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Has anyone heard of this scope before (Sharpstar 61 EDPH)?

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#126 Cometeer

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Posted 25 July 2020 - 12:44 AM

Got mine in today.
 

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#127 Cometeer

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Posted 25 July 2020 - 12:45 AM

I’m quite happy with it, but I still need to fine tune  the spacing. Another 0.5mm should do it.

 

Single raw sub of M16 and M17 with a quick auto stretch. 
 

25ADC0C3-6B33-4CD4-B921-2AA3B7E30A4D.jpeg


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#128 kel123

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Posted 25 July 2020 - 08:42 AM

Got mine in today.

09CC5349-74B8-470C-909A-CC4355D2BECB.jpeg

54C97970-5CE0-4434-BB33-3F0C8F8BC3B0.jpeg

0B79A635-21D5-4C21-AC4C-06906764F25B.jpeg

51576BC1-51DF-44AF-AFE9-96BBEB0E4F24.jpeg

9C0EA41E-7636-47AB-9A5A-14D20978B600.jpeg


Wow! That's exactly the guide scope I am waiting for. What camera is that?

#129 kel123

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Posted 25 July 2020 - 08:43 AM

Is that the ioptron wedge?

#130 UKalwayscloudy

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Posted 25 July 2020 - 10:01 AM

To save others time I just tried the Sharpstar 61 with my small M63 (small versioin) .75 Riccardi reducer and it did not work. The focuser was racked all the way in and I still couldn't reach focus....the reducer would have to be about an inch inside the focuser to reach focus.

 

 

I had the Riccardi threaded directly into the focuser of the Sharpstar 61. 

Thanks chongo228. So we all seem to be happy with the supplied reducer but none of us have had any luck so far with any other kit. I got nowhere with the large Riccardi FF or FR and chongo228 had no luck with the small reducer. I've tried the Altair FF designed for their 360mm doublet and that got closer but the star shapes were poor even at APS-C. If anyone has the William Optics Flat 61 that might be interesting to try - it has some adjustment. Likewise for the Borg adjustable one, which has the tantalising feature that it looks like it extends into the focus tube and is adjustable for focal length. I'd be surprised if anyone has one sitting around, quite apart from the necessary 63-57 adapters it is very expensive. 

 

If anyone stumbles across a non-reducing flattener that does work do let us know. 



#131 Cometeer

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Posted 25 July 2020 - 10:55 AM

Wow! That's exactly the guide scope I am waiting for. What camera is that?

It is the QHY mini guide scope with a ZWO ASI224mc. It’s just a camera I had on hand, but a 120 mini would work just as well. 

 

Is that the ioptron wedge?

It is a William Optics wedge. Pricey, but very solid. 



#132 Cometeer

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Posted 25 July 2020 - 10:56 AM

Thanks chongo228. So we all seem to be happy with the supplied reducer but none of us have had any luck so far with any other kit. I got nowhere with the large Riccardi FF or FR and chongo228 had no luck with the small reducer. I've tried the Altair FF designed for their 360mm doublet and that got closer but the star shapes were poor even at APS-C. If anyone has the William Optics Flat 61 that might be interesting to try - it has some adjustment. Likewise for the Borg adjustable one, which has the tantalising feature that it looks like it extends into the focus tube and is adjustable for focal length. I'd be surprised if anyone has one sitting around, quite apart from the necessary 63-57 adapters it is very expensive. 

 

If anyone stumbles across a non-reducing flattener that does work do let us know. 

I’ll be testing a Hotech SCA flattener this weekend. Will share my results here. 



#133 chongo228

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Posted 25 July 2020 - 12:15 PM

Thanks chongo228. So we all seem to be happy with the supplied reducer but none of us have had any luck so far with any other kit. I got nowhere with the large Riccardi FF or FR and chongo228 had no luck with the small reducer. I've tried the Altair FF designed for their 360mm doublet and that got closer but the star shapes were poor even at APS-C. If anyone has the William Optics Flat 61 that might be interesting to try - it has some adjustment. Likewise for the Borg adjustable one, which has the tantalising feature that it looks like it extends into the focus tube and is adjustable for focal length. I'd be surprised if anyone has one sitting around, quite apart from the necessary 63-57 adapters it is very expensive. 

 

If anyone stumbles across a non-reducing flattener that does work do let us know. 

