February 2003 - Utah-Astronomy - mailman.xmission.com

Today's NASA Briefing
by Patrick Wiggins 03 Feb '05

03 Feb '05

Two things of note out of today's briefing. 1) The briefer noted they have received 132 reports of found debris in CA, 130 in AZ and 9 in NM but that none had been confirmed. He made no mention of Utah. 2) The picture mentioned in the Aviation Week article was shown. Some of the media has been playing it up as being "hi resolution". Don't know that I'd call it hi-res but it does show the shape of the orbiter and maybe there's "something" with the left wing but the image is so pixcelated it's hard to say for sure. No doubt the picture will be all over the TV tonight.

6 19

New Saturn Picture
by Siegfried Jachmann 27 Oct '04

27 Oct '04

Joe, I see it the same way and wondered the same thing even before reading your post. The ring is not parallel with the belts. I'm also wondering where the top of the planet disappeared to. Siegfried Jachmann Family History Network Comptroller 801-553-8881

6 9

Re: Auto Find Feature that could still allow for equatorial rotation...
by John Renstrom 03 Mar '03

03 Mar '03

I have been doing a bit of research on the web and noticed that there are some Meade scopes that have what appears to be a wedge mount...I would like to get a scope that could allow for equatorial rotation but still maintain it's auto find features? I am heavily leaning towards a Nexstar 8 or Nexstar 11 for the ease of use and quality...However, I loose the auto find feature as soon as I put it on a wedge. >From all my research over the past few years, I have nailed down my buying decision based on the following priorities: #1 Ease of use (Auto Find Features)...This is absolutely the most important thing because this is my first scope. #2 Quality of image...I want to make sure I don't under buy...I am afraid I might get bored if the image quality isn't very good. #3 Photography...Long term goal. I would appreciate any opinions of other scopes that might meet my needs. Thanks, JohnRen

12 27

Re: [Utah-astronomy] Re: Auto Find Feature that could still allow for equator...
by RStmarie＠aol.com 01 Mar '03

01 Mar '03

I have really enjoyed this thread on go-to scopes. Lots of good commentary from people who really know and care about the hobby (and none of the punches have been below the belt). Right up front let me say, I feel just the way John does about buying a good all around scope; a go-to "piece of schmidt" is exactly the all around compromise I'd make, I even prefer the Meade. That said, I have not bought the scope yet, for some good reasons, even though, as Brent and Rich both have said, the best telescope is THE ONE YOU ACTUALLY USE. It sure is nice to have one (or several) to use and I intend to have one soon. But, Like a friend said, "The best boat in the world ... is the one your fishing buddy just paid for." It sure is nice to have the clubs own the scopes they do. The best astronomy money I ever spend is to join a club and meet the people who have 8" Clark's or 36" Dobs on trailers! The best astro time I spend, next to observing, is learning from these guys and gals. I find it funny that people have anywhere at home to put a scope the length of a pick-up truck bed, or as big around as a trash can. It amazes me people have one scope for planets and another for deep sky, and maybe one for the kids, and several pair of binos. I can't imagine having two or three regular nights off a week to grind a mirror. I barely have time to run out into my backyard with my 15x80 binos and look up for a half hour every other week. I can't imagine tapping the side of a dobsonian for 10 minutes to find a fuzz ball the size of a pin prick just to prove I can do it. But I have friends who do all of this, and I think they're great because they can and do. I'd still like to have that Meade LX200gps in the backyard all to my self.

