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Equipment Discussions >> Refractors

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russell23
Post Laureate
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Reged: 05/31/09

Loc: Upstate NY
CA Reduction filters
      #6113911 - 10/02/13 07:52 PM Attachment (165 downloads)

I have been using a Baader Fringe Killer for several years now with my Vixen 140 NA. Based upon discussions of the use of a #8 light yellow filter for CA reduction and a mention here of the Baader 495 long pass filter I decided to order a 2" Lumicon #8 light yellow and a 2" Baader 495 long pass filter. They are pictured below against a magazine page. Clockwise from top the are the Fringe Killer, Baader 495, and Lumicon #8.

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russell23
Post Laureate
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Reged: 05/31/09

Loc: Upstate NY
Re: CA Reduction filters new [Re: russell23]
      #6113913 - 10/02/13 07:53 PM Attachment (130 downloads)

Here they are against white index cards with same order as first post if you start on the right side and go counterclockwise:

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Mike4242
Pooh-Bah


Reged: 11/02/11

Loc: Memphis, TN
Re: CA Reduction filters new [Re: russell23]
      #6114027 - 10/02/13 08:56 PM

Like you, I've been a huge fan of the Baader Fringe Killer. That filter makes a very noticeable difference in contrast on almost every class of object. I'm very interested to hear how the other filters stack up against the Fringe Killer. I'll be anxiously awaiting your report.

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russell23
Post Laureate
*****

Reged: 05/31/09

Loc: Upstate NY
Re: CA Reduction filters new [Re: Mike4242]
      #6114385 - 10/03/13 12:07 AM

Quote:

Like you, I've been a huge fan of the Baader Fringe Killer. That filter makes a very noticeable difference in contrast on almost every class of object. I'm very interested to hear how the other filters stack up against the Fringe Killer. I'll be anxiously awaiting your report.




I just got in from several hours of testing these three filters and my new Agena 18mm dual ED. The first test of the filters was with the 18mm eyepiece and a 3x ES Barlow on Altair (128x). I started with no filter and Altair had a bright, beautiful, purple halo. I then panned west to a small group of fainter stars and found I was unable to get a pinpoint sharp focus of these stars.

With the Fringe Killer the halo around Altair was reduced about 50-60%. The color of Altair was a nice white and when I panned to the group of stars I was able to achieve a nice sharp focus. The 18mm ED has slight edge brightening which was reduced with the Fringe Killer. Sky background was blacker than without the filter and the field seemed "cleaner". All this is what I have always found with the FK.

The #8 light yellow Lumicon performed exactly like the Fringe Killer. Same reduction in CA, same white color or Altair, same increase in pinpoint sharpness of star images. The one thing I noticed was that the Lumicon filter is buttery smooth threading and unthreading whereas both Baader filters are hard to catch initially, then tighten easily, but then are very difficult to unthread. Big advantage to Lumicon here.

Next up was the Baader 495 long-pass filter. This filter cuts 100% of the light below 475nm and let's through over 95% at longer wavelengths. I was extremely impressed with this filter. Altair had zero purple/blue fringing and just a tiny bit of red fringe. Stars were razor sharp at 128x and the mild edge brightening of the 18mm eyepiece was almost completely gone. Altair was a beautiful golden yellow color indicating a strong but not unexpected color shift.

These results were repeated in detail with Vega at 89x.

I then went on to observe number of open clusters, globular clusters, and the nebula M17 and M27. There was no obvious dimming of nebulous light with any of these filters including the longpass. If anything, the increase in sharpness seemed to make fine structure easier to detect with the longpass. Partially resolved clusters such as ngc 6819 and M71were as clear and sharp as I have ever seen them with this scope. Star clusters and the Milky Way were striking with precisely rendered pinpoint sharp stars against a deep black sky.

The color shift with the long-pass filter was not noticeable except on very bright stars. Albireo was yellow-orange and white instead of the natural golden yellow and blue. Fainter stars appeared white.

In short, for deep sky the Baader 495 long-pass was the best filter and I really felt like I was getting the sharpness and contrast of a true APO. The Fringe Killer has never pushed the performance to that level. I just kept thinking "Wow" with that longpass filter!

What I will be interested to see next is how the longpass works with the Moon and Jupiter.

Dave


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Mike4242
Pooh-Bah


Reged: 11/02/11

Loc: Memphis, TN
Re: CA Reduction filters new [Re: russell23]
      #6114738 - 10/03/13 09:09 AM

Wow! Thanks for that report. Very interesting indeed. I have to admit, I didn't think the yellow #8 would be just as good as the Fringe Killer. The yellow #8 is definitely the most economical way to go. I might have to pick up one of those 495 long-pass filters myself.

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Jon_Doh
scholastic sledgehammer


Reged: 09/16/11

Loc: On a receiver's back
Re: CA Reduction filters new [Re: Mike4242]
      #6114802 - 10/03/13 09:49 AM

Very interesting report. I wonder if stacking a Baader Moon and Skyglow filter with the Longpass would correct the color shift as it does with the Fringe filter?

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russell23
Post Laureate
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Reged: 05/31/09

Loc: Upstate NY
Re: CA Reduction filters new [Re: Mike4242]
      #6114818 - 10/03/13 10:00 AM

Quote:

Wow! Thanks for that report. Very interesting indeed. I have to admit, I didn't think the yellow #8 would be just as good as the Fringe Killer. The yellow #8 is definitely the most economical way to go. I might have to pick up one of those 495 long-pass filters myself.




Yeah - I came in for the night really excited about the 495 longpass filter. The Fringe Killer is excellent but the 495 longpass takes it to a whole different level.

Last week I found a PDF that gives the transmission data from 400-700nm for all the wratten filters. The #8 is as follows:

<460nm 0%
460 0.25
470 5.5
480 19.0
490 41.0
500 63.5
510 78.0
520 84.1
530-700 86.5-91.5%

These numbers are a stronger cut than the FK so I was surprised there wasn't much difference.

Lunar/planetary tests will be interesting when I get a chance.

Dave


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Jon_Doh
scholastic sledgehammer


Reged: 09/16/11

Loc: On a receiver's back
Re: CA Reduction filters new [Re: russell23]
      #6114831 - 10/03/13 10:08 AM

Here's another thread about the Longpass filter:

http://www.cloudynights.com/ubbthreads/showflat.php/Number/5047210


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russell23
Post Laureate
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Reged: 05/31/09

Loc: Upstate NY
Re: CA Reduction filters new [Re: Jon_Doh]
      #6114842 - 10/03/13 10:16 AM

Quote:

Very interesting report. I wonder if stacking a Baader Moon and Skyglow filter with the Longpass would correct the color shift as it does with the Fringe filter?




I think it would but for deep sky it will dim the image so I would only stack them for lunar/planetary only.

Dave


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russell23
Post Laureate
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Reged: 05/31/09

Loc: Upstate NY
Re: CA Reduction filters new [Re: Jon_Doh]
      #6114970 - 10/03/13 11:33 AM

Quote:

Here's another thread about the Longpass filter:

http://www.cloudynights.com/ubbthreads/showflat.php/Number/5047210




That was the thread that led me to try the 495 longpass. Notice in the pictures that the Semi APO shows a fair amount of false color but the 495 shows none. That is what I saw visually last night and the photos in that thread capture the visual difference pretty closely.

Dave


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Mike4242
Pooh-Bah


Reged: 11/02/11

Loc: Memphis, TN
Re: CA Reduction filters new [Re: russell23]
      #6115022 - 10/03/13 12:03 PM

Have you ever tried the Contrast Booster?

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Jon_Doh
scholastic sledgehammer


Reged: 09/16/11

Loc: On a receiver's back
Re: CA Reduction filters new [Re: Mike4242]
      #6115043 - 10/03/13 12:17 PM

A little off topic, but for folks sensitive to CA, here are a couple of articles where CA was reported in the ES 127 ED:

http://explorescientific.com/telescopes/ES127Review_v1.pdf
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/4873424/page...