I'm going back to the Sharpstar reducer. I had the Riccardi already from my other scope so it was easy to try. I was just trying to be greedy and get down to F4.1. My 92mm is at 4.1 so I get a lot of signal but focus is harder to find and I have to do it often as temps fall. It's almost more trouble than it's worth sometimes to push it to really fast speeds sometimes. I wanted the wider FOV more than anything from the .75 reducer.



#134 OldManSky

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Posted 25 July 2020 - 12:15 PM

That image with the 30mm 2" eyepiece, nearly as big around as the scope, is priceless :)

Congrats on the new arrival.  I'm sure you'll love it as much as I do mine!



#135 gionk

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Posted 12 August 2020 - 04:13 PM

I have bought this scope about 2 month ago. Just before the 61EDPH II came out :-) I'm usually lucky with timing like this...

 

Can anyone with the 61EDPH II provide some test results on longitudinal chromatic aberration? I was using the scope for narrowband on my mono cameras (ASI1600MM and ASI183MM) and I really liked the results. However, I now wanted to use it with my ASI533MC for some casual portable imaging and I was a bit shocked from the longitudinal chromatic error of the scope. I would expect a bit better from a scope that claims to be an APO with correction up to 44mm image circle. I also tested with my Z6 and noticed similar issues on-axis, however, due to larger pixel size, the aberration is not as prominent as with the ASI533MC. Maybe that's the reason you can't find an official longitudinal aberration plot from the scope? :-)

 

Basically the scope is not usable at all for OSC or DSLR with pixel sizes below 6um I would say. Can someone with a 61EDPH II maybe repeat my test?

 

Here are my test results:

 

Single 120 seconds shot Ha with ASI183MM and it's tiny 2.9um pixels. Pretty okay result:

single frame 120 ASI183MM
 
Stacked random patch of the sky with Z6:
star adventurer ts61apo 30sec unguided

 

Longitudinal Aberration with Nikon Z6 fullframe and 6um pixels:

longitudinal Ca Z6
 
Longitudinal Aberration with ASI533 small 1" diagonal square sensor and moderate 3.76um pixels:
longitudinal Ca asi533mc

 

Compared to the fantastic CA correction of the Redcat Petzval, this scope is a horror show lol.gif Would really love to see if that's also the case with the EDPH II.

 

Just from looking at the defocused stars I guess the secondary spectrum of the 61EDPH is more than 0.1mm (I'm measuring defocus diameter of roughly 8px and calculate focal point distance = (diameter * pixelsize * focal ratio) / 1000) which is too much for an f4.5 scope I believe (I just recently stared to look into optics, so please don't take my interpretation for granted). The William Optics Star61 has around 0.04mm at f4.9. The Redcat maybe 0.05mm at f4.9. It's always hard how deep red you need to go (at least I have no clue). I have used ~620nm as red in my estimations.

 

Cheers

Gion


Edited by gionk, 12 August 2020 - 06:35 PM.


#136 gionk

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Posted 12 August 2020 - 04:18 PM

I mean... If I can see the Airy Disk in the Red channel while Blue is perfectly focused, at a moderate 3.76um Pixel size, would you really call yourself an APO refractor? lol.gif I think that's not okay. I bought actually the TS version and their technical support thinks that this is to be expected for the price and also they tell me that the image circle should be much larger for longitudinal CA to be corrected better... I'm still learning about optics, but I have this bad guts feeling about those statements. Why would on-axis aberration correction have something to do with corrected image circle? confused1.gif


Edited by gionk, 12 August 2020 - 04:19 PM.


#137 UKalwayscloudy

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Posted 13 August 2020 - 02:03 PM

Interesting observations on the doublet. The shots I’ve taken now I’ve got used to the mark II triplet had some mild CA on my Z6 that was pretty much eliminated by the CA tools in Lightroom. That was with the rather brutal Altair Quadband filter that emphasises RB differences in focusing, and which had been hard to fix on my camera lenses. So present but easily correctable at the 6 micron level. I’ll find a photo and post it later. As it happens I have just received the Altair Hypercam 269c which has 3.3 micron pixels and I will try it with the same Quadband filter on the triplet. The weather looks rubbish for the next ten days so don’t hold your breath. I’m also new to using a dedicated astrocam.

