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Pages: 1 buddyjesus Carpal Tunnel Reged: 07/07/10 Loc: Davison, Michigan Double star eyepieces       #4660428 - 06/26/11 08:32 PM Edit   Reply   Quote Quick Reply   I was wanting to be able to make precision measurements to get more scientific with my double star observing. I was thinking of getting the celestron microguide 12.5mm eyepiece and using it with a barlow in my f10 refractor for 160x. I know this eyepiece has an illuminated grid pattern for timing(and therefore angular seperation) along with a 360 degree for angular positioning. Was wondering if anyone knows of a better reticle eyepiece? What are your favorites? Any suggestions? Post Extras:       azure1961p Postmaster Reged: 01/17/09 Loc: USA Re: Double star eyepieces [Re: buddyjesus]       #4660480 - 06/26/11 09:10 PM Edit   Reply   Quote Quick Reply   The approximation method via dawes [looking for the first signs of a notch] is one method, then theres the center of the spurious disc to the first minima for the rayleigh limit and when applicable the rings and minima beyond that as a seperation guide. Beyond that it gets iffy. Micrometer are used often but they get pricey, the mount needs to be solid - it really gets expensive quick when you look for that kind of precision. The approximation method tho [i think] does surprisingly well. Pete Post Extras:       buddyjesus Carpal Tunnel Reged: 07/07/10 Loc: Davison, Michigan Re: Double star eyepieces [Re: azure1961p]       #4660601 - 06/26/11 10:39 PM Edit   Reply   Quote Quick Reply   The measurements I was wanting to make were positional angle and seperation. I have seen some articles on JDSO.org that used the celestron eyepiece so thought that might be a good place to start. I agree that approximation would likely work best for tight doubles. Making several measurements based on that and recording the atmospheric quality would help determine what my final measurement would be. Also thought of using a little math to find the drift time on the x(RA) axis(sin cos theta)? I think I would need a very good stopwatch for that. Was also wanting to measure the distance from a star to the first diffraction ring by drift method to have another measure for reference. Post Extras:       Ed Wiley professor emeritus Reged: 05/18/05 Re: Double star eyepieces [Re: buddyjesus]       #4662371 - 06/28/11 12:17 AM Edit   Reply   Quote Quick Reply   I have a suggestion. Why not try imaging your doubles. I have used CCD cameras, ToU webcams and a DMK21. The trick is to use REDUC to measure the doubles and try for an optical train at around F20. Check out Florent's web site: http://www.astrosurf.com/hfosaf/index.htm There is lots of great information specific to imaging and measuring doubles. The software is free on demand. A ToUcam or Celestron Neximage can be picked up on on the used market for a start. Don't know the aperture of your scope but a webcam + 2X barlow and Florent's software and you are in business. Just make sure and begin with doubles of about equal magnitude and bright enough to be seen on your computer screen. Don't expect to be able to image really faint doubles or those very different in magnitude unless you can do long exposures (a la a CCD or something like a DMK21 that integrates). And don't expect to measure doubles anywhere near the Dawes limit of your particular scope; that takes very special techniques, exceptional seeing and rather large scopes (read interferometry techniques). For example, with average seeing I am limited to doubles about 2" separation and I am using an 8" DK at F22.5 (Dawes something like 0.75"). But even with these limitations there are lots of doubles in sore need of measures. I am happy to help, I am a JDSO contributor and love to encourage double star observers to contribute quality measures. Ed Post Extras:       desertstars Reged: 11/05/03 Loc: Tucson, AZ Re: Double star eyepieces [Re: buddyjesus]       #4662955 - 06/28/11 12:09 PM Edit   Reply   Quote Quick Reply   A few resources you might find useful: http://www.jdso.org/volume7/number2/Brewer_45_46.pdf http://www.jdso.org/volume6/number1/Frey.pdf http://www.jdso.org/volume6/number3/Schrader.pdf The chapter by Tom Teague ("Simple Techniques of Measurement") in Observing and Measuring Visual Double Stars, - edited by Robert Argyle - is also worth checking out. In fact, if you're delving into double stars, Argyle's book would be a good investment in any case. Post Extras:       buddyjesus Carpal Tunnel Reged: 07/07/10 Loc: Davison, Michigan Re: Double star eyepieces [Re: desertstars]       #4663429 - 06/28/11 04:03 PM Edit   Reply   Quote Quick Reply   I am a sketcher mostly but will be starting to dabble in webcamming sometime this year. I have a 4" achromat since you asked. My goals are to have measurements within two degrees for angular position and as close as possible with seperation(I don't know what level of error to expect.) More for personal study than anything else. I have seen this eyepiece used in JDSO articles and it seems like good gear. I was going to use it with a 2.4x dakin barlow on good seeing days for 192x since this is about all I can expect out of my scope. 