Televue Paracorr Vs. Other Coma Correctors

[TangoCharlie]

Greetings!

 

In delving into the world of astronomy in prep for buying a 8" F4.9 Orion Newtonian, I understand that I will have to contend with the issue of COMA.  Several Questions please:

 

1. Expense - Is the cost of a Paracorr worth it compared with buying another coma corrector from other vendors?

 

2. Compatibility- Are there compatability issues in using a Paracorr with say an Orion Newtonian?

 

3. Limitations - Are there any limitations in using a Paracorr with certain A. Eye Pieces, B. Barlows, or use of a camera or CCD? 

 

4. Two Paracorrs - Do I need two separate Paracorr - one for visual and one for AP?

 

TC

[stepping beyond]

TV Paracorr t2 is an awesome piece of hardware, worth it . It has 3  functions besides being a coma corrector . All glass in any of my Tv products are grade A , my other glass isn't even close. Versatile , usable with  2 " or 1 1/4" eps drop in "videocams , dslr or ccd"Tunable top comes off and you'll need an adapter to fit your specific camera model straight to the lens barrel. SB

[TangoCharlie]

Stepping Beyond,

Thanks for the reply.  You mentioned three other functions besides coma corrector.  Was it the

quality, versatility, and adapter you mentioned OR did you have other functions in mind?  Very interested!

Also - one question I had was do you need two Paracorrs - one for viewing and one for AP?

Thanks!

[Louis D]

I've had good luck with the GSO coma corrector once I added a 15mm to 25mm extension between the eyepiece holder and the optics unit.  I can't remember exactly which length I ended up settling on.  I then parfocalized my eyepieces to focus at the shoulder if they were out more than 6mm from that point.  It works great at f/6 this way.  It really helped flatten the field and clean up the edges in my Newt.  There's no noticeable vignetting even with my 40mm Meade 5000 SWA.  It also worked great to bring my camera to focus in my newt as well as flatten the field and correct coma when photographing the Mercury transit last year (see photo below).  Mercury is the dot toward the right edge.

As far as I know, you can't really barlow with a CC because it throws off the focus point, and thus the distance between the primary and the CC.  It may be possible the SI SIPS system, but I haven't figured it out yet with my setup.

36 minutes ago, stepping beyond said:

All glass in any of my Tv products are grade A , my other glass isn't even close.

My Pentax glass is easily as good as my Televue glass.  My new 17mm ES-92 is easily as good as my TV Delos.  My GSO 2X 2" ED barlow is easily as good as the TV Big Barlow.  The 40mm Meade mentioned above easily matches the 41mm Panoptic while maintaining a sharp field stop that the Panoptic struggles to maintain.  I will say my 30mm ES-82 is no match for the 31mm Nagler T5 correction wise, so there is that.  Nikon, Leica, and Zeiss glass are also easily as good as or better than TV glass based on reports I've read.

TV products are good across the board, but there are other good glass manufacturers out there as well.

[Tim]

The Mkii Paracorr is fine for both visual and photographic use.

It is expensive......but it is Televue.......not sure they do "cheap"!

Be aware that the Paracorr acts as a slight barlow too, I think it is X 1.15

I'm not sure  but I have never seen another option so versatile, so easy to use, and that performs so well to be honest.

But I would get your scope first and see how you get on with the eyepieces you are using. You will soon know whether or not you will require/want the corrector.

Tim

[alanjgreen]

At f4.9, I would wait to see if coma actually is a problem for you in this scope.

you may not be that sensitive to it, and 4.9 is not that fast. Sub 4.0 you would need one but you may get away with it.

Alan

[alanjgreen]

7 hours ago, Louis D said:

I've had good luck with the GSO coma corrector once I added a 15mm to 25mm extension between the eyepiece holder and the optics unit.  I can't remember exactly which length I ended up settling on.  I then parfocalized my eyepieces to focus at the shoulder if they were out more than 6mm from that point.  It works great at f/6 this way.  It really helped flatten the field and clean up the edges in my Newt.  There's no noticeable vignetting even with my 40mm Meade 5000 SWA.  It also worked great to bring my camera to focus in my newt as well as flatten the field and correct coma when photographing the Mercury transit last year (see photo below).  Mercury is the dot toward the right edge.

As far as I know, you can't really barlow with a CC because it throws off the focus point, and thus the distance between the primary and the CC.  It may be possible the SI SIPS system, but I haven't figured it out yet with my setup.

My Pentax glass is easily as good as my Televue glass.  My new 17mm ES-92 is easily as good as my TV Delos.  My GSO 2X 2" ED barlow is easily as good as the TV Big Barlow.  The 40mm Meade mentioned above easily matches the 41mm Panoptic while maintaining a sharp field stop that the Panoptic struggles to maintain.  I will say my 30mm ES-82 is no match for the 31mm Nagler T5 correction wise, so there is that.  Nikon, Leica, and Zeiss glass are also easily as good as or better than TV glass based on reports I've read.

TV products are good across the board, but there are other good glass manufacturers out there as well.

I agree with this.

BUT if you go faster than f4 (which you are not at 4.9) then you are safest going with TV, they test their eyepieces down to f3 (other manufacturers don't)

if you have Ethos EPs then these have been designed to work perfectly with Paracorr 2.

[alanjgreen]

As far as Barlow is concerned, TV recommend you use a power mate with paracorr.

[scarp15]

The paracorr can enable some eyepiece lines to become parfocal. It will also flatten the field of view slightly, which is beneficial for imaging and if using wide angle or ultra wide eyepieces. The long barrel, which can be extended outwards, also serves as an excellent extension tube. At F4.9 if just for visual, to begin with, see how you get on, it will largely be towards the edge of the field that will show coma. 

[estwing]

39 minutes ago, alanjgreen said:

At f4.9, I would wait to see if coma actually is a problem for you in this scope.

you may not be that sensitive to it, and 4.9 is not that fast. Sub 4.0 you would need one but you may get away with it.

Alan

^^ this +1

[swamp thing]

+2 wait and see..........

 

[alan potts]

I have to say it would depend on the eyepieces that you intend to use. Personally I feel a Paracorr is a must for high end and very wide field eyepieces like Ethos, though of course there are other 100 degree offerings on the market and Paracorrs for that matter. Speed of scope really matters, I would say F5 and above you could live though on most eyepieces but I would still want a perfect field from say a 21mm Ethos costing many hundreds of pounds, why pay the earth for a well corrected EP that is not sharp to the edge for avoidable coma.

Recently I used Panoptic's, I have 3 of them, without the Paracorr and even at F 4.3 I was fairly happy, though I know members with lightning fast scopes like F 3.9 and I am not sure I would feel the same given one of them outside in the garden.

I guess in a very roundabout way I am taking sides with others here and that is to say wait and see how you get on but if you have the best eyepieces for me it is madness not to have them sharp to the edge, these things are expensive and rarely show up secondhand but they only need buying once. As one of my fellow Mods has said the Mk1 is fine, I have owned both and did a compasion review which is in the Equipment section somewhere.

Alan

[swamp thing]

I agree Alan but as the OP said he was "delving into the world of astronomy" I took that as he was new to amateur astronomy and unlikely to be using ethos or similar quality eyepieces just yet.

Hence why I said wait and see how you get on.  

 

[John]

Before I had the 12" F/5.3 dob I had a 10" F/4.8. I used 100 degree eyepieces with that scope (Ethos) but didn't find the coma bothersome. It was there but not to the extent that it stood out each time I observed.

Imaging might be more exacting though.

 

[stepping beyond]

TC, I have a z10 f5/fl 1200 dob and 8 in. Orion imaging Newtonian astrograph @f3.9 with a fl 800mm ,  "

[Quote}
" allows a f3 parabolic to perform like an f12 without it , 15%{1.15x} magnification factor and since the wide field ep's I had were in my kit with the dob the  2 " 100* and SWA eps really tell the tale by improving there quality {tested} in both scopes . I weighed the option of purchasing the ethos and went with my {GUT} the model { vip-2010 visual/imaging Paracorr t2} dual function for it's versatility. I'm saying it has 3 functions 1.15x focal extender/ magnifier , visual , imaging  , TeleVue say dual because they recommend the TV line of top- notch eyepieces to be used but, when putting a quality ep in it made me a believer . No need to purchase more expensive wide field eps IMHO . The choice and money is yours ,  weigh the benefits vs price .

[faulksy]

hi tangocharlie and welcome to sgl

all good points above, but as you sound new to astronomy you probably won't know what coma is or have not experienced it and at your focal length i don't think you will detect it, than less you have a very keen eye and 100* eye pieces. just buy your scope, get it colimated and enjoy. report back when you have had a few sessions. good luck

[TangoCharlie]

Dear Fellow Astronomers,

Thanks for sharing your advice and expertise.  I will wait and see.  I am interested in lenses though that give me 82 degrees of AFOV.  I am guessing that these are more like the Naglers I have read about whether it is a Celestron Luminos or a Meade 5000.

Thank you so much for the help!

TC

[TheLookingGlass]

On 1/2/2017 at 06:31, alanjgreen said:

As far as Barlow is concerned, TV recommend you use a power mate with paracorr.

I used to own the GSO CC. When I added a barlow, then the eyepiece, the cantilever was ridiculously long. Not a big fan of that.

5 of us  did a shootout between the latest TV PC, and the GSO CC. Correction was exactly the same in both. The only thing the TV had over the GSO was the lever. If you parfocalize your eyepieces, the need for the lever becomes moot. 

After futzing with the CC and eyepieces, I prefer not to have one in there. The slight coma does not bother me at all since the action is always in the center. Some are more picky, and of course a CC / paracorr IS a must at f/4 or lower IMO. While the GSO CC *did* help a bit, it did not completely eliminate coma. I used the right spacing at about 75mm in between the field stop of the EP and the CC lens.

Cheers!