ATM session report and next planned date
We had a great ATM session on Saturday. Charlie, Jay, Joan and Josh were there and my neighbor who is working on a couple of 8" mirrors also came by. Charlie brought parts of his 17" telescope that he is adapting for use for his 13" f9 project. The purpose of this is to get the scope operational to the point that he can star test to determine if the mirror is astigmatic. Jay worked on the azimuth motion of his Orion 10 " scope. After shimming the central bolt up with disks made of milk jug plastic, the motion seemed much better. This had the effect of reducing some weight on the teflon bearings. He did not have the OTA with him to try the motion out, but it should be improved. Joan brought the optics from a 17" telescope from which she would like to build an ultra-compact style dobsonian. This must fit in her car trunk when finished, hence the need to go with the ultra-compact design. This should be a nice telescope when finished and I look forward to seeing it and seeing through it when finished. Josh brought his 8" mirror and supplies to strip the mirror of its coatings. This is something I had not done before so it was good to learn together. As it turns out, ferric chloride does a great job. Josh soaked the front surface with the chemicals and gently swabbed with cotton balls. It did take awhile, probably an hour, to get the bulk of the aluminum off the mirror. At that point, we poured a sub-diameter pitch lap he will will use to touch up the figure of the mirror. My own current project is a 4" f4 mirror. Prior to the ATM session, I quickly threw together a mini dob mount for the purpose of star testing. So far the mirror is making a good impression on me, but I have yet to have a good night to really see what its limitations are. At that point I will either decide to work on its figure some more, or call it done and get it coated. I plan on mounting the OTA in a ball rather than a dob mount. The next session is on Nov. 12th from 9:00 AM to noonish. As usual, email me off list at mat.hutchings@siemens.com and I will give you directions to my house. Mat ---------------------------------------------------------------------------- This message and any included attachments are from Siemens Medical Solutions and are intended only for the addressee(s). The information contained herein may include trade secrets or privileged or otherwise confidential information. Unauthorized review, forwarding, printing, copying, distributing, or using such information is strictly prohibited and may be unlawful. If you received this message in error, or have reason to believe you are not authorized to receive it, please promptly delete this message and notify the sender by e-mail with a copy to Central.SecurityOffice@siemens.com Thank you
No Ronchi grid, Mat? Or artificial star? You can determine a lot from a mirror in daytime with either. The star test is the acid test, but a Ronchi will get you 98% of the way there, with some experience. Too, an artificial star will let you test in broad daylight.
Hang a Christmas ornament (silver) on a telephone pole about a block away. Instant artificial star.
Hi Chuck; I have had too many problems with getting an artificial star to work well. In the first place, there are not any telephone poles any longer (at least in newer neighborhoods), and even if you do have one, climbing a telephone pole can get you in trouble. I guess you could use an extendible pruning hook or something to jockey an ornament up there. Once you get the artificial star up, then even a slight breeze can make the ornament move, then you have poor contrast due to being in the daytime even with a black card as a background. After trying to make this type of artificial star work, I wondered, why? Just make the telescope and do a real star test at night. Also, that way when you are done with the mirror, you are automatically already done with the telescope. On the other hand, the advantages of an artificial star are that you don't have to wait for nighttime, seeing is not an issue, and the artificial star does not move across the sky. Over time, I have found the star test with a real star to be first rate. Yes, you do have to wait until dark, etc, etc, but waiting is what we amateur astronomers do best, right? Having said all that, I actually have been thinking about asking a neighbor if I can put an ornament up on his ham radio tower. I might go down that path again. See above for problems to overcome, but overcoming problems is another characteristic of what we do. Mat -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Monday, October 17, 2011 9:30 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] ATM session report and next planned date Hang a Christmas ornament (silver) on a telephone pole about a block away. Instant artificial star. _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php ---------------------------------------------------------------------------- This message and any included attachments are from Siemens Medical Solutions and are intended only for the addressee(s). The information contained herein may include trade secrets or privileged or otherwise confidential information. Unauthorized review, forwarding, printing, copying, distributing, or using such information is strictly prohibited and may be unlawful. If you received this message in error, or have reason to believe you are not authorized to receive it, please promptly delete this message and notify the sender by e-mail with a copy to Central.SecurityOffice@siemens.com Thank you
On 10/18/11, Hutchings, Mat (H USA) <mat.hutchings@siemens.com> wrote:
Hi Chuck;
I have had too many problems with getting an artificial star to work well.
