Here is a quick crop of what I got yesterday 7th November. No RGB data yet though. I was hoping it would stay clear tonight but no luck.
Exposure: L 42 x 5min, total 3hrs 30mins @ -30C
Telescope: 10" Serrurier Truss Newtonian f/5
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from my observatory in Auckland, New Zealand
Here is a quick crop of what I got yesterday 7th November. No RGB data yet though. I was hoping it would stay clear tonight but no luck.
Exposure: L 42 x 5min, total 3hrs 30mins @ -30C
Telescope: 10" Serrurier Truss Newtonian f/5
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from my observatory in Auckland, New Zealand
Excellent image You have a flat undistorted field I yearn for
Thanks Roger, and that magnitude is certainly fascinating.
With NGC1365 being 56 million light years away I calculate an absolute magnitude of -18.87!
So if SN2012fr was in the place of say Betelgeuse, its apparent magnitude would be -12.39. More or less like the full Moon!
Thanks Roger, and that magnitude is certainly fascinating.
With NGC1365 being 56 million light years away I calculate an absolute magnitude of -18.87!
So if SN2012fr was in the place of say Betelgeuse, its apparent magnitude would be -12.39. More or less like the full Moon!
That would be bright
I haven't been following closely, I think it is still increasing in bightness isn't it? (It's not just my 12.2 is an error?).
It sometimes takes me a while to catch on to these events, but I have now scripted it in my nightly script, so it will be interesting to graph the brightness over it's life span at the end.
I wonder what those in the know think of this magnitude estimate?
Camera is NABG, ST8.
Taken from a single reduced 3 minute exposure.
The rest is probably self evident from the screen shot.
Roger.
Roger
What filter if any was the image taken with?
I forget what database astrometrica uses for comp stars but it is different to the standard stars on the AAVSO site. These are probably better to use as they are reproducable betreen observers.
The aperture needs to be bigger. I usually use 3 or 4 x the fwhm as this gives more reproducable results.
Cheers
Terry
Roger
What filter if any was the image taken with?
I forget what database astrometrica uses for comp stars but it is different to the standard stars on the AAVSO site. These are probably better to use as they are reproducable betreen observers.
The aperture needs to be bigger. I usually use 3 or 4 x the fwhm as this gives more reproducable results.
Cheers
Terry
Hi Terry,
In Astrometrica you can choose from the usual databases. At the moment I have it set to NOMAD, as the other option I did have it set to was UCAC3. For some reson my local UCAC2 wasn't working last night.
Could you clarify what you mean by bigger aperture? Are you suggesting it is better to estimate the magnitude from a stack of exposures? Not sure what you mean by using 3 or 4 x the FWHM sorry
In Astrometrica you can choose from the usual databases. At the moment I have it set to NOMAD, as the other option I did have it set to was UCAC3. For some reson my local UCAC2 wasn't working last night.
Could you clarify what you mean by bigger aperture? Are you suggesting it is better to estimate the magnitude from a stack of exposures? Not sure what you mean by using 3 or 4 x the FWHM sorry
What I mean by bigger aperture is the size of the circle that the stars flux is measured. In your image there is clearly lots of the star flux outside the little circle. Your measured FWHM os 3.5arcsec so the circle needs to be 3 or 4 x this size. You will need to work out how many pixels this is as I don't know the resolution of your scope.
The UCAC3 databases are good but the accuracy depends on the filter being correct.
There is some advantage to averaging a few exposures to improve noise but you are probably better to measure individual exposures and average the results.
Any form of "stretching" of the exposure will make photometry measurements unreliable so just use plain dark and flat processed exposures. Flats are very important and must be used for accurate photometry.
cheers
Ahh, thanks, I understand better now. I haven't noticed if that circle can have its diameter changed in Astrometrica.
I assumed it would calculate the magnitude based on the brightness of other stars in the image and then using the single brightest pixel value from the estimate star, I wonder why having more surrounding the star being included in the estimate has n impact? I should RTFM on the subject.
Flats, stretching, etc - have that covered.
Thanks,
Roger.
Quote:
Originally Posted by Terry B
What I mean by bigger aperture is the size of the circle that the stars flux is measured. In your image there is clearly lots of the star flux outside the little circle. Your measured FWHM os 3.5arcsec so the circle needs to be 3 or 4 x this size. You will need to work out how many pixels this is as I don't know the resolution of your scope.
The UCAC3 databases are good but the accuracy depends on the filter being correct.
There is some advantage to averaging a few exposures to improve noise but you are probably better to measure individual exposures and average the results.
Any form of "stretching" of the exposure will make photometry measurements unreliable so just use plain dark and flat processed exposures. Flats are very important and must be used for accurate photometry.
cheers
...
I assumed it would calculate the magnitude based on the brightness of other stars in the image and then using the single brightest pixel value from the estimate star, I wonder why having more surrounding the star being included in the estimate has n impact? I should RTFM on the subject....
I think Astrometrica doesn't use aperture photometry, it fits a point spread function (PSF) to the pixels.
I've just finished a high resolution image of NGC 1365 with SN2012fr, using the L data I got on the 7th plus 3 hours of RGB from 9th Nov. Attached is a downscaled version of the image (a thread with the full res image will be up soon, but right now I got to go to bed )
It's quite spectacular how intensely blue the SN is!
I'm still waiting for our bad weather to clear up so I can take a look visually- just looking at the weather forecast, Wed & Thurs are looking good for Brisbane.
I need to catch this SN in in its peak- haven't much time by the looks of it.
Another clear sky last night, so a chance to gather more photometry data on this SN.
On the 9th, it looked like it might have flattened out, but last night (10th) it was brighter, and still rising. R-band magnitude 11.90 +/- 0.03
For those wanting to view this visually (I'm thinking of you, Suzy), I've seen reports the SN is easily visible in a 10", but only the core of the galaxy is visible. With a goto scope, you are laughing. If you are manually pushing your Dob, I guess you need to be armed with dark skies and some charts.
Slightly embarrassed to say personally I have not been inclined to actually look through the 'sope -- then I'd have to take the flats again!
Ron spotted it easily from his dark site thru an 8" and he seems to think it should remain bright for a couple of weeks, so that sound like it's back in keeping with what he said; I got worried eeeek when it looked like it was flattening out re your prev. post. If I nab it in in my 10" the next few days at it's peak, I'll be very happy.
I don't expect to see any arms from my light polluted site, just the core as you said. Which is what's going to make my job harder I think.
I have push-to-go (Argo Narvis), but with faint/small objects that can be just on the threshold of visibility, I find a star chart is useful so I know where to look harder in that area. A map showing a good deep starfield also helps to determine/confirm it's the SN in the right area and not just a faint star. And often the object can be put just out of field of the ep by the Argo- so sometimes hunting is involved, esp. if it's tiny & faint.
Go on Ivan! Do it! It should be quite a rewarding experience seeing this thru both means. Allow that eye to bathe in all those photos that took 56 million light years to hit your eyeball! It's a rush I tell you!
I've just learned that this galalxy is called "The Great Barred Spiral Galaxy" so that in itself is worthy of a look for me!
You have a flat undistorted field I yearn for 
so no light magnitude estimate for me! 
It should be quite a rewarding experience seeing this thru both means. Allow that eye to bathe in all those photos that took 56 million light years to hit your eyeball! It's a rush I tell you! 
