26 replies to this topic

[gezak22]

TV101 + 31 mm Nagler + dark skies. Man!

 

Backstory:

I spent the last couple of years pretty much only doing photography. It requires a lot of my attention as I am still learning, and a mobile setup requires me to setup and tear down every single time I am imaging. This was fine, as I would much rather do one thing really well than do a mediocre job at two things, so I decommissioned my 8" dob (my first scope) in ~2008. A couple of years ago my astrograph was a Tak Sky 90. It was a very nice setup for mono and narrowband imaging. But I eventually ran out of targets for 400mm of focal length, so I moved on to a 525/660mm focal length instrument, and I hoped to sell the Tak to help with funds. The sell was complicated, and in the end I decided to just keep the Tak and convert it into a visual setup. What I loved about the visual Tak visual setup was its compactness - even with my 5" apo and imaging gear, there was plenty of space for the Tak in my car. Because my photo rig still required some baby sitting, I found that the Tak was only used for widefield views. Of course, it's a fast small aperture doublet, so the field curvature was very obvious.

 

While the Tak was a lovely astrograph for my needs, I've found that I was now looking for another application - quick, casual, flat widefield views. Out with the Tak and in with something more appropriate - a TV101. Combined with the 31 mm Nagler I was floored ... by the abysmal performance. The eyepiece forum debugged the issue for me and we concluded that the views were compromised by astigmatism in my eye. Off to the eye doc I went, followed by ordering the proper Dioptrx.

 

This all lead to last night, a night where I really wanted to do some imaging, but clouds were approaching and I was tired. So instead, I only packed up my visual gear and drove out to my local dark site. It was nice to be set up in 1 minute, rather than the usual 1 hour when I am doing photography. And the views were just spectacular. I've always had a thing for dark nebulas, but the large ones in the summer Milky Way just never showed up well in my 8" Dob. The fast 4" Apo is the polar opposite. Dark nebulas popped right out. It was a lot of fun to aimlessly scan around the Milky Way. My personal highlights were NGC6445+6440, and the dark nebulas around M11.

 

I promptly removed the 9x50mm finder scope form the scope the next morning. The finder scope was a critical part of my 8" dob, but it is completely redundant now.

 

Thanks for all the help.

[JimP]

I have been an imager primarily for many years and am now wanting to get back to doing visual at least a significant part of the time with my telescopes. My experiences with low power wide fov visual observing has been just like your initial response, abysmal. I too have astigmatism and have ordered a Dioptrix to correct it and a Takahashi FC 100 F/7.4 DC. I am very hopeful that the wide field low power views will improve significantly. During the summer I live near a beach and the skies looking NE to SW can be very dark. Fingers crossed.

Congrats to you.

[havasman]

I should have my 1st refractor, a midrange instrument, by this time next week and dark nebulae are at the very top of the list for objects to be viewed ASAP. Your nice report just whets my appetite for them.

[bgi]

The NP101's flat field combined with the Terminalger is a combination I remember reading about here many times.

The FC of my smaller scopes always leaves me wanting more when I'm enjoying those wide sweeping views.

 

Grats to you.

[allen g]

I love my np 101 and all of the eps I use with it  especially the  20 ethos and 31 nagler.  The tfovs are magnificent - try the veil and let us know what you think. Enjoy 

[Jon Isaacs]

I love my np 101 and all of the eps I use with it  especially the  20 ethos and 31 nagler.  The tfovs are magnificent - try the veil and let us know what you think. Enjoy 

 

 

Me too.. I think though the 31mm Nagler -NP-101 or TV-101, it's a match made in heaven. I like to say, that's the closest to heaven I'll ever get.  

 

Jon

[sparrowhawk]

What filters are you using with the 31mm terminagler?

[Scott in NC]

Nice story, Geza--thanks for sharing it!

[gezak22]

... try the veil and let us know what you think. Enjoy 

I did, and the North America-Pelican complex. Very nice indeed.

 

What filters are you using with the 31mm terminagler?

I am filterless at the moment. Given that I only occasionally use the visual setup, I don't want to sink any more $ into it this year. I already spent $10k on a CCD for my SCT in early January.

[Jon Isaacs]

What filters are you using with the 31mm terminagler?

 

I use an Orion Ultrablock, a Celestron O-lll and a Lumicon H-Beta, all 2 inch.. I sometimes use the 35 mm Pan or the 41 mm Pan to get a brighter view but mostly its the 31 mm.

 

Jon

[allen g]

I use the astronomik uhc and lumicon O111
With the NP 101, 31 nagler and O111 you get 4.5* and can see the entire veil

[mdanese]

silly beginner question but I have the NP 101 and Nagler 31mm.  Do you put the filter on the eyepiece or the diagonal?  Was thinking of getting a UHC filter and testing this out.  (I have a 2" TV diagonal)

Edited by mdanese, 13 July 2016 - 04:30 PM.

[Phil Cowell]

31mm Nagler, NP101 and dark skies gives me an enhanced state of euphoria. Gives me as close to an optimal release of human pleasure chemical flood as possible.

 

Balance, one scientific to go with the mythological. 

 

 

 

I love my np 101 and all of the eps I use with it  especially the  20 ethos and 31 nagler.  The tfovs are magnificent - try the veil and let us know what you think. Enjoy 

 

 

Me too.. I think though the 31mm Nagler -NP-101 or TV-101, it's a match made in heaven. I like to say, that's the closest to heaven I'll ever get.  

 

Jon

 

[coopman]

I would put it on the diagonal.

[bgi]

I would put it on the diagonal.

 

Then when you change eyepieces, you don't have to fiddle with filters.

[Jon Isaacs]

 

I would put it on the diagonal.

 

Then when you change eyepieces, you don't have to fiddle with filters.

 

 

I put it on the eyepiece.  Less fiddling..

 

Jon

[Jim Romanski]

Yes it's a wonderful thing that NP101 or TV101 and Nagler 31 combo.

 

I sold my NP101 and would be sad except that I replaced it with the NP127. 

 

Slightly small FOV but more aperture with the same beautiful flat pinpoint starfield.

[bgi]

 

 

I would put it on the diagonal.

 

Then when you change eyepieces, you don't have to fiddle with filters.

 

 

I put it on the eyepiece.  Less fiddling..

 

Jon

 

 

Guess it depends on usage.  When I use a moon and skyglow filter, I put it on the diagonal and leave it for hours.  For a short look, yea, put it on the eyepiece or in a filter slide or wheel.  

[Jon Isaacs]

 

 

 

I would put it on the diagonal.

 

Then when you change eyepieces, you don't have to fiddle with filters.

 

 

I put it on the eyepiece.  Less fiddling..

 

Jon

 

 

Guess it depends on usage.  When I use a moon and skyglow filter, I put it on the diagonal and leave it for hours.  For a short look, yea, put it on the eyepiece or in a filter slide or wheel.  

 

 

 

I never use moon or Skyglow filters.  I use color filters on the planets, O-III, UHC and H-Beta filters on nebulae and a solar filter on the sun.

 

 

Jon

[Erik Bakker]

Jim, having owned both, how do you compare the NP101 and NP127?

[bgi]

 

 

 

 

I would put it on the diagonal.

 

Then when you change eyepieces, you don't have to fiddle with filters.

 

 

I put it on the eyepiece.  Less fiddling..

 

Jon

 

 

Guess it depends on usage.  When I use a moon and skyglow filter, I put it on the diagonal and leave it for hours.  For a short look, yea, put it on the eyepiece or in a filter slide or wheel.  

 

 

 

I never use moon or Skyglow filters.  I use color filters on the planets, O-III, UHC and H-Beta filters on nebulae and a solar filter on the sun.

 

 

Jon

 

 

The M&SG helps some here in the white zone.  Maybe when I retire...

[Jim Romanski]

Jim, having owned both, how do you compare the NP101 and NP127?

 

It's more of the same.  To me the color correction and pinpoint star images are the same.  But going from a 4" to a 5" scope is a 56% increase in brightness and that is definitely noticeable.  Globular clusters start to resolve and dimmer objects are easier to pull in.  It's kind of amazing that even with my larger scopes that give brighter images the contrast in the NP127 is so good and the view so aesthetically pleasing, especially on star clusters, that I often prefer using it for DSO. 

 

The NP127 really isn't much harder to pick up and handle but it does require a better mount than the NP101.  You can get away with a CG-5 for most visual observing up to about 200X  But if you were to use it for imaging you'll need a beefier mount.  I have a CG-5 and a CGEM DX.  I haven't started imaging yet but might some day.  When I want to do high power observing especially if I have other people who want to look through the scope I go with the CGEM DX and the views are rock solid. When I go more grab and go I use the CG-5.

 

If TeleVue made an NP152 I would start saving my pennies for one and sell my NP127 when I had enough to buy one.  I keep trying to convince Al and David Nagler that they should make one.

[dothead]

Any high-quality APO coupled with an appropiate Field Flattener /Reducer will match a Petzval system's performance for visual use.

 

Jim, no need to dream about a TV NP152. Just get a Takahashi TOA 150 & the 645 RD reducer/flattener, and you'll have a F/5.6 sytem with a perfectly flat field of 65 mm diameter (good for the ES 30mm 100° AFOV 3 inch eyepiece [52.5 mm fieldstop]).

[Jim Romanski]

I suppose that a Tak TOA 150 with the reducer/flattener would be like having an NP152.  But that's over $13,500 with the reducer/flattener.  Of course who knows what an NP152 would cost.

 

I wonder if the color correction and star images with the reducer would be as good as without it.  The NP scopes are designed to perform that way without add on lenses.  Not to mention that a NP152 would be 2mm larger aperture.

[Jon Isaacs]

Any high-quality APO coupled with an appropiate Field Flattener /Reducer will match a Petzval system's performance for visual use.

 

Jim, no need to dream about a TV NP152. Just get a Takahashi TOA 150 & the 645 RD reducer/flattener, and you'll have a F/5.6 sytem with a perfectly flat field of 65 mm diameter (good for the ES 30mm 100° AFOV 3 inch eyepiece [52.5 mm fieldstop]).

 

Have you actually made this combination work?  You are recommending it, that means you must have actual experience.  There are a couple of issues to consider here:

 

-  Back focus. By their very nature, focal reducers inherently require more inward focuser travel.  Photographically, this is not difficult because few photographers a diagonal but visually, the scope must come to focus with the diagonal in place.  When I looked into using a focal reducer visually on a refractor, what I found was that there was not enough inward focuser travel. 

 

-  Spacing:  The spacing of a focal reducer is critical.  A modified Petzval accomplishes this because the rear element is fixed, the focal plane never moves.  With a photographic field flattener/reducer, typically it mounts to the focuser so spacing is achieved adjusting the camera to reducer distance.  One question here is whether the 645 reducer can be setup properly with the 3 inch diagonal.

 

As as I was trying to find out a bit more about the 645 reducer I stumbled across this old Scope City Page:

 

"The Takahashi Super Reducer 645 reduces the focal length on a TOA-150 from 1100mm to 840mm while speeding up the optics from f/7.33 to f/5.6. However, it also introduces a considerable amount of field curvature on the TOA-150. Stars around the edges of images are noticeably stretched towards the center of the frame. Stars in the center will be nice and round."

 

Somehow that is not sounding quite like the NP-101 or the NP-127.  

 

- The claim that any high quality apo can match a Petzval for visual use, I don't think so.  Most have 2 inch focusers which means they are limited in the field of view they can provide without vignetting.  Add in the back focus and spacing issues, the fact that scopes like the NP-101 use multiple ED elements, one front, one back, to obtain that color correction, I am just not seeing it.  I looked into making it happen but it just doesn't seem that the cards fall that way.  

 

I would like to hear of examples of successfully obtaining F/5 focal ratios visually to obtain the same well corrected, well illuminated fields possible with scopes like the NP-127, the NP-101 and the FSQs, though I guess it gets a little tricky with the FSQs because of backfocus with a diagonal. Never tried it myself.

 

Jon Isaacs