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watcher
Carpal Tunnel
*****

Reged: 11/21/07

Loc: St. Louis, MO
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: APM M.Ludes]
      #5216706 - 05/11/12 08:35 AM

My only concern with a scope of 140mm is keeping the moment arm low enough to mount the scope easily on a CG-5 class mount. I think 7.5 would just about make it feasible, otherwise we might as well go with the 6" F/8 if the 140 will need more mount to be comfortable with.

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Alvan Clark
sage


Reged: 03/13/10

Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: APM M.Ludes]
      #5216813 - 05/11/12 10:04 AM

Quote:


so we recomment minimum F/7.5

can you ask around so I get many feedbacks whats acceptable ?





Doesn't this website have a "poll" feature? Someone could put up a survey but everyone will still want something different. Going with 7.5 or 8 would seem to be the best compromise.

I'm disappointed that FPL53 will not be used. I'm happy with my 120mm FPL53 and would have taken a chance on the 140mm. Now, I think I need to look through one of these before buying any. If you can have these ready by WSP 2013 you'll have to bring them there and let people have a look.

One bad review about how much color they have could effect sales.


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Jan Owen
Pooh-Bah


Reged: 02/12/06

Loc: Sun City West, Arizona
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: APM M.Ludes]
      #5216820 - 05/11/12 10:09 AM

I have said since long before this thread started, that f/9 was probably going to be necessary to achieve the level of desired correction. Others seem to want shorter tubes, but have difficulty understanding that adequate focal length is needed to achieve decent correction...

If you don't allow sufficient focal length to achieve a higher level of correction, you may as well settle for an achromat, which at least offers low cost for it's lower level of performance...


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Sol Robbins
Carpal Tunnel
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Reged: 12/01/03

Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: Jan Owen]
      #5217103 - 05/11/12 01:00 PM

Markus & Jan,

That's why I thought it might be better to have a 140mm lens as a retrofit on the 6" Synta tube. The correction of a 140mm at f/8.57-f/l 1200mm and, hopefully, overall lens quality/cost would be a better trade-off versus the 10mm aperture increase with less sphero-chromatic correction.


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APM M.Ludes
Vendor (APM Telescopes)
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Reged: 05/01/03

Loc: Germany
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: Sol Robbins]
      #5217410 - 05/11/12 03:48 PM

Sol

10 mm more aperture with a bit lesser good chromatical correction , or 10 mm less with a bit better correction ....aperture will win


Think about the real live use of such telescopes

Objects with high contrast you may use the power 2 times aperture ( 140 mm lens 280 power and 152 mm lens 304 power), on low contrast objects ( like Jupiter) you use normal 1.5 times aperture ( 140 mm lens 210 times , 152 mm lens 225 times ), at this level or NORMAL max powers you will always see more details with the 10 mm bigger lens

Also : if you want a bit better correction on the 152 , just put a 140 mm mask in front and you have what you want :-)


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watcher
Carpal Tunnel
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Reged: 11/21/07

Loc: St. Louis, MO
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: APM M.Ludes]
      #5217809 - 05/11/12 08:40 PM

I know the example that you give of the correction of an F/30 6" achro would be absolutely fine for me, and well worth the additional cost over an achro.

The 1050mm focal length of an F/7.5 140mm, I think, would just about be good on a CG-5 (entry level) goto EQ. If you go any longer on that scope, you might as well just do the 6", because both would do better on a bigger mount.


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HCR32
sage


Reged: 08/27/10

Loc: Australia
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: Jan Owen]
      #5217824 - 05/11/12 08:49 PM

Quote:

I have said since long before this thread started, that f/9 was probably going to be necessary to achieve the level of desired correction. Others seem to want shorter tubes, but have difficulty understanding that adequate focal length is needed to achieve decent correction...

If you don't allow sufficient focal length to achieve a higher level of correction, you may as well settle for an achromat, which at least offers low cost for it's lower level of performance...




I agree with your opinion. If people are going to influence the production of these scopes based on what mount they have at home that's going to rob us of better colour correction then, I'd say markus make the f/l what ever it needs to be to achieve best correction. I'm sure people will find a way around their mounting issues.


