55mm Televue Plossl : Worth while with C8 ?

[Space Hopper]

Hi Everyone,

Interested in your thoughts regarding using a 55mm eyepiece with a Celestron C8 (Edge HD)

I already use a 31mm Nagler with my other scope ; a William Optics refractor.

I've tried using the big 31 on the C8, but its weight is an issue, making the scope very 'back heavy'

So i was thinking about a smaller, more manageable eyepiece and have come across the 55mm Televue Plossl.

It would be only used in the C8 of course, for low power (37x magnification) sweeps of the sky.

User thoughts and experiences very welcome.....

Thanks 

[Stu]

I did try a 55mm Plossl for a while in my 200mm mak. It did give a wide field (considering it is a mak!), but I found that under anything other than a very dark sky it tended to be washed out because of the larger exit pupil.

There is the 41mm Panoptic, which admittedly is not dissimilar weight to a 31mm Nagler. How about the Vixen 42mm LVW? This has a 72 degree afov and will give a wider field than the Plossl with smaller exit pupil. I think it is around 550g which is similar to the Plossl? Should give a darker sky and better contrast. Not tried one myself but they get good reviews.

Stu

[Space Hopper]

Your OMC200 is an F/20 Stu isn't it ? So surely that would be a small exit pupil, not a large one ?

I'm working along the lines of 55mm divided by F/10 with the C8, i.e. 5.5mm exit pupil. Have i got that right, or am i muddled up ?

Ironically, i used to own a Vixen 42mm LVW. Sold it to fund the N31 !!

Thanks for your thoughts anyway.

TB

[scarp15]

The lowest power that I have used in my C8 was a 35mm panoptic X58. Worked very well in a dark sky but not advised for any light pollution, as the views get a bit washed out. In this circumstance, I also use to own a 27mm panoptic (X75) - an effective low power eyepiece for a C8 in any situation and a more reasonable 2.7mm exit pupil.

[John]

I used to use a Vixen 50mm 2" plossl with a C8 a few years back. It worked OK but the views were a bit washed out compared with a 38mm 70 degree super wide eyepiece that I also had at the time. I seem to recall I was seeing traces of the shadow of the central obstruction at times too.  

[Stu]

Your OMC200 is an F/20 Stu isn't it ? So surely that would be a small exit pupil, not a large one ?

I'm working along the lines of 55mm divided by F/10 with the C8, i.e. 5.5mm exit pupil. Have i got that right, or am i muddled up ?

Ironically, i used to own a Vixen 42mm LVW. Sold it to fund the N31 !!

Thanks for your thoughts anyway.

TB

Hi TB

I did say larger, not large :-)

You are right, it was only 2.7mm but I still didn't find the views under my skies very nice.

I think in general, a wider afov, shorter focal length tends to work better giving a darker sky background. If your skies are good then perhaps it would be ok but I think with any LP around you may not like it.

Stu

[Mark in Macc]

I would try to balance the OTA and use the Nag. I use an ES 82 deg 30 mm with my C9.25, which is a similar weight and is really excellent.

[Naemeth]

I would try to balance the OTA and use the Nag. I use an ES 82 deg 30 mm with my C9.25, which is a similar weight and is really excellent.

I agree, balancing the C8 is certainly cheaper than a new eyepiece.

[Space Hopper]

Thanks for your comments chaps.

I think i need to be realistic. My light pollution is pretty bad here in my part of Derby.

The C8, i don't think is really designed to work with a Tv Nag 31mm. Its just too big & heavy.

An  f/10 C8 isn't a widefield telescope either.

I'll continue using the N31 with my refractor where there's no size / weight issues,  and use the C8 with the binoviewer or higher power eyepieces only. 

But with a whopping 38mm of eye relief (Tv 55mm Plossl), i thought light washout wouldn't be such an issue.

I'll start thinking about Astrofest in a couple of months. I'll mention it to the Televue staff there and see what they reckon.

Cheers, clear skys etc

TB

[Mark in Macc]

The binoviewers I use weigh between 850 and 1000g depending on what EPs I use, which is pretty much what a Nagler 31 mm and ES 82 deg 30 mm weigh. The chances are that the binos you use won't be far off the weight of the Nagler.

[faulksy]

i use the sw aero 40mm for wide views, it is very light for a 2" and gives me 1.15 tfov

[michael.h.f.wilkinson]

Thanks for your comments chaps.

I think i need to be realistic. My light pollution is pretty bad here in my part of Derby.

The C8, i don't think is really designed to work with a Tv Nag 31mm. Its just too big & heavy.

An  f/10 C8 isn't a widefield telescope either.

I'll continue using the N31 with my refractor where there's no size / weight issues,  and use the C8 with the binoviewer or higher power eyepieces only. 

But with a whopping 38mm of eye relief (Tv 55mm Plossl), i thought light washout wouldn't be such an issue.

I'll start thinking about Astrofest in a couple of months. I'll mention it to the Televue staff there and see what they reckon.

Cheers, clear skys etc

TB

I beg to differ. My C8 works just fine with the 31T5 "Panzerfaust", even when mounted in teh heavy Denkmeier filter-switch diagonal, and a 70mm finder on the back:

Add a dew shield at the front (highly recommended anyway) and the balance is good enough on my Great Polars mount (with the OTA pushed as far forward as possible). You can also add a small counterweight to the dovetail bar (I might get a little Vixen-style clamp from TS (38 euro), and attach a small weight to it for fine-tuning).

The focusing mechanism of the C8 is ideally suited to the weight of the 31T5, because the EP is fixed.