2x barlow on average days for 160x. I will ready your articles today Tom and just got that book yesterday. I will also bookmark this page when I am ready to start webcamming. Post Extras:       EdZ Professor EdZ Reged: 02/15/02 Loc: Cumberland, R I , USA42N71.4W Re: Double star eyepieces [Re: buddyjesus]       #4663750 - 06/28/11 07:24 PM Edit   Reply   Quote Quick Reply   actually for double star observations, you can push your scopes easily up to 70x-80x per inch. I've had my 6" f/8 achromat up to 90x/inch For extremely close doubles you're going to need extreme high powers. 50x to 60x per inch is not enough to see minute details of what is going on in the diffraction pattern. edz Post Extras:       Warren Bitters member Reged: 05/04/06 Loc: Santa Barbara, CA Re: Double star eyepieces [Re: EdZ]       #4663976 - 06/28/11 09:52 PM Edit   Reply   Quote Quick Reply   All three of the articles referenced by desertstar in his June 28 post involve key members of the Central Coast Astronomical Society who fortunately benefit from the involvement of the professor of astronomy at the local college. I attended a club meeting recently and the speaker was Russ Genet. He described their work, which greatly involves high school and college students from CA and OR. They were able to teach kids with no experience how to make accurate measurements. It was quite interesting. Basically they are using the technique described by Tom Teague in the Sky & Telescope article about ten years ago (please help me with the exact reference) using the Celestron Micro Guide eyepiece. One thing I noticed in their presentation was the double stars measured were relatively wide, typically 15 to 60 arcseconds or more. However, I personally believe the technique could be used with more tight pairs. If you choose to pursue this project, enjoy and please let us know how it goes. Post Extras:       buddyjesus Carpal Tunnel Reged: 07/07/10 Loc: Davison, Michigan Re: Double star eyepieces [Re: Warren Bitters]       #4664118 - 06/28/11 11:39 PM Edit   Reply   Quote Quick Reply   Cool. I was worried about image stability with such high magnifications but will give it a try with both barlows together then. For me, your mentioning it is my first recent source saying that. I read about using 100x/inch in The Double Stars by Robert Grant Aitken(on google books website) and that was published back in 1918. Post Extras:       PJ Anway Carpal Tunnel Reged: 06/04/03 Loc: North Coast Re: Double star eyepieces [Re: buddyjesus]       #4673680 - 07/04/11 03:02 PM Edit   Reply   Quote Quick Reply   Quote: I was wanting to be able to make precision measurements to get more scientific with my double star observing. I was thinking of getting the celestron microguide 12.5mm eyepiece and using it with a barlow in my f10 refractor for 160x. I know this eyepiece has an illuminated grid pattern for timing(and therefore angular seperation) along with a 360 degree for angular positioning. Was wondering if anyone knows of a better reticle eyepiece? What are your favorites? Any suggestions? There are a couple of nice S&T articles on using this eyepiece to measure double stars. 1) by Ronald Tanguay in the Feb. 1999 issue p. 116 and 2) by Thomas Teegue in the July 2000 issue p. 112. Post Extras:       desertstars Reged: 11/05/03 Loc: Tucson, AZ Re: Double star eyepieces [Re: PJ Anway]       #4678812 - 07/07/11 12:03 PM Edit   Reply   Quote Quick Reply   Quote: Quote: I was wanting to be able to make precision measurements to get more scientific with my double star observing. I was thinking of getting the celestron microguide 12.5mm eyepiece and using it with a barlow in my f10 refractor for 160x. I know this eyepiece has an illuminated grid pattern for timing(and therefore angular seperation) along with a 360 degree for angular positioning. Was wondering if anyone knows of a better reticle eyepiece? What are your favorites? Any suggestions? There are a couple of nice S&T articles on using this eyepiece to measure double stars. 1) by Ronald Tanguay in the Feb. 1999 issue p. 116 and 2) by Thomas Teegue in the July 2000 issue p. 112. You know, it's posts like this that make me glad I bought S&T's seven decades collection. Post Extras:       rookie Good Night Nurse Reged: 01/14/06 Loc: St. Petersburg, FL Re: Double star eyepieces [Re: desertstars]       #4679944 - 07/07/11 09:31 PM Edit   Reply   Quote Quick Reply   Sky and Telescope has Robert Tanguay's article available online here. Post Extras:       Pages: 1

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