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Posts Made By: Larry Thaxton

October 28, 2004 07:21 AM Forum: Equipment Talk

Seeing Encke

Posted By Larry Thaxton

There are several references to observations of Encke's divison in A.F.O'D.Alexander's "The Planet Saturn: A History of Observation, Theory and Discovery" among those mentioned:

Captain Henry Kater did most of his observing with a pair of Newtonian reflectors, a 6 1/4" F/6 and a 6 3/4" . On 17 December 1825 "the conditions were very favorable: no wind and a very slight fog. With the larger reflector (6 3/4") he saw a very distinct image but nothing unusal, but with the 6 1/4-inch Watson and his most perfect single eyepiece (power about 280)....'I fancied that I saw the outer ring separated by numerous dark divisions, extremely close, one stronger than the rest dividing the ring about equally...'

On 7 September 1843 W. R. Dawes viewed Encke's through a 9" reflector belonging to W. Lassel- "I presently perceived the outer ring to be divided in two.....The outline of the planet was very hard and sharply defined at a power of 450; and the primary (Cassini's) divison...very black and steadily seen all around the southern side." At 400x he could glimpse Encke's but could not see it at all at lower power.

On 25 November 1850 Dawes was armed with a 6 1/3" achromat of "very fine" quality. Using powers of 282 to 425 "Dawes ... was satisfied that in finest moments, a very narrow and short line was discernible on the outer ring near it's extremities."

On November 29: "having applied higher powers, and viewed the planet steadily for a considerable time, I obtained several satisfactory glimpsesof a division near the extremity of the outer ring. It was occasionally seen with power 323; but far more certainly with 460."

On 26 November 1854 Dawes, using a 7 1/2" achromat, described Encke's as " a very dark, narrow, well defined line concentric with the ring, and about one-fifth of it's breadth."

In 1852 W.S. Jacobs appears to have observed Encke's division with a 6.2" refractor at Madras Observatory at a power of 365.


October 30, 2004 11:36 AM Forum: Equipment Talk

Pentax 40 XW?

Posted By Larry Thaxton

HI Ed,

I own the 40mm XW and find it to be an excellent performer in everything- a 10" F/5 Portaball, FS-152 Takahashi, 12.5" dobson and an 8" F/12 D&G. Feel free to e-mail me re: questions.

ltha379@aol.com

November 5, 2004 07:19 AM Forum: Equipment Talk

Dobs Dobs Dobs!

Posted By Larry Thaxton

Hi David,

I am no expert on plate glass v. pyrex in the temperatures you mentioned but you can get pyrex in Discovery scopes. Their site mentions that they make all of their mirrors, I am sure a call to them would clarify that.

Mirror quality- as I write this I have just received my second Portaball scope- this one a 12.5" with Zambuto optics(the only optics Mag 1 currently uses). The first PB was a 10" also with CZ optics. I also have a Discovery 10" DOB picked up for a friend's kids that has a plate glass mirror and can tell you that it compares very favorably on deep sky with the best of the best. I was suspicious of plate glass until I set the Discovery up and hit M13- stunning pin-point images. On planets and under excellent seeing the 10" CZ was better at rendering fine detail and had better contrast (especially Jupiter's more subtle markings), but it is closer than one would think, especially if cost is a factor.

Floyd is right on when he mentions that the optics are only part-albeit the biggest part- of the consideration that goes into a scope. The Discovery I have is the 10" F/5.6 DHQ and it is "serviceable" as far as the base and bearings. The motions are quite sticky and abrupt which comes into play during high power planetary viewing. I have read how to fix the problems and it sounds easy enough.

Rob Teeter put together a "Planet Killer" structure for a 12.5" Meade Research Grade mirror I owned and his work was absolutely first rate and the scope a pleasure to use. All conventional DOBs I have used suffer near zenith when trying to track an object by hand. Not so with the Portaball which moves equally smoothly in every part of the sky. The Portaball is the most impressive scope I have owned as far as ergonomics and quality- and optics. Collimation is easy, transportation a breezy and Peter Smitka is a match for anyone out there in terms of being genuinely interested in his "family" of scope owners being happy. Limits- forget DSCs and "goto" servo drives (though an equatorial plarform works perfectly with PBs).

November 14, 2004 05:35 PM Forum: Equipment Talk

Staying warm

Posted By Larry Thaxton

One for the APO crowd:

http://www.mgear.com/pages/product/product.asp/level1_id/56/level2_id/75/level3_id/76/item/102218/level2_title/Men%27s+Technical+Wear/level3_title/Down+and+Insulated+Tops

November 25, 2004 06:55 AM Forum: Equipment Talk

Rukl's Atlas of the Moon, 2nd edition

Posted By Larry Thaxton

I find this to be a very useful addition to lunar studies. The plastic laminated version is quite durable.

http://scientificsonline.com/product.asp?pn=3004598&bhcd2=1101394578

December 29, 2004 08:40 PM Forum: Refractors

MILO refractor?

Posted By Larry Thaxton

Here area couple of images of the scope in question. We are in the midst of a series of rain storms here in So Cal which means I will have time to finally set th scope up but won't be able to use it quite yet!

December 31, 2004 12:08 PM Forum: Refractors

MILO refractor?

Posted By Larry Thaxton

Since it is raining to beat the devil I had time to set the Milo refractor up this morning. Not the best background for pictures but....

April 7, 2005 05:32 PM Forum: Equipment Talk

Wanted: Opinions on an exceptional planetary scop

Posted By Larry Thaxton

Hi George,

I am primarily a visual planetary observer and have been looking for the optimal planetary scope as well. To date my favorites are a 12.5" Portaball with Zambuto optics, an Astro-Physics 6" F/12 Superplanetary and a D&G 8" F/12. If I had to pick one it would be the Portaball. The images of Saturn it has provided are simply amazing. I definitely like the Portaball design, especially at and near zenith, but the optics are the real key. Any of the high end DOBs would be great!

May 12, 2005 09:25 PM Forum: Refractors

3 Apo vs. 4 Acro

Posted By Larry Thaxton

I have owned both and would take the 4" achro as F/12 or slower, especially for planets. It will not be a "grab and go" scope especially with an adequate mount. My current grab and go-a TV85. An old Jaegers 4 1/8" F/15 is an all-time favorite too!

June 28, 2005 04:22 PM Forum: Takahashi

FS-78,FC-76, FCT-76

Posted By Larry Thaxton

Hi David,

I am not sure I understand the question- do you mean a place you could physically compare the three, a website review or comments from others on performance? I actually owned all three at one time or another.

Larry