Lib, as it happens, the Jan. 2000 issue of S&T has a report on the 8" Dobs on the market right now, bench-testing and comparison. Although they found some problems with each of the scopes, the Orion was the best of the models they tested (which also included the Bushnell Voyager, Celestron Star Hopper, Discovery DHQ, Meade Starfinder, and Starsplitter).
Here were the results for the Orion (which retails for about $499):
Portability: Good
Focuser: Excellent
Balance adjustable: No
Smoothness of motions: Good
Overall mechanical quality/design: Very good
Ease of assembly: Very good
Assembly instructions: Excellent
Use instructions(for beginners): Good
Star test of mirror: Fair-good
Sharpness of planets: Good
Brightness: OK
Freedom from tube currents: Fair-good
Overall optical grade: Good
Ease of collimation: Fair (both mirrors)
Collimation instructions: Excellent
Eyepiece quality: 25mm Fair, 9mm Good
Finderscope quality: Good
Adjustment ease: Good
It’s probably worth checking out the article for comparisons and details.
My scope is a Meade 114mm (4.5") Newtonian reflector, and I’m happy with it. Not so good at deep-sky objects (especially in an urban setting), but for planets, double stars and star clusters, you can’t ask for much mor for the money.
"I prefer shows of the genre, “World’s Blankiest Blank.”
Thanks for clearing up the goals. I had kinda thought they were more biologically-oriented.
The ones I am most interested in are:
o Image landing site (in stereo yet!) to determine soil types and mineral composition
o Dig into surface and collect soil and layer data.
o Analyze soil samples for evidence for water, ice, hydrates, and aqueously deposited minerals.
I doubt we will find life doing that, but if we detect the right constituents, it might be evidence that the building blocks of life are not unique to Earth. From there it will be easier to describe possible pathways from “primordial soup” to early organisms.
Of course, it might not really help at all, since Mars isn’t Earth. It might just confuse things … I mean, young Earth must have been profoundly different from old Mars. It will certainly be interesting though. Let me throw out a pure hypothetical:
Let’s say we detect some frozen ammonia, kind of near some frozen hydrogen sulfide. We might then be able to reconstruct those conditions on Earth in some sort of “primordial refrigerator”. Then we could heat up and irradiate the contents of our refrigerator to make a “primordial radar range” (I’m liking this primoridal stuff, huh?) Then we could study the effects over a nice long period. Eventually, maybe proteins would form.
I don’t think this is going to clear up any political debates, but I think it would give a fascinating answer to the question: How warm and bright would Mars have to be to host life forms (assuming it doesn’t already).
Then, someone needs to answer the question, How do we reverse the positions of Mars and Venus so life can evolve on both? (I used to ponder this one all the time as a kid.)
What in the blazes are you talking about, Phaedrus? We seem to not be speaking the same sort of english.
NASA has a stated goal of searching for life on mars. To that end they are planning a sample return mission for sometime in the next decade, which I guess is what the mag was talking about. But you claimed the Mars Polar Lander is searching for life on mars this week. It isn’t.
And even if the longer range search for life on mars turns up empty, why would that be an “embarrassment”? Maybe there wasn’t any, or wasn’t any right where we looked. It would be a disappointing result but it would still convey knowledge and a huge amount of important science would still be done on the soil sample.
The two things I recommend when people ask me (which you really didn’t but what the heck) about getting a telescope is:
Make sure it is a reflection telescope and not a refraction telescope. The Orion one you mentioned is reflective so all is good there.
Get a motor operated telescope. Now this is personal taste but I can’t stand manually setting a telescope. Of course, optimally you want to get one where you can choose to adjust it manually without stripping the gears of the motor.
Thanks. I can’t tell you how much I am looking forward to this. It is one of those always-wanted-to-but-never-made-the-time things. Later, maybe I can upgrade to a good scope like y’all have. But for now, I will be content just to look out across the heavens that my Father made with awe and wonder. I will think of Galileo, and of the suffering he endured at the hands of religion politicians. I will think of David, the Psalmist, and his inspirational poetry about the beauty of the sky. I’ll even think about guys like you, wondering if you’re seeing the same things I’ll be seeing. (I’m going straight for Saturn first, then the moon, then the Messiers, then all the other planets. Don’t think I’ll do any sun gazing, though. One false move, and its over…)
I can’t wait! We live in a very rural area with very little light, a jet black sky, and bright stars.
“It is lucky for rulers that men do not think.” — Adolf Hitler
It is a clunky old 5" refractive manually adjusted telescope. It’s pretty though (and expensive … I can only imagine what my wifey could have got with what she must have spent on it) since it is made of brass.
Anyway, I’m jealous.
As for Glib/Glitch, one could logically take being called Glib as a compliment so no problem … now if you confused Glitch with dumbass maybe I may have been insulted.
Libertarian - I envy you. I live in an urban area with a fair amount of light pollution (it’s “adequate lighting” when you’re walking alone at night, and becomes “light pollution” when you’re stargazing!) and a lot of overcast.
Glitch - What’s wrong with a refraction telescope? I only know in theory the difference between refraction scopes and reflection scopes; I’ve never heard how they differ in practical performance. I think you’re right about manual-adjusted sets - the last telescope experience I had was marred mainly by the difficulty of “fine tuning” with bare hands (we get barely get a fix on the moon). Am I right that mechanical sets make it much easier to fine-tune?
But suppose a future prove finds organic precursor compounds (as mentioned by David B).) How would you know those compounds don’t originate by contamination from a previous earth craft, such as the Mars Pathfinder?
La franchise ne consiste pas à dire tout ce que l’on pense, mais à penser tout ce que l’on dit.
H. de Livry
One last question for now. I am near-sighted. (I can almost feel your anticipation of the question…) Will I have to wear corrective lenses, or will I be able to focus the scope to compensate?
Seems like objects in a mirror (reflecting scope?) would still look blurred, since the light reflecting from the mirror has travelled mere inches further than it would have travelled if I faced it directly and would have seen it out of focus anyway.
“It is lucky for rulers that men do not think.” — Adolf Hitler
There isn’t anything really wrong with them, but reflection telescopes are better.
Reflection telescopes typically have a much brighter, clearer image. Back in my university days we had a couple of reflective and refractive. Looking at even relatively close objects like Saturn there was a very clear difference. The rings in the reflective telescope were very crisp as were the moons. In the refractive, you couldn’t really see the moons.
Looking at the moon really made it obvious too.
IIRC, the reason is that the lenses absorb some of the light or fail to refract it perfectly because of even very minor imperfections in the lense. However, a mirror is much simpler to make near perfect and gives a better image.
Yes, definitely.
There are some manually adjusted telescopes that have an ultrafine adjuster. It is basically a wheel you turn to adjust it (like the other adjusters) but you have to turn it ALOT to get even a small adjustment.
You can do either, but generally it is better to wear your glasses. Contacts are needless to say even better. I don’t think you can adjust (it just isn’t humanly possible to be that fine) the scope completely perfectly as your glasses as tailored for your eyes.
Do you wear glasses/contacts already, Lib? If so, I would definitely wear them when viewing. Even an excellent eyepiece with good eye relief doesn’t, as you speculate, provide enough additional distance for that light path. I’m nearsighted also, and I always wear my specs.
Sounds like you’re going to have a lot of fun. I had a friend over on Halloween who had never looked through a telescope before. It so happened that Jupiter and Mars were both above the horizon and seeing was good that night. I used a 9mm eyepiece to show her both. Jupiter was quite vivid that night–the cloud bands were easy to see, and all four Galilean moons were visible. Saturn, too, was perfectly visible, down to the shadow on the rings. She was amazed.
Sounds like we have the same kinds of feelings, mine are just nonreligious in nature. Every time I see the Hubble Deep Field photo, my mind just boggles.
This is an especially good time to start, in the winter, if you have dark skies. M42 in Orion’s sword will be easily visible, as will the Pleaides (amazing for the first time at any decent magnification), Jupiter and Saturn, and on Jan. 20, a total lunar eclipse.
My scope doesn’t have a motor drive, but the fine tuners work real well. Once you nail right ascension and declination, it’s pretty easy to find whatever you want.
"I prefer shows of the genre, “World’s Blankiest Blank.”
I predict the Mars polar lander will take a bunch of samples, probe them, and relay that data back to NASA JPL. I predict that NASA scientists will analyze the data. I predict that they will arrive at tenative conclusions based on this data.
In other words, I predict they’ll do science. Not prognostication.
“Love 'em, fear 'em, and leave 'em alone.” – Dr. Spockiavelli
Arnold, I know at one point NASA used to sanitize such craft for just this reason (Carl Sagan pushed them to do so). I do not know if they still do, but I would hope so. Even if some got past, we’ve shot a few spacecraft to the entire planet. It’s not like we’ve infested the place. So we ought to be able to tell.
I believe they still do. They build them in cleanrooms and so on for exactly that reason. And anyway, any contaminants would be mostly localized to the region where the probe landed, and the next probe digging into soil some thousands of km away would be unaffected.
OTOH, oddly enough, a good fraction of the moon’s current atmosphere is manmade (which was easy as it had very little to begin with).
It was always my opinion that if we hadn’t squandered a huge sum of cash on that ISS thing, we coulda sent some ppl to mars to look around instead. I had hoped to see that happen in my lifetime, but it doesn’t appear likely now.
I’ll have to agree with Phaedrus, here. I think the secret agenda of the Mars Polar Lander is to find evidence of life and cover it up.
Just like the Hubble Telescope was really designed and placed in orbit by the military as an early warning system against alien invasion based on evidence obtained at Roswell.
