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Badder Fringe Killer vs. 495 Long-Pass Comparison

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#26 Jon_Doh

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Posted 11 August 2014 - 09:15 AM

Is there any filter for reducing c/a that does not turn the subject object yellow?

 

steve

Yes.  Stack a Moon & Skyglow with the Fringe filter and it will reduce the CA and pretty much give you true color.  Stacking these filters will not give you as much light loss as using the Semi APO filter as that filter combines the Fringe with the equivalent of stacking two Moon and Skyglow filters.



#27 astroneil

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Posted 11 August 2014 - 10:37 AM

Steve,

 

I would recommend you take a look at the transmission curves for the Baader filters posted on the Agena website.   Restoring a neutral color is achieved by taking significant cuts to the visible part of the spectrum that an achromat does focus.  The FK leaves the 500-680nm wavelengths alone for the most part.  So doesn't the 495 Longpass.  The only way to remove the <500nm defocused light and maintain color neutrality is to also remove light that is normally focused by the achromat.  That will lead to some dimming of the image.  The reason I recommend the 495 LP for a large achromat is that it completely eliminates CA while keeping the 500-700nm wavelengths at 95% or better transmission rate.  If you really can't take the color shift then a #8 light yellow will cut the same amount of CA as the Baader Fringe Killer ~50%.

 

Incidentally, when I tested these filters on the Moon with my Vixen 140 NA, the moon was lavender colored without the filter - not just purple fringed, but lavender across the surface.  The #8 restores a white appearance to the Moon's color.  So depending upon your scope and eyes you might find a light yellow filter does give a reasonably neutral color.  

 

If your eyes are so sensitive to the color shift that you cannot adapt then you might want to consider an APO or the light loss that goes with the semi-APO filter.  But I think the color shift may be one of these things that people run away from before they have really given themselves a chance.  I rarely notice the color shift of the 495 LP filter for DSO unless the stars are really bright in which case the are a beautiful golden color like Capella.

 

Dave

Hi Dave :bow: :bow: :bow:

 

I have much work to do this autumn evaluating the effects of the Fringe Killer on Gaius, my choice little ST-80. I wonder whether it might even allow you to see fainter objects than without it. Have you conducted any work along these lines?

 

Regards,

 

Neil. ;)



#28 Kon Dealer

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Posted 11 August 2014 - 09:14 PM

I have the semi apo and the #8 filter. 

Having compared the two i can confidently say the semi apo does close to sweet FA, except dim the view.

the #8 cuts out CA very effectively and only imparts a slight yellow tint.

much cheaper too. The semi apo is rubbish.



#29 russell23

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Posted 11 August 2014 - 09:34 PM

 

Steve,

 

I would recommend you take a look at the transmission curves for the Baader filters posted on the Agena website.   Restoring a neutral color is achieved by taking significant cuts to the visible part of the spectrum that an achromat does focus.  The FK leaves the 500-680nm wavelengths alone for the most part.  So doesn't the 495 Longpass.  The only way to remove the <500nm defocused light and maintain color neutrality is to also remove light that is normally focused by the achromat.  That will lead to some dimming of the image.  The reason I recommend the 495 LP for a large achromat is that it completely eliminates CA while keeping the 500-700nm wavelengths at 95% or better transmission rate.  If you really can't take the color shift then a #8 light yellow will cut the same amount of CA as the Baader Fringe Killer ~50%.

 

Incidentally, when I tested these filters on the Moon with my Vixen 140 NA, the moon was lavender colored without the filter - not just purple fringed, but lavender across the surface.  The #8 restores a white appearance to the Moon's color.  So depending upon your scope and eyes you might find a light yellow filter does give a reasonably neutral color.  

 

If your eyes are so sensitive to the color shift that you cannot adapt then you might want to consider an APO or the light loss that goes with the semi-APO filter.  But I think the color shift may be one of these things that people run away from before they have really given themselves a chance.  I rarely notice the color shift of the 495 LP filter for DSO unless the stars are really bright in which case the are a beautiful golden color like Capella.

 

Dave

Hi Dave :bow: :bow: :bow:

 

I have much work to do this autumn evaluating the effects of the Fringe Killer on Gaius, my choice little ST-80. I wonder whether it might even allow you to see fainter objects than without it. Have you conducted any work along these lines?

 

Regards,

 

Neil. ;)

 

 

Neil,

 

I have not checked with the ST80 yet - too few chances due to weather this summer.  With the Vixen 140 there is absolutely an increased ability to see fainter stars because the smearing effects of CA is removed with the filter allowing pinpoint sharp focus to be achieved.  I've seen this with clusters and faint companion stars.  I also think nebula show a bit more detail with the filter.  The 495 Longpass is most effective in producing these improvements.  

 

People might object that you should not be able to see fainter stars with the filter.  But the CA makes it difficult to get sharp focus and so the faintest stars are smeared out of view.  Remove the CA, sharp focus is easier to attain and those faint stars that could not be seen before pop into view.

 

It really is that simple.

 

Dave


Edited by russell23, 11 August 2014 - 09:35 PM.


#30 astroneil

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Posted 13 August 2014 - 06:33 AM

Hi Dave,

 

I suspect that is the case.  The filter seemed to help in the summer twilight at my location, by darkening the sky and reducing the rather large, unfocused halo around bright stars seen at the higher powers. But it should be fairly easy to establish whether such filters permanently affixed to the diagonal (out of sight and out of mind) will allow you to probe that little bit deeper into the mysteries of Creation.

 

Best wishes,

 

Neil. ;)



#31 saemark30

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Posted 13 August 2014 - 03:25 PM

So the #8 is a weaker filter than the 495. Will it also not reduce t he brightness of deep sky objects as much as the 495?

I have a 6" f/8 achromat.



#32 russell23

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Posted 13 August 2014 - 07:33 PM

So the #8 is a weaker filter than the 495. Will it also not reduce t he brightness of deep sky objects as much as the 495?

I have a 6" f/8 achromat.

 

The 495 Longpass filter transmits 95+ % of the light from 500-700nm.  It cuts most of the light from 400-490nm.  With a 6" F/8 achromat a significant portion of that light is not focused and therefore not contributing to the brightness of the image anyway.  So there is not really that much dimming from these filters.  There is some.  But what I've found is that I can see more of the DSO with the filter than without.  For example, M27 shows more structure even if it is very slightly dimmed.  Globular clusters show a lot more detail because it is possible to get pinpoint sharp star images.  I've noted faint companion stars when I use the 495 Longpass filter that I had not noticed before.  

 

I also think a lot of the "dimming" that comes with these filters is actually just defocused light being removed. 

 

Dave



#33 De Lorme

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Posted 13 August 2014 - 10:47 PM

Dave you are so right!

 

The Baader Longpass has been the best{and cheapest} improvement I've done to the CR6".  

 

De Lorme



#34 russell23

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Posted 14 August 2014 - 11:07 AM

Dave you are so right!

 

The Baader Longpass has been the best{and cheapest} improvement I've done to the CR6".  

 

De Lorme

 

I would love to hear what the folks with the IStar 8" F/6 would find if they would give the 495 Longpass a shot.  People worry about a little bit of lost light and color shift ... But there is a gain.  Without the filter I would not want to go above 80x with my Vixen 140.  With the filter I've gone to 200x on bright globs and over 300x on the Moon when seeing allows.  So I don't have to think of my Vixen 140 as just a low power scope with the filter. I see more with the filter - not less.

 

Dave



#35 krakatoa1883

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Posted 14 August 2014 - 01:31 PM

I do not agree with those who are saying that the SemiApo is rubbish, the results that can be obtained with this filter actually depend on the subject. I made a test on several Baader filters (it can be read here, sorry it is not in English) and I found the SemiApo very effective in observing, for example, Jupiter as it does not sacrifice blue details while the 495 LP wash them out almost completely. With large and fast achromats with lot of CA the 495 may be preferable but with a well corrected achromat the view through the SemiApo is definitevely more pleasant and contrast is very good. With these instruments there is no need to paint the Moon in yellow.

 

Raf



#36 russell23

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Posted 14 August 2014 - 06:06 PM

I do not agree with those who are saying that the SemiApo is rubbish, the results that can be obtained with this filter actually depend on the subject. I made a test on several Baader filters (it can be read here, sorry it is not in English) and I found the SemiApo very effective in observing, for example, Jupiter as it does not sacrifice blue details while the 495 LP wash them out almost completely. With large and fast achromats with lot of CA the 495 may be preferable but with a well corrected achromat the view through the SemiApo is definitevely more pleasant and contrast is very good. With these instruments there is no need to paint the Moon in yellow.

 

Raf

 

Hi Raf,

 

I would not say the Semi-APO filter is rubbish, but I think for people that haven't tried these filters the name "semi-apo" is misleading and result in people buying the semi-apo filter when another filter choice might be more appropriate.  I have compared the #8 light yellow, Fringe Killer, #12 deep yellow, and 495 Longpass directly and at an earlier time tried the semi-apo filter. 

 

For a long time I had the Baader Fringe Killer mounted permanently on my star diagonal.   With my Vixen 140NA refractor the Fringe Killer removed ~50-60% of the visible CA.  With a 107mm aperture mask I was able to get lunar views that were essentially CA free.  Then after reading debates about the various filters on this forum I decided to do a direct comparison of the 4 filters listed above. 

 

Keep in mind that the semi-apo filter is the Fringe Killer (which is identical in performance to a #8 light yellow filter) combined with the Baader M&SG filter.  So the semi-apo does no better at removing CA than the FK: about 50-60%.  All it does is restore color neutrality --- by removing additional light from the spectrum that is actually focused by the achromat.  This is readily seen if you look at the transmission curves on the Agenaastro website.   So maybe the semi-apo is the filter a person will prefer, but it should not be assumed that because it is more color neutral than the #8 and FK and because it has the "-apo" in the name that it is the best option.  As you point out - it will depend upon observing targets ... and IMO also the scope. 

 

The advantage the 495 Longpass filter has over all the others for certain observing goals is that it offers complete removal of purple CA.  I was very happy with the FK for a long time, but when I compared the FK to the 495 Longpass the positive effects of the filtration was taken to a higher level.   With the FK I was able to push my Vixen 140 to ~160x for bright globs and ~200-225x on the Moon.  With the 495 Longpass I have pushed the Vixen 140 to 200x on bright globs and over 300x on the Moon.  Views are sharper and cleaner when I use the 495 LP than with the FK.  There is a mild amount of additional dimming but it is made up for by the increased ability to detect fine details and faint stars - and I can use my Vixen 140mm refractor at full aperture instead of using the 107mm aperture mask. 

 

These days I recommend the #8 light yellow over the FK because it is just as effective.  For 100mm and smaller achromats the #8 light yellow should be sufficient.   For 127mm and larger achromats the 495 LP is the way to go in my opinion.

 

The only issue is whether or not you can deal with the color shift of the 495 LP - which is only seen on the Moon, planets, and bright stars.   But isn't that what color filters are for anyway - to enhance details on the Moon and planets?  Use #56 for this, #80A for that,  #15 or 21 for ... and so on.    In comparison to the unfiltered view you get with an achromat the yellow CA free view with the 495 LP is much preferable to me.  If it is not satisfactory to an individual then that person should go with the semi-apo filter or just get an APO refractor. 

 

Dave



#37 saemark30

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Posted 14 August 2014 - 06:22 PM

Are you folks using the 1.25" filters or 2" ones? There is a big savings with the former and for high power I would only need the 1.25".

For imaging I would use a 2" but for the 2" eyepieces I hardly think any CA filtering is needed.



#38 Kon Dealer

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Posted 14 August 2014 - 08:54 PM

I would like to repeat that my observation of the semi-APO is that it does near to nothing when it comes to removing CA.

I have checked it with a spectrophotometer - which agrees with my visual observations.

In brief the semi-APO is rubbish.



#39 krakatoa1883

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Posted 15 August 2014 - 11:51 AM

 As you point out - it will depend upon observing targets ... and IMO also the scope. 

 

agreed, and personal taste also. Of course if the goal is to completely remove CA in a fast refractor the 495 LP is far more effective than the SemiApo, however this happens at the expense of the shorter wavelengths as one can see by comparing the spectra of both filters. These colours can still be seen in a well corrected achromat for which the FK (or the SemiApo) make more sense, IMO.

 

I also agree that the term "SemiApo" is really misleading.

 

Rgds

 

Raf

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#40 jrbarnett

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Posted 17 August 2014 - 11:11 AM

Are you folks using the 1.25" filters or 2" ones? There is a big savings with the former and for high power I would only need the 1.25".

For imaging I would use a 2" but for the 2" eyepieces I hardly think any CA filtering is needed.

It has more to do with convenience, I think.  The goal is to make a scope that is decidedly not optimal for higher magnification targets, adequate.  Rather than swapping a single 1.25" filter among multiple shorter focal length eyepieces, or buying multiple 1.25" filters and installing them on all shorter focal length eyepieces, a single 2" unit installed in the nosepiece of the diagonal is more efficient.  If you plan on using the scope for what it does best - low power, wide fields panning - you have but a single filter to remove.

 

- Jim



#41 russell23

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Posted 18 August 2014 - 11:04 AM

 

 As you point out - it will depend upon observing targets ... and IMO also the scope. 

 

agreed, and personal taste also. Of course if the goal is to completely remove CA in a fast refractor the 495 LP is far more effective than the SemiApo, however this happens at the expense of the shorter wavelengths as one can see by comparing the spectra of both filters. These colours can still be seen in a well corrected achromat for which the FK (or the SemiApo) make more sense, IMO.

 

I also agree that the term "SemiApo" is really misleading.

 

Rgds

 

Raf

 

 

Hi Raf,

 

It is an interesting tradeoff.  It is true that the 495 Longpass eliminates most of the blue violet - but that is why it is so effective at eliminating CA.  If you look at the images you posted you can see some other things worth considering.  Notice that between 515 and 540 nm there is significant dimming of the green light with the semi-APO whereas the 495 Longpass leaves it untouched.  And then from 570-600 nm the semi-APO completely eliminates the light whereas the 495 Lonpgass again leaves those wavelengths untouched.   So it is a definite tradeoff.  With the semi-APO you gain light from 440-490nm but then you lose a lot in the 515-540nm range and all in the 570-600nm range.  So that is why I prefer the 495 Longpass because the wavelengths it removes are the wavelengths the achromat does a poor job of focusing whereas with the semi-APO the wavelengths the achromat does a poor job of focusing are not significantly removed and some wavelengths that the achromat does focus well are removed.

 

Dave



#42 aa6ww

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Posted 18 August 2014 - 02:58 PM

I think the value of these filters depends on what type of optics you are use to looking through and also what you own. If your only scope is an achromat, especially a fast one, then anythings should be an improvement on bright objects. The small additional cost of a filter is probably worth is for some.  If your use to looking through ED Glass or  triplet lens systems, a yellow moon for example looks just horrible, as bad as a dull washed out one with a green perimeter from no filtering. Still, for the price some people pay to try and improve their achromat, they can just sell what they have an purchase a used ED refractor or a nice reflector for roughly the same overall price or less.
 
A $299.00  8" Orion F/4.9 OTA reflector is my answer to a large filtered achromat refractor.
 
Yellow Moons, Green Stars, Pink Clovers belong in kids cereal, not in an eyepiece.
 
  Ralph in Sac
 
 

I think the semi-APO is rubbish.
I see no evidence of CA removal, just a general dimming of the view. :mad:
Now a light yellow filter kills any CA stone dead and only imparts a slight yellow cast- which you soon get used to.
Alot cheaper too :grin:


Edited by aa6ww, 19 August 2014 - 01:15 AM.


#43 russell23

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Posted 18 August 2014 - 05:15 PM

If you are used to looking through an APO then isn't this whole thread irrelevant anyway?  If you can afford a large APO then you don't need to worry about filtering an achromat.  You can get Achromats and APO's from 50mm to over 200mm.  Once your budget goes above $4000 you can get a large APO or a large achromat.  Below $4000 you have to make a choice - do you want an unfiltered CA free view with smaller aperture?  Or do you want a larger aperture that needs filtering to remove CA?  That becomes a genuine decision with a smaller budget.  For $1000 you can get a 152mm achromat or a 102mm APO.  The aperture difference is enough to make the achromat a worthy alternative.  

 

I'm leaving newts and cats out of this because some people just want refractors.  

 

Dave

 

 

 I think the value of these filters depends on what type of optics you are use to looking through and also what you own. If your only scope is an achromat, especially a fast one, then anythings should be an improvement on bright objects. The small additional cost of a filter is probably worth is for some.  If your use to looking through ED Glass or  triplet lens systems, a yellow moon for example looks just horrible, as bad as a dull washed out one with a green peremiter from no filtering. Still, for the price some people pay to try and improve their acrhomat, they can just sell what they have an purcase a used ED refractor or a nice reflector for roughly the same overall price or less.

 

A $299.00  8" Orion F/4.9 OTA reflector is my answer to a large filtered achromat refractor.

 

Yellow Moons, Green Stars, Pink Clovers belong in kids cereal, not in an eyepiece.

 

  Ralph in Sac

 

 

I think the semi-APO is rubbish.
I see no evidence of CA removal, just a general dimming of the view. :mad:
Now a light yellow filter kills any CA stone dead and only imparts a slight yellow cast- which you soon get used to.
Alot cheaper too :grin:

 



#44 azure1961p

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Posted 18 August 2014 - 10:59 PM

The conventional wisdom Ive  gathered is the long pass is superior on nixing violet fringing while the Baader FK is still very good and with a more natural color balance than the LP.  

 

Pete



#45 jrbarnett

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Posted 20 August 2014 - 06:30 PM

Any experiences with the Baader Contrast Booster at night?  The comparative images in the link below, albeit in daylight, make the contrast booster look pretty darned good, though maybe introducing a different set of color balance issues.

 

http://astro-foren.d...EMI-APO-Filter/

 

Regards,

 

Jim



#46 oldtimer

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Posted 23 August 2014 - 05:39 PM

An important point no one here is dicussing is the 'amount' of CA one is trying to subdue. It should be oblious that a 6" f-5 achro is going to produce much nore CA rhan a 4" f-10 achro. 

I have a 100mm F5 achro that I use a #8 yellow in as it needs a strong filter. My 90mm F8.8 gets by with a Lumicon MV which is a weak CA filter.



#47 SStoffer

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Posted 23 August 2014 - 11:18 PM

An important point no one here is dicussing is the 'amount' of CA one is trying to subdue. It should be oblious that a 6" f-5 achro is going to produce much nore CA rhan a 4" f-10 achro. 

I have a 100mm F5 achro that I use a #8 yellow in as it needs a strong filter. My 90mm F8.8 gets by with a Lumicon MV which is a weak CA filter.

 

What would you suggest for a ES AR102, F/6.5 refractor? I'm having an impossible time deciding between the 495 Longpass filter and the Fringe Killer.



#48 REC

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Posted 24 August 2014 - 08:32 AM

 

Is there any filter for reducing c/a that does not turn the subject object yellow?

 

steve

Yes.  Stack a Moon & Skyglow with the Fringe filter and it will reduce the CA and pretty much give you true color.  Stacking these filters will not give you as much light loss as using the Semi APO filter as that filter combines the Fringe with the equivalent of stacking two Moon and Skyglow filters.

 

This is a great post. I have been happy with the views of the Moon & Skyglow on my C102 and just oredered the Fringe Killer to stack together.  This should also be good for my old ST 80 as well.  Now all I need is some clear skies....lol








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