C A filter

[Mark Daniels]

Hi

could someone recommend a CA filter for 1.25 eye piece. Not sure who does one looked online but can’ seem to find them 

cheers 

[John]

The Baader Semi-Apo filters get decent reviews and seem work well:

https://www.firstlightoptics.com/baader-filters/baader-semi-apo-filter.html

The Baader Fringe Killer does a similar job:

https://www.firstlightoptics.com/baader-filters/baader-fringe-killer-filter.html

As does the Baader Contrast Booster:

https://www.firstlightoptics.com/baader-filters/baader-contrast-booster-filter.html

I believe the Semi-Apo produces the most natural tint to the view wheras the other two do introduce a slight hue to the image.

Here is some further discussion on these:

 

[vlaiv]

If by CA filter you mean filter that will lessen chromatic aberration, then you can use any of the following:

- simple wratten #8 filter. This works very well, but casts a yellow tint on the view

- Baader Contrast booster filter - this works well on F/10 achromat and the Moon (I was really surprised) - probably other planets as well. Not as good as I expected on bright stars

- For complete removal of any CA - Baader continuum filter. This is rather "specialty" filter usually used for white light solar observing. It impacts strong green cast on the image. I found that it transformed my F/5 achromat in spectacularly sharp moon scope (although like I said - green cast). It is probably very useful for double star observing as well (it helps with seeing besides CA).

- Look also at Baader fringe killer and Baader semi apo filters (used neither and opted for Baader contrast booster instead on my F/10 achro).

[joe aguiar]

What u can also do alot scopes  refractor comes with an inner dust cap in the main dust cap.

Take that smaller cap out and that reduces colour alot.

As an example if u had the 4inch f5 model refractor it turns it into something like a f8. Of course it's not 4 inch anymore but 3 inch. Depending on your cap size

Joejaguar 

Edited November 13, 2019 by joe aguiar

[Rob]

Always found this helpful.. its from a post in CN. Its just nice to see a visual comparison. Rob

 

 

[John]

I used a William Optics Minus Violet filter with a 150mm F/8 achromat refractor a few years back and compared the views of the moons limb with and without the filter. I found that the filter reduced  the visible violet fringe by around 50%. The flip side was a pale lemon tint to the overall view. The CA was still visible but it was reduced.

 

[Rob]

2 hours ago, John said:

I used a William Optics Minus Violet filter with a 150mm F/8 achromat refractor a few years back and compared the views of the moons limb with and without the filter. I found that the filter reduced  the visible violet fringe by around 50%. The flip side was a pale lemon tint to the overall view. The CA was still visible but it was reduced.

 

I had one of the WO -V filter and found the same John. I now switch between a Baader Fringe Killer & Wratten #8.. that said I often dont use one at all!

[John]

3 hours ago, Rob said:

I had one of the WO -V filter and found the same John. I now switch between a Baader Fringe Killer & Wratten #8.. that said I often dont use one at all!

I don't recall the Bresser 127-L that I had producing any really objectionable CA Rob. A good 5 inch achromat I thought 

[Mark Daniels]

21 hours ago, John said:

The Baader Semi-Apo filters get decent reviews and seem work well:

https://www.firstlightoptics.com/baader-filters/baader-semi-apo-filter.html

The Baader Fringe Killer does a similar job:

https://www.firstlightoptics.com/baader-filters/baader-fringe-killer-filter.html

As does the Baader Contrast Booster:

https://www.firstlightoptics.com/baader-filters/baader-contrast-booster-filter.html

I believe the Semi-Apo produces the most natural tint to the view wheras the other two do introduce a slight hue to the image.

Here is some further discussion on these:

 

Very helpful thank you

[Mark Daniels]

21 hours ago, vlaiv said:

If by CA filter you mean filter that will lessen chromatic aberration, then you can use any of the following:

- simple wratten #8 filter. This works very well, but casts a yellow tint on the view

- Baader Contrast booster filter - this works well on F/10 achromat and the Moon (I was really surprised) - probably other planets as well. Not as good as I expected on bright stars

- For complete removal of any CA - Baader continuum filter. This is rather "specialty" filter usually used for white light solar observing. It impacts strong green cast on the image. I found that it transformed my F/5 achromat in spectacularly sharp moon scope (although like I said - green cast). It is probably very useful for double star observing as well (it helps with seeing besides CA).

- Look also at Baader fringe killer and Baader semi apo filters (used neither and opted for Baader contrast booster instead on my F/10 achro).

Thank you

[Mark Daniels]

9 hours ago, Rob said:

Always found this helpful.. its from a post in CN. Its just nice to see a visual comparison. Rob

 

 

Very helpful thanks

[Rob]

17 hours ago, John said:

I don't recall the Bresser 127-L that I had producing any really objectionable CA Rob. A good 5 inch achromat I thought 

True enough John. My 127-L appears to be a good one, so will stay filter less around 80% of the time. The wratten #8 does boost the contrast on Jupiter, but you have to deal with the strong yellow of course!.. so its in & out quite a bit.

Rob