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Astro-Physics Zeiss Comparison - GTX First Light

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#1 daveCollins

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Posted 25 June 2016 - 03:32 PM

I will start off this review with a first light for the GTX, followed by a comparison with an AP 130 EDF from 1998, and then the last portion will be an Astro-Physics – Zeiss APQ comparison.

 

The scopes compared in this review are as follows:

 

  •         Astro-Physics        130mm f6    EDF (1998)            FL 780mm
  •         Astro-Physics        130mm f6.3 GTX (2016)            FL 819mm
  •         Astro-Physics        160mm f7.5 EDF (2004 - 2007) FL 1200mm
  •         Zeiss APQ             130 f8                (90s)              FL 1040 mm
  •         Zeiss Baader/APQ 150 f8                 (90s)              FL 1200mm

First Light – Astro-Physics 130mm f6.3 GTX

 

First I have a qualification to make concerning this scope. This particular GTX is not optimized for astrophotography. The optics where modified to change the null point to be more in line with visual use. I will not comment beyond this and as to why this is the case, but I did want to make the point up front before going through with a review of the scope. The figure on this particular scope’s optics has proven to be very good.

 

The second point I want to make about the GTX is that it has never been shipped. I drove up to Astro-Physics and picked the scope up myself. So this scope has not been subjected to the stresses of being shipped. It is as it was when it left Roland’s hands. I want to know for sure the the collimation was as perfect as Astro-Physics made it originally.

 


The following is copied word for word out of my observing log:

 

  •     Saturn
    • 21:00 - Saturn was in clouds for first light of the newly refigured AP 130. It was steady and off white. Hard to see moons through the clouds.
  •     Σ 2048 - AB (5.5" sep with mag 6.5 and 9.7)
    • 22:00 - Fantastic. Bright A and very dim B using 6mm Ethos. Both stars were pinpoints. 3.7mm Ethos was too much power, and 8mm not enough.
  •     Σ 1985 - AB (5.9" sep with mag 7.0 and 8.7)
    • 22:33 - "A" noticeably brighter than "B". Both were pinpoints and relatively bright.
  •     β 119 - AB (2.1" mag 8.1 and 8.8)
    • 22:47 - Tight pair. Evenly matched. Perfect with 6mm Ethos. 3.7 Ethos provided a wide separation. Split with 8mm Ethos as 2 pinpoints.
  •     Σ 1962 - AB (12" sep with mag 6.4 and 6.5)
    • 23:11 - Great pair. 8mm Ethos Perfect. Evenly matched pair. Fine binary.
  •     Saturn
    • 23:24 - Saturn rose above the Marriott. Clearly seen Cassini division. Hints of structure on Jupiter. It has the appearance of a sphere with a ring around it. Feels magical to see the sphere. With the contrast, it is full of structure and it feels like I am up close.

AP 130mm f6.3 GTX compared to AP 130mm f6 EDF

 

I thought it would be interesting to compare the 2016 GTX with my 1998 Astro-Physics 130mm StarFire EDF. The question I was trying to answer is what does roughly 18 years of experience and changes in technology buy me. So the first light was done with the two scopes sided by side on my balcony in Washington DC.

 

IMG_0910.JPG

 

The following is copied word for word out of my observing log:

 

  •     Moon
    • 19:30 through 21:30. I started observing an hour before sunset. The EDF and GTX showed equal performance on the somewhat washed out moon. Once it started to get a bit darker, I concentrated on Copernicus. There was no difference between the scopes. In general the scopes were showing the same amount of detail. After sunset and into darkness, I switched to Bullialdus (near the Straight Wall).
    • On the rim adjacent to shadow in the crater, the EDF showed reddish color which spilled into the shadow which diminished its darkness. The GTX showed no color and a crisper black. On the opposite side of the crater, the rim was a thing bright cusp. The EDF showed this as a mushy colored cusp. The GTX showed it as a bright white structure. Overall the GTX showed a more well defined image with crisper detail and no hint of color. At the time, I thought the EDF image was cartoonish with the colors while the GTX was showing fine detail in what appeared to be natural looking shades of grey to black.
    •  Going back to Copernicus, the scopes showed little difference. So depending on the moon structure, the GTX can be clearly superior, or in less contrasty situations, the GTX and EDF are mostly equal.
  •     β Lib
    • 22:15 - This star was used as a target star. The EDF showed this star to be poorly defined and it showed reddish color asymetrically distrubuted to one side of the star. The GTX showed a well defined star with no color at all. So on β Lib, the GTX was clearly superior.
  • β 119 - AB (2.1" mag 8.1 and 8.8)
    •         Split was spectacular in both scopes. Neither scope had an advantage over the other. The best image was with a 6mm Ethos.
  • Σ 2048 - AB (5.5" sep with mag 6.5 and 9.7)
    • 23:10 - This was a tough split due to the 3.2 magnitude difference. The primary is easily seen, but the secondary is almost mag 10 which makes it challenging in DC lights. The secondary required averted vision mostly. The GTX and EDF perfomed equally well, no advantage with either.

 



#2 daveCollins

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Posted 25 June 2016 - 03:43 PM

AP/APQ: Day 1 (APQ 130, GTX 130, AP 160)

 

 

It is a 2 ½ hour drive from DC to an observing spot. Traffic was only a pain for the first 30 minutes. Once past the beltway, things were fine. I am looking forward to the beautiful new highway 55 in WV which runs along to top of ridges. I note that conditions seem to be great along the way. I stopped to meet up with Roy outside of DC and we both drove out to John’s place. John showed up a little later. The skies started getting slightly overcast, but that was muted by the smells and sights of being in the mountains.

 

One of my hobbies is collecting watches. Here is the watch I used for this trip. It is a 1950 and is in original condition:

 

IMG_0929_Rolex.JPG

 

I have wanted to do a scope comparison for a while. It’s one this to speculate as to the advantage of once scope over another, but an entirely different experience to choose a scope based on a comparison of it with other scopes, both larger and smaller. The other factor for me is that I’ve heard over the years about the fine optics of the APQs and so I was curious to see how the scopes compare with scopes I own. It may seem that this would lead to a “my scope is better than yours” type of comparison, but that couldn’t be further from the truth for me. I could care less whose scope performs the best. I love the scopes that I have … period. Doesn’t matter how they compare in terms of satisfaction.

 

My intent isn’t to explore the performance potential of the scopes in this review. I wouldn’t know how to go about doing that and I don’t consider myself qualified to undertake such a task. What I can do, and what we did, was to compare a set of scopes side by side in conditions that we typically find ourselves observing in. It was much harder to do than I thought it would be when I was in the planning stages. I stuck to my plan and focused on the task at hand and kept at it until I accomplished what I set out to do.

 

 

Here were are just before sunset and excited about the first night:

 

 

YN0R7886_allScopes.jpg


We started out with Jupiter. Jupiter was not behind a veil of clouds, but still remained in clear sky. The seeing was stable.

(Everything is presented as it happened. The sequence of the comments is significant)

 

  •     Jupiter
    • Roy
      • AP160 – Banding evident (8mm E)
      • GTX – Very similar image. No difference in brightness, or sharpness. Same detail.
      • APQ130 - Same detail as in the other two scopes. Slightly sharper image.
    • Dave
      • APQ130 – Nice sharp image
      • GTX – More detail than APQ, but same sharpness.
      • AP160 – More detail than the GTX, but not as sharp.
    • Overall Impressions
      • Jupiter was not affected by the veil of clouds overhead. It was in a hole. In my opinion, the seeing was decent and at least as good as average conditions for our area.
      • Roy
        • Overall the GTX appeared to have a sharper image.
      • Dave
        • I agree with Roy about the sharpness of the GTX, but the difference between it and the other two is subtle and not particularly significant.

 

YN0R7889_apGTX.jpg
 



#3 daveCollins

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Posted 25 June 2016 - 03:54 PM

After a short break, we spent one more cycle between the GTX and AP 160 on Jupiter:

  • Jupiter
    • Dave
      • Same general image quality, but the AP 160 is showing slightly more detail. This detail includes the shading between the main bands and polar areas.
      • After another cycle between both scopes, Dave felt the detail was the same.
    • Roy
      • Cannot distinguish any difference between the two scopes.

 

YN0R7893_AP160.jpg

 

 

  • Mars
    • There was a shading of the surface of Mars across the planet. The most distinctive feature was a blackish area on the planet, nearer one of the poles. So it was particularly hard to judge the two scopes. It is also notable that Mars was behind a thin veil of clouds and these clouds were illuminated by moon light. This contrasts with the conditions on Jupiter in that Jupiter wasn’t affected by clouds.
    • Roy
      • The APQ was slightly sharper than the GTX.
    • Dave
      • The GTX and APQ130 showed no differences in sharpness or detail.
      • AP160 – Showed more detail than either the GTX or APQ.

 

YN0R7896_APQ130.jpg

 

  • Saturn
    • The planet was also veiled by clouds and was particularly close to the moon. Those clouds were scattering moon light and so the region around Saturn was brighter than in the case of Mars.
    • In all scopes the Cassini division was clearly visible as a relatively sharp detail on the rings. The planet itself showed shading variations which were subtle.
    • Roy
      • There was no perceptual difference between the APQ 130 and the GTX.
    • Dave
      • There was no perceptual difference between the APQ 130 and the GTX.
      • AP160 – Presented a superior image. There was more detail visible on the planet than any of the 130 scopes was showing.

Clean GTX objective:

 

 

YN0R7911_GTX_Obj.jpg

 



#4 daveCollins

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Posted 25 June 2016 - 04:00 PM

AP/APQ: Day 2 (APQ 160, GTX 130, AP 160)

 

The second day was quite a bit better than Day 1. The seeing was also better and at times was good enough to see an almost steady diffraction ring around stars. Earlier in the evening the seeing fluctuated between bad and average. This condition improved as the night went on. The night was clear of any clouds. The moon was mostly full and beautifully bright. With a slight breeze and temperatures in the 70s, it was a fantastic evening. John and I were fully enjoying the evening and we both agreed that even if we didn’t have scopes, it would be a great evening under a full moon with planets clearly visible. The moon was casting sharp shadows.

 

As I waited for sunset, it was nice to relax an just enjoy being outside. This is one of the aspects of this hobby that I appreciate. It gets me out into beautiful areas and gives me a chance to catch up with myself:

 

YN0R7926AfterNoon.jpg

 

Roy was not present for this day and Dave made all observations recorded below.

 

I wanted to experiment with a lens of mine. Its a canon 85mm f1.2 which is tricky to use. I set everything up and had Roy take my picture. You might not be able to tell from the photo, but I was having a great time:

 

 

YN0R7919Dave.jpg

 

It was a tough night/morning of attempted sleep. I think I got 5 hours total. Since I started out yesterday a bit short on sleep, I'll have to count on excitement to keep me going for another day of observing. As it turns out, I was able to nap for an hour before sunset.

 

Anyway, here are the scopes from last night safely tucked away. They'll be getting up shortly for the today's observing.

 

 

YN0R7923Morning.jpg



#5 daveCollins

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Posted 25 June 2016 - 04:10 PM

Obviously, we (John) need to get the APQ 150 setup for observing. Here is John finishing up:

 

YN0R7935John.jpg

 

And now everything is set for day two.

 

YN0R7938_JohnDave.jpg

 

By the way, even though John was observing on and off throughout the night, he was focused on his imaging. For this reason, I just plowed ahead with the rest of the review:

 

  • Jupiter
    • GTX - The red spot was situated close to the center of the planet at the start of observations. Two bands were visible with some detail towards the poles.
    • APQ 150 – Very close to the GTX. The APQ was showing a slightly sharper image.
    • AP 160 – Softer image than the APQ. Both the GTX and APQ showed a sharper image than this scope.
    • After another 30 minutes of cycling between the scopes, all three scopes were close in detail and sharpness. If I were to rank the scopes it would be first APQ 150 (barely ahead of GTX), GTX (slightly ahead of AP160), AP 160 (last by a very small degree)
  • Mars
    • GTX – Surface detail was sharp and compared closely with that visible using the AP 160. The AP 160 was showing slightly more detail.
    • 30 minutes more of observing using all three scopes were showing a very clear dark region and whitish (subtle) towards one of the polar areas (opposite the dark region).
      • There was no difference between the three scopes.
  • Saturn
    • The APQ 150 showed a brighter image than the GTX.
    • Both the APQ and GTX showed faint banding on Saturn, a sharp ring structure and the Cassini division was visible all the way around the ring.
    • Comparing the GTX and AP 160, the AP 160 image was brighter, but even with the dimmer image, the GTX showed more detail.
      • I spent a long time on Saturn. I cycled between all scopes trying to eke out differences between them. I would spend 5 to 10 minutes on a specific scope and then quickly compare what I was just looking at with the new image. I would continue with the new scope waiting for the clearest moments.
    •     I had all three scopes at 200x. I walked from scope to scope and all three were showing the same details. The APQ 150 and AP 160 were presenting brighter images and easier to see detail, but the GTX was giving a more subjectively pleasing image than the two larger scopes. This was especially true on the planet itself.

 

 

A note I want to make that wasn’t captured during the note taking was that all scopes showed color free images ... completely color free. The moon was virtually full and I used it as a target in order to evaluate the color correction and the APQ 150, AP 160, and GTX were flawlessly color free.

 

I fought with the wind over the past few years when attempting to make coffee. I knew what I needed to do, but never got around to it. Finally I fashioned this simple kitchen and now have not problems making food and brewing coffee.

 

YN0R7929Coffee.jpg



#6 Erik Bakker

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Posted 25 June 2016 - 04:10 PM

Excellent stuff Dave, look forward to the next episode. Beautiful scopes and wonderful kitchen!



#7 daveCollins

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Posted 25 June 2016 - 04:21 PM

It is now 12:30 am and I am done with the planets and the moon. I wanted to evaluate the GTX as compared to the AP 160 on double stars. I did not include the APQ 150 in this observing. Also note that observing stopped abruptly at roughly 2 am due to a battery’s voltage dropping to 11 volts. At that point the Mach1 can be slewed, but will not respond to goto commands. I was tired and called it a night.

 

  • Alberio
    •     GTX – beautiful yellow blue pair. The stars were well defined and showed a first diffraction ring.
    •     AP 160 – The stars were not as well defined as with the GTX. The diffraction rings were not nearly as evident.
  • Delta cyg (mag 2.9 and 6.3 with a 2.7” separation)
    •     The GTX had a tough time with the split using a 3.7mm Ethos. Part of the difficulty was that the first diffraction ring was falling on B.
    •     AP 160 – The split was easy. There was a big difference between the scopes.
      • This may sound a bit contradictory base on my other comments. The A star was not as well defined on this scope as with the GTX, but the B star was easy to see beyond the somewhat poorly imaged A, but the AP 160 wasn’t showing the clear diffraction rings that were evident with the GTX.
  • Σ 2609 (HD 189432) Mag 6.7 and 7.6 with a separation of 2.0 seconds
    •  The GTX showed a clear split.
    •  
    •  The AP 160 was much easier. Again a clear difference between the scopes.
    •  Both scopes showed well defined pinpoints of light.
      •  I used the 3.7mm ethos on each scope (GTX 221x and AP 160 using 324x).

 

At this point the Mach1 stopped function with respect to goto even though it would slew. I thought I had done something wrong and after a fair amount of trouble shooting, I discovered that the issue was low voltage. It was now 3am and I just called it a night.

 

YN0R7942AP150.jpg

 

 

  • Summary
    • All scopes showed flawless color correction. There was no difference between the four.
    • In the finest moments of clarity, all three scopes showed comparable sharpness. It’s hard to say anything other than comparable since you can’t hold the see conditions to perfect and the walk around and do an objective comparison. But subjectively, the figure on the optics of these scopes must be very close in quality.
    • The 130s showed the same detail on the planets, although somewhat dimmer than the larger scopes.
      • This was one of the surprises for me. The difference in planetary detail is small to nonexistent between the 130s and the 150/160 scopes.
    • The smaller GTX 130 was at a clear disadvantage to the larger AP 160 in splitting doubles, although the star images were superior in the smaller GTX on brighter stars.
      • Dimmer stars were resolved as pinpoints on both scopes.
    • In my subjective and biased opinion, the GTX had one of the finest figured and designed set of optics I’ve used. There were times in the comparison were I felt it was simply the superior scope. The GTX can be used in the same capacity as the larger 150/160 class scopes without missing anything. Its image may be a bit dimmer, but the quality of that dimmer image surpasses the brighter images in some cases.
    • I do not claim to have made any observations concerning the performance potential of any scope. That wasn’t the point of the exercise. Would the APQs show superior performance as compared to the Astro-Physics scopes? Maybe, maybe not. I don’t think anyone can make that call without perfect conditions and all scopes on hand at the same time. Since 2012, I’ve only had one night were I would describe the conditions as perfect.
    • From this point of view, who cares what the performance potential is. Isn’t it the actual performance in conditions that we observe that is important?

I want to end this with a thanks to Roy for putting fun aside and doing the work needed to perform a comparison. And many thanks to John for the effort he made to support this comparison and supply the APQ scopes.



#8 daveCollins

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Posted 25 June 2016 - 04:24 PM

Finally, a couple of fun shots to close out this mega post:

APQ 150 at sunset:

 

YN0R7944_APQ150.jpg

 

 

GTX under a full moon:

 

YN0R7947_GTX.jpg

 

Packed and going home.

 

IMG_0932_goingHome.JPG



#9 donadani

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Posted 25 June 2016 - 04:41 PM

Great scopes! great review - thanks!

 

I´m a bit suprised the difference between 5" and 6" seemed to be so small...

 

cs

Chris



#10 Astrojensen

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Posted 25 June 2016 - 04:53 PM

A great and fascinating report! There's one thing that bugs me, however:

 

 

 

Delta cyg (mag 2.9 and 6.3 with a 2.7” separation)
    The GTX had a tough time with the split using a 3.7mm Ethos. Part of the difficulty was that the first diffraction ring was falling on B.

This worries me a lot. Why is the first diffraction ring bright enough to hide the companion? In a first-rate scope, it shouldn't be. In my 5" f/14 achromat (before I mothballed it due to portability issues) Delta Cygni was effortlessly resolved and the companion immediately obvious and well away from the first ring. And in the 100mm f/8 TMB apo I have on loan, the first diffraction ring is extremely dim and very delicate and the companion much brighter than it, again making it very easy to see. 

 

I wonder why there's such a large descripancy between our views? 

 

 

Clear skies!

Thomas, Denmark



#11 Kent10

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Posted 25 June 2016 - 05:01 PM

Thanks for the review.  I enjoyed reading every word and seeing the pictures.  Beautiful scopes.  I bet if the seeing was better then the difference between the 130 and 160 would be more evident.  I often compare my NP-101, TV-140, Tec 180FL and Starmaster 16.5".  The Tec is almost always best on the planets and the moon but when the seeing is marginal then at slightly lower power the 140 can look as good or better than the 180.  The 16.5" of my SM has only twice in almost a year been better than the Tec.  Seeing was great and I saw the Alpine Valley Rille in both scopes but it was very obvious and I could use higher power in the Dob.  The other time was with Jupiter.  The Dob had more color and the detail was more obvious but still seen in the Tec.  If only we could have more nights with great seeing!   

 

Thanks again.  I wish I could have been there. 

 

PS.  My wife saw your scope set up as I was reading and said it looks like my setup :).  No, I said, those are Zeiss and AP!  She asked if I was going to get a Zeiss. . .  She knows about AP from my many stories.  I told her I was happy with my Tec and Televue but she did in a sense open the door for me :lol:

Attached Thumbnails

  • P6179814 (Medium).jpg

Edited by Kent10, 25 June 2016 - 07:17 PM.


#12 Scott99

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Posted 25 June 2016 - 05:07 PM

nice report!!!  I didnt know DC was only a couple hours from the mountains, thought it was farther.   Not different from Boston in that regard.  What a great spot!  (I see I'm not the only one plagued by cirrus clouds while observing)

 

My reaction to this is that I like the streamlined design of the Zeiss.   no rings, no focuser knobs, slim dewshield.  All the APs and TEC and Taks of today are made to faciliate imaging, with big huge focusers.  

 

Also I like using less glass ep's on this type of observing - planets and double stars.  You guys should try some good orthos or even a Tak LE 5mm.  I see a contrast improvement over 6 and 7 element ep's with these, I'm sure the improvement's even larger with 8 or 9 elements.    just a thought.  I use widefields too.



#13 Kent10

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Posted 25 June 2016 - 05:07 PM

A great and fascinating report! There's one thing that bugs me, however:

 

 

 

Delta cyg (mag 2.9 and 6.3 with a 2.7” separation)
    The GTX had a tough time with the split using a 3.7mm Ethos. Part of the difficulty was that the first diffraction ring was falling on B.

This worries me a lot. Why is the first diffraction ring bright enough to hide the companion? In a first-rate scope, it shouldn't be. In my 5" f/14 achromat (before I mothballed it due to portability issues) Delta Cygni was effortlessly resolved and the companion immediately obvious and well away from the first ring. And in the 100mm f/8 TMB apo I have on loan, the first diffraction ring is extremely dim and very delicate and the companion much brighter than it, again making it very easy to see. 

 

I wonder why there's such a large descripancy between our views? 

 

 

Clear skies!

Thomas, Denmark

Are diffraction rings brighter in smaller scopes or are they just easier to see because the seeing affects them less?  I see the rings more often and more obviously in my NP-101 than in my Tec 180FL, for example.  Maybe it has to do with the power used too.



#14 Scott99

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Posted 25 June 2016 - 05:09 PM

haha Kent I hear you on the Zeiss.  All I can say is, good thing there's no APQ 160.  that should be enough to deter me from trying one   :lol:



#15 Astrojensen

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Posted 25 June 2016 - 05:13 PM

 

A great and fascinating report! There's one thing that bugs me, however:

 

 

 

Delta cyg (mag 2.9 and 6.3 with a 2.7” separation)
    The GTX had a tough time with the split using a 3.7mm Ethos. Part of the difficulty was that the first diffraction ring was falling on B.

This worries me a lot. Why is the first diffraction ring bright enough to hide the companion? In a first-rate scope, it shouldn't be. In my 5" f/14 achromat (before I mothballed it due to portability issues) Delta Cygni was effortlessly resolved and the companion immediately obvious and well away from the first ring. And in the 100mm f/8 TMB apo I have on loan, the first diffraction ring is extremely dim and very delicate and the companion much brighter than it, again making it very easy to see. 

 

I wonder why there's such a large descripancy between our views? 

 

 

Clear skies!

Thomas, Denmark

Are diffraction rings brighter in smaller scopes or are they just easier to see because the seeing affects them less?  I see the rings more often and more obviously in my NP-101 than in my Tec 180FL, for example.  Maybe it has to do with the power used too.

 

It can be a mix between different factors. Small apertures help, because the seeing is getting better at smaller apertures and the optical quality is also likely better, but on the other hand, stars are getting dimmer, so fewer stars will show diffraction rings. 

 

 

Clear skies!
Thomas, Denmark



#16 Astrojensen

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Posted 25 June 2016 - 05:14 PM

haha Kent I hear you on the Zeiss.  All I can say is, good thing there's no APQ 160.  that should be enough to deter me from trying one   :lol:

There's an APQ 200 out there, if you can find it...  ;)

 

 

Clear skies!
Thomas, Denmark



#17 Kent10

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Posted 25 June 2016 - 05:17 PM

 

haha Kent I hear you on the Zeiss.  All I can say is, good thing there's no APQ 160.  that should be enough to deter me from trying one   :lol:

There's an APQ 200 out there, if you can find it...  ;)

 

 

Clear skies!
Thomas, Denmark

 

Oh no.  That would be perfect and then someone will have to do a comparison with it and the Tec 200 F9 and Tec 200FL (I think there are 2 focal lengths, also) and then I believe there are AP 200s or 206 or something like that too.  What fun that would be.



#18 Astrojensen

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Posted 25 June 2016 - 05:17 PM

BTW, I just ran a simulation in Aberrator and the companion star in a 2.7" double is well outside the first diffraction ring in a 130mm scope. The ring *just* touches the side of the companion's spurious disk in a 100mm scope.

 

 

Clear skies!
Thomas, Denmark



#19 HARRISON SCOPES

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Posted 25 June 2016 - 05:34 PM

Superb stuff...APQ is legendary, to fuel the 8" debate I have used extensively TEC200FL #1 compared to my then excellent TMB203 F9 and the TEC was better, more detail, more contrast...dare I say the Fluorite advantage was apparent...

#20 Astrojensen

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Posted 25 June 2016 - 05:38 PM

Uh, the f-word has appeared, now the debate is on!  :grin:

 

 

Clear skies!

Thomas, Denmark



#21 Kent10

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Posted 25 June 2016 - 05:41 PM

Superb stuff...APQ is legendary, to fuel the 8" debate I have used extensively TEC200FL #1 compared to my then excellent TMB203 F9 and the TEC was better, more detail, more contrast...dare I say the Fluorite advantage was apparent...

My Tec 180FL is also #1.  It somehow feels special. 



#22 HARRISON SCOPES

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Posted 25 June 2016 - 05:45 PM

I collected TEC200FL #1 with the owner from BC&F London where we worked when it arrived from yuri...it was a very special refractor moment opening it with the very excited owner wh5will never let her go and uses her...yes her she's named phoebe literally every opportunity even all these years later. An extraordinary instrument.

#23 junomike

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Posted 25 June 2016 - 05:49 PM

Excellent Review Dave.  It gives some insight into astro-gear some of us may never be able to acquire, but at least we can live vicariously through reviews like yours!

 

Mike



#24 junomike

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Posted 25 June 2016 - 05:51 PM

Dave, I know you already commented as far as you're willing to in regards to the AP 130 GTX  being tweaked for visual. I'm hoping someone will be able to comment further on whether this might soon be an option for those who's "number" comes up (at AP).

 

Mike



#25 Rutilus

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Posted 25 June 2016 - 06:16 PM

A great and fascinating report! There's one thing that bugs me, however:

 

 

 

Delta cyg (mag 2.9 and 6.3 with a 2.7” separation)
    The GTX had a tough time with the split using a 3.7mm Ethos. Part of the difficulty was that the first diffraction ring was falling on B.

This worries me a lot. Why is the first diffraction ring bright enough to hide the companion? In a first-rate scope, it shouldn't be. In my 5" f/14 achromat (before I mothballed it due to portability issues) Delta Cygni was effortlessly resolved and the companion immediately obvious and well away from the first ring. And in the 100mm f/8 TMB apo I have on loan, the first diffraction ring is extremely dim and very delicate and the companion much brighter than it, again making it very easy to see. 

 

I wonder why there's such a large descripancy between our views? 

 

 

Clear skies!

Thomas, Denmark

In a 80mm scope, the companion of delta Cyg sits bang in middle of the first diffraction ring.  With a 100mm scope, I describe it

as kissing the outside edge of the first diffraction ring. With a 130mm scope, it is well away from the diffraction ring.  




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