So I finally got myself a nice beginner’s telescope, a 6" Dobsonian. It’s a SkyWatcher with the standard accessories. (The 8" would have been hard to fit into the car.)
Ohhh, I love it. It’s awesome. Why didn’t I get into this years ago?
Question: I have taken a few peeks at Saturn and Jupiter these past few nights. Max magnification with my current setup is 240x, I think (10mm eyepeice, 1200mm scope, plus a Barlow 2x.) However, I was looking at them over Toronto - a rather huge light pollution source. But from my 35th floor apartment I could see them quite clearly.
Saturn appears to me to be a small cream-colored dot with a ring. Jupiter is basically just a cream-colored dot on which I can discern two hairlines running across it, and I believe I spotted a moon. So here are my questions:
If I leave town and drive to the boondocks I can see things (deep space objects, double stars, etc) I cannot see in the city. but will it substantially improve the quality of images of planets like Saturn and Jupiter? They’re coming in loud and clear, just very small and not detailed.
Is it possible, in fact, with a 6-inch Dobsonian, to see these planets clearly enough to discern things like the Great Red Spot or Cassini’s division? According to everything I’ve read, 240x power is pushing towards the upper end of a 6-inch scope’s resolving power, with 300x being about the max.
For looking at planets with a 6-inch scope, should I invest in an eyepeice that will deliver more magnification? In other words, would it be worthwhile to go to 300x, or even higher? I suspect more power would be worthless for seeing deep space objects, since the issue there is dimness, not size, and a good dark observing site is key there. (Fortunately my father in law lives in the middle of nowhere and has a big plot of land. Perfect location.) But could I ramp up big time just for the sake of looking at planets?
Do I need a filter? I have a green moon filter. I’ll be damned if I know why I bought it. Basically, it makes everything look green.
Note: if the answer to this is “no, that’s all you’re going to see with that scope,” I’m not upset. Its still the coolest thing I’ve ever owned.
Well, in truth, I don’t know. But I thought I’d point you to the forums at http://www.badastronomy.com - I’m sure they’ll have a lot of good info. Plus, they’ll be a great resource for you in the future, I’m sure.
Cities give off a lot of light and heat. The light’s not going to cause much trouble with seeing Jupiter and Saturn, but the rising heat causes turbulence which can erase the fine details in views of planets. Particulates and smog also cut down on the visual clarity of the sky.
2)On a good night you should be able to see Jupiter’s red spot. It’s not very red. The moons Io, Europa, Ganymede, Callisto should also be visible. You can check on their placement around Jupiter here. Casini’s division will also be visible in Saturn’s rings when the skies are clear and steady.
3)There should not be any need to go to 300x for viewing planets. In a city at a low elevation, you’ll just end up magnifying atmospheric turbulence.
4)I never understood those green moon filters either. Supposedly it improves the contrast a bit, but you still end up blinding yourself from staring at such a bright object. There are filters available that help with the sky glow in cities by cutting out the emission frequencies from mercury vapor and sodium lamps. You might try perusing a few issues of Sky and telescope (web site) for more information on filters.
Be sure to go to Heavens Above and check out the times for ISS visibility. You might be able to use your scope to tell whether or not the shuttle is docked.
Although the theoretical maximum magnification is 50X per inch of objective lens, atmospheric turbulence as well as the scope itself may make 25X a more reasonable expectation.
I am a bit surprised that you only saw one moon. You may have used too much power and narrowed your field of view too much. The moons are fairly easy with almost any visual aid.
I don’t own a Dob, but I expect that precise collimation is going to be critical for you to see the most and best possible. Are you sure it’s collimated well?
Light pollution in the city will make most deep space observing frustrating. On the other hand, planets and the Moon are essentially unaffected by light pollution. Have you looked for open clusters? They are also fairly robust even in light-polluted locales. And, the fall and winter are great times for them. Check out Auriga and its gems.
Filters are nice for various projects. They are especially useful if you get into any imaging. The best images are usually composite taken from different filters on the CCD.
When I run observing sessions we never look at the moon past first quarter, but still there have been kids who have cried because the moon was so bright in the scope. Now I use a makeshift lunar filter fashioned out of cardstock.
Resist the urge to buy any more accessories until you are thoroughly comfortable with what you already have. Observing takes a lot of practice–you won’t believe how much more you will see over time.
You say you are observing from your apartment–I presume you are pointing the scope out an open window? This isn’t good–the heat currents from indoors will blur everything. Piling on more magnification will only make it worse. I guess there’s not much you can do if you live in a high-rise apartment, but you’d be much better off from a backyard even if still within the urban area.
You have plenty of power to see the phases of Venus, the polar caps and major surface features on Mars (when it’s near opposition), the four moons of Jupiter–including their shadows on the surface of the planet during transits–and also to see Titan, Cassini’s Division in Saturn’s rings, to resolve Uranus into a disk, and to locate Nepture. (It looks like a star, of course, but it’s way cool just to know you’re looking at it.) And all that’s just within the solar system, and none of it (except maybe Neptune) even requires a dark sky. But be patient, it will take time and practice to see everything. Happy observing!
I strongly urge you to join a local astronomy club, or at least visit one. They will have lots of advice, and show you how to find things. I have a page with links on how to find one near you. Hope this helps, and have fun!