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watcher
Carpal Tunnel
*****

Reged: 11/21/07

Loc: St. Louis, MO
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: APM M.Ludes]
      #5217837 - 05/11/12 08:56 PM

Quote:

The 140 F/7 FPL 53 will not comes as FPL, it turned out that even at 200 pc the FPL53 with mating glas is to expensive, so we will switsch it to the same design as the 152F/8 then the price will be hold or more close to $ 3,000, but right now we finishing first the 152 design, then we move to the 140 model

However we plan to release a 160 mm F/7.5 doublet in a price range between 5000 and 5500 $ retail. Here the cost are known by today




I'm still good with the lesser corrected version up to F/7.5, but wasn't your original estimate with the FPL-53 based on a 300 unit minimum order? Just wondering if the 100 unit difference is the cause for the difference?


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watcher
Carpal Tunnel
*****

Reged: 11/21/07

Loc: St. Louis, MO
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: HCR32]
      #5217870 - 05/11/12 09:17 PM

Quote:

Quote:

I have said since long before this thread started, that f/9 was probably going to be necessary to achieve the level of desired correction. Others seem to want shorter tubes, but have difficulty understanding that adequate focal length is needed to achieve decent correction...

If you don't allow sufficient focal length to achieve a higher level of correction, you may as well settle for an achromat, which at least offers low cost for it's lower level of performance...




I agree with your opinion. If people are going to influence the production of these scopes based on what mount they have at home that's going to rob us of better colour correction then, I'd say markus make the f/l what ever it needs to be to achieve best correction. I'm sure people will find a way around their mounting issues.




If people have the kind of money it takes to upgrade a mount AND buy a 5 1/2 or 6" ED, there are already options at APM.If people are just interested in the best color correction possible there are already options. F/8 achros sold big numbers for a reason. you don't need a 6000.00 mount to use one. OK, maybe you can go to F/9 or 10, and still be good on an Atlas class mount, but then your leaving out all the folks that have been wishing for an upgrade to their C6Rs for years.My preference for a shorter 140mm isn't based on the mount I have at home. It's based on the sheer number of entry level mounts out there. I think Markus would sell an awful lot of scopes if everyone interested could get by with a mount they have at home.


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HCR32
sage


Reged: 08/27/10

Loc: Australia
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: watcher]
      #5218086 - 05/11/12 11:51 PM

Problem is people are happy to buy cheap with the understanding that they aren't buying a flagship model and will be quick to criticize in review. It happens in life people forget where they come from. "rages to riches", and if Marcus stamps it APM then reputation is at stack. Business is business.

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watcher
Carpal Tunnel
*****

Reged: 11/21/07

Loc: St. Louis, MO
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: HCR32]
      #5218114 - 05/12/12 12:10 AM

We're talking about color correction here. not quality. Does D&G have a good reputation. These scopes are over 3000 U.S. They are ED doublets not super APOs. I just can' understand why some still can't grasp that this is a type of scope that there is a demand for. There are achros and APOs, right? Why is it so difficult to comprehend that there is an "in between" type. And the type of scope has nothing to do with the quality of the scope.

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Sol Robbins
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Reged: 12/01/03

Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: APM M.Ludes]
      #5218129 - 05/12/12 12:19 AM

Quote:

Also : if you want a bit better correction on the 152 , just put a 140 mm mask in front and you have what you want :-)




Very good. :-)


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Vondragonnoggin
Post Laureate
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Reged: 02/21/10

Loc: Southern CA, USA
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: Sol Robbins]
      #5218490 - 05/12/12 10:29 AM

I see this is going to lose sight of the spark that started this whole idea rather quickly - this was a desire for a middle ground scope! Middle ground in price between triplet apo and doublet achro. Middle color correction which is why F/8 was picked. Originally requested to get something in at $3000 or less that had about half the color correction of the triplet.

All I see is more and more emphasis on color correction now.

That was not the idea of the thread or main concern. The thread originator wanted better correction than his 152 achro, but not perfect color. Many agreed at the time with it.

Markus, I think you should stick with the original idea here that so many chimed in on that they would be interested in.


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Astrojensen
Post Laureate
*****

Reged: 10/05/08

Loc: Bornholm, Denmark
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: Vondragonnoggin]
      #5218615 - 05/12/12 12:00 PM

I am still very much interested in the original idea. I was even willing to settle for a 150mm f/8 ED with the color correction of an f/20 achro, a level of color correction Markus considered unacceptable and decided to go for one with the correction of an f/30, which should keep me happy for many years, perhaps life.

