Posts Made By: david roberts

September 26, 2004 04:12 AM Forum: Religion

I am the Light...

Posted By david roberts

Or maybe what is light anyways. After reading a few pop culture particle physics books, and some not so pop, the 2-slit experiment, as far as I can tell, is still a mystery. We live for bunches of photons on those clear nights, but I must admit, the more I read about light, the less I understand 8O

Not wanting to stray to far off point, I've read that time as we know it doesn't count for light. From the light particle's point of view, a trip across the universe takes as long as a trip across the face of an atom. That lenght of time to the light particle is zero. The concept of time is meaningless for a light particle or wave, pick your flavor.

What strikes me is that Jesus said I am the light, maybe a metaphor such as a light at the end of a tunnel, light = hope, etc.

But us humans would not want our supernatural beings to wear a watch, as though they could be affected by time.

BTW, what is time, really. Something that fills the voids in an expanding universe?

Just a thot.

DCR

December 11, 2004 04:39 AM Forum: Religion

Knives and Fire - My Epiphany

Posted By david roberts

I grew up around fire and knives, being a country boy and all. They were part of my young life. Now my son is 11 and has been in cub scouts and now boy scouts. I've never pushed fire and knives on him. Just the opposite. I tend to be a conservation father and preach safety and such.

We go camping a lot and I get the chance to observe about 60 kids or more at these campouts. They come from all backgrounds, cultures, races, religions. I figure they are a pretty good cross section of young males. Their interest and tastes differ but the one thing most have in common is they gravitate towards fire and knives. Some boys will come to the campouts with a pocketful of knives. They become depressed when there is a fire watch due to dry weather and a fire can't be built.

Why is that? Being an amateur student of paleoanthropology, I've read much about homonids/humans in the 200K bce to 5K bce range. The discovered campsites of the early ones all have one thing in common. Evidence of fire and stone tools - as in sharp stone tools.

Then my epiphany - male humans have an inherent fascination with fire and knives for a reason. For hundreds of thousands of years, they have been born and raised around a campfire watching their fathers make sharp stone tools. Over time, the average young male became born with this fascination. Call it instinctive. It didn't happen overnight, but it is engrained still today in their psyche, from birth.

The age of fire and knives is not over. Maybe some day we will advance to the point that fire and knives will fade from memory, and be replaced by something else. But not anytime soon I suppose.


October 23, 2005 01:46 AM Forum: Reflectors

Fan Questions

Posted By david roberts

I plan to install a fan on my old Coulter 13.1 inch, F4.5 reflector. It has a thin mirror. The red tube is 16 inch diameter.

I bought a 3-inch brushless 12VDC cooling fan from Radio Shack ($20) and a battery attachment. My goal is to remove the air layer hugging the primary.

My questions are:

1. Is this fan to big or to small? I tried a 2-inch fan which I didn't think would blow air much to the other side of the tube. Does that matter? Is a 3-inch to much fan?

2. Should I install 2 fans on the tube or is one enough?

3. If one is all I need, I want to install it on top of the tube. Does it make a difference in performance where I install it, i.e. on the side of the tube?

4. Should I install it to blow air over the mirror or reverse it to pull air across the mirror? Would the reverse help with air currents in the tube? By the way, there are three holes in the original Coulter mirror cell.

5. The fan seems to run smooth but do I need a damper between the fan and the tube, like rubber or form?

6. Should I add a fan or two to the back of the mirror cell? Should they pull or push air.

7. How far forward should I place the fan from the face of the mirror.

8. I there an optimum fan arrangement?

All suggestions appreciated

November 7, 2005 12:44 AM Forum: Reflectors

Question about Silicon

Posted By david roberts

I bit the bullet and installed a fan on the back of my coulter reflector. I reinstalled the mirror last night using silicon that is probably a year to 18 months old. It was very hard to squeeze out of the tube, but in my haste to get done I applied it anyways. That was 21 hours ago from the time of this post. It still has not set up properly. It is not sticky but is moldable if squeezed between the index finger and thumb. I haven't removed the supports (stacks of pennies) for fear the mirror will just sink into the hole I cut in the back of the mirror cell. So after all of that, my question is - can silicon get old in the tube and not useful? Should I cut my losses and just go buy a new silicon tube. The work was done at room temperature.

Thanks!

November 14, 2005 04:14 AM Forum: Refractors

Glueing the primary in its cell

Posted By david roberts

I used silicon to hold the mirror in the cell. I used three "dots", and placed the mirror on three sets of pennies (5 each I believe) to hold the mirror off the cell until it dried. After collimation, I'm getting a slight double vision. When I focus on Mars, I see a faint second and sometimes thidd Mars. The faint "reflections" come closer in line with the real Mars but not completely. Is this a collimation problem or have I used to much silicon? Maybe I should have made the silicon dots smaller. After the mirror (13.1 inch) pressed them down at bit, they are about a quarter ($0.25) in size, maybe just a hair larger, and about 3 or 4 mm tall. Maybe just a dab will do you using silicon. Anyone had similar experience?

November 20, 2005 01:44 AM Forum: Reflectors

Pinching, not just for ol' men

Posted By david roberts

I finally caught on to why I was seeing a slight double after I glued my mirror to the sell with silicon. Three dabs on the cell and on the three posts sticking up beside the edge of the mirror. The mirror is very thin, easily less than an inch and 13.1 inch diameter (vintage coulter).

I glue at room temperature and take it outside to cool down, thus the mirror tries to deform slightly based on temperature change but is pinched in the process. I'm starting to believe that glueing the back to the cell is ok, but glueing to the posts is probably a problem.

Does this sound right?

also, is plop in inches or metric?

David Roberts :S

May 1, 2006 01:01 AM Forum: Lost Contacts and Personal Messages

May 7, 2006 03:30 AM Forum: CCD Imaging and Processing/Deep Sky

Re: eeek!

Posted By david roberts

Where did you point to find so many planetaries in one field of view grin

Do you have a one-vane secondary holder. Several of the blobs seem to show a stalk.

November 22, 2006 04:08 AM Forum: Beginning Astronomy?

Help with Observing Chair

Posted By david roberts

I got plenty of lumber and plenty of tools, but no money. I'm looking for a good design for an observing chair I can put together over Thanksgiving. Any help on a website suggestion would be apprciated.

Thanks

David Roberts

January 22, 2007 02:41 AM Forum: Eyepieces

What should it sell for?

Posted By david roberts

I posted a Nagler 9mm Type 1 in the classified on 1/17/2007. Even thought I put a firm price, I haven't even got a nibble. Maybe I'm not checking the correct email. I click on the Message Inbox to the left but no responses. So maybe I'm just a bit optimistic with a price of $190 including shipping insurance and paypal with a 10 day money back. Maybe I misjudged the market and my price is just to close to a used Type 6.

If anyone would care to hazard a guess (or price range) of what a Nagler Type 1 9mm should sell for please let me know, either on the forum or by email. I've searched the internet and can't find comparables for the type 1. I don't want to seem outrageous in price but I'm doing something wrong. I'm feeling pretty ignorant at the moment.

Thanks

david roberts