32 replies to this topic

[Sarkikos]

As I was once again researching my possible entry into Night Vision, I came across the 67mm Convertor for the Tele Vue 55 Plossl. 

 

https://televue.com/...on-enhancement/

 

This will convert the TV 55 Plossl into a 67mm eyepiece with a 40 degree AFOV, matching the AFOV of the PVS-14 objective for night vision. 

 

Has anyone tried using the TV 55 Plossl + 67 Converter for visual without an NVD?  How was it?  Are there are practical uses for this setup without an NVD?

 

Mike

Edited by Sarkikos, 07 September 2022 - 08:21 PM.

[FoxIslandHiker]

Yes.  But only briefly.  In my scope, without NV, there is a large central black spot caused by the secondary.  This was just recently discussed in the NV section.

 

See https://www.cloudyni...and-exit-pupil/

 

To avoid a whole lot of blather from a repeat offender, jump to post #22.

 

With a NV device, the 55 Plossl with the 67 converter works great.  I had a great session with it last night.  Filters help.  Ha for nebulas and 642 for helping cut out light pollution for clusters and galaxies.

[sixela]

In my f/3.72 it gives a visually completely unusable exit pupil. I only use it visually to roughly focus before I put an NVD on top.

Should work fine in an f/12-f/15 Mak though.

Edited by sixela, 08 September 2022 - 02:22 AM.

[25585]

But for refractors?

[sixela]

Typically a 55mm Plössl (and for shorter f/ratio even a 41mm Panoptic) would show the same field at higher magnification, showing more stars and extended objects with the same surface brightness despite the higher magnification.

There has to be a _reason_ to pick a 67mm 40° over a 55mm 50° eyepiece.

[GOLGO13]

Seems like it should work in a C8. I'll give it a try sometime. 

 

It would provide a bit more exit pupil in a dark sky. 6.7mm vice 5.5 with the 55 plossl. Same FOV pretty much.

[Sarkikos]

I was thinking it might have a use in Cats and slow refractors when stacked with a deep sky filter.  The wider exit pupil would give a perceived brighter field which could be advantageous particularly with H-Beta and OIII filters.

 

For fast Newtonians, a 55mm Plossl is pushing the envelope enough by itself.

 

Mike

Edited by Sarkikos, 08 September 2022 - 09:15 AM.

[chemisted]

As I was once again researching my possible entry into Night Vision, I came across the 67mm Convertor for the Tele Vue 55 Plossl. 

 

https://televue.com/...on-enhancement/

 

This will convert the TV 55 Plossl into a 67mm eyepiece with a 40 degree AFOV, matching the AFOV of the PVS-14 objective for night vision. 

 

Has anyone tried using the TV 55 Plossl + 67 Converter for visual without an NVD?  How was it?  Are there are practical uses for this setup without an NVD?

 

Mike

In another thread you mentioned you have the Russell long focal length eyepieces.  I do not have the TV 67 as I use the GR 65 and 85 for afocal nebular viewing and they perform exceptionally well. Have you tried yours in your scopes as you suggest for the TV 67 in this thread?

Edited by chemisted, 08 September 2022 - 01:14 PM.

[Sarkikos]

In another thread you mentioned you have the Russell long focal length eyepieces.  I do not have the TV 67 as I use the GR 65 and 85 for afocal nebular viewing and they perform exceptionally well. Have you tried yours in your scopes as you suggest for the TV 67 in this thread?

I've only tried the GR long focal length eyepieces natively - without a filter, without NVD - in various f number scopes to see how they would perform.  I haven't used them with DSO filters yet.  I don't have an NVD - yet - but intend to try these GR eyepieces for that as well.

 

What NVD do you have?  A PVS-14?

 

Mike

Edited by Sarkikos, 08 September 2022 - 01:35 PM.

[chemisted]

No, I have three C-mount devices.  I recently wrote about them in the following thread:  https://www.cloudyni...y-three-amigos/

[ButterFly]

It's the same true field as a 41 Pan, except it's squished into a forty degree AFOV.  There really is nothing to be gained.  As the exit pupil goes up, everything gets brighter, including the background, by the same amount.  Contrast is the same and everything is smaller.  That doesn't make much easier to see.

 

Of course I've put in all my scopes and looked visually.  Who wouldn't want to see the effect of the giant central obstruction of a 67mm eyepiece on the Moon with a dob?  It's nothing good, in case you were wondering.  The central obstruction is a darker region in the middle of the field.  It's not totally dark.  In my refractors, again, it's the same true field as in my 41 Pan, except squished into a forty degree AFOV.  And yeah, even with OIII or h-beta filters, the background is brighter, as is the object.  No gain in contrast, no gain in true field, and everything is smaller.

 

For digiscoping with my 80mm and phone during the day, it works great.  It shoots down the effective f/ratio of the scope to the camera in the same way it does to an NV device.

