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Any APOs you would avoid?

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#51 GSBass

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Posted 05 April 2021 - 10:17 AM

Often miffs me to see post on refractors with collimating  issues, oldest design in telescope history and yet certain scopes even from high end manufactures still struggle, just hits me as something that would be standardized by now, I’ve heard my AT edl will have an adjustable cell while the regular ED does not, really no idea if I will ever have to adjust or why the design is different.... it honestly does not seem cost should be a consideration on this although it does seem more prevalent the more money you speed


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#52 Nippon

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Posted 05 April 2021 - 10:41 AM

Vixen and Takahashi doublet refractors used to have collimatable lens cells but they only adjusted the orientation of the cell to the tube. But neither company uses that kind of cell in their doublets anymore. I guess the manufacturing accuracy is such now that that is not needed. Where triplets get out of whack is the the orientation of the three lenses to each other. I think it's not an issue in most doublet designs because doublets just are not real sensitive to that.


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#53 csrlice12

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Posted 05 April 2021 - 10:46 AM

They ain't APOs, they ain't expensive, some are even collimatable....but for just general visual viewing bang for the buck refractor..... there's the ubiquitous 4" f9.7 achromat that will keep you occupied night after night.  Put it on a CG5 and it's a formidable photon machine.


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#54 Mirzam

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Posted 05 April 2021 - 10:58 AM

There are variables involved that make standardization difficult.  If the optical design entails air spacing and very steep curves, perhaps in an attempt to use cheaper glass, the sensitivity to de-centering can be high.  A well designed cell can deal with this sensitivity.  On the other hand, an oiled triplet with tightly nesting elements presents less de-centering tendency.  In other words, it’s all a function of optical design, intended use (color correction and f-ratios), glass types, and of course, cost.

 

JimC


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#55 Bomber Bob

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Posted 05 April 2021 - 11:08 AM

I know a while back SV was only testing the inner 95% of the diameter.

 

Markus has made comments along the lines that, unlike APM, most APO makers test less than 100% of the aperture - but very few disclose that fact.



#56 Bomber Bob

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Posted 05 April 2021 - 11:14 AM

There are variables involved that make standardization difficult.  If the optical design entails air spacing and very steep curves, perhaps in an attempt to use cheaper glass, the sensitivity to de-centering can be high.  A well designed cell can deal with this sensitivity.  On the other hand, an oiled triplet with tightly nesting elements presents less de-centering tendency.  In other words, it’s all a function of optical design, intended use (color correction and f-ratios), glass types, and of course, cost.

 

JimC

With the exception of 2 local (driving distance) scopes, ALL of mine had to be shipped to The Swamp, so no way I'm gonna plunk down $$$$ on a top-tier APO if it has a fixed lens cell.  Just because it left the shop perfectly aligned doesn't mean it'll be that way when I get my grubby hands on it.


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#57 NC Startrekker

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Posted 05 April 2021 - 11:28 AM

I know a while back SV was only testing the inner 95% of the diameter.

 

Markus has made comments along the lines that, unlike APM, most APO makers test less than 100% of the aperture - but very few disclose that fact.

Bob, see my earlier post #46. 



#58 Deadlake

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Posted 05 April 2021 - 11:41 AM

Satisfaction, Control and Prestige are all fine reasons but I would think there has to be serious profit involved for SV to make that move. SV is a business and has expenses and employees to pay and the employees can’t take prestige to the bank.

Bob


The other item is moving from one OEM to another.
I know that APM is moving it’s non LZOS 107 mm from Sharp Star to Long Perng due to QC issues. I think that China can produce scopes just as good as anyone, however at that scale of production it becomes harder to be consistent and that’s what is tripping them up. No other telescope manufacturers have to produce at the scale so it’s new and difficult.
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#59 Deadlake

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Posted 05 April 2021 - 12:11 PM

Vixen and Takahashi doublet refractors used to have collimatable lens cells but they only adjusted the orientation of the cell to the tube. But neither company uses that kind of cell in their doublets anymore. I guess the manufacturing accuracy is such now that that is not needed. Where triplets get out of whack is the the orientation of the three lenses to each other. I think it's not an issue in most doublet designs because doublets just are not real sensitive to that.


Tecnosky 125 mm doublet can be collimated, and according the dealer it makes it a sale of the century item as he can tweak it. I know as well the mark II AG tube for LZOS has a collimating flange to make adjustments easier.

I wonder how many box shifters out out there, i.e. dealers who cannot collimate a scope?

#60 Mike W

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Posted 05 April 2021 - 04:19 PM

Tele Vue NP101, some have collimation issues & they have to be sent back to Tele Vue for fixing, you pay both ways I understand. And TV don't do emails either.


Only if you are very clumsy with one! All are tested at Televue before going out the door. My TV is twenty years old and looks and performs like the day it was new!!!!!!!!!!!!5.jpg

Edited by Mike W, 05 April 2021 - 04:23 PM.

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#61 russell23

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Posted 05 April 2021 - 04:46 PM

I think I would avoid the AP 130 GTX.  In fact, I think everyone on the waiting list should just remove their name and look for something else.  


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#62 NC Startrekker

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Posted 05 April 2021 - 05:08 PM

Only if you are very clumsy with one! All are tested at Televue before going out the door. My TV is twenty years old and looks and performs like the day it was new!!!!!!!!!!!!attachicon.gif5.jpgattachicon.gif5.jpgattachicon.gif5.jpg

Couldn’t agree more. Kind of tiring of what I will call an “urban legend” concerning the fragility of collimating with Tele Vue Petzals. Have there been instances of mis-collimating with the TV NP’s?  Of course. Any more so than triplets or even doublets for that matter? I sincerely doubt it. In fact, I’ve only read about three instances in my several decades on this forum. Those were from actual owners (I find the “legend” perpetuated mostly by hear say from folks who have never owned one). I’ve certainly seen more posts of miscollimation with triplets. So, anecdotally I think the instances are far fewer with the Petzals. I own a 101 and, until this past year, also had a 127.  No issues.  I never abused them but they traveled to numerous Star parties and dark sites with never an issue. TV scopes are extremely well built.  Frankly, I worry more about my Taks.



#63 PKDfan

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Posted 05 April 2021 - 05:48 PM

Hi all! Another data point for excellence in China made, Synta to be exact. The 4" doublet F/9 fpl-53/bk7 that has been around for well almost forever. Mine did 65× per inch on Mars at opp. and was perfect. I marvel everytime I have good seeing and the moon well placed o.m.g.!

I think I was the receipient of a proud Chinese worker taking pride in producing an excellent quality thing.

I am itching to do some shootouts at star parties against the BIG boys. I think my underdog might surprise!

 

Clear skies & Good seeing


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#64 Jon Isaacs

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Posted 05 April 2021 - 05:59 PM

Couldn’t agree more. Kind of tiring of what I will call an “urban legend” concerning the fragility of collimating with Tele Vue Petzals. Have there been instances of mis-collimating with the TV NP’s?  Of course. Any more so than triplets or even doublets for that matter? I sincerely doubt it. In fact, I’ve only read about three instances in my several decades on this forum. Those were from actual owners (I find the “legend” perpetuated mostly by hear say from folks who have never owned one). I’ve certainly seen more posts of miscollimation with triplets. So, anecdotally I think the instances are far fewer with the Petzals. I own a 101 and, until this past year, also had a 127.  No issues.  I never abused them but they traveled to numerous Star parties and dark sites with never an issue. TV scopes are extremely well built.  Frankly, I worry more about my Taks.

 

It's no legend. As a mechanical engineer/researcher, i consider it a design flaw. Here's the problem:

 

The NP-101 objective cell is held in place with three screws. The tilt of the objective is held in alignment by these screws. The holes in the objective cell are larger than the screws so this allows a certain amount of room adjusting the tilt. 

 

It also means that it's possible that if the cell is bumped somehow, it can get knocked out of alignment.  In my mind as an engineer, there should be set screws that allow positive adjustment of the tilt. As it was, I built my own...

 

When I purchased my NP-101 used in 2010, someone had already fussed with the alignment screws and at 300x I could see the diffraction rings were not radially symmetrical.. 

 

I built myself a collimation jig so I could loosen the screws and tweak the collimation. This is that story:

 

https://www.cloudyni...g-my-tv-np-101/

 

post-3933-14073119232914_thumb.jpg

 

Since I wrote that, others have had issues as well.

 

The good news is that since I collimated it in 2010, it has remained in collimation despite having traveled at least 10,000 miles in its soft case in the bed of a pickup plus taking a nose dive into the dirt when I bumped into it and knocked the tripod over..  the Telrad helped absorb the energy.

 

Telrad Saves the Day CN.jpg
 
Jon

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#65 2112_Mike

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Posted 05 April 2021 - 06:45 PM

Not sure who posted the comment about the 115 mm refractor that was barely good at 30 times per inch and that it would only be good enough possibly to give to a kid starting out? I think that's somewhat foul play considering the probable price difference between that refractor and a Takahashi or a astrophysics or whatever high end you want to swing at it.
Some of us don't have that kind of money. Doubtful that a 'kid' is going to have that kind of money either by the time they have to get the scope, mount,eyepieces etc to make everything work. I definitely don't consider Chinese apochromat refractors low end. Also 30x per inch is on the low end for my eastern scopes, that I do know.
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#66 John Huntley

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Posted 05 April 2021 - 07:02 PM

I would be cautious about purchasing in TAL Apolar 125 without carefully star testing it before committing. I tried two examples a few years back, one was delivered with a smashed internal element and the replacement was optically intact but one of the elements was clearly not quite aligned properly so the star test was not really satisfactory. Fortunately these were loaned to me to review so I had not paid for them but I would have been very concerned if I had paid £1,500 to purchase one.

 

The Apolar 125 used a 6 element, 3 groups optical design which did not use ED glass as far as I'm aware. It had potential but collimation was definitely a return to factory job (the manual said so) and the factory is in Siberia !

 

This is the optical layout:

 

cache_15426448.jpg?t=1381090090


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#67 Jaimo!

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Posted 05 April 2021 - 07:37 PM

I know its a doublet but I wouldn’t recommend a WO Z61 Mark2 due to pinched optics and odd corner star shapes in all directions. Had mine replaced and same thing again. It is well made but even with zero tenson on the 4 rear lens cell screws it still is pinched badly when below 32F. Big stars look like they exploded! The only way i can image is by putting 4 lens heater dew straps around it. Some people have no issues where some are nightmares. I don’t expect much from a low cost doublet scope but it has made me rethink WO products made recently. Your milage may vary!

It sounds like a spacing/flattener issue, especially with issues in the corners.  I also had issues in the corners with the 61a and the ASI294MC Pro, until I got the correct backspacing, it may be more prevalent with a full frame/mirrorless camera.  I don't think pinched optics are only limited to the corners, but across the field...?  I may be wrong...

 

There are a lot of these little scopes out there, the WO Z61, AT60ED, Apetura 60EDR, and TS had one also...


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#68 NC Startrekker

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Posted 05 April 2021 - 08:03 PM

Jon, yours is one of the three examples of miscollimation by a owner that I can actually document. And, yours is more than likely the result of the previous owners tampering. The history of yours since you recollimated it reinforces my point. The TV Petzals are far from fragile. Evidence to the contrary. They are no more fragile than any other and hold up well to any reasonable use and transport. Sometimes they go a little beyond the call of duty when we astronomers accidentally require them to. wink.gif


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#69 Jon Isaacs

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Posted 05 April 2021 - 09:31 PM

Jon, yours is one of the three examples of miscollimation by a owner that I can actually document. And, yours is more than likely the result of the previous owners tampering. The history of yours since you recollimated it reinforces my point. The TV Petzals are far from fragile. Evidence to the contrary. They are no more fragile than any other and hold up well to any reasonable use and transport. Sometimes they go a little beyond the call of duty when we astronomers accidentally require them to. wink.gif

What you wrote:

 

"Those were from actual owners (I find the “legend” perpetuated mostly by hear say from folks who have never owned one)."

 

For some reason the previous owner thought it needed collimation. 

 

I'm sure there are far more than three documented cases.  I documented the design flaw.  That's why they're more fragile than other designs. The collimation is not positive..  

 

Now, avoiding the NP-101 is a different issue.  If you want the flat-flat field in a visual scope, it comes with territory, you just need to be aware that it may need collimation at some point.  

 

Jon



#70 teashea

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Posted 05 April 2021 - 10:09 PM

With the exception of 2 local (driving distance) scopes, ALL of mine had to be shipped to The Swamp, so no way I'm gonna plunk down $$$$ on a top-tier APO if it has a fixed lens cell.  Just because it left the shop perfectly aligned doesn't mean it'll be that way when I get my grubby hands on it.

Almost all of the Takahashi refractors I have purchased lately are fixed cells.  They are all excellent.  They do not need to be adjustable because Takahashi has engineered them in such a way that they work with fixed cells.


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#71 Mitrovarr

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Posted 05 April 2021 - 11:56 PM

I dunno, not many. Reaching back to think of all of the negative reports on apos I've heard of, there aren't a lot.

 

I've heard a bunch of negative reports about the Takahashi Sky 90 although I've never personally seen one (or any Takahashi).

 

The old Meade 5-7" apochromats (particularly the 7") are notorious for having bad lens cells and becoming hopelessly miscollimated. That's probably the worst experience with apos I've heard over the years.


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#72 Jeff Morgan

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Posted 06 April 2021 - 02:53 AM

Couldn’t agree more. Kind of tiring of what I will call an “urban legend” concerning the fragility of collimating with Tele Vue Petzals. Have there been instances of mis-collimating with the TV NP’s?  

 

Urban legend?

 

Well I own a NP101is and I just happen to have the receipt for factory collimation. A roughly $500 round-trip.

 

Should I send it to you via pm or would you like me to post it here?


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#73 Jeff Morgan

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Posted 06 April 2021 - 03:01 AM

Not sure who posted the comment about the 115 mm refractor that was barely good at 30 times per inch and that it would only be good enough possibly to give to a kid starting out? I think that's somewhat foul play considering the probable price difference between that refractor and a Takahashi or a astrophysics or whatever high end you want to swing at it.
Some of us don't have that kind of money. Doubtful that a 'kid' is going to have that kind of money either by the time they have to get the scope, mount,eyepieces etc to make everything work. I definitely don't consider Chinese apochromat refractors low end. Also 30x per inch is on the low end for my eastern scopes, that I do know.

 

I posted it.

 

And yes, I would recommend one of those as starter scopes. Low cost, decent build, and encompassing most of the qualities refractors are generally purchased for.

 

Just not the pushing up the power aspect.

 

In other words, you still do get what you pay for.

 

Did you have any other questions?

 

And since your signature line (currently) shows six (6) telescopes (plus whatever other equipment you have to support those six telescopes), I am not shedding any tears for you as to not having the money to afford one (1) higher end scope.



#74 Jon Isaacs

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Posted 06 April 2021 - 08:22 AM

And yes, I would recommend one of those as starter scopes. Low cost, decent build, and encompassing most of the qualities refractors are generally purchased for.

 

Just not the pushing up the power aspect.

 

In other words, you still do get what you pay for.

 

 


 

My 120 Eon definitely out performs my NP-101 at high magnifications.  

 

30x per inch in a 120mm is only 140x, it does 257x on the planets nice and clean.  

 

I got what I paid for, more aperture.

 

Jon


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#75 2112_Mike

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Posted 06 April 2021 - 08:51 AM

Ok, you win, not going to argue on this post.  I would much rather have a variety of scopes to pick from on a given night based on seeing conditions then just one scope.  30X per inch is still lower than I have used on my 130 to give what 'I' consider fantastic views of  Jupiter and Saturn.  Seeing conditions permitting I have used my 6mm Delos without image break down.  Never done a side by side with a better refractor because I frankly just don't know anyone around here that owns one. I'm not out to gauge performance.

I just don't believe the marginally better performance of a scope that cost 3x mine is worth it...that is just my opinion.

Oh, and I don't believe either of the two APO scopes I own would be scopes to avoid.




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