Does anyone measure double stars anymore?
Posted 01 September 2013 - 06:33 PM
Ronald Tanguay's name comes up quite a bit and he seemed to be an advocate for this sort of thing. Indeed, it looks like he once even published a journal of sorts on it.
What is the state of amateurs doing separation measurements these days?
(And what became of Ronald Tanguay? His journal seems to have vanished and his house (address listed in some of his S&T articles) seems to be owned by someone else, so I fear the worst.)
Posted 01 September 2013 - 06:44 PM
There are quite a few individuals and groups nowadays measuring doubles.
The JDSO appears every three months, has been running since 2005, and the archive of past issues is on the website. You can read your way through the lot, and be inspired. And it's free, but worth much more than the price.
Posted 02 September 2013 - 05:11 PM
Posted 03 September 2013 - 08:11 AM
I even found a FAQ in the JDSO from the U.S. Naval Observatory on submitting observations. That is probably the strongest pro-am link I've ever come across!
Now I wonder if visual measurements are useful. I know they have to be calibrated else are worthless. Still researching on how to do that....
Posted 03 September 2013 - 01:24 PM
If you read the various articles in the JDSO you will find a variety of way to measure from ToUCams to filar micrometers. For example, I use a DMK21 video camera for image acquisition (reel off a video file, convert to separate frames). Then I use REDUC to determine angle and separation. There is a bit more to it than that, like establishing your plate scale (pixels/sec) and camera angle, but this is easily accomplished.
Visual measures requite a micrometer. An eyepiece micrometer may be used to produce publishable measures, but I find the video camera route much easier. Filar micrometers are very expensive but visual measures do have advantages -- I am limited to pairs with less than 2.5 or so magnitude difference using video.
Hope you give measuring a try,
Posted 03 September 2013 - 02:20 PM
Posted 03 September 2013 - 09:11 PM
Posted 04 September 2013 - 03:58 AM
Posted 04 September 2013 - 08:22 AM
Am I reading this right?
Posted 04 September 2013 - 12:21 PM
You can get the list from the USNO, look for the neglected doubles link:
As StarDusty relates, it does not take expensive equipment or large scopes. But, it does require that the difference in magnitude be relatively small and you have to match your scope's capabilities to the doubles. That said, there are plenty to measure with a small scope.
Posted 04 September 2013 - 07:25 PM
I am toying with the idea of imaging a few with my DLSR using techniques similar to what I already do for Deep Sky Object (DSO's) using a guide scope system for long exposures.
My 4" f/28 Schiefspiegler might be able to do it. Here is M13 taken through the Schief. I should be able to go for a fainter doubles if I can image this?
Lots to work out yet regarding the best way to determining image scale, PA, etc, but it might work out....
Maybe when the weather improves.
Posted 04 September 2013 - 09:32 PM
Look at Florent's discussion of how he measures doubles in the link "The webcam is a micrometer." His REDUC program is the way forward and you can use any camera you like, not just a video camera. And, of course, if your DSLR takes videos, then that is the way forward. Using REDUC does not require plate solving, just camera angle and plate scale, parameters that can be easily determined using calibration doubles. Your 4" Schiefspiegler will make an excellent platform if on a equatorial mount.
Posted 07 September 2013 - 08:53 PM
I was imaging DSO's because of the clear conditions and moonless night we enjoyed at UACNJ in Hope NJ last night.
We also were able to observe the LADEE mission rocket as it pasted by New Jersey headed north after its launch last night at 11:27pm.
Here is a description of what we saw:
It was a crystal clear night right down to the horizon.
There was a group of us on the rock, maybe 8 in all standing on the rock together. About half the group was there because it was so clear and dark, the other half came just to watch the launch.
We spotted the rocket within 30 seconds after the 11:27 launch time, first as a bright red ball, like a flare less than 5 degrees above the hill tops on the other side of the valley.
The red ball changed colors and became a distinct and crisp white-yellow streak of light, like a long narrow cone with the large end up.
As it rose out of the southeastern horizon the long cone of light became more horizontal. It was headed north up the valley. It became dimmer, changed back a pinpoint of white light and disappeared. By now it was 10 maybe 15 degrees up and directly across the valley from us.
I thought is was over, but then there was a buff of white smoke followed by the lighting of the next stage. This left behind a gray cloud in the clear night sky. The rocket continued in the northerly direction and soon I could not see it any more.
Nice treat on a super clear and dark night. .
Posted 08 September 2013 - 09:11 AM
(1) If you are using a regular CCD with an decent FOV (say 15-30') and lots of other stars in the image, then you can use almost any available software that can "plate solve." No need to determine camera angle or image scale as they have been "solved." You simply use your software to measures the positions of the two stars.
(2) You are at a very narrow FOV because you are working at a very narrow FOV due to long effective focallength with either a video camera or CCD. There are few if any background stars that can be used to plate solve. In this case you calibrate camera angle and plate scale by first "shooting" one or more pairs of known angle and separation. You use the values obtained in REDUC to determine angle and separation of your unknown pairs. You also shoot another "calibration pair" at the end of the session to insure that the camera did not move during the session.
Caution: The use of calibration pairs assume a very accurate polar alignment. Best to pick calibration pairs fairly close to the pairs to be measured.
Posted 09 September 2013 - 09:10 AM
This software seems to provide image scale information, but I am just learning you how to use it and extract the plate scale and plate angle data it can provide. Pretty cool software. I never used anything like this before.
Are their other programs that will run under windows that might be better for this?
Posted 09 September 2013 - 09:48 AM
I used MPO Canopus because it has a very nice double star routine and automatic plate solving, but it does require attending to the learning curve inherent in all such programs.
The point of the plate-solving route is that you do not need to determine camera angle and plate scale -- this is solved by the fitting. All you have to do is determine the angle and separation between two stars on the plate and at least in MPOCanopus and AIP4WIN the calculation are done for you once you select the two stars in correct sequence.
I suggest you do some reading. The Bob Buchhiem chapter in the second edition of Observing and measuring Visual Double Stars (not the first edition) is a "must read" IMO as it summarizes the basic principles. Bob is one of the best science writers around. Many of the other chapters are very valuable.
Good measures, Ed
Posted 16 September 2013 - 09:54 PM
Posted 17 September 2013 - 08:03 AM
And I freely admit to having to google "Schiefspiegler." Fascinating scope design!