Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Announcements and News >> Discussion of CN Articles, Reviews, and Reports

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | (show all)
Tom TAdministrator

*****

Reged: 02/26/02

CN Report: The Tele Vue NP101
      #2167880 - 02/04/08 04:38 PM

The Tele Vue NP101

Post Extras: Print Post   Remind Me!   Notify Moderator  
Keith Howlett
Pooh-Bah
*****

Reged: 03/06/07

Loc: Northumberland, UK
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2167982 - 02/04/08 05:17 PM

Tom,

An excellent review, thank you!

Keith


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jim7728
Postmaster
*****

Reged: 04/10/05

Loc: Stoop Landing Observatory, NYC
Re: CN Report: The Tele Vue NP101 new [Re: Keith Howlett]
      #2168082 - 02/04/08 06:00 PM

Great article and such a privilege to read it for "free" on Cloudy Nights.

I'd love to own a NP-101, but do feel fortunate to have the older Genesis SDF version.

Thanks for the fun and interesting read, sir!


Post Extras: Print Post   Remind Me!   Notify Moderator  
John Kocijanski
Carpal Tunnel
*****

Reged: 08/22/03

Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2168216 - 02/04/08 06:50 PM

Great review. I had a couple of opportunities look through one a while back. The views made me realize what all the hoopla over apos was all about. How does it compare to the TV 102 as far as performance?

Post Extras: Print Post   Remind Me!   Notify Moderator  
naglertized
Carpal Tunnel
*****

Reged: 01/10/07

Loc: Jacksonville Florida
Re: CN Report: The Tele Vue NP101 new [Re: John Kocijanski]
      #2168227 - 02/04/08 06:55 PM

Awesome article Tom, makes me treasure my lil ole Pronto even more ( I can still get spacers! ). It's clear tonight, I know where I'll be.

I especially loved the inset of behind the scenes of TV.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Doug D.
Carpal Tunnel
*****

Reged: 08/23/05

Loc: Virginia
Re: CN Report: The Tele Vue NP101 new [Re: naglertized]
      #2168242 - 02/04/08 07:03 PM

Wonderful review Tom - I suppose I am biased because I own one but to me, your review simply affirms what I knew to be true already. The NP101 is just about the right "balance of everything" I need in a portable APO (e.g., performance, versatility, weight, form factor, quality build). Did I mention performance?

Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: John Kocijanski]
      #2168309 - 02/04/08 07:34 PM

Thanks for the comments guys. I've been fortunate to use a fair amount of truly superb gear over the last few years, and the TV products are right up there the very best of them. They have always satisfied.

Quote:

Great review. I had a couple of opportunities look through one a while back. The views made me realize what all the hoopla over apos was all about. How does it compare to the TV 102 as far as performance?




Hi John,

Years ago I bought a TV102 - for various reasons, I figured it was the best option for me at the time - with cost no object. A while back Al and I were both speakers at the Apollo Rendezvous and had the opportunity to do a little observing together out at their club site. He put me on to the NP101 that night. He convinced me that a number of the myths I'd heard were really just that - myths, and it was a really superb design. Further, he made a convincing argument as to why I should use it as a platform for eyepiece testing.

Well, some time passed, and the opportunity came up last year. Since then I've been using it a *LOT*, and there's not much the TV102 can do that the NP can't. The exceptions are binoviewing (the new TV102IIS is great in that regard), and saving some extra space in your wallet to help with that ethos purchase. The fields are flatter, the wide views are wider, and the NP even handles power better - showing no CA, whereas the TV102 shows a bit at magnification.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
stevecoe
"Astronomical Tourist"
*****

Reged: 04/24/04

Loc: Arizona, USA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2168606 - 02/04/08 09:35 PM

Tom;

I have had the pleasure of observing with Al Nagler twice, once at TSP and last year at Riverside. I find that I agree completely with all the folks who say he is a true gentleman. Not to mention one of the best optical designers in the world today. I have been lucky to enjoy his company while viewing the sky.

I am not at a place where I can afford an expensive refractor at this point, but when I am, the NP 101 will be first on my list.

Clear Skies;
Steve Coe


Post Extras: Print Post   Remind Me!   Notify Moderator  
alanon
Nobody tells me anything
*****

Reged: 06/29/07

Loc: Las Vegas
Re: CN Report: The Tele Vue NP101 new [Re: stevecoe]
      #2168743 - 02/04/08 10:34 PM

Ok. You have me drooling! I am starting to save my pennies now. Very nicely written article Tom.

Post Extras: Print Post   Remind Me!   Notify Moderator  
NukenGeek
super member
*****

Reged: 12/28/06

Loc: Richland, WA
Re: CN Report: The Tele Vue NP101 new [Re: alanon]
      #2168951 - 02/04/08 11:52 PM

Great review Tom. I had been considering a variety of refractors for a while, trying to find one that would allow me to use the full capability of the SBIG imager I recently bought. I ordered the NP101is on Friday for many of the same features you pointed out in your review. It cost a lot more than I had intended to spend, but I decided it was worth it. I feel relieved to have my investment vindicated by someone with your level of experience. Now I just have to be patient and wait for it to arrive. (Not easy!)

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: CN Report: The Tele Vue NP101 new [Re: alanon]
      #2168960 - 02/04/08 11:59 PM

Quote:

Ok. You have me drooling! I am starting to save my pennies now. Very nicely written article Tom.




I agree... Very nicely written...

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
MacRoberts
sage


Reged: 08/25/05

Loc: Redlands, CA
Re: CN Report: The Tele Vue NP101 new [Re: Jon Isaacs]
      #2169012 - 02/05/08 12:33 AM

Well done, Tom. So well it made me second guess (for a second, anyhow) whether I should have gotten the NP-101 instead of the 127. One thing is for sure, the 101 is even more portable than my 127 and can do most everything it can do.

Thanks for your significant and ongoing contributions to this community.


Post Extras: Print Post   Remind Me!   Notify Moderator  
goober
member


Reged: 12/31/07

Loc: Victoria, Australia
Re: CN Report: The Tele Vue NP101 new [Re: MacRoberts]
      #2169040 - 02/05/08 12:58 AM

I enjoyed your review, Tom, especially the tour through the Tele Vue establishment.

I agree about the narrow focus zone. I initally put a Tele Vue Focus Lever on mine, but eventually upgraded to the FocusMate. It made a wonderful scope even better.

If I had one problem with the scope (more a problem with me, I guess!), is I use a Starbeam, and a 24mm Panoptic as a 3 degree FOV finder eyepiece. It gets a bit confusing star hopping with the L/R view reversed via the diagonal. I'm torn between teaching my brain to mirror image the view, or put an actual finderscope on it!

Tom, I'd be very interested if you could draw on your experiences and suggest a dream set of eyepieces for this scope. Say, three eyepieces and a barlow? I want to know how much better it could be


Post Extras: Print Post   Remind Me!   Notify Moderator  
Madsen
super member


Reged: 05/01/07

Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2169084 - 02/05/08 01:46 AM

Very nice review

Have anyone compared the NP101 and the Takahashi FSQ?

Søren


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mike Clemens
Frozen to Eyepiece
*****

Reged: 11/26/05

Loc: Alaska, USA
Re: CN Report: The Tele Vue NP101 new [Re: Madsen]
      #2169118 - 02/05/08 03:09 AM

Enjoyed the review, thank you.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Dirtyharry
member


Reged: 11/01/07

Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2169220 - 02/05/08 06:39 AM

Hello,

Nice advertisement for Televue! Is this really a meaningful review? Sounds lke Tom T. is working for the company Personally having looked through several Petzval designs in the Nagler line,I find the simpler TV 102 to be a better beast for the visual observer. And there's plenty of seasoned obsevers out there who'll wholeheartedly agree with me! Just my 2 cents.

Harry.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2169263 - 02/05/08 07:51 AM

Quote:


Hello,

Nice advertisement for Televue! Is this really a meaningful review? Sounds lke Tom T. is working for the company Personally having looked through several Petzval designs in the Nagler line,I find the simpler TV 102 to be a better beast for the visual observer. And there's plenty of seasoned obsevers out there who'll wholeheartedly agree with me! Just my 2 cents.

Harry.





Hi Harry,

First off, welcome to CN! A couple of words of wisdom - if you stick around here for very long, you'll probably learn that although it's easier on the forums (because many use a handle instead of their names) libel still isn't considered to be good form. Calling someone a shill is just plain poor behavior. We're not SAA and we put a large emphasis on being civil to each other. Reasoned disagreement is one thing. Insults and aspersions are another. Lets keep it to disagreement, eh?

So lets put that aside and start fresh.

FWIW I got a chuckle out of your post. You see, I completely understand your opinion on the TV102 because for many years, it was one I shared.

I owned a TV102 for 5-6 years, and it was my most used telescope during that time frame. I've also owned a Genesis SDF and had occasion to use a TV101 (along with a couple of other petzval designs). As I alluded to in the article, there was a time that I made similar arguments about the suitability of the doublet to the (earlier) petzvals for the visual observer - in fact, if you take a look at some of my old postings on the TV group, I was quite the proponent of the TV102. Paul L and I used to really get into it over the perceived advantages and disadvantages of the two scopes, so if you go back and look at those old posts, you'll find I was one of those "seasoned observers" who agreed with you.

But after using the NP for a year I have to admit that Paul was absolutely correct in this and I was wrong. The NP is a different beast than the TV101 or the Genesis SDF, and it really is a step up from the TV102.

Tom T.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: goober]
      #2169268 - 02/05/08 07:57 AM

Quote:


Tom, I'd be very interested if you could draw on your experiences and suggest a dream set of eyepieces for this scope. Say, three eyepieces and a barlow? I want to know how much better it could be




Hi Goober -

If I had to pick just three, it would be the 31 Nagler t5, the 13mm Ethos, and the 2-4 zoom. I'd also pick the Antares 1.6x or TV 2x barlows.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: MacRoberts]
      #2169269 - 02/05/08 07:57 AM

Quote:

Well done, Tom. So well it made me second guess (for a second, anyhow) whether I should have gotten the NP-101 instead of the 127. One thing is for sure, the 101 is even more portable than my 127 and can do most everything it can do.

Thanks for your significant and ongoing contributions to this community.




Hi Jim,

Thank you! And thank you to everyone else who contributed civil comments, they are appreciated.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Madsen]
      #2169310 - 02/05/08 08:27 AM

Quote:

Very nice review

Have anyone compared the NP101 and the Takahashi FSQ?

Søren




Hi Soren, the Q is a fine scope - and one that I gave strong consideration to myself. The thing that stopped me - with the first Q, focus travel was very limited. The scope was really intended more as an astrograph from what I was given to understand. The new Q appears to be a bit better in this respect, but most people seem to be using them as astrographs again. I hope to get the opportunity to use one of the New Q's before too long, they sure look like a sweet telescope.


Post Extras: Print Post   Remind Me!   Notify Moderator  
ac2005
member


Reged: 11/04/07

Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2169526 - 02/05/08 10:16 AM

Excellent...thoroughly enjoyed reading it...thank you for sharing insight on the tv facility.

Regards
AC


Post Extras: Print Post   Remind Me!   Notify Moderator  
ckwastro
Pooh-Bah


Reged: 11/23/05

Loc: Tempe, AZ
Re: CN Report: The Tele Vue NP101 new [Re: ac2005]
      #2169560 - 02/05/08 10:31 AM

Tom,

As always, excellent review, thank you! Darn near picked up the phone and called TV so I could have a "His & Hers " pair of 4"(ish) APO's at home. Especially since my wife confiscated the AP as her own

Seriously though I used a friend's on & off for a couple years and I completely agree with your assessment of it's performance - excellent instrument.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Dirtyharry
member


Reged: 11/01/07

Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2169561 - 02/05/08 10:31 AM



The NP is a different beast than the TV101 or the Genesis SDF, and it really is a step up from the TV102.

Tom T.





Hi Tom,

I'm afraid we'll have to agree to disagree! The NP101 might well have better colour correction, but there are many more aberrations to consider than this and the TV 102, being a doublet at f/8.6 means that most of these other imperfections are reduced even further than they could be at f/5.4. 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. The 101 was more like 1/5th wave, which is enough to take the edge off fine planetary detail. Have a look at the Aberrator freeware where it compares a typical petzval 4" f/5.4 to that of a 4" f/8.6. That's more or less what I have experienced. I doubt if a typical NP101 would do a lot better in this respect.
The extra $1000 for the NP101 gets you increased portability, a slightly wider field of view at low power and excellent field flatness for astrophotography. But it DOES NOT, IMO, translate to better sharpness and contrast (irrespective of the kinds of coatings they employ).
Harry.


Post Extras: Print Post   Remind Me!   Notify Moderator  
dtsmith
scholastic sledgehammer
*****

Reged: 03/22/06

Loc: Lafayette, IN
Re: CN Report: The Tele Vue NP101 new [Re: ac2005]
      #2169576 - 02/05/08 10:41 AM

I thought it was a great review Tom, although as an owner, I'll readily admit that I am biased. One of the things I really like about this scope is the fact the case doesn't require you to disassemble the scope to store it. Just remove the eyepiece, pop in the dust covers and put it away with the diagonal and clamshell/starbeam attached. I noticed in the pictures that the Focusmate and driver appear to be quite large. Does the size of the Focusmate create problems when using the case?

Post Extras: Print Post   Remind Me!   Notify Moderator  
ScottAz
Fleet Navigator
*****

Reged: 02/06/05

Loc: Kenosha, Wisconsin
Re: CN Report: The Tele Vue NP101 new [Re: dtsmith]
      #2169584 - 02/05/08 10:47 AM

Fantastic! (As always.) Thanks, Tom!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2169587 - 02/05/08 10:48 AM

Quote:


I confirmed this with a simple but all-telling star test, where I once compared a TV 101 with a TV102.




Hi Harry, a TV101 (like the SDF) is a different telescope than an NP101.

Like I said, I was where you are once.

Quote:


But it DOES NOT, IMO, translate to better sharpness and contrast





Actually depending on the amount of visual accommodation you have (younger people tend to have more, older people less), a flatter field does mean that the field (overall) is sharper - because everything comes to focus at the same point (a similar argument can be made for color correction, but I don't think it's as big an issue here). OTOH, Increased color correction allows one to see deeper as the energy is where it's supposed to be rather than scattered beyond the airy disk. (I've confirmed that experimentally BTW.) And it results in a cleaner view at higher magnifications.

Quote:


I'm afraid we'll have to agree to disagree!





Sure. No problems there. I respect your opinion. I just don't share it any longer.

Clear skies.

Tom T.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: dtsmith]
      #2169630 - 02/05/08 11:08 AM

Quote:

Does the size of the Focusmate create problems when using the case?




Not in the slightest.

Thanks for all the comments folks!

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
amirab
super member


Reged: 03/03/04

Loc: Israel
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2169643 - 02/05/08 11:16 AM

Hi Tom .

As always ,I like to read you'r reviews and in fact it affected few of my buying decisions.

I own a Genesis SDF.

When you wrote " a TV101 (like the SDF) is a different telescope than an NP101" to what qualities do you refer exactly except CA ? .

Amir


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: amirab]
      #2169660 - 02/05/08 11:21 AM

Hi Amir,

I believe the design is the same but the coatings and glasses are different.

If you aren't an imager you won't gain much at low power.

However, with the samples I owned, I found the performance of the SDF at high power was on a par with (perhaps slightly below) the TV102. The NP101 is clearly a better high power performer.

The SDF is a wonderful telescope - a true classic. I had one, and hated to part with it.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
Brian Gibson
super member


Reged: 10/17/07

Loc: Oakville, Ontario
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2169788 - 02/05/08 12:25 PM Attachment (130 downloads)

Nice article Tom. I have a TV Pronto and a TV-85 as well as one of the original 13mm T1 Nagler's. I will never part with any of them. The quality and performance are truly outstanding and make me smile every time I use them!

Here is a single 60 second Olympus E510 DSLR shot of comet Holmes taken last November with the 70mm Pronto using a TV 0.8X reducer flatener.

Brian Gibson


Post Extras: Print Post   Remind Me!   Notify Moderator  
Clive Gibbons
Mostly Harmless
*****

Reged: 05/26/05

Loc: Oort Cloud
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2169803 - 02/05/08 12:31 PM

Another excellent review from you, Tom.
We can always count on you for the "straight goods".

Your behind-the-scenes look at TeleVue was also really neat.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Clive Gibbons]
      #2169817 - 02/05/08 12:36 PM

Nice shot Brian!

Clive, that was (at one time) supposed to be a full fledged article. I visited last year at NEAF and was planning on doing something a month or two down the road. Unfortunately, my mother passed during that time frame, and I wasn't able to write for a while. By the time I found my voice again, my impressions weren't as immediate and the article wouldn't have been anywhere near as good. I'm glad that I was finally able to get something of it down.

I appreciate your comments gents.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rick rian
Seeker of Truth(s)
*****

Reged: 08/03/04

Loc: Upper Mid West
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2169883 - 02/05/08 01:13 PM

Thanks Tom, another wonderful review.

Post Extras: Print Post   Remind Me!   Notify Moderator  
timmbottoni
Carpal Tunnel


Reged: 08/25/05

Loc: W Chicago suburbs, IL USA
Re: CN Report: The Tele Vue NP101 new [Re: rick rian]
      #2170089 - 02/05/08 02:54 PM

I really enjoyed the review Tom!

I appreciate your up front, and descriptive approach, and if you ever need another set of eyes on some piece of equipment you are reviewing, you can feel free to contact me!

Timm


Post Extras: Print Post   Remind Me!   Notify Moderator  
goober
member


Reged: 12/31/07

Loc: Victoria, Australia
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2170432 - 02/05/08 05:10 PM

Quote:

If I had to pick just three, it would be the 31 Nagler t5, the 13mm Ethos, and the 2-4 zoom. I'd also pick the Antares 1.6x or TV 2x barlows.




Cheers Tom.

Someone was kind enough to drop an Ethos in my scope last week, and I still haven't recovered from the view through it. It sort of made my 24mm Panoptic and 11T6 Nagler instantly redundant

Also, a visiting 7mm Pentax XW performed nicely against my 7mm Nagler T6 - seemed to provide brighter, more comfortable views. Need to do some more comparisons with this match up.


Post Extras: Print Post   Remind Me!   Notify Moderator  
spaceydee
Postmaster
*****

Reged: 04/16/04

Loc: Where the Kittens Are
Re: CN Report: The Tele Vue NP101 *DELETED* new [Re: goober]
      #2170946 - 02/05/08 08:34 PM

Post deleted by spaceydee

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jim Romanski
Carpal Tunnel
*****

Reged: 01/02/05

Loc: Guilford, Connecticut
Re: CN Report: The Tele Vue NP101 new [Re: spaceydee]
      #2171069 - 02/05/08 09:26 PM

Excellect review Tom.

But shouldn't you be working on the next installment of your Nagler review?


Post Extras: Print Post   Remind Me!   Notify Moderator  
spaceydee
Postmaster
*****

Reged: 04/16/04

Loc: Where the Kittens Are
Re: CN Report: The Tele Vue NP101 new [Re: Jim Romanski]
      #2171081 - 02/05/08 09:32 PM

technically speaking, this is a Nagler!
(doesn't NP stand for Nagler/Petzval??)


Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2171284 - 02/05/08 10:59 PM

Tom, nicely written review. I wish it were in you to review other APOs that are more cost effective. I thought that was the point to relay of the review I was to read.

The longer APOs on the market than f/5.4 will offer sharp to edge color free performance as well with less elements to degrade the final wavefront as found in Nagler's specialized 4-element design. Include to this the absolutely desireable depth of focus from them that more accurately compensates for atmospheric changes to focus at high powers. An f/5.4 quickly falls flat on it's face in this regard.

[snip, spaceydee]

Would I buy another product of theirs at today's prices?? I have stars in my eyes but they are from the sky above and not my dreamy imagination.

It is my opinion that there is far better money spent and review time to be done elsewhere. I hope to see more work done with scopes and eyepieces other than TeleVue all the time.

Don't get me wrong, I always wish to speak the truth, and I do like your literary style, however. It is the best there is and improving all the time!

Edited by spaceydee (02/11/08 12:29 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
docmusolf
Out of Africa


Reged: 09/06/07

Loc: port austin, mi
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2171381 - 02/05/08 11:52 PM

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.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2171413 - 02/06/08 12:08 AM

Hi Pete,

Good to hear from you.

[snip, spaceydee]
As per other reviews - well, they come in waves. FWIW, in the years I've been doing this, do you realize this is actually the first stand alone review I've done of a TV scope! I have talked about two or three others over the years, but Iirc those were short comparision articles. Kinda funny, huh. I do have several other projects in the works. Perhaps you'll find some thing more to your liking down the road.

BTW - When are you going to do some bino reviews/picks? You always had a talent for finding some real deals! I miss seeing those.

T

Edited by spaceydee (02/10/08 01:24 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2171514 - 02/06/08 01:29 AM

Hi Tom,
Well it is good to hear all the news.

[snip, spaceydee]

Thanks for suggestion on bino reviews. Glad you liked them. Right now, of all things, I prefer simple binoviewing with a small refractor. At least the stars are nice and sharp!

Edited by spaceydee (02/11/08 12:30 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
naglertized
Carpal Tunnel
*****

Reged: 01/10/07

Loc: Jacksonville Florida
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2171715 - 02/06/08 06:57 AM

Has this turned into a bash TV thread?

In my industry (opthalmic) I have seen perfectly assembled products turned into trash from abuse. I don't care how well manufactured a product is, it can still be trashed due to abuse.

Regarding the Genesis, I'm holding a October 1989 issue of Astronomy Magazine, it was advertised as a 4 element APO.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: naglertized]
      #2171767 - 02/06/08 08:04 AM

[post deleted by spaceydee]

Edited by spaceydee (02/10/08 01:28 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2171786 - 02/06/08 08:32 AM

[snip - quote deleted by spaceydee]

From a slightly different point of view, a companies product of 25 years ago is quite relevent, if taken in the appropriate context. Certainly the APO refractor has come a long way since 1989 and one does not expect A-Ps nor TV's of that era to match the performance of the scopes 20 years later. After all, the scopes of today wouldn't exist without these forefathers.

But those older scopes are very telling, even with the major improvements that TV and other companies have made since 1989, these older scopes are still good performers and provide very good views. They are an indication of a company that was dedicated to making a solid, durable product that was near state of the art for it's time and that one can expect that same dedication today with today's product.

20 years down the road, the NP-101 maybe have been superceded by several models with various improvements and we will be looking back at the less than perfect "this and that" of the NP-101. Hopefully though, we won't miss the big picture, ie that the 20 year old NP-101 will still be a very effective telescope capable of providing the observer many productive nights of pleasure and learning and with just a bit of care, it will be like new.

Jon

Edited by spaceydee (02/10/08 01:29 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Jon Isaacs]
      #2171825 - 02/06/08 09:05 AM

Good points Jon.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
davidmcharg
super member
*****

Reged: 05/29/05

Loc: Scotland, UK
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2171907 - 02/06/08 10:13 AM

Great review tom and could not agree more. I don't have NP101 but i have a little TV85 and its a scope that is going to be with me for many many years to come. A nice pair of binoculars, a small 4" APO and 8"+ reflector is a life time of observing giving you the best of all worlds.

Post Extras: Print Post   Remind Me!   Notify Moderator  
sixela
Postmaster
*****

Reged: 12/23/04

Loc: Boechout, Belgium
Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2172011 - 02/06/08 11:08 AM

Quote:


I confirmed this with a simple but all-telling star test,




Star testing APOs is anything but simple. If you believe it is, then you're in disagreement with both the late Thomas Back and Roland Christen.

A lot of high order aberrations that have little impact on the in-focus image can often be seen outside of focus, and to the untrained eye look like low order spherical aberration. So much so that even Markus Ludes often tries to hack something together in Aberrator that looks *exactly* like a picture of a star test before he ventures to throw numbers around.


Post Extras: Print Post   Remind Me!   Notify Moderator  
gmacln
professor emeritus


Reged: 04/10/06

Loc: Ontario, Canada
Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2172036 - 02/06/08 11:22 AM

A great read as usual Tom. Thanks!

Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: naglertized]
      #2172225 - 02/06/08 12:56 PM

Quote:

Has this turned into a bash TV thread?

In my industry (opthalmic) I have seen perfectly assembled products turned into trash from abuse. I don't care how well manufactured a product is, it can still be trashed due to abuse.

Regarding the Genesis, I'm holding a October 1989 issue of Astronomy Magazine, it was advertised as a 4 element APO.




Clinton,
As would be expected, most of the owners of high dollar APOs would cherish them and therefore be careful to keep them sound. I know I did. Never banged mine on a door or threw it out the window on a cloudy day

When Tom discussed the aspect of paint chipping in his report as per his experience with the scope under test, I offered to share some of my own experiences as well. Experiences are not always going to be positive ones but to honestly discuss them in a thread is always going to be so. This includes experiences with the related pieces of the equipment when are used together. An overall experience by a product user offers others greater knowledge and that is what we are here for. The thread is to discuss the TeleVue 4 element refractor design and execution. Can be current or historically. If product discussions are restricted to only be one sided as "sweet smelling roses", all the time, our behavior would serve as a disservice to those that come here to learn.

Let's not forget that fact about a company keeping a product as cost effective as possible. A question might be why for example would a rack and pinion focuser be used when a Crayford is better and now the industry standard? Why would lenses be figured to just meet the Rayleigh criterion instead of being openly documented at something of greater accuracy? The reason is whatever the market accepts (and why) is all that matters. There are more questions, far more than answers, but if bias is set aside, I think you may can see my point.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2172334 - 02/06/08 01:46 PM

Hi Pete,

I don't think I'd say a crayford is automatically better. IME, it depends on the application that you're going to use the scope for.

Further I'm not certain a poor experience 20-25 years ago with what (at the time) was a new process for them (powder coating) qualifies as a definitive statement on QC (or even in this case a truly valid counterpoint). However, I do agree there are exceptions to everything, and that people should seek out as many informed opinions as possible before considering a major purchase. Excellent advice, and something I always advocate.

And actually, the thread is indeed intended to discuss the NP101 and the NP101 article [snip, spaceydee]
Thanks!

T

Edited by spaceydee (02/10/08 01:33 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
naglertized
Carpal Tunnel
*****

Reged: 01/10/07

Loc: Jacksonville Florida
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2172371 - 02/06/08 01:57 PM

Tom, it was a TV ad. Would it be a violation of TOS to take an image of the ad and post it?

Post Extras: Print Post   Remind Me!   Notify Moderator  
spaceydee
Postmaster
*****

Reged: 04/16/04

Loc: Where the Kittens Are
Re: CN Report: The Tele Vue NP101 new [Re: naglertized]
      #2172442 - 02/06/08 02:24 PM

I would drop it. To be honest there have been a lot of scopes advertised as APOs that today would not be considered such.

Folks, as Tom has suggested can we please get back on topic??

thanks!!


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: spaceydee]
      #2172488 - 02/06/08 02:48 PM

Hi Clinton,

Unfortunately yes.

But I've verified it myself. Times change.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jeff Morgan
Postmaster
*****

Reged: 09/28/03

Loc: Prescott, AZ
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2172568 - 02/06/08 03:32 PM

Quote:

Include to this the absolutely desireable depth of focus from them that more accurately compensates for atmospheric changes to focus at high powers. An f/5.4 quickly falls flat on it's face in this regard.




That would be a myth.


Post Extras: Print Post   Remind Me!   Notify Moderator  
sixela
Postmaster
*****

Reged: 12/23/04

Loc: Boechout, Belgium
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2172620 - 02/06/08 03:51 PM

Quote:


Let's not forget that fact about a company keeping a product as cost effective as possible. A question might be why for example would a rack and pinion focuser be used when a Crayford is better and now the industry standard?




There's nothing wrong with a good rack and pinion focuser. Some of the models with helical teeth are better than any Crayford focuser I've ever met, and they carry very high loads without ever budging a micron.

Astrophysics also has a fine rack and pinion focuser. If you want to convince Roland Christen he hasn't seen the "industry standard" light yet, be my guest.

Have you actually used the Televue rack and pinion focuser? Is it anything like a Synta or GSO rack and pinion focuser?


Post Extras: Print Post   Remind Me!   Notify Moderator  
spaceydee
Postmaster
*****

Reged: 04/16/04

Loc: Where the Kittens Are
Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2172665 - 02/06/08 04:07 PM

I've used the TV rack and pinion and like it a lot better than any other focuser I have used except the Feathertouch. I have never used the Moonlight though.

Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2172672 - 02/06/08 04:09 PM

Not talking about low end Crayfords you mentioned only high end ones where the load capacities and fine performance are generally found superior to R&Ps. Crayfords are superior. There is no possible mechanical slop, there are multi-speed options and this is type especially well suited to short focal ratio telescopes due to the shorter depth of focus. Yes, I've use TeleVue scope many times.

Post Extras: Print Post   Remind Me!   Notify Moderator  
RogerRZ
Whatta you lookin' at?
*****

Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2172675 - 02/06/08 04:10 PM

Quote:

Have you actually used the Televue rack and pinion focuser? Is it anything like a Synta or GSO rack and pinion focuser?




I have, and the answer is NO! The TV models I used (one on a TV102, and another, the newer black-drawtubed model, TV76), were head and shoulders above (actually, probably the waist up, maybe more) the C80ED I now have. Even if the lens is nice on the 'ED, I miss my TV76, and wish I had the green to go NP101...


Post Extras: Print Post   Remind Me!   Notify Moderator  
blandp11
Carpal Tunnel
*****

Reged: 04/19/05

Loc: Glen Ridge, NJ USA
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2172738 - 02/06/08 04:48 PM

The best Crayfords are inferior to the best R&P because a R&P can hold a heavy load under dew conditions with positive mechanical contact while a crayford will slip on the dew slicked surface.

There is a reason why the focusers of Astro-Physics, TEC, TMB, Tele Vue and others are R&P. When an imaging train is hanging pulling off while imaging at the zenith, you want a R&P system.

Philip

Quote:

Not talking about low end Crayfords you mentioned only high end ones where the load capacities and fine performance are generally found superior to R&Ps. Crayfords are superior. There is no possible mechanical slop, there are multi-speed options and this is type especially well suited to short focal ratio telescopes due to the shorter depth of focus. Yes, I've use TeleVue scope many times.




Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2172744 - 02/06/08 04:50 PM

[snip, spaceydee]

Lastly, please see my reply to sixela about Crayfords vs. R&Ps. In high end they are more complex and more costly to manufacture. They have greater performance parameters for all scopes and applications. Just because TeleVue or Astro-Physics simply don't use them doesn't really justify their approaches. That's why I mentioned factor of cost just as you have at the beginning of your article. yes R&Ps can be excellent but equasl quality Crayfords are better especially with faster scopes. They provide a more precise focus for critical applications.

Edited by spaceydee (02/10/08 01:35 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: blandp11]
      #2172763 - 02/06/08 04:59 PM

And what you are saying is that the dew issue is one that cannot be rectified?

Like I said, just because others use rack and pinion instead of Crayford design really tells us nothing definite about advantages. The points made regarding the Crayford are valid more diversified pointing toward a better product.


Post Extras: Print Post   Remind Me!   Notify Moderator  
spaceydee
Postmaster
*****

Reged: 04/16/04

Loc: Where the Kittens Are
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2172767 - 02/06/08 05:02 PM



Folks lets keep all "personal remarks" to ourselves from this point forward.

Thanks

your moderator


Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: Jeff Morgan]
      #2172795 - 02/06/08 05:17 PM

Jeff,
I stand corrected. Very interesting since my life long experiece with long f/ratio to short seemed to indicate otherwise viewing the planets. I've learned something new and exiting today.
Thank you.


Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2172803 - 02/06/08 05:21 PM

Quote:

Include to this the absolutely desireable depth of focus from them that more accurately compensates for atmospheric changes to focus at high powers. An f/5.4 quickly falls flat on it's face in this regard.




This that I stated above is incorrect. Jeff Morgan points to a helpful article done by our friend Bryan Greer that shows this long held understanding to be invalid.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2172854 - 02/06/08 05:45 PM

Quote:

Let's not forget that fact about a company keeping a product as cost effective as possible. A question might be why for example would a rack and pinion focuser be used when a Crayford is better and now the industry standard?




Actually I believe it's the mid range scopes that use Crayfords, the high end use premium rack and pinions like theR&P Feathertouch, I believe that's what A-P uses among others. I think the reason to use a Rack and Pinion is that R&P focusers are better at handling heavy loads. They are however more expensive to manufacture.

Dollar for Dollar you get more with a Crayford but friction has it's limits as a drive mechanism and so at the point where a designer quits playing the best value game and goes for the best design regardless of cost, a rack and pinion again becomes the design choice.

Jon

Edited by Jon Isaacs (02/06/08 05:54 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: Jon Isaacs]
      #2172878 - 02/06/08 06:03 PM

Hi Jon,
As someone in the engineering field I believe you to know quite a bit. How confident are you of the R&P costing more to produce? And especially when are weight loads so high the Crayford of excellent quality insufficient? It is my understanding from specifications and use that they handle up to 8-10 pounds. A TeleVue having to hold that much would impress me.
Thanks.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Doug D.
Carpal Tunnel
*****

Reged: 08/23/05

Loc: Virginia
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2172887 - 02/06/08 06:07 PM

An AP 2.7 or 4" focuser R&P is designed to be subjected to flattener, TC and a big honking SBIG that could easily exceed the 8-10 lbs you refer to. Some of these CCD cameras and filter wheels add a lot of weight (let alone additional optics in train), so even a TV could be subjected to loads in excess of 10 lbs by high-end imagers. My understanding is that the IS version focusers were designed with that in mind as well.

Curiously - Roland recently posted something germane here


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Jon Isaacs]
      #2172892 - 02/06/08 06:10 PM

[post deleted by spaceydee]

Edited by spaceydee (02/10/08 01:40 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2172945 - 02/06/08 06:39 PM

Quote:

Hi Jon,
As someone in the engineering field I believe you to know quite a bit. How confident are you of the R&P costing more to produce? And especially when are weight loads so high the Crayford of excellent quality insufficient? It is my understanding from specifications and use that they handle up to 8-10 pounds. A TeleVue having to hold that much would impress me.
Thanks.




My thinking goes like this: Precision gearing is expensive to manufacture because of the difficulty in accurately machining a complex tooth profile. We all know what a good RA drive costs. Crayfords eliminate the problem of quality gearing by using a friction drive. It's a compromise because you are now putting side loadings on the shaft unless you use a backing bearing (ED-80)in order to provide the traction. With a light load this can make for a nice smooth, easy focuser but as the loads on the focuser increase, the side loadings which provide that traction must increase, not so good. I like Crayfords on a dollar for dollar basis but they are more finicky than a good rack and pinion.

So at some point, a designer probably says, enough is enough, lets quit trying to force the issue and just provide a positive gear drive. In the case of the gear drive, side loading on the draw tube may be what keeps it in place once it is focused but it is not required for focusing.

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
naglertized
Carpal Tunnel
*****

Reged: 01/10/07

Loc: Jacksonville Florida
Re: CN Report: The Tele Vue NP101 new [Re: Jon Isaacs]
      #2173379 - 02/06/08 09:44 PM

Ford ( GT ) and Ferrari ( Enzo ) use R&P steering on their 200MPH+ cars, must do pretty well under pressure.

All I have to say is I may go the route of an NP127 instead of waiting for my name to be called on the AP wait list. I'm 8 months in on the 160 list. Speaking strictly visual only one can't go any better that the NP series, the obligatory IMHO.

Again, thanks for a great telescope article Tom.


Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2173544 - 02/06/08 11:00 PM

[post deleted by spaceydee]

Edited by spaceydee (02/11/08 12:46 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: Jon Isaacs]
      #2173613 - 02/06/08 11:44 PM

Hi Jon,
Thanks for elaborating so fluidly on this from an engineering standpoint, is most appreciated.

Let me, if I may, add some more thoughts to this. One is that all focuser designs have inherent compromises built into them. Even a precision rack and pinion assembly has its weaknesses. Both the types under discussion of course also have their strengths and there is new work being done regularly to improve both.

Another aspect to ponder is that the R&P has only two moving parts, the rack and the pinion gear. With that are the outer housing with machined clearance channel and drawtube (often with a shallow machined trough).

The, Crayford, OTOH, has more and complex parts to offset the high pressures involved from the roller against the land placed on the drawtube. To do this well, small roller bearings are set at the opposite side to the force placed on the drawtube. The outer casting now becomes more elaborate with needed stations for the small roller bearings. The land itself, where the focuser roller shaft comes in contact, is best made wear resistant as bearing surface itself (hence the more advanced Feathertouch model with hardened steel plate). These things require quite a bit of machining/processing to be done right, and there is significantly more again needed when one considers a 2-speed model with a planetary gear assembly.

I'm not sure that a R&P with a high precision gearing assembly is all that costly against an equivalent (or approximately) heavy duty Crayford. Not talking the 4" model type, here. The actual R&P gears in this size for any of them are not really that expensive to obtain. Probably well under $100 in many cases, AFAIK.

The first highly successful JMI Crayford was quite expensive to produce due to the design time, set up to manufacture, and other related expenses. Do you suppose there is a real difference here today in cost comparisons and overall performance when talking about the best of both types of these focuser mechanisms? Is probably too hard to quantify but the above should give something of a general feel.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Hermie
sage
*****

Reged: 04/20/05

Loc: Cloudy HKG
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2173686 - 02/07/08 12:30 AM

Tom,

Thank you for the great and honest report. All of us appreciate your reviews, even if we don't all agree with you.

I'm a visual observer looking for a hassle free easy to use telescope, and so found myself looking at 4-5" APOs. I was looking at the TV101 for portability, but the new TV102 binoview package caught my eye - apparently it is the same size as a 101. Any thoughts?

Thanks again!


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2173764 - 02/07/08 01:54 AM

Quote:

Do you suppose there is a real difference here today in cost comparisons and overall performance when talking about the best of both types of these focuser mechanisms? Is probably too hard to quantify but the above should give something of a general feel.




I do believe that a quality rack and pinion is more expensive to manufacture but really that is not the point here, that is really off topic.

The point here is that the 101NP uses a Rack and Pinion and you commented that Crayfords were better and this was in indication of TeleVues lack of commitment to quality.

Quote:

Let's not forget that fact about a company keeping a product as cost effective as possible. A question might be why for example would a rack and pinion focuser be used when a Crayford is better and now the industry standard?




In the context of the current conversation, that statement clearly does not stand up, at the high end, Crayfords are not the industry Standard nor are they clearly better.

So, I think it is time to get back on topic and discuss the NP-101 and not the difficulty of producing a high quality rack and pinion focuser. It is clear people are doing that and it clear that TeleVue is doing it.

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
AL A.
super member


Reged: 12/11/05

Re: CN Report: The Tele Vue NP101 new [Re: Jon Isaacs]
      #2173927 - 02/07/08 05:58 AM

Tom, thank you for the excellent review. I have the NP101's big brother, the NP127, and I am extremely happy with it. Considering its optical performance, excellent build quality, and relatively light weight, I wouldn't trade it for any other 5-inch refractor.

Al


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Hermie]
      #2174080 - 02/07/08 08:38 AM

Quote:

Tom,

Thank you for the great and honest report. All of us appreciate your reviews, even if we don't all agree with you.

I'm a visual observer looking for a hassle free easy to use telescope, and so found myself looking at 4-5" APOs. I was looking at the TV101 for portability, but the new TV102 binoview package caught my eye - apparently it is the same size as a 101. Any thoughts?

Thanks again!




Hi Hermie,

Thank you.

The TV102 is a wonderful telescope, and the new package makes it even better. If you want to binoview, it's a superb choice. Off the top of my head, the only things you'll be "giving up" over the NP101 are the extreme wide and flat field, and you'll sacrifice a bit of performance due to the residual CA.

The 102 will be probably a bit lighter (although having to carry an extension tube probably makes up for not having the rear lens elements).

If I can make a suggestion - you might give TV a call, ask for Al and see what he recommends.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2174105 - 02/07/08 08:57 AM

[post deleted by spacyedee]

Edited by spaceydee (02/10/08 01:45 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2174111 - 02/07/08 08:59 AM

Thanks for your comments guys.

Post Extras: Print Post   Remind Me!   Notify Moderator  
RogerRZ
Whatta you lookin' at?
*****

Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2174170 - 02/07/08 09:34 AM

No matter what anyone says, I still really enjoyed the use of my TV102 and TV76, and would like to someday, get my hands on a NP101...

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jeff Morgan
Postmaster
*****

Reged: 09/28/03

Loc: Prescott, AZ
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2174353 - 02/07/08 11:21 AM

Quote:

Very interesting since my life long experiece with long f/ratio to short seemed to indicate otherwise viewing the planets.




All things considered, I still prefer longer ratios myself.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Jeff Morgan]
      #2174494 - 02/07/08 12:42 PM

That was one of the main reasons I held off on trying the NP101 myself for such a long time.

Post Extras: Print Post   Remind Me!   Notify Moderator  
peleuba
scholastic sledgehammer


Reged: 12/01/04

Loc: Southern PA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2174734 - 02/07/08 02:37 PM Attachment (114 downloads)

Quote:


But after using the NP for a year I have to admit that Paul was absolutely correct in this and I was wrong. The NP is a different beast than the TV101 or the Genesis SDF, and it really is a step up from the TV102.

Tom T.





Hey Tom -

Really a superb job - as always. I could not agree with you more (tee-hee ).

I have really liked the NP101's that I have owned. The NP101 while premium priced, really does represent a near perfect package. When you combine build quality/ruggedness, optics and portabalility I cannot think of another telescope that comes close. Sure, there are others that excel in one area or another, but as a complete package, its alwfully tough to beat the NP101.

Thanks for mentioning our previous conversations on the TeleVue Yahoo group. Those debates were a lot of fun.

Looking forward to finally meeting you in person later this Summer.

Best Regards.


Post Extras: Print Post   Remind Me!   Notify Moderator  
peleuba
scholastic sledgehammer


Reged: 12/01/04

Loc: Southern PA
Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2174836 - 02/07/08 03:19 PM

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.

Edited by peleuba (02/07/08 03:49 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Dirtyharry
member


Reged: 11/01/07

Re: CN Report: The Tele Vue NP101 new [Re: peleuba]
      #2175043 - 02/07/08 04:35 PM

Hello Paul,

I'm not an expert on star testing and I agree that star testing is a complex subject, as Suiter's great book exemplifies. That said, I did use a green filter (over a few nights) to reduce the wavelength range and this showed the diffraction rings better both inside and outside focus. It worked much better on the TV 101 than on the TV 102 as I recall. But in essence, the star test is easy to judge. In a word, what you're looking for is perfect symmetry at equidistant points inside and outside focus. An even better test, IMO, is through observing planets under calm seeing conditions. In this respect we both agreed that the view of Jupiter with my buddy's 101 had a slightly softer appearance than that seen through the 102. You see, you don't have to be an optical genius to spot a real difference in performance!
1/6th wave sounds a bit low for some of the literature I've seen on the 102. Less good sample maybe?

Harry.

Harry


Post Extras: Print Post   Remind Me!   Notify Moderator  
peleuba
scholastic sledgehammer


Reged: 12/01/04

Loc: Southern PA
Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2175159 - 02/07/08 05:35 PM

Quote:


I'm not an expert on star testing and I agree that star testing is a complex subject, as Suiter's great book exemplifies.





Harry,

I have found Dick Suiter's book to be a wonderful reference especially as it pertains to CATS and Newts. But, IMO it is not the end-all, be-all for APOchromatic refractors...

It makes little mention of Spherochromatism; which is the level of spherical aberration present at a given (single) wave length of light. Spherochromatism makes the star test quite difficult to interpret. It usually manifests itself as making one side of the diffraction pattern "less contrasty" then the other side. In an APO, you can have seemingly different Fresnal patterns on either side of focus yet have a lens with a very high Strehl. I have seen this myself. But, don't take my word for it - go search the literature... Start with reading Roland Christen's essays on the subject.


Quote:


1/6th wave sounds a bit low for some of the literature I've seen on the 102. Less good sample maybe?





I dunno - could be. TeleVue does not publish wavefront ratings or Strehls, so I do not know for sure. I do know that the NP101's I have owned were better absolute performers in every sense. Please note this does not take into account cost. I am just looking at performance on the bench and under the night sky.

Edited by peleuba (02/08/08 11:11 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
JoeBftsplk
sage
*****

Reged: 09/26/07

Loc: North of the Fingerlakes-NY
Re: CN Report: The Tele Vue NP101 new [Re: peleuba]
      #2175356 - 02/07/08 07:10 PM

Peleuba,
Your comments on Spherochromatism are interesting. What does it translate to in actual practice while observing?

The reason I ask is that my TV102 sometimes "drives me nuts". I often find that I'm hunting for a good focus on bright stellar objects.

I thought it was astigmatism and asked Televue to check the scope out. They said there was no problem with the scope.

My FS78 doesn't bug me like this, so I don't think it's an issue with my vision. I'm not an expert on star testing and don't wish to become one; but am wondering if this defect you've mentioned could be the source.
Bob


Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: Jon Isaacs]
      #2175931 - 02/07/08 11:08 PM

Quote:



I do believe that a quality rack and pinion is more expensive to manufacture but really that is not the point here, that is really off topic.




Who is to know without looking up some useful price information to make for helpful comparisons? At this point each of us would be operating in essence from opinion. I did try to find something quickly helpful regarding costs of precision racks and pinion gears, last night, but all the producers found stated quotes on request. I can tell you this, I have previously set out to buy precision rack and pinions in industry before and they were not that expensive. As I stated, that being the only moving part to the focuser design itself tells me it is a more cost effective design focuser to use. One that has a leverage advantage as other folks pointed out earlier, but there doesn't seem to be anything more than that that I'm aware of. When I spoke of the NP101's using a R&P as a cost effective measure, who is to say this isn't also true in real life?

Quote:

The point here is that the 101NP uses a Rack and Pinion and you commented that Crayfords were better and this was in indication of TeleVues lack of commitment to quality.




No sir, I never did that. You would unfortunately be reading into this something fully incorrect. I spoke ONLY of cost effectiveness NOT a lack of commitment to quality regarding focuser types. A matter that is indeed on topic, as well, since we are discussing the scope in question. Tom Trusock, the writer of the article clearly pointed out that cost was a part of the equation.

Quote:

Let's not forget that fact about a company keeping a product as cost effective as possible. A question might be why for example would a rack and pinion focuser be used when a Crayford is better and now the industry standard?




I wrote the above through the best of my understandings and my question seems to have been answered in that heavier loads, than I was aware of, are required with todays more advanced levels of astrophotography equipment. I, like others, am willing to accept that "belief" as it does appear to be something very reasonable to understand.

However, this cannot also say the R&P is a better design in itself, overall. I had already brought up commonly accepted points to the contrary by correctly pointing out important distinctions the Crayford design possesses. Why is this relevent to the discussion of the topic telescope? It would be because they make for superior focusing action in other useful areas (no backlash, no play, and a finer focusing action). These are worth pointing out! Just as much so as it is for the distinct advantage a R&P might hold. Users (or potential ones) have varied interests in astronomy. They certainly are not all (or to be) advanced astrophotographers!


Post Extras: Print Post   Remind Me!   Notify Moderator  
starpal
professor emeritus
*****

Reged: 08/06/04

Loc: Mid-USA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2176060 - 02/08/08 12:08 AM

[post deleted by spaceydee]

Edited by spaceydee (02/11/08 12:32 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: CN Report: The Tele Vue NP101 new [Re: starpal]
      #2176347 - 02/08/08 06:56 AM

Quote:

However, this cannot also say the R&P is a better design in itself, overall. I had already brought up commonly accepted points to the contrary by correctly pointing out important distinctions the Crayford design possesses.




Remaining ON TOPIC means discussing the NP101 focuser rather than the generic issues of as to whether the Crayford is better than a Rack and Pinion focuser. Clearly that is a personal choice and best discussed in the appropriate forum. There are many ways to skin a cat and the question here is whether or not the NP-101 has an effective focuser.

I think this is the appropriate starting point:


Quote:

All TV scopes use a proven rack and pinion focuser, unique to TeleVue products. Frankly, I think it's one of the best focusers on the market. For telescopes that have a greater depth of field it works wonderfully. On the faster scopes however (like the NP series) a two speed focuser is definitely appreciated. Enter the Focusmate. The Focusmate is an add on fine focuser for, well, nearly any of the telescopes sold by TeleVue in recent history. (This is just one of the things there is to like about TV. When they design their equipment they do it with several goals in mind, including - but not limited to - backwards compatibility, as well as with an eye to future products.)

The Focusmate sports a 6:1 planetary reduction gearing and is easily installed by the end user. While perhaps not as aesthetically pleasing as the a StarLight Instruments FeatherTouch, it was designed to fit with other accessories within Tele Vue’s Imaging System line. The Focusmate works and it works well. It mates up to an optional motor drive which can be controlled by hand or computer. One of the definite pluses to the Tele Vue system is that the motor is quickly and easily disengaged (without tools) if one wishes to focus manually - you simply loosen a thumbscrew and rotate the motor out of the way.




Looks to me like the NP-101 has a high quality focuser that is effective though the gear reduction unit is not as attractive aesthetically as the Feathertouch.

Jon Isaacs


Post Extras: Print Post   Remind Me!   Notify Moderator  
Doug D.
Carpal Tunnel
*****

Reged: 08/23/05

Loc: Virginia
Re: CN Report: The Tele Vue NP101 new [Re: Jon Isaacs]
      #2176377 - 02/08/08 07:39 AM

Gee, I even like helical focusers....! It depends on the scope, the application, and the likely demands a user puts upon it. A blanket statement that Crayfords or R&Ps are superior - end of story - is really a bit silly. I have a Moonlite on my Dob and I love it, but pop a 31 Nag in there and it slips easily. Does it mean the Moonlite is junk or that an R&P is "best"? Of course not. They both work fine within their intended specs, set points, price points, and respective performance ranges.

As for the NP101, I guess I agree with Tom that most might find the Focusmate less than attractive. Personally, I kind of like the look. I have Focusmate and driver on both my 76 and NP101. They are a delight to use for high mag work (and webcam imaging). My only "complaint" is that I think they are a little pricey - particularly the rebranded Orion focusmate driver.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 *DELETED* new [Re: starpal]
      #2176509 - 02/08/08 09:26 AM

Pete Said
Quote:


What about flatness across FOV?





From http://www.cloudynights.com/item.php?item_id=1749

Quote:


Other characteristics of the design include: improved color correction (in a Petzval, color is reduced from that of a comparable focal ratio doublet by some 30%), and flat fields. As implemented by TeleVue, the NP series allows for stunning widefield views with no field curvature.





Remainder of post currently unavailable as part of a good faith effort to clear up a misunderstanding.

Edited by Tom Trusock (02/10/08 04:19 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
jtpowers
more clever in the first place
*****

Reged: 11/03/05

Loc: Cambridge, MA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2176585 - 02/08/08 10:11 AM

Hi Tom,

I've heard or read somewhere that shorter focal length (i.e. Tak's Sky90) refractors are more sensitive to seeing/atmospheric variations. Perhaps it's mainly true for short f. ratio doublets...?

In your experience with the TV102 and NP101, does this hold for the f5.4 NP101 vs. the f8.8 TV102? Or is it offset in the NP101 because the front elements are a longer focal length (F12 or something)? Or, is it offset as a function of lens design, element number (as it contributes to lens design), etc...? I've always wondered about this, especially as the seeing here in Boston is typically atrocious.

Thanks!


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: jtpowers]
      #2176708 - 02/08/08 11:17 AM

Hi John,

Jeff Morgan linked to a nice article by Bryan Greer on just this topic:

http://www.fpi-protostar.com/bgreer/seeing.htm

T

Edited by Tom Trusock (02/08/08 01:06 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
peleuba
scholastic sledgehammer


Reged: 12/01/04

Loc: Southern PA
Re: CN Report: The Tele Vue NP101 new [Re: JoeBftsplk]
      #2176861 - 02/08/08 12:29 PM Attachment (84 downloads)

Quote:


Your comments on Spherochromatism are interesting. What does it translate to in actual practice while observing?





Hi Bob,

Spherocromatism will not cause bright star points to become less star like. The effects of spherocromatic aberration can be seen more easily when looking at bright planets or by performing the star test.

One of the strong points of the TV102 is it's relatively deep depth of focus due to the longish focal ratio. If your hunting for "best focus" in the TV102 while your other scopes seem to snap, I think something is wrong. I think your FS78 is around F/8 so it should have a similar depth of focus.

Astigmatism is pretty easy to detect and, if bad enough, will prevent a star from focusing down to a point of light. Rather then a point, the star will appear in as "cross" pattern.

I have done some modeling and have attached a jpeg illustrating astigmatism. The image on the left is that of a star at high magnification through the TV102 with no aberrations - its an essentially perfect view. The middle image depicts the same star but with 1/4 wave of astigmatism. The right most image is the same star but with a half wave of astigmatism. Notice the cross pattern.

Is this what you see?


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: peleuba]
      #2176876 - 02/08/08 12:39 PM

Hi Bob,

I think Paul already mentioned this, but don't forget about the effects of seeing. If it's happening some nights and not others, I suspect that's probably a real good bet.

And as an added clarification about spherochromatism I'd include the fact that it's inherent in the design and really to be expected of any moderate speed doublet. One way (there are others) to correct for spherochromatism is by using extremely long focal lengths and I'm guessing a Petzval falls in here because of the speed of the front doublet.

FWIW, the effects of spherochromatism are mainly seen out of focus and can fool the user into thinking they have a telescope with some spherical aberration. This is why filters are appropriate for use when testing APO's.

TMB has a good paragraph on spherochromatism here:
http://geogdata.csun.edu/~voltaire/tmb/definition.html

To remain on topic, I'd add that like Paul, I too find the NP101 to have the lowest amount of spherochromatism of any apochromatic refractor I've ever looked through.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: peleuba]
      #2176881 - 02/08/08 12:41 PM

Quote:

Quote:


But after using the NP for a year I have to admit that Paul was absolutely correct in this and I was wrong. The NP is a different beast than the TV101 or the Genesis SDF, and it really is a step up from the TV102.

Tom T.





Hey Tom -

Really a superb job - as always. I could not agree with you more (tee-hee ).

I have really liked the NP101's that I have owned. The NP101 while premium priced, really does represent a near perfect package. When you combine build quality/ruggedness, optics and portabalility I cannot think of another telescope that comes close. Sure, there are others that excel in one area or another, but as a complete package, its alwfully tough to beat the NP101.

Thanks for mentioning our previous conversations on the TeleVue Yahoo group. Those debates were a lot of fun.

Looking forward to finally meeting you in person later this Summer.

Best Regards.




Hi Paul,

Me too!

BTW - did you manage to get your hands on that NP101 we discussed this summer?

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
JoeBftsplk
sage
*****

Reged: 09/26/07

Loc: North of the Fingerlakes-NY
Re: CN Report: The Tele Vue NP101 new [Re: peleuba]
      #2177126 - 02/08/08 03:00 PM

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: JoeBftsplk]
      #2177141 - 02/08/08 03:06 PM

Hi Bob,

I can't speak to your specific sample, but if if makes you feel any better, I owned a TV102 for many many years, and it was a very very good optic.

As per the FT focuser - if you installed it, one other thing you might want to check is the collimation of the scope. If you somehow managed to miscollimate it while installing, that could contribute to the "finicky" feeling on a scope. (In this case it would most likely be a misalignment of the focuser with the lens. Frankly, I doubt this happened, but it is a possibility I guess.)

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
naglertized
Carpal Tunnel
*****

Reged: 01/10/07

Loc: Jacksonville Florida
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2177575 - 02/08/08 06:21 PM

Tom,

Does the NP101 impart any color tonality, such as being "warm" or "cold"? Does color tonality differ between the NP series and the other TV APO's such as the 102?

Thanks


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
naglertized
Carpal Tunnel
*****

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!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Daniel Mounsey
Vendor (Woodland Hills)
*****

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)


Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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!


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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!!


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
sixela
Postmaster
*****

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).


Post Extras: Print Post   Remind Me!   Notify Moderator  
jonnyastro
Carpal Tunnel
****

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?

Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

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.

Post Extras: Print Post   Remind Me!   Notify Moderator  
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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Downward Bound
Adrenaline Junkie
*****

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!!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
sixela
Postmaster
*****

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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
RogerRZ
Whatta you lookin' at?
*****

Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2180632 - 02/10/08 07:40 AM

I had a TV102, and the in-focus images were so nice, that I never once considered ovserving with it out of focus. I suspect the NP101 is the same.

Post Extras: Print Post   Remind Me!   Notify Moderator  
sixela
Postmaster
*****

Reged: 12/23/04

Loc: Boechout, Belgium
Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2181302 - 02/10/08 02:22 PM

Quote:


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





This snippet:
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. The 101 was more like 1/5th wave, which is enough to take the edge off fine planetary detail.




Given that you describe the star testing as "simple" and given your subsequent general comments about star testing, I have doubts as to the rigour which which you came to assess the 101's performance.

Which *is* the subject of the thread, after all.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Dirtyharry
member


Reged: 11/01/07

Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2181637 - 02/10/08 04:39 PM

Hi Sixela,

On the matter of the TV 101, it has already been asserted that the 102 has sharper optics than the Genesis SDF (see the astromart review comparing them both)and that critical assessment by observers I trust (Ed Ting and Phil Harrington) both agreed that the 102 was sharper optically than the 101(despite it having marginally better color correction). As my threads already discussed, I confirmed this visually on Jupiter by comparing both the 102 and 101 images on the same night. Both gave excellent images, but the 101 was slightly softer IMO. No amount of optical theory can alter my own conclusions. Or, in the immortal words of the celebrated English poet John Keats, " Nothing is real until it is experienced"


Harry


Post Extras: Print Post   Remind Me!   Notify Moderator  
skyview
Pooh-Bah


Reged: 02/01/06

Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2181894 - 02/10/08 06:35 PM

Late to the party here but thanks for the article Tom, as always it was very thorough and well done. Being lucky enough to own an NP101 I was almost tempted not to read the article as I pretty much knew what would be said; although, it never hurts to be reminded of what an absolute gem this scope is. I always find it somewhat strange and often amusing that when the ubiquitous "best 4 inch APO" posts come up that the NP101 is mentioned as infrequently as it is. Perhaps the only thing better than an NP101 is an NP127, but thats another debate.

Overall my minimal gripes with the NP101 would be:
1) Length, as you mentioned, due to its optical design its functionally an F5.4 but in a slower body
2) Price (worth it IMO), which may keep it out of deserving hands
3) May requires use of well made, designed, and perhaps expensive EPs depending on your viewing habits. This may be more of a problem with fast scopes in general but I really noticed a difference in EP performance between my TV76 (f6.3) and the NP101, some EPs didnt work as well in the NP101. Perhaps I am overly sensitive to these things.

As an aside, I would like to add that I too have the focusmate with the driver and will echo how well it works. It may not be the most elegant looking device but I think it works with the scopes aesthetics and it is extremely functional. It also can handle heavy loads, it tolerates my use of a denkII with twin pan24s with no obvious problem.

As a further aside did anyone in the central Ontario (east of Toronto) region do anything to make the astro gods especially furious? I havent had decent viewing conditions for months, I'm not kidding. If its not snow, its fog, if its not fog its wind. Come on, admit what you did and repent. Of course, in retrospect it could be all my fault as the viewing has gone down hill since I waitlisted a Mach1. Is there an "eventually new equipment curse" I dont know about that strikes those who dare sign up for things that wont be available for potentially years. Makes me wonder what the skies will be like when the Mach1 makes its way to my backyard, I expect "black hole" and near-earth orbit" to be prominent in the vocabulary of any survivors who dare speak of it.

Back to topic: Well Done Tom.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2181957 - 02/10/08 07:03 PM

Quote:

Hi Sixela,

On the matter of the TV 101, it has already been asserted that the 102 has sharper optics than the Genesis SDF (see the astromart review comparing them both)and that critical assessment by observers I trust (Ed Ting and Phil Harrington) both agreed that the 102 was sharper optically than the 101(despite it having marginally better color correction). As my threads already discussed, I confirmed this visually on Jupiter by comparing both the 102 and 101 images on the same night. Both gave excellent images, but the 101 was slightly softer IMO. No amount of optical theory can alter my own conclusions. Or, in the immortal words of the celebrated English poet John Keats, " Nothing is real until it is experienced"


Harry




Hi Harry,

I'd also (re)state that it's the NP101 we're talking about here - not the 101. I'd basically agree with those statements in the context with the TV102 and the SDF and TV101. In fact, if you go back to the ask-al section on the TV website he has some comments on the relative performance of those scopes too.

Having owned a TV102 for 6 some years, a Genesis SDF for a time concurrently with the 102 (and having a fairly significant baseline of other telescopes come across my desk or viewed through in the field - including the TV101), I can say that the SDF came close to the TV102, while the sample I have of the NP outperforms the 102.

As it's been noted, star testing apos can be somewhat problematic, and for the typical observer I suggest a comparison of the in-focus images. One very important thing to keep in mind: Focus depth is noticeably shallower with the NP tho, so I can see where one might easily come to your results given a single night of comparison if one is not careful of focus and the NP is not equipped with a fine focuser.

As to your statements about Ed Ting and Phil Harrington, I think you might be a bit confused as to the TV101 (previous generation) and the NP101 (current generation about which this article was written).

As per Phil Harrington in the 4th (current edition) of Starware (pg 104), he writes:

Quote:


No doubt about it, Nagler has done it again. The NP101 is an amazing optical accomplishment setting bar by which all other apochromatic refractors are judged.

This level of excellence does not detract from the TV102, which is an exceptional performer in it's own right. But in side by side tests conducted at Riverside Astronomy Expo, I found it is not in the same league as the NP101.





(emphasis mine)

Additionally, Ed Ting compared the TV102 to a TV101 and SDF, not an NP101 as can be seen here:

http://www.scopereviews.com/page1k.html

Where he makes very similar statements to what I do regarding the relative performance of the SDF and the 102.

To the best of my knowledge, Ed has nothing written up on the NP - certainly not on his website, and I can't recall any print articles.

To be fair, there seems to be a LOT of confusion regarding the NP101 and it's predecessor the TV101. The NP replaced the TV101 several years back. It is a different telescope, and should not be judged the same as it's predecessors. The TV101, while also a fine telescope belongs to an older generation and does not represent the pinnacle that the NP does.

Perhaps TV should have named the NP, the Not your fathers TV101 - 101.

Incidentally, I find it interesting Al waited till this scope to put his name on it. From what I understand the MPT, Rennaisance, the Genesis, the Genesis SDF, and the Tele Vue 101 were also Nagler variants on Joseph Petzval's design, but only this one is the Nagler Petzval 101. If you look at the history of the company, Al has chosen to put his name on only truly revolutionary designs - the Nagler Eyepieces and the Nagler zooms. Now he's lent it to the current design of the np101 and np127. I suspect that was not an accident.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2182017 - 02/10/08 07:21 PM

Thanks for the comments folks, they really are appreciated.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
gripweed44
Pooh-Bah
*****

Reged: 02/12/05

Loc: PDX
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2182685 - 02/10/08 11:44 PM

If a focuser focus's
Is it not in focus?

Focus in the EYE of the observer is what matters
RP or CRAY- what does it matter if it works--

for you


Post Extras: Print Post   Remind Me!   Notify Moderator  
jonnyastro
Carpal Tunnel
****

Reged: 02/14/06

Loc: Pittsburgh, PA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2183658 - 02/11/08 01:29 PM

I would add that Dickinson and Dyer in , "The Back Yard Astronomer", also alluded to the NP101s superiority to the TV102 visually, stating, "optics don"t get any better than this".

Post Extras: Print Post   Remind Me!   Notify Moderator  
Dirtyharry
member


Reged: 11/01/07

Re: CN Report: The Tele Vue NP101 new [Re: jonnyastro]
      #2184314 - 02/11/08 06:33 PM

OK guys, I get the message! Much as the NP101 is a nice piece of kit,I won't be parting with my TV102 anytime soon!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom TAdministrator

*****

Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2184318 - 02/11/08 06:36 PM

Heaven forbid! Harry, the 102 is a world class apo in it's own right. Mine was an excellent piece of kit that gave me many many happy hours under the stars.

T


Post Extras: Print Post   Remind Me!   Notify Moderator  
karim
super member


Reged: 11/09/05

Loc: HB, California
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2188652 - 02/13/08 12:27 PM

I agree with Tom, the FSQ is mostly used for astrophotography, whereas the NP101 (or TV102 to that matter) is visual.

IMHO, the NP101 is to TV102 what C9.25 is to C10.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Daniel Mounsey
Vendor (Woodland Hills)
*****

Reged: 06/12/02

Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2195248 - 02/16/08 02:39 AM

Quote:


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.





Hi Alexis,

Tom T. mentioned some interesting points about the in-focus star test and light outside the airy disc which I found to be quite valid. Just thought I'd share some experiences I had during some observations I made. I have always respected your views and continue to, so I'm attempting to share some observations I made while testing a good number of 4" apo refractors and in this case, two, three and even four of the same exact ones on the same night at the same time. I also had some personal discussions with Markus Ludus at NEAF about the star test, in fact I just recently star tested a new FSQ106 Q for Markus before I sent it to him but let me address something first. I actually don't care what the papers say. If I can't observe the differences myself, then I don't bother.

There is actually quite a bit of difference of opinion in this industry regarding star tests these days. Since we know there are so many orders of spherical aberration, there needs to be some clarification. For example, there have been discussions about differences in the star test being visible outside of focus but not in-focus. But I ask by what standards are these images the same from a visual standpoint? What do they define as absolutely excellent? In other words it's a bit vague.

Here are some observations I made. I took two of the same scopes and focused them on the Trapezium in Orion under excellent seeing conditions. Each one was star tested on a brighter star first and then placed on the Trapezium. I want to make it clear to others that the point of using the Trapezium as a target was NOT about splitting the components as it is not a valid test. The key was to observe and study the contrast between the components and observe the strength of the light in and around the airy discs, particularly the E and F component stars. In some of the refractors I tested, a good number of them did not direct a strong amount of light in the airy discs of the fainter E and F components compared to others and the differences were quite startling to my eyes to say the least!

I'm a custom wood case builder. I can purchase three sheets of A-1 birch ply and build three of the same cases but they still will have subtle differences which can be observed. It's just simply impossible to get every one literally, exactly identical and high quality apos are no different and easily proved to be so during my critical tests with the human eye. In every single case with my tests, the star test proved absolutely dead accurate to what was observed with the in-focus image on the Trapezium and particulary the planets. In other words any optic which exibited a slightly higher degree of under-correction, proved to scatter more light outside the airy disc.

It's just simply impossible for opticians to make every optic exactly the same and thus, observers end up discussing various orders of spherical aberration, but at critical levels of observations, they are still aberrations, they still exist and some can be detected visually. My point is that three scopes with three slightly different star tests will all have a different level or degree of contrast. They are not going to be the same while trying to descern very fine planetary details and that defference will most easily be noticed side by side on the same night. My visual tests clearly validated this. BTW, the NP101's I tested were incredibly consistant in optical quality in that regard. I can understand why Tom likes the NP101, it proved to be a good scope during my observations as well.

Clear Skies!


Post Extras: Print Post   Remind Me!   Notify Moderator  
sixela
Postmaster
*****

Reged: 12/23/04

Loc: Boechout, Belgium
Re: CN Report: The Tele Vue NP101 *DELETED* new [Re: Daniel Mounsey]
      #2195282 - 02/16/08 03:26 AM

Post deleted by sixela

Post Extras: Print Post   Remind Me!   Notify Moderator  
sixela
Postmaster
*****

Reged: 12/23/04

Loc: Boechout, Belgium
Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2195285 - 02/16/08 03:34 AM

Quote:

The key was to observe and study the contrast between the components and observe the strength of the light in and around the airy discs, particularly the E and F component stars. In some of the refractors I tested, a good number of them did not direct a strong amount of light in the airy discs of the fainter E and F components compared to others




I have no issue with that - that's eating the pudding, which is its proof. Performance *in* focus is what counts. What isn't simple is correctly interpreting the *out* of focus star images.

Doing an in-focus star test isn't as simple as it sounds either, by the way, at least not if you want to detect 1/8th wave of spherical aberration. Refractors need to cool as well and will typically show spherical aberration before they're perfectly cooled (the aberrations are nowhere near as ugly a on an uncooled Newtonian, but they do exist).

Quote:


My point is that three scopes with three slightly different star tests will all have a different level or degree of contrast.




If you're talking about the in-focus star test, yes. If you're talking about out of focus star test images, though, it's possible for the three scopes to have very different *out* of focus star test images and still perform identically in the *in*-focus star test. Yes, in theory what you're seeing are aberrations, but I doubt you can see them if the effect in focus is to reduce the Strehl ratio by 0.003. *Some* aberrations are much more visible out of focus than in focus, and that's the danger.


Mind you, even out of focus it's *possible* to discriminate between different orders of e.g. spherical aberration by the way ring patterns *evolve* around focus. But it certainly isn't simple.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Daniel Mounsey
Vendor (Woodland Hills)
*****

Reged: 06/12/02

Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2219435 - 02/26/08 12:46 AM

Hi Alexis,

Forgive me taking so long to get back to this forum. My time has been very limited lately. I don't make any claims regarding Strehl ratios or wavefronts based on visual observations. They mean very little to me.

The issue I'm having with the star test is that since sophisticated triplets have hit the market, opticians have placed contradicting emphasis on the in-focus image and my tests clearly proved that the star test works only one way and that is, that both sides look exactly as close to the same as possible. Obviously there are limitations to this. It's just simply impossible for opticians to make every single lens the same in that manner, not to mention the various temperatures they are exposed to causing differences as well.

As you and I both know, refractors by their very nature will exhibit under-correction throughout the cooling process and it's a safer state for the optic to be in. My FS152 produces a slightly different star tests under various temperatures but the problem I'm having regarding this matter is that some opticians are trying to convince observers that two of the same refractors, one producing under correction and one that isn't are going to produce the same image and that just doesn't fly with me and my tests clearly proved it.

Most observers don't notice it and would be quite satisfied and understandably so. Focusing both instruments on a planet will reveal subtle differences that most observers seeing conditions would rarely allow them to see, not to mention that they'd need two of the same scope to see it more easily. Those last remaining hard outlines on lunar and planetary images can not be the same.

When I listen to some of the things I hear about this new star test, it begins to remind me of the magic bullet theory during the JFK assassination. Since opticians can not make all lenses the same, they have to come up with a reason as to why and those reasons have become a bit misleading. I'd be more than happy to discuss this issue with any optician. There's really nothing to debate though, all one has to do is simply look and see for themselves. Some optics are and "A" and there are some that are just a freak of nature that are an "A+" and they are the rare ones that purist would appreciate, provided their conditions allow.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | (show all)


Extra information
0 registered and 3 anonymous users are browsing this forum.

Moderator:  droid 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 16419

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics