Wow! Congratulations! That was something!
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jrista said:Taurid Meteor through the heart of Pleiades
This new ASI1600 is an incredibly sensitive camera, so it's forced me to use shorter exposures. I was acquiring short 10 second L filter subs two nights ago, and while blinking through them with PixInsight to find and discard bad subs, I noticed something bright flash through one of the frames. When I investigated more closely, I found this amazing sequence:
Meteorite, I believe a Taurid, a minor meteor shower which peaked tonight, zipped through my frames leaving a smoking plasma trail behind, corkscrewing off the right side of the field.
jrista said:Taurid Meteor through the heart of Pleiades
This new ASI1600 is an incredibly sensitive camera, so it's forced me to use shorter exposures. I was acquiring short 10 second L filter subs two nights ago, and while blinking through them with PixInsight to find and discard bad subs, I noticed something bright flash through one of the frames.
rrcphoto said:jrista said:Taurid Meteor through the heart of Pleiades
This new ASI1600 is an incredibly sensitive camera, so it's forced me to use shorter exposures. I was acquiring short 10 second L filter subs two nights ago, and while blinking through them with PixInsight to find and discard bad subs, I noticed something bright flash through one of the frames.
I was checking out that camera. there were some reports that it has an IR filter stack attached - was that the case with yours? there was confusion over whether or not that the was the color versus monochrome imager though.
I was thinking of getting the color - simply because of hyperstar compability.
StudentOfLight said:Experimenting with the 80D and the 135mm f/2. This is a interesting combo as it puts more pixels on target than my Tamron 70-200m with the 6D. The 80D also has a new low read-noise sensor which I thought could be good for deep sky. To compensate for the lower full-well capacity of the smaller pixels I used ISO 800 instead of my typical ISO 3200 or ISO 6400. Not happy with the amount of highlight detail. Maybe the lens is just not sharp enough for 3x Drizzle??? Hopefully my local currency will improve a bit more then I can get a tracking mount.
The most notable feature in the LMC is the Tarantula Nebula https://en.wikipedia.org/wiki/Tarantula_Nebula, which is the most active star-forming region in our local group of galaxies. The 200 parsec size of this extra-galactic object is hard to fathom. To put it in context, if it were as close as the Orion nebula then it would appear 40 times larger than the full moon in the night sky.
StudentOfLight said:I generally do not have sufficient focal length for deep sky objects so I usually end up drizzling the interesting portion of frame. I previously shot the LMC under similar LP conditions with my 6D and Tamron 70-200 at 70mm (102x6s).
LMC (102x 6s) by Omesh Singh, on Flickr
The most notable difference is that the stars were not round with the 6D+Tamron image. I suspect it is due to some residual tilt in the IS mechanism as I always get stretching in my images from top left to bottom right.
Regarding ideal settings for the 80D, I read this on DPReview:
https://www.dpreview.com/forums/post/57481095
I'm interested to see how it does at ISO100-200 with long exposure tracked images.
Wouldn't you get the best results on an 80D with an ETTR approach at a lower ISO setting?
Could I share a couple of RAW files with you to help determine the best ISO to use with the 80D? There is so little info out on this camera. Just tell me what you need.jrista said:StudentOfLight said:I generally do not have sufficient focal length for deep sky objects so I usually end up drizzling the interesting portion of frame. I previously shot the LMC under similar LP conditions with my 6D and Tamron 70-200 at 70mm (102x6s).
LMC (102x 6s) by Omesh Singh, on Flickr
The most notable difference is that the stars were not round with the 6D+Tamron image. I suspect it is due to some residual tilt in the IS mechanism as I always get stretching in my images from top left to bottom right.
Regarding ideal settings for the 80D, I read this on DPReview:
https://www.dpreview.com/forums/post/57481095
I'm interested to see how it does at ISO100-200 with long exposure tracked images.
Wouldn't you get the best results on an 80D with an ETTR approach at a lower ISO setting?
