Robin Leadbeater

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  • in reply to: ZZ Psc not where it should be! #630816
    Robin Leadbeater
    Participant

    Proper motion confuses the heck out of some of the bots auto reporting transients. They compare the sky with their library image, looking at the differences and once the proper motion moves the star out of the psf of the library image it suddenly triggers a bright transient ! There are quite a few examples in the Transient Name Server

    in reply to: ZZ Psc not where it should be! #630812
    Robin Leadbeater
    Participant

    If you look at the image cutout at SIMBAD
    https://simbad.cds.unistra.fr/simbad/sim-basic?Ident=ZZ+PSc&submit=SIMBAD+search
    and blink between the DDS and SDSS images you can actually see the position move between the two survey dates. The J2000 position is between the two (Sometimes for high proper motions you even see a double image Red/Blue in the colour DSS images because of the difference in dates)

    in reply to: Betelgeuse #630788
    Robin Leadbeater
    Participant

    An ApJL preprint on ArXiv today presents events for the probable direct imaging of a lower mass companion of Betelgeuse:

    There’s an excellent episode from the BBC World Service “Science in Action” programme on this
    https://www.bbc.co.uk/programmes/w3ct6yfm

    “Have we found Betelgeuse’s ‘Betelbuddy?’ An astronomical mystery seems to be solved as the long-predicted stellar companion to the bright star Betelgeuse has been detected by a team of researchers led by Steve Howell of the NASA Ames Research Center using the Gemini North telescope in Hawaii. Steve discusses this breakthrough alongside astronomer Andrea Dupree of the Harvard Smithsonian Center for Astrophysics, who has discussed the predictions of this star on previous Science in Action programmes.”

    Robin Leadbeater
    Participant

    Here is some further information from Alexander on the spectroscopy side which I have been asked to also distribute to the wider spectroscopy community. It is similar monitoring to that requested by Paul Roche which covered mainly 2018-2021 and was reported on the ARAS and BAA forums
    https://www.spectro-aras.com/forum/viewtopic.php?t=2128
    https://britastro.org/forums/topic/request-for-monitoring-of-x-per

    ————————————————————————————-
    Call for Spectroscopic and Photometric Monitoring of X Persei (4U 0352+309)

    Observers are invited to join a monitoring campaign on the Be/X‑ray binary X Persei, which is currently in an unusually low X‑ray state.

    The campaign is coordinated by Alexander Salganik, PhD researcher at the University of Turku, Finland, whose work focuses on the Swift/BAT X‑ray light curve of the system. Since 2001 X Persei has shown three major X‑ray outbursts roughly every seven years. The next expected outburst has not occurred, and the source now sits at its lowest X‑ray flux in more than twenty years. Optical monitoring will help determine the current state and physical properties of the Be star’s disk, including whether it remains present or has dissipated during this faint phase.

    Spectroscopy: priority is high‑resolution Hα (6563 Å). Additional coverage of He I 6678 Å, He I 5876 Å, or Hβ 4861 Å is welcome. Target cadence is one observation per week.

    Photometry: UBVRI is very welcome. If limited, R and V bands are most useful, with R particularly sensitive to disk emission.

    Data can be sent directly to Alexander Salganik (alsalganik “at”gmail.com), who will provide regular feedback and campaign updates.

    Robin Leadbeater
    Participant

    The paper is now in A&A and a press release from University of Warwick

    (At one point there was a possibility of me appearing on BBC Midlands Today but it was pushed off the list by other events !)

    Cheers
    Robin

    in reply to: Quantum Efficiency #629968
    Robin Leadbeater
    Participant

    I am not sure if the transmission grating (grism) used in the direct vision spectrograph you are using is sensitive to polarisation though.

    Transmission gratings are not sensitive to polarisation so that is one thing less to worry about 😉

    https://www.edmundoptics.co.uk/f/transmission-gratings/13496

    Cheers
    Robin

    in reply to: Quantum Efficiency #629966
    Robin Leadbeater
    Participant

    One thing you could do without having to calibrate is to compare the spectrum of the antitwilight sky with that in different directions. Just divide the two spectra to see the difference (Adjust the exposure so the intensity is similar to reduce problems with non-linearity of the camera and be sure to switch off any automatic colour correction in the camera).

    Note though that some reflective gratings respond differently depending on the polarisation which changes depending on the direction in the sky. This is an example of the response of a reflection grating. S and P are for the two directions of polarisation. You can also see why you need to consider the grating response as well as the camera QE if you want an absolute flux calibration
    https://www.optometrics.com/assets/M466Sales.png

    I am not sure if the transmission grating (grism) used in the direct vision spectrograph you are using is sensitive to polarisation though. This shows typical curves for some transmission gratings but it does not show any effect of polarisation.
    https://www.optometrics.com/assets/ARTx.png
    The one in your spectrograph will probably be similar to the 600l/mm curve

    Cheers
    Robin

    • This reply was modified 2 months, 2 weeks ago by Robin Leadbeater. Reason: typo
    in reply to: Quantum Efficiency #629954
    Robin Leadbeater
    Participant

    You can approximately calibrate the spectrograph in relative flux using a tungsten lamp of known temperature which will have a black body curve but this will not include the effect of the atmosphere. If you then measure the sun at two different elevations you can then also estimate the effect of the atmosphere. You will need to calibrate the spectrum in wavelength first though

    Cheers
    Robin

    in reply to: Quantum Efficiency #629953
    Robin Leadbeater
    Participant

    Note that even if you know the QE of the camera, this is not enough to flux calibrate the spectrum as there are many other effects between the sun and the camera sensor. The atmosphere and the grating efficiency are the main ones. You need a known light source to flux calibrate spectra. For astronomical spectroscopy this is done by measuring a star with a known spectrum as described in my document here
    http://www.threehillsobservatory.co.uk/astro/Relative_flux_calibration_20221222.pdf
    but that would not be straightforward with your setup.