#138 Cometeer

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Posted 13 August 2020 - 02:50 PM

I tried Hotech SCA 1x Field Flattener, but it wast a good match for the scope even with a 4/3” sensor. I believe it’s identical to some of the Orion, Astro-tech, etc field flatteners

 

Another one to cross off the list. 



#139 gionk

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Posted 13 August 2020 - 03:34 PM

Interesting observations on the doublet. The shots I’ve taken now I’ve got used to the mark II triplet had some mild CA on my Z6 that was pretty much eliminated by the CA tools in Lightroom. That was with the rather brutal Altair Quadband filter that emphasises RB differences in focusing, and which had been hard to fix on my camera lenses. So present but easily correctable at the 6 micron level. I’ll find a photo and post it later. As it happens I have just received the Altair Hypercam 269c which has 3.3 micron pixels and I will try it with the same Quadband filter on the triplet. The weather looks rubbish for the next ten days so don’t hold your breath. I’m also new to using a dedicated astrocam.


Cool! Can you also try a broadband single sub? That would be directly comparable to my broadband shot.

#140 kel123

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Posted 13 August 2020 - 05:31 PM

I mean... If I can see the Airy Disk in the Red channel while Blue is perfectly focused, at a moderate 3.76um Pixel size, would you really call yourself an APO refractor? lol.gif I think that's not okay. I bought actually the TS version and their technical support thinks that this is to be expected for the price and also they tell me that the image circle should be much larger for longitudinal CA to be corrected better... I'm still learning about optics, but I have this bad guts feeling about those statements. Why would on-axis aberration correction have something to do with corrected image circle? confused1.gif


Not that I expect it to be perfect but I have not experienced anything close to your observations. This is also the first time I am reading about such issues.
Perhaps you got a bad copy or you need to reassess your imaging train. There might be something you are getting wrong.
At this focal length and price, there might be some funny looking stars at the corners and it should be expected. The answer will be to crop them out. This should be considered will framing objects.

#141 anat

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Posted 13 August 2020 - 09:46 PM

Gion

I am setting up my 61edph II and ASI533mc. Hope to get some results after a long period of cloudy skies. BTW, did you install an L (UV/IR cut) filter in your test?

Anat

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#142 gionk

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Posted 14 August 2020 - 03:20 PM

Gion

I am setting up my 61edph II and ASI533mc. Hope to get some results after a long period of cloudy skies. BTW, did you install an L (UV/IR cut) filter in your test?

Anat

Sent from my SM-N960F using Tapatalk

 

Wow, cool that would be a perfect comparison! Yes, sorry. My 61EDPH (doublet) and ASI533MC test shot was done using an Optolong l-pro LP filter which cuts UV and IR, so that shouldn't be the issue. Also accounted for the ~0.5mm additional optical path. I have also tested without a filter and 0.5mm distance ring and the result was the same except without UV / IR block, there were some halo like glows and other ugly optical artifacts but the more prominent main visual spectrum still showed the same longitudinal color blur.

 

Not that I expect it to be perfect but I have not experienced anything close to your observations. This is also the first time I am reading about such issues.
Perhaps you got a bad copy or you need to reassess your imaging train. There might be something you are getting wrong.
At this focal length and price, there might be some funny looking stars at the corners and it should be expected. The answer will be to crop them out. This should be considered will framing objects.

 

Which camera where you using and with what pixel size? I really carefully evaluated my distance to the corrector and also the field is really flat as you can see in my Ha shot or even the Z6 full-frame. Given the scope is otherwise nearly free from aberrations I don't suspect a bad build. Consider that this chromatic aberration is on-axis, so it's not the more commonly encountered lateral chromatic aberration which gets worse off-axis- Also longitudinal chromatic aberration is actually something every refractor scope has and is the secondary spectrum in achromats and tertiary spectrum in apochromatic systems. The term apochromatic is actually reserved for scopes which bring at least three wavelength to the same focal length. From my studies that's actually the choice of the designer which wavelength to bring to the same focus but usually is d, F and C Abbe numbers which more or less fall into green, blue and red. With faster optics the linear size of the diffraction limiting airy disk get's smaller but the aberration size does not change. I therefore expect that aberrations will probably be the limiting factor on such a fast telescope, however, I don't except a tertiary spectrum between 0.15 mm and 0.2 mm. (That's the focus blur diameter on the image translated to focus distance).



#143 anat

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Posted 14 August 2020 - 05:47 PM

Maybe it is worth shooting without the reducer to see the source of the issue. And did you combine the LRGB frames from your mono camera and find the same issue.

