TeleVue Plossls

[DRT]

Last night I spent an hour trying out my recently acquired collection of TV Plossls and Barlows in my CPC1100. I did this immediately after comparing my Ethos 13mm, T4 Nag 12mm and T6 Nag 13mm and used the same targets, M57 and M92, to give a fair comparison. Unfortunately, I didn't take detailed notes whilst doing this and it was more a case of pointing the scope and then going through the EPs in descending FL order to see how they performed relative to one another. Here are some observations from memory...

The 40mm gave a very washed-out view of the sky in comparison to the higher powered EPs I had been using for a couple of hours before popping it in the focuser. It was also significantly more washed out than the 32mm. However, the thing I found most frustrating with the 40mm was that it is not parafocal with its siblings so you have to mess around with the focus each time you put it in. It also has significantly more eye relief than the others so positioning the eye can be quite difficult and if there had been any local light sources around it might have been more or less unusable without an additional eyeguard.

The 32mm was a joy to use. It gave a nice level of contrast and the same FOV as the 40mm. The Ring Nebula was absolutely stunning through this EP - very vivid blue and beautifully framed against a backdrop of tiny bright stars.

The 25mm, 20mm, and 15mm all gave excellent views of M92 and showed almost as much detail and contrast as the Ethos and Naglers I had been using earlier. If you can give up the FOV and a bit of magnification these could save you hundreds of pounds!

The 11mm and 8mm were getting into territory where they were struggling due to excessive magnification for the sky and targets I was looking at. They were useable and I am sure if I hadn't looked through anything else would have seemed very good but they lacked sharpness in this set-up.

I then went through all of the Plossls again with the 2x and then 3x Barlows. Magnification became a real problem and the 3x was completely unuseable in this scope. With the 2x the 40mm was very challenging as it was now even more difficult to position the eye correctly. The 25mm to 8mm were unuseable due to high magnification. Only the 32mm gave a clear image, but that was almost identical to the view obtained by the 15mm on its own. The conclusion is that the Barlows are a waste of time and money with a scope of this focal length (2800mm).

I will be trying all of these again in my other scopes when time and skies permit. On this showing I am delighted to own the 32mm, 25mm, 20mm and 15mm. The jury is out on the others but they might come into their own in a different device.

Below is the relevant data from TeleVue's Eyepiece Calculator:

[ronin]

A barlow on something like a CPC is pretty redundant, an 8mm TV will give 350x and that is easily enough for just about anything sensible and even non-sensible.

The TV Plossl's are good eyepieces, they rarely get mentioned these days I think because TV raised the price in one "big" jump and people hesitated and also the BST's and X-Cels appeared on the scene at about that time.

[DRT]

I agree about the Barlows, Ronin, and only really put them in becasue they are in my case. I bought them to use with a short f/l travel scope.

I owned an entire set of X-Cel LX's and wish I had held onto some of them to do a direct comparison with the TV Plossls. Both styles are about the same price on the second-hand market, which is where I picked up all but two of mine. It might just be the green and balck fever that I suffer from but I think the Plossls give a sharper image than the X-Cel's.

[YKSE]

TV plossls are excellent eyepieces, but they don't barlow well as I understand it, the vignetting will be noticeable in the edge, independant of focal length. A better alternative will be powermate of tele-extender if you want to keep better eye-relief for short-focal TV plossls.

[John]

Interesting report. They are excellent eyepieces and do provide top class performance within the constraints of the plossl design. When I had a set of the TV plossls I also bought the 40mm for completeness but, like yourself, found the lack of par focality with the others in the range annoying and the low power did lead to a brighter background skies and a more washed out view. If you own the 32mm you don't need the 40mm. To be fair to Tele Vue they do state that the 40mm is not par focal in their eyepiece specs section - I just didn't take that in when I was researching them !

[JED-E3]

It will be interesting to hear how they compare on planetary views, I recently found that a humble Meade plossl out performed BST and ES uwa eyepieces on saturn in my 5" f/9 refractor, the view had better contrast control and cloud banding was visible in the plossl and not in any of my other eyepieces.

James.

[jabeoo1]

Good report.  I love them (un-barlowed),  I too agree with you and don't really see the point if the 40mm or 8mm (the 11mm is fine).  The others are excellent longterm investments, absolute pleasure to use.  I do not wear glasses by the way. 

[ronin]

A plossl is generally fine in a medium to slow scope, as long as the lens are ground fairly accurately there is little to go wrong - I suppose that getting the optical centres right is the main thing when the 2 lens are cemented.

Scatter and reflections are kept to a minimum as there just is not that much glass to cause problems.

So a well made plossl I would expect to work happily on anything that is f/7 or slower, that does assume that the scope itself is a reasonable item.

I also would have dropped the barlow into the chain for the same reason, it was at hand so give it a go.

Never sure about comparisons, even BST and TV plossls are getting close to a price difference of 2x and they are different designs and then comes the preference of the person doing the comparison. I have read comparisons where eyepiece A has come out best in 3 areas, a draw in a fourth and eyepiece B better in 1. Then the conclusion is eyepiece B is far the better.

[DRT]

To be fair to Tele Vue they do state that the 40mm is not par focal in their eyepiece specs section - I just didn't take that in when I was researching them !

My collection started by buying the 8mm to 25mm as a used set and then adding the 40mm, mainly because I wanted one of the lower powers but I couldn't find a 32mm. When I first realised I wasn't getting along with the 40mm I bought the 32mm and am pleased I did. I have a feeling the 40mm is going to spend its life as a very expensive finder eyepiece

[John]

Al Nagler of Tele Vue revised the curvature of the lenses of the plossl design so that their plossls would remain well corrected for astigmatism in scopes as fast as F/4. It was a subtle design change but enough that Nagler could get a patent on it.

[YKSE]

So a well made plossl I would expect to work happily on anything that is f/7 or slower, that does assume that the scope itself is a reasonable item.

Would you care to give the source about f/7 claim?

As John rightfully pointed out, TV plossls work down to f/4 scopes with patented edge design, and others simple plossl are usually referred as having f/6 as critical focus ratio, as here

http://www.astrosurf.com/re/evolution_of_eyepieces.pdf

and here

http://www.handprint.com/ASTRO/ae5.html

[Moonshane]

you may find a 40mm TV plossl will provide excellent solar views with scopes of a long focal length. my old 40mm TV widefield is a large chunky 2" eyepiece but provides lovely sharp views of the full disk in my 1600mm focal length 6" dob.

TV plossls represent excellent value for money, especially if bought used. I have 11,15,20,25 and 32.

[DRT]

I've ordered a TV eyeguard extender to see if it makes the 40mm more comfortable to use. The blurb on their marketing material suggests I might need two but at £20 a pop for an 8mm metal ring I'll try just one first.

[Moonshane]

they are very good http://stargazerslounge.com/topic/223548-what-to-get-the-person-who-has-everything-tv-eyeguard-extender/

I suspect you may need two for the 40mm.

you do get a spare rubber and eyepiece cap plus a nice box though

[DRT]

they are very good http://stargazerslounge.com/topic/223548-what-to-get-the-person-who-has-everything-tv-eyeguard-extender/

I suspect you may need two for the 40mm.

you do get a spare rubber and eyepiece cap plus a nice box though

I now have two spare rubber eyeguards, two spare 2" caps, two nice boxes and a 40mm TV Plossl that is a joy to use

[Moonshane]

Great stuff mate. Not a cheap option but transforms some lr eyepieces