Re: Lacrosse 5 Reappearance

From: Philip Masding (
Date: Fri Jan 26 2007 - 15:44:39 EST

  • Next message: Kevin Fetter: "Re: Flashing Unknown in Perseus"

    Just a short note to say how the light curves were obtained.
    As you probably know Mike Tyrrell and I have written automated tracking 
    software which allows us to track satellites with an LX200.
    We also both have low light cameras mounted on the telescopes. Mine is a 
    f2.8 135mm telephoto lens and a 1/3" BW Sony EXviewHAD chip rated  0.003 
    Lux. It can reach about mag 7.
    During a track the computer continually takes light readings from this 
    camera and creates the light curve.
    Afterwards the camera can be pointed at a series of stars of known magnitude 
    and calibrated in a few minutes.
    This calibration is then used to create the light curve. We calibrate our 
    cameras after every observations so the calibration is correct for the 
    transparency on the night and any temperature dependency say of the 
    It would be great if someone else out there had similar technology because 
    the light curves of Lacrosse are complicated and we need more information!
    ----- Original Message ----- 
    From: "Gerhard HOLTKAMP" <>
    To: <>
    Sent: Thursday, January 25, 2007 10:10 PM
    Subject: Lacrosse 5 Reappearance
    > Congratulations to Marco Langbroek and Philip Masding for their 
    > simultaneous
    > observations of the Lacrosse 5 "disappearance trick" on 22-JAN and 
    > 24-JAN-07.
    > Seeing Lacrosse 5 fade from two separate locations with quite different
    > viewing geometries at exactly the same time clearly indicates that it is 
    > not
    > the observer's position but just the satellite itself that is to blame. 
    > This
    > rules out a lot of fancy explanations I was dreaming of!
    > Taking a closer look at the light curve which Phil posted on
    > I now realize that I kind of witnessed the reappearence of Lacrosse 5 at
    > yesterday's (24-JAN-07) pass without noticing it at the time. I wanted to
    > observe Lacrosse 5 pass Auriga. With some cirrus clouds present I could 
    > just
    > make out some brighter stars and decided I rather take binoculars and try 
    > to
    > pick up Lacrosse 5 next to Iota Aur. When trying to locate that star at 
    > about
    > 18:21:00 I didn't notice anything special. According to Phil's light curve
    > Lacrosse 5 must have come out of hiding a few seconds after that and 
    > indeed a
    > few seconds before it passed Iota Aur at 18:21:14 it almost blinded me in 
    > my
    > binos. It was an easy and steady mag 1.5 or brighter and passed Beta Tau 
    > at
    > 18:21:30. Had I just looked up to the sky without the binoculars I should
    > have seen it  reappear right away! (At the moment I thought that I had not
    > seen it before because a roof was blocking part of the sky for me but I 
    > now
    > realize that it was not the roof but the disappearance trick to blame.)
    > Gerhard HOLTKAMP
    > Darmstadt, Germany
    > 49.8822 N, 8.6558 E
    > -------------------------------------------------------------------------
    > Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive:
    Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive:

    This archive was generated by hypermail 2b29 : Fri Jan 26 2007 - 15:51:31 EST