Televue Plossls and safety undercuts.

[russ.will]

Now I've had a few sessions and a few cheap EPs, to try out in my binoviewer, I've worked out that my nose is a prominent limiting factor. BST Starguiders actually worked really nicely, but I couldn't get comfortable and the same goes for Vixen NPLs. However, the dual experience of the NPL and a revelation 20mm Plossl proved that the smaller EPs are just fine comfort wise and also, Plossls are less prone to kidney beaning during white light solar viewing.

So, I was pondering TV Plossls as a buy once and keep-em proposition - I may upgrade the BVs, but it would be unlikely the TV Plossls would move on as they'd also form the basis of a nice travel/family set.

However, the thing I noted with my Delos is that somebody really should drag Un Al screaming and kicking to the ES factory and show him a well designed safety undercut! Indeed as both of my mounts are Alt/Az I'd be perfectly happy with no undercut of any sort, as it makes squaring the EP in the holder (or a diagonal) much less of a faff.

Which brings me to my question - Does the barrel of a TV Plossl unscrew from the body (I imagine, yes) and if so, does it hold the lens elements in? Is the thread a standard 1.25" thread?

If the answer no it doesn't hold the elements and it's a 1.25" thread, then I may investigate replacing the barrel with 1.25" extension tubes. Who'll be brave enough to have a look for me? 

Russell

[michael.h.f.wilkinson]

Not sure about unscrewing barrels, but I got a 25mm Plossl which has a band of blue plastic/rubber material to fill up the undercut (which can be a bleedin pain)

[bingevader]

I have the 8mm, 11mm and 25mm TV plossls, and the silver barrel in all three does not contain any lens element.

However, the 25mm does have a matt black baffle.

They do all have a 6mm wide, 1mm deep grove in them, is it not to your liking?

[John]

The older "smooth side" TV plossls have no undercut. The more recent versions have one as Ben describes and some of the focal lengths made in the last couple of years have a taper to the lower part of the undercut to reduce the incidence of snagging on compression rings, as seen on the 32mm below. It's possible that eventually all the focal lengths will have this.

The barrel of the 32mm does hold the lenses in place but this does not seem to be the case for the other 1.25" focal lengths in the range, or at least not the examples that I have.  I don't have the 40mm so I can't see what happens there with regard to lenses.

In the case of the 40mm (from memory), 32mm and the 25mm the field stop is held within the chrome barrel wheras it's part of the lower lens retaining assembly with the other 1.25" focal lengths and stays in place when the chrome barrel is unscrewed.

The threading of the chrome barrels, where they screw onto the eyepiece body, does not appear to be 1.25", it's a little more. The other ends of the chrome barrels are threaded for 1.25" filters of course.

I have a feeling that some tape applied in the undercut section might be the most straightforward way to remove / reduce the undercut if it's an issue that you want to address.

[NGC 1502]

Regarding unscrewing the chrome barrel from Televue eyepieces - on some of them, the chrome barrel holds the lens elements in place, others can be unscrewed because the barrel does not retain the lenses in place.

The TV 32mm plossl and the 27mm Panoptic barrels do hold the lens elements in place.

The 24mm Pan barrel does not hold the elements in place, there's a separate internal retaining ring.

So tread very carefully, or you could hear a 'tinkle tinkle' as bits of expensive glass hit the floor......

Regards, Ed.

[Dude_with_the_tube]

put a piece of insulation tape around the undercut.Solves your issue cheap and easy.

[alan potts]

Oddly I find all my Televue eyepieces work superbly in my collection Televue diagonals and reducer, I have only one of the latter.  I also have 3 reducers that came with scopes and a WO diagonal combo and in agreement the same cannot be said, TV are a bit problematic. The one ExSc eyepiece I did test (4.7mm UWA) was horrible in the Televue reducer, clearly there is something in the design.

I also find the WO diagonal awful to use, the 2 inch sleeve fitting that goes into the scope is tapered and three of my scopes do not tighen onto it well enough, something that you cannot say about the TV's, they are a different class and price bracket for that matter but I wish now I had not tried to save money. Bear in mind two of those scopes have very high quality focusers.

I am happy to put up with the undercut problems as they shine in other areas, but if you are using all TV gear there is no problem..