Yeah, the Christmas ornament has it's limitations, but don't throw the baby out with the bathwater. Epoxy a large-diameter ball bearing to any convenient structure or tree. It won't swing in the wind. It also helps to stick a square of black plastic such as ABS behind it, to increase contrast. It doesn't have to be really high up, but the higher it is, the less ground currents you have to deal with. You can also mount it on a stick or tripod and just take it to a nearby schoolyard or football field. Also, I've used the specular reflections off of glass or ceramic insulators, but that was a long time ago. I don't know if they still use shiny insulators on poles anymore. Richard Berry described how to make a battery-powered artificial star a couple of decades ago, that he just toted out to a nearby field. I prefer shop work in the daytime, and star-testing in winter outdoors at night has it's own set of problems.
Yep, those are all good points and as I mentioned in my previous post, I am considering walking down that path again. I have also used the insulator trick in the past. Aw, come on, you can brave the cold at night in the winter! -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Tuesday, October 18, 2011 11:16 AM To: Utah Astronomy Subject: Re: [Utah-astronomy] ATM session report and next planned date On 10/18/11, Hutchings, Mat (H USA) <mat.hutchings@siemens.com> wrote:
Hi Chuck;
I have had too many problems with getting an artificial star to work well.
Yeah, the Christmas ornament has it's limitations, but don't throw the baby out with the bathwater. Epoxy a large-diameter ball bearing to any convenient structure or tree. It won't swing in the wind. It also helps to stick a square of black plastic such as ABS behind it, to increase contrast. It doesn't have to be really high up, but the higher it is, the less ground currents you have to deal with. You can also mount it on a stick or tripod and just take it to a nearby schoolyard or football field. Also, I've used the specular reflections off of glass or ceramic insulators, but that was a long time ago. I don't know if they still use shiny insulators on poles anymore. Richard Berry described how to make a battery-powered artificial star a couple of decades ago, that he just toted out to a nearby field. I prefer shop work in the daytime, and star-testing in winter outdoors at night has it's own set of problems. _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php ---------------------------------------------------------------------------- This message and any included attachments are from Siemens Medical Solutions and are intended only for the addressee(s). The information contained herein may include trade secrets or privileged or otherwise confidential information. Unauthorized review, forwarding, printing, copying, distributing, or using such information is strictly prohibited and may be unlawful. If you received this message in error, or have reason to believe you are not authorized to receive it, please promptly delete this message and notify the sender by e-mail with a copy to Central.SecurityOffice@siemens.com Thank you
On 10/18/11, Hutchings, Mat (H USA) <mat.hutchings@siemens.com> wrote:
Aw, come on, you can brave the cold at night in the winter!
Yeah, to a point, but then again, I am designing a heated observatory, so that's gotta tell you something... ;) Re: Ronchi testing With much experience, you can tell a lot with the Ronchi test. I used to hang-out with a local optical manufacturer, and we'd look at mirrors through the Ronchi. I would point-out problems that he had to stare and stare at, and most of the time he'd say "yeah, maybe..." until we star-tested it. Then he'd admit that I detected it with the grid.
Here is link about using a LED to build an artificial star, it does not seem to require more than about 100 ft of distance.
http://observatory.mvastro.org/library/Star_Test/ArtStar.html On 10/18/11, Hutchings, Mat (H USA) <mat.hutchings@siemens.com> wrote:
Aw, come on, you can brave the cold at night in the winter!
Yeah, to a point, but then again, I am designing a heated observatory, so that's gotta tell you something... ;)
Re: Ronchi testing
With much experience, you can tell a lot with the Ronchi test. I used to hang-out with a local optical manufacturer, and we'd look at mirrors through the Ronchi. I would point-out problems that he had to stare and stare at, and most of the time he'd say "yeah, maybe..." until we star-tested it. Then he'd admit that I detected it with the grid.
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Wow, that's an impressive setup for an artificial star! -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of erikhansen@thebluezone.net Sent: Tuesday, October 18, 2011 3:37 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] ATM session report and next planned date
Here is link about using a LED to build an artificial star, it does not seem to require more than about 100 ft of distance.
http://observatory.mvastro.org/library/Star_Test/ArtStar.html On 10/18/11, Hutchings, Mat (H USA) <mat.hutchings@siemens.com> wrote:
Aw, come on, you can brave the cold at night in the winter!
Yeah, to a point, but then again, I am designing a heated observatory, so that's gotta tell you something... ;)
Re: Ronchi testing
With much experience, you can tell a lot with the Ronchi test. I used to hang-out with a local optical manufacturer, and we'd look at mirrors through the Ronchi. I would point-out problems that he had to stare and stare at, and most of the time he'd say "yeah, maybe..." until we star-tested it. Then he'd admit that I detected it with the grid.
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On 10/18/11, Hutchings, Mat (H USA) <mat.hutchings@siemens.com> wrote:
Hi Chuck;
I have had too many problems with getting an artificial star to work well.
Yeah, the Christmas ornament has it's limitations, but don't throw the baby out with the bathwater. Epoxy a large-diameter ball bearing to any convenient structure or tree. It won't swing in the wind. It also helps to stick a square of black plastic such as ABS behind it, to increase contrast. It doesn't have to be really high up, but the higher it is, the less ground currents you have to deal with. You can also mount it on a stick or tripod and just take it to a nearby schoolyard or football field. Also, I've used the specular reflections off of glass or ceramic insulators, but that was a long time ago. I don't know if they still use shiny insulators on poles anymore. Richard Berry described how to make a battery-powered artificial star a couple of decades ago, that he just toted out to a nearby field. I prefer shop work in the daytime, and star-testing in winter outdoors at night has it's own set of problems.
It's actually cool to see people still grinding mirrors, I haven't done it in decades and have enough polished and aluminized mirrors to keep me going until death, lol. I used to teach mirror making at a local private school for gifted and talented kids, a LONG time ago.
Sir Isaac told me he loved your classes. On Oct 18, 2011, at 9:20 AM, Chuck Hards wrote:
It's actually cool to see people still grinding mirrors, I haven't done it in decades and have enough polished and aluminized mirrors to keep me going until death, lol.
I used to teach mirror making at a local private school for gifted and talented kids, a LONG time ago.
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Sir Isaac said there is an interesting article in the current S & T mag about rough grinding using a vertical drill press. 73, lh On 10/18/2011 3:20 PM, Dave Gary wrote:
Sir Isaac told me he loved your classes. On Oct 18, 2011, at 9:20 AM, Chuck Hards wrote:
It's actually cool to see people still grinding mirrors, I haven't done it in decades and have enough polished and aluminized mirrors to keep me going until death, lol.
I used to teach mirror making at a local private school for gifted and talented kids, a LONG time ago.
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Is it an orbital drill press?
Sir Isaac said there is an interesting article in the current S & T mag
about rough grinding using a vertical drill press. 73, lh
On 10/18/2011 3:20 PM, Dave Gary wrote:
Sir Isaac told me he loved your classes. On Oct 18, 2011, at 9:20 AM, Chuck Hards wrote:
It's actually cool to see people still grinding mirrors, I haven't done it in decades and have enough polished and aluminized mirrors to keep me going until death, lol.
I used to teach mirror making at a local private school for gifted and talented kids, a LONG time ago.
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Eric, just cleaning out some old messages. Sorry to have missed yours. No, I believe it is an earthbound one. heh, heh....73, lh On 10/20/2011 5:00 PM, erikhansen@thebluezone.net wrote:
Is it an orbital drill press?
Sir Isaac said there is an interesting article in the current S& T mag
about rough grinding using a vertical drill press. 73, lh
Yep, got a Ronchi screen or two. If you are referring to testing for astigmatism, the Ronchi test is not good for that. Unless the mirror is really bad. There are testers for testing astigmatism, but the star test is even better. See another post from me about artificial stars. Mat -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Monday, October 17, 2011 8:05 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] ATM session report and next planned date No Ronchi grid, Mat? Or artificial star? You can determine a lot from a mirror in daytime with either. The star test is the acid test, but a Ronchi will get you 98% of the way there, with some experience. Too, an artificial star will let you test in broad daylight. _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php ---------------------------------------------------------------------------- This message and any included attachments are from Siemens Medical Solutions and are intended only for the addressee(s). The information contained herein may include trade secrets or privileged or otherwise confidential information. Unauthorized review, forwarding, printing, copying, distributing, or using such information is strictly prohibited and may be unlawful. If you received this message in error, or have reason to believe you are not authorized to receive it, please promptly delete this message and notify the sender by e-mail with a copy to Central.SecurityOffice@siemens.com Thank you
participants (5)
-
Chuck Hards -
Dave Gary -
erikhansen＠thebluezone.net -
Hutchings, Mat (H USA) -
Larry Holmes