refractor for DSOs

[Karen]

Hi All

Something I would like to know. Are widefield f5 4 inch refractors any good for visual use on DSOs. I wouldn't expect them to be as good as a large reflector.

[Bizibilder]

Aparture rules for visual DSO observing. That's not to say you can't use a refractor its just that if spending your hard earned cash a big reflector will win easily. For photographic work the refractor (APO) rules.

[nightfisher]

what he said^^^^^^^sounds like good advice

[Doc]

An F5 refractor will be Ok, of course no where near as good as say a large reflector. But at F5 you will see loads of CA around planets and moon but DSO's won't be to bad.

I have a 6" F5 refractor and it's pretty good on DSO's especially clusters.

[Capricorn]

There are a couple of 127mm and 152mm refractors that are f/5.6 which while achro's are pretty good for DSO's. But at that aperture they should be reasonable.

Some colour in them on things like moon, Jupiter and Saturn, however not too bad it would seem.

[Trull]

In my experience I've needed around twice the aperture in a reflector compared to a refractor - this is due to the obstruction ratio and the refraction spikes reducing contrast. The way around this is an advanced design like a Chiefspiegler, which is unobstructed but allows sensible f/ratios (unlike a Yolo ,say, which is really planetary optimised). This said, reflectors still win as they only need one large optical surface.

[Karen]

Thanks. It seems like there is no substitute for aperture for visual observing of DSOs. I have to think about getting a large DOB for next winter.

[John]

Thanks. It seems like there is no substitute for aperture for visual observing of DSOs. I have to think about getting a large DOB for next winter.

Dark skies are the other key factor. I've just got back from the SGL6 star party and last night, under clear, dark skies, we saw loads of DSO's with just 6" of aperture and the views of the brighter ones like M81 and M82, M51, M42 etc were sensational

So aperture plus access to a dark sky site would be the ideal situation.