W UMa - first variable star observation

[Paz]

I've been put off variable star observing due to the prevalence of bad weather making it hard to string observations together but I noticed W Ursa Major was in a good spot in the sky for observing almost any time of night for some time to come and it varies a lot over a short period so I have decided to give it a go.

I took out the ST120 with a 32mm plossl and that was all. Finding it wasnt too bad apart from it being at about 74 degrees altitude which is higher altitude than I normally go for. Luckily I had my observing chair out so it was ok.

I hopped over from Upsilon and found a rhomboid of 4 stars that it forms a corner of with a pair of mag 8.9 stars and a mag 6.5 star and I compared it to similar brightnes stars nearby using sky safari to check their brightness. I made it dimmer than mag 8.2 and brighter than mag 8.9. This was at 22:30.

After a break for my (late) tea I went back out for one more go and compared it to mag 8.7 and 8.5 nearby stars. I made it brighter than both. This was at 23:20. It was super high by this time  (80 degrèes), I was off my chair and grubbing around on my knees!

So I make it between 8.2 and 8.5.

I reaslied I should have checked it the second time against the 8.2 star in case it had changed  in the mean time, I understand it varies from aboutn mag 7.8 to 8.5.

My measurements are not very refined but they are a start and Im in the right ballpark(!). I plan to check it out when the chances arise and try to string together the pattern.

Altogether a good session, no need for dark skies, or dark adaptation, any expensive kit either, and it didnt take much time to do.

[MarsG76]

Cool project.. and nice report....

If I would try to track the b rightness of a variable star, I think I would go the photography route.. take a few photos of the variable star and it surrounding stars (if any) at various exposures, than repeat the photos a few hours later.... the stars around the variable could be used as calibration and this way the brightness change of the variable star would stand out... if it changes intensity.

[DHEB]

Observing and estimating variable stars is a joy, and also one that contributes to science if you report your observations to an organisation.

You seem to have started well: a circumpolar star that may be followed the whole year and that is within the range of your scope. I suggest you spend some time "calibrating" yourself, comparing your observations to those of others. Watch out for very red stars, you may fall prey of the Purkinje effect.

Have you read this fine introduction?

Goodluck and welcome to this fascinating world!

[Demonperformer]

Excellent project. A reasonable magnitude variation and a short period (just over 8 hours) with a "double dip". Good luck for your future observations.

[DHEB]

On the other hand, @Paz if you are interested in visual estimations I suggest you start with a star that has a longer period and a larger range, and that many observers observe, for example Mira, R Leo or khi Cyg. In that way you can learn to estimate a relatively easy and well observed star, having at hand lots of observations made by others to compare yours, and to learn to observe in a large range of magnitudes.

Just my two cents.

[Paz]

Thanks for the comments, Ive had a look at the aavso site which looks very good, and im going to pick another couplem in the same area that i can view at most times of the evening for the next few months and give them a go.

[Demonperformer]

Can I suggest Z UMa (within 'the bowl' and fairly close to δ?) as an interesting one to watch? It's ability to surprise may add that extra bit of zest to your variable observing schedule.

[DHEB]

5 hours ago, Demonperformer said:

Can I suggest Z UMa (within 'the bowl' and fairly close to δ?) as an interesting one to watch? It's ability to surprise may add that extra bit of zest to your variable observing schedule.

Oh yes, and T and S too.