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Sharpstar 61 EDPH II APO Chromatic Abberation?

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#76 licho52

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Posted 26 February 2021 - 07:22 AM

Odd business this. Interesting to see FPL-51 stated for the Raptor. There is that more expensive version that TS-optics sells that is stated to be FPL-53, but it seems us owners of the Sharpstar-branded model (whether doublet or triplet) are not sure what we have. Might even be some variation as SS have not committed themselves. Their web site just says: "Objective type: Triplet air-spaced APO (One element of the lens is made from ultra-low dispersion ED glass)".

 

And then there is this statement on the Agena web site:  

 

"Please Note: In recent days, with the buzz around the Radian Raptor, we have received a few inquiries whether this scope uses FPL-53 glass or whether there are two optical versions of this scope in the market. Based on the information provided to us by Shapstar on Oct 3:

1) They use an ED element in this scope but they will NOT disclose what that glass type is.
2) Despite some speculation to the contrary in online forums, there is only ONE optical version of this scope worldwide. While some other international dealers state that this scope has an FPL-53 element, Sharpstar itself does not specify this."

 

Clear as mud. Not sure how to reconcile that information with user experiences. 

 

 

While I believe that this statement sort of sounds plausible, TS is clearly stating that the telescope has FPL53.  It would be completely misleading-downright lying to make that claim if Agena's statement is true.

 

I can only say that having purchased the TS version I don't see the level of CA in my pictures that is seen in this thread.  It's there (lets face it, it's f4.5!) but not huge and a very slight correction in Lightroom is all that's necessary to fix it, which makes it a non-issue to me.  It's either that my flattener spacing setup is more exact or maybe the filters being used introduce some false color.  Overall I am happy with the scope, 61mm has its limitations but it's good at large field pictures which it was designed for.

 

Out of the box the scope did suffer from significant pinched optics (and associated CA that was quite noticeable) in very low temperatures but I have loosened the retaining ring as is commonly advised for most TS telescopes out of the box. It was extremely tight and hard to dislodge.  Once it did the problem immediately became much less severe and now in warm weather it went away.

 

I don't know who is saying the truth, Agena or TS, either way it's a non-issue for me as the telescope performs as expected.  None of the vendors is impartial so they will both claim something that's commercially beneficial to them.  We can only judge the results.

 

(TLDR: if you have CA try to loosen the retaining ring, it caused pinched stars and worsened CA in my scope.)


Edited by licho52, 26 February 2021 - 07:41 AM.

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#77 TareqPhoto

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Posted 26 February 2021 - 11:20 AM

While I believe that this statement sort of sounds plausible, TS is clearly stating that the telescope has FPL53.  It would be completely misleading-downright lying to make that claim if Agena's statement is true.

 

I can only say that having purchased the TS version I don't see the level of CA in my pictures that is seen in this thread.  It's there (lets face it, it's f4.5!) but not huge and a very slight correction in Lightroom is all that's necessary to fix it, which makes it a non-issue to me.  It's either that my flattener spacing setup is more exact or maybe the filters being used introduce some false color.  Overall I am happy with the scope, 61mm has its limitations but it's good at large field pictures which it was designed for.

 

Out of the box the scope did suffer from significant pinched optics (and associated CA that was quite noticeable) in very low temperatures but I have loosened the retaining ring as is commonly advised for most TS telescopes out of the box. It was extremely tight and hard to dislodge.  Once it did the problem immediately became much less severe and now in warm weather it went away.

 

I don't know who is saying the truth, Agena or TS, either way it's a non-issue for me as the telescope performs as expected.  None of the vendors is impartial so they will both claim something that's commercially beneficial to them.  We can only judge the results.

 

(TLDR: if you have CA try to loosen the retaining ring, it caused pinched stars and worsened CA in my scope.)

My only solution with this telescope if i will buy it will be that i only using narrowbanding filters with it, or only one filter from LRGB set mainly green anyway, this scope will never been used alone in my imaging train/setup, it will be part of a dual or trio setup, so it will be next to a triplet or quad or quinto anyway, and in that case i don't need to use full RGB filters or OSC with it either using a reducer or without, problem solved to me, the price of the scope is also good, cheap.



#78 F.Meiresonne

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Posted 13 March 2021 - 06:17 AM

This is very helpful thread, I purchased the sharpstar EDPH II last week and coincidentally my first light image was also of M45.

Although the stars were nice and round into the corners of the frame I was very disappointed to see large amounts of blu/purple fringing on the brightest stars, considering I purchased specifically as it is a triplet. I was Using an Idas LP2 filter which has built in UV/IR cut & also tried a standard Baader UV/IR filter. some form of UV?ir filter is a must with all refractors, but neither of these seemed to help

On further test tonight I decided to remove the reducer and found the fringing was almost completely absent and quite satisfactory, put the reducer back on and the fringing was back.Ive just sent Sharpstar a FB message, they normally have replied to me the same day in the past.

I wonder if they upgraded the reducer at same time as they switched the scope from goblet to Triplet, or if its the same one used for both. it arrived in a separate box so its possible our reducer came from older batch than the scope?

Ive found a work around solution is to image through an Astronomik CLS ccd filter which has  a very strong blue cut built in ( it blocks all blue light below 450nm) I consider this a hack though as I used to use that with cheap doublets, didn't expect to need it with a triplet.

Here are some example images.

looks definitely CA to me..and that is with the EDPH Mark II...?

 

Then the mark I (doublet) just give better results....can't understand. Somewhere, something is not right...


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#79 TareqPhoto

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Posted 13 March 2021 - 06:39 AM

looks definitely CA to me..and that is with the EDPH Mark II...?

 

Then the mark I (doublet) just give better results....can't understand. Somewhere, something is not right...

From what i read, it is from the reducer, because it is an old version, it was designed for the doublet actually, so they didn't make another one newer to match the triplet, i really wanted to see if someone can try another third party reducer that is more designed for a triplet from another manufacturer to see if it is still an issue.



#80 F.Meiresonne

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Posted 13 March 2021 - 03:43 PM

From what i read, it is from the reducer, because it is an old version, it was designed for the doublet actually, so they didn't make another one newer to match the triplet, i really wanted to see if someone can try another third party reducer that is more designed for a triplet from another manufacturer to see if it is still an issue.

boy, oh boy....

 

Why could they not stick to the doublet then...it is fine...



#81 TareqPhoto

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Posted 13 March 2021 - 04:35 PM

boy, oh boy....

 

Why could they not stick to the doublet then...it is fine...

And that is why i moved my interest from this Sharpstar 61EDPH II to Sharpstar FRA400 and its reducer, sounds this is better option, later one day if they will make a better reducer for this 61 then i will buy it to have more gear/setup to play with.



#82 cpviolation

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Posted 14 March 2021 - 10:55 AM

While I believe that this statement sort of sounds plausible, TS is clearly stating that the telescope has FPL53.  It would be completely misleading-downright lying to make that claim if Agena's statement is true.

 

I can only say that having purchased the TS version I don't see the level of CA in my pictures that is seen in this thread.  It's there (lets face it, it's f4.5!) but not huge and a very slight correction in Lightroom is all that's necessary to fix it, which makes it a non-issue to me.  It's either that my flattener spacing setup is more exact or maybe the filters being used introduce some false color.  Overall I am happy with the scope, 61mm has its limitations but it's good at large field pictures which it was designed for.

 

Out of the box the scope did suffer from significant pinched optics (and associated CA that was quite noticeable) in very low temperatures but I have loosened the retaining ring as is commonly advised for most TS telescopes out of the box. It was extremely tight and hard to dislodge.  Once it did the problem immediately became much less severe and now in warm weather it went away.

 

I don't know who is saying the truth, Agena or TS, either way it's a non-issue for me as the telescope performs as expected.  None of the vendors is impartial so they will both claim something that's commercially beneficial to them.  We can only judge the results.

 

(TLDR: if you have CA try to loosen the retaining ring, it caused pinched stars and worsened CA in my scope.)

Hey!! Please please let me know, what is the retaining ring, and how do I adjust this to trouleshoot whether this is contributing to some of the issues I have. I emailed TS Optics and they stated there is no manual and no documentation for the 61 EDPH II. Here is something from AgenaAstro but there is no indication of a retaining ring in the document that I can find


thanks for your time!


Link to AgenaAstro "manual" https://agenaastro.c...oad/link/id/79/

 



#83 licho52

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Posted 14 March 2021 - 05:57 PM

I just followed this video: https://www.youtube....h?v=Sj_IyhRspTM



#84 DRK73

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Posted 17 March 2021 - 09:58 AM

And that is why i moved my interest from this Sharpstar 61EDPH II to Sharpstar FRA400 and its reducer, sounds this is better option, later one day if they will make a better reducer for this 61 then i will buy it to have more gear/setup to play with.

Following this thread because I've been looking for something in the 300mm focal length range - but have been using a FRA400 for several months now. 

 

First, there is a dedicated thread for this scope here in the "refractors" forum. 

 

Secondly, the scope without the reducer is very good. The glass is not fpl-53 but neither is the glass in my AT115EDT and both have excellent color correction (I use the FRA400 with a OSC and have been very happy with it). 

 

I *did* originally buy it with the 0.7x reducer, but sent the reducer back as it was clear that with the reducer red, green, and blue were not coming to focus together. Even without pixel-peeping, I decided it was unusable unless one was doing strictly narrowband imaging. 


Edited by DRK73, 17 March 2021 - 09:59 AM.


#85 TareqPhoto

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Posted 17 March 2021 - 02:45 PM

Following this thread because I've been looking for something in the 300mm focal length range - but have been using a FRA400 for several months now. 

 

First, there is a dedicated thread for this scope here in the "refractors" forum. 

 

Secondly, the scope without the reducer is very good. The glass is not fpl-53 but neither is the glass in my AT115EDT and both have excellent color correction (I use the FRA400 with a OSC and have been very happy with it). 

 

I *did* originally buy it with the 0.7x reducer, but sent the reducer back as it was clear that with the reducer red, green, and blue were not coming to focus together. Even without pixel-peeping, I decided it was unusable unless one was doing strictly narrowband imaging. 

Honestly speaking, if i will buy that FRA400 and maybe add this Sharpstar 61 to the collection all with reducer only to use Nb filters or Lum, for RGB or OSC i will be using my APO triplet FPL-55, but only if i want to go very wide to ~300mm range, and i must buy that Starizona APEX 0.65x to use with 90mm F/6 FPL-55 and buy APS-C, this way i can use FRA400 and 61EDPHII both reducers without issues.
 



#86 UKalwayscloudy

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Posted 20 March 2021 - 05:51 AM

I do not have CA problems with the Altair Variable 1.0 flattener either, on my Mark II. Or at least nothing that can't be dealt with by a small nudge in LR.  It's good to APS-C size, just need to push the BF up as far as you can while maintaining infinity focus. Can't help wondering if SS are shipping these with more than one type of glass, unless you get the TS version which is also sold by Altair here in UK. 



#87 AlienRatDog

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Posted 20 March 2021 - 07:18 AM

I did not notice such fringing when I had the Apertura 69EDR w/ field flattener...it’s half the price (a bit slower at f/6 however)

#88 licho52

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Posted 21 March 2021 - 11:08 AM

Let me just state that 6 to 4.5 is not "a bit"

 

It's not in the same universe.



#89 Barologuy

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Posted 21 March 2021 - 06:58 PM

So, CA is still present with my scope at this point I'm just going to live with it but I figured I'd give people here some closure. It's really not horrible CA and it's mostly correctible in post.

That said I'd agree with what people say here that for the price of this it's almost worth it to pick up a nice doublet like the AT102ED or move down in Focal length to a RedCat petzval. I don't regret the purchase, I've made some beautiful images. If someone asked for my advice though, it would be " You get what you pay for, don't cheap out on optics, but get a focal length that makes sense for a variety of objects. " If I could go back in time I'd definitely move towards a more reknowned producer of refractors. Just my own opinion. You really do get what you pay for in this hobby, and I wish I had gotten something for deeper space. The thing is though, now I have an excuse to buy a larger, higher quality telescope and maybe a mount to hold it.. It's a win-win for me.

Cheesy but for those interested in optics the SharpStar gives you a taste of what's possible on a budget, so you can decide if you want to do more down the road. You can get that from a lot of scopes though, so I think marketing this as an apo is highly misleading, and we just need to establish as a community that "apo" as a light measurement should be standardized to some sort of deviation from universally considered to be "quality apo" scopes, and I think manufacturers need to take the time to provide individual spot diagrams on scopes if they want to command this higher price.

That's all I think. I'm not upset, it's just not standardized. As it stands I could market a triplet as APO if, "it tried to correct something". Sure feedback will comeback from the community, but it does nothing to talk about glass used when its more about light correction anyway. Give us spot diagrams for each individual scope and let the consumer decide if they want to send it back or not.
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#90 F.Meiresonne

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Posted 22 March 2021 - 06:49 AM

APO has become a very 'gray' definition imo.

 

In the 'old' days you had achromats with flint and crown glass, and apo chromats will  3 ,4 or even more lenses.

 

Nowadays you have doublets made of exotics types of glass , difficult sometimes to make out how much APO it is.

