153 replies to this topic

[topomountain]

Does anyone have any experience with this type of scope, particularly how it performs vis a vis the NP-101?

 

https://www.cloudyni...ion-vixen-120s/

i have the 4 element na120  version

 

it is an awesome low to mid mag scope, i never knew what a flat field was until i looked through it...

 

not sure if its as bog and heavy or bigger than the at125edl, but i think it is a must try for a person who has tried so many scopes! 

[bobhen]

To each their own. I’ve owned several achro’s and been unimpressed fa@tless. None remain in the stable. As stated I’m very sensitive to CA and it’s going to be there in a fast achro. As an imager, a less than stellar field sticks out like a sore thumb. You might have a different view or different expectations, everyone is different. I provided an opinion that I stand by. You made your opinion and I dare say you stand by that. The OP now has a few opinions to add to the mix. The OP might be happy with the view that’s provided, I wouldn’t, knowing the imperfections of the system it would be something looked for and found. Like I say, I stand by my comment. 

I have currently 35+ scopes so have enough to compare against as well, including two NP-101’s being converted to an NV binoscope.

The APO comment you added bold to makes me think the reviewer is suspect at best and to top it off this completely makes it not reliable. 
“Overall the contrast with another scope I’m testing – the Vixen VMC95 Maksutov – was interesting. The Vixen of course shows little CA, but in almost every other respect its view was inferior, even on Jupiter where you’d think it would excel.”

 

The second not far comment you added bold text to what’s the reviewers definition of not far?
Like a meat substitute that many folks say tastes just like meat? I disagree there too.

 

It’s all subjective and individual observer dependent. 

I respect your opinion but my experience matches the 2 reviewer's experience's and the 2 reviewer's experiences match each other's. Both are very experienced observers and have reviewed many apo refractors. 

 

You won't see CA on stars at the low powers of 15x - 25x with the 102 F5. Only when power is increased does CA become evident. And at those low powers, the views of big nebula and rich star fields, CA will be no different than with a same size apo. And put an OIII or DS filter on the scope and on an apo, and the view will be the same.

 

I use mine in the daytime at at 25-power and in the bright sunlight, CA is very subdued and hardly seen. You really have to look for it. At night, at those low powers on dim, amorphous deep sky objects, there's just not enough light to trigger color in the eye. The same is true with achromatic binoculars. 

 

The title of the tread is: A Poor Man's  4" Tele Vue. NOT a poor man's 4 refractor that can do exactly what a $4,000 TV 101 can do at 25x on deep sky AND at 300x on the moon and planets.

 

Bob

Edited by bobhen, 27 July 2024 - 07:52 AM.

[Terra Nova]

Welp, I guess there goes my idea for a poor man's Genesis thread when I get a TSFLAT2 for my StarTravel 102. 

 

I would have to agree with Phil on that one too. Just not the same. If you had a Genesis, SDF, TV101, or NP101 you would know that. It’s okay to love fast achros if that’s your cuppa, I don’t mean to denegrate them in any way, but they are what they are no matter how you dress them up.

[Echolight]

I owned a pure Vixen 120S for a number of years. It’s not an apo but color is very well corrected, about the same as an F12 or F13 120mm achromat. It also delivers pretty wide fields (not as wide as an ST120) and the field is fairly flat. It’s really a multipurpose telescope, in a whole other league compared to an ST120. I’ve had three ST120s. In my book, ST120s (and ST102s) are cheap thrills but they’re strictly fast RFTs. The 120s can deliver good views of the moon and planets at 200X, (w/ 4mm Delite). In fact, on one night of excellent seeing, I pushed mine up to 266X with a 3mm Delite and the views of Jupiter and Saturn were quite serviceable. Note the 120S is the five element model, the petzval unit has three elements. It’s a level higher than the more common NA120 (Vixen called that one a neoachromat) which has four elements and not as good of color control. I liked mine a lot and only sold it because it’s a fairly large telescope and I was moving from my house into a condo where it would have no longer been practical.

 I got the little five pound ST102 because it's about a third the size and weight of that thing. (A quarter or less including the mount)

....and I like cheap thrills 

 

A readily available better version of the ST80(in any guise) to me. And better than the SV48. A simple sturdy 2" focuser, no fuss, no fiddle, and one hand out the door on the mount five degree four inch widefield for camping or travel, no weight no worry go anywhere anytime chunk in the trunk fun. 

 

(Dare I say better than an NP101 in these regards?)

 

It's an aid to naked eye viewing that you don't have to hold or lay in a recliner to use.

 

A half binocular on steroids.

 

Although I wouldn't call it an RFT (but neither is a 120S.) so much as a UltraWideTelescope (which a 120S is not).

 

For me, an RFT is an 8 inch f4, PACKING a 2.9° view with faint stars.

Edited by Echolight, 27 July 2024 - 09:34 AM.

[Terra Nova]

Why would you look at the moon at ~15x magnification using a 4" ~f/5 refractor? An ST102 with the 28mm UWA provides a 4.6 degree FOV, 4.2 degrees with the 30mm UFF I have.

 

I think the point being made is that even at ~15X, when you look at a star field and don’t notice glaring CA, it’s still there, as tiny almost invisible violet halos around the stars, (which show up as star bloat in an image, even tho you may miss it given the sensitivity of an individual’s eyes, around 0.4μ). However, point that telescope at the moon and there it is! A thin, bright and vivid color band of opposing sides of the spectrum, neatly (and brightly) portrayed along the limb. I used to enjoy fast achromats, but what with gradually acquiring apos and making comparisons, and even more so, having cataract surgery on both eyes, and I was pretty well done with them.

[Terra Nova]

 I got the little five pound ST102 because it's about a third the size and weight of that thing. (A quarter or less including the mount)

....and I like cheap thrills 

 

A readily available better version of the ST80(in any guise) to me. And better than the SV48. A simple sturdy 2" focuser, no fuss, no fiddle, and one hand out the door on the mount five degree four inch widefield for camping or travel, no weight no worry go anywhere anytime chunk in the trunk fun. 

 

(Dare I say better than an NP101 in these regards?)

 

It's an aid to naked eye viewing that you don't have to hold or lay in a recliner to use.

 

A half binocular on steroids.

 

Although I wouldn't call it an RFT (but neither is a 120S.) so much as a UltraWideTelescope (which a 120S is not).

 

For me, an RFT is an 8 inch f4, PACKING a 2.9° view with faint stars.

For me is ≥ 80mm and ≥ 4° but it’s all right defining things differently. Different strokes after all.

Edited by Terra Nova, 27 July 2024 - 09:44 AM.

[Echolight]

I would have to agree with Phil on that one too. Just not the same. If you had a Genesis, SDF, TV101, or NP101 you would know that. It’s okay to love fast achros if that’s your cuppa, I don’t mean to denegrate them in any way, but they are what they are no matter how you dress them up.

Yourself and Phil seem to overlook a few words in what was the original title and in my comment. And to me, those words allow the scopes in question to be a consideration for at least part of, or most of the reason someone would buy an NP101.

I mean there's lots of cheap scopes that can show more high power details than an NP101. Bigger scopes albeit.

But it's the wide flat field that is something those big scopes can't replicate. And that includes the 120S, which somehow entered the conversation.

And S? What's that for anyway?

Short? No... Super? Uh uh. Sorta? 

 

The "poor man's" version is easily overlooked without a keen optic I guess. 

 

But if your reason for getting an NP101 is for the wide flat field of view, I see no reason to foul a person's Wheaties just because they are poor and want to use a flattener with a widefield achromat to achieve a similar widefield view.

[Terra Nova]

Here’s my ‘poor woman’s NP101’. It’s an AT90CFT with a f.l. of 540mm, (the same as the NP101). With a 72° 36mm eyepiece I can get 15X and almost 5° with an exit pupil of 6mm. This scope replaced my TV Genesis SDF (also 540mm f.l.). The same eyepiece with the SDF gave me a 6.8mm e.p. But I haven’t noticed any decrease in brightness, perhaps because it’s less glass, (triplet vs. doublet+petzval unit). Stars are bright and pinpoint, the sky is black, ie. views are very sharp and contrasty. No CA what so ever was observed when viewing the moon at 15X or 150X. The scope is shorter and lighter than the SDF. I’ve not used a TS Flat but I haven’t seen the need for a flattener either. Only being a visual observer, I haven’t really noticed any field curvature with it that didn’t seem to be more a result of a particular l.p. eyepiece. Overall, I couldn’t be happier with this scope as a replacement for the SDF. I wanted something that was easier for me to tote around, mount, etc. and this is that, and with the same f.l. and same suite of eyepieces, it’s an easy transition. A new AT90CFT costs about a third what an NP101 goes for new, maybe less; I haven’t priced one in a while and won’t be doing so.

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Edited by Terra Nova, 27 July 2024 - 10:56 AM.

[Terra Nova]

Yourself and Phil seem to overlook a few words in what was the original title and in my comment. And to me, those words allow the scopes in question to be a consideration for at least part of, or most of the reason someone would buy an NP101.
…

But if your reason for getting an NP101 is for the wide flat field of view, I see no reason to foul a person's Wheaties just because they are poor and want to use a flattener with a widefield achromat to achieve a similar widefield view.

You seem to be the person here who want’s/needs to make something more of this than it is. No one is fouling anyone’s Wheaties. You can call anything whatever you like, but calling it something doesn’t necessarily make it so. It’s as simple as that. To put it another way, comparisons in relative terms are rarely the same as comparisons in absolute terms.

 

Also, I’m having trouble reconciling your opening statement with your closing statement. Firstly, you state: “be a consideration for at least part of, or most of the reason someone would buy an NP101.“ implying that it’s justification for a person to buy an NP101. But then, in your last statement you say “because they are poor and want to use a flattener with a widefield achromat to achieve a similar widefield view.” implying that the person is unable to buy an NP101? But circular reasoning aside, numerous alternative have been posted by others, most importantly being the possibility of buying a used Genesis for $800 bucks. They are out there for that price if one waits and that is only around twice the cost of a 102mm fast achromat and a reducer/flattener, and is certainly a much more apt comparison.

 

Enjoy your Wheaties.

[topomountain]

maybe another way to look at this subject is this:

 

a tv101 or its cousins is a 100mm at f5ish

 

an st102 is the same

 

both very similar in light gathering and fov, d a tsflat2 and the st102 has a flatter field

 

while the st102 is much lighter and cheaper, it will not do very well on medium or high mags, but can still view at over 100x

 

to compare my achros, i have the following fpl 53 refractors:

at72ed2

eon 80 fpl53

orion ed80 f7.5

starfield 102 f7.5 fpl53

vixen ed102ss f6.5

sw 120ed fpl53

 

these all look way better at ANY mag to me than all but my sweet celestron 102 f10 achro that is magic, and my vintage 60 f11

 

so, i expect the tv101 is better at any mag, but how much better with the at28uwa, because i know my pentax 40 will probly have too large of an ep to be best in that scope anyway

 

and to the comment on the vixen 120s, my na120 is boss next to my st120 in the field it shows, not quite as wide but much better views, and i expect the tv wide field cousins are as jon says, as good as it gets!

[tony_spina]

Here’s my ‘poor woman’s NP101’. It’s an AT90CFT with a f.l. of 540mm, (the same as the NP101). With a 72° 36mm eyepiece I can get 15X and almost 5° with an exit pupil of 6mm. This scope replaced my TV Genesis SDF (also 540mm f.l.). The same eyepiece with the SDF gave me a 6.8mm e.p. But I haven’t noticed any decrease in brightness, perhaps because it’s less glass, (triplet vs. doublet+petzval unit). Stars are bright and pinpoint, the sky is black, ie. views are very sharp and contrasty. No CA what so ever was observed when viewing the moon at 15X or 150X. The scope is shorter and lighter than the SDF. I’ve not tried it with a TS Flat but I am considering getting one to play with. I couldn’t be happier with this as a replacement as I wanted something that was easier for me to tote around, mount, etc. and this is that. A new AT90CFT costs about a third what an NP101 goes for new, maybe less; I haven’t priced one in a while and won’t be doing so.

The AT90CFT is a great scope but at $1600 new it's not a poor man's TV101.  Even if you could get one used it's not going to be cheap 

[Terra Nova]

The AT90CFT is a great scope but at $1600 new it's not a poor man's TV101.  Even if you could get one used it's not going to be cheap 

Very true, I was looking at it mostly in relative terms. With money recouped from the sale of my Genesis SDF, it was only $200 more.

[maniack]

But circular reasoning aside, numerous alternative have been posted by others, most importantly being the possibility of buying a used Genesis for $800 bucks. They are out there for that price if one waits and that is only around twice the cost of a 102mm fast achromat and a reducer/flattener, and is certainly a much more apt comparison.

Used TV scopes are quite hard to find, they exist but you might be waiting a long time for one to show up for sale. You also have to be in the US, otherwise fat chance.

 

The cost also goes up quite a bit when you take into account the mounting requirements. An ST102 is ~7lbs and under 22 inches long. A Genesis is 4 lbs heavier and 4 inches longer.

 

The Genesis (non-SDF) is still an achromat, albeit with better color correction considering the focal length of the doublet component is twice as long as an ST102's. But with the larger size and general unavailability I'd rather go for a new Sharpstar 94EDPH triplet at $1000. I've seriously considered that Sharpstar but am leaning very much to the lighter and cheaper ST102 as my cheap alternative to the NP101.

 

That being said, the OP was asking about a $1300 kit that's a bit heavier than a Televue 4" petzval. For the OP a used Genesis SDF sounds like a better alternative. The caveat is that they are in New Zealand, so finding one there might just be impossible.

[alnitak22]

You seem to be the person here who want’s/needs to make something more of this than it is. No one is fouling anyone’s Wheaties. You can call anything whatever you like, but calling it something doesn’t necessarily make it so. It’s as simple as that. To put it another way, comparisons in relative terms are rarely the same as comparisons in absolute terms.

 

Also, I’m having trouble reconciling your opening statement with your closing statement. Firstly, you state: “be a consideration for at least part of, or most of the reason someone would buy an NP101.“ implying that it’s justification for a person to buy an NP101. But then, in your last statement you say “because they are poor and want to use a flattener with a widefield achromat to achieve a similar widefield view.” implying that the person is unable to buy an NP101? But circular reasoning aside, numerous alternative have been posted by others, most importantly being the possibility of buying a used Genesis for $800 bucks. They are out there for that price if one waits and that is only around twice the cost of a 102mm fast achromat and a reducer/flattener, and is certainly a much more apt comparison.

 

Enjoy your Wheaties.

Thank you, Terra and well said!

[Terra Nova]

Used TV scopes are quite hard to find, they exist but you might be waiting a long time for one to show up for sale. You also have to be in the US, otherwise fat chance.

 

The cost also goes up quite a bit when you take into account the mounting requirements. An ST102 is ~7lbs and under 22 inches long. A Genesis is 4 lbs heavier and 4 inches longer.

 

The Genesis (non-SDF) is still an achromat, albeit with better color correction considering the focal length of the doublet component is twice as long as an ST102's. But with the larger size and general unavailability I'd rather go for a new Sharpstar 94EDPH triplet at $1000. I've seriously considered that Sharpstar but am leaning very much to the lighter and cheaper ST102 as my cheap alternative to the NP101.

 

That being said, the OP was asking about a $1300 kit that's a bit heavier than a Televue 4" petzval. For the OP a used Genesis SDF sounds like a better alternative. The caveat is that they are in New Zealand, so finding one there might just be impossible.

https://www.cloudyni...unt-and-tripod/

[maniack]

https://www.cloudyni...unt-and-tripod/

Unfortunately the plane ticket from NZ to come and pick that up from you would have been a bit much.

[Phil Cowell]

Well we disagree. As for the garbage about a 4” achro performing better than a VMC for planetary work well that makes the first reviewers opinion’s ridiculous at best.

You might not see CA I’m pretty sure I would. 
 

I respect your opinion but my experience matches the 2 reviewer's experience's and the 2 reviewer's experiences match each other's. Both are very experienced observers and have reviewed many apo refractors. 

 

You won't see CA on stars at the low powers of 15x - 25x with the 102 F5. Only when power is increased does CA become evident. And at those low powers, the views of big nebula and rich star fields, CA will be no different than with a same size apo. And put an OIII or DS filter on the scope and on an apo, and the view will be the same.

 

I use mine in the daytime at at 25-power and in the bright sunlight, CA is very subdued and hardly seen. You really have to look for it. At night, at those low powers on dim, amorphous deep sky objects, there's just not enough light to trigger color in the eye. The same is true with achromatic binoculars. 

 

The title of the tread is: A Poor Man's  4" Tele Vue. NOT a poor man's 4 refractor that can do exactly what a $4,000 TV 101 can do at 25x on deep sky AND at 300x on the moon and planets.

 

Bob

[Phil Cowell]

Poor man’s NP101 would be a scope as capable but for less money. That is not.

If folks don’t want to hear diverse answers don’t ask the question. If you don’t want the wheaties fouled don’t put them in a porcelain bowl with the large white mints.

Will the achro produce wide field views some will enjoy, yes. Is it anyway the equal of an NP-101? No.

 

 

The "poor man's" version is easily overlooked without a keen optic I guess. 

 

But if your reason for getting an NP101 is for the wide flat field of view, I see no reason to foul a person's Wheaties just because they are poor and want to use a flattener with a widefield achromat to achieve a similar widefield view.

[maniack]

Poor man’s NP101 would be a scope as capable but for less money. That is not.

If folks don’t want to hear diverse answers don’t ask the question. If you don’t want the wheaties fouled don’t put them in a porcelain bowl with the large white mints.

Will the achro produce wide field views some will enjoy, yes. Is it anyway the equal of an NP-101? No.

How would TV be selling these scopes if there were something as capable for less money? I and others are interested in something the can provide similar visual views at a cheaper price point.

 

Not everyone has 10s of thousands of dollars to spend on 35 telescopes and AP equipment. If they had the budget this question wouldn't need to be asked.

 

Well we disagree. As for the garbage about a 4” achro performing better than a VMC for planetary work well that makes the first reviewers opinion’s ridiculous at best.

You might not see CA I’m pretty sure I would. 
 

The question isn't if any CA is visible. Obviously if you're starting with an achromat there is the potential for CA, even for wide-field views. Or you can start with an APO like the OP suggested but compromise elsewhere. How much CA is objectionable depends on the individual. Many folks said an AT80ED with its FPL51 glass would not show objectional CA for visual use. I bought one and was not happy with the CA on Jupiter, and its one of the reasons I "downgraded" to an AT72EDII. On the other hand I have an ST80 and don't find the CA objectional for wide-field usage. I can use the AT72EDII for solar system objects or one of my SCTs. But the real issue I have with the ST80 compared to the AT72EDII is field curvature, as I can use a TSFLAT2 with the 72 (and go wider with 2" eyepieces, but that's less important for me). An ST102 comes with a 2" focuser so that issue isn't there. I'm fairly sure I can deal with the CA in those wide views. I can't justify paying 10x the price for the improvement the TV provides, especially given the low usage such an instrument would have for me. As much as I'd love to have an NP101 or FSQ106 they are not practical expenditures for me. You and others can justify the cost, which is totally fine.

[alnitak22]

How would TV be selling these scopes if there were something as capable for less money? I and others are interested in something the can provide similar visual views at a cheaper price point.

 

Not everyone has 10s of thousands of dollars to spend on 35 telescopes and AP equipment. If they had the budget this question wouldn't need to be asked.

 

The question isn't if any CA is visible. Obviously if you're starting with an achromat there is the potential for CA, even for wide-field views. Or you can start with an APO like the OP suggested but compromise elsewhere. How much CA is objectionable depends on the individual. Many folks said an AT80ED with its FPL51 glass would not show objectional CA for visual use. I bought one and was not happy with the CA on Jupiter, and its one of the reasons I "downgraded" to an AT72EDII. On the other hand I have an ST80 and don't find the CA objectional for wide-field usage. I can use the AT72EDII for solar system objects or one of my SCTs. But the real issue I have with the ST80 compared to the AT72EDII is field curvature, as I can use a TSFLAT2 with the 72 (and go wider with 2" eyepieces, but that's less important for me). An ST102 comes with a 2" focuser so that issue isn't there. I'm fairly sure I can deal with the CA in those wide views. I can't justify paying 10x the price for the improvement the TV provides, especially given the low usage such an instrument would have for me. As much as I'd love to have an NP101 or FSQ106 they are not practical expenditures for me. You and others can justify the cost, which is totally fine.

Monkey Shoulder is a very nice blended Scotch. I’ve enjoyed it. However it is NOT a poor man’s Macallan 18 yr old Single Malt no matter how much one tries to make it so. Same with this thread. Use what you want and what you can afford and enjoy. Absolutely nothing wrong with that. But why try to claim it’s something that it’s not?  Puzzling. 

[Phil Cowell]

I think you have repeated what I said. It depends on the individual how bad the CA impacts the enjoyment of the scope. My personal view is it will impact the quality of the view by bloating of stars and fringing around bright stars. You didn’t ask about other scopes only the comparison. If you found the fringing on bright objects objectionable in the AT80ED, good luck with the achro.

If you willing to live with that then fine, you don’t need to convince me otherwise because you won’t. If you just want cheer leaders then phrase your question to elicit that type of response. 
A question was asked and it got diverse answers. Thats how it works.
 

The question isn't if any CA is visible. Obviously if you're starting with an achromat there is the potential for CA, even for wide-field views. Or you can start with an APO like the OP suggested but compromise elsewhere. How much CA is objectionable depends on the individual.

Edited by Phil Cowell, 27 July 2024 - 06:09 PM.

[Echolight]

Poor man’s NP101 would be a scope as capable but for less money. That is not.

If folks don’t want to hear diverse answers don’t ask the question. If you don’t want the wheaties fouled don’t put them in a porcelain bowl with the large white mints.

Will the achro produce wide field views some will enjoy, yes. Is it anyway the equal of an NP-101? No.

Where's that donkey imoji when you need it... 

[Phil Cowell]

Yeah there’s always folks who keep pushing the dead horse.

 

Where's that donkey imoji when you need it... 

[topomountain]

i think terra nova did not find the poor mans tv101, just the elderly persons np101, or shall i say downsized np101/genesis 

 

im not sure which one i want most, the tv101 or the at90cft..... im sure the at90cft would get more use from me!

 

probly would prefer a tv127is but my daughter needs a better used car for college out of town

 

i think my poor mans tv101 will have to be the vixen ed102ss 650mm and bite the bullet for a tsflat2, then i can try on the st102, st120, ed102ss and see how that works out....

 

any good odds on the ed102ss tsflat2 and vixen xw40 winning that shootout?

[Exnihilo]

I have the NA 140, and since I also have an Omni 150 achro to compare, I’d just guesstimate the NA has about 1/3 the chromatic aberration of the rather extreme Omni. The NA also has a very flat field, which is really nice.  Still, it’s no Televue. Not that I feel any real need to actually GET a Televue.