Anat

Edited by anat, 14 August 2020 - 05:53 PM.


#144 gnarayan

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Posted 21 August 2020 - 12:09 PM

Has anyone had a chance to try the Sharpstar 61 with the WO Flat61A field flattener, rather than the standard 0.8x reducer/flattener?



#145 byang

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Posted 21 August 2020 - 08:11 PM

Hi everyone, I am on the verge of ordering the AT60ED as a pure visual grab-n-go scope but wonder if I should up my budget to get the 61EDPH II instead.

 

I am sensitive to CA and a triplet should offer better colour correction than a doublet but would the addition of an extra glass actually result in a dimmer image (slightly maybe) considering that the small aperture may already limit the amount of light entering the scope in the first place?

 

Another consideration would be the weight, I would like a lighter scope that works well with a normal camera tripod for grab-and-go and travelling use and this makes me favour the AT60ED but at the back of my mind, I wonder if I should just "go all the way" and get the 61EDPH II triplet which should stop my itch to upgrade further as I do not have the budget to upgrade my scope often.



#146 OldManSky

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Posted 21 August 2020 - 08:17 PM

Hi everyone, I am on the verge of ordering the AT60ED as a pure visual grab-n-go scope but wonder if I should up my budget to get the 61EDPH II instead.

 

I am sensitive to CA and a triplet should offer better colour correction than a doublet but would the addition of an extra glass actually result in a dimmer image (slightly maybe) considering that the small aperture may already limit the amount of light entering the scope in the first place?

 

Another consideration would be the weight, I would like a lighter scope that works well with a normal camera tripod for grab-and-go and travelling use and this makes me favour the AT60ED but at the back of my mind, I wonder if I should just "go all the way" and get the 61EDPH II triplet which should stop my itch to upgrade further as I do not have the budget to upgrade my scope often.

I’ve had the WO ZS61 (essentially the same scope as the AT60ED) and have the Sharpstar triplet. I can confirm that the triplet has noticeably better visual (and imaging) color correction. The difference isn’t “omg” in your face, but it’s clearly noticeable. And while a third element will reduce light throughput by 1% or so, that’s not noticeable.  :)



#147 byang

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Posted 22 August 2020 - 08:01 AM

I’ve had the WO ZS61 (essentially the same scope as the AT60ED) and have the Sharpstar triplet. I can confirm that the triplet has noticeably better visual (and imaging) color correction. The difference isn’t “omg” in your face, but it’s clearly noticeable. And while a third element will reduce light throughput by 1% or so, that’s not noticeable.  smile.gif

Thank you for replying! Could you recall which astronomical objects were your observing for making the comparison?



#148 F.Meiresonne

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Posted 23 August 2020 - 03:17 AM

I mean... If I can see the Airy Disk in the Red channel while Blue is perfectly focused, at a moderate 3.76um Pixel size, would you really call yourself an APO refractor? lol.gif I think that's not okay. I bought actually the TS version and their technical support thinks that this is to be expected for the price and also they tell me that the image circle should be much larger for longitudinal CA to be corrected better... I'm still learning about optics, but I have this bad guts feeling about those statements. Why would on-axis aberration correction have something to do with corrected image circle? confused1.gif

Well, i guess they have replaced (rather soon) with a triplet , there must be some reason.And it comes at thesame price...

 

I have no complaints about it (doublet). Did not use it much sofar  but for my DSLR and the shots i take, i don't see much color it it..

See below a cropped image from the left under corner of a picture i took for test .I cannot see much color around any star.

So for my set up i think it will perform great. The cropped images  comes from a wide field with M35 and NGC 2158

 

Off course a space/red cat should perform better, these are Petzval designs...

Attached Thumbnails

  • M35_low_right.JPG

Edited by F.Meiresonne, 23 August 2020 - 03:21 AM.


#149 F.Meiresonne

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Posted 23 August 2020 - 03:19 AM

Full picture, resized to stay under the 500 kb limit

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  • M35_2 (Medium).jpg

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#150 gnarayan

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Posted 23 August 2020 - 08:27 PM

Not quite got the spacing right yet because even though I measure 37mm (+18 fr the A7s), the stars in the corners suggest it's too far. Enjoying the Sharpstar quite a bit nonetheless. I'm hoping there's a flattener that works well at the native focal length.
 
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