Hmm. I am not sure that Jerry nor Roger are correct in that post. Canon has always, to my knowledge, used a 512 ADU 14-bit offset. I've been measuring DSLR data for years now, and I always make sure to measure in the proper bit depth, and across countless Canon DSLRs, I've measured a bias offset of 512 ADU (14-bit).
I think people make the common mistake of converting the original RAW DSLR data into 16-bit, or the mistake of processing it in 16-bit space. Interestingly, the conversion factor between 14-bit and 16-bit is 4 (2^2), and 512*4 = 2048. I do not believe, at least not with any cameras since the 5D II or around there, that Canon has used a 2048 ADU offset.
If Roger is correct that Canon is using a lower offset at ISO 100 and 200, my guess is it would be a 128 ADU 14-bit offset. With lower read noise, that would certainly be possible. It also seems logical to keep a larger offset at higher ISO settings, which amplify noise more, and need more "buffer" room to avoid clipping the signal anyway. I haven't read anything specific to that effect myself, so I honestly cannot say what Canon may have really done with the 80D.
My opinion on which ISO is best is this, and actually in line with Roger's opinions most of the time:
It is better to "oversample" each electron of true signal, than to "undersample" them. By that I mean, you want your gain to be high enough that you are amplifying each electron by a factor of two, if not more. At low ISO, you are, for lack of a better term, "attenuating" the signal, since in most cases you must convert many electrons into each output ADU (analog to digital unit). This is low gain, high quantization. You are quantizing, or grouping together and effectively "squashing", many electrons together and losing a certain amount of information they held when they were separate and distinct.
This is not ideal for astrophotography, since we are chasing extremely faint details, and every single electron matters. It is entirely possible that at a low ISO, say ISO 100, you are converting 2, 3, 5, maybe even more electrons (depends on the pixel size and architecture) into one ADU. Technically speaking, it is possible to recover precision by stacking lots and lots of subs. However that is at odds with using a lower ISO, which requires longer exposures, which means you tend to get fewer of them.
While from a read noise standpoint alone, you may have low read noise at low ISO with a supposedly "isoless" camera, from an actual functional standpoint, ISO 100 is absolutely NOT the same as ISO 800, or 1600, etc. ISO 100 is going to have poor representation of fine, faint details. ISO 1600 is going to have good representation of fine details. Quantization error is also usually going to be lower at higher gain.
To preserve the full fidelity of the signal, and not lose any of the fineness of detail that each and every individual electron holds, you want to use a higher ISO. You generally want to "sample" each electron by a factor of 2-3x, meaning for each electron "input" into the ADC unit, you want to get 2-3 ADU out. There is always going to be some amount of quantization error (not even unity gain is free of quantization error, and it usually isn't selectable anyway), however relative to the scale of each electron at a higher gain, quantization error tends to be much smaller than at lower gain. So there are benefits all around when using higher gain, and all of them are more conducive to acquiring the best data for the kind of ultra faint signals you get with astrophotography.
I don't ever recommend using low ISO for AP anymore. I also don't generally recommend using extremely high ISO settings, as you not only lose dynamic range, but FPN has a gain component and it can get much worse at higher ISO settings. This is particularly true of any secondary amplifiers are used in downstream electronics, which will amplify any signal and noise coming out of the pixels (and Canon definitely uses a secondary amp at high ISO settings). The sweet spot is usually ISO 800, 1600, maybe 3200 on some select few cameras with low FPN.
ISO64 said:Jon,
That smokin' trail is really the first dynamic astronomy photo that I've seen!!! As they say, happy go lucky!
Thanks for sharing.
jrista said:Andromeda Galaxy
One of my latest images. This is a classic object, but one of the first LRGB images I've made with my new mono camera. Full fill factor for both the luminance (L) channel, which is where most of the integration time goes and where you optimize SNR, detail, etc. And full fill factor (means 100% of the pixels are used) for all three color channels. This is in contrast to a normal DSLR, which has a 50% green and 25% red/blue fill factor, which greatly reduces the sensitivity in those channels.
The data is still light polluted, however I was a bit surprised at how nice it turned out despite that fact: