54 replies to this topic

[Jeff B]

This scope has been on my DPAC bucket list ever since it came out.  So, when a sample at a very good price (IMO anyway) showed up relatively close, I dove in the deep end and purchased it.

 

Four days later Fedex tucked it in my car port.  I then used my hand truck to wheel it into my bunker/scope warehouse, AKA, my basement.

 

The whole shipment weighs 66 pounds with the packaging and case easily outweighing the scope by 2 to 1.  

 

Fit and finish are excellent.  The objective cell and screw on dew shield are particularly robust.  The stock, dual speed, focuser is tight but smooth.  However it has the standard mediocre, two set screws at 90 degrees apart, Synta visual back.   The rings are light weight but fine.  I replaced the V dovetail with a nice Losmandy style.  No accessories other than the rings/V dovetail were included, which is just fine for me.  I'm quite impressed with its straight forward utility.

 

Jeff

 

 

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[Darren Drake]

I have one of these and love it.  I've also tested it extensively with single pass but will wait for your results before once again sharing my results...

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[Jeff B]

With my new arrivals, I always check the focuser alignment with the center of the objective using an objective mask with a whole in the middle and my Glatter (R.I.P) laser in the focuser.    This is where the stock visual back shows it's limitations as the laser beam could wonder a bit off center, maybe 3-4mm, or be dead center depending on how I mounted the laser and how I tightened those set screws.  So at most, you might be looking, maybe .1 to .15 degrees off axis....or completely on axis.  Fortunately there are replacement visual backs out there.  The picture shows the laser shining through the middle and reflecting off of the DPAC flat.  I mean the scope does have a price point, but, come on, how much of a cost difference would it be to upgrade that VB? 

 

The next thing I do is check the "collimation" of the objective using a Cheshire eyepiece (with no X hairs!) to see how the reflections off of the backs of the two lens elements line up with each other.  They should form a single dot.  And they did, but, thanks to that VB, the dot would typically be slightly offset from the image of the Cheshire aperture by maybe "half a dot width" ...or maybe not.   That cheap VB strikes again.

 

Of note is the OTA is not bino-friendly, even with a prism 1.25" diagonal.  A barlow/OCS/GPC type  element is needed to get to focus.  When at focus with my reference AP 2" diagonal, there was ~32mm of back focus remaining.  However, the OTA does have a two transition pieces between the focuser body and main tube which total 3" long.  Combine that with the 6" from the focuser bottom to the top of the VB at focus, gives 9" (or 230mm) of room for a more compact focuser assembly between the 2" diagonal and the main tube.  Subtract 115mm for a bino-viewer's optical path length would  give ~ 100mms for the height of a fully racked in replacement focuser.  So, it seems making the OTA bino--friendly withoutcutting back the main tube can be done with scrupulous choices in adapter design and focuser choice.   

 

Another thing of note is that with the 2" diagonal, the fully Illuminated FOV at focus is very small, maybe just a few MMs, due to the baffling in the focuser draw tube and/or the main tube.  I'm going to rearrange things internally because, for me at least, one of the big attractions of refractors is the ability to have huge fully illuminated FOVs. Why choke it down like that?  With my own refractor ATM projects I can get huge FI FOVs but still have a dead black interior.  I would guess it's some sort of design dogma....like those stupid eyepiece undercuts.

 

Jeff

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[Erik Bakker]

[...]

 

Another thing of note is that with the 2" diagonal, the fully Illuminated FOV at focus is very small, maybe just a few MMs, due to the baffling in the focuser draw tube and/or the main tube.  I'm going to rearrange things internally because, for me at least, one of the big attractions of refractors is the ability to have huge fully illuminated FOVs. Why choke it down like that?  With my own refractor ATM projects I can get huge FI FOVs but still have a dead black interior.  I would guess it's some sort of design dogma....like those stupid eyepiece undercuts.

 

Jeff

In the scopes I had that were baffled that narrow, removing the baffles showed why. Color correction and optical performance at full aperture were not up to snuff at the widest opening, creating the illusion of great performance at first glance. Look forward to your findings on the SW EVOPSTAR 150 ED performance at full aperture.

[A Y]

I have one of these and love it.  I've also tested it extensively with single pass but will wait for your results before once again sharing my results...

This is like a visual representation of all those threads when someone asks whether they should get a refractor or a Dob. 

 

I have a 150ED and am excited to see Jeff's results, good or bad!

Edited by A Y, 05 May 2023 - 12:49 PM.

[Rutilus]

In the scopes I had that were baffled that narrow, removing the baffles showed why. Color correction and optical performance at full aperture were not up to snuff at the widest opening, creating the illusion of great performance at first glance. Look forward to your findings on the SW EVOPSTAR 150 ED performance at full aperture.

I'm too looking forward with interest. It would be nice if Jeff could test the scope first with the factory positioned baffles,

and then again after the modification. 

Edited by Erik Bakker, 05 May 2023 - 04:29 PM.

[Jeff B]

Ok, enough of the preliminaries, how about the stuff mentioned in the Title?

 

So, first the green images.

 

This is really very good spherical correction in green.  An excellent edge too.

 

The contrast enhanced at focus image shows obvious (in DPAC) circular figuring errors along with some radial polish lines and a very small "pimple" or "nipple" right in the middle.

 

The overall polish of the system is smooth, with smooth transitions between the circular zones.  The magnitude of those zones is small as I see only minor/subtle disturbances in the Ronchi line shadows due to them.  But, yes, you can see them.  But, yes, this is DPAC, which can clearly show everything, every wart and pimple, in sharp relief.  Which is exactly why some of us here use it.

 

And speaking of pimples.  To me, that center pimple is the only slightly abrupt artifact.  But it's really very small and a feature I have found common in some of the Asian sourced lenses I have tested, particularly achromats.  But this is the smallest I've seen.   

 

To me the uniformity of the polish makes the figuring errors stand out, but they are quite mild, errors of revolution and any negative effect they have on contrast I would imagine to be completely invisible outside of the test bench....except, based upon previous experiences, I bet I can catch out that "pimple" during a high power star test as a hot/bright center on one side of the out of focus patterns.  But at focus?  No.

 

This polish also strongly suggests to me predominantly machine polishing is involved, though, based on this sample, they have that process under very good control.

 

Finally, I noticed that it was actually quite easy to find a "null" spot with even illumination of the wave front.  It is not a precise  "null" as there are artifacts and texture but it's a uniform surface of revolution.  Also note the rather small contrast difference between the inside and outside of focus images.  That has typically meant good polish and excellent spherical correction.

 

  

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[Jeff B]

In the scopes I had that were baffled that narrow, removing the baffles showed why. Color correction and optical performance at full aperture were not up to snuff at the widest opening, createing the illusion of great performance at first glance. Look forward to your findings on the SW EVOPSTAR 150 ED performance at full aperture.

Funny you should ask Erik. 

 

One thing I've started doing is taking a shot with the scope at focus but with my newtonian collimation sight cap in place of the ronchi screen/LED assembly.  This documents if I'm getting the full aperture.  And I am with this sample but the fully illuminated FOV is very small, maybe 3-4mm. 

 

In my ATM projects where the tube inner diameter is very close to the size of the objective's aperture, I have always paid special baffling/flocking attention to the first 120 mm or so of the space behind the objective to kill off early reflections and light scatter, the kind of reflection you see in this shot.  I would typically place two baffles just slightly larger than the objective's aperture in that "zone" along with some very effective flocking.  Boom, no bathtub ring of scattered/reflected.  It's really not too bad here at all.  But, I will eliminate it along with considerably expanding the fully Illuminated FOV.  

 

Jeff

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[peleuba]

This polish also strongly suggests to me predominantly machine polishing is involved, though, based on this sample, they have that process under very good control.

 

Another good test, Jeff, and I am not speaking about the results.  Your execution is perfect.

 

Yes - 100% machine polishing or the blemishes on the lens would be slightly more random and less concentric.

 

I would be pretty happy with this lens.

 

I was just reading Erik's comments on the baffles and he is, of course, correct.   Its all too common to have misplaced baffles or extra long focuser draw tubes that eclipse the light path giving the impression of a higher level of correction then may actually exist at full aperture.

Edited by peleuba, 05 May 2023 - 02:07 PM.

[CHASLX200]

Mine was very good for the price of under 2k when i bought it.  450x was easy on Jupiter and Saturn. I am sure a 6" AP or Tak would do better but at 3 to 5 times the cost and that is something that i won't be buying for around 5% better views.

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Edited by CHASLX200, 05 May 2023 - 06:17 PM.

[Jeff B]

Here are the color images.  Place the cursor over the images to read the titles. 

 

First the white light Master Images and then my usual color montages derived from the Masters.

 

Both Masters clearly show some secondary spectrum as blue/purple and yellow/green fringing of the R/L ronchi line shadows.  The blue tips to the L/R lines also indicate spherochromatism in the blue.   All of this is also clearly seen in the color montages, specifically some blue secondary spectrum and spherochromatism (over correction) with mild/minor secondary spectrum and spherochromatism (under correction) in red, green is very slightly over corrected all relative to the yellow.  

 

But I do have to say that these color aberrations are rather astonishingly well balanced across the spectrum for a 6" F8 FPL-51 based doublet.  This is a well designed lens, tuned to the heart of the visual spectrum and an excellent, well made, sample, randomly bought on the open range, and not cherry picked.  

 

This bench performance is also remarkably similar to my old AP 178 F9  pre-ED Starfire, right down to the center "pimple" and mild green over correction.   That objective is extremely sharp too. 

 

I also saw no indication of astigmatism with the SW 150ED (no clocking/rotation of the line shadows when sweeping from one side of focus to the other).

 

This is excellent bench DPAC performance, especially for the aperture price point.

 

I will post tonight's star test results tomorrow.

 

Jeff

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[Scott in NC]

Nice, Jeff—a very enjoyable read.  Hope you get a chance to enjoy this scope under the stars tonight!  I’m eagerly awaiting the star test results, and will be very interested to hear how that aligns with your DPAC findings.

[bob midiri]

Really exceptional for a large Mass produced relatively inexpensive ED lens, thanks Jeff for sharing. If this is an example of Skywatchers mass produced lens, on a consistant basis, no wonder these 6" ED scopes get such good reviews! I get Exceptional views with my example and am quite satisfied! 

[drprovi57]

The Sky-Watcher Esprit 150mm ED Triplet APO Refractor I have found is also excellent - yes more expensive by a fact of 3 compared to the SW150ED - but still an excellent buy compared to other 150 APO's .. also is available and not 1 year wait time.   The Esprit is also bino-friendly with a substantial focuser and retractable dew shield.  

 

I would love to see a DPAC test for the SW150 ED Triplet APO 

 

Jason

[Jeff B]

Nice, Jeff—a very enjoyable read.  Hope you get a chance to enjoy this scope under the stars tonight!  I’m eagerly awaiting the star test results, and will be very interested to hear how that aligns with your DPAC findings.

Thanks Scott, and speaking of the star testing aligning with the DPAC data, yes it does.

 

That's the short story version, and as I've said in the past..just yesterday actually... I'm not very good at that.

 

The scope came out of a cool basement so it was actually warming up at first.  It is a perfect fit up to my trusty AP Mach 1.  The OTA was quite "lite weight" and an easy lift into the rings for this old guy.  Once installed, about a couple of hours before sunset, I just had to slew over to Venus.  Surprise number one was that the seeing was very steady despite, or maybe because of, the high thin clouds.   Surprise number two came from the lack of terrible color error bordering the planet.  I know, I know, even my achromats will not show much "CA" around Venus during the day as the sky brightness does a good job of hiding it, but the body of the planet usually shows a mild purple tint.  The SW 150ED showed a very white disk and it was sharp at 110x.  Cranking up the power to 164x still showed a sharp disk but also a slightly ruddy tint to the globe.  But the scope was still warming up too.

 

I parked the scope to present a minimum profile to the setting sun, did some yardwork, shanked a couple of short wedge shots, grumbled about that and had some dinner.

 

About 15 minutes before sunset I got "serious".  The scope had been in shadow for over an hour, the ambient temperature had dropped a degree or two and, around here, the upper atmosphere was calm.  I used my AP 2" diagonal and I broke two star testing rules right up front my using my TV 3x and Silver Top 2x barlows along with my 22mm & 10mm Silver Top Plossl, old 12mm Celestron Ortho and went crazy with my 7mm UO volcano top ortho.  All viewing was boring old cyclops vision. I used a trick Roland taught me years...ok....decades... ago, of putting a deep green filter over the eyepiece eye lens to isolate green.

 

Venus, though much brighter and in much higher contrast against the sky was still quite white.  However, a blue/ruddy border was seen.  The image was quite sharp though.  Best, most pleasant, views were at 164x and 200x.   Really very nice and I could talk myself into seeing shadings in the clouds.

 

Chosen stars were Pollux, Procyon and Castor.  I started with Pollux at 164x and it became instantly apparent that I could go much higher in power and this was a very nice sample.  Boom, right up to 300x.  The airy disk at focus was slightly ruddy/orange, round and surrounded by a 360 degree ruddy first ring with very faint second ring.  No Coma at all and no astigmatism was seen, even on the way to focus.  Hanging the green filter in front of the eyepiece and just barley touching up focus, showed a nice round airy disk and just a single, dimmer 360 first ring.   Going crazy at 514x, the atmosphere was intruding much more but I got basically the same result.

 

Ditto Procyon but with a more yellow tint to the airy disk with a more white first ring.  Ditto to Pollux with the green filter but I also could see no meaningful differences on either side of focus close in, with the rings smoothly shrinking down to focus and then smoothly expanding out the other side.  I was also surprised to not find or catch out that center "pimple" just inside/outside of focus.  

 

Castor was just beautiful!  Really rather white with a blue tint.  Overall, the prettiest views were at 200x and 240x.

 

So, star testing was just superb really.

 

Jeff

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Edited by Jeff B, 06 May 2023 - 09:04 PM.

[Scott in NC]

Very nice, Jeff.  It sounds like both of us had enjoyable observation sessions with our respective scopes last night.  I had to post an observing report too, lest people start to think that all I did nowadays was DPAC testing.

[Scott in NC]

On another note, I just saw a nice SW150ED on AM.  I’m going to leave it for someone else to purchase, but honestly that scope wouldn’t have even been on my radar had it not been for your nice report.  Thanks again for sharing that!

[Bobby Astro]

The Sky-Watcher Esprit 150mm ED Triplet APO Refractor I have found is also excellent - yes more expensive by a fact of 3 compared to the SW150ED - but still an excellent buy compared to other 150 APO's .. also is available and not 1 year wait time.   The Esprit is also bino-friendly with a substantial focuser and retractable dew shield.  

 

I would love to see a DPAC test for the SW150 ED Triplet APO 

 

Jason

I just sold an Espirit 150 to a guy who will use it for imaging. I’m mainly visual and the Espirit was superb with a basically perfect start test. Very similar or even better than the second sample in that “5 sample test” floating around on the internet.

I sold it and immediately regretted my decision and had purchased another new scope (C-11) but wanted another refractor, so purchased a new Evostar 150 to go along with the 11”.

Actually a better choice for me anyway as it is lighter and I won’t be doing any imaging anytime soon.

 

Should be here next week. IMO, the SW’s are amazing not only for the price, but just amazing period! Super happy to see the Evostar seems to follow the same high quality optical path!

Edited by Bobby Astro, 07 May 2023 - 08:30 AM.

[Joe G]

The Sky-Watcher Esprit 150mm ED Triplet APO Refractor I have found is also excellent - yes more expensive by a fact of 3 compared to the SW150ED - but still an excellent buy compared to other 150 APO's .. also is available and not 1 year wait time.   The Esprit is also bino-friendly with a substantial focuser and retractable dew shield.  

 

I would love to see a DPAC test for the SW150 ED Triplet APO 

 

Jason

https://www.cloudyni.../#entry12633609
 

[Jeff B]

I have one of these and love it.  I've also tested it extensively with single pass but will wait for your results before once again sharing my results...

Share away Darren!   

 

I have plenty of questions for you too.

 

Jeff 

[Scott in NC]

I’d like to see Darren’s results too.  The more the merrier!

[Illinois]

I still like my SW Evostar 150 ED and it’s big refractor. 1200mm is reason I bought is for my serious planetary.  I think SW Espirt is shorter is for astro photography.  I think SW wouldn’t tell us what kind of glass in Evostar so anyone know what kind of glass it is?  Here’s picture of me and big 150mm refractor. 

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[CHASLX200]

No one knows the glass type. I don't even care about glass type. If i get a super image at 450x on the planets then it don't matter. Maybe if i paid AP or Tak prices for a 6" i would care a little bit. But at 1900 smackers when i got mine it was the best deal going.

[Jeff B]

If I recall properly (which is increasingly doubtful) the early SW lit mentioned FPL-51, which is what I mentioned above.   What everybody keeps secret is (are) the mating element (s). 

 

Chas makes an excellent point.  I was really enjoying myself using this sample.  That's what mattered in the moment.  I quickly began to ignored the color errors in favor of the excellent views with tight star images even though I was firmly in "review mode".  This reminds me a lot of my high end audio days where if the component/system swept me up in the music, that's what really mattered in the end, despite my predilections towards measurements (and that hobby is just chockfull of measurements).  

 

This scope drove home another point for me.  Good spherical, coma and astigmatism corrections, all trump minor color errors at the ends of spectrum.  Again, with another nod to high end audio, get the midrange right and everything else above and below is salt and pepper to taste.  Screw up the midrange and no amount of flavoring makes for a tasty  experience.  

 

This objective has excellent spherical correction in the heart of the visual range, no astigmatism or coma either.  I have more stuff I'm going to try, but, so far, it's visually very tasty....though that stock visual back does have a slightly bitter aftertaste. 

 

Jeff

[fate187]

Thank you for the as usual thorough investigation using DPAC! I am planning on getting such a scope exchanging one of my existing telescopes for this affordable lens. I will probably cut the ota to make in binofriendly...

However, I have one question regarding your method to check collimation of the focuser relative to lens. You put the Glatter laser into the focuser right. The beam goes though the lens and is off center depending on the off-axis amount. But How to find the center with you "mask" you employ? How do you ensure the mark is in the middle of the lens? Maybe thinking too complicated, but its an interesting test I wanted to do myself!

With my new arrivals, I always check the focuser alignment with the center of the objective using an objective mask with a whole in the middle and my Glatter (R.I.P) laser in the focuser.    This is where the stock visual back shows it's limitations as the laser beam could wonder a bit off center, maybe 3-4mm, or be dead center depending on how I mounted the laser and how I tightened those set screws.  So at most, you might be looking, maybe .1 to .15 degrees off axis....or completely on axis.  Fortunately there are replacement visual backs out there.  The picture shows the laser shining through the middle and reflecting off of the DPAC flat.  I mean the scope does have a price point, but, come on, how much of a cost difference would it be to upgrade that VB? 

 

The next thing I do is check the "collimation" of the objective using a Cheshire eyepiece (with no X hairs!) to see how the reflections off of the backs of the two lens elements line up with each other.  They should form a single dot.  And they did, but, thanks to that VB, the dot would typically be slightly offset from the image of the Cheshire aperture by maybe "half a dot width" ...or maybe not.   That cheap VB strikes again.

 

Of note is the OTA is not bino-friendly, even with a prism 1.25" diagonal.  A barlow/OCS/GPC type  element is needed to get to focus.  When at focus with my reference AP 2" diagonal, there was ~32mm of back focus remaining.  However, the OTA does have a two transition pieces between the focuser body and main tube which total 3" long.  Combine that with the 6" from the focuser bottom to the top of the VB at focus, gives 9" (or 230mm) of room for a more compact focuser assembly between the 2" diagonal and the main tube.  Subtract 115mm for a bino-viewer's optical path length would  give ~ 100mms for the height of a fully racked in replacement focuser.  So, it seems making the OTA bino--friendly withoutcutting back the main tube can be done with scrupulous choices in adapter design and focuser choice.   

 

Another thing of note is that with the 2" diagonal, the fully Illuminated FOV at focus is very small, maybe just a few MMs, due to the baffling in the focuser draw tube and/or the main tube.  I'm going to rearrange things internally because, for me at least, one of the big attractions of refractors is the ability to have huge fully illuminated FOVs. Why choke it down like that?  With my own refractor ATM projects I can get huge FI FOVs but still have a dead black interior.  I would guess it's some sort of design dogma....like those stupid eyepiece undercuts.

 

Jeff

 

Very nice