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Astro Physics 130EDT f/8 - how to really find out if air- or oilspaced?

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#51 LMO

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Posted 16 December 2017 - 04:51 AM

...

 

The entire serial number is SF58285:

SF = Starfire

5 = 5 inch diameter

8 = f/8 (nominally f/8.35)

285 = 285th 5 inch telescope made by Roland (NOT the 285th in this series, nor the 285th in this particular run, but the 285th 5 inch telescope of all types ever made by Roland up to this point). During a run, the serial numbers are only added as each set is tested and complete - and that is why the tube is not labelled with a serial number, only the edge of the lens set is, written there by Roland. Other marks which can be seen, especially on the 'older' optics are alignment marks for the rotation of the elements.

 

At some point Roland switched serial numbering to its current format. DDDFFSSS:

DDD= diameter in millimeters

FF = focal ratio

SSS = serial number

 

From everything I have gleaned over the years, there were 2 production runs of five inch Starfire EDT telescopes and both were 100% oil spaced. There were several prior makes and smaller runs of 5 inch telescopes which were NOT EDT, some of which were air spaced. The first runs of 5" EDT were possibly made from some surplus 155mm glass which did not make the cut for edge defects or inclusions or whatever reason. These telescopes are labeled f8 on the lens cell but are nominally f8.35. (155mm f/7.1 cut down to 130mm results in f/8.35). As well, there is absolutely no point in remaking tooling to build slightly different focal ratios. These telescopes are effectively identical to the later run of Starfire f/8.35 EDT scopes.

There was one run of 130 EDT f/8.35 scopes labelled as such on the cell which were made over a two year split run period. These were possibly made directly from new glass but used the same tooling as was used with the 155 f7 scopes. These were 130EDT were produced only for this period and then dropped from production as almost the entire demand was for the faster f/6 130EDF (nominally f/6.3!) scopes.  ...

 

At any rate, as a visual observer, Thomas Back absolutely loved the Starfire EDT. I have a friend with the f8 and another with the f8.35. At some point I hope we can get these scopes together for a night of side by side viewing pleasure.

 

 

The information on serial-number conventions of AP scopes provided in this post is helpful and welcome.  But it appears that the serial numbers of the much discussed AP 130 f8.35 FPL-53 versions departed somewhat from these conventions.  There was a long CN thread in 2014 discussing prices of used AP scopes and focused on one particular offering of a used f8.35 that included several reports of f8.35 serial numbers, for both those in the first run, marked 'f8' on their rings, and those in the second run, marked 'f8.35.'  

<http://www.cloudynig...fractor-prices- plummeting/>

 

The serial-number reports were summarized in that thread, also by M13 Observer, as follows:

 

"Awesome, so now we 'know'. For AP130EDT telescopes, 131xxxEDF or 131EDFxx are the serial numbers of the AP130EDT f8.35 using FPL-53. We can make an assumption that the first run, likely ALL engraved with F8 on the retaining ring, goes from 131000EDF to least 131026EDF, and if Roland's comments can be relied upon, likely to around 131032EDF. The second and final run marked 131EDF33 (?) to at least 131EDF60, and likely to 131EDF64 is engraved with F8.35 on the retaining ring. Not definitive but probably quite close."

 

The f8.35 serial numbers thus had '131' in the 'aperture-diameter (mm)' field, included the design designation 'EDF' either after the actual serial number in the first run, or before it in the second run, and did not include a focal-length designation.  (While the f8.35's design is in the 'EDF' group, it was named an 'EDT' to avoid confusion with the shorter focal length AP 130 f6 model offered at the same time; <http://astro-physics...edt/130f8edt>.)

 

M13 Observer's post in the present thread is absolutely right about Thomas Back's admiration for the AP 130 f8.35.  In his 'Brief History of Astro-Physics Lenses,' he singled it out with the phrase "what a sweet telescope," and elsewhere cited it as ""truly Roland's finest moment" among AP scopes he had inspected, and as the inspiration for design of his own legendary TMB 130 f9.23 (aka 'f9.25') to replace it.  See TMB's comments in <https://groups.yahoo...s/topics/26535>

 

Thomas Back's own AP 130 f8.35 was from the first run; the TMB 130 f9.25 was designed and produced after that run and before the second run.  That sequence is described in a fascinating account of the history of TMB's 130 f9.25 by 'MrGrytt' (Harvey), relating his own involvement in it.  He reported that, disappointed in the apparent discontinuation of the AP 130 f8.35 after the first run and before he had become eligible to buy one, he pressed Thomas Back to design a substitute.  The result was the TMB 130 f9.25, and Harvey obtained essentially the first available production model of that scope, then was informed of the second run of AP f8.35's and the rise of his application for one to the top of the AP list.  So, in the end, he got one of those, too!  The story was outlined by Harvey in CN thread <https://www.cloudyni...to-tmb-optical/> and is well worth reading.

