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I’ve just measured it as 7.54 (2021 June 13 22:51) compared to 5.94 at this time last night. Both unfiltered ref to Gaia DR2 G so somewhere between V and R. That’s a fall of 1.6 mags in day. That’s pretty fast. I remember photographing V838 Her (George Alcock’s last nova) in 1991 but only getting it on one occasion since it faded so fast.
Another bright nova! Here’s my image https://britastro.org/observations/observation.php?id=20210612_231222_b0ed29be83050b55. I’ve taken some 1s exposures too which I’ll measure later.
Here are my edited highlights from yeasterday: https://youtu.be/MoRfhjLTS8k. From Chelmsford I managed about 15 mins at the beginning and end but it was cloudy for the rest of the time.
I too have ordered a copy. Tom’s unsolicited email campaign is clearly working! I wonder if the plot includes a hero who drives his car at supersonic speeds but is shopped to the local feds by a trusted colleague?
Gary. Aren’t you at the ground? I was looking forward to an eclipse drawing from the posh stand at Edgbaston.
Very cloudy in Chelmsford at the moment after a cloudless day yesterday. Weather satellite shows it clear at the moment up the east coast and in the North Sea and a few clear patches elsewhere. Fingers crossed for some breaks later.
This is the link for my eclipse livestream on Thursday morning https://youtu.be/DtqzzB5xAF8. The forecast for here looks encouraging at the moment.
Here is a speeded up video of your flares from Chelmsford. I have lots of cheap IP cameras pointing in all directions recording video in a 7-day cycle so I still had this from Sunday morning. There is quite of lot of cloud but Altair is visible just left of centre and Delphinus is visible through the cloud. I’m around 37 miles SW of you as the crow flies so my flares were probably not as impressive as yours.
This is the set-up I’m using for the live stream. It is a Megrez 72 FD refractor on a NEQ6 with an IP camera module which feeds video directly into OBS via a long PoE Ethernet cable and then on to Youtube. It’s the first time I’ve tried this and it was far too easy! Hopefully the weather will play ball on Thursday.
Here is an example file which gives the JD zero date: http://www.nickdjames.com/Transfers/ngc6888_n_solved.fit.gz
Max, Thanks. That works and this looks really powerful, particularly the ability to measure multiple variables in a field and generate automatic reports. My only remaining comment is that I get strange timestamps:
ES UMa, -4713-11-24 12:00:00.000 UTC, G = 10.91 ± 0.11
-4713 is something like JD = 0. The FITS file I’m measuring includes the record:
DATE-OBS= ‘2021-05-25T22:53:18’ / Start time of stacked exposure
Nick.
Hi Max,
I’ve downloaded 0.15 and am running it under Windows 10. It does the PSF photometry but then fails when I try to download catalogue stars:
694 ‘charmap’ codec can’t encode character ‘u03b1’ in position 25: character maps to <undefined>
Any idea what this might be?
Nick.
Maxim,
Just to let you know that I’ve been using the program but haven’t had a chance to look at the SNR details yet. I’ll do that when I get time.
Nick.
This comet is now quite a nice target for small, widefield instruments. I imaged it with a 90mm refractor last night.
There is an old discussion on calculating SNR here. Basically I ended up calculating all of the non-photon sources directly by measuring the RMS value in the sky estimation. To calculate the photon, sqrt(N), noise you need to know the camera gain. I’ve implemented this in an automated aperture photometry tool that I use and it seems reasonable to me.
Thanks. That works very well. I get a pretty good ensemble fit against Gaia G and a magnitude for SN 2021hpr of 14.21. This compares to 14.29 using my aperture photometry tool, presumably affected by the galaxy background. I think the SNR you quote is too low though. I get 168, you have 27. SNR is a difficult thing to calculate correctly. How do you do it?
Maxim – Thanks, I’m almost there. I had forgotten the “Get comparison stars” step! Now I get a fit. The only problem remaining is when I click on the object the flux/magnitude etc are all zero. What am I doing wrong?
One other question – Am I right that the ensemble fit graph is upside down, i.e. the brightest magnitudes are in the lower left corner. Not a problem but I would just like to understand.
