First attempt on Jupiter with my ETX!

[yanyewkay]

I would like to know what caused the purple fringing effect on this picture. I though cats don't suffer from CA problems?

[jiahao1986]

hi,

actually my scope is a little bit out of collimation, and it doesn't seem to affect the visual view, however after stacking and post-processing, the effect might be amplified, and this could be the reason to cause the coler fringe

[weixing]

Hi,

I would like to know what caused the purple fringing effect on this picture. I though cats don't suffer from CA problems?

I think it may be cause by bad seeing or Jupiter is still too low.... sometime you'll see purple fringing even in Newtonian if Jupiter is not higher than 45 degree.

Also, I think sometime barlow will also cause some CA problem, although may not be visible in visual, but will become more obvious in imaging especially after stacking and image processing which bring out every possible details and colours.

Have a nice day.

[jiahao1986]

this is the single frame image



this is the image after stacking and without other post-processing



this is the final image, after sharpening, level, color, brightness and contrast ajustments

[rcj]

Just a note to add:

The ETX Mak uses a relatively thick correcting meniscus frontal lens, which leads to longitudinal chromatic aberration. Unless it is a two-element achromatic corrector (which is expensive), the residual CA cannot be nullified completely. Such a corrector can only be paraxially achromatic which means the light rays very close to the optical axis will have the same focus for different colour wavelengths. However, once the light rays come on near the outer zones, this will not happen similarly, thus as a result of this (called spherochromatism), longitudinal chromatic aberration will still occur, particularly in the outer zones. Thus if one were to correct for this, an additional lens element can be placed in the front of this corrector, but if one were to completely eliminate residual spherical aberration at the same time, you will have to make the lens apheric too (which in turn has a further consequence, the resultant colour-free FOV is even narrower).

[acc]

In English please?

[weixing]

Hi,

Just a note to add:

The ETX Mak uses a relatively thick correcting meniscus frontal lens, which leads to longitudinal chromatic aberration. Unless it is a two-element achromatic corrector (which is expensive), the residual CA cannot be nullified completely. Such a corrector can only be paraxially achromatic which means the light rays very close to the optical axis will have the same focus for different colour wavelengths. However, once the light rays come on near the outer zones, this will not happen similarly, thus as a result of this (called spherochromatism), longitudinal chromatic aberration will still occur, particularly in the outer zones. Thus if one were to correct for this, an additional lens element can be placed in the front of this corrector, but if one were to completely eliminate residual spherical aberration at the same time, you will have to make the lens apheric too (which in turn has a further consequence, the resultant colour-free FOV is even narrower).

Hmm... I think this is a bit too "deep"... most of us won't understand... ha ha ha

IMHO, as long as there are glass elements in an optical system, there'll be some form of CA... it may be so small that you can't see it visually or normally detect it in your image.

Have a nice day.

[weixing]

Hi,
Found a page in dpreview and it mention that some "Purple Fringing" is caused by the microlenses or Blooming on some digitial camera:
http://www.dpreview.com/learn/?/key=chr ... aberration

Have a nice day.

[kayheem]

In English please?

Aiyoh...what he means is to buy TMB or AP apo to solve the problem! :-)

[mrngbss]

Jiahao, can you sort of provide some of the settings you play with to get from your pre-processed (registaxed) pict to your final processed pict? You are very good in adjusting these settings.

Thanks.