 

    Larry


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#52 LMO

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Posted 16 December 2017 - 05:11 AM

"At any rate, as a visual observer, Thomas Back absolutely loved the Starfire EDT."  

 

According to Roland all early FPL-52 EDT’s used a mating element that resulted in perfect color correction, that mating element later became unavailable in sufficiently good quality suitable for use in astronomical telescopes, I believe that happened sometimes in mid nineties, the next best mating elements that was used in later FPL-53 triplets required some minor aspherics to make up for less than ideal mating element available at the time.

.

Vahe

It is not entirely clear what mating glass was used with FPL-53 for the AP 130 f8.35's and the 'sibling' AP 155 f7 EDF's, of which the f8.35's were essentially stopped-down versions.  (This sibling relationship was described by Thomas Back, with more praise for the f8.35 - "the new AP 130EDT is really the 155EDF 
stopped down to 5.1-inches, and the level of color, spherical 
and spherochromatism is the best of all the production apo-
chromats that

Roland has ever made." <https://groups.google.com/forum/#!topic/sci.astro.amateur/xYPcsqwy4Fk%5B1-25%5D>.  The relationship has been confirmed elsewhere by Roland.)

 

As Vahe noted Roland has indicated that "ZKN7 is the ideal mate for FPL53 theoretically," but that there are significant problems in obtaining satisfactory batches of it and working with it, and that, eventually, he "totally abandoned this material." <http://www.astromart...ws_id=&page=>. 

 

In another post, <https://groups.yahoo.../messages/38409>, Roland elaborated on this issue -- "In the past, one could get essentially perfect color correction in an 
oiled lens using ZKN7 and FPL52 or FPL53 as the center element. ZKN7 is not in good supply as is BK7, neither is it always delivered with good internal homogeneity. Therefore to use this material is always a gamble." He added. however that "BK7, when used as the mating element(s) to FPL53, results in almost perfect color correction," and that "BK7 is almost 100% reliable as a top quality material for objective lenses and can be gotten to any size desired."  Consistent with another part of Vahe's post, Roland had also noted that "If we use FPL53 as the ED element, then a great combination is to use two elements of BK7 surrounding the ED.  [But] Unfortunately, in order to eliminate

the spherical aberration, 5th order and coma all at the same time, this combination of glasses requires extensive aspherization if the lens is oiled." (The same post by Roland also discusses the tradeoffs between oil-  and air-spaced designs.)

 

In the 'History of Astro-Physics Lenses' cited in my previous post here, Thomas Back indicated that "The first EDT design used ZKN-7 crown glass and FPL-52 ED glass. The last runs of the smaller EDT models used the same crown glass but FPL-53 ED glass. They were even better corrected for monochromatic and polychromatic aberrations."   This implies that satisfactory ZNK7 could still be obtained for the 'smaller' AP scopes.

 

So it appears that some production AP models did involve the 'ideal' pairing of ZNK7 with FPL-53, but it's not clear which ones.  The very well corrected f8.35's admired by Back (and sibling 155 f7's) might have been among them, but I have not found an explicit statement confirming that.

 

    Larry


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#53 donadani

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Posted 16 December 2017 - 05:28 AM

Hi Larry,

 

welcome infos! 

 

Well - with starting the discussion about the 130EDT at f/8,35 now we have the third mystery about these EDT´s wink.gif

 

1. air-spaced vs. oil-spaced

2. FPF52 vs. FPL53

3. f/8 vs. f/8.35

 

about 1.)

 

I thought for a long time to have one of the air-spaced scopes - but finally I had not as you can read above. So I never have seen a real air-spaced 130EDT until today and now start to believe that all 130EDT´s are maybe oil-spaced just as M13 Oberserver mentioned.

