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Tom TAdministrator

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Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: naglertized]
      #2177670 - 02/08/08 07:06 PM

Quote:

Tom,

Does the NP101 impart any color tonality, such as being "warm" or "cold"?




Hm. Interesting question.

IIRC, Nothing that really stands out. If I had to call it, I'd have to say the images seem just right for tone to me. For comparison, the FS128s I've looked through definitely seemed on the warmer side - this is nothing like that.

Quote:


Does color tonality differ between the NP series and the other TV APO's such as the 102?

Thanks




Boy, that's asking me to go back into the memory banks and retrieve an impression...



I don't recall a night and day difference, but the 102 *might* be a bit warmer. I *think* I recall the old SDF (NOT the NP) being a bit warmer than the 102 - but it could easily have been the eyepieces I was using at the time. I could easily be mistaken too. Memory is quite fallible with things like this, and it's nothing that makes a major impression. Unless it's side by side, I just kind of get used to the view and tend to think of whatever view I'm seeing as "normal".

I can compare the NP101 to my FS102 when I get a chance, but alas, I can't compare it to the TV102 any longer.

You'd do well to ask that on in our refractor forum or the TV group and seeing what other users have to say.

T


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naglertized
Carpal Tunnel
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Reged: 01/10/07

Loc: Jacksonville Florida
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2177718 - 02/08/08 07:31 PM

Tom, thanks for your quick response!

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Daniel Mounsey
Vendor (Woodland Hills)
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Reged: 06/12/02

Re: CN Report: The Tele Vue NP101 new [Re: peleuba]
      #2177906 - 02/08/08 09:12 PM

Quote:

Quote:



I confirmed this with a simple but all-telling star test, where I once compared a TV 101 with a TV102. The 102 won hands down and showed a level of SA correction < 1/8th wave ptv.







Harry,

I am sure Tom knows about Abberator...

I am quite comfortable using Abberator and make use of it regularly in my testing... But with all due respect, how fluent are you in performing the star test? Did you make use of colored filters to isolate the wave lengths of light - specifically Wratten 56, 58 and 8? If not, I will tell you its quite difficult to assign a wave front rating - as you have previously done - via the star test. Especially if your not isolating indidual wavelengths. Spherochromatic aberation will be the biggest issue and it will, most certainly, obscure the Fresnal pattern your trying to evaluate. And, I have not mentioned the presense of zones, edge issues, inhomogenity in the glass etc. All will have a detrimental effect and all are unrelated to Spherical Aberation.

The bottom line is that star testing is easy to perform but difficult to interprate even for folks who have a lot of experience. I never, ever, place final judgment on a lens unless I test it indoors, outside and then let an optical genius friend put it through its paces for a couple of nights.

I have owned a TV102 and three NP101's and have been able to evaluate each on a fairly sophisticated optical bench as well as in the field. My TV102 was perhaps 1/6 wave in GREEN light but it was the Spherochromatic abberation that drove me nuts. I would like to know more about the tests you performed on the 101 you had access to .

All three samples of the NP101 I owned had good Spherical corretion - one was nearly perfect in green light. The other two were very good. My biggest objection was that one sample had a very small central zone which wreaked havoc on the star test but was not visble in-focus.

If you could let us know specifics to your testing it would be interesting. I have found that performing a 5 minute star test one night on a scope then, the next day, trying to match it up to Abberator is not really valid in assigning wave front values. Too many variables (other then sperical correction) need to be accounted for and evaluated.





This is a very good post and a valid one at that. I think it's important to note that no two scopes are exactly alike and it's proved to be so during a ton of visual tests we conducted. Take in mind that we're talking subtle differences that most would never even notice. It's like two of the exact same guitar. If a purist gets a hold of it, they will have a subtle difference in sound and rightly so. This is not to imply bad quality control by any means. Like I said, it's on a very high level of scrutiny. I'm kind of limited on what I'm allowed to share.

Edited by Daniel Mounsey (02/09/08 12:47 PM)


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mattiewolfhound
sage


Reged: 02/12/06

Re: CN Report: The Tele Vue NP101 new [Re: Daniel Mounsey]
      #2178048 - 02/08/08 10:08 PM

Hi Tom,

Great report. Thanks.

BTW, you wouldn't be thinking about selling your TV 101, would you?

Let me know!

Terrence


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djh
sage


Reged: 05/03/06

Loc: NY
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2178143 - 02/08/08 11:15 PM

Tom, I really enjoyed your article!

I was wondering if you could comment on the FocusMate driver... can it stay attached when you put the scope back in the hard shell case, like the StarBeam RDF? Al demonstrated it for me one day at TV when I took my TV-85 in for cleaning. Really sweet!


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Tom TAdministrator

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Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: djh]
      #2178589 - 02/09/08 08:19 AM

Quote:

Tom, I really enjoyed your article!

I was wondering if you could comment on the FocusMate driver... can it stay attached when you put the scope back in the hard shell case, like the StarBeam RDF? Al demonstrated it for me one day at TV when I took my TV-85 in for cleaning. Really sweet!




