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coatesg

V416 UMa - Faint, Scuppered by clouds!

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A run at capturing V416 UMa this evening, which is a short period HADS (~1.52hrs) - it's a faint one (mag 13.9-14.5 from my results) and I wanted to have a go at using the G filter and see what kind of exposure is required for this kind of magnitude star. (I have a Johnson V but haven't had chance to take the FW apart to install as yet and to refocus the OAG as a result)

I ended up using 120sec exposures - it'll be interesting to see if this is fine enough to use for timing studies (will await feedback...). Using the APASS DR9 figures for the check stars (from VizieR), I get reasonably close figures, so think that the exposures are about right given the lack of brightness for this one - just whether the timing is good enough. (For some reason I can't get the absolute magnitudes out of AIJ to plot - not sure why?)

Shame the clouds rolled in at the end and prevented me from getting the rise back to maximum to complete the whole cycle - I wasn't that far off...! (the points at the end of the run go completely haywire as a result of the decreased and variable flux). 

Measurements.png.412a2f0888eadb4db2b182511d930c39.png

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As you say, shame about the clouds cutting the session short. But the data you got is interesting. I don't know this variable at all, but it is clear from your data that it has a steep climb to max and then a leisurely drop back again. Must go and look it up. What software are you using?

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Graph is plotted from AstroimageJ - I make the master flats and darks in PI, then use AIJ for reduction and analysis. @Dave Smith has a good tutorial pinned in this board!

This looks like a fairly typical Delta Scuti curve - asymmetric in appearance, though you're right in that it is a rapid climb over >0.4mags.

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I like the shape of that curve. The cloud certaily is showing its effect on the last readings.

Patrick will likely find this useful. He uses a curve fitting analysis which doesn't require a whole period, although he does prefer a period or more.

I also have not been able to get AIJ to plot absolute magnitudes, although I must admit that I haven't really tried. My technique is to generate a BAA report and import that into Excel where there is much flexibility to how it is plotted, labels etc

You seem to have well and truly been hooked onto variable stars ??

Dave

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I've had AIJ working before with abs mags, but not now! No idea at present!

It's interesting work - last night if imaging, I would have been swearing that I set up, and then only got an hour and a bit of data... but that might well be enough for a meaningful contribution here ?

 

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OK - sussed it out. Here's the calculated magnitudes with reference star names (NB: errors in APASS DR9 magnitudes aren't included here). 

Measurements.png.6aa350d17b7b8b3c64dc203918993d87.png

Here's the field - the whopping diffraction spike is from Mizar, about 1.2 degrees away....

field.png.7dd970a28e8b802b27c9621a9f7f7ee6.png

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Presumably if you didn't plot the comparison stars then it will have a better scalefor the main star.

Dave

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Yep - without the two refs at the top, I can change the y-min, which will emphasise the curve. Interesting to prove why the right amount of signal results in smaller error bars (Poisson noise, etc)

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