planetary viewing scopes

I currently own an AP 130 EDT for viewing planetary objects (not photography/CCD). However, I'm looking into an Obsession 15". Has anyone compared these two instruments for just viewing planets? Is it worth it to sell my AP to buy the Obsession? How often would the atmosphere affect the Obsession views since it has much greater light gathering capability?

Thanks,

Rob

Rob,

It really depends on your seeing conditions. Living in the foothills near Denver, I've found that my 130 consistently gives me better views than my previous 12.5". Yes, when seeing is really good, aperture wins. But when the seeing is only fair (about 90% of the time), the 130 is a winner. Also, the cooldown is faster with the refractor.

BTW, if you're selling your EDT please let me know!

Thanks,
Bill

Cooldown is a big factor. If storing your scope indoors you may have to wait an hour or more to get good planetary views with a big Newt. Of course, 15" of aperture admits an off-axis aperture mask of something like 6", so after cooldown you should be able to beat your AP 130 that way even if seeing is a factor.

A lot depends on the quality of the mirror, and I'd sure feel more comfortable about Zambuto or Pegasus than Nova, Galaxy, or Torus, but that's because Carl and John have built a reputation for excellence, and I just don't know where Nova, Galaxy, and Torus are right now. You can't have great planetary performance without a smooth, well-corrected mirror. For planetary observation I'm not sure a 15" mirror is that much better than a 12.5" on anything but the best of nights, and 12.5" is a more manageble size. If you can afford a 12.5" or so Dob with great optics I think you'll find having BOTH refractor and reflector is really nice. Of course 15" is going to be a noticeable step up from 12.5" for deep sky.
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Mike

The reral advantage of the 15" is deep sky. I doubt that you will see much improvement on planetary. And, given what it takes to set up a 15 in dob on a tracking platform, I think that you'd actually see a lot less.

If you are considering the Obsession 15 for the circumstances you cite, then go for it.

As has been said, if the atmosphere will not do sub arc second seeing, then you can mask it down (both off and on axis). This is not a project scope. You won't have to upgrade parts. It is high performance, with superior optics and movement. Hand traking at high power is not an issue, if your scope is made for hand tracking at high power. These are. They are also one person scopes: compact and portable.

I had a budget dob. I still have it, but there is very little left of it's original hardware. It still needs more upgrades. Lower power sweeps were wonderful. High power deep sky and planets were not. Until after upgrades. Like those that Obsession (and other premium dobs) have as standard issue. My 3 cents.

john