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Hi Andrew,
I think for me the main problem the flat solves is getting rid of the ripples in the ATK428 camera response when used with the ALPY, that are otherwise difficult to accurately remove using an instrument response generated using a reference star, because of their rather close spacing
Yep plenty of signal to knock down the stochastic errors and a large area to average out the seeing. The question is how stable is the camera electronics (gain and dark current) and the atmospheric transparency at the sort of timescale we a talking about?
Hi Grant,
Mostly beginners luck really. Back then I was just scratching around for interesting science based projects to do with my modified webcam and knew very little about measuring variable stars, otherwise I probably would not have even tried!
That sounds tough. A back of envelope calculation suggests ~1/32000 change (10 arcsec/30 arcmin)^2
Robin
It was (just) possible with a modified webcam 🙂
If it is just a simple demonstration of a dip you are after, perhaps you could use the guiding program PHD which can produce a graph of the “mass” of the selected star in the field in real time. (using a zwo camera with its all sky wide field lens?)Not sure if you can scale the graph to show a small dip though
Cheers
Robin
These types of star have have distinctly sawtooth pulsations with the rise time shorter than the fall. eg YZ Boo has a catalogued rise time of 31% which seems to tally with the actual light curve
EDIT:from the catalogue field descriptions
Rise_Eclipse_Time
This parameter contains either the rise time (M-m) for intrinsic variables, or the duration of the eclipse (D) for eclipsing binaries, both given as a percentage of the period value for the star. These values help to define the shape of the light curve.Cheers
Robin
>It would rely on a bit of luck with the timing – if the capture started at the maxima or minima there would be no difference in the pulsar’s brightness between the frames. Also I’m not sure you could trust the camera to run at a constant speed and not drop frames whilst capturing.
I think provided the exposure time is short enough (less than the max to min), the frame rate just needs to be known and stable (and just different from, even slower, than the pulsar). You can then assign a relative phase to each frame and stack the frames in groups with similar phase. A quick initial test would be to test if the pulsar can be seen in a simple stack of short enough exposures. If so then seeing the pulses should just be a matter of picking the right ones out and stacking them. In theory I suspect you could even find the pulsations without knowing the period.
I know it is possible directly with a 1m scope and an EMCCD based camera which has effectively zero read noise
https://www.cloudynights.com/topic/285383-crab-nebulass-pulsar-is-blinking-not-a-joke/?p=3632352
but it might be interesting to run the figures for a modern CMOS camera to see if given a reasonable size scope, summing enough images at each phase could pull the signal out
Robin
Well H alpha is there with the right sort of width for a nova (FWHM ~2500km/s) and probably H beta with similar width but the bright sky background has dragged the SNR down to single digits so nothing else is showing above the noise.
Well after 140 mins on it with the ALPY 600 last night there is something there.
(signs of a broad H alpha emission by the looks) Lets see if I can extract it
Also on TNS
https://wis-tns.weizmann.ac.il/object/2019qcg
There is a possibility of some clear sky here tonight but yes,likely to very tricky with interference from galaxy and moonlight
I am not a member of the “12a Collaboration” but there must be some of the VSS Section who are on here. If not, I am sure an email to Dr Matt Darnley at LJMU would bring you up to speed if you want to join the collaboration.
Cheers
Robin
If you are interested in following a white dwarf binary system that might “soon” become a type 1a supernova then M31N 2008-12a could be a good bet. Matt Darnley talked about it at NAM this year
https://nam2019.org/thursday/details/23/327
https://nam2019.org/thursday/details/23/445
Robin
Yes the progenitor of the LMC supernova SN 1987A, Sanduleak -69 202 had been catalogued spectroscopically as a blue supergiant prior to it going supernova. I am not aware of any observed outbursts before it exploded though.
If 2010oct and 2017ein (correction 201oct and 2019cda) don’t turn out to be the same object then other examples of impostors apparently later exploding for real as supernovae are 2006jc and 2009ip
Yes extra galactic supernova progenitors are just faint stars among billions so until we get another supernova in our own galaxy, there are very few observations of supernova progenitors, mostly found in deep images eg archive HST images. All are of core collapse types as they are produced by luminous stars eg supergiant and Wolf Rayet stars, for example
https://www.spacetelescope.org/images/opo1847b/
The progenitor of sn 2017ein discovered by Ron Arbour
Robin
There are cases of stars which have had previous outbursts and then gone supernova, as in this one found by Ron Arbour
https://britastro.org/node/17595
Cheers
Robin
Hi Kevin,
Concerning instrument response/atmospheric extinction, Christian Buil has been moving away from the reference star at the same air mass method recently.
http://www.astrosurf.com/buil/instrument_response_us/
Essentially he is separating out the true response of the instrument which he reuses, from the atmospheric extinction which he models. Although this is similar to the technique pros use, I am not totally convinced about this for my atmospheric conditions so am currently still using the old reference star as similar air mass method, though I do admit to reusing instrument responses quite freely for H alpha at high resolution with the LHIRES where the atmospheric extinction effect is small. David Boyd was at OHP this year so perhaps he has some updates on this new method?
I think your method of reusing the dispersion equation should work well with the ALPY provided the temperature does not change too much as it seems very stable to me. I would suggest still taking a lamp spectrum and using a lamp line as a single anchor point to avoid any problems with overall shifts. You could also use this lamp spectrum to make sure there has been no change in dispersion eg due to temperature by checking the position of second line in the spectrum
Cheers
Robin
Hi Paul,
They look like trails of hot pixels. Is this an aligned sum of several individual exposures?
(IC1296 brings back memories. It was a test of how deep I could go with my first astro camera, a surveillance camera which I modified for long exposures in 2002).
http://www.threehillsobservatory.co.uk/astro/1004xcam.htm
The resulting LRGB image of M57 even made it into Astronomy Now. Cutting edge then !
