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Posts Made By: Bob Chester

March 4, 2007 06:47 PM Forum: Bad to the Bone Autos

Dream Cars You May Actually Buy

Posted By Bob Chester

I like your list.
This one is on my list. Environmentally friendly with performance and styling.
http://www.teslamotors.com/index.php?js_enabled=1

Sold out for 2007 models but taking orders for 08'.

Bob

March 25, 2007 12:04 AM Forum: CCD Imaging and Processing/Solar System

first saturn of spring

Posted By Bob Chester

SUPERB work Alan. Thank you for sharing.

Bob

April 29, 2007 03:22 AM Forum: Telescope Making

Focal Plane Placement

Posted By Bob Chester



Stuart St. Clair said:

NEWT recommends placing the focal plane at 1/4" below the top of the focuser when fully racked in.

I know it's really late but this sure sounds wrong to me.

Are you sure it didn't say "when fully racked out"?

In theory the field stop of an eyepiece is located at the focal plane of that eyepiece. So, when the field stop hits the focal plane of the scope it should be in focus. Most Televue eyepieces have the field stop 1/4" below the shoulder (where the barrel meets the body).If you put the focal plane of the scope 1/4" below the top of the focuser when fully racked IN these eyepieces will barely (if at all) come to focus only when the focuser is fully racked in. Some eyepiece makers try to put the EP focal plane at the shoulder. These EPs will not reach focus.

This is how I've done it with good results. I take my eyepiece that has the field stop furthest below the EP shoulder and design the scope to focus that eyepiece 1/4" below the fully racked OUT position.
It might be easier to say: [SIZE="Large"]put the scope focal plane where all your EP field stops can meet it[/SIZE].

Of course there are all kinds of variables and considerations. Like if you plan to attach a 35mm camera then you need to put the focal plane a good 2" above the fully racked in position. Or, if all you own are TV plössls and Radians you can put the focal plane at the top of the fully racked in focuser. If you own a TV 55mm plössl and a 31mm Nagler you will need over 1-1/2" of travel between the 2 extremes.
Sorry, its really late and I'm rambling. Maybe someone else will chime in and put it more simply than I have.
Bob

April 30, 2007 06:32 PM Forum: Telescope Making

Eyepiece Focal Plane

Posted By Bob Chester

The field stop is usually located at the eyepieces focal plane.

June 4, 2007 10:55 PM Forum: Beginning Astronomy?

Anything else I'm missing?

Posted By Bob Chester

Mark,
With no finder, a photo tripod, and only the 3-6 zoom you may be a bit frustrated tonight but please don't get discouraged. The 32mm plössl and Porta mount will make a world of difference.

"What else do I need?"

I would recommend a simple red dot finder and some star charts.
You have the high power covered with the 3-6 zoom and the wide field milky way sweeping will be covered when the 32mm arrives. If the scope is to serve double duty you will probably want somthing between that 15-80 power range. I think the soon to be released TV 13mm Ethos would be a very nice fit......it's fun spending someone elses money.

Bob

July 8, 2007 09:55 PM Forum: Off Topic Discussions

Severe Vignetting?

Posted By Bob Chester

A standard fireworks photo from the 4th.

July 14, 2007 11:23 PM Forum: Equipment Talk

Re: Need a dingus thingamabob....

Posted By Bob Chester

If you can do with pulling...a fish scale should work well.
http://www.dickssportinggoods.com/product/index.jsp?productId=967920&cp=2291549&sr=1&origkw=fish+scale&parentPage=family&searchId=2291549

Bob

August 22, 2007 07:52 PM Forum: DVDs and Music and Books That You Recommend

Best Science Fiction Movie?

Posted By Bob Chester

Your avatar is my favorite. Maybe because I saw it several times when it first came out. I was 15 and it was a spiritual experience to see it on the 'real' big screen in a 'real theatre in 70mm format.

Ana

August 15, 2008 12:59 AM Forum: SCI-FI

October 20, 2008 03:44 PM Forum: Telescope Making

Packing a large Mirror for shipment

Posted By Bob Chester

This is the method I use.

http://www.spectrum-coatings.com/Telescope-Mirror_Packing.htm

Hope it helps.

Bob