Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Starwave 102ED f11 (yes, ED)

  • Please log in to reply
798 replies to this topic

#776 Max Lattanzi

Max Lattanzi

    Viking 1

  • *****
  • Posts: 932
  • Joined: 27 Jun 2007

Posted 22 March 2021 - 02:47 PM

At their website Teleskop Service says that it is comparable to a 4"ED F8 with FPL53. I actually expect it to have a little bit more contrast than an ED100 with FPL53 at F9.

That is pure marketing.

Without knowing the mating elements of both, it is impossible to make comparisons.

 

If you use a glass that is a good mating for the FPL53, and blindly couple it to the FPL51, yes, by increasing the focal length to about 50% you can roughly have the same color correction (but, as always, better overall correction of the other aberrations in the longer f/ratio instrument). 

 

But optical design is not done like that. By choosing a good or bad mating element, the correction can vary from simple to double.

 

There are better mating glasses to FPL51 than the vanilla one used for the FPL53 (read BK7 -- which, btw, is just the cheapest, not the best). 

Then, if the producer does not want to use them, because customers are overhappy by simply reading "FPL53" or "FPL51" written on the front ring, well, that's another story.

 

Again: marketing, not optics (and actual performances, which go hand in hand with the latter, not the former).

 

Cheers,

-- Max


  • Astrojensen and Bomber Bob like this

#777 russell23

russell23

    Voyager 1

  • *****
  • Posts: 11,789
  • Joined: 31 May 2009
  • Loc: Upstate NY

Posted 22 March 2021 - 03:54 PM

Max,

 

That makes sense.  I care about the optical performance more than the glass.  My 102mm f/11 with the fpl51 seemed to have better color correction than my Stellarvue 102 Access with fpl53.  

 

But that said, the general pattern is that fpl51 objectives show more CA than fpl53 objectives.  That is why the people on this forum talk about the glass. The Starwave 102 f/11 seems to be the exception.  

 

If you ask someone whether the objective uses fpl51 or fpl53 you pretty much can determine from that what the color correction will look like after factoring in the f/ratio with the scopes that are actually on the market.

 

Dave


  • Tyson M and Ben the Ignorant like this

#778 Max Lattanzi

Max Lattanzi

    Viking 1

  • *****
  • Posts: 932
  • Joined: 27 Jun 2007

Posted 22 March 2021 - 06:55 PM

Dave,

 

Actually I do care about performances, and only about them -- those are given (also) by the glass. But not a fancy-labelled one, rather the combination of all of the elements composing the objective lens.

 

If your 102 f/11 FPL51-flavoured gives better chroma correction that your Stellarvue 102 Access FPL53-empowered, that simply means that the designer of the former did a better work than the one of the latter; and the lens executor(s) did a better job in figuring it. FPL51 vs FPL53 being just a part of the equation.

 

All things being equal -- same mating element, same f/ratio, same spherical, same mechanics -- FPL51 objectives do show more CA than their FPL53 counterparts. But "all things" are never "equal".

 

People  on this forum and elsewhere seem to like cheap shortcuts to self-pride of ownership, calling it "knowledge". But, if you carefully select the mating element, if you use a slightly longer f/ratio, if you are more careful with the spherical (longer f/ratio helps in that AND in better spherochromatism as well), and you have a better mechanics (which is also helped, again, by the slightly longer f/ratio), it is no surprise that your slightly longer FPL51-flavoured telescope has better performances that its shorter FPL53-blessed sibling.

 

And, no, the Starwave 102 f/11 is not at all an exception; it is simply a relatively widespread instrument which uses just some of the above-mentioned design elements. That's why more people experience the phenomenon and therefore talk about it.

 

But I can tell you that, just to pick up but a few, the well-mated TMB-designed 110 f/7 WO-branded FPL51-flavoured triplet has the same correction (if not better) than the AP Traveler FPL53-based triplet (not at all bashing AP -- I own them; just being realistic). Yes, of course the Traveler is f/5.8 and much more portable as it is (although the WO can be split into 3 parts, while the Traveler only in 2). Further, the very same can be said of the old AT 111 f/7. And shall we talk about the WO 110 f/6.5 oiled version made by TEC...?!  And, to remain in TEC domain -- not because TEC is magic, but because Yuri did his homework and carries out some clever mating -- I can tell you that the FPL51-doomed TEC200ED f/9 has a better color correction of both my C11 and C14 that, at high magnification, show the spurious colour (and spherochromatism) coming from their Schmidt plate. And, had Yuri done a f/10 version of this ED, this would have been pure white at the CCD at 486nm, even better than his f/8 CaF2 (Fluorite) sibling.

 

So, no magic: optics (or, better, opto-mechanics). And clever execution of it.

 

Cheers,
-- Max

 

PS/ All this being said, for an astro-photographer the spherical has very little importance, while the chroma correction WITH as fast as possible focal ratio has. Therefore, today astrophotography-driven market does heavily favour -- and therefore put a heavy pride-of-ownership value on -- the short-focus FPL53-blessed instruments, and rightly so for that purpose.  But if you are instead into, say, visual planetary, your FPL51-plagued telescope, with a slightly longer f/ratio (between 25 and 50%, depending on whether the designer was heavenly inspired or just a mere stray dog) will serve you and your eyepieces much better.


Edited by Max Lattanzi, 22 March 2021 - 06:55 PM.

  • siriusandthepup, Alterf, Astrojensen and 5 others like this

#779 SteveG

SteveG

    Cosmos

  • *****
  • Posts: 9,885
  • Joined: 27 Sep 2006
  • Loc: Seattle, WA

Posted 22 March 2021 - 11:36 PM

I'm still waiting for a direct, side-by-side comparison with a 100 f9 ED (using FPL-53). My guess is the longer focal length scope will have slightly better sharpness, but the f9 FPL-53 scope will have slightly better color correction. Just a wild guess though.

 

I'm still thinking about getting one one these just for fun.



#780 Jacques

Jacques

    Viking 1

  • -----
  • Posts: 584
  • Joined: 11 Aug 2002
  • Loc: Belgium

Posted 23 March 2021 - 03:29 AM

This would be my guess too.In de ED100 thread the emphasis lies on excellent color correction, in this tread the emphasis lies on exceptional contrast. Also toying with the idea of getting one btw. 


Edited by Jacques, 23 March 2021 - 03:54 AM.


#781 russell23

russell23

    Voyager 1

  • *****
  • Posts: 11,789
  • Joined: 31 May 2009
  • Loc: Upstate NY

Posted 23 March 2021 - 08:10 AM

Max,

 

Great explanation!  Love it.  I think it is extremely important for everyone to remember that there is more to it than fpl-51 vs. fpl-53 in terms of what is possible.  

 

I think we are talking about two different levels of scope here.  When I say the fpl-51 scopes show more color than the fpl-53 scopes, I’m talking about the typical scopes costing less than $3000 - not premium APO’s like TEC, Astrophysics, Takahashi, etc. 

 

If you look at those “budget APO’s”. It is pretty consistent that fpl-51 doublets show visible CA and are best characterized as “semi-APO’s” whereas most fpl-53 doublets show no visible CA unless you are highly sensitive to seeing it and are therefore “visual APO’s”.  

 

Specifically I think of the AT80ED and AT102ED with fp-51 or FK-61 and the Williams optics Megrez 110, the early Lunt 80mm and 102mm f/7 scopes etc.  All of those scopes show visible CA whereas the fpl-53 doublets do not typically - or you really have to hunt for it. 

 

If you are going to cheap out on the mating element or go fast on the focal ratio then the ED element does make a difference.  The fact that you can cheap out on the mating element and still get a visual image free of easily detectable CA in scopes < f/8 with fpl-53 glass whereas you cannot with fpl-51 glass does explain why people have this perception that fpl-53 is better than fpl-51.   In the short f/ratio, cheap mating element circumstance the fpl-53 produces noticeably better results.

