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Starwave 102ED f11 (yes, ED)

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#251 Robert Zebahl

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Posted 04 April 2019 - 04:03 PM

This is my second evening with the new refractor. Good thing: I saw stars. Bad thing: Conditions! Very low transparancy (today: Bortle 7, SQM-L 18.7) and very bad seeing. The image in the eyepiece was just jumping around at high frequency. I could not see any diffraction rings on brighter stars, just a halo. But I observed something:

 

Messier 82 was visible at 22x and showed at 125x indications of the dark lanes with averted vision. But this should not be assumed as an indicator for high quality optics.

 

Messier 44 was a little surprise: At 22x the color rendition of stars was very good. I saw a lot of different color grades. Actually Messier 44 was just a starting point for a star hop to the triple system zeta Cnc, but I skipped this due to the bad conditions.

 

Up to now I am quite happy and I looking forward for better conditions and the moon. At the end of April there is a little star party in our region, where we probably have the chance to compare this refractor to some others: TMP 105 APO, Zeiss AS 100/1000 or TAL100 and Tak FC100DL.


Edited by Robert Zebahl, 05 April 2019 - 01:37 AM.

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#252 stevew

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Posted 05 April 2019 - 01:47 AM

This is my second evening with the new refractor. Good thing: I saw stars. Bad thing: Conditions! Very low transparancy (today: Bortle 7, SQM-L 18.7) and very bad seeing.

 

Similar conditions to what I have had lately.

Congratulations on the scope.

Looking forward to more of your reports under better skies.



#253 Robert Zebahl

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Posted 05 April 2019 - 08:47 AM

I've made two images with a DSLR (exposure time 1/2 sec, ISO100) with a barlow in between of an artificial star in a distance of about 10meters. The defocus was roughly 10lambda. First image is extra-, second one intrafocal. Maybe this helps to get a better impression of the spherical aberration at least for my sample.

 

But this is just a quick shot, not a scientific star test smirk.gif

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Edited by Robert Zebahl, 05 April 2019 - 09:00 AM.

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#254 Robert Zebahl

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Posted 05 April 2019 - 10:41 AM

I did some further images with a green filter using a barlow. Exposure time 1/2sec, ISO800. defocus 5mm (~9lambda). First image extrafocal, second in focus, third intrafocal. There is little astigmatism visible, but I am pretty sure, that this comes from the 2" diagonal mirror. Visually this was never an issue for me and it is hard to see in focus, at least to my eyes. I have another diagonal mirror (1.25") which seems to be better.

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Edited by Robert Zebahl, 05 April 2019 - 10:41 AM.

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#255 daquad

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Posted 05 April 2019 - 12:49 PM

I did some further images with a green filter using a barlow. Exposure time 1/2sec, ISO800. defocus 5mm (~9lambda). First image extrafocal, second in focus, third intrafocal. There is little astigmatism visible, but I am pretty sure, that this comes from the 2" diagonal mirror. Visually this was never an issue for me and it is hard to see in focus, at least to my eyes. I have another diagonal mirror (1.25") which seems to be better.

Looks like a fine lens.  Why did you take the pic with the diagonal in place?  

 

Dom Q.



#256 Robert Zebahl

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Posted 05 April 2019 - 12:51 PM

Looks like a fine lens.  Why did you take the pic with the diagonal in place?  

 

Dom Q.

To reach the focus smirk.gif  And even with the diagonal the was a pretty large tower of extensions...



#257 daquad

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Posted 05 April 2019 - 01:23 PM

To reach the focus smirk.gif  And even with the diagonal the was a pretty large tower of extensions...

Oh.  I didn't realize it was an indoor test.  



#258 Niklo

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Posted 05 April 2019 - 03:24 PM

Hello Robert,

thank you for sharing your star test photos. Intra and extra focal look good. The little bit astigmatism could be really caused by 2" diagonal mirror. 