2 1

RE: [Utah-astronomy] Re: Auto Find Feature that could still allow for equatorial rotation...
by David Dunn 28 Feb '03

28 Feb '03

I would recommend that you find someone who has a high end Celestron GPS scope and visit with them about it. I know that there are two of them in the Ogden Club but I don't know if they are on the this list. I could forward your message to them and you could see what their impressions are. I know that I would be very wary of buying anything from Celestron right now because I have had several bad examples of their low end goto scopes that didn't perform at all. Based on that and the fact that I have seen several nice LX200s that functioned real well, I would buy the Meade unless someone that owns a Celestron can tell me of good performance without having to send parts back for replacement and getting new computer programs. When someone spends a couple of thousand dollars on a product, I think it should work. Let me know if you want me to put you in contact with one of the guys I know up north. Dave -----Original Message----- From: JohnRenstrom(a)Hotmail.com [mailto:JohnRenstrom@Hotmail.com] Sent: Friday, February 28, 2003 2:40 PM To: utah-astronomy(a)mailman.xmission.com Subject: Re: [Utah-astronomy] Re: Auto Find Feature that could still allow for equatorial rotation... Jim Wrote: > One other thought. I bought a Meade 2130 5inch telescope > with Autostar. It cost about $300.00. I would suggest > considering something like this. I believe it would satisfy > all of your (John Renstrom's) criteria. I like playing with the > GOTO and allot of the time I just like pushing the tube > around by hand. I figured if I didn't like the telescope, > I could give it to my son and then I would have a better > idea what I really wanted after my experience with the Meade. I have thought about buying a small cheap version of the nexstar, but as I keep asking people why they are selling these types of scopes, it almost always the same story...they are upgrading. I have several thousand dollars that I am willing to invest into my scope and despite how anxious I am to buy, I enjoy reading and learning more about this field...Also, the prices on this equipment just keep getting better and better... Jim Wrote: > It sounds like, John, you have been looking at telescopes > for a while. If you haven't gone to a Star Party or two > that would be a good move before you actually plunk > down a sizeable investment. Yes, you are correct, I have been reading up on scopes for over 2 years now...I really like to take my time before buying anything...I consider this a very expensive and time consuming hobby and I want to be as prepared as possible before plunging in...I consider myself a very caucious buyer and like to buy for the long-term...As for the star parties, I am very anxious about attending one...I have some friends with scopes, but I think the idea of a bunch of people all draging their scopes out for a party sounds like a total blast! I anticipate I will be that nosy person asking a lot of questions and roaming around mindlessly. To Kim: I my bark sounds worse than my bite...I actually liked what you said...In fact, I think I was replying to Chuck's email more than yours... To Chuck: I know someday it might be nice to roam the stars and to be able to know where everything is...But until then, I must rely on the auto find feature. I don't think the auto find feature is bad at all...I compare it to calculators in the class room...when I went to school, we couldn't use calculators because the teachers felt like the students wouldn't learn how to do the math...Now days, the tests are so complicated, you would be crazy to even try to take a test without a calculator...I just think that the auto find technology is the beginning of more intelligent scopes...Having more intelligent scopes only opens the door for the lazy people like myself...and let me assure you, when I say lazy, I mean lazy! I am so lazy that I am extremely tempted by the GPS unit simply because I don' want to have to care where I set the scope up...I want to plug it in start playing without having to key in any numbers! :-)

4 4

[Fwd: Apogee Inc Review on 25x100's]
by karen vanderhule 28 Feb '03

28 Feb '03

Chuck, In response to your inquiry about the Apogee 25x100s' here is a little info... Ron Vanderhule

4 5

RE: [Utah-astronomy] Re: Auto Find Feature that could still allow for equatorial rotation...
by Kim Hyatt 28 Feb '03