Thanks!

The driver can stay attached, but you should unclip the control box. Not a big deal as it uses a standard phone type clip.

T


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Tom TAdministrator

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Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: docmusolf]
      #2178592 - 02/09/08 08:22 AM

Quote:

nice article. always enjoy the read. I am not personally able to appreciate what this scope has to offer. However the view of comet holmes through the ethos was amazing. to all that would like other reviews i would suggest that you call those manufactures and ask them to send Tom more scopes. From my knowledge of how this woorks is that he will review what is sent to him. No scope equals no review. I to would like to read more reviews so i have more reasons to sit around smoke cigars sip on scotch and dream about astronmoy when i a freezing in the middle of winter. So lets all make it a point to call our favorite relescope company and ask them to send more scopes for review.




Yah, that's pretty much it. If folks want something reviewed they have to send it. About once a year we do a letter to manufacturers to remind them. We're about due. But they don't have to wait for that.

T


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ckwastro
Pooh-Bah


Reged: 11/23/05

Loc: Tempe, AZ
Re: CN Report: The Tele Vue NP101 new [Re: docmusolf]
      #2178704 - 02/09/08 09:47 AM

Quote:

I to would like to read more reviews so i have more reasons to sit around smoke cigars sip on scotch and dream about astronmoy




Yep, if you can't be at the eyepiece, it doesn't get any better than that!!


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Tom TAdministrator

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Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: JoeBftsplk]
      #2179380 - 02/09/08 03:27 PM

Quote:

Paul & Tom,
Thanks for the responses. I'd guess the third (rightmost) image is closest to what I see. However, to Tom's point, it doesn't seem to be an issue all the time. That, plus the scope and diagonal went back to Televue with the specific complaint and they could find no evidence of astigmatism. Thanks for verifying that spherochromatism is not likely to be the cause. Could simply be conditions like Tom said.

I recently installed a Feathertouch focuser on the TV102. Maybe that will help on difficult nights. Thanks to our NY snowbelt weather I haven't had a chance to try it yet.

Would like to go side-by-side with an NP101 or maybe a TSA102 sometime. Might give me a better feel for how the TV102's performing. The FS78 is almost always a perfect gem, but that may be due to its size more than anything else.
Bob




I've been thinking about this a bit more. Paul, I have a minor issue with your aberrator graphic because it assumes that TV would let a scope out of the factory with ½ wave astigmatism. I know that wasn't the statement you were making, but it got me thinking. Given the QC they do on every scope, I just can't see an errror that gross sneaking through. So lets back up a bit and do some more complete and basic triage.

First some initial conditions/thoughts before you test:

1) Check the seeing using the pickering scale.

http://uk.geocities.com/dpeach_78/pickering.htm

Don't expect to much unless the seeing is good or better, and be aware that seeing can change.

2) Ensure that the scope is properly cooled.

3) Make sure that your own vision is up to par - no colds, dry eyes, allergies etc. It also helps to be well rested and healthy.

4) Have a couple of different eyepieces on hand. Simpler is often better (although naglers should be fine - the key is you want well corrected eyepieces that won't add any of their own aberrations to the test).

5) Remember, when we look through a scope, we're looking at an optical train - target, atmosphere, objective, diagonal, eyepiece, eyes, brain - not just a telescope objective. ALL of these things affect the final image. Too often we are very quick to blame one or the other – even those of us who really know better.

Realize that Paul's aberrator shots are for in focus astigmatism. This can creep in via a couple of different things. Rather than look for it in focus the best way to spot it is to roll the scope across focus. (There are other things that can look like astigmatism in focus that aren't – although there shouldn't be any with this particular setup.) When you roll across focus, instead of a round out of focus star, you'll see an elliptical patch. When you cross focus, the ellipse will change orientation 90 degrees.

When you see the figures that resemble what Paul posted, what magnification are you using? This is pretty important, because if it's visible only at lower powers or large exit pupils what you're most likely seeing is the astigmatism in your own eye.

Some things to try and consider:

1) Try a side by side with the FS 78 at comparable magnifications AND exit pupils (that's the important part I think here) and see if the problem still exists. When testing, be sure to pick a star at least 45 degrees high to minimize the effect of the atmosphere on it.

Don't do them on different nights for a couple of reasons: 1) if you're getting seeing which compounds this, it could be better one night and worse the next 2) sadly memory is really a pretty flaky thing to go by. It's really best to have both there at the same time.

2) Sad fact of life, as we age our eyes get worse. I'm thinking if you see this at large exit pupils, it may be astigmatism all right, but it's not the fault of the manufactured components. It could well be your eyes - even if you have little to no daytime astigmatism. Personally, I have around a 1/4 diopter when my eyes are fully dilated - none during normal daylight viewing. For me, this starts to show up with exit pupils over 5mm. Under that I don't see any.

3) If you do see astigmatism, try rotating the diagonal, the eyepiece and finally your head. Note if the orientation of the astigmatism changes with any of these. If it does (and I suspect it may) then you have found at least part of the culprit.

