Forum Replies Created
-
Posts
-
there is a discrepency at Hbeta (min intensity ~ 0.2 compared to my value of ~ 0.35) which I would like to resolve.
Ken,
My measurement originally posted by Andy confirms your value of ~0.35 minimum for H beta as measured at R~18000
https://britastro.org/specdb/data_graph.php?obs_id=9871Cheers
Robinas well as downscaling, converting to video also involves significant compression with resulting artifacts and loss of detail, akin to using jpeg images
The amount of compression (in addition to the downscaling (binning by interpolation) can be seen by comparing the video size with the expected size of uncompressed frames. For example one minute of uncompressed 8 bit 1270×720 video at 60fps should be 1270*720*60*60 = ~3.3GB !
Cheers
RobinI forgot to mention that as well as downscaling, converting to video also involves significant compression with resulting artifacts and loss of detail, akin to using jpeg images so the resulting video is not like uncompressed avi from webcams (or ser from astro cameras) so RAW stills would be better. The downside is planetary imagers take hundreds or even thousands of frames to select the ones with good seeing to stack which would be impractical with RAW frames from a DSLR
Cheers
RobinSadly eclipse day was cloudy, but Gigglewick got it!
As a girl of 7, my mother lived in rural Lancashire a few miles along the track from Giggleswick and recalled the 1927 eclipse. She remembered the chickens rushing back into the hen house thinking night had fallen !
Not wishing to get people’s hopes up, but this interesting ATel #17041 was released just a few moments ago.
The spectrum from the ARAS database showing the increase in H alpha emission taken on 7th of February that they refer to is mine, though I have no connection with the team. (If this was my ATel I would definitely be putting a question mark at the end of the title !)
There are actually high resolution H alpha spectra close to all three dates in ARAS database
https://aras-databas…abase/tcrb.htm
See attached. Mine showing the increase in emission is in black.I am sceptical about any predictions of TCrB base on accretion rate though which varies continuously in all timescales. For example attached is a spectrum in the ARAS database from from Francois Teyssier taken in 2021 when it was in a continuous high state which shows the same H alpha intensity as my Feb 7th spectrum. Of course then again it might blow tonight ! We do urgently need more spectra though and unfortunately I have been clouded out since.
Cheers
RobinWe do have a spectrum of Europa in the BAA database, but it is low resolution with an R value of 564.
That link actually points to a high resolution solar spectrum by me (taken through a solar filter, not of the sky) though unfortunately although it covers H beta it does not cover Na D
Cheers
RobinIn the case of 640×480 video where the aspect ratio is lower than that of the sensor I would expect the downsampling to be done based on the height of the sensor and then the left and right edges cropped to match the aspect ratio ie 5184×3456 is downsampled to 720×480 and then cropped by 40 pixels left and right
Hi James,
Not the same camera but with my compact camera the video is downsampled from the native sensor resolution to the video resolution based on the width of the video frame and then if the aspect ratio of the video is different from that of the sensor, the video image is cropped in height. eg 5184×3456 would be downsampled to 1920×1280 and then cropped 100 pixels top and bottom to give 1920×1080. The downsampling ratio is not in general a whole number of pixels (ie a simple binning) so presumably it is done using some kind of interpolation algorithm to maintain image quality.
Cheers
RobinAn AAS research note has been issued discussing the similar short term flare event seen in amateur spectroscopic observations during November 2024
https://iopscience.iop.org/article/10.3847/2515-5172/adb425
(It is possible that these are common during the low state but may not be picked up due to observing cadence)Cheers
RobinThe Variable Star Section is a good example of why it can be useful to make a Circular public. I know that professional astronomers read it. If it were behind a pay wall then that might not happen. Having the professional researchers read the Circular benefits the members who contribute to the Section.
I’ve experienced this just today. It was an unexpected treat to see in a paper just published on the RW Cep “Great Dimming”
“Atmospheric dynamics of the hypergiant RW Cep during the Great Dimming”
https://arxiv.org/abs/2501.11701
several references to my BAAVSSC article on thisCheers
RobinAnd another paper
“Bridging the Gap: OPTICAM Reveals the Hidden Spin of the WZ Sge Star GOTO 065054.49+593624.51”
https://arxiv.org/abs/2501.11669
(Detection of a 148s periodic signal in high cadence photometry)Chrome win 10 here. I stay logged in to the BAA site if I close the tab but keep the browser open but it logs me out immediately when the browser is closed. Many websites/forums give the choice to be remembered or not (which IMO is the best arrangement) while with others (like Amazon for example and soon Outlook) you have to physically sign out unless you are using private browsing.
Preprint now on ArXiv
https://arxiv.org/abs/2501.11524
(Includes some of my spectra taken with ALPY200/600)Cheers
RobinFrom a practical point of view though it would greatly help if there was an option to stay logged in on the website. Trying to view or comment on something which is restricted to members only to have to log in and then be directed away from the page you were viewing is very frustrating.
There seems to be some inconsistency. For example VSSC, Comets Tale and Infinite Worlds are all open access while the I&E, Solar Section and Deep Sky Newsletters are members only. Is this at the discretion of the section director or is it due to where they are located within the website?
Not sure how much Registax has been updated/rewritten over the years but its origin dates back over 20 years now, predating multicore processors in PCs
Meanwhile the observatories around Paranal (including the yet to see first light ELT) face a potential threat from a US backed proposed green energy mega-project
https://skyandtelescope.org/astronomy-news/will-chilean-observatory-lose-its-dark-skiesRobin
In the meantime these systems are being used without oversight or basic checks that any observer should be doing. (The TNS system has no gatekeeper and relies on the accuracy of the submitted data). The issues with this observation are multiple and obvious without needing any further data to anyone with basic knowledge of how transients behave (A mag 14 object which suddenly appears with no sign of a precursor or host galaxy and then stays at identically the same brightness for several weeks should already have raised suspicions.) The ghost negative “missing star” in the (observed – archive) difference image and the double colour star images in the DSS 2 colour archive image of the region made it obvious was going on (even before taking into account the proper motion from Gaia and the 2MASS image showing it in yet another position) yet the operators of this system “followed” it for 4 weeks before finally triggering it as “discovery”.
Jack,
It looks like now you have got the badge off, you also now have to remove the plate underneath which is glued on. The chap here drilled it, screwed in a self tapping screw and pulled it off
https://www.cloudynights.com/topic/648277-disassembling-a-porta-ii/?p=9112803
Cheers
RobinThe rapid decline continues based on Atlas forced photometry
Attachments:
