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6 April 2021 at 11:57 am in reply to: SN 2021hem – an apparently “hostless” supernova in Hercules #584059
Dr Paul Leyland
ParticipantThanks.
Yes, very easily visible. I’ve imaged galaxies in that sort of range.
4 April 2021 at 7:30 pm in reply to: SN 2021hem – an apparently “hostless” supernova in Hercules #584049Dr Paul Leyland
ParticipantHmm, I wonder if it is akin to SN1987A? I doubt that the LMC would be readily visible at that distance.
Dr Paul Leyland
ParticipantDetection of Rotational Variability in Floofy Objects at Optical Wavelength https://arxiv.org/abs/2103.16636Dr Paul Leyland
ParticipantMy offer of assistance from a few months back still stands.
Paul
Dr Paul Leyland
ParticipantThe first Dobsonian I had showed serious spherical aberration.
Worked just fine as a light bucket, which I what I wanted it for.
Dr Paul Leyland
ParticipantYes!
Please try it if you can; you only have a few more days of it being bright enough.
Really regretting not being in La Palma right now.
Dr Paul Leyland
ParticipantFurther: note that the proposed rotation period of only 25 seconds implies that exposures of only a few seconds will be needed to get a good light curve. In practice, this suggests only 0.7m-class or larger telescopes will be able to do this successfully, likely implying the use of robotic telescopes.
Getting colour indices, on the other hand, should be somewhat easier as exposures >25s will average out the rotational behaviour. This could be a productive use of personal telescopes fitted with two or more standard photometric filters.
My thanks to Richard Miles and Tomasz Kwiatkowski for the further information.
Dr Paul Leyland
ParticipantAnd vice versa, in my experience. Over-long USB cables can give connection problems which are sometimes solved by using a powered hub.
Try it both ways, in other words.
Dr Paul Leyland
ParticipantI have absolutely no idea whether this might be an explanation, but I believe that aurorae produce radio waves which can be picked up by radio receivers.
There have been documented cases of unexpected diodes (akin to the good old cat’s whisker) producing audio outputs from AM radio transmissions. A few cases involved mercury amalgam dental fillings, for example.
I wonder whether this may be relevant.
Dr Paul Leyland
ParticipantI’m also tempted, despite my age, but my itinerant lifestyle may make things difficult.
Dr Paul Leyland
ParticipantHave you also tried asking on CN and SGL?
I will ask my Twitter followers.
Dr Paul Leyland
ParticipantYou could always just suck it and see. It shouldn’t take more than one night to take dozens of exposures of a relatively bright star at a variety of settings. Then process them and see what works best for your equipment.
Dr Paul Leyland
ParticipantYou make a good point, but up here in the sub-arctic the night time is very often at or below fridge temperature (~5C). When it doesn’t it often never gets dark at night anyway.
At the opposite extreme, a good calima in La Palma can result in the air temperature being higher than 20C all night and even a good two-stage Peltier cooler can’t get a camera much below -15C. Been there, done that.
Dr Paul Leyland
ParticipantI have an Odroid running Ubuntu and Kstars/EKOS as a proposed replacement TCS. I have been quite unable to find a driver for the dome controller (a Vellman board) and there are still teething problems with the mount (a FS2 controller). All the SX kit works perfectly; not yet tried the focuser. It will be months before I can return to La Palma and try to resolve these issues. 8-(
A Celestron NEXIMAGE 5 purchased via the BAA forum also fails to work under the local Ubuntu installation but I have found a package which claims to contain a driver for the camera.
Other people with more main-stream equipment have no significant problems with Linux-based controllers.
Dr Paul Leyland
ParticipantI whole-heartedly agree!
As already stated, I also generally run in 2×2 binning mode for photometry.
Dr Paul Leyland
ParticipantMy Lodestar 2 works very nicely. Whether it has an abnormally large (or small, for that matter) I couldn’t say.
Dr Paul Leyland
ParticipantI think what we are really saying is that you have to pay attention!
Astrometry could well be different from photometry which could well be different from spectroscopy which could well be different from bare detection which could well be …
To summarize: think about what you wish to achieve and make your decisions in that light.
Dr Paul Leyland
ParticipantRobin, thank you very much for posting the link to http://spiff.rit.edu/richmond/signal.shtml which I had not seen before and have now bookmarked.
Typing in the values for my set-up confirmed my prejudice that the read noise is almost entire unimportant for the photometric work I do, where I generally take 30s to 60s subs and co-add.
Dr Paul Leyland
ParticipantNote with CCD cameras (not CMOS), in camera binning (as opposed to post binning) reduces the read noise as there is only one dose per binned super-pixel
That is true, but the read noise adds in quadrature whereas the signal adds. The post-binning signal to noise ratio per NxN binned pixel is N times that of the unbinned pixels.
That is why I was careful to state that the dynamic range can be improved by a factor of NxN for N-fold post-binning, and not the signal to noise ratio. Sometimes the dynamic range is particularly important, such as when trying to detect extremely low contrast objects for instance.
FWIW, I generally use in-camera binning for photometry and post-binning for simple detection. The reason for the former is primarily for faster download times and smaller image sizes, rather than any read noise consideration. Read and dark noise is so small on my cooled CCD camera that it is completely overwhelmed by photon noise from the object and the sky. It is way down in the noise, to coin a phrase 😉
Entirely agree about the under/over confusion but failed to mention it earlier. I am pleased that you have done so.
Dr Paul Leyland
ParticipantYou can always do post hoc binning. What you can not do is undo any binning already applied.
In particular, performing NxN binning in software afterwards gives you the opportunity to increase your dynamic range N^2 -fold by either summation if you can avoid integer overflow or averaging to a floating point format if you can’t — the two are equivalent from a signal processing point of view.
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