Chromatic Abberation in Refractors

[ONSLOWE]

In a fast (f5,f6 or even f8) refractor is CA limited to the very brightest stars (Sirius, Vega, Rigel etc), Venus and the Moon ? Having a limited budget it is tempting to go for a Startravel or Evostar refractor of 100-120mm rather than an 80mm semi APO. I have never forund looking at Sirius etc to be the most interesting objects and though the phases of Venus are impressive I would rather be seeing Saturn, Jupiter and clusters in more detail with the extra light grasp. I realise I could get a Reflector to avoid CA but I prefer Refrators. Does the CA spoil the view of contrasting coloured double stars ? Thanks for any advice

Martin

[barkis]

Achromatic refractors need to have a long focal length if you want minimal Chromatic aberration. Even then it's no guarantee.

I have a 150mm f8 refractor, and I am quite happy with it. It does have CA, but I don't let it bother me. I get some very good views with it, especially on the moon. A yellow rim is always there, but I ignore it.

You have to go APO to reduce CA to a minimum, and even then, there may be some still If it is a doublet.

You could spend an awful lot more money and go Triplet to almost guarantee no CA. The question is, . Are you prepared to spend big Bucks.

Ron.

[The Warthog]

I have a minus violet filter in my frac, and am almost unbothered by CA. I used to use a yellow filter on the Moon before I had te -V filter, but it isn't really an issue inmy enjoyment of the view.