I suspect the problem here is a combination of conditions and eyesight, but the eyepiece may also play a factor. If TV says there's no astigmatism being induced by the scope or diagonal, then I'd feel pretty safe in ruling that out and look elsewhere.

Tom T.


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sixela
Postmaster
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Reged: 12/23/04

Loc: Boechout, Belgium
Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2179383 - 02/09/08 03:29 PM

Quote:

But in essence, the star test is easy to judge.




No, it's not. Certainly not on scopes whose designs have small low order spherical aberrations and larger high order spherical aberrations (that change the out of focus star image but have little impact on the image in focus).


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jonnyastro
Carpal Tunnel
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Reged: 02/14/06

Loc: Pittsburgh, PA
Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2179411 - 02/09/08 03:46 PM

Don"t seeing conditions also factor into complicating a star test?

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Tom TAdministrator

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Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: jonnyastro]
      #2179431 - 02/09/08 03:54 PM

You need good seeing to even attempt one.

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V.A.
sage


Reged: 05/14/05

Loc: Ontario, Canada
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2179618 - 02/09/08 05:26 PM

an artificial star test eliminates seeing problems,makes judging a star test alot easier and accurate.
for testing eyepieces i'm thinking of getting a tv60is as a eyepiece test rig (among many other reasons), i can test eyepieces indoors, since the artificial star does'nt have to be very far.


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Dirtyharry
member


Reged: 11/01/07

Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2179627 - 02/09/08 05:31 PM

Quote:

Quote:

But in essence, the star test is easy to judge.




No, it's not. Certainly not on scopes whose designs have small low order spherical aberrations and larger high order spherical aberrations (that change the out of focus star image but have little impact on the image in focus).




Yes it is, as I have explained earlier!!!

Harry


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mattiewolfhound
sage


Reged: 02/12/06

Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2179725 - 02/09/08 06:33 PM

Tom or Anyone Else,

Can you please help me with the differences between the TV 101 and 101 NP? I didn't realize there were two different ones until I went looking for a TV 101. I'm strictly a visual oberserver. What performance differences would I expect?

Which would you recommend for a visual observer?

Thanks
Terrence


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Tom TAdministrator

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Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: mattiewolfhound]
      #2179808 - 02/09/08 07:17 PM

Hi Terrence,

The NP101 replaced the TV101 several years ago.

From what I understand the NP uses different glasses, has different radii and different spacings. It also uses current coating technologies where the coating is tuned to the particular glass.

The TV petzvals have been an evolution, each improving performance over the last.

With the NP (VS the TV101) you can expect improved color correction and better high power performance.

As per recommendation, I think a discriminating observer would find the NP to be better for lunar and planetary performance, but the TV101 is still a superb optic (and can probably be had for a real bargain now).

T


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Downward Bound
Adrenaline Junkie
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Reged: 03/29/06

Loc: Seattle
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2179954 - 02/09/08 08:41 PM

Great article Tom! Thank you for the time you took to test this scope, write your review and then to promptly and politely continue to respond to all the inquiries!!! I very much appreciate the investment of your time for the benefit of us all!!

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Tom TAdministrator

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Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Downward Bound]
      #2180373 - 02/10/08 12:44 AM

Hi Bill,

Thank you. It's truly gratifying to know that people appreciate it.

I really value your comment.

T


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sixela
Postmaster
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Reged: 12/23/04

Loc: Boechout, Belgium
Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2180537 - 02/10/08 04:26 AM

Quote:

Quote:


No, it's not. Certainly not on scopes whose designs have small low order spherical aberrations and larger high order spherical aberrations (that change the out of focus star image but have little impact on the image in focus).




Yes it is, as I have explained earlier!!!

Harry




You've stated it, but that doesn't make your assertions true. In particular in the presence of design higher order spherical aberration.

Some designs will generate unsymmetrical star test images at both sides of focus but will perform very well in focus; you *can* identify this by taking star test images at many different distances from best focus and doing very thorough analysis (to discriminate between the different Zernike polynomials, i.e., aberration types) or by doing a Roddier test, but none of this is simple.

Let me state this another way: neither Roland Christen and Markus Ludes think nor the late Thomas Back thought that star testing a refractor with more than two elements was particularly simple (not even when light is filtered to only show the wavelength designed to show no spherochromaticism), and others have echoed the same sentiments in this thread.

So either you assertion that it's simple is true and they all don't know what they're talking about, or your view of the world is simplistic and your brain is playing tricks on you to avoid acknowledging anything that doesn't fit your current cognos.

But this is really off-topic: if you want a discussion about this, the ATM and Optics forum is the place for it, or you can try Astromart if you feel like getting spanked by Roland himself.


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Dirtyharry
member


Reged: 11/01/07

Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2180596 - 02/10/08 06:36 AM

[


Let me state this another way: neither Roland Christen and Markus Ludes think nor the late Thomas Back thought that star testing a refractor with more than two elements was particularly simple (not even when light is filtered to only show the wavelength designed to show no spherochromaticism), and others have echoed the same sentiments in this thread.

Hi,

I have a doublet TV 102, so what's your issue?

Harry


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