Quote:
Originally Posted by glend
...but there is the rub: not enough aperture to make it really useful for DSO work. The reactor can resolve bright double stars (or triples like Beta Moncer..) well but it has no real reach. Even for widefield star work on clusters and Eta Carinae, the refractor can't provide the expanse of view that the dob has.
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Doesn't that depend on the size of the DSO and the exact nature of the "work"? I've looked at M31 through 10 and 12 inch dobs versus a small fast 'frac and was somewhat underwhelmed by the "improvement". More detail? Yes. Different? Yes. Better? No. Each has its merits. Every DSO has a context. And some DSOs are just too big for big dobs. To me the key components are exit pupil and FOV. They are the end result the optical train provides and all that matters. Aperture is just a means to that end and only needed if you want high power. Power is a matter of taste. I do want to be able to view at high
and low powers, do so efficiently and enjoy the advantages each has to offer. The FOV a dob provides at 15x is not good enough - that's if you can find an eyepiece for this in the first place. A big dob is as useless for low power as a small frac is for high power, IMHO. Please correct me if I'm wrong here.
The statement you make re the "expanse of view" that a refractor can't provide as opposed to the dob - Is that really the case when a fast refractor is used?
Quote:
Originally Posted by glend
So why do people buy refractors (maybe they live in small apartments), or do mostly guided astrophotography on expensive mounts. But for stunning visual vistas, it's the dob hands down.  |
I have bought a small refractor:
- because I do not do AP and want stunning visual vistas. For that, a wide FOV is key. Even with my 1.25" back, I can take in over 4 degrees of sky.
- because I do not want an expensive mount. It sits on a photo tripod.
- because I want viewing comfort. I observe best standing up, feet on the ground, line of sight horizontal. The refractor setup provides exactly that, no matter where it's pointed. Viewing comfort means more detail seen at lower powers.
- because I want ultimate speed & portability. The fastest I have set up my visual rig ready for pointing was 33 seconds, out of the boot of my small car (Loading the gear into the boot at home: 10 seconds). Cool down time: Nil. Try to beat that with a 16" dob.
- because I want flexibility. Spotting Syrtis Major from the lounge room? Possible. Observing Jupiter while cooking dinner? Piece of cake. Counting feathers on that Rosella in the garden? Easy.
- because I chase eclipses (some). The Sun doesn't care about aperture unless you want the finest of details. Plenty of light for everyone. The Sun in Total Eclipse through a low power scope - I won't even try to describe it. Outside of the moon's shadow: White light and H-alpha, both excellent.
- because I want to observe planets during the day. What's the current phase of Venus look like? 33 seconds - you get the idea. Try moving a light bucket along with the moving shadow of a building to stay safe when the target is close to the Sun.
- because of the Moon. It's there on most nights. No other object shows that much detail. Again, plenty of light.
- because the best scope is the one used most often.
And finally, I have bought a small refractor because I can always use a dob for the higher magnifications. The 10" has recently arrived and is waiting to be put to work
I agree with all of this. 