 

about 2.) and 3.)

 

The correction of both of my EDT´s is very good! I have a Takahashi TSA-102 as well as a TOA-150 which are well known as some of the best corrected scopes around - both of them have a perfect startest. Until now I still have not compared them 1 to 1 against the EDT´s - but I will for sure! wink.gif

 

What I saw right now is that both EDT scopes are very, very good corrected in terms of color- as well as in terms of spherical correction. I would really love to compare them directly to an f/8.35 example too to see if there is any difference...

 

cs

Chris


Edited by donadani, 16 December 2017 - 05:30 AM.


#54 Roragi

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Posted 16 December 2017 - 10:25 AM

I really am the only guard the oiled in vertical position when not used? In fact when I detect that in the star test the disk is not completely round because it is stored horizontally, I read here in cloudynights that the oiled ones have to be stored vertically, as my friend told me. Although the amount is minimal oil I understand that everything stays in one place causing this image that is only seen extrafocal.

 

Roberto.



#55 vahe

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Posted 16 December 2017 - 03:46 PM

"Well - with starting the discussion about the 130EDT at f/8,35 now we have the third mystery about these EDT´s wink.gif

3. f/8 vs. f/8.35

What I saw right now is that both EDT scopes are very, very good corrected in terms of color- as well as in terms of spherical correction. I would really love to compare them directly to an f/8.35 example too to see if there is any difference..."

 

 

The choice of glass used in various 130 f/8’s is not necessarily the entire story, there is one other variable that defines their quality.

.
The older EDT’s, all of them, date back to pre-interferomety period of AP, Peter Ceravolo set up the interferometer for AP sometimes in mid nineties, so I assume that the better corrected late model f/8,35 was figured with interferometer and in green light.

.
Now, this is just a guess on my part, but my guess is based on a lens evaluation report that I received from AP specifically for my 155 f/9 EDT, in that report Roland stated that my lens was originally figured in yellow light, that is 593 nm, I am simply assuming that all pre-interferometry triplets were all figured in the same light.

.
How much of a difference all this makes? I do not know.

.

Vahe



#56 LMO

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Posted 16 December 2017 - 10:19 PM

Vahe is right again.  The introduction of interferometry for lens testing was noted in Thomas Back's 'Brief History of Astro-Physics Lenses' as an important step, along with use of an 'Opticam CNC glass surface profiler and an U of R magnetic polishing machine,' around the time the new EDT and EDF designs using FPL-53 glass were developed.

 

I and others have cited Roland's description of the successive cycles of interferometry testing and hand re-figuring to correct errors that were required to achieve the high performance, including extremely high Strehl ratios, for each individual AP scope.  It seems worth citing again for any not yet familiar with it -

<http://www.astromart...ws_id=&page=89>

 

There has been the suggestion that this degree of hand re-figuring (including aspheritization) is not required for the new, air-spaced, all spherical designs AP is now producing.  One also wonders whether interferometrically guided re-figuring could now be computer automated, or perhaps already is, with the expertise of opticians such as Roland 'taught' to machines.

 

     Larry



#57 donadani

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Posted 17 December 2017 - 02:47 AM

I really am the only guard the oiled in vertical position when not used? In fact when I detect that in the star test the disk is not completely round because it is stored horizontally, I read here in cloudynights that the oiled ones have to be stored vertically, as my friend told me. Although the amount is minimal oil I understand that everything stays in one place causing this image that is only seen extrafocal.

 

Roberto.

 

Hi Roberto,

 

storing an oil spaced scope horizontal or vertical is just another topic often discussed wink.gif There are two fractions around - some belive scopes has to be stored vertically and some not. Wolfgang Rohr for example suggests to do so as he can see the difference when testing an oil spaced lens - so he suggests to store it at least some hours or days vertically before doing any testing (but never saw him testing a AP-130EDT btw.) 

 

On the other side when looking to the boxes for my "old" EDT´s they have handles on each side - so it´s just not possible to store the scope vertically inside this boxes... As mentioned one of the scopes is from 1994 as Christine wrote to me and I guess it was stored for all the time horizontal in its box - the startest I saw with it now at calm air was top notch, that´s all I can say about it...

 

On the other side... I store my CFF-185 (that is oil-spaced as well) in vertical position too - just to be on the safe side! wink.gif - and btw. the box allows this in this case too.

 

 

 

"Well - with starting the discussion about the 130EDT at f/8,35 now we have the third mystery about these EDT´s wink.gif

3. f/8 vs. f/8.35

What I saw right now is that both EDT scopes are very, very good corrected in terms of color- as well as in terms of spherical correction. I would really love to compare them directly to an f/8.35 example too to see if there is any difference..."

 

 

The choice of glass used in various 130 f/8’s is not necessarily the entire story, there is one other variable that defines their quality.

.
The older EDT’s, all of them, date back to pre-interferomety period of AP, Peter Ceravolo set up the interferometer for AP sometimes in mid nineties, so I assume that the better corrected late model f/8,35 was figured with interferometer and in green light.

.
Now, this is just a guess on my part, but my guess is based on a lens evaluation report that I received from AP specifically for my 155 f/9 EDT, in that report Roland stated that my lens was originally figured in yellow light, that is 593 nm, I am simply assuming that all pre-interferometry triplets were all figured in the same light.

.
How much of a difference all this makes? I do not know.

.

Vahe

 

Vahe is right again.  The introduction of interferometry for lens testing was noted in Thomas Back's 'Brief History of Astro-Physics Lenses' as an important step, along with use of an 'Opticam CNC glass surface profiler and an U of R magnetic polishing machine,' around the time the new EDT and EDF designs using FPL-53 glass were developed.

 

I and others have cited Roland's description of the successive cycles of interferometry testing and hand re-figuring to correct errors that were required to achieve the high performance, including extremely high Strehl ratios, for each individual AP scope.  It seems worth citing again for any not yet familiar with it -

<http://www.astromart...ws_id=&page=89>

 

There has been the suggestion that this degree of hand re-figuring (including aspheritization) is not required for the new, air-spaced, all spherical designs AP is now producing.  One also wonders whether interferometrically guided re-figuring could now be computer automated, or perhaps already is, with the expertise of opticians such as Roland 'taught' to machines.

 

     Larry

 

Vahe, Larry - do I understand your points right here - that you guess the newer EDTs as well as all the EDFs and GTs should be "better" as they are corrected to green light (instead yellow for the older EDTs) and inteferometry is used in the manufacturing process?

 

Well of course technology steps forward but I´m not sure if this is true in generell... just using interferometry is not a guarantor for a top optic and I´m pretty sure some "old" scopes are better then some "newer" ones - but of course I´m with you that it could help. 

 

My reference for a good optic is an older, pre-interferometry-era-made and hand figured Takahashi FC-100N - that was measured by Wolfgang Rohr with a strehl of 98,9 in green light - enclosed you find the report.

 

 

 

 

 

Next to that I learned that if you wanna have a really good analysis with interferometry - you should do the test more often in different directions (at least two, shifted 90° better more!) to see all the errors of a lens or mirror. My CFF-185 for example was reworked because the preowner saw some noncircular stars in one corner of the field. As it came out after some research this error was only visible at a specified direction on the interferrogram. To correct it the complete lens was reworked (coating removed, repoolished, new coating - be sure, not many companys would do that!!!). The result now is a perfect lens in any direction of the interferogram. 

 

So what I want to say is that interferometry don´t makes good lenses alone and that very good lenses were just possible before interferometry was used - the startest is a very sensitive tool here and I guess the last 1-2% of strehl are always a bit of just luck...

 

Coming back to the EDT´s we are talking about here - I was just suprised, that the startests of my two samples are so very, very close that I couldn´t see any difference - all that without interferometry and at least two years between their manufacturing - and btw. both are very close to my reference scopes smile.gif

 

cs

Chris


Edited by donadani, 17 December 2017 - 06:19 AM.


#58 vahe

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Posted 17 December 2017 - 10:08 AM

"So what I want to say is that interferometry don´t makes good lenses alone and that very good lenses were just possible before interferometry was used - the startest is a very sensitive tool here and I guess the last 1-2% of strehl are always a bit of just luck...

 

Coming back to the EDT´s we are talking about here - I was just suprised, that the startests of my two samples are so very, very close that I couldn´t see any difference - all that without interferometry and at least two years between their manufacturing - and btw. both are very close to my reference scopes smile.gif"

 

 

 

My opinion; interferometry does not necessarily guarantee quality, interferometry if used properly will result in consistency of the end product.

.
One example that I can offer here is for my own 155 EDT f/9, there is a test of this Apo on Astro-foren.com under “A1041 Astro-Physics EDT APO 155-1395 Super-APO anno 1990 f9”, check out the test results, this is a sample of pre-interferometry lens that tested exceptionally well, on the other hand my own 155 EDT was re-tested by Roland with interferometer using green light and the results were 0.925 Strehl, that is unacceptable to say the least, this example proves that there could be considerable variation in quality in pre-interferometry lenses.

.
I could not find a similar test for 130 f/8 but your visual tests tells me that what you have is one of the better ones.

.
As for figuring an Apo in green light versus other wavelengths consider the fact that Zeiss APQ’s were figured in white light, primarily optimized for visual. 

The bottom line, you can safely drop all this technical mumbo-jumbo and enjoy the views.

.

Vahe



#59 M13 Observer

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Posted 17 December 2017 - 12:01 PM

 

...

 

The entire serial number is SF58285:

SF = Starfire

5 = 5 inch diameter

8 = f/8 (nominally f/8.35)

285 = 285th 5 inch telescope made by Roland (NOT the 285th in this series, nor the 285th in this particular run, but the 285th 5 inch telescope of all types ever made by Roland up to this point). During a run, the serial numbers are only added as each set is tested and complete - and that is why the tube is not labelled with a serial number, only the edge of the lens set is, written there by Roland. Other marks which can be seen, especially on the 'older' optics are alignment marks for the rotation of the elements.

 

At some point Roland switched serial numbering to its current format. DDDFFSSS:

DDD= diameter in millimeters

FF = focal ratio

SSS = serial number

 

From everything I have gleaned over the years, there were 2 production runs of five inch Starfire EDT telescopes and both were 100% oil spaced. There were several prior makes and smaller runs of 5 inch telescopes which were NOT EDT, some of which were air spaced. The first runs of 5" EDT were possibly made from some surplus 155mm glass which did not make the cut for edge defects or inclusions or whatever reason. These telescopes are labeled f8 on the lens cell but are nominally f8.35. (155mm f/7.1 cut down to 130mm results in f/8.35). As well, there is absolutely no point in remaking tooling to build slightly different focal ratios. These telescopes are effectively identical to the later run of Starfire f/8.35 EDT scopes.

There was one run of 130 EDT f/8.35 scopes labelled as such on the cell which were made over a two year split run period. These were possibly made directly from new glass but used the same tooling as was used with the 155 f7 scopes. These were 130EDT were produced only for this period and then dropped from production as almost the entire demand was for the faster f/6 130EDF (nominally f/6.3!) scopes.  ...

 

At any rate, as a visual observer, Thomas Back absolutely loved the Starfire EDT. I have a friend with the f8 and another with the f8.35. At some point I hope we can get these scopes together for a night of side by side viewing pleasure.

 

 

The information on serial-number conventions of AP scopes provided in this post is helpful and welcome.  But it appears that the serial numbers of the much discussed AP 130 f8.35 FPL-53 versions departed somewhat from these conventions.  There was a long CN thread in 2014 discussing prices of used AP scopes and focused on one particular offering of a used f8.35 that included several reports of f8.35 serial numbers, for both those in the first run, marked 'f8' on their rings, and those in the second run, marked 'f8.35.'  

<http://www.cloudynig...fractor-prices- plummeting/>

 

The serial-number reports were summarized in that thread, also by M13 Observer, as follows:

 

"Awesome, so now we 'know'. For AP130EDT telescopes, 131xxxEDF or 131EDFxx are the serial numbers of the AP130EDT f8.35 using FPL-53. We can make an assumption that the first run, likely ALL engraved with F8 on the retaining ring, goes from 131000EDF to least 131026EDF, and if Roland's comments can be relied upon, likely to around 131032EDF. The second and final run marked 131EDF33 (?) to at least 131EDF60, and likely to 131EDF64 is engraved with F8.35 on the retaining ring. Not definitive but probably quite close."

 

The f8.35 serial numbers thus had '131' in the 'aperture-diameter (mm)' field, included the design designation 'EDF' either after the actual serial number in the first run, or before it in the second run, and did not include a focal-length designation.  (While the f8.35's design is in the 'EDF' group, it was named an 'EDT' to avoid confusion with the shorter focal length AP 130 f6 model offered at the same time; <http://astro-physics...edt/130f8edt>.)

 

M13 Observer's post in the present thread is absolutely right about Thomas Back's admiration for the AP 130 f8.35.  In his 'Brief History of Astro-Physics Lenses,' he singled it out with the phrase "what a sweet telescope," and elsewhere cited it as ""truly Roland's finest moment" among AP scopes he had inspected, and as the inspiration for design of his own legendary TMB 130 f9.23 (aka 'f9.25') to replace it.  See TMB's comments in <https://groups.yahoo...s/topics/26535>

 

Thomas Back's own AP 130 f8.35 was from the first run; the TMB 130 f9.25 was designed and produced after that run and before the second run.  That sequence is described in a fascinating account of the history of TMB's 130 f9.25 by 'MrGrytt' (Harvey), relating his own involvement in it.  He reported that, disappointed in the apparent discontinuation of the AP 130 f8.35 after the first run and before he had become eligible to buy one, he pressed Thomas Back to design a substitute.  The result was the TMB 130 f9.25, and Harvey obtained essentially the first available production model of that scope, then was informed of the second run of AP f8.35's and the rise of his application for one to the top of the AP list.  So, in the end, he got one of those, too!  The story was outlined by Harvey in CN thread <https://www.cloudyni...to-tmb-optical/> and is well worth reading.

 

    Larry

 

Thanks for pointing that out Larry. In this case I wanted to concentrate on the original runs of the f8 labeled EDT scopes. Further to this, the serial numbering schemes across all of the Astro-Physics' scopes seem to have some other variations from time to time as well. I don't even know if Roland could sort it all out exactly at this point. I hope he kept some good records LOL! Enough to know he made excellent telescopes and to be able to enjoy twenty plus year old optics performing comparably to competing current high end apochromats.


Edited by M13 Observer, 17 December 2017 - 12:03 PM.


#60 donadani

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Posted 20 December 2017 - 01:10 PM

Enough to know he made excellent telescopes and to be able to enjoy twenty plus year old optics performing comparably to competing current high end apochromats. 

 

 

 

 

I could just compare one of my EDT´s against a EDF GT.

 

For high mag. visual on the moon I prefered the views in the EDT as they where a bit more steady, calmer and so easier to see. I believe the longer f-ratio of the EDT´s is a big plus for visual only.

 

No difference in details. Color was no theme at any magnification with any scope. But didn´t looked explicit for it - will do that maybe later.

 

So for just visual I prefere the EDT over the EDF GT - for any photo ambitions of course the EDF with flattener will be preferable.

 

There was no winner and no looser - but some are better for this and others better for that. All of these scopes are outstanding!



#61 vahe

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Posted 21 December 2017 - 04:18 PM

"So for just visual I prefere the EDT over the EDF GT - for any photo ambitions of course the EDF with flattener will be preferable."

 

 

Not necessarily, check out the image of M45 by Chris Cook taken with 130 f/8 EDT.

https://500px.com/ph...&user_id=716342

 

Vahe


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#62 donadani

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Posted 21 December 2017 - 04:33 PM

Woww - great!!! - just as I saw them visually wink.gif

 

ok barely... but I guess the EDF is not behind of that at AP

 

Biggest plus of the GT - where no other scope can beat it yet for sure - in my view is portability!!! saw one taking it in three pieces and take it by hand luggage with ease when traveling by plane - you can´t do that with an EDT or any other scope in that class - nor that easy with the new GTX - really great "little" scope!

 

EDIT: Stop!... -  you CAN do it! ...if your name is "nicknacknock" lol.gif


Edited by donadani, 21 December 2017 - 04:39 PM.


#63 Chris Cook

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Posted 22 December 2017 - 11:03 AM

"So for just visual I prefere the EDT over the EDF GT - for any photo ambitions of course the EDF with flattener will be preferable."

 

 

Not necessarily, check out the image of M45 by Chris Cook taken with 130 f/8 EDT.

https://500px.com/ph...&user_id=716342

 

Vahe

My 130EDT is serial #SF58227 made in May 1992 and from what I can gather here on CN and other online sources, it is a FPL-52/ZKN-7 design.

http://www.abmedia.c...les/130EDT.html

 

Chris



#64 donadani

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Posted 22 December 2017 - 11:41 AM

Hi Chris - thanks for that link! great scope and as mentioned before - geat photo of the pleiades waytogo.gif

 

Do you painted the lenscell adapter by yourself or is that original from AP?