    Can you describe in more detail what you are trying to measure about the solar spectrum ?

    Cheers
    Robin

    in reply to: Which diagonal? #629711
    Robin Leadbeater
    Participant

    The only caveat with these high reflectivity dielectric mirror coatings is that the reflectivity can plummet outside the visible range, particularly into the UV below 4000A. Something to keep in mind if doing spectroscopy at that end of the spectrum.

    in reply to: April Lyrids #629679
    Robin Leadbeater
    Participant

    Only 10 Lyrids on my NW facing camera last night 21/22nd, though cloud was patchy and completely clouded over by 02:00 UT so probably missed the peak

    in reply to: April Lyrids #629678
    Robin Leadbeater
    Participant

    I just thought it was suspicious to get 3 meteors so close together and parallel within a 30 second period.

    Specular reflectance flares from satellite constellations perhaps ?

    Cheers
    Robin

    in reply to: Anomalous bright spot on the night side of Venus #629649
    Robin Leadbeater
    Participant

    If it is gas from an eruption it will be interesting to see if it turns into a dark (absorption) feature in UV images once it reaches the sunlit area

    Robin

    in reply to: US administration looking to slash NASA science budget #629519
    Robin Leadbeater
    Participant

    European institutions including British will need to step up to fill some of these gaps.

    There are other important resources like this in Europe like CDS (SIMBAD etc) for example, and others which form a global “astro-ecosystem”. This is less to do with money and more to do with politics and cultural shifts in the US though of course.

    in reply to: Disadvantages of cooled camera #629464
    Robin Leadbeater
    Participant

    The controlled constant temperature that cooling provides also means that calibration frames can be re-used

    Robin

    in reply to: Preparing for the next eruption of T CrB #629229
    Robin Leadbeater
    Participant

    Interesting graphics from NASA in this article. The accretion disc appears to be around the wrong star, with the erupting T CrB occuring in the outer regions of the disc. Wow!

    I did a reverse image search and tracked it back to where it was repurposed from in 2010
    https://svs.gsfc.nasa.gov/20184
    not that it makes it any better but at least we now know who was to blame !

    They actually do also have a decent animation linked from that page showing the accreting system but not the outburst
    https://svs.gsfc.nasa.gov/20393/

    EDIT the explosion is shown in a further animations down the page

    in reply to: Preparing for the next eruption of T CrB #629218
    Robin Leadbeater
    Participant

    I see at least Space.com put a question mark at the end of their headline and quoted Jeremy’s scepticism (Also the lack of any evidence in the RV data to support the presence of a suggested third body to trigger the outburst on certain dates.)
    https://www.space.com/the-universe/stars/hold-onto-your-hats-is-the-blaze-star-t-corona-borealis-about-to-go-boom

    in reply to: DwarfLab smart telescopes #628879
    Robin Leadbeater
    Participant

    The downside for spectroscopy though would be the built in 430-690nm “astro” filter. Does it also have an unfiltered setting do you know ? (If not, for dedicated astro use an obvious hack would be to remove the terrestrial “VIS” filter like with DSLR)
    The dual band OIII/Hbeta +H alpha filter setting could be interesting for wavelength calibration though

    Cheers
    Robin

    in reply to: DwarfLab smart telescopes #628878
    Robin Leadbeater
    Participant

    Hi Andy,

    It is perhaps also interesting for spectroscopy. I see from the specs that the sensor is larger than the one in the SeeStar 30 which means that unlike the Seestars it could potentially be used directly with a Star Analyser recording the full spectrum in one shot (not including the zero order, though that plus the blue end of the spectrum could be captures separately.) The equatorial mode would also avoid the problem of the spectrum fanning out due to field rotation which is seen with the SeeStar. The tiny 2 micron pixels means the image is probably well over sampled which should be good for avoiding artifacts with the colour sensor.

    Cheers
    Robin

    in reply to: Which Powertank ? #628661
    Robin Leadbeater
    Participant

    The specs on line say it has an (impressively large) 9.6v 45Ah internal battery, good for 10 hours operation

    I suspect 45Ah may be a typo and the battery is actually 4.5Ah even though the 45Ah figure appears everywhere on different sites.
    Compare for example with the effectively identical Celestron branded version, here where a space has been used instead of the decimal point (9 5v 4 5Ah)
    https://altairastro.com/celestron-nexstar-evolution-925×22-sct-6537-p.asp
    That would be ok for the claimed 10 hrs just tracking (at ~0.5A) but a lot of slewing would take more power. What life do you typically get with the internal battery ? (If the internal battery is 4.5Ah then say 3 x that time with the 17Ahr power tank would seem reasonable given that you don’t want to run down lead acid batteries too low to prolong their life)

    Cheers
    Robin

Viewing 20 posts - 1 through 20 (of 1,203 total)