Re: ATM Lowest power for splitting Epsilon Lyrae

["Barlow Pepin" <atmjedit@conceptsnet.com>]

Having done some video work on double stars with a friend I can say that it
was a lot of fun. We were eventually able to fleetingly image Sirius B, for
instance, using an 11-inch SCT. But long-term data collection and reduction
with a rig like this?

The bottom line is really pretty simple: if the scope is not stable enough
for simple visual micrometer work on wide doubles, you may be in for much
frustration no matter what you stick at the image plane. Also, as for
measurements over time for computing orbits, current off-shelf VCR
technology is not up to the challenge. Resolution is limited to less than
1000 lines which cuts out most really close doubles unless you project the
heck out of them, at which point seeing disturbances become a nightmare.
Also, star images outside a narrow magnitude bin irradiate excessively or
disappear unless a lot of setup is done and individual (repeatable!)
settings are contrived for each pair. This involves much work with various
ND and color filters, focal reducers, projection with an assortment of EPs,
adjusting gain with inline amplifiers -- fascinating but long hours.  Also,
the more sensitive the camera (such as low light surveillance types) the
coarser the star images tend to be, and the greater the difficulty deriving
a true center from which to measure the position of the comes. Don't let
this
dissuade you from trying, but in my opinion such a project calls for a
purpose-built telescope and imaging system. Good luck!



-----Original Message-----
From: The Silent Observer <silent1@ix.netcom.com>
To: atm@shore.net <atm@shore.net>
Date: Wednesday, August 11, 1999 7:26 PM
Subject: Re: ATM Lowest power for splitting Epsilon Lyrae


>
>Richard Schwartz wrote:
>>
>> I want to do more than just split the close doubles: I want to measure
>> their separation and their angle.   That would allow me to relate their
>> masses to their distances if I take measurements over a long period of
>> time and see one entire orbit.
>>
>> I know there are techniques using a micrometer, but many of us don't
>> have a steady enough image to use a micrometer.
>>
>> I thought of using some kind of beam splitter to superimpose images of
>> the two stars, but generally they are of unequal brightness and one star
>> will cover up the other one so as to prevent accurate positioning.
>>
>> I thought of using the earth's rotation to sweep cross hairs past the
>> stars, but surely the earth rotates way too fast for those close
>> doubles.
>>
>> There must be a better, elegant way that we can do it.  After all, this
>> is 1999, not 1899!
>
>This is an application just crying out for videography.
>
>With a video camera, assuming you have a bright enough image and/or
>sensitive enough chip, you can take 30 frames per second; that's fast
>enough to pretty much freeze seeing wobbles (or at least let you pick
>out the good frames from among the bad ones), digitize the frames, and
>use graphics software of some sort to count the pixels between star
>images.  Average the counts from a lot of frames, and use the sweeping
>crosshair on less close doubles (say, Mizar or Castor) to calibrate your
>image size against the known angles of other doubles or multiples.
>
>Using video, you can take as many measurements in a single night as
>would have been done in a month using film photography, as recently as
>1970.
>
>--
> WARNING!!  This area has been designated an official DOPE FREE ZONE!!
>
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>
>Donald Qualls, aka The Silent Observer           NAR # 70141-SR Insured
>Rocket Pages             http://members.aol.com/silntobsvr/launches.htm
>
>Opinions expressed are my own -- take them for what they're worth
>and don't expect them to be perfect.