 

My Starwave 102 f/11 with fpl-51 shows what happens if you slow down the f/ratio and possibly improve the mating element. I have no idea if the mating element is better than in other doublets or not but the results are excellent.

 

All I’m saying is that market reality and optical potential are not the same thing. 

 

Dave


Edited by russell23, 23 March 2021 - 08:11 AM.

  • Astrojensen, Don Taylor, Bomber Bob and 3 others like this

#782 Max Lattanzi

Max Lattanzi

    Viking 1

  • *****
  • Posts: 932
  • Joined: 27 Jun 2007

Posted 24 March 2021 - 10:54 AM

Dave,

 

No matter what you pay -- 500, 5.000, 50.000 $ -- the song remains the same: with the same mating element AND the same f/ratio AND the same wavefront correction AND the same glass quality (this less evident to check and get), the FPL53 instrument will always have an advantage in correcting chromatic aberration. Otherwise it would mean that the FPL53 glass is of inferior quality than the nearby FPL51 (it can happen though) and/or the spherical is also visibly worst.   But, what I tried to say, is that it is enough to change one or more of the above elements, and the advantage is gone.

 

Therefore, no matter the wrong perception of people, it is ridiculous to dismiss an instrument for the sole reason that utilises FPL51 glass without knowing anything else about it.

 

Once more, if you work well, you can indeed build a better FPL51-based instrument than its FPL53-flavoured more expensive counterpart. No matter the price tag. And, as you've notice, the 102ED f/11 is one of the few instruments that has been adopting some of the insights above. Which is good, at last. 

 

But, if you want my honest opinion, it's a pity that the marketing department was a bit shy on the final correction: a better choice of the mating element (or a slightly longer f/ratio, say f/13) would have provided the end user with even better quality than the 110 first-class FPL51 triplets mentioned above (which all have a substantial better correction that the one reported here https://www.cloudyni...s-ed/?p=9269983), still at a fraction of the cost. And, I guess anyone would have happily paid one or two hundred dollars more to have a perfectly corrected instrument -- which could have been possible, still remaining under the bar of the 900$, and far from the price of either a FPL53 f/9 doublet or a FPL51 f/7 triplet.

 

Alas, we live in a world of compromises where marketing has more influence than substance in the final assessments. C'est la vie.

 

Cheers,
-- Max


  • russell23, Tyson M and Jethro7 like this

#783 obsale

obsale

    Lift Off

  • -----
  • Posts: 7
  • Joined: 28 Mar 2021

Posted 28 March 2021 - 11:23 PM

First of all, mention that I am new here, I apologize for my bad translation into English. I've been following this thread for a long time, and I want to add my humble experience on the f11 ed.

 

I am an astrophotographer and have tried all kinds of telescopes. refractors, newton. mak, sc. etc. and I wanted to experiment with a long focus ed with a large sensor to observe not only color correction but other typical refractor distortions. I have been tremendously surprised since I have never had a telescope so sharp and perfect in images. I know people take photos at f5, f6 and max f7 but high resolution astrophotography is not taken there. when you take at f11 onwards you can see the true quality of an instrument vs sensor.

 

I have never felt a better 35mm lens than this ota. I am really very surprised what a simple and cheap instrument can do in good hands ...

 

I would like to share high resolution images but I do not know how to upload them in this medium, if someone can help me, I would appreciate it very much ...


  • daquad, Astrojensen, Don Taylor and 4 others like this

#784 obsale

obsale

    Lift Off

  • -----
  • Posts: 7
  • Joined: 28 Mar 2021

Posted 29 March 2021 - 06:17 AM

omega centauro

 

 


  • daquad, Astrojensen, eros312 and 9 others like this

#785 obsale

obsale

    Lift Off

  • -----
  • Posts: 7
  • Joined: 28 Mar 2021

Posted 29 March 2021 - 06:28 AM

this image was taken with a full frame dsrl, 22 shots of 3 minutes iso 640. a bit of pixinsight and ps. Generally my images are several hours long.

 

but what I wanted to highlight is the quality of the lens in deep sky astrophotography. None of my otas that I have had has this image quality. the contrast is very high, the AC is very, very controlled, the image is slightly cropped to appreciate the stars more closely, at f11 it is able to take a situation with 35mm that is almost impossible with many short focal lengths.

 

the image scale in that format is incredible, you can take thousands of objects without that pressure of framing. Anyway, just judge what I tell you.


  • Astrojensen, russell23, Don Taylor and 3 others like this

#786 Jethro7

Jethro7

    Surveyor 1

  • *****
  • Posts: 1,853
  • Joined: 17 Dec 2018
  • Loc: N.W. Florida

Posted 29 March 2021 - 11:26 AM

First of all, mention that I am new here, I apologize for my bad translation into English. I've been following this thread for a long time, and I want to add my humble experience on the f11 ed.

 

Hello obsale and everyone,

Some how, I should be surprised by your findings with the F/11 but this scope has surprised me so often now that I am anticipating that the outcome performance will exceed my expectations. From clarity of resolution at insane magnifications to Night Vision Astronomy ( in general the preferred scopes are the ultrafast Astrographs below F/3 For NVA)  at least for the Altair Starwave 102ED F/11 Kunming United Optics, got everything right in the design and execution and produced one heck of a amazing and inexpensive scope. I did not even consider the glass used in the lenses of this scope whether it be FPL 51 or FPL 53 or whatever when I desided to buy one. What was the determining factor were the simple words written in the threads here on CN on Topic threads just like this one, that made the decision for me. There are a number of contributors here on CN, that over the years I know that their words are true and opinions are more than likely correct and I have learned to take them with special consideration. Only in my beginnings with this hobby was I ever swayed by the manufacturers  clever advertisements touting this and that and in hindsight have caused me to make some poor decisions in equipment.  I am still thinking that I need a second Altair F/11"and make a Super binoscope and that idea has never left my table. Two Altair F/11's will be twice as good. 

 

THANK YOU EVERYONE  For keeping me financially broke but Happy, forever LOOKING UP Jethro


  • russell23 likes this

#787 obsale

obsale

    Lift Off

  • -----
  • Posts: 7
  • Joined: 28 Mar 2021

Posted 29 March 2021 - 01:52 PM

When I started taking deep sky images, obviously I was guided by the general opinion in astronomy forums that images should be taken with fast lenses etc. etc. etc. problems with the stars and the sky background. I did not understand why manufacturers only offer very fast lenses and telescopes for all purposes.

 

Over the years I developed photo skills and discovered how marketing literally misleads the consumer to achieve its purpose. Obviously they have flooded the market with increasingly expensive equipment (fast) with the story that a photo is taken faster etc, etc.

 

Let me tell you that for 600 dollars more or less I have the best deep sky lens that my cameras can take ! I think they were wrong with this refractor, as it is a complete marketing mistake! This telescope is in direct competition with multi-thousand dollar instruments! I myself have taken pictures with all kinds of instruments and when I looked at my own results I just couldn't believe it. I have compared images with this modest, inexpensive, and inconspicuous instrument with otas of great historical renown and I just don't understand how people can afford NOT TO TRY IT.

 

my humble opinion is a complete marketing error and is a serious threat to the sales of expensive instruments ... obviously this opinion is in astrophography, with I have the limited visual experience to reaffirm this. but let me ask something ?, who would dare buy a refractor f 11 with ed glass, the cheapest in the world to take serious photos ?? let me answer; I only know a crazy person: I


Edited by obsale, 29 March 2021 - 01:54 PM.

  • Jethro7 likes this

#788 ris242

ris242

    Ranger 4

  • -----
  • Posts: 350
  • Joined: 01 Feb 2017
  • Loc: Wellington, New Zealand

Posted 29 March 2021 - 02:07 PM

When I started taking deep sky images, obviously I was guided by the general opinion in astronomy forums that images should be taken with fast lenses etc. etc. etc. problems with the stars and the sky background. I did not understand why manufacturers only offer very fast lenses and telescopes for all purposes.

 

Over the years I developed photo skills and discovered how marketing literally misleads the consumer to achieve its purpose. Obviously they have flooded the market with increasingly expensive equipment (fast) with the story that a photo is taken faster etc, etc.

 

Let me tell you that for 600 dollars more or less I have the best deep sky lens that my cameras can take ! I think they were wrong with this refractor, as it is a complete marketing mistake! This telescope is in direct competition with multi-thousand dollar instruments! I myself have taken pictures with all kinds of instruments and when I looked at my own results I just couldn't believe it. I have compared images with this modest, inexpensive, and inconspicuous instrument with otas of great historical renown and I just don't understand how people can afford NOT TO TRY IT.

 

my humble opinion is a complete marketing error and is a serious threat to the sales of expensive instruments ... obviously this opinion is in astrophography, with I have the limited visual experience to reaffirm this. but let me ask something ?, who would dare buy a refractor f 11 with ed glass, the cheapest in the world to take serious photos ?? let me answer; I only know a crazy person: I

It's not a problem - taking photos of stars - as they are bright to start with. Its a little different taking photos of nebula that are dim, and in some cases just brighter than the background.



#789 Don Taylor

Don Taylor

    Apollo

  • *****
  • Posts: 1,366
  • Joined: 12 Jul 2009
  • Loc: Broken Arrow (Tulsa Area) Oklahoma

Posted 29 March 2021 - 08:22 PM

I noticed the Altair website no longer shows the 102F11ED as "out of stock" - so I presume available again for anyone that might be interested. https://www.altairas...cuser-467-p.asp

 

TS still shows their version is scheduled to arrive May 15: https://www.teleskop...AP-Focuser.html



#790 obsale

obsale

    Lift Off

  • -----
  • Posts: 7
  • Joined: 28 Mar 2021

Posted 29 March 2021 - 10:12 PM

It's not a problem - taking photos of stars - as they are bright to start with. Its a little different taking photos of nebula that are dim, and in some cases just brighter than the background.

50 images of 4 minutes, iso 1250, full frame, pixinsight and ps. I just did a simple illustrative basic something fast processing. you can see two images, one original another cropped to see some important aspects:

 

1) a very low chromatic aberration.

2) spherochromatism easily contained with a flattener.

3) there is no comma.

4) excellent Gaussian profile around the stars.

5) very round stars without significant distortions from external peaks.

6) good sky contrast.

7) good detail of the particular object (pillars of creation).

 

messier 16
 

8) Good background color sampling (no color stretching was done in processing).
evidently the result is more than satisfactory for a low cost refractor with the worst glass that can be coupled as ED.
I forgot!, 35 mm sensor for an excellent framing ratio and little vignetting. that in a quick optics would be big cuts of the image! ...


Edited by obsale, 29 March 2021 - 10:13 PM.

  • Bomber Bob and Jethro7 like this

#791 obsale

obsale

    Lift Off

  • -----
  • Posts: 7
  • Joined: 28 Mar 2021

Posted 29 March 2021 - 10:13 PM

 
messier 16 crop

  • KevH, Bomber Bob and Jethro7 like this

#792 obsale

obsale

    Lift Off

  • -----
  • Posts: 7
  • Joined: 28 Mar 2021

Posted 29 March 2021 - 10:27 PM

super crop messier 16
 
look at the incredible degree of resolution for a lens of only 4 inches!

don't you think it can get older siblings in trouble?


Edited by obsale, 29 March 2021 - 10:36 PM.

