Discoloured images

[george7378]

I have been observing Jupiter and the Moon, and for some reason, Jupiter seems to show an orange tinge on one side and a blue on the other, and the Moon's limb is surrounded by a very nasty looking orange halo. My scope is pretty badly collimated, but it looks the same from every angle. Can anyone help?

Thanks.

[John]

I could be the poor collimation or a poor quality eyepiece but often this effect is caused as objects get low in altitude and more of our atmosphere gets in the way. I believe it's called atmospheric refraction.

[michael.h.f.wilkinson]

It is atmospheric refraction. Poor collimation on a Newtonian can mess up an image, but not show colour fringes. This is why I gave Jupiter a go at 5 PM when it was still high in the sky.

[M42]

Hi. Yes this is caused by atmospheric refraction. But you are also using an f5 scope which though very good deep sky objects not too great for bright planets.

If you are using say 10mm eyepiece either stop the scope down (the front cover has a removeable section take that out and leave the rest of it on the scope) or use a 20mm eyepiece with a descent x2 Barlow.

Most people think a x2 Barlow doubles the power of your eyepiece. Well it does and it doesn't. What a x2 Barlow effectively does is double the focal length of your scope.

So if you look through a 10mm ep you are seeing through a 1200mm long scope at f5 giving 120x mag.

If you use a 20mm ep and barlow you are effectively looking through a 2400mm long scope at f10 still giving 120x mag.

The benefit of using a larger ep and barlow will give you more contrast on bright planets and you will see more detail.

Clear as mud eh?

[george7378]

Thanks for the help - yes, I think I understand now! It did get less and less noticeable when the Moon climbed higher during the night.