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Posts Made By: Bill Barrett

May 2, 2004 02:17 PM Forum: Equipment Talk

Filter recommendations for urban viewing?

Posted By Bill Barrett
Although I live & do my viewing several miles north of downtown Seattle, between the light pollution and the particulate matter in the atmosphere, the sky has become a grey, contrast robbing haze rather than a black backdrop.

My interests are both planetary and DSO observing. Are there any filters which are especially effective under these conditions? thank you, Bill

May 4, 2004 01:23 PM Forum: Telescope Making

Homebuilt 4" F15 scope & shadow transit

Posted By Bill Barrett
The other night we had a break in the Seattle cloud cover. So, I pulled out the recently put together Jaegers 4" F15 and pointed it at Jupiter. At first I thought it would be a ho hum evening. The atmosphere was not stable, and there was some particulate matter in the air. A 10.5 mm plossl produced a good image size. The polar regions and bands were quite evident, and there was a black dot just inside the limb. I couldn't believe how exciting it was to follow a slow moving black dot millions of miles away, I stayed with it for the rest of the evening. Later I checked a website and found it was Ganymede. Very cool!
I'll just catch those reruns of Law and Order some other time.

May 20, 2004 12:31 PM Forum: Equipment Talk

Chromacor or minus violet filter?

Posted By Bill Barrett
All of us with achros experience varying degrees of chromatic aberration. Interference filters block the unfocused blue/violet light. The chromacor focuses the blue/violet light. Will (a properly matched) chromacor offer a meaningful improvement in the ability to resolve planetary detail over a preimium quality filter? I know it is difficult to quantify & there are variables. Could it be as much as the difference between being able to resolve the GRS or not...or being able to resolve the encke minimima?



May 30, 2004 10:25 PM Forum: Telescope Making

Black wool felt instead of flocking paper?

Posted By Bill Barrett
I have a 6" refractor which needs to be relined. I want to make it as dark and non reflective as possible. I was wondering how black wool felt would work rather than flocking paper?

June 14, 2004 12:51 AM Forum: Telescope Making

Refractor Problems...what have I done?

Posted By Bill Barrett
I have an old 6" F8 jaegers refractor. Recently I took the scope apart, had the tube cut down & added an astro physics focuser, flocked & baffled the inside of the tube, & had the lens taken apart & cleaned.
I just put it back together today, and everything looks like it is under water! There is maybe a small area in the center of the field which is almost in focus...but the rest of the field is a mess. I tried reversing the crown...no luck. I don't anything could be that badly out of collimation to cause this. This is really bad! I'm wondering if it couldn't be a spacing problem between the crown and the flint?
Any ideas would really be appreciated. thank you, Bill

June 20, 2004 03:43 PM Forum: Equipment Talk

Baffling & flocking do make a difference

Posted By Bill Barrett
The original builder of my old 6" f8 refractor baffled & blackened the tube by placing two 5 1/2" rings near the center of the tube, and spraying the inside with a not quite black primer. As much as I liked the scope, I always felt the background could be darker. Having recently purchased an AP 2.7" focuser, for it, I decided to repaint the outside, baffle and flock the inside.
The baffling and flocking made an immediately apparent difference in the contrast: The backgrounds are now ink black and the image almost pops out of the scope. It was definitely well worth the effort.

P.S. With the Ap focuer there is no more fumbling for pretty good focus. That doesn't hurt things either. Bill



July 24, 2004 05:10 PM Forum: Equipment Talk

Advice on collimating refractors?

Posted By Bill Barrett
I need to collimate a 6" refractor which I have just built a new tube for and does not have an adjustable cell.

Please advise me if I'm wrong, but I think collimation will involve first being sure the focuser is square. Then once that is done, I would proceed to make sure the ojective is square.

I planned on using a laser collimater for this process. I would first square the focuser by using a paper template over the lens with a hole dead center. If the light passes through the hole, we are good.

Next to square the ojective I would use the collimator with the dew cap on and check the reflection. I would adjust the cell until there was only one centered beam.

Does this sound correct or have I not thoroughly thought the process through?
thank you, Bill

August 2, 2004 01:23 AM Forum: Equipment Talk

Why do Stars & lights look like asterisks not disks?

Posted By Bill Barrett
I was looking through my neighbors old 6" f10 refractor and noticed stars looked like little asterisks. Brighter stars looked like bigger asterisks. Outside focus produced diffraction rings but inside focus became a big blurry asterisk. Any ideas what might be causing this?

October 3, 2004 02:23 AM Forum: Equipment Talk

Using a Pronto @ F23?

Posted By Bill Barrett
I was reading the manual today, and it said if we use a 2x barlow, and a 3" extension, the Pronto would be operating @ F23. Has anyone tried this? Would it really work as a small planetary scope at that point?

October 3, 2004 05:27 PM Forum: TeleVue

Powermate does it require an extension?

Posted By Bill Barrett
I have been reading about powermates vs barlows and I'm still a bit unclear of the practical difference.
Does the use of the powermate eliminate the need for the use of an extension tube to achieve focus?

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