  • siriusandthepup, JKAstro, KevH and 4 others like this

#793 starcanoe

starcanoe

    Mercury-Atlas

  • *****
  • Posts: 2,804
  • Joined: 07 Nov 2013
  • Loc: Gulf Coast, Panhandle of Florida

Posted 30 March 2021 - 06:37 AM

I've always kinda wondered about these super fast refractors that also aren't particularly large. As noted by others the image scale only works well for rather large objects in the sky. There are a lot more moderate and small objects in the sky than large ones.

 

These days i get the impression that stitching together images is fairly workable if the object doesn't fit in the frame. On the other hand blowing up a small object in the frame is more problematic given the physics of optics and sensors.

 

Nice to see good work done with a more modest set up. 


Edited by starcanoe, 30 March 2021 - 06:38 AM.

  • Bomber Bob and Jethro7 like this

#794 russell23

russell23

    Voyager 1

  • *****
  • Posts: 11,789
  • Joined: 31 May 2009
  • Loc: Upstate NY

Posted 03 April 2021 - 09:21 AM

I'll just say, if you have one of these scopes, try a 28mm RKE in it!  Wow!  What a combination!

 

Last night was interesting.  It probably was seeing conditions, but I set my Starwave 102 and SV102 Access up and it was definitely easier to get pinpoint sharp stars in the Starwave and the stars were definitely tighter in the Starwave. 

 

Dave


  • Don Taylor, areyoukiddingme, Tyson M and 2 others like this

#795 russell23

russell23

    Voyager 1

  • *****
  • Posts: 11,789
  • Joined: 31 May 2009
  • Loc: Upstate NY

Posted 08 April 2021 - 12:47 PM

I've had a couple really nice nights for 3 hour observing sessions over the last few days.  I spent quite a bit of time looking at galaxies and the contrast of the 102mm f/11 continues to impress.  I think this scope is providing the best views of galaxies i have seen in a 4" class refractor. 


  • Don Taylor and Bomber Bob like this

#796 Don Taylor

Don Taylor

    Apollo

  • *****
  • Posts: 1,366
  • Joined: 12 Jul 2009
  • Loc: Broken Arrow (Tulsa Area) Oklahoma

Posted 09 April 2021 - 09:04 AM

I've had a couple really nice nights for 3 hour observing sessions over the last few days.  I spent quite a bit of time looking at galaxies and the contrast of the 102mm f/11 continues to impress.  I think this scope is providing the best views of galaxies i have seen in a 4" class refractor. 

 

Before obtaining the 102F11ED I never would have thought of going galaxy hunting with a 4" refractor. Going to TSP or Okie-Tex I would always take the Dob.  But I too was amazed by what could be seen with the 4" ED in M51 after Thomas' post #295 - and my similar report in post #361, in my case from a darker (but not truly dark) site. Glad you are enjoying the scope!


  • russell23 likes this

#797 Jethro7

Jethro7

    Surveyor 1

  • *****
  • Posts: 1,853
  • Joined: 17 Dec 2018
  • Loc: N.W. Florida

Posted 10 April 2021 - 07:51 AM

I've had a couple really nice nights for 3 hour observing sessions over the last few days.  I spent quite a bit of time looking at galaxies and the contrast of the 102mm f/11 continues to impress.  I think this scope is providing the best views of galaxies i have seen in a 4" class refractor. 

Hello Russell23,

My findings are just like Don Taylor's. I never would have thought of using a 4" F/11 scope for galaxy hunting or other types of observing. I just bought it for Lunar and Planetary observations. The Altair 102ED F/11 scope has surprised and delighted me more than any other scope I own.  I am happy that you are really enjoying your scope.

 

HAPPY SKIES AND KEEP LOOKING UP Jethro


Edited by Jethro7, 10 April 2021 - 07:52 AM.