28 Feb '03

Please don't misunderstand - I wasn't trying to be critical. In the long run, any telescope that gets used the most is the best to build or purchase. -----Original Message----- From: JohnRenstrom(a)Hotmail.com [mailto:JohnRenstrom@Hotmail.com] Sent: Friday, February 28, 2003 10:24 AM To: utah-astronomy(a)mailman.xmission.com Subject: Re: [Utah-astronomy] Re: Auto Find Feature that could still allow for equatorial rotation... I appreciate all your responses...It is always nice to get different opinions. > I also agree that "Go-To" mounts do a disservice to > users, in the long run. I must disagree to this comment...The auto find feature is what sold me on finally buying my scope...I have small kids and my wife needs me at home as much as possible...If I am lucky, I might be able to get a few hours a week to spend under the stars. The last thing I want to have to do is drag out a big scope and spend a ton of time setting it up before I can even start . Eventually, I could see me getting more into just wandering the sky, but until I have done the rounds, I need to have an instructor...Thus, my auto find feature that will make me more confident and ensure that I enjoy what little time I have to spend under the stars. > BUT- if someone is only going to take out their > telescope 3 or 4 times a year, has the money to burn, > then buying one of these might make sense. Actually, I view my time as money...I consider it a good investment in myself when I can make my time more enjoyable and more productive. I am also very exited about sharing time with others and being able to quickly show them things through my scope. Especially thos that might not be able to spend an entire evening with me while I scan for specific objects. Eventually I will be more interested in just roaming the stars...Just because my scope has an auto find feature, doesn't mean I have to always use it. My priorities remain the same... #1 Ease of use...It needs to be compact, easy to set up and capable of taking me for a tour of the night sky... #2 Image quality. #3 Photography. _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy

1 0

Go-to scopes
by Kim Hyatt 28 Feb '03

28 Feb '03

I agree entirely with Brent (almost). There's no way one will learn the night sky without spending time star-hopping - with planisphere and unaided eye, binoculars, or a telescope. An added benefit is the myriad treasures one happens upon quite by chance while one is hunting a specific target. A couple years ago I came upon, quite by chance, a fabulous deal on a Celestron Ultima 2000, a "go-to" model capable of both alt-az and equatorial operation. I bought the scope mainly for it's optical quality but also for use at public star parties. There are two advantages for me: the scope is lighter and more compact than either of my Newtonians and I can more quickly find objects so that people waiting don't get bored and go away. "Oh, you've never seen a quadruple star? Well give me 30 seconds and I can show you one." I still use my Newtonians or my refractor for serious personal observing. Except for these and maybe other marginal advantages, I find that the go-to phenomenon is gimmicky and discourages beginners, especially, from simply scanning the sky to see what one may find. I am especially puzzled why the manufacturers promote their GPS models over all others. After all, how much trouble is it to align a scope on a couple of stars? Kim A. Hyatt, AIA SL&A Architects 331 South Rio Grande, Suite 304 Salt Lake City, Utah 84101 801.322.5550 x122

2 1

Goodwin Mask (long)
by Marilyn Smith 28 Feb '03

28 Feb '03

In tune with the recent discussion about mirrors, I'd like to pose a question about off-axis masks. During the course of reading about telescope designs and modifications, I have read about modifying Newtonians with offset circular masks of roughly 40% of the primary mirror's diameter to reduce diffraction and increase the effective focal length, and about curved spiders to reduce diffraction effects, but nowhere else have I encountered the type of mask that I will discuss below. I hope it may prove beneficial to others, and provoke some discussion. Is this a now discredited concept, or does it have merit like my own experience would suggest? I have copied at the end of this email the text from "Helpful Telescope Hints for Observers" by Frank L. Goodwin. This text came to me along with other paperwork accompanying the 1956 8" Cave f/5.84 that I inherited, but it evidently had been printed in S&T in 1954 or 1955 (see below). (BTW, old issues of S&T and Astronomy are in the stacks at the U of U.) Other correspondence between Mr. Goodwin and the telescope's original owner indicate that my adjustable Barlow was also made by Mr. Goodwin. He appears to be a credible source. Briefly, the Goodwin Mask is a black paper cutout that is taped onto the primary mirror. This cutout matches the shape of the combined secondary and spider, but is 1/4" wider all around the secondary and 1/4" wider on each side of the spider's struts. The concept is that you can improve the image by "throwing away" the light affected by the diffraction of the secondary and spider. Further description of this is in the text at the end of this email. My first attempt at this a couple of years ago appeared to be ineffective, so I removed that mask. But in a recent attempt to dismiss any temptation to buy a new scope, I decided to "hotrod" my existing Cave to make it more easily portable, precise and user-friendly while keeping it as close to original as practical. It was quite neglected and abused when I got it. My first experiment was with a single quadrant offset mask at the "top end" of the scope. This didn't allow any light to pass the secondary and spider, increased the effective focal length, reduced the light gathering by about 75%, but gave much sharper views of Saturn, Jupiter, and the limbs of the pine trees on Mt. Olympus above my house in East Mill Creek. Let's call the unmasked mirror "A". And let's label this mirror with offset masked as "B". View "B" is better than view "A". This success led me to make a new Goodwin Mask, but since installing it required removing the primary mirror and then replacing it in somewhat oversized holes in the aging fiberglass tube, it required recollimation. Let's label the mirror with the Goodwin Mask as "C". Due to the time required for this modification, it was not possible to directly compare view "A" with view "C". However, since mask "B" could be removed in less than a second, I could easily compare it with both "A" and "C". It is hard to tell much difference between view "B" and view "C", even though the focal lengths are different. This could lead me to conclude that "C" is also better than "A". Except for the fact that I also just began using a Cheshire collimating tube, and may have collimated the optics better than ever before, and this might attribute to the improved view. Nevertheless, I'm leaving the Goodwin Mask on the primary because Saturn and Jupiter have never looked sharper, it is historically accurate to the period when the scope was made, light loss is minimal, and it evidently doesn't degrade the image. (BTW, I was in the southern Nevada desert a year or two ago and was able to read a sign on Interstate 15 from 9 miles away, even though I was at about a 45 degree angle from it.) I welcome any comments about the Goodwin Mask concept, why I've never encountered it anywhere else, and from anyone else who may give this a try. Bob Grant The text from Mr. Goodwin follows: How a Patterned Strip of Paper Laid on the Mirror can Transform any Reflector into an Off-axis Telescope. An off-axis reflector is one in which the light coming from a sky object is not obstructed by the Newtonian diagonal or its struts, - thereby avoiding diffrac- tions of the latter. A Newtonian diagonal and its struts produce two types of diffraction of light reaching the mirror's surface. One diffraction is caused by obstruction of the light, - the other is the 'temperature diffraction' when the diagonal and struts are slightly colder or warmer than surrounding air inside the tube, - this temperature differential warps the incoming light passing by in close proximity to the edges of these surfaces. Because of this temperature factor it is necessary to make a metal tube of the reflector 3/4 inch between the edge of the mirror and the inner wall of the tube, or 1 1/2 inch total inside diameter of the tube wider than the diameter of the mirror. This wider diameter of the tube also helps to lessen tube wall currents from distorting finest details of the mirror. The effect of these two diffractions is seen on stellar photographs by large observatory mirrors, - both right angled crosses of light around bright stars, and circles of light from tube diffractions enclosing the crosses. Now have you noticed the phenomenon in a telescope, any size, when a tree branch or twig is in the path of light coming from the star into your telescope? The obstruction of the tree twig causes a star obstructed by it, to appear as a string of multiple stars on each side. The farther away the tree twig obstruction is, the greater is this multiple star diffraction effect. While usually in amateur reflectors the Newtonian diagonal and its struts are too close to the mirror to exhibit this ' interference' phenomenon, - it exists anyway with the result of detracting from maximum sharpness of detail. To prevent these diffractions of Newtonian diagonal and struts from reaching the mirror's surface to be reflected back to the diagonal and eyepiece, confusing the image by mixing in with the pure unobstructed light from the sky object, we simply do this: We place a paper pattern right on the mirror to mask off these diffractions. The paper pattern (black paper) represents the 'shadow' cast by the Newtonian diagonal and its struts on the mirror, only you cut the pattern 1/4 inch wider all around than the diagonal itself and Â¼" on each side of the strut (4) 'shadows'. Care must be taken to have the paper pattern exactly where the diffraction falls on the mirror, not carelessly to one side of the occluding strut and diagonal structure. True, by this pattern masking off the diffractions right on the mirror itself, you lose a little light gathering area, but it is confused (diffraction) area you can well afford to get rid of. To properly collimate the paper pattern to the strut and diagonal 'shadow' on the mirror you should have a motor drive to follow the stars. Then point the reflector directly at the Sun, - ascertained as squarely direct by a white cardboard at the base of your telescope tube, which shows when the Sun is optically squared sufficiently to make the pattern. Or if your finder is accurate, it will do. Place a white piece of paper on the mirror, anchored to the sides of the cell by scotch tape. Note the Sun's shadow of the diagonal and struts on the white paper over the mirror, and make the pattern wide enough to occlude the slight 'blurring' on each side of the struts, and outside of the diagonal's shadow. Your telescope tube necessarily should have a hole near its base to draw an outline of the pattern, before cutting it out with black paper for permanent use. Otherwise look down the barrel of your tube, and with the pre- pattern white paper marked with suitable lines, you can note between which lines the limit of the "blur" occurs, caused by the Sun's disc shining down from all sides of its limb, - a sort of 'penumbra' effect, - which will amply suit for lesser extent of star and planetary diffraction spreading, and equals the Moon's effect, due to lesser brightness of the Moon, and near comparable visual solar disc. Anchoring the resulting black paper pattern on the mirror with scotch tape on the mirror or cell sides, you are all set. The reason for the paper right on the mirror's surface is to minimize the distance from the pattern's edge to the mirror's surface, since the paper's edge would interpose diffraction were it as far away from the mirror surface as the diagonal and struts are. The theoretical diffraction from a mirror's circular edge to the eyepiece has been grossly over- rated, - for which reason regular 'one-sided' off-axis mirrors are circular with an idea of minimizing the diffraction from mirror edge. But here with the paper pattern you need not have circular areas on four sides, since by having them as 1/4 'slices of pie' in shape, the gain in light gathering area far offsets the impractically insensible paper edge diffraction going back to the diagonal and eyepiece. There being no sensible distance between the paper pattern and the mirror's surface to multiply any diffraction effect. By this paper pattern method, known to one large observatory as the "Goodwin Mask" planetary, lunar, etc details come out so remarkably on nights of minimum atmospheric turbulence, as to make one fairly 'gasp' in astonishment. Here is an off-axis mirror, all around, instead of on one side, - in which the light coming from a celestial object does not strike an obstruction of diagonal and strut to cause a 'diffraction shadow' on the mirror. All four sides of the pattern receive the light unobstructed by a Newtonian diagonal and its struts. Space does not permit legions of other instrumental and observational techniques found in my 53 years of observing since a kid, - but trust the foregoing may prove of some interest. Frank L. Goodwin, ScB., (Vice President Chicago Burnham Astronomical Society). The 4 HELPFUL HINTS were printed in Sky & Telescope Magazine in Dec. 1954 and Jan, Feb., March 1955 issues)

5 13

RE: [Utah-astronomy] Goodwin Mask (short)
by David Dunn 27 Feb '03

27 Feb '03

I have put curved spiders on three of the four telescopes I have built. I think that it is easier to build the curved spider than to built a vaned spider. I think that I understand the concept of the mask that sits on the mirror. How do you get it lined up on the mirror correctly? It would seem that if you didn't get it just right it wouldn't work. Dave -----Original Message----- From: David L Bennett [mailto:dlbennett@mac.com] Sent: Wednesday, February 26, 2003 11:10 PM To: utah-astronomy(a)mailman.xmission.com Subject: Re: [Utah-astronomy] Goodwin Mask (short) Brent/Bob, Is it possible that because the mask is, essentially, touching the mirror there is not the diffraction inherent with the spider and secondary obstruction? I mean, yes, there is a larger obstruction but isn't that obstruction basically diffraction free because of it's proximity to the mirrors surface? I would think that would be the only reason to place it upon the mirror as opposed to above the secondary mirror/spider where an aperture stop or apodizing mask normally would be placed. David Bennett On Wednesday, February 26, 2003, at 10:02 PM, Brent Watson wrote: > Bob, > > This is an interesting idea, but I don't see that it > would make the view any netter. The mask still acts > like the spider, and in fact is worse because it is > wider. It MAY get rid of the temperature effects > mentioned in the article. I would be scheptical about > it working, and would have to conduct several careful > tests to see if it made an improvement. > > Brent _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy

2 2