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40mm Televue Plossl in Binoviewer?

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#1 Eddgie

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Posted 04 January 2013 - 01:36 PM

I am trying to go more to bino-only viewing, but I found one important attribute that I am missing with just the binoviewers and the 24mm, 17mm, and 13mm Hyperions... I can't get much of an exit pupil.

I originally did not consider using a 40mm Plossl becuase of the narrow apparent field, but now I realize that for faint targets like Nebula, many fit in the field of the 24mm Hyperions, but because the exit pupil is so small (2.16mm), I feel like I am not getting the brightness, and that forces a swap of diagonal and the insertion of the 41mm Panoptic.

I just purchased a pair of 40mm Televue Plossls. While the true field won't be larger, the exit pupil should go up to about 3.6mm exit pupil, so a fairly large jump in image brightness.

Is anyone else using this kind of setup? Does it work for you in the way I described? Or did I just spend a lot of money on something I will never use? LOL.

#2 johnnyha

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Posted 04 January 2013 - 01:50 PM

I dunno Eddgie but I'd love to find out. I recently got a pair of 32mm Brandons and I love them! I thought I loved the 24mm enough that I wouldn't need the 32mm, but the view in the 32mm is actually about 15% wider and its pretty spectacular. On a target like the Double Double in my 6" f8 it made a huge difference. I also recently got a pair of new 20mm TV Plossls to fill the gap between the 24mm and 16mm Brandon pairs, and I've grown very fond of them, for bot widefield and barlowed for Jupiter observations. 40mm I never even considered but why not? I think you are on to something here. FOV is 43 degrees, thats not too bad. Keep us posted!

#3 Eddgie

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Posted 04 January 2013 - 02:05 PM

Well, for me of course, the problem is that I am working at a focal lenght of 3950mm and with this aperture, I feel like the binoviewers are locking me in to small exit pupils.

I bought a Clicklock back for the scope in hopes of being able to make changing to the 2" diagonal and 41mm Pan easier, but if I just need a bigger image pupil and don't need the extra true field, it seemed like it would be easier to just swap in the 40s... Very close to the same exit pupil as the 41mm Pan.

But I just don't know if the 43mm Apparent field will be an issue.

I figure though that the image scale of the target will be so much smaller that it might not feel claustrophobic. In fact sometimes there is a lot of empty field in the skies around some galaxies and such, so perhaps it won't be an issue.

#4 junomike

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Posted 04 January 2013 - 02:08 PM

Eddgie, I`m not sure If It works as you describe, but I think you`ll be happy with the 40mm.
I have the a Bino set of the TV NJ`s and thought at first I`d only use the 40mm in place of the 32mm strictly for lower magnification. Well that is true, but I find I prefer the overall feel of the 40mm Pl. especially in a Refractor.
Keep in mind my set up includes one of Sieberts modified Prisms to reach focus without the need of an OCS.

Also, A friend (Tank) tried the 32mm and 40mm Plossls in his Burgess Binoviewer and the 32`s Vignetted slightly whereas the 40mm did not. Not sure as both have similar FOV. This was not an Issue for me as I use a TV Binoviewer with 27mm clear Aperture.

Mike

#5 pftarch

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Posted 04 January 2013 - 02:16 PM

I don't know how much of this applies, because I mainly view with my Z10 dob, but for me it went like this:

Bought a pair of Knight Owl 40mm Plossls. Used them, they were ok but then....

Bought a pair of GSO 32mm plossls. Used them, liked them better than the 40mm plossls, pretty much stopped using the 40mm, and then.....

Bought a pair of 28RKEs. Used them, liked them better then the 32mm plossls, pretty muched stopped using the 32mm plossls.

If I were to focus on the plossls only, and forget the whole RKE thing, I liked my 32's better because the 40's FOV was "soda straw" like and the 32's weren't as bad. Eye placement was easier with the 32's. (This is ironic because the 28 RKE's are MUCH MUCH MUCH fussier about eye placement than the 32 plossl, yet I still like them more, go figure.)

So if I could only keep mt 32's or my 40's I'd keep the 32's. Please note that in my case the 40's were a different, significantly cheaper brand than the 32's, and that may be skewing my results. In addition, neither the 32's or the 40's were Televue.

Good luck wherever you choose to go!

#6 Eddgie

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Posted 04 January 2013 - 04:14 PM

Well, for me these would be to get bigger exit pupil. I realize the field will be no larger, but the exit pupil will be quite a bit larger, so far the faintest targets, I would think that the added brigthness will be a benifit.

But it is an experiment. I don't see myself using them much, but I think there may be times when I want the brightest possible view of some Nebula like the Swan or Dumbell. I looked at the Dumbell and the little Dumbell, but with the 24mm eyepeices, they seemed dim. Plenty of room in the field though, so I just want to get the exit pupil larger so that they lok a bit brighter.

#7 pftarch

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Posted 04 January 2013 - 09:48 PM

Do you presently have a single TV 40mm plossl? It's hard for me to describe why I don't care for them as much as my 32's, but I felt the same way when I mono viewed them. If you are ok with single 40 it probably won't bother you in a paired scenario. If you want to experiment with my knight owl 40's for free, shoot me a pm and I'll mail you mine to play with for while.

#8 Eddgie

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Posted 04 January 2013 - 11:23 PM

A generous offer. Quite kind of you. But unnecessary I think.

No, I didn't have one, but have already bought a pair.

I have used 40mm Plossls in the past (10 years ago maybe?) and do remember the narrow field, but I feel as if I am missing out on the brighter deep sky performance that I get from the 41mm Panoptic. I know I won't get the same true field, but I will get a bit more brigntness.

The 32mm just didn't seem to give enough extra exit pupil to make it worthwhile.

So, just for times when I want to see a nebula or galaxy with a bit more brightness.

#9 GlennLeDrew

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Posted 05 January 2013 - 02:54 AM

I can't see why you shouldn't realize the gains you desire in image surface brightness that the larger exit pupil will provide. Especially if your sky is not overly bright.

#10 Astrojensen

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Posted 05 January 2013 - 08:49 AM

I have a pair of 40mm TS eyepieces (likely plössls) and they perform very well in their intended role, namely maximizing the exit pupil in long-focus telescopes. I have used them for galaxy observing in the Baader Maxbright with excellent results.

A wonderful feature of the TS eyepieces are their adjustable eyeguards, which is very important for ergonomics.


Clear skies!
Thomas, Denmark

#11 faackanders2

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Posted 05 January 2013 - 04:32 PM

Believe 24mm panoptic would provide widest TFOV in 1.25" eyepiece.

#12 Guest_**DONOTDELETE**_*

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Posted 16 January 2013 - 06:53 PM

:jump:
On my C14 and Mark V every time I start with TV pl 40mm 98X.
Then if seeing is OK Taka LE 30mm 130x.
Then Pan 24mm 163x.
But I start tu be very uppy :roflmao: wehn I can use XW 20 or 14mm 195x/280x.

Of course when seeing is bad the TV pl 40mm :jump: are the only one that give me satisfaction.

They are also very good on the C8.

In may opinion the TV pl 40mm are the only TV pl really important. All the other can have better choice.






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