[Sarkikos]

It's the same true field as a 41 Pan, except it's squished into a forty degree AFOV.  There really is nothing to be gained.  As the exit pupil goes up, everything gets brighter, including the background, by the same amount.  Contrast is the same and everything is smaller.  That doesn't make much easier to see.

 

Of course I've put in all my scopes and looked visually.  Who wouldn't want to see the effect of the giant central obstruction of a 67mm eyepiece on the Moon with a dob?  It's nothing good, in case you were wondering.  The central obstruction is a darker region in the middle of the field.  It's not totally dark.  In my refractors, again, it's the same true field as in my 41 Pan, except squished into a forty degree AFOV.  And yeah, even with OIII or h-beta filters, the background is brighter, as is the object.  No gain in contrast, no gain in true field, and everything is smaller.

 

For digiscoping with my 80mm and phone during the day, it works great.  It shoots down the effective f/ratio of the scope to the camera in the same way it does to an NV device.

Like I said earlier, I wouldn't even bother trying the 67mm eyepiece in a fast Dob.

 

Mike

[a__l]

Yes.  But only briefly.  In my scope, without NV, there is a large central black spot caused by the secondary.  This was just recently discussed in the NV section.

 

See https://www.cloudyni...and-exit-pupil/

 

To avoid a whole lot of blather from a repeat offender, jump to post #22.

 

With a NV device, the 55 Plossl with the 67 converter works great.  I had a great session with it last night.  Filters help.  Ha for nebulas and 642 for helping cut out light pollution for clusters and galaxies.

FoxIslandHiker   ??? This is what "lot of blather" ?

 

If you want to link to a specific post with a specific number, you can do it without problems and your "kind" expressions.

 

Secondly, there are two participants in the discussion, besides me sixela

 

Third, the OP didn't specify which telescope he would be using.
Perhaps this is a refractor and your link on Lockwood message about the shadow of the secondary does not make sense.

 

If it refractor, compare with the exit pupil of its telescope+TV67 and advise to measure the pupil of the OP (ruler). It depends on the age of the OP, the older he is, the smaller. The greater the difference, the more OP's pupil will cut the aperture of his telescope.

If OP has children, this kit will probably suit them better

Something like this.

Edited by a__l, 09 September 2022 - 07:15 AM.

[N-1]

Reviving this thread to see if anyone has tried this product, in a suitable scope, without NVD. None of the problems described above apply to my use case. What's the image quality like? Any colour changes? Field stop sharp or fuzzy? Things like that.

 

Thanks!

[sixela]

As stated above, it’s mainly useful in really slow scopes, where even a Pan 41 has an exit pupil that might be too small for some objects.

In those scopes (typically Maks) they work quite well, although the smaller ones often vignette the outer part of the field. In such scopes even the simple three group design is quite good at suppressing aberrations (in fact better than the 55mm on its own).

Refractors over f/10 are a dying breed; those that also support a 2” field even more so.

Perhaps if you revive the thread you could describe your use case rather than tell us what does not apply?

Edited by sixela, 06 September 2024 - 01:02 PM.

[Jeff Morgan]

As I was once again researching my possible entry into Night Vision, I came across the 67mm Convertor for the Tele Vue 55 Plossl. 

 

https://televue.com/...on-enhancement/

 

This will convert the TV 55 Plossl into a 67mm eyepiece with a 40 degree AFOV, matching the AFOV of the PVS-14 objective for night vision. 

 

Has anyone tried using the TV 55 Plossl + 67 Converter for visual without an NVD?  How was it?  Are there are practical uses for this setup without an NVD?

 

Mike

 

You probably would not want to do this.

 

Note the converter is easily added or removed, so the base eyepiece is still available for use in non-augmented visual observing.

 

However, it would be slightly cumbersome to do that multiple times during a session. The more reasonable scenario would be NV configuration night 1, standard configuration night 2.

 

YMMV on that of course, but speaking for myself I would be thumb-printing lenses or dropping something to the ground in a multiple-swap observing session.

[sixela]

He wasn’t talking about changing from 55 to 67 and vice-versa, just using it as a 67 mm 40° eyepiece.

Tl;dr: it works, but the uses for such an eyepiece are limited. Not impossible, though, I know a couple of Schiefspieglers for which it’s a really good eyepiece if you’re interested in anything except planets.

[N-1]

As stated above, it’s mainly useful in really slow scopes, where even a Pan 41 has an exit pupil that might be too small for some objects.

In those scopes (typically Maks) they work quite well, although the smaller ones often vignette the outer part of the field. In such scopes even the simple three group design is quite good at suppressing aberrations (in fact better than the 55mm on its own).

Refractors over f/10 are a dying breed; those that also support a 2” field even more so.

Perhaps if you revive the thread you could describe your use case rather than tell us what does not apply?

Thanks. It's for an f/13.3 refractor to get me to a useful 5mm exit pupil, and I already have the 55 TVPL. Strictly visual, no NV.

[Sarkikos]

My slowest telescopes compatible with the 2" TV 55mm Plossl with 67mm Converter would be the Bosma 150 f/12 and the SkyMax 102 f/12.7.  Both are Maks, the former a Rumak and the latter a Gregory ("spot").  Here are the stats when the 67mm setup is used in these scopes:

 

Bosma 150 Mak f/12:  40-degree AFOV, 1.5-degree TFOV, 27x, 5.6mm exit pupil.

 

SkyMax 102 Mak f/12.7:  40-degree AFOV, 2.1-degre TFOV, 19x, 5.3mm exit pupil.

 

OK.  Considering these two cases, would either of these have practical use in the field for visual?  Would either be better in some way(s) than possible alternatives?   Would they be worse?

 

Mike

Edited by Sarkikos, 06 September 2024 - 10:25 PM.

[N-1]

Maximised exit pupil has its advantages, to a point. The practical use is a brighter image, which is useful for some objects, and filters. 5-6mm works very well for me.

[GGK]

Reviving this thread to see if anyone has tried this product, in a suitable scope, without NVD. None of the problems described above apply to my use case. What's the image quality like? Any colour changes? Field stop sharp or fuzzy? Things like that.

 

Thanks!

I've tried the eyepiece in a TV-85, 600mm focal length, f/7.  The image is fine, but not as nice as a 40mm XW or 32mm Masuyama, which have the same true field as the TV-67.  

 

Three things are very evident. 

 

First is that the TV-67 needs A LOT of outward focuser travel.  I extended the barrel by 2 inches, otherwise it would only come to focus when I held the eyepiece above the diagonal.

 

Second is that the eye relief is LONG.  Even with the eye lens recessed, I have to hover above the eyepiece.  An eye guard extender would be beneficial like it is for the 32mm and 40mm TV Plossls.

 

The apparent field is about 40^o. Using the TV-67 visually instead of the 40mm XW has the same feel as using the 40mm Plossl instead of the 32mm Plossl - A brighter image which can be beneficial when using narrow-band nebula filters, but a negative for non-filtered visual use except for the few times one needs the largest exit pupil.

 

When using the TV-67 in my 85mm, f/7 refractor, the effective aperture drops to about 55mm, so that combined with the brighter background makes some of the stars invisible that are visible in the 40mm XW. 

 

So, for a more fair comparison, this morning I pointed toward Orion and put the 2X Powermate between the eyepiece and diagonal in order to see full aperture for both the TV-67 and 40mm XW.  1200mm focal length, f/14.  There was no change in my general impression of the eyepiece, but I did see a little EOFB in the TV-67. Now, the sky was entering morning twilight and some clouds and haze were present, so it might simply have been from the atmosphere interacting with the larger exit pupil.  The exit pupil was ~2.9mm for the 40mm and 4.8mm for the 67mm, so a major increase in image brightness.

 

If you need the 5mm exit pupil, then I wouldn't hesitate to get the 67mm conversion lens, accepting the 40^o apparent field as the trade off.  It's very simple to install and remove if first I take off the top shroud of the 55mm Plossl.

 

---and the field stop appeared clear and sharp to me.

 

Gary

Edited by GGK, 07 September 2024 - 05:56 PM.

[N-1]

This is the exact info I was looking for. Thank you.

[Highburymark]

I second everything that Gary has said above. The TV ‘67mm’ works surprisingly well optically in an F/6 60ED refractor. There’s a bit of field curvature and a tiny bit of astigmatism at the edge, but otherwise views are fine. The outward travel is an issue, however - the TV67 requires a long extender to reach focus. That’s quite a lump for my little 60ED focuser to contend with.

[Celestro21]

I do have a question. I saw the 67 mm converter for the 55 plossl at NEAF. I am heavy into night vision astronomy. Is it worth spending the money getting this or should I just buy a focal reducer. I have a c11 f/10 and I also have a truss tube cassegrain 10 inch f/12. Thanks

[Highburymark]

I do have a question. I saw the 67 mm converter for the 55 plossl at NEAF. I am heavy into night vision astronomy. Is it worth spending the money getting this or should I just buy a focal reducer. I have a c11 f/10 and I also have a truss tube cassegrain 10 inch f/12. Thanks

With such slow and high power scopes as yours, I’d have thought the 67mm would be an essential bit of kit - possibly with a focal reducer too. It’s really useful for large, faint nebula with my scopes, but it really depends what you want to see - objects like the North American nebula are vast, so even with an F/7 85mm refractor, I need the 67mm to frame it well with afocal night vision.