[YKSE]

Aero 40mm is my wide field EP for C8 too, gives 1.36deg FOV, same as the 55 TV plössl, the weight of almost the same too (520gram).

[michael.h.f.wilkinson]

Aero 40mm is my wide field EP for C8 too, gives 1.36deg FOV, same as the 55 TV plössl, the weight of almost the same too (520gram).

I had the TMB Paragon 40mm (the Aero is a clone, I understand), and it is very nice in the C8. I sold it only when I found that I was not using it any more after the arrival of the 31T5 (smaller exit pupil, so better in LP, and nearly the same FOV). I sometimes have twinges of regret. The paragon was a well made Ep and surprisingly light. The Aero is the same, by all accounts.

[Space Hopper]

Ok........this this is going off thread a little.

Let me ask another question then.....

Will a Tv 55mm Plossl show me any more of the sky than my N31 using the C8 ?

Its fl is 2032mm.  According to my vague calculations theres not much in it : the 55P edging it but only giving roughly half the magnification.

I think i'll abandon the idea of a 55P, and, as i say, use the C8 with my bino only for visual use.

By the way....i'd advise anyone with a C8 to try it with a bino-viewer. I know the combined weight would be similar (a bit less though) to using a N31 set-up as discussed,

but to me theres no contest. Lunar looked amazing last week with my 19Pans.

Keep the light path as short as possible and let the views blow you away.

Once again guys, thanks for your advice & input. 

[John]

Let me ask another question then.....

Will a Tv 55mm Plossl show me any more of the sky than my N31 using the C8 ?

Its fl is 2032mm.  According to my vague calculations theres not much in it : the 55P edging it but only giving roughly half the magnification.

I think i'll abandon the idea of a 55P, and, as i say, use the C8 with my bino only for visual use.

TV 55mm Plossl, with your scope = (approx) 1.35 degrees true field at 59x

TV 31mm Nagler = 1.25 degrees at 153x.

As you say, not much in it other than quite a lot of magnification !

[Mark in Macc]

Are those magnifications correct John? Seems a little high to me.

[John]

Are those magnifications correct John? Seems a little high to me.

Oops, thats embarrassing 

Well spotted Mark - the true fields are OK but the magnifications should be 37x and 66x (rounded) respectively.

[michael.h.f.wilkinson]

The 55 Plossl gets essentially the same TFOV as the 40mm Paragon (1.34 degrees if you calculate by field stop), and I found I did not use the Paragon again, as stated. I must say I am tempted by the idea of having a binoviewer with my C8 (I have two MaxVision 24mm EPs, so I am good to go in that sense), but on the other hand, I rather love the wider fields provided by my 2" EPs.

[Mark in Macc]

Have both. I use my binoviewers for the moon and planets and the 2" beasts for DSOs and for wider views. The binos will add significantly to the optical path and increase the focal length. You will never get wide field views with binos and a SCT.

[michael.h.f.wilkinson]

Have both. I use my binoviewers for the moon and planets and the 2" beasts for DSOs and for wider views. The binos will add significantly to the optical path and increase the focal length. You will never get wide field views with binos and a SCT.

It is tempting to go towards binoviewing with the SCT, but given the EPs I have, finding a second one for each would become very, very costly. I would rather invest in a bigger solar scope (LS60PT) to improve my solar capabilities or tracking mount (HEQ5, EQ6, or similar) to get into guided DSO imaging

[Mark in Macc]

It can get expensive, but certainly worth trying if you can. I have been able to borrow a pair of WO binoviewers from my Astro club that came with 2 EPs. I started out with that then added a couple of pairs to provide a range. I already had 1 25 mm TV plossl, so that helped. I don't observe the moon or planets without them now. I find the views quite remarkable.

[michael.h.f.wilkinson]

It can get expensive, but certainly worth trying if you can. I have been able to borrow a pair of WO binoviewers from my Astro club that came with 2 EPs. I started out with that then added a couple of pairs to provide a range. I already had 1 25 mm TV plossl, so that helped. I don't observe the moon or planets without them now. I find the views quite remarkable.

With Plossls things are manageable, but I cannot handle their short eye relief on planets. Given the cost of my XW and Delos EPs, I am not going down that path.

[alan potts]

I had the 55mm before the 41mm Panoptic, I thought it was a cheap way to a wide field and I was wrong. It is a fine eyepiece but you cant beat wide FOV in 68 degree and larger eyepieces on these scopes. In the end I sold it on as I found it was a bit like drinking straw viewing after having the others. I do not find the same problem up the scale where the magnification kicks in the likes of orthoscopics, it is just wide boys.

Alan

[Space Hopper]

It can get expensive, but certainly worth trying if you can. I have been able to borrow a pair of WO binoviewers from my Astro club that came with 2 EPs. I started out with that then added a couple of pairs to provide a range. I already had 1 25 mm TV plossl, so that helped. I don't observe the moon or planets without them now. I find the views quite remarkable.

I'm with you there Mark. The views are indeed remarkable.

I can certainly recommend the Baader Maxbright. They use GPCs so you don't need to spend mega bucks on lots of eyepieces. My 19Pans & 13Nags cover everything I need.

.

With Plossls things are manageable, but I cannot handle their short eye relief on planets. Given the cost of my XW and Delos EPs, I am not going down that path.

Michael, the 25Tv Plossls have very good eye relief at 17mm and work very well in a Baader Maxbright.

Why spend a fortune on Ethos Delos etc when you can use both eyes ? The Maxbright is great value at under £200uk

I can't recommend them enough.....