 

You changed from a EDF-GT to the older EDT and as I see mainly for photo is that right? but why? wasn´t you satisfied with that GT? That EDF´s faster f-ratio should be a pro to keep exposure time low for any deep-sky object - shouldn´t it? 

 

cs

the other Chris wink.gif



#65 Chris Cook

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Posted 22 December 2017 - 11:53 PM

Hi Chris - thanks for that link! great scope and as mentioned before - geat photo of the pleiades waytogo.gif

 

Do you painted the lenscell adapter by yourself or is that original from AP?

 

You changed from a EDF-GT to the older EDT and as I see mainly for photo is that right? but why? wasn´t you satisfied with that GT? That EDF´s faster f-ratio should be a pro to keep exposure time low for any deep-sky object - shouldn´t it? 

 

cs

the other Chris wink.gif

Hi Chris,

I had the GT for about 8 years and loved it.  I was basically looking for a bit more FL.  I also bought it for planetary viewing when I don't have a camera attached.  Saturn last summer was pretty sweet at 260x.  I'll probably keep the EDT.  She's a special scope.

 

Chris


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#66 Chris Cook

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Posted 22 December 2017 - 11:56 PM

Do you painted the lenscell adapter by yourself or is that original from AP?

 

The lens cell has always been white.  Roland produced several scopes with white lens cells in the 90's.  Most of them seem to be in the 1991-1994 range.  The 6" f/9 doublet that he made for a very short time also had a white lens cell.

 

Chris



#67 The Mekon

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Posted 23 December 2017 - 01:42 AM

In early1991 I ordered an 127 F8 starfire.  Half way through the year I received the news that I would receive a 130EDT Starfire, as this model was replacing the 127mm   Of course I was quite pleased about this at the time.

The scope was shipped on 30th December 1991 - serial number SF 58197.  It must have been one of the earliest of the EDTs.   Kept the scope for 22 years, spending many wonderful nights with it.   I always thought it was an oil spaced design, though looking through the original paperwork, nothing indicates this.

Regretted selling it and bought a CFF 132 f7......


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#68 Jeff B

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Posted 23 December 2017 - 10:26 AM

As an additional data point, I have a pre-ED 5" F8 Starfire, S/N SF5887.  Not sure the production date but it has the white tube, not the earlier blue tube.

 

Jeff


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#69 donadani

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Posted 23 December 2017 - 02:01 PM

 

Hi Chris - thanks for that link! great scope and as mentioned before - geat photo of the pleiades waytogo.gif

 

Do you painted the lenscell adapter by yourself or is that original from AP?

 

You changed from a EDF-GT to the older EDT and as I see mainly for photo is that right? but why? wasn´t you satisfied with that GT? That EDF´s faster f-ratio should be a pro to keep exposure time low for any deep-sky object - shouldn´t it? 

 

cs

the other Chris wink.gif

Hi Chris,

I had the GT for about 8 years and loved it.  I was basically looking for a bit more FL.  I also bought it for planetary viewing when I don't have a camera attached.  Saturn last summer was pretty sweet at 260x.  I'll probably keep the EDT.  She's a special scope.

 

Chris

 

 

...the EDT definitely is a special scope - otherwise I wouldn´t have bought two of them ;)

 

 

As an additional data point, I have a pre-ED 5" F8 Starfire, S/N SF5887.  Not sure the production date but it has the white tube, not the earlier blue tube.

 

Jeff

 

Jeff - yepp, sorry but we nee a pic to proof it :)


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#70 The Mekon

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Posted 23 December 2017 - 04:03 PM

As an additional data point, I have a pre-ED 5" F8 Starfire, S/N SF5887.  Not sure the production date but it has the white tube, not the earlier blue tube.

 

Jeff

Jeff, Is that a typo?    Is it perhaps SF58187 which would make it 10 scopes before mine (pictured)?

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#71 Jeff B

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Posted 23 December 2017 - 10:15 PM

 

As an additional data point, I have a pre-ED 5" F8 Starfire, S/N SF5887.  Not sure the production date but it has the white tube, not the earlier blue tube.

 

Jeff

Jeff, Is that a typo?    Is it perhaps SF58187 which would make it 10 scopes before mine (pictured)?

 

Nope, not a typo.

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#72 The Mekon

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Posted 24 December 2017 - 03:00 AM

Thanks for confirming the number Jeff.   How to work out AP's serial numbering system?    From what I can gather, AP made around 40  127mm F8 Starfires, before making around 120 130EDT's.  The numbering system is far from sequential !

 

Amazing photo of the triplet lens.  Now I know why the front end is so heavy.



#73 donadani

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Posted 24 December 2017 - 04:01 AM

Yes! great photo - thanks!

 

Intersting that the numbers are written in different directions on hte middle and lower lens - always thought it´s some kind of mirroring effect when looking for them from outside.

 

Looks like you guys have some fun to pullout the lenses sometimes from the tubes ;)

 

cs

Chris



#74 Jeff B

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Posted 24 December 2017 - 12:02 PM

Not so much fun with this one Chris.

 

This old Starfire was in terrible shape when I got it as part of a deal from an estate.  Even though installed in the OTA for almost 15 years, the dew cap was off, the lens was left uncovered and the focuser uncapped.   The front surface was completely covered in what I hoped would be just dust.  The center of the rear element was also covered in dust and.....spider webs.   Also what caught my eye was that I saw no Kapton tape on the edges of the lens block, like you see in the photos above.  At first, I though it might be airspaced but saw no spacers between the elements.  So I was very suspicious and thought the lens may have been tampered with. 

 

As the OTA was part of the "package" with a couple of boxes of other stuff, including an AP 400 mount with the quartz drives (but no hand controller), I priced the entire deal so that the OTA was essentially free, that way there was no risk to me and I could part it out if I had to.  

 

When I got the scope home, I removed the lens block from the cell and very carefully cleaned both surfaces.  Well, they came out looking brand new. waytogo.gif .  and I photographed it as I thought it strange that there was not Kapton tape on the edges and it appeared to be cemented together.  There was also no buffer between the lens block and the cell's interior metal wall.  More suspicion.

 

I then reinstalled the lens block, collimated the focuser with a laser (did not need adjustment) and collimated the lens with a Cheshire eyepiece.  I was able to test it that very night (which, around here, is unusual when I get a new scope).

 

And the star test was terrible, confused1.gif with complete mush on one side of focus and sharp rings on the other.  I could not though find any astigmatism and color correction seemed fine.  The double, double actually looked rather good at high power with no signs of coma.  I suspected a turned edge and I verified that in DPAC along with a little bit of SA in green. I made a 4.5" aperture stop and that cleaned up the star test very nicely.  In DPAC there was now no turned edge but still a bit of SA in green but yellow-red looked very good.

 

So I got in touch with Christine at AP (She has always been incredibly helpful with the older equipment) and forwarded my information to her and she forwarded it to Roland.  He too suspected the lens had been tampered with and that the cement may be stressing the lens, causing the turned edge.  He suggested just stopping it to 120 mm but I could also return it for service where he would take it apart, realign it and oil & tape it....but it may or may not relieve the stress.  But I want a 127MM Starfire, not a 120MM one, so I took the chance and returned the lens a couple of months ago.  Roland confirmed what I saw and the lens was inducted into the service cycle, which can take a while as Roland works returns as time permits him to do so. 

 

As part of my communications with Roland, he confirmed that this lens was corrected more towards the yellow-red end of the spectrum rather than the green-blue end which was normal for this vintage lens.   

 

So we shall see what happens.

 

Jeff


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#75 M13 Observer

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Posted 24 December 2017 - 01:54 PM

 

 

As an additional data point, I have a pre-ED 5" F8 Starfire, S/N SF5887.  Not sure the production date but it has the white tube, not the earlier blue tube.

 

Jeff

Jeff, Is that a typo?    Is it perhaps SF58187 which would make it 10 scopes before mine (pictured)?

 

Nope, not a typo.

 

Nice! sn87. I wonder what the sn of the first FPL52 based 130 is? Is the retaining ring engraved and if so, is it labeled 130mm?

 

Edit -> Ah, I see in a follow up post that it is a 127mm / 5". Is the cell retaining ring engraved with mm or inches or neither? Truly interesting stuff.


Edited by M13 Observer, 24 December 2017 - 01:57 PM.



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