  • russell23 likes this

#798 Robert Zebahl

Robert Zebahl

    Vostok 1

  • -----
  • Posts: 128
  • Joined: 12 Aug 2016
  • Loc: Leipzig, Germany

Posted Today, 02:58 AM

I would like to give a small update regarding the optics. A few days ago I did a short test on an artificial star and did not expect any issues. At high magnification (~300x) I saw a triangular diffraction disk and 3 arcs of the first diffraction ring: pinched optics. I never really noticed this before. I then tested the refractor on a real star: Not much of the triangular shape was visible, but astigmatism, which seemed to get stronger over time. It was not very cold outside. Actually, a pinched optic is not a problem. You just have to loosen the retaining ring slightly. However, this proved to be difficult.

The retaining ring was glued. Behind the retaining ring is another ring, which connects the lens cell with the tube. This one was also glued. I built a small tool to loosen the retaining ring. Without success. In the end, I was able to loosen the glue with a small paintbrush and acetone. Unfortunately, quite a few splatters of acetone made it onto the lens. Most of it could be removed by cleaning. There are still a few spots on the lens, which are optically insignificant. Another test on the artificial star showed a decent image: well centered without coma, no distortion at all. Slightly out of focus, some astigmatism was visible.


  • daquad, Bomber Bob, jeremiah2229 and 1 other like this

#799 daquad

daquad

    Surveyor 1

  • *****
  • Posts: 1,947
  • Joined: 14 May 2008

Posted Today, 07:01 PM

I would like to give a small update regarding the optics. A few days ago I did a short test on an artificial star and did not expect any issues. At high magnification (~300x) I saw a triangular diffraction disk and 3 arcs of the first diffraction ring: pinched optics. I never really noticed this before. I then tested the refractor on a real star: Not much of the triangular shape was visible, but astigmatism, which seemed to get stronger over time. It was not very cold outside. Actually, a pinched optic is not a problem. You just have to loosen the retaining ring slightly. However, this proved to be difficult.

The retaining ring was glued. Behind the retaining ring is another ring, which connects the lens cell with the tube. This one was also glued. I built a small tool to loosen the retaining ring. Without success. In the end, I was able to loosen the glue with a small paintbrush and acetone. Unfortunately, quite a few splatters of acetone made it onto the lens. Most of it could be removed by cleaning. There are still a few spots on the lens, which are optically insignificant. Another test on the artificial star showed a decent image: well centered without coma, no distortion at all. Slightly out of focus, some astigmatism was visible.

Glad you were able to correct the problem.  My experience was a bit different.

 

When I received my Starwave 102 DE f/11 the first thing I did was check the collimation with a Cheshire eyepiece.  As there is no provision for user collimation, I was a bit concerned that the collimation would be off, but at f/11 it would not be much of a problem.  Well, I was surprised to see that the collimation was perfect, all three reflections perfectly concentric.  Impressive, when you consider that the scope traveled from the UK to New York, to Boston, and to my home in Rhode Island and still remained collimated.

 

The next test was under the stars to check for astigmatism.  At 280X I could not detect any ellipticity of the stellar image  as I moved from outside to inside focus.  So astigmatism is well controlled.  It was a rather poor night, but the intra and extra focal positions showed nearly identical patterns without a green filter, so SA  seems to be OK.  However, I plan to  do more testing for SA on a better seeing night with a green filter.  Of course even if the patterns are identical, in green light, spherochromatism will still be present. 

 

As an aside, my old 4" f/15.5 Jaegers shows distinctly different intra and extra focal patterns without a filter, yet produces color-free lunar images at 50X/inch; with a green filter the patterns are close, but still not identical.  I expect the Starwave to have less spherochromatism than the Jaegers, but I am skeptical that I will see any more detail with the Starwave, than I can with the Jaegers.

 

The fit and finish of the Starwave is excellent from the pearl finish of the OTA, the smooth operation of the dual speed focuser and the sliding dew shield, which stays put and does not move from the fully extended position.  The coatings are excellent and the lens seems to disappear when looking down the the tube.

 

Anyone in the market for a longish refractor should consider the Starwave 102ED f/11.

 

Dom Q.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics