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Paracorr 2: First Light Tonight....

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#1 Paul R.

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Posted 08 October 2018 - 08:35 PM

The skies have FINALLY cleared enough for me to try out the new Parcacor 2 in my 20"  First impressions are very nice...  didn't think at f5 it would make that much of a difference, but it does...  More stars visible...and contrast has improved across the entire field.  Of course stars are pinpoint to the field stop!  Cool...

 

One thing I've noticed, and maybe it's just me, but using Ethos eyepieces it 'feels' as seems as if eye relief has improved somewhat as well.  It's really noticeable using the 17.3mm Delos eyepiece, almost to the point of black outs....weird...

 

After I wrote this originally, I went back outside, fighting clouds, and concentrated just using the 21E with and w/out the Par2.  It really does*appear* to improve the eye relief slightly...if I had to estimate I would say it adds about 1mm or slightly more.  One thing's for sure, I will not be using that eyepiece again without it.  Aside from the superior view, it's just more comfortable to use..No wonder why these things cost so much!


Edited by Paul R., 09 October 2018 - 09:29 AM.


#2 TOMDEY

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Posted 08 October 2018 - 09:21 PM

Hi, Paul; that's quite possible, even likely... bet you're right!

 

I know how to measure that stuff and have the equipment here to accurately do it. But I left the Paracorr 2 up at the observatory, 1000 ft up the hill from here. Can probably do that tomorrow. 20-inch f/5. That's all I need to know. I can then characterize where your exit pupil is with and without the Paracorr 2, and even confirm operational magnification both ways.

 

Many/most people don't realize that pupils, eye relief, and magnifications shift, depending on how the scope/eyepiece are configured. So Yes, there is a lot more going on than just a change in F# and correction of Coma. The Good News (for you)... I think the Paracorr design is optimized for something like your focal length (100 inches) and faster speed... so, as you have noticed... performance is excellent!

 

If I get around to it, I will measure the pupil shift, and see how it agrees with what you have noticed. Got me curious.

 

The instrument is Soviet... and like most all Soviet hardware... a bit bare bones... but it WORKS wonderfully! I give them a LOT of credit for making stuff that simple WORKS!  Tom

 

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#3 TOMDEY

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Posted 08 October 2018 - 09:23 PM

Ummm... I can measure it for the Ethos eyeps too...



#4 Mike W.

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Posted 09 October 2018 - 07:19 AM

Would this also be true of the ES HRCC?

 

I've been of recent trying to decide whether to retire the ES and get a ParaCorr, but just don't want to give up the helical focus unit on top of the HR.

I've gone through quite a bit to get my eyepieces all para focal'd for this unit, but I'm pretty sure that manufactures have the skills to make sure that their eyepieces perform 100% with their own accessories, 98% with other manufacturer's components.


Edited by Mike W., 09 October 2018 - 07:34 AM.


#5 Paul R.

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Posted 09 October 2018 - 11:23 AM

Hi, Paul; that's quite possible, even likely... bet you're right!

 

I know how to measure that stuff and have the equipment here to accurately do it. But I left the Paracorr 2 up at the observatory, 1000 ft up the hill from here. Can probably do that tomorrow. 20-inch f/5. That's all I need to know. I can then characterize where your exit pupil is with and without the Paracorr 2, and even confirm operational magnification both ways.

 

Many/most people don't realize that pupils, eye relief, and magnifications shift, depending on how the scope/eyepiece are configured. So Yes, there is a lot more going on than just a change in F# and correction of Coma. The Good News (for you)... I think the Paracorr design is optimized for something like your focal length (100 inches) and faster speed... so, as you have noticed... performance is excellent!

 

If I get around to it, I will measure the pupil shift, and see how it agrees with what you have noticed. Got me curious.

 

The instrument is Soviet... and like most all Soviet hardware... a bit bare bones... but it WORKS wonderfully! I give them a LOT of credit for making stuff that simple WORKS!  Tom

 

Thanks dude!  Let me know what you come up with.  I edited my original post with my thoughts after doing more with and wout comparisons...  as I said, to me it appears there is an increase; a modest one, but enough to recognize.  Awesome views though...even despite the less then perfect conditions...  What's frustrating is here in northern Illinois we are going into the cloudy, cold months...opportunity to use the scope becomes minimal.  In this part of the country you really spend your life waiting for decent observing conditions...especially us workin' folk.  They usually happen maybe once or twice a year AT BEST... sucks.  Thanks again.



#6 Starman1

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Posted 09 October 2018 - 01:47 PM

It is likely to be the Barlow effect that changes the eye relief, much in the same way a barlow also increases eye relief in an eyepiece.

IF that conjecture is correct, then the ES HRCC would have less effect since it magnifies only 1.06x versus the 1.15x of the Paracorr.



#7 Spartinix

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Posted 09 October 2018 - 03:32 PM

Welcome to the annoyed-by-coma-at-F5 club Paul grin.gif. I was hesitant too to get one for my F5... turns out it does indeed make a nice difference. I've only been able to use it a dozen or so times.. My last wow moment was M22 last night with the Ethos 13... without.. and then with.. pinpoint stars all around and a nice flat field!


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#8 Paul R.

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Posted 09 October 2018 - 06:11 PM

Welcome to the annoyed-by-coma-at-F5 club Paul grin.gif. I was hesitant too to get one for my F5... turns out it does indeed make a nice difference. I've only been able to use it a dozen or so times.. My last wow moment was M22 last night with the Ethos 13... without.. and then with.. pinpoint stars all around and a nice flat field!

