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Posts Made By: Stu Lieberman

February 18, 2006 08:39 PM Forum: Telescope Making

Homemade $10 Tripod for 200 pound binoculars

Posted By Stu Lieberman
This is MUCH sturdier, steadier, and cheaper than anything I have come across.

It can adjust from a 30 degree leg angle to 45 degrees.

Don't try it at home.

Stu

February 19, 2006 11:53 PM Forum: Beginning Astronomy?

A Few Basic Questions

Posted By Stu Lieberman
A Few Basic Questions

I have a 63 year old pair of B&L 7x50's individual focus. They are marvelous binoculars, bright, and sharp.

There is a hinge assembly between the 2 OPA's to swing them for IPD adjustment.

What happens to the image when you swing the OTA's?

Is the convergence affected?

Is the collimation affected?

Is there an angle of swing beyond which the image would not look upright?

My reason for asking these questions is that I am designing a bi-Newt based on a pair of Meade 114NT's.

I wonder what needs to be adjusted for convergence and whether a pair of Newts whose eypieces face each other can achieve a correct image?

Stu

February 19, 2006 11:54 PM Forum: Telescope Making

A Few Basic Binocular Questions

Posted By Stu Lieberman
A Few Basic Questions

I have a 63 year old pair of B&L 7x50's individual focus. They are marvelous binoculars, bright, and sharp.

There is a hinge assembly between the 2 OPA's to swing them for IPD adjustment.

What happens to the image when you swing the OTA's?

Is the convergence affected?

Is the collimation affected?

Is there an angle of swing beyond which the image would not look upright?

My reason for asking these questions is that I am designing a bi-Newt based on a pair of Meade 114NT's.

I wonder what needs to be adjusted for convergence and whether a pair of Newts whose eypieces face each other can achieve a correct image?

Stu

February 21, 2006 12:50 PM Forum: Eyepieces

A few questions about Barlows.

Posted By Stu Lieberman
A few questions about Barlows.

What does a 2x barlow spec mean with respect to its focal length?

In your example above, the barlow is not in contact with the EP. Once you fix the barlow is there a unique position to focus the EP?

Assume for example, I would like the fp to be 12" outside the tube and I could buy a negative lens with a fl of 12".

Would that do it?


Is there a lens program that you could recommend?

Thanks,

Stu

February 22, 2006 02:42 PM Forum: Eyepieces

Barlow questions

Posted By Stu Lieberman
1> If a Barlow lens is rated at 2x what is its focal length?

2> Are there different fl for 2x Barlows?

2> What is the relationship between fl and power?

February 23, 2006 03:37 PM Forum: Beginning Astronomy?

Local 'Darkness'

Posted By Stu Lieberman
In the olden days of photography, the photographer would place himself under a black curtain in order to focus the scene on the focusing glass.

Why don't we do it?

Stu

February 24, 2006 03:12 AM Forum: Telescope Making

Give me a brake (idea)

Posted By Stu Lieberman
Give me a brake (idea)

I have a pipe Alt/Az mount based on a pipe 'T'.

While observing tonight I had some annoying slippage.

The bulb went off at that point. Why not use a pair of brakes on 2 ends of the 'T'?

I even might consider an electric clutch brake. Press a pushbutton to release, aim, set the brake.

All ideas welcome.

Stu

February 27, 2006 03:27 AM Forum: Beginning Astronomy?

Daytime collimation test.

Posted By Stu Lieberman
My Meade 114NT was completely out of collimation after I replaced the focuser.

I used a film can pinhole to collimate it and I viewed a licence plate sticker 84 feet distance. I could easily read 1/8" numbers and could almost read smaller numbers.

Is this test a reasonable performance test prior to viewing a star out-of-focus pattern?


February 27, 2006 10:19 PM Forum: Beginning Astronomy?

What is that 'eyebrow' image around the diagonal?

Posted By Stu Lieberman
What is that 'eyebrow' image around the diagonal?

I am just learning to collimate my Meade 114NT f/8 910mm.

After using the 35mm film can and when everything looks lined up correctly, it appears that the diagnonal is too small because a little shiny 'eyebrow' appears on 2 parts of the circle.

What am I seeing, is it important, what should I do?

Stu

March 2, 2006 04:34 PM Forum: Beginning Astronomy?

What magnification do you use the most?

Posted By Stu Lieberman
What magnification do you use the most?


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