Posts Made By: Paul Kammueller

I like the way you hung this question out there with a long tongs!

Morality, religious or not, has but one purpose: to facilitate the cohesion of the society in which it is developed. Humans are social animals, living in herds -- they don't do as well on their own as they do in groups.

So our species developed 'morality' -- because it helped us survive. After all, if you chose to kill or rape the mate of the guy living in the next cave, the guy in the next cave might kill you for revenge. Probably the guys in the next four caves would get together in a caveman posse and kill you, simply as a precaution.

The morals in most societies do not appear to be absolute: generally they are meant to foster altruistic behavior toward other members of its own society, but are generally permissive of violence toward members of another society. We need to be able to fight wars without feeling guilty, so morality is predictably selective.

At that size it might be cheaper just to buy a new mirror. You could get a 4.5" f/8 Orion mirror for $39.95 -- or if you want to take this opportunity to upgrade it you could get a nice Discovery mirror for $80 too

You ask me, they are both (dust and scratches) a question of degree. The scattering impact of dust particles will depend on (1) the diameter of each particle relative to the mirror's diameter and (2) the density of particles distributed on the mirror's surface.

I suspect that things have to be pretty dirty to start to have a detectable impact. I like to keep my mirrors clean too but have yet to see a detectible change in performance from cleaning. Mind you, I don't let them get too grubby to start with. I too am very careful in cleaning, and in my opinion you run a greater risk of scratching the optics if you wait longer to clean, since you're having to get more gunk off at one time.

I have also seen varying degrees of scratching. I have seen multiple hairline sleeks have no detectable effect. Even 3 or 4 BIG scratches, like you'd get from a few swipes with a medium-sized chunk of gravel, having no detectable effect on a fairly large mirror (like 14"-16"). But get lots (and I mean lots) of cross-crossing ultra-fine scratches on a tiny secondary and you've got a serious light scatter problem.

It's all a question of degree and severity, relative proportional area impacted, etc.

Congratulations!!!

Does he have a bike too, or are you gonna tow him around in the kiddie trailer?

I'll vote for Antares Optics. I've used them for my last two purchases, the 1.5" for my 10" f/8 planetary dob, and just recently the 1.3" for my new 6" f/6 porta-dob. I really like them, they supply a very comprehensive and complete 3-d interferometer test chart so you can see exactly what you've got, and where the highest peak and lowest valley is. Their prices are indexed to wavefront accuracy so you get exactly what you pay for.

The last 1.3" flat I got from them was rated to 1/25 wave P-V... but then I saw the test report, and nearly all that error is at the edge -- a 1/25th wave 'turned edge' -- in fact the vast majority of the mirror's surface (which is pretty much all that will be catching the on-axis light cone), away from the edge, is closer to 1/70th wave P to V!! Yeehah!

I have a strict rule against selling thousand-dollar telescopes to guys who have no money, no credit, and no record. Hey, you gotta draw the line somewhere...

That ad is an awfully tall order. He's looking for a seller who is willing to (1) part with an expensive, modern telescope, while (2) assuming a *completely* unknown credit risk. There's not a lot of people here who would lend $1000+ to a total stranger just on his face. There is no rate of interest high enough to balance that sort of risk on a loan.

You are interpreting correctly, though the linear profile is leading to some erroneous generalization: the 'low point' isn't actually at one end, but around most of the edge, this can be seen from the two-dimensional color-coded profile at upper left. This is fairly typical, i.e. a bit of a 'turned edge' to the flat. The edge usually forms the valley of the peak-to-valley. Much of the non-edge surface of the secondary is between 1/30 and 1/40 wave P to V, so depending on how tightly you're sizing the secondary, it's possible that images at the center of the field (the on-axis light cone) will behave closer to 1/30 wave while somewhat off-axis images will perform closer to 1/13 wave. Not that it would be very easy to tell the difference in any case.

Align the secondary first. Then align the primary. If it's visually confusing, align the secondary while the primary is out of the tube for cleaning, then you can just center the tube's rear hole in the secondary.

Lose the focuser with the built-in barlow. Being stuck at f/13 with what may be sub-par optics is a severe handicap indeed. Dropping to f/6-f/7 will enable lower magnifications and brighter, more pleasing images. You can always stick in a separate barlow if the optical quality allows, but the instrument will be more versatile and flexible at f/7 than at f/13. Be prepared to change the position of the primary, though, since removal of a built-in barlow has the potential to change the position of the focal plane (i.e. it may no longer be able to reach focus).

Don't worry about goto. Just one tip, use your lowest power eyepiece (makes it nice and bright and easier finding stuff anyway) and just wander aimlessly through the Milky Way -- don't feel like you have to hunt down specific objects right away, just relax and enjoy it a little at first. Look at the Moon, the first look at that in a 6" scope it will absolutely blow you away. An f/8 scope is very forgiving with collimation/alignment so you can get by without worrying too much about that yet. You made an excellent choice for a first scope, no complex gadgetry needed, just point and shoot. Congrats!

P.S. one thing that may be frustrating is timing of the purchase: all the planets are currently hiding amongst the Sun's glare. But you will see some very cool stuff with this scope as they re-emerge in the early pre-dawn sky later in summer/fall.

Maybe. Though to be fair, if I were God I'd probably do the same. I would want humanity to stand on its own and not waste its time worrying about where I am or what I'm doing. I am reminded of an episode of "Futurama", wherein the chronic alcoholic robot Bender meets God far out in space, who tells him:

"...You have to have a light touch. Do too much, and people grow dependent. Do too little, and they begin to lose hope. But if you do things just right, they'll begin to think that you haven't done anything at all."