Hi!
In working with time series analysis of V0627 Peg, I have recently run into some new issues:
I have saved a sequence for the target star and comparison stars, by working with one of my images. THen, when opening another one, the target variable is NOT identified. This happens even though it is clearly within the aperture indicating where it should be - the aperture is colored red, as seemingly no star is found - despite the star clearly being there.
I have calibrated the files and plate solved with ASTAP. Images taken under summer sky in Sweden, so bright background. Even so, VPhot have no problems identifying the target star on individual images - but when reusing the sequence, it fails. And thus my time series fails.
See attached png for how it looks in VPhot.
Anyone recognize this? Any ideas on what to do?
EDIT: after redoing the plate solve in ASTAP and deleting and redoing the sequence, it seems to work better.
Edit again: better but still not good. Time series fails,
Magnus
Hi!
More to this: Today I have another series, from last night. Now I am getting "not detected" for my I-band images. As I understand this, the target is not identified by VPhot.
However, clicking on any of those images, in the results view in time series analysis process, that is, where I get this series of "Not detected", I come to the individual image with the sequence chosen. And there it is! Easily detected, SNR between 30 and 75-ish. Image after image. How come it is listed as "Not detected" when in fact it is detected?
Any help on this is very highly appreciated.
Magnus
Magnus:
Share the images to me at MZK. How were they plate-solved? What is your minimum SNR setting on the time series page?
Reply with some screenshots that show the problem.
Ken
And I've shared my I-band images with you. The whole batch.
Minimum SNR has been everything from 10 to 50, no change.
Magnus
Magnus:
The RA/Dec is not quite where it should be, thus the not found red circle. Notice the slight offset there. Not centered exactly.
Increase/expand the search radius under Tool>Settings AND on the Time Series page.
Ken
Hi!
Thanks for replying! I've been trying to get this to work a lot, so maybe some things get mixed up in the process. The first small image I sent, was with images calibrated and platesolved by ASTAP. Later, I switched to calibrating with AstroimageJ but still plate-solving with ASTAP (my only offline option for the moment).
After that, the first batch of images actually worked! Just waiting a few hours seems to have made a difference. That batch is now reported.
The later problem still remains: that my I-band images from last night are reported as "not detected". These are calibrated by AIJ and platesolves with ASTAP.
First screenshot shows the list of images in the time series process. No stars detected in any image. Search radius set to 15, both in Tools - Settings - Search radius and in Time series settings.
Second screenshot shows the last image (top of the list) when I click on the link in the list in the first screenshot (makes sense?). Here the target as well as comps are clearly identified.
Seems I cannot attach files, but they are here, in a dropbox-folder:
https://www.dropbox.com/sh/0p5nnu3o04grq2t/AAD4lf3AKEk9NIBlnZLMu4sJa?dl=0
Does this help to make sense of it? It's bedtime here, but I'll be back in 9 hrs time.
Magnus
Magnus:
Any reason you didn't run 60s exposures for these images? Would be nice if SNRs were more than 100. In general images are faint.
I got a sequence set up. Ran a time series.
Something strange happens on every other image. They alternate brighter/fainter flux??
Ken
Yes, I agree that these…
Hi!
Yes, I agree that these are faint and that 60 secs could have been good. I'm wary about not getting the target saturated, which is a bit tricky with the bright summer skies here. However, these are far from that. I think that there were high thin clouds this night, contributing to the faintness of them - and that is what makes the flux fluctuate, I suspect. I was not awake, I set it all up and then went to sleep, so only saw the SNR after the fact. There is also a whole lot deleted in the end, because of clouds coming in.
Have you been able to make a time series of them and measure? I till have the issue of them being easily measured individually, but the time series says it cannot detect them.
Magnus
An update: I now…
Hi again!
An update: I now have installed and learned the basics of Lesvephotometry, and with that, I can get a time series of my I-band images. Sure, there is not a good SNR and the sky is brighter in Ir than in B, but it seems to work nicely. However, I am not sure about some of the settings so hesitant to upload the report just yet (unsure about the BZERO and BSCALE settings, and wonder if they might influence the results if set wrongly).
The only thing I had to adjust in Lesvephotometry was to make sure the reference and check stars have I-band magnitudes and allow comparison stars to have SNR as low as 20 (errors are consequently larger), but no problem in locating the stars. I use Pinpoint to platesolve in Lesvephotometry.
Does this add something to the question of why I'm having difficulty with VPhot?
Magnus