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Paracorr vs ES Coma Corrector

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#1 Kevdog

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Posted 24 April 2014 - 10:11 AM

I know the Paracorr II is THE one to get. But it looks like ES have come out with their own version. http://agenaastro.co...-corrector.html

So is the ES one any good for an f4.5 18" Obsession? What do I get for the extra $150 with the Paracorr? It looks like it is easier to tune.

Plus I was wondering, I have all ES82 eyepieces (30, 18, 11, 7). Would they all use the same setting in the ES, so I wouldn't have to switch anyway. I'm guessing no, since 2 are 2" and 2 are 1.25" and will be in the adapter?

Anyone used both and have any comments/pros/cons?

Thanks!

#2 OrdinaryLight

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Posted 24 April 2014 - 10:35 AM

I was tempted by the ES during the recent NEAF sale but some searching revealed that my focuser doesn't have the required 32mm+ of in-focus travel. Your Obsession probably has a fancier focuser than my Chinese Dob so it may not be an issue in your case.

#3 maakhand

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Posted 24 April 2014 - 10:50 AM

i think at f/4.5 you should be fine with regular paracorr. usually around 180~200 in used market.

#4 Darren Drake

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Posted 24 April 2014 - 10:59 AM

The folks at ES told me at the WSP that this one only has a 1.06X (I think) mag increase instead of the 1.15X from the TV. That alone makes this an interesting item....

#5 okieav8r

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Posted 24 April 2014 - 11:20 AM

i think at f/4.5 you should be fine with regular paracorr. usually around 180~200 in used market.


I agree. Unless one is getting a very fast mirror, the regular Paracorr will work just fine, for a lot less $$$.

#6 George N

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Posted 24 April 2014 - 11:54 AM

I would assume that the ES lens is a very good product, just based on their eyepiece efforts. Are they in people’s hands yet?

With the Paracoor II you get published results on how well it corrects coma (better than the original, but the improvement may not be needed) and a tunable top designed to work with Ethos eyepieces (earlier Paracoor won’t), and a lens group designed for removal for use in imaging. Also the machining quality is first rate, with two screws to hold in the eyepiece. The adjustment of the top is very smooth, which is great for actually focusing with it. It is on the heavy side.

At NEAF, TV had a new 3-inch Paracoor, and ES had an 8-inch carbon-fiber tube astrographic Newt with their coma reducer installed in the bottom of the focuser. It was actually a little cheaper than their 6” Mak-Newt.

#7 GeneT

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Posted 24 April 2014 - 07:46 PM

The ES might be fine, but if I were buying this item, I would get a Paracorr, a proven performer, with a long track record of success.

#8 Pinbout

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Posted 25 April 2014 - 08:13 AM

The folks at ES told me at the WSP that this one only has a 1.06X (I think) mag increase instead of the 1.15X from the TV. That alone makes this an interesting item....


and if you look at the chart they're suppose to be good down to the mid 3.whatevers.

and they have a lot more finer focusing helical top, but only a little more smoother.

https://www.youtube....h?v=mLwzqxgbkbI

#9 JimMo

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Posted 25 April 2014 - 09:52 AM

The folks at ES told me at the WSP that this one only has a 1.06X (I think) mag increase instead of the 1.15X from the TV. That alone makes this an interesting item....


and if you look at the chart they're suppose to be good down to the mid 3.whatevers.

and they have a lot more finer focusing helical top, but only a little more smoother.

https://www.youtube....h?v=mLwzqxgbkbI


Is there a quicker way to change settings on the ES? That would be an awful lot of turns to go from say a 21 or 17 Ethos to an 8 or 6 Ethos which have the widest setting difference on a PC2. Sounds like you's need barrel extensions and parfocalizing rings to get them set up so as not to spend the whole evening spinning the "tunable top" to change settings. :p

#10 Pinbout

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Posted 25 April 2014 - 10:06 AM

Is there a quicker way to change settings on the ES?



yeah use a motor. :foreheadslap:

#11 sixela

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Posted 25 April 2014 - 11:18 AM

Use parfocalisation rings. I think a manufacturer of parfocalisation rings bribed ES to design the top this way ;-).

#12 precaud

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Posted 25 April 2014 - 12:54 PM

Make sure you've got enough in-focus range to use the ES, it requires more than the Paracorr... more than the GSO CC too. It will not work with your typical metal tube Chinese dob, that knocked it out of consideration for me.

#13 Kevdog

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Posted 25 April 2014 - 04:27 PM

Well, any in-focus will knock it out for me. I'm already at the verge of in-focus problems. In fact I sold my 1.6x 2" barlow as I couldn't focus anything with it. I probably need to shorten the tubes as the JMI focuser the previous owner put on the scope is a bit taller than the original. I just don't have time to mess with it right now!

#14 Scott in NC

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Posted 25 April 2014 - 04:52 PM

The folks at ES told me at the WSP that this one only has a 1.06X (I think) mag increase instead of the 1.15X from the TV.


This may help to explain the reports that the ES requires a bit more in-focus than the TV.

#15 Starman1

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Posted 26 April 2014 - 12:52 AM

ES in-travel compared to eyepiece with focal plane at shoulder: 32mm.
TV in-travel: 14mm.
I dare say most dobs aren't going to have an extra 32mm of intravel.
Be prepared to cut your poles.

#16 Starman1

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Posted 26 April 2014 - 12:55 AM

I know the Paracorr II is THE one to get. But it looks like ES have come out with their own version. http://agenaastro.co...-corrector.html

So is the ES one any good for an f4.5 18" Obsession? What do I get for the extra $150 with the Paracorr? It looks like it is easier to tune.

Plus I was wondering, I have all ES82 eyepieces (30, 18, 11, 7). Would they all use the same setting in the ES, so I wouldn't have to switch anyway. I'm guessing no, since 2 are 2" and 2 are 1.25" and will be in the adapter?

Anyone used both and have any comments/pros/cons?

Thanks!

As with the Paracorr, if you find the perfect setting for just one of those, you freeze the focuser and focus using the top of the HRCC. The in-focus setting is the setting for the other eyepiece.
Obviously, this will be easier if your eyepieces are parfocal.
If, like my switch from a 21 Ethos to a 13 Ethos, the difference in setting is 0.7", be prepared for some unscrewing of the top.

#17 jpcannavo

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Posted 26 April 2014 - 03:44 AM

The folks at ES told me at the WSP that this one only has a 1.06X (I think) mag increase instead of the 1.15X from the TV. That alone makes this an interesting item....



Darren

Not sure, but it may be that Paracorr's magnification is the "cost" in their optical design that achieves a negligible introduction (i.e. less than the diffraction limit) of spherical aberration - a nice accomplishment for a paraboloid with a sub aperture coma corrector. Would be curious to know how the ES - with significantly less magnification - fares in this regard.

Joe

#18 sixela

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Posted 26 April 2014 - 04:22 AM

be prepared for some unscrewing of the top.


If you're like me, you'll give up and buy a 2" barrel extender and 2" parfocalisation ring for that 13mm Ethos...

#19 precaud

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Posted 26 April 2014 - 06:00 AM

ES in-travel compared to eyepiece with focal plane at shoulder: 32mm.
TV in-travel: 14mm.
I dare say most dobs aren't going to have an extra 32mm of intravel.
Be prepared to cut your poles.


I am still amazed that they put that design into production, eliminating, as it does, such a large percentage of the potential user base. Someone at ES didn't have their thinking cap on.

#20 Pinbout

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Posted 26 April 2014 - 07:47 AM

ES in-travel compared to eyepiece with focal plane at shoulder: 32mm.
TV in-travel: 14mm.
I dare say most dobs aren't going to have an extra 32mm of intravel.
Be prepared to cut your poles.


I am still amazed that they put that design into production, eliminating, as it does, such a large percentage of the potential user base. Someone at ES didn't have their thinking cap on.


I thought [but never tried] the paracorr II needs 19.5mm of in-travel.






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