Which Filters for controlling CA

[Xiionn]

I have given up on the idea of a Chromacor!

I have been researching some filters. Opinions seem varied on which is best to control CA on an Achro. Some say a 495 Longpass, others say it tinges things yellow, some rate the Baasder Semi Apo, some prefer the Fringe Killer (Others say it tinges yellow) One idea was to use a #8 yellow combined with a #50 Blue.

I have also gone looking for these items online, and i can only find the Apo. The others all come in a kit of four!

Thoughts?

[southernman]

I have an earlier Skywatcher 150mm F/8 achro refractor and originally used a Baader fringe killer filter with some success. It does however leave a slight yellow cast to the view. At a later time I found using a Crystalview moon and skyglow filter in conjunction with the Baader fringe killer filter gave a more natural view. Nowadays I remove the centre section of the dust cap making the scope an approx. 4.5" F/11 which works even better although obviously only on solar system objects. For DSO's full aperture works fine.

Hope that helps.

Peter

[Sirius Starwatcher]

I've not long had a baader semi apo filter and find it has made a really big difference to the CA in my 120 Refractor

Home :: OPTICAL ACCESSORIES :: Filters :: Other Contrast & Deepsky Filters :: Baader 2" Semi APO Filter (optically polished)

Printable version

[SpaceWalker]

 Opinions seem varied on which is best to control CA on an Achro. Some say a 495 Longpass, others say it tinges things yellow, some rate the Baasder Semi Apo, some prefer the Fringe Killer (Others say it tinges yellow) One idea was to use a #8 yellow combined with a #50 Blue.

I have also gone looking for these items online, and i can only find the Apo. The others all come in a kit of four!

Thoughts?

The 495 Longpass is the most effective but produces intensive yellow cast. The #8 Yellow  is less effective, but still very good and gives *some* yellow cast. I prefer the Semi Apo, since it shows colors closest to natural. I've read here recently, on SGL, somebody said it blocks ~60-65% unfocused spectrum, I can live with it. The Baader M&SG alone is not effective, it should be combined with the Fringe Killer to work like the Semi-Apo.

For single #8 Light Yellow filter check out this link.

[Xiionn]

I just made a filter, just for something to do. I took some old Hoya blue and yellow flash filters which when paired gave a sunglasses type effect to the naked eye, no bothersome colour cast to speak of. So I ground them to size, epoxied them into the standard cheapo plastic celestron 10mm  EP  and added my revelation 2.5x barlow. Tested that against the bright blue sky on a hut accross the fields about 3/4 mile away. It reduced the CA to a fair point, increased contrast a tad and dropped the brightness by about 20%. CA was still there, just wasn't as noticeable. These filters are probably not the ideal colours as they are designed for removing colour casts in flash photgraphy, but still. I think there is hope. I will get some 2" planetary filters, i might also try the Semi Apo filter.