 

Nice, *modest* boost in magnification too...plus, as stated, for me anyway, slightly better eye relief.  The next time you use your scope, especially with the Ethos eyepieces, tell me if you think ER improved at all.  For me it did, slightly, but still, apparent.



#9 Starman1

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Posted 12 October 2018 - 03:38 PM

OK,

I checked with TeleVue:

The P2 is essentially telecentric, so adds no eye relief to any eyepiece.

IF any change occurs at all, it might be a very slight reduction in eye relief.

Go figure.


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#10 Spartinix

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Posted 13 October 2018 - 01:22 AM

Ah... I haven't noticed any small difference in er anyway. Next time out I'll try seeing what you mean though Paul.



#11 Jon Isaacs

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Posted 13 October 2018 - 06:48 AM

OK,

I checked with TeleVue:

The P2 is essentially telecentric, so adds no eye relief to any eyepiece.

IF any change occurs at all, it might be a very slight reduction in eye relief.

Go figure.

 

Even a 1.15x Barlow would add very little eye relief.  The increased eye relief with a Barlow is not 1:1 by any means, a 2x Barlow does not double the eye relief.

 

Jon


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#12 25585

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Posted 13 October 2018 - 01:14 PM

The longer focal length an eyepiece has, the greater effect on increasing eye relief an ordinary Barlow has, in general. Perhaps the focal length of a Barlow makes a difference too.

 

 


Edited by 25585, 13 October 2018 - 01:16 PM.


#13 Starman1

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Posted 13 October 2018 - 01:36 PM

Except in this case, per the designer, the P2 has no barlow effect on the eyepiece's eye relief.

I was told that if it had any effect, it would be to shorten the eye relief.


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#14 Paul R.

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Posted 14 October 2018 - 04:35 PM

Except in this case, per the designer, the P2 has no barlow effect on the eyepiece's eye relief.

I was told that if it had any effect, it would be to shorten the eye relief.

 

 

Then I wonder why I experience a difference?  I will check it out again as soon as the skies clear...and I have no work the next day...GOOD LUCK WITH THAT...lol  Seriously though, I do need to check this again...  Last Monday I did 4 comparisons and to me, the eyepiece seemed easier to use...the sensation anyway...I thought it might have been the slight magnification factor...which is there, but it's more then that. 



#15 Starman1

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Posted 14 October 2018 - 04:39 PM

Well, the P2 is a mild field flattener, and that could have an effect on ease of use.



#16 25585

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Posted 17 October 2018 - 05:30 PM

Except in this case, per the designer, the P2 has no barlow effect on the eyepiece's eye relief.

I was told that if it had any effect, it would be to shorten the eye relief.

Not noticed that, and I sincerely hope it's not true!!!



#17 Jon Isaacs

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Posted 18 October 2018 - 02:04 PM

Not noticed that, and I sincerely hope it's not true!!!

 

We're splitting hairs here . The difference in eye relief one way or the other is going to be miniscule.  If you hadn't notice it , no wonder .

 

Jon


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#18 earlyriser

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Posted 19 September 2019 - 06:57 AM

OK,

I checked with TeleVue:

The P2 is essentially telecentric, so adds no eye relief to any eyepiece.

IF any change occurs at all, it might be a very slight reduction in eye relief.

Go figure.

I had my paracorr 1 out for a brief test this morning. My initial impression is that it reduces eye-relief on the Nagler 31 enough that I can no longer see the whole field of view while wearing glasses. 


Edited by earlyriser, 19 September 2019 - 06:57 AM.

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#19 earlyriser

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Posted 19 September 2019 - 07:02 AM

We're splitting hairs here . The difference in eye relief one way or the other is going to be miniscule.  If you hadn't notice it , no wonder .

 

Jon

I noticed it on the P1 right away. The eye relief of the 31 Nagler is marginal for me when wearing glasses, so even a small reduction is enough for me to notice. Whether the P2 has a similar effect, I can't say.


Edited by earlyriser, 19 September 2019 - 07:03 AM.

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#20 25585

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Posted 19 September 2019 - 07:33 AM

I noticed it on the P1 right away. The eye relief of the 31 Nagler is marginal for me when wearing glasses, so even a small reduction is enough for me to notice. Whether the P2 has a similar effect, I can't say.

Maybe an improvement made for the PC2 fixed that.



#21 hakann

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Posted 19 September 2019 - 12:08 PM

It do sound odd that more glass added will show you more stars.

And this is a very cheap products as well, not something in extreme quality.

Take a 20" a f/3.5 and FL will change so ex E13 less is 135X and with is 155X.

You might detect more stars, but...

Anyway, all this is in the end about Your eye in the EP.

 

Most scope owners I borrow out my Ethos or Nikon HW and the Paracorr in focals at f/4 to f/5 go back to their own Delos/Naglers etc and no Paracorr as they prefere it, and this is 9 of 10.

 

-Actually I start to like the Delos better myself after use Ed's Elivra at OSP.

Next for me is to test some Delites from Don.



#22 25585

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Posted 19 September 2019 - 12:42 PM

OK,

I checked with TeleVue:

The P2 is essentially telecentric, so adds no eye relief to any eyepiece.

IF any change occurs at all, it might be a very slight reduction in eye relief.

Go figure.

Should be easy enough to measure an eyepiece's eyepoint distance with & without a PC attached, using flashlight, paper & ruler.  


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