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brian nordstrom
23-11-2015, 11:07 AM
:D As the title says , this is a short review of a short 3 way shootout between 3 of TelVue's mid power eyepieces .

They are ,

#1 , The awesome 19mm Panoptic , giving 53x , probably one of the best eyepieces ever made , its beautiful to look at as well to look thru .

#2 , The now seemingly forgotten 18mm Radian , giving 55.5x , this eyepiece is beautiful to look thru with its 20mm eye relief .

#3 , The now not made TelVue 21mm smooth side plossl , giving 48x with sweet Japan made optics .

All 3 were only a gnat's hair from being par-focal so this made it very easy in the swapping out eyepieces .

The night was Friday night 20/11/15 , a very good night here .
Targets were , the 8 day old moon , M42 and M22 .

Scope used was my well collimated and cooled iStar 127mm f8 achromat refractor .

First up was M22 before it dropped to low in the mire .

Here it was obvious that the Radian did not have the light thru-put as the other 2 , it still resolved the intervidual stars but not as easily as the Panoptic and especially the Plossl , this is where it really shone , showing the Globular as a tight ball of stars as only a refractor can , beautiful .

So here the winner is the Plossl '
#1 , 21mm Plossl .
#2 , 19mm Panoptic.
#3 , 18mm Radian.

Second up the moon and as the refractor does show very faint CA on the moon , this is very subdued for a refractor working at f8 , the main test here was the colour imparted by each eyepiece .

Time and time again I changed these 3 out testing , taking rough notes and one thing I kept seeing was the more natural hues seen on the moon thrown up by the Radian , I seen this every time I looked at the moon using this eyepiece and it became the favourite of the night , the Panoptic with its slightly larger field was vey good , but seemed a little ' Clinical ? '
The Plossl was easily as sharp as the Panoptic , but showed the most CA of the 3 , very subtle but definatly there '.

So on the moon I found this ,
#1 the 18mm Radian .
#2 the 19mm Panoptic .
#3 the 21mm Plossl .

Next up , M42 , I found that the Radian did not have the light thru-put the Panoptic and Plossl had , it was as sharp but the wings were harder to make out in the Radian .
The Panoptic was the best here as its larger FOV really shone as it took the whole field in its stride , very nice view .
The Plossl was as sharp but the FOV was not there .

The trapezium was easily seen as 4 stars in all 3 .
#1 here was the 19mm Panoptic
#2 was the 21mm Plossl .
#3 was the 18mm Radian .

All 3 of these eyepieces are winners , excelling in what they do best and essentially perfect in all ways .
Hope you all enjoy this and please , comments welcome .

Brian.

N1
23-11-2015, 11:49 AM
Interesting write up, Brian.
Could the Radian's apparently lower throughput be to do with the slightly higher power it produces compared to the other two? The M22 ranking suggests power is a factor here. Also M22 being critically low, a few minutes between EPs may have made quite a difference.

MortonH
23-11-2015, 11:50 AM
Interesting results, Brian. Now you need to buy an 18.2mm DeLite and do the comparison again. :P

brian nordstrom
23-11-2015, 12:38 PM
:question: Good point , but I think it has to do with what all my other Radians do ( I have a full set ) and that's to impart a soft/yellowish ? hue onto the view , I like it as it as I say give a nice natural tint to the moon , Jupiter and Saturn especially when the powers hit 200x plus , nice and natural .

I have read that TV use 'Lanthium' glass in the Radians , perhaps that's why ? who knows .
On M22 perhaps , I will redo the comparisim when we get out to our dark sky site and use Omega Centarui as the target using the iStar again and report back .

Morton :eyepop: please !!! :D , I would be divorced if I started that , but on that an observing buddy has the Delos set and they are very sharp , more like the plossl's with a Panoptic FOV . so I imagine the DeLits would be similar :shrug: ,,,,

I love my Radians and wont sell them in a hurry , and yes there are better for deep sky eyepieces out there for sure , but for Luna/planetary viewing they are the best getting easy ( stupid ? ) high powers with ease .

Brian.

FlashDrive
23-11-2015, 03:24 PM
....and then sell it on to Morton ....:D ..... I'm sure he'd love one....;)

MortonH
23-11-2015, 04:58 PM
One other factor is that there is quite a weight difference between the three eyepieces you compared. The Radians get especially heavy at the shorter FL's, something that the DeLite's seem to avoid.


BTW, if anyone wants to sell me a DeLite, it's the 11mm I'm most interested in! :lol:

brian nordstrom
23-11-2015, 06:13 PM
:thumbsup: There is but a scope like my iStar does not feel the difference , it is not that much .
Brian.

clive milne
23-11-2015, 11:30 PM
It's probably worth adding the caveat that the performance of a plossl design is heavily influenced by the focal ratio of the telescope it is used with, irrespective of the level of the quality of the eyepiece or telescope.
F8... no problem
f4... forget it.

brian nordstrom
24-11-2015, 09:23 AM
:shrug: Paracorr or ,,,
,,,, if you are working at f4 you will probably have either a CCD of box of Etho's to stick in the focuser :rofl: .
Brian

SkyWatch
24-11-2015, 09:54 AM
Thanks for the review Brian. I haven't had the pleasure of using the 21mm Plossl, but I went through the exercise a few years back when I wanted a good, medium power eyepiece that was as sharp as possible. I initially purchased the 19mm Panoptic based on reviews I had seen that it was the best eyepiece ever made, etc. Unfortunately in my case it was not quite(!!!) up to that exalted standard (in fact a GSO 20mm performed better!), and close inspection even revealed a small air-bubble in the glass. QC was not the best! It was quite fuzzy from about 60% of the way from the centre (in a range of scopes from f5 to f10), and the field distorted significantly. Sounds like you got a better one...
I ended up returning it and got the 18mm Radian instead- and I concur it is a lovely eyepiece.
Unfortunately it often sits in my eyepiece box now because I got a 13mm Nagler6 a couple of years later (the $A was so much better then!): it has a pretty much identical fov but at a higher power and is also beautifully sharp to the edge. The eye relief is not quite as good, but otherwise it is a great little eyepiece.
All the best,
Dean

brian nordstrom
24-11-2015, 10:51 AM
:sadeyes: Shame about your experiences with the Panoptic ,, its the first negitive thing I have ever heard .

I have the 15 ,19 , 22 , 24 and 27 and they are by far the first eyepieces I grab when starting an observing session , normally the 27mm when using my C9.25 and the 19mm when using the iStar refractor .
These seem to be a good gauge of sky conditions , then for higher power luna/planetary viewing its the Radians every time .

Brian.

bytor666
24-11-2015, 11:08 AM
Excellent report Brian!

I'v'e always wondered about the 18mm Radian, and while I am a nutter for long eye relief, The throughput of the 18mm Radian would keep me from getting one, so I will stick to keeping my 22mm LVW instead.

Cheers Brian!!!! :)

clive milne
24-11-2015, 12:13 PM
The issue with plossls at fast focal ratios is that the design suffers from spherical aberration, even if the telescope is an aplanat (or an anastigmat) the spherical aberration remains.
At f/5 the system is no longer diffraction limited....

SkyWatch
25-11-2015, 09:49 AM
Thanks Brian,

I tried a borrowed 24mm Panoptic at the time as well: and it killed the 19 for clarity and lack of distortion, although it still showed a curved field towards the edges. I did toy with the idea that I had got a Friday-afternoon-before-a-long-weekend one, but there were too many issues along with the air bubble, and I didn't like the curved field of the 24, so I followed a "once bitten" approach and got the Radian...

I am surprised by the comment about the light through-put of the 18mm Radian. I haven't noticed any dimming- but as you say it might be the glass used. I had a Vixen "Lanthanium" once that gave a decidedly yellow cast.

All the best,

Dean