Robin Leadbeater

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Viewing 20 posts - 821 through 840 (of 1,193 total)
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  • in reply to: Spectro stuff for sale, best place to advertise? #580029
    Robin Leadbeater
    Participant

    Meteor spectroscopy is possible with the Star Analyser and a wide field camera

    http://www.threehillsobservatory.co.uk/astro/spectra_20.htm

    but a grating with higher dispersion would be better  eg 300 or even 600 l/mm depending on the lens focal length and sensor size. Bill Ward would be able to advise on the optimum setup

    https://britastro.org/user/213

    Cheers

    Robin

    in reply to: Request for monitoring of X Per #580019
    Robin Leadbeater
    Participant

    Here is how the H alpha line looks currently.  (LHIRES 2400 grating,  R~15000).  Also uploaded to the BAA spectroscopic database

    Robin

     

    in reply to: Spectro stuff for sale, best place to advertise? #580018
    Robin Leadbeater
    Participant

    Hi Paul,

    I think he sort of did 😉  You could PM for details

    in reply to: New RCB star in Cam – call for photometry/spectroscopy #580016
    Robin Leadbeater
    Participant

    Latest feedback from Gabriel Murawski based on the spectrum is that this may in fact be a YSO. It is currently being looked at by experts in this area.

    Robin

    in reply to: X Per – Photometry and spectroscopy requested #580012
    Robin Leadbeater
    Participant

    I have posted some information specifically about spectroscopy in the spectroscopy section

    https://britastro.org/node/15540

    Robin

    in reply to: Spectro stuff for sale, best place to advertise? #580011
    Robin Leadbeater
    Participant

    Hi Tony,

    the ARAS forum has a new for sale section now, “Petites Annonces”  though there are not really many constructors there.

    The astronomical_spectroscopy yahoo group probably has more self builders and I see there was a recent ad there for an L200 for example, you could check with Ken who owns the group if it would be acceptable

    Also Stargazers Lounge perhaps where there is some interest in spectroscopy ?

    Robin

    in reply to: X Per – Photometry and spectroscopy requested #580001
    Robin Leadbeater
    Participant

    According to BeSS, it is not catalogued as a Be star unfortunately otherwise there would undoubtedly have been a good history of H alpha spectra of this bright object. Does anyone know why it is not in the Be Star catalogue ?

    Robin

    in reply to: New Atik 460, does it have too many hot pixels? #579999
    Robin Leadbeater
    Participant

    Looking in detail at the distribution of these warm pixels in my camera it seems most of them fall between 500-800 ADU, causing the “knee” in the cumulative distribution described in the ARAS thread. They are in fixed positions and only represent ~1 in every 2000 pixels though and are low enough to be corrected by a dark provided they are otherwise well behaved.

    Robin

    in reply to: New Atik 460, does it have too many hot pixels? #579998
    Robin Leadbeater
    Participant

    Hi John,

    Here is a link to a dark taken under the same conditions as yours using my ATIK 428.  This camera is identical except for using a smaller version of the same CCD so should be a direct comparison.

    https://drive.google.com/file/d/1QkocrvkQRBCOlTK9NbxOhSVxWMwM7COg/view?usp=sharing

    If you have ISIS, it includes a nice feature which you can use to calculate the gain, and noise figures described here

    http://www.astrosurf.com/buil/isis/noise/result.htm

    These warm pixels are not specifically measured using this technique though. To get the dark current figures quoted by ATIK and measured by Christian Buil, you have to chose a measured area free of warm pixels.

    Robin

    in reply to: New Atik 460, does it have too many hot pixels? #579995
    Robin Leadbeater
    Participant

    Hi John,

    I remember there was some discussion on the ARAS forum about the long tail of warm pixels seen in cameras with Sony CCD which seems to have got progressively worse with each generation.  

    http://www.spectro-aras.com/forum/viewtopic.php?f=8&t=1919&p=9871

    I recently saw an article somewhere which suggested this was a characteristic of CCD with anti-blooming, a connection had not been aware of before.

    Discounting these, the noise figure of these CCD is very good though and they seem to respond well to dark subtraction.

    Running at a lower temperature might help. I run my similar ATK428 at -10C all the year round. 

    Robin

    in reply to: Transient location #579981
    Robin Leadbeater
    Participant

    A potential target for a spectrum. mag 15 is just about bright enough for a standard ALPY 600 and a modest (say> 10 inch) aperture.

    Robin

    in reply to: Characterizing a newly discovered variable #579975
    Robin Leadbeater
    Participant

    Hi Woody,

    I have it on my list but have not had a chance to look at it yet. It looks a very crowded field. I make it this one in centre of the DSS image. Is that correct ?   From VSX  J2000 18 20 12.99 +07 15 52.1 

    Cheers

    Robin

    in reply to: New RCB star in Cam – call for photometry/spectroscopy #579972
    Robin Leadbeater
    Participant

    Here is the reduced spectrum.  Very noisy but the H alpha emission is clear.  The continuum is very red but there is high extinction in this direction. Total galactic E(B-V) is ~1.0 according to IRSA. The Na D line is clear but again that could be Interstellar.  

    Robin

    in reply to: New RCB star in Cam – call for photometry/spectroscopy #579969
    Robin Leadbeater
    Participant

    On it now with the ALPY600. It is very weak but there is clear H alpha in emission.  Raw spectrum image (30min) attached

    Robin

    in reply to: A most unusual meteor spectrum #579948
    Robin Leadbeater
    Participant

    I wondered this too.  A piece of Mg alloy not large enough to have been tracked but enough to produce a trail ?

    Robin

    in reply to: Hyperstar for photometry? #579937
    Robin Leadbeater
    Participant

    Michael Richmond’s on line calculator can be used to estimate the performance of a given setup for example

    http://spiff.rit.edu/richmond/signal.shtml

    Robin

    in reply to: Hyperstar for photometry? #579936
    Robin Leadbeater
    Participant

    added replies to #9 and #11 above

    (Note to webmaster – we need a quote button so we can keep to a linear thread and not lose replies back up the thread)

    Robin

    in reply to: Hyperstar for photometry? #579935
    Robin Leadbeater
    Participant

    Then  you are currently slightly undersampled already and would not want to go any shorter in focal length. Undersampling in photometry is much less desirable than oversampling.

    Robin

    in reply to: Hyperstar for photometry? #579934
    Robin Leadbeater
    Participant

    Yep sorry, factor of 4 out but the ratio (and hence the increased counts) is the same.  Changing the magnification (ie focal length) changes the counts per pixel (both star and sky background counts) but makes no different to the counts in the aperture, either the star counts or the sky background counts. The only difference is if you spread the light over more pixelsthan you need to, you increase the camera noise contribution. In practise this is only the thermal noise, not the read noise as you can compensate for this (in CCD cameras) by binning pixels.  Thermal noise is very low in modern CCD, particularly at typical exposure times used for photometry so the net effect is that changing focal length does not improve photometry SNR, only increasing the aperture does this   

    Robin

    in reply to: Hyperstar for photometry? #579926
    Robin Leadbeater
    Participant

    What is your typical star size with the 70mm f6 currently?  3 arcsec is only 6.1um with your existing setup so you are potentially undersampled already so there would be no advantage going to a lower focal length to beat the seeing.  (I think potential gain is only marginal anyway as all you do by moving to a shorter focal length  is reduce the camera noise contribution, the star and sky background counts stay the same).

    The extra aperture will gain you some photons though  (Area of C6 is 608 cm2 allowing for the central obstruction compared with 154 cm2  so ~4x or ~1.5 magnitudes)

    Robin

Viewing 20 posts - 821 through 840 (of 1,193 total)