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Posts Made By: David Simons

November 28, 2007 06:17 PM Forum: Equipment Talk

Whats the worst scope you had?

Posted By David Simons

Hands down it was a 50mm scope with a plate glass singlet lense about f30. The eyepieces were also singlets, so chromatic aberration was an abomination. The tube was a mess of glued together cardboard, and the mount was so undersized, it was originally designed to hold a small surveyors leveling telescope. The whole thing shook like a leaf in the slightest breeze.

But hey, I made it myself when I was in grade school, and it showed me the rings of Saturn, the moons of Jupiter, and the true face of the moon for the very first time.

Yep, truly the worst scope I have ever had, and I absolutely loved every minute using it.

smile

[SIZE="Small"]
[[COLOR="Blue"]QUOTE]Charles Peterson said:

Ok guys and gals,

We just did a thread on the most perfect scope.
So what is the worst scope you have owned?
Bad optics, mount, or other is fine.

Chas[/QUOTE][/COLOR][/SIZE]

November 28, 2007 06:27 PM Forum: Equipment Talk

Telrad flasher schematic

Posted By David Simons

Hi Ken,

Chances are it was based on the CMOS version of the 555 timer IC chip.

Here is a link to the operation:

http://www.eleinmec.com/article.asp?3

It is a bit technical, but the equations are there to determine the pulsing rate you might want. The Telrad LED would hook up to the output pin 3 of the IC through the dimming resistor on the Telrad.


February 3, 2008 11:09 PM Forum: Antique/Classic/Vintage Optical Instruments

Tinsley Cassegrain type

Posted By David Simons

Hi Robert,

Thanks, exactly what I as looking for ! Great collection of old literature.

I like Tinsley's slogan for their 8 inch, "A star is born"

wink


Robert Provin said:

Take a look at:
http://geogdata.csun.edu/~voltaire/classics/tinsley/tinsley2/tinsley2.pdf

On page 7, Dall-Kirkham is given as the type for the 8 inch.

April 4, 2008 05:10 PM Forum: Deep Sky Observing

This forum

Posted By David Simons

Inge,

I plan on introducing a few co-workers to the "Messier Marathon" this weekend.

I'll post a report later this week.

April 12, 2008 10:56 PM Forum: Astro Binoculars

Building a binoscope

Posted By David Simons

Hi Paul,

I believe Vixen has reintroduced their 125mm binoculars.

April 14, 2008 07:01 PM Forum: Telescope Making

making the secondary diagonal

Posted By David Simons

Hi Bill,

Looks like you've pushed some glass before smile

There are a couple of ATM books that talk about the 3-plate process for making a flat, I can look it up if nobody else remembers wink (Allen Thompson?) I recall in the old TM magazines several folks had some luck with it.

If you start with the plate glass already polished, then after you have done your cutout you can use the cross polarizer to check for strain in the glass. Remember LCD screens give off polarized light, so you have one, or a laptop, a white screen will give you 1/2 of your solution. Put your glass to be tested in front of the screen, and look at the glass with the polarizer and roate the polarizer. Try this with other glass, or plastic first to get an idea of what this looks like.

If your glass appears a uniform gray, you should be good to go if the glass is reasonably thick.

Don't forget "Surplus Shed" as a source of glass. They have all sorts of glass blanks and windows/filters and finished flats (for testing) that might work for you.

[COLOR="Blue"]
Bill Wheaton said:

I'm giving serious thought to making my own secondary. Grinding and figuring it using the 3 blank method.

I have heard that since it's for flats, that using plate glass is adequate.

I have also found out that people will sell just about anything on Craig's List including old glass coffee tables, some with 3/4 inch to 1 inch plate glass on them. I have no idea about the annealing on them, but for $50 for a huge amount of plate glass, I'm wondering if I should take the gamble? Maybe a small enough portion of the glass is ok?

How do you test that? I heard of using polarizers somehow.

What do you all think?

Of course after I make the blank, I have to core it at 45 degrees, using something in the 2.1 to 2.7 inch range. I went to Lowes today and found a hole saw that might work. But if I make my own, how would I do it?

Thanks for your ideas on that.

-Bill Wheaton
[/COLOR]
Decatur GA

May 9, 2008 12:02 AM Forum: Equipment Talk

Whats Up with These Huge Refractors

Posted By David Simons

Hi Steve,

An 8" f6 is pretty easy to handle. Most folks don't even think it's a refractor when they see it in the dark.

Steven Cotton said:


Gee ... I must be behind the times ... I see a lot of 6", 7", 8" refractors in the group I hang around with. A 7"/f9 isn't all that bad to transport around -- you just need to be tall to get it on the pier.

July 14, 2008 01:10 PM Forum: Refractors

Large Aperture Refractors for Visual

Posted By David Simons

Hi Larry,

Nice to hear from another fellow inflicted with refractoritis. (sp?)

I am getting close to finishing my 8" f10 achromat OTA (Ukraine Lense) with first light this last weekend. Lots more to do, baffling. flocking, choosing paint color etc. I designed the lense mounting cell to be removable from the OTA end plate flange. I have captive thumbscrews on the tube flange, and guide pins on the lense cell so re-mounting is repeatable. For transport the lense and focuser are removed, with the empty tube length less than 5.5ft long, and ~20 lbs, fairly easy to manage. However fully assembled the tube is at 6 feet, and shy of 50 lbs which makes for somewhat of a beast. (note: Blonde assistant also wanted to help clean the lense)

As you know, the needle sharp pinpoint stars are breathtaking.

Finally saw the three larger craterlets in Plato without much trying.

Jupiter was still boiling being low on the horizon, but the mottled subtle detail on the polar regions was very satisfying. (Pentax SMC 9mm)

I also have a short tube 8" f6 doublet which gives beautiful wide field views. The Veil, Double Cluster, dark nebula, Milky Way, Virgo Galaxy clusters, and of course Sagittarius region all are awesome targets.

I liked the 8" so much, I am in the process of having an 11" f8 refractor lense quoted. (remove common sense here) I can send you some details if you want. They want a hefty tooling charge, but if they make more than one lense, it would be much cheaper.(hint hint). I would also plan to have this a portable instrument.

Also I know someone who has a 10" f9 fluorite triplet lense if your need is serious ; )

PS. In your link, it was interesting to see how they placed the pack of cigarettes onto the lense for scale - yipes !! Any idea how much the lense finally sold for ?

July 14, 2008 11:01 PM Forum: Telescope Making

Another 8in Refractor

Posted By David Simons

And another shot

July 15, 2008 07:30 PM Forum: Equipment Talk

Mirror refigure

Posted By David Simons

HI Larry,

Check out Alan Raycraft's info near the bottem of my webpage. He used to do smaller mirrors for Starsplitter years ago IIRC.

http://www.planetatm.com/