Alan

[Roy Challen]

Just tried with the 15 and 20mm, you're safe with them too!

[John]

I ought to mention that my post above relates to the 32, 25, 20, 15, 11 and 8mm which are the focal lengths that I currently have in this range.

[ghostdance]

The 40 is the same as the 32 - the glass is held in by the barrel...

[russ.will]

This is good stuff. I don't foresee me buying anything higher than the 25mm - In fact initially, it will be a pair of 25 and a pair of 15mm. 

The 25mm baffle was unforeseen, but if it's not a 1.25" thread, it's irrelevant. I will look at the Michael/John/Dude solution.  

Russell

[Mark in Macc]

You could try taking the twist off eye cup from the NPLs to slim them down. I'm considering this with my NLVs.

[russ.will]

To be fair to the NPL, if it hadn't been too large, then I'd have sent it back on quality grounds. I don't think (from the dim memory of handling one) the NLVs share a lot with the NPLs other than the comapny 'look'.

The eye guard was so loose it was either down, or clicked fully up and wobbly, plus the plastic molding it was constructed from had some really rough edges. The inside of the body was shiny and so it lacked contrast, particularly in white light solar use. I'm not even sure the lenses were edge blackened.

It was sharp and reasonably well corrected - slightly sharper with less CA at the edges than the Revelation, but only just - but I would take the GSO/Rev every time, because the image just had more contrast pop and it's made of metal.

The funny thing is, I'm sitting here with the GSO/Rev right now and just noticed that it's undercut is neither one nor the other, just like the TV. But I've also just noticed it does one, rather interesting thing:

[alan potts]

Russell,

I firmly believe that if by the sounds of it you are going down the TV Plossl road you will not have quality issues with your purchases be it 20mm, 25mm or what ever. I only have two of the range, 11mm and 15mm and optically they are as good as my others, with very slight differences. My only minor issue was the rubber eyeguard which I can't get on with in the up mode, I have now folded them both down and I like them much more. I am thinking of adding the 8mm and 20mm, they are very nice planetary eyepieces for me and for the money great value.

Alan

[John]

I'd not go down the Tele Vue road again Russell. I honestly don't think the brand is really going to live up to your expecations. You can get GSO plossls for £30 a throw (thats GSO ones rather than the Revelations), their barrels can be reversed in the way you have above and their performance is very, very close I reckon. Save youself some £'s and frustration with TV's quirks perhaps

[russ.will]

Alan, I did think about the 11mm, but as the 15mm has 10mm of eye relief and I did get on the Nag Zoom with the same ER, I figured that was a safe place to start. 25mm was picked as it doesn't have too much ER and with the ES Focal Extender, gives a nice spread of 25, 15, 12,5 & 7.5mm in the frac when I'm away.

Russell

[russ.will]

I'd not go down the Tele Vue road again Russell. I honestly don't think the brand is really going to live up to your expecations. You can get GSO plossls for £30 a throw (thats GSO ones rather than the Revelations), their barrels can be reversed in the way you have above and their performance is very, very close I reckon. Save youself some £'s and frustration with TV's quirks perhaps

You're right, they're the panacea to all issues, and having had Delos, I'm well aware of where my expectations lie, or not. But, if there's one thing I've learned from my occasional TV sojourns, you don't loose a lot of money (if any) in trying.

Russell 

[russ.will]

I should have typed 'not' inbetween 'they're' and 'the'. My meaning got somewhat lost as a result.

No matter - I bagged the 15mm TV Plossl on Fleabay for £48 and have bought a new one to partner it. As I have a couple of 26mm somethings for the other end, I'll give the 15mm TVs a run out and see how I get on.

Russell

[russ.will]

Just a quick update.

I've been lucky enough to have a couple of days where I could use both of the scopes for white light solar and them leave them out into the evening for a a bit of more traditional astro, trying both bino and cyclops modes. Transparency wasn't great during the day and seeing somewhat variable at night, but you take what you can get and patience will deliver moments that exceed the average.

In terms of binoviewer and cyclops daytime use, the TV 15mm Plossls are the real deal. No kidney beaning and blackouts, an eye-cup that is just the right height to suit the eye relief whilst cutting out as much incidental light as could be expected. I would judge the effective eye relief to be a bit less than the 10mm quoted, as you really do have to 'get in there' to see the field stop. The Nagler Zoom had the same quoted eye relief and actually felt arms length by comparison. I also found in the BVs that the Plossl's eye-cup could be turned down on one side only, creating a pseudo winged eye-cup, that worked really well in helping to maintain a comfortably viewing position.

Removing the binoviewer (and it's aberrations) from the equation and treating the TV Plossl for what it is on it's own terms was interesting. On Jupiter, it was up against my ES100 14mm, which is about a diametric proposition as you can get in EP world. Both were in the LX200 at this point and with that being F10, anything going on is likely to be the EP.

In terms of on-axis sharpness, I would just, but only just, give the nod to the TV. It wasn't so much the detail in Jupiter itself, as the tightness of it's moons which, as seeing stabilized, just seemed to look that tiny bit rounder and less like points of light. This was impressive stuff from the ES, but I'll await a night of better seeing, where the Plossl should really stretch it's legs.

Contrast in the Plossl definitely had the edge, but again it was a small difference. Again I await that really clear night....

Off axis, well the ES100 is WAY beyond the field stop of the Plossl before it breaks down, so that comparison is somewhat specious, but I did notice a fair bit of pincushion distortion in the outer 5% of the TV Plossl FoV. It's sharp, but as Jupiter hit this point, it noticeably elongated. It stayed sharp, but definitely elongated.

I was actually checking to see what colour might appear at the field stop (basically none except where Jupiter was touching it) and also what sort of internal reflections there might be with a bright object just outside the field of view (basically none also), so I was a bit surprised to see this. I noted I was using the second hand example, so swapped it out for the brand new one and it was exactly the same. I've checked a few reviews and none seem to mention this which is odd, but I have to ask does it bother me?

No, because I want this for planets that will remain if not dead, then close to center of the field and stars, etc, don't really show this up. It's clearly very sharp, free of internal reflection, high contrast, plus it's comfortable enough in use to fit two either side of my nose. It's a very nice EP that I'm happy to own.

Happy enough that I've bagged a couple of 25mm examples too.

Russell

[alan potts]

Russell,

Nice report and as always very well written. Interesting about the eyecup on the TV Plossl, it shows how we are all different, I do not like them at all and fold them down, for me they get in the way on the 15mm and 11mm, the only two I have.

I don't know if you read it but a little while ago the TV Plossl 15mm was much better in my LX when compared to a 14mm Delos on Jupiter, strangely a few nights later the roles were reversed. They promise me a clear sky tonight but with the stream or lies I have had of late from the forecast I will not hold my breath.

I imagine that to get aberation free bino viewers you have to dig deep into the pocket but I am no expert having forgot to even buy a set after getting the eyepieces.

Look forward to the report on the 25mm Plossl's.

[russ.will]

What you say about the way one night suits things better than another, is very pertinent. Much as people like them, I can't really see the point in First Light reports, as not only is it unlikely viewing conditions will conincide perfectly with a new purchase, but I find it takes 10+ sessions before you get to know, never mind decide if you actually like a new toy.

I suppose that because of the dual solar/astro role both of my scopes enjoy, one can compress the timescale a bit, and because we are dealing with a Plossl here, there aren't exactly going to be too many surprises hiding up it's sleeve. Indeed, I have established that they do work better during the day than anything else I've got, so they're assured a home on that basis alone. Their astro chops will only be proven with extended (ab)use, but early impressions are that I don't have any nagging doubts in the way that I did with Delos.

Russell

[alan potts]

I did as i believe you read write a first light report on the Sumerian though I was cheating, it was two nights really. I agree with you on this point and it is why I spend so much time on eyepiece reviews or head to heads, always spending two nights on each target and many time three or four. Once not so long ago the seeing conditions around here were pretty much of a muchness at any given time of year, now they are very up and down.

But I fully understand the getting used to a scope part, I am still trying to work out which way to push or pull 90% of the time when nudging, more disappointing is the fact thai I get it wrong more than 50% of the time

Alan

[moriniboy]

This is how I get over the safety undercuts on my 32mm Plossls. My bino's use a compression ring which clamps on the collar of the undercut so it does not tighten well.

Using a couple of suitable o rings means that it clamps on the lower portion.

I'm quite happy that it clamps on a smaller area as its far more secure.