Posts Made By: Jon Isaacs

Andy Sedlacek said:

Does anybody out there in forumland know if a C5 can be made to mount atop a Vixen Polaris mount? I have completed my dream Polaris mount (you don't know how hard it is to find an MD-5 system!) and I've always wanted to put a C5 on one for convenient travel. Any suggestions? Thanx!

VMO

The Polaris doesn't have a dovetail so you need to modify it somehow. Rather than a dovetail, a pair of rings bolted directly to the Polaris may be more practical because it allows the tube be rotated so the finder can be moved to a more workable position. With the rings, you just leave them on the scope.

Rings for a C-5 are not so easy to find. I am looking for a pair to mount my deforked Nexstar 5 on a Vixen Portamount or a Mizar EQ, they are 146mm. The only thing so far I have found that might work are at Scopestuff, they are 5.7 inches is about 145mm.

Jon

Tom:

I have very little experience in this matter. I was able to use a 2 inch adapter with a 2 inch Meade refractor, dielectric 2 inch diagonal on a Nexstar 5. It looked to me though that a SCT diagonal might have clearance issues with the focuser knob.

Jon

Andy Sedlacek said:

I hear your words Billy! A scope with no goto and an ac drive will outlive the human race. And at that, never require a software upgrade.

VMO

Not quite true... my own personal CPU could use a new operating system..

Unless you never have anything else to do in your life, most people do not have the time to wait two hours, especially when work awaits you early the next morning. If I can see 4 or 5 bands clearly with my old 102, why wait 2 or 3 hours to try to see one more band, which will not be as clear.

My experience:

It is pretty simple to plan ahead far enough to set the scope out an hour before I plan to observe and start the fan running.

I have a good 4 inch apo refractor and I do use it very frequently. But if I want contrasty, detailed views of Jupiter, Saturn, Mars, there is no doubt in my mind that I will go with a Newtonian of 10 inches or more. Viewing Jupiter, it's not just the number of bands, it's the details and contrast within the bands, this is what aperture buys you. A 4 inch might make 200x on a good night but the image is dim and near the limit of the eye's resolution but at 200x, a 10 inch is just getting started.

It's true that for a given given aperture, planetary contrast is greater for a telescope without a central obstruction, this is a result of diffraction. But it is also true that the major diffraction effect is the result of the "outer obstruction", that is the aperture of the scope... that's why a 10 inch Newtonian will easily outperform a 4 inch refractor on any night when the seeing is sufficiently stable to make viewing the planets worthwhile.

Jon

Another angle, it's a daily runner..

Jon

I saw something about that... they go through about 400 tons of cooling water a day, it has to be stored since it is radio-active. Apparently they need to build a storage tank with a capacity of 1000 tons of water every 2 days... that's a cylinder about 35 feet tall, 35 feet in diameter.

There are currently a 1000 tanks, these tanks have plastic seals, they need to last 300 years or so.... one is already leaking.

It seems like contingency planning for an accident was not in place... it does not speak well for the industry as a whole. If you are playing with stuff that is so potentially dangerous, you need to be prepared for every eventuality...

It seems like they were relying on crossed fingers.

Jon

Billy:

From my urban backyard, sometimes I use a larger Newtonian but most often it's a 3 or 4 inch refractor. But out in the country where the skies are dark and clear, it's gonna be a Dobsonian of at least 12.5 inches and a 3 or 4 inch refractor.

Jon

jerome hayes said:

Found m33 ok but having trouble with m27 and 57 in my small city skies with my 100ed scope. Are they sensitive to pollution?

M33 is much more difficult than M57 and M27. If you can see M33 (not M31) then M57 and M27 should be a piece of cake and just require proper positioning. Both are visible in an 80mm from my urban backyard under a full moon.

M57 is small so it requires some magnification if you don't have an eye for small objects. M27 is large and visible with binoculars (10x50s for sure) from my back yard.

Jon

John MacDonough said:

If you're one of those beginning astronomers that is looking to purchase his first scope, my favorite recommendation is now available again. Thanks to Orion for reintroducing the 6" XTi. You can read my review here. I think it's an outstanding value. If you decide to purchase one, please also purchase a laser collimator (the least expensive available will do) at the same time. Keeping it collimated is essential, but also easy once you've practiced.

A few thoughts:

6 inch F/8 certainly a nice scope, I have owned a few, a couple of RV-6s, some Dobs. I am sure you will enjoy yours. However, these days, I have to believe an 8 inch F/6 dob is a better first serious scope. A few reasons:

- There is not much difference in size between a 6 inch F/8 and an 8 inch F/6, the OTA is a little bigger around but essentially the same length. For both scopes, the heaviest pieces is about 20 lbs.

- 8 inch versus 6 inches, this represents a significant increase in capability, globular clusters begin to resolve, galaxies are more easily seen, clusters are brighter, the planets are more detailed an brighter.. the difference is about 33% in resolution, 78% in light gathering, this is significant.

- 1.25 versus 2 inch focuser. The Orion XT-6 scopes come with a so-so 1.25 inch rack and pinion focuser. Stock they are generally tight and sloppy. With some work, they can be pretty nice but still not great. They also represent a significant limitation on the field of view, a wide field of view is an advantage for a beginner, particularly one interested in Star hopping. The 8 inch Dobs come with decent quality 2 inch Crayford focusers, the GSOs come with quite nice 2 speed units. Buying a decent Crayford and adapting it to the XT-6 puts the overall cost right there with an 8 inch Dob...

My thinking:

If the Intelliscope feature is important, Orion really has the only game in town. The XT-6i does represent a savings over the XT-8i. But if Goto is not on desired, then the 8 inch GSO dobs from Apertura, Zhumell, Astro-Tech and others represent a better value, the 2 speed focuser, a 2 inch 30mm widefield as well as a 9mm plossl, a laser collimator.. $400 buys you an 8 inch GSO shipped to your door.. cheaper than a 6 inch intelliscope by about $80.

If one is interested in a 6 inch F/8 Dob without Pushto, then the Bushnell Ares 6 is looks to be the best value. Manufactured by Synta who also manufactures the Orion Dobs, it has a 2 inch focuser and some nice accessories. It's also only $280.

- Laser collimators: a good one (Howie Glatter) with some sort of Barlowed laser, is a very good way to collimate a Newtonian.

However, the inexpensive lasers are best avoided. There are a number of reasons for this. First they rarely arrive collimated, I have seen quite a few of them, I have never seen one that was properly collimated so that when the collimator was rotated in the focuser, it did not scribe out a circle. They can be user collimated but they do not stay in collimation for long. The fit in the focuser is sloppy..

There are other, affordable, reliable collimation tools, the collimation cap shares many of the positive features of the Barlowed Laser for adjusting the primary mirror tilt, a Cheshire or Combination tool is useful for setting the secondary tilt.

My two cents...

Jon

One can certainly tell the difference between an 80mm and a 100mm scope, a 4 inch or a 5 inch, a 10 inch or a 12.5 inch.. . that's a difference of about 0.5 magnitudes. A factor of 2.5 is one magnitude, a skilled variable star observers can see 0.1 magnitudes...

A more relevant question: What is your goal, purpose, in going to a larger scope? What do you hope to see with the 127mm that you cannot see with the 100mm? What scopes are these?

Jon