How does the airy disk and the first refraction ring looks like in the eyepiece? For the colour correction a photo of the star in the focus without green filter could be interesting but you can describe the view through the eyepiece in focus, too. For a real star test I would try to do it without diagonal mirror.

Enjoy your nice APO refractor.

Clear skies,

  Roland


Edited by Niklo, 05 April 2019 - 03:25 PM.


#259 Robert Zebahl

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Posted 05 April 2019 - 06:44 PM

I've attached an image in focus without a green filter. It was captured together with my first "star test images".

 

Today I observed together with Uwe Pilz and we did some comparisons to his TMB 105/650 APO. We mainly observed double stars like zeta Cnc, STF1426 (both pretty tight for 4 inch), but also Castor and mu 1/2 Boo. Both refractors showed almost identical images. You have to search for differences.

 

When we observed Messier 44 at same exit pupil, we both had the impression, that the f11 refractor showed the stars slightly tinier. But we used different eyepieces: Fujiyama  HD Ortho Okular 25 mm (TMB) and 40mm Pentax XL (Starwave).

 

Overall we came to the conclusion, that my sample has quite decent optics without any defects I should worry about. Cold temperatures is a different topic and might lead to some distortion.

 

Between the TMB APO and the Starwave there was just one "evident" difference: Color correction. We observed Regulus at about 120x. The Starwave showed a rather small, dark blue halo, which didn't bothered me. Here the TMB was colorfree.

 

When I was at home, I additionally compared quickly some of my other refractors on Vega. My Vixen ED70SS (f/5.7) showed at 133x a small dark blue halo. The Zeiss Telementor I (63/840mm) showed more color at 140x, which I also noticed when observing the moon. But even this was never an issue for me. The Starwave is in between regarding color correction at 187x, but more towards the Zeiss. As Thomas said, it is not an APO, but the color correction is at least for me very good. And the correction of other aberrations is more important then hunting for the last blue hint.

 

Update: The Airy disk was very sharp without any defects. The first diffraction ring was faint and not evident. The conditions, especially the seeing, was way better than before, but not perfect.

Attached Thumbnails

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Edited by Robert Zebahl, 05 April 2019 - 07:00 PM.

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#260 karstenkoch

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Posted 05 April 2019 - 09:24 PM

Well, my time outside under the stars with this scope continues to to be limited to those few brief moments I had, which has given me some time to look the scope over inside. So, I was turning this thing on it's mount inside the house when I happened to catch the light from a ceiling light shine down the tube...

IMG_4845.JPG

Okay, so just so you know, I'm not a perfectionist when it comes to dust on a lens. But, looking down the OTA of my new prize, I couldn't help but think that this was just a little too much dust to be hanging out having a smoke leaning back against the inside lens of my brand new scope. I could just see it in my minds eye blowing smoke in my face taunting me as I gazed wide-eyed down the tube. Overpersonification?

IMG_4843.JPG

Anyway, I also like to keep my lenses and mirrors clean, so I clean then fearlessly, but only when required and only using proper technique. I am totally willing and happy to unscrew the dew shade and lens cell (assuming it's a single assembly that allows this to be done) so I can hit it with some dry air and then lightly wipe it with 91% isopropyl alchohol. But, this thing is still under warranty. So, I guess I'll email Land Sea & Sky and ask them if this is okay first.

IMG_4844.JPG

I really like the scope. I am also wondering about potential contrast reduction with this amount of dust on the lens. I haven't spent near enough time with it yet to know if this is causing any issue. 99% of my observing is done in LP areas. So, what do you think? Tempest in a teapot? Do whatever it takes to clean it?

Edited by karstenkoch, 05 April 2019 - 09:53 PM.


