Baader Fringe Killer

[CoolhandJo]

Just thought I would post my recent experience with Baader Fringe killer. I use an Achromat at F7 and the Fringing on RGB is not useable. I stumbled upon the Baader Fringe Killer and it reduce the fringe by over 70% and makes the RGB subs useable.

taken on different nights and one night moon very close but these give a good indication on how effective this filter can be for an Achromat

[Saturnine]

Hi Paul

Minus Violet filters have been around for a while, from several manufacturers for using with achromat refractors. I have several, including the Baader Semi Apo and Williams Optics MV. With my 127mm / f9.4 and 150mm / f6.5 they work well enough , that the colour fringing is not intrusive. Doesn't spoil the view for me and I don't find the colour fringing as problematic as some folks might but it doesn't magically turn the achros' into astrographs and aren't intended too. They are for visual observing and the fringing is really only noticeable on the bright objects.

[CoolhandJo]

Good to know Jeff! I see people using these for astrophotography also and have some good results. It seems the Fringe killer holds the colour more true and reduces the Fringing a lot. Have you used yours for Astrophotography?:

[floyd_2]

You could also consider a software approach, using the Camera Raw plugin for Photoshop (Lens Correction tab). It has a Defringe tool that I've used in years gone by quite successfully.

[CoolhandJo]

Thanks. Yes I use that but without the fringe killer the stars are twice as big and bloat

[Saturnine]

No, I Don't use mine for astrophotography, I have apos' and newts for that . Sometimes I just like to get out an achro for quick sessions on double stars or getting an idea of what the seeing is like before setting up more complex gear.

[glend]

The effectiveness of the Fringe Killer depends greatly on the quality of the objective, as all acromats are not equal. I will give you two examples:
1. A Bresser 150mm f5, you would think it would be terrible but it actually had a Prezel lens at the rear which acts as a field flattener, and which provided some defringing by bringing the violet light closer into the focal point. When a Finge Killer was added it was a very nice wide field scope with little fringe. Btw I also used this scope for narrowband imaging for a couple of years, at which it was terrific. Sadly they are hard to fund new these days, only Teleskop Services seem to list them.
2. My iStar 127mm f12, also an acrobat but with a special glass formulation, that reduced fringing by 35%, add a fringe killer and it was very clean. Once you get an acro out to f15 there is no fringing anyway, and at f12 with the filter, it performed like an f15.

Consult this thread on the Cloudy Nights forum to get a complete, detailed look at CA in Acromats.

https://www.cloudynights.com/topic/355643-chromatic-aberration-chart/

[CoolhandJo]

this is incredibly useful and explains a lot! Id love to see how the Fringe killer versus Semi apo shift the chart numbers :)

[doug mc]

Thought you might be interested in this post taken from a CN member. Having owned one of these filters for visual only, i found it always cleaned up whatever i was looking at. It imparts the least yellowing than the other filters here, while removing about the same amount of colour fringing. To remove the yellowing effect of this filter, Baader introduced the Semi Apo filter which cuts into the yellow area of the spectrum to balance the colour, at the expense of light throughput.

[CoolhandJo]

Thanks. i saw that also and I think its the baader Fringe killer with Skyglow Neodymium bandpass overlay?