 

Now this is not a bad thing but with so much different type of glass around  it has become hard to define how much 'APO appeal' a scopes has. 

 

I have a TS 102 mm FPL-53 doublet. which is called also APO. If it is , I doubt it , but it seems so nicely controlled that is has become  a non issue , or not noticable even for  AP.

 

I still have a hard time to believe it but the pictures I take with it are just great and no obvious CA is seen. And that goes for my 61 EDPH Mark 1 too,


Edited by F.Meiresonne, 22 March 2021 - 06:52 AM.

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#91 Barologuy

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Posted 01 April 2021 - 03:24 PM

Weird question but how are you guys installing filters in this OTA if you're using a DSLR? Just realized my only possible place to screw in a filter are on the "48mm baffles" inside the camera side of the reducer itself.

Edited by Barologuy, 01 April 2021 - 03:25 PM.


#92 Petripher

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Posted 01 April 2021 - 08:35 PM

"...how are you guys installing filters in this OTA if you're using a DSLR?"

 

A solution is to use a filter mounted inside a "plate" that take place inside the DSLR body, like this: https://www.astronom...tml?___store=en



#93 F.Meiresonne

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Posted 07 April 2021 - 03:05 PM

Weird question but how are you guys installing filters in this OTA if you're using a DSLR? Just realized my only possible place to screw in a filter are on the "48mm baffles" inside the camera side of the reducer itself.

I don't understand the question.

 

The filter  2 inch screws in the FF/FR, why should this be a problem for a DSLR? It is however difficult to reach in theFF/FR of the  61 EDPH, it is much easier in the 76 EDPH.

 

No real need for clip in filters in this case....

 

PS : the FF/FR is  a 2 piece thing, you  can screw them apart...


Edited by F.Meiresonne, 07 April 2021 - 03:09 PM.

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#94 UKalwayscloudy

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Posted 07 April 2021 - 04:37 PM

Indeed, I've taken off the end of the reducer and have put in the Badder UFC gear coming off the thread in the middle of the reducer. So I have easy filter slide tray. 



#95 Barologuy

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Posted 07 April 2021 - 05:01 PM

Indeed, I've taken off the end of the reducer and have put in the Badder UFC gear coming off the thread in the middle of the reducer. So I have easy filter slide tray.

ah, ok

#96 Barologuy

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Posted 07 April 2021 - 05:02 PM

I don't understand the question.

The filter 2 inch screws in the FF/FR, why should this be a problem for a DSLR? It is however difficult to reach in theFF/FR of the 61 EDPH, it is much easier in the 76 EDPH.

No real need for clip in filters in this case....

PS : the FF/FR is a 2 piece thing, you can screw them apart...



Yeah I figured it out, sorry I didn't reply here. I just wasn't sure if that was a thread or not since it was a bit of a stretch to put in for someone with bratwurst fingers like myself.

#97 cedric_d

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Posted 08 April 2021 - 02:09 AM

I have very similar blue halos around stars with my Sharpstar 94EDPH :

https://www.cloudyni...orrection-issue

 

I emailed Sharpstar but received no answer for the moment.



#98 TareqPhoto

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Posted 08 April 2021 - 07:21 AM

I have very similar blue halos around stars with my Sharpstar 94EDPH :

https://www.cloudyni...orrection-issue

 

I emailed Sharpstar but received no answer for the moment.

I remember in another thread talking about Sharpstar 61 II that they have seeing that halo or CA whatever only when using the Sharpstar reducer, i read that it is the old version of reducer for the doublet scope, and they didn't see that halo or CA without the reducer, so could that be from the reducer itself?



#99 cedric_d

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Posted 08 April 2021 - 08:40 AM

I remember in another thread talking about Sharpstar 61 II that they have seeing that halo or CA whatever only when using the Sharpstar reducer, i read that it is the old version of reducer for the doublet scope, and they didn't see that halo or CA without the reducer, so could that be from the reducer itself?

I didn't test the scope without the reducer, but i'am using the more recent model that is dedicated to 94EDPH :

http://www.sharpstar...erface/346.html


Edited by cedric_d, 08 April 2021 - 10:59 AM.


#100 TareqPhoto

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Posted 08 April 2021 - 02:04 PM

I didn't test the scope without the reducer, but i'am using the more recent model that is dedicated to 94EDPH :

http://www.sharpstar...erface/346.html

I see, and the reducer is a quadruplet design which should be good enough, so i really don't know how that halo is there with the scope and reducer, i will point it last to the filters then no matter if it is a mono camera being used or the color.




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