I wonder if it is necessary to use a Fringe or Long Pass filter with the ED scope?


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Niklo
professor emeritus


Reged: 03/29/13

Loc: Bavaria
Re: CA Reduction filters new [Re: Jon_Doh]
      #6115280 - 10/03/13 02:09 PM

Hi,
today I tried Jupiter without filter and with the fringe killer with my 4" 1100mm achromat.
http://www.cloudynights.com/photopost/showphoto.php?photo=28394&size=big&...
and with the fringe killer please see here:
http://www.cloudynights.com/photopost/showphoto.php?photo=28396&size=big&...
Clear skies,
Roland

Edited by Niklo (10/03/13 02:10 PM)


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Mike4242
Pooh-Bah


Reged: 11/02/11

Loc: Memphis, TN
Re: CA Reduction filters new [Re: Niklo]
      #6115348 - 10/03/13 02:46 PM

The fringe killer photo appears to have better contrast.

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Mike4242
Pooh-Bah


Reged: 11/02/11

Loc: Memphis, TN
Re: CA Reduction filters new [Re: Mike4242]
      #6115376 - 10/03/13 02:58 PM

Looking at the contrast booster transmission graph, it looks like it cuts very slightly deeper into the blue/violet end of the spectrum than the 495 long pass. Also, the contrast booster has a sharp cutoff in the red at about 700nm and cut's some of the green, whereas the 495 long pass doesn't cut any of the spectrum in red or green wavelengths. Not sure what the difference would be in practice. Now we need a comparo between those two filters.

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Jon_Doh
scholastic sledgehammer


Reged: 09/16/11

Loc: On a receiver's back
Re: CA Reduction filters new [Re: Mike4242]
      #6115380 - 10/03/13 03:01 PM

The disadvantage to the contrast booster is that it dims the image a lot more than the long pass or fringe filter. But does a good job on the CA otherwise.

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Niklo
professor emeritus


Reged: 03/29/13

Loc: Bavaria
Re: CA Reduction filters new [Re: Mike4242]
      #6115411 - 10/03/13 03:12 PM

Quote:

The fringe killer photo appears to have better contrast.



Yes, it improves the contrast and reduces/removes the fringe. The only disadvantage is that the view gets a little bit yellow.
Clear skies,
Roland


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Jon_Doh
scholastic sledgehammer


Reged: 09/16/11

Loc: On a receiver's back
Re: CA Reduction filters new [Re: Niklo]
      #6115417 - 10/03/13 03:15 PM

Quote:

Quote:

The fringe killer photo appears to have better contrast.



Yes, it improves the contrast (planetary detail) and reduces/removes the fringe. The only disadvantage is that the view gets a little bit yellow.
Clear skies,
Roland




Combining it with a Skyglow filter will increase contrast while restoring the color by removing the yellow cast.


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PeterR280
Pooh-Bah
*****

Reged: 05/27/13

Re: CA Reduction filters new [Re: Niklo]
      #6115424 - 10/03/13 03:17 PM

I don't see much fringing on the non-filtered image. The colors are more natural. i never liked the greenish yellow tint of the frings killer.

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azure1961p
Postmaster
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Reged: 01/17/09

Loc: USA
Re: CA Reduction filters [Re: PeterR280]
      #6115450 - 10/03/13 03:34 PM

The white , or rather yellow elephant in the room with the Baader long pass is that strong yellow. I find the Fringe Killer is all the yellow I want on generalized targets before color shift begins to attenuate contrasts. That much yellow on Jupiter or terrestrial spotting or Saturn for that matter might be more hinderance than help. I'm impressed with the long pass on stars but I couldn't see carrying the baggage of that yellow on much else unless it waS to increase something like festoons in Jupiter or other bluer features.

Interesting filter though. I may get the Long Pass - just for limited use however. I'd be curious how it stacks with my Wratten 15 .

Pete

Edited by azure1961p (10/03/13 03:39 PM)


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