need more from you👍

[Ian McCallum]

Three Barlows, was the headline.  I thought it was something to do with Ken, Deidre and Tracey!🤣

[Louis D]

4 hours ago, Ian McCallum said:

Three Barlows, was the headline.  I thought it was something to do with Ken, Deidre and Tracey!🤣

Had to look that one up since that show hasn't made it to this side of the pond.  Good one. 👍

[NGC 1502]

36 minutes ago, Louis D said:

Had to look that one up since that show hasn't made it to this side of the pond.  Good one. 👍

 

Your’re not missing anything😁

[bosun21]

7 hours ago, Mr Spock said:

The other thing you'll notice with the Meade is there's no loss of sharpness or contrast. LVWs are already sharp to the edge and it continues with the Barlow. I wish they had made a larger range. I always wanted a 10mm...

I don’t know a lot about the Vixen LVW eyepieces other than them being a great eyepiece. There’s a set of six of them for sale on eBay which includes an 8mm and a 5mm .

[Mr Spock]

5 minutes ago, bosun21 said:

I don’t know a lot about the Vixen LVW eyepieces other than them being a great eyepiece. There’s a set of six of them for sale on eBay which includes an 8mm and a 5mm .

I have all but the 5mm and 3.5mm. Spending nearly £1k on a set just to get a 5mm isn't worth it 

[bosun21]

Yes it’s a pity that they are not being sold separately.

[Mr Spock]

Extension has arrived. Fast service from Amazon 👍 It's a Svbony 70mm extension tube - a bit misleading as 70mm is the length of the whole thing not the amount of extension. The top part measures at 40mm, the actual extension, which is what we are interested in.

So, when fitted into the Meade, it gives x2.95, which is good enough. This gives me: 22mm x204; 17mm x265; 13mm x345 - an ideal combination for the moon I think.

If I screw the Meade nosepiece directly into the Svbony, it measures at x2.18. Quite useful on it's own. The Svbony extension has a compression ring which the Meade doesn't, so, more eyepiece friendly.

[kirkster501]

I had the 2" X4 Powermate.  Lovely piece of kit but way too much for UK skies on a SCT and so I sold it.

[Mr Spock]

I've tried the combination. It works, but isn't without issues. Eye placement is a bit more sensitive than usual for an LVW - something they are really good at. Plus the whole assembly is a bit on the long side. 

Tonight on the moon I've been using my 8mm LVW at x190 and the 6mm SLV at x253. The latter showing the most detail.

I also used my 7mm Ortho (x217). Excellent image quality but the FOV is no good without tracking. When I get my EQ platform the othos will be contenders.

[Louis D]

Sounds like you need to find a used 5-8mm Speers-Waler Zoom (Varifocal).  It works quite well as long as you're okay with refocusing during focal length changes and can live with 10mm of usable eye relief; although it's much longer if you don't try to see the entire 78-80 degree AFOV field at once thanks to its 25mm diameter eye lens.

Edited March 15, 2022 by Louis D