#261 Tyson M

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Posted 05 April 2019 - 10:32 PM

Well, my time outside under the stars with this scope continues to to be limited to those few brief moments I had, which has given me some time to look the scope over inside. So, I was turning this thing on it's mount inside the house when I happened to catch the light from a ceiling light shine down the tube...

attachicon.gif IMG_4845.JPG

Okay, so just so you know, I'm not a perfectionist when it comes to dust on a lens. But, looking down the OTA of my new prize, I couldn't help but think that this was just a little too much dust to be hanging out having a smoke leaning back against the inside lens of my brand new scope. I could just see it in my minds eye blowing smoke in my face taunting me as I gazed wide-eyed down the tube. Overpersonification?

attachicon.gif IMG_4843.JPG

Anyway, I also like to keep my lenses and mirrors clean, so I clean then fearlessly, but only when required and only using proper technique. I am totally willing and happy to unscrew the dew shade and lens cell (assuming it's a single assembly that allows this to be done) so I can hit it with some dry air and then lightly wipe it with 91% isopropyl alchohol. But, this thing is still under warranty. So, I guess I'll email Land Sea & Sky and ask them if this is okay first.

attachicon.gif IMG_4844.JPG

I really like the scope. I am also wondering about potential contrast reduction with this amount of dust on the lens. I haven't spent near enough time with it yet to know if this is causing any issue. 99% of my observing is done in LP areas. So, what do you think? Tempest in a teapot? Do whatever it takes to clean it?

No canned compressed air, but bulb blower is fine. If you can unscrew the lens cell and use that front and back it should remove some of that.

 

In between the lens is stuck there unless deassembled and reassembled on a bench. 


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#262 Don Taylor

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Posted 05 April 2019 - 10:53 PM

I haven't spent near enough time with it yet to know if this is causing any issue. 99% of my observing is done in LP areas. So, what do you think? Tempest in a teapot? Do whatever it takes to clean it?

A new scope should not be like that - Land Sea & Sky should clean it for you. Especially so if there is dust between the elements.

 

(mine appears dust free - it's a real "black hole" down there. Your's should be too).  Sorry to hear this.


Edited by Don Taylor, 05 April 2019 - 10:54 PM.

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#263 Steve Allison

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Posted 06 April 2019 - 01:23 AM

No telescope from any manufacturer should ever be sent out with a lens this dirty IMHO. This reminds me of the filthy lenses in the Williams Optics refractors that were sent to Dr. D for inclusion in his widely read 4 inch refractor shootout conducted some years back.


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#264 Uwe Pilz

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Posted 06 April 2019 - 01:28 AM

Yesterday evening I meet Robert. Robert wrote his own report of that evening.

 

We stood for a few hours at my terrace and compared his brand new ASCENT 102ED f/11 refractor with my 105 mm f/6.2  TMB Apo. My TMB sits in a diy tube. I bought it from the widow of my  astronomical friend Ralf, which passed away much too early in 2014 –  with only 54. Ralf has a very fine understanding of astronomy and optica, but never too much money. I was not surprised to detect that the TMB lens has a slight vice - a slight amount of spherical aberration, SA. I have a protocol to the instrument, which measured 90% Strehl. Nevertheless it is a real good scope.

 

SA acts not the same amount as measured. If you measure, you use the central focus. With SA you focus slightly to the "sharp" side - the on where you have a prominent sharp ring. This leads to around half that error in fact.

 

I was curious how both scopes compare. In short: Nearly identical.

 

We looked at some double stars, nothing else was in the sky suitable for instrument testing. We started with Castor. The optical quality in the scopes was nearly identical. However, the view seemed slightly different, more a different feeling than a real difference in resolution. The Starwave showed nearly no aberrations: A very slight amount of SA (less than my TMB) and a tiny amount of blue blue light around the Castor A - just detectable with concentrated viewing. Of course, we used magnifications which were nearly identical.

 

We switched to zeta Canci, a not so easy triple. The closest double we could detect (but not split) was STF 1426 in Leo. Again a triple: 8" and 0.9".

 

I have my instrument at a Berlebach report tripod and use a syktee mount. I extend the legs of the report only slightly, Robert uses a UNI and a medium heavy Giro type mount, extended fully. As you might guess, we love azimutal and manual driven mounts. Both instruments had the same amount of stability with this setup. A moderate kick against the focuser was dampened in around a second.

 

We tried what happens if we set the Ascent at my tripod and mount. We had to extend the Report to full degree. This combination can be used – in case of need. But the kick against the focuser lead to a large amplitude of swinging which needed 8 seconds to quieten. Nothing you want to use regularly.

 

I get very good images with a 5x Televue powermate barlow lens and orthoscopic eyepieces. Robert can use normal wide angle eyepieces, TeleVue DeLiteI think.In both combinations the stars were sharp from edge to edge. Real sharp, down to the shape of the Airy disc. The DeLite have a much wider FOV,of course.

 

The conclusion: You can change the huge amount of money you need for a real good but short Apo against a fraction of the money for a real good f/11 ED Apo (which works Apo like). You have to pay for it with a larger tripod and mount and a longer scope. You get payed back less problems with the eyepieces, but again pay with the largest FOV (4° with my Apo and slightly more than 2° with the Starwave).

 

The Starwave is a very good instrument for sun, moodn, planets and double stars. It resolves what the stability of air delivers in most nights. The image is very pleasing. Colors of the stars are distinct: Something you sacrifice if you have false color to an amount more than neglectable.

 

At our next telescope meeting end of the month we have the chance to compare 4 4 inch scopes. I hink somebody of us writes a few words here afterwards.


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#265 Don Taylor

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Posted 06 April 2019 - 09:01 AM

Uwe & Robert:

 

Thank you for the interesting comparison.  I have not had an opportunity to compare to other scopes (mine or those owned by friends and club members) as the weather has not been cooperative. Last night was a club event and the only object visible through the clouds was a bright glow from Sirius. Hopefully the conditions will improve soon.

 

The initial indications from the three short observing sessions with the 102 F11 ED align with your observations. 



#266 Uwe Pilz

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Posted 06 April 2019 - 01:24 PM

Dear Karsten,

 

I would first check the optics. If it is real good (as Robert's) is I would stay with it and cleaned it. If is only of mediocre quality you may ask the seller for a replacement.

 

If most of the dust is at the outer lenses you may clean them with your usual procedure. Cleaning has nothing to do with warranty. I would resile, however, from opening the lens cell.

 

If I had this amount of dust at my used optics I would wait with cleaning, perhaps. If I had tons of spare time, it could be that I cleaned it. That means: The amount of dirt is a limiting case in my eyes. If most of it is at the accessible areas all is fine. A few motes of dust between the lenses don't play any role.


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#267 karstenkoch

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Posted 06 April 2019 - 02:25 PM

Dear Karsten,

 

I would first check the optics. If it is real good (as Robert's) is I would stay with it and cleaned it. If is only of mediocre quality you may ask the seller for a replacement.

 

If most of the dust is at the outer lenses you may clean them with your usual procedure. Cleaning has nothing to do with warranty. I would resile, however, from opening the lens cell.

 

If I had this amount of dust at my used optics I would wait with cleaning, perhaps. If I had tons of spare time, it could be that I cleaned it. That means: The amount of dirt is a limiting case in my eyes. If most of it is at the accessible areas all is fine. A few motes of dust between the lenses don't play any role.

Uwe,

 

The optics of the scope looked very good on my one test on Castor. And it's serial # 0001 of a historical new scope line smile.gif Okay, that's not relevant. Okay, not ENTIRELY relevant smile.gif

 

I've been in touch with Land Sea and Sky who has given me precise instructions for cleaning the front and back of the cell without touching the collimation of the lenses. Since I'm comfortable doing so, I'm going to clean the front and back. I'ver never even dreamed of going inside the cell itself. Well maybe in a nightmare.

 

I'll post pics.


Edited by karstenkoch, 06 April 2019 - 02:26 PM.

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#268 karstenkoch

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Posted 06 April 2019 - 10:30 PM

Sn 0001 is back in action.

 

The dew shield was the first to come off. You can see two of the collimation screws here. There are four sets of two screws located at 90 degree intervals.

 

IMG_4847.JPG

 

I carefully unscrewed the lens cell. It was on pretty tight. LS&S recommended a hairdryer to loosen it, but got it off with mere persistence and patience.

 

IMG_4886.JPG

 

A small hand blower did the trick. All of the dust on the rear of the cell was clinging only loosely to the glass.

 

IMG_4888.JPG

 

Getting the cell back on was easier than I thought. LS&S warned me about cross-threading due to the very fine threads, but I got it threaded properly with little effort.

 

IMG_4892.JPG

 

Dust pretty much shows up in any photo that has its focus point on the surface of the glass and you can still see some here. But it is in fact 99%+ freer of debris than before.

 

IMG_4897.JPG

 

I wasn't messing around tonight. The Lunt 100 degree 3.5mm went straight in the focuser and I got the scope pointed at Castor again. Seeing was excellent tonight. Castor showed showed two beautiful airy disks again with fragments of the first ring dancing around. I watched them drift right right to the edge of the field of view in perfect focus even as they fell off the edge. Success! I pointed the scope at Polaris next. Here's my iPhone AP attempt. See the secondary?

 

IMG_4910.JPG

 

I'm very happy with the results. I can't wait to get that Lunt on the moon.


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#269 Don Taylor

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Posted 06 April 2019 - 11:10 PM

Karsten!   Glad this turned out well. I too am waiting for the moon


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#270 Jond105

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Posted 06 April 2019 - 11:24 PM

Would it be stupid to sell an ed100 for one of these?

#271 Don Taylor

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Posted 07 April 2019 - 12:01 AM

Would it be stupid to sell an ed100 for one of these?

Don't know - I have not looked through an ED100 in quite a while.  IIRC it's an FPL-53* doublet F9 scope.  Purely speculating - I would guess there would be very little difference for visual use.  

 

(*note: did I see a thread here on CN where Synta recently stopped claiming the ED doublets used FPL-53? As if they have made a change in the optical prescription?)



#272 Jond105

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Posted 07 April 2019 - 12:20 AM

Don't know - I have not looked through an ED100 in quite a while. IIRC it's an FPL-53* doublet F9 scope. Purely speculating - I would guess there would be very little difference for visual use.

(*note: did I see a thread here on CN where Synta recently stopped claiming the ED doublets used FPL-53? As if they have made a change in the optical prescription?)


The 80-100-120 still use the FPL-53, what’s in the 72 and 150 they will not claim.
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#273 Niklo

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Posted 07 April 2019 - 04:56 AM

Would it be stupid to sell an ed100 for one of these?

If you already gave an ED 4" f/9 and if it shows a nice startest I wouldn't replace it.

For the colour correction I guess that you probably won't improve but you can compare with the description of Robert.

Even if Roberts star test is better then with your ED100 you have no guaranty to get such a good ED 4" f/11 as Robert did.

Clear skies,

Roland


Edited by Niklo, 07 April 2019 - 04:57 AM.

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#274 Robert Zebahl

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Posted 07 April 2019 - 04:57 AM

I just took a few photos regarding color correction. You can see the clearly reduced chromatic aberration compared to the Telementor.

Attached Thumbnails

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#275 Niklo

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Posted 07 April 2019 - 09:17 AM

I just took a few photos regarding color correction. You can see the clearly reduced chromatic aberration compared to the Telementor.

Hi Robert,

the telementor photo already looks nice from the colour correction but the ED 4" f/11 is superior. It looks APO like or very close to on the last photos.

Clear skies,

  Roland


Edited by Niklo, 07 April 2019 - 02:55 PM.



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