Refractors with perfect color correction are widely available, the problem is that people doesn't seem willing to accept that such scopes are costly to produce and want perfection at an entry level price. While this is understandable, people should also try to understand that if they can't afford perfection, compromises must be sought. Wherein this compromise lies can vary and what is an acceptable compromise varies from person to person. For me, I am willing to sacrifice a bit of color correction and ultra-low cost to get a very good, but not perfect (color wise) lens at a moderate cost.

Markus, please carry on with the 150mm f/8 ED project!


Clear skies!
Thomas, Denmark


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Jan Owen
Pooh-Bah


Reged: 02/12/06

Loc: Sun City West, Arizona
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: Vondragonnoggin]
      #5218635 - 05/12/12 12:16 PM

I agree, for the most part.

What I've been asking for, for the last couple years, has been essentially a 6" EON class scope. Not a premium scope; just an upper middle class scope. A doublet, like the EON. I don't care what kind of ED glass is used, as long as the RX delivers about the same level of correction.

I've said I think the focal ratio will have to be on the long side, to allow decent correction without the need of top grade glass, or a triplet design. That was another way to save cost by staying with less expensive glass, without giving up too much performance. Without the extra performance, everyone might as well just buy, or keep their present achros, if they already have one.

I have built, over time, an 8" f/6 Newtonian, with a superb Mike Spooner primary and high quality Antares secondary, with central obstruction below 20%, and have recently further enhanced that scope's capability. Right now, it can easily stand in for a 6.5" top quality APO. So my urgency level has dropped somewhat... Oh, and I just weighed it on an accurate scale, and it weighs exactly 16 pounds. So, aside from it's lever-arm from the tube length, it doesn't require a massive mount.

I'm still interested in an EON class 6" doublet, but I certainly have NO issue if the concensus final scope here comes out to be something different than I'd originally asked for.

If it doesn't meet my needs, I already have a scope that can outperform it in any category I'm likely to use it in, so I won't be overly disturbed by it not happening. And I have a 12" scope that can outperform the 8" handily.

I do worry that sometimes one or two loud squeaky wheels get all the attention, so I've tried to not be overly pushy about my interests. Of course, that hasn't stopped others.

The suggestion to poll the group for what their opinions are, as a group, would probably give Markus a better feel for what the market really is, versus deciding what person presents the most arguments, or the best arguments.

It will, after all, be all those customers who will buy or not buy the scope he decides to make, and not the select few squeaky wheels, that will make this a package that's good for both the buyers and the maker, instead of just a few select folks.


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Astrojensen
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Reged: 10/05/08

Loc: Bornholm, Denmark
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: Jan Owen]
      #5218665 - 05/12/12 12:40 PM

Squeeeak...

150mm f/8 ED

Squeeak...

150mm f/8 ED

Squeeak...




Clear skies!
Thomas, Denmark


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tomharri
sage
*****

Reged: 09/19/08

Loc: USA
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: Astrojensen]
      #5218686 - 05/12/12 12:55 PM

Stick with the 6" f/8 replacement lens for all the Meade and Celestrons out there, f/9 at the most if you can supply an extension tube.

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APM M.Ludes
Vendor (APM Telescopes)
*****

Reged: 05/01/03

Loc: Germany
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: tomharri]
      #5218918 - 05/12/12 03:51 PM

the 152 F/8 ED doublet is in progress and will come , also with lens in cell and adapters for your excisting tubes.

I will try to check how a 140 F/7 performs via a F/7.5 , we will check some excisting smaller apos and if I feel the faster F/7 is still fine, then we keep F/7, it it shows to much color, then maybe F/7.5


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Jan Owen
Pooh-Bah


Reged: 02/12/06

Loc: Sun City West, Arizona
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: APM M.Ludes]
      #5218936 - 05/12/12 04:09 PM



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watcher
Carpal Tunnel
*****

Reged: 11/21/07

Loc: St. Louis, MO
Re: New 6" F/8 ED Doublets from APM Telescopes new [Re: APM M.Ludes]
      #5219198 - 05/12/12 07:27 PM

Quote:

the 152 F/8 ED doublet is in progress and will come , also with lens in cell and adapters for your excisting tubes.

I will try to check how a 140 F/7 performs via a F/7.5 , we will check some excisting smaller apos and if I feel the faster F/7 is still fine, then we keep F/7, it it shows to much color, then maybe F/7.5




You da man Markus! I have a feeling you'll be going through multiple runs of these scopes.


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