Dave Smith

I think you are probably right Andrew. It is too short for an exoplanet and the magnitude drop is too big also. I have tried to confirm that it is local cloud by looking at the light curve of all the nearest stars but none show the dip? Whatever the cause I don't think it is anything to get excited about. Dave

At least this virus does not stop us going into the garden to do some astronomy. This was from last night. Any suggestions about the small dip in readings about half way through. The comparison stars did not show any variation at that time. Dave

Here are the results of using Peranso. Dave

Thanks very much for that. I will post the results of your XY LMi in your thread. Dave

I tried minima2.7 on this data and it produced a result very close to the predicted value. I'm not sure that Peranso can deal with just one set of results, I will check. So far I have only used it when I have data from different occasions to make a phase diagram and then an accurate period. I will have a play and see what is possible. I would be very happy to share data if it works. Dave

Thanks Andrew. Not quite trial and error. From the quoted magnitude of the star I guessed an exposure from previous experience and then in AstroImageJ tested a sample image to get a profile of the star mainly to check it is not near saturation. After that I just had it running continuously to get as many images as possible in the time. Dave

To have a change from HADS stars as it was clear yet again last night I thought I would try an eclipsing binary. This one was occurring at the right time. It also gives me an excuse to try out the Minima software suggested by @coatesg The predited minimum was at 22.33 UT Now off to play with Minima. Dave

We've had a nice run of clear nights. 5/7 😀 The night before last (Sunday) was to some extent wasted as I had stars rather too close to saturation and so unreliable measurements. I repeated them again last night with much better result. Dave

Very nice. Well done Graeme. Dave

Last night I wanted to do photometry on the HADS star V376 Cam but it has quite a long period (about 3h 20m) and when I looked on my weather app for cloud and rain there was an enormous band of rain approaching from the west which I estimated would take about an hour to arrive. So I decided I would make a start in preparation for another time. As that band of rain approached Essex the part due to hit just fizzled out and as you can see I had 7 hours of clear sky. That sort of thing only happens in dreams. It was still clear when I packed up! I am quite chuffed about the quality of this one. I guess the transparency was much better last night. Dave

I'm usually out on a Thursday evening and before going out the forecast was for it to be clear until around 11pm so not enough to get much done when I return home. However the forecast changed and it was clear for a good part of the night. Hence the results below. Dave

Thanks Graeme. I do have Peranso and have found it useful for combining results from different occasions to get a phase diagram and hence an accurate time period. However I haven't tackled an eclipsing binary for some time now. HADS stars are so convenient in that you can start at any time. Dave

Wow you have been busy! That Minima software looks interesting, I must give it a try. Dave

Variable star V460 Andromeda Multiple 60 sec exposures binned 2x2 through my Celestron 11" EdgeHD scope last night. The increased noise towards the end is due to the star approaching the northern horizon. Dave

I'm inclined to agree with that. Even if a light pollution filter made a difference I don't consider it worth spending on one just for that reason. There are more than enough stars within my range to keep me busy. Dave

Yes and in this case I believe there is some relatively rapid changes. That is a very interesting idea, thank you. When I did this sort of work with my 90mm refractor I did as standard have a LP filter in the optical train. I need to go and check my present setup, but I don't think I do this at the moment. When this storm has passed I will go and check. If not I do have space on my filter wheel to add one. Normally I use a V filter but when the star is so dim that filter is not used to increase the possible signal. Dave

Earlier this week I attempted to measure the variable star U Leo which is a current BAA project but found it at magnitude around 17 right on the limit of my observation. I am using my Celestron 11" edgeHD scope at F7 and an Atik 460EX CCD camera unfiltered and binned 4x4. The sky background was showing as around 32 000 ADU with a 2 minute exposure and the star hardly showing. I was advised that they were worth submitting to the database (BAA and AAVSO) and they are in a comparable region. No detail is revealed so not worth showing the plot here. I have seen somewhere a chart showing aperture of scope versus range of magnitudes that can be measured. Can anyone point me to this? Dave

Thanks Luke. I stopped using Muniwin some time ago when AstroImageJ became available. Muniwin seemed to have a mind of its own and it was not clear (to me anyway) what the various settings did. There were occasions when only half of the measurements were accepted with no apparent logic. AstroImageJ is free and works well. See my tutorial at the beginning of this section. Dave

Well done Graeme. Dave

Tuesday night looked very promising. I started with V965 Cepheus which has a period of around 2 hours. I still find it mind boggling that a star can pulsate with such a short time scale. Having taken enough readings for two cycles I moved on to V973 Cepheus which has a period of 1.9 hours but unfortunately the sky was becoming rather misty until it finally prevented any further readings. Both were taken with a Johnson V filter. V965 Cep with 2 min 2x2 binned images and V973 Cep with 30s 2x2 binned images Dave

Nice and clear last night and I wanted to experiment with using binning (x2) for variables. This one has a period of 3.2 hours. The exposures were of 120s through a C11 with 0.7x reducer. Dave

That first one at mag 15 looks tricky. What scope and exposure time are you using? I like the second one. Dave

You could come to the VSS day if "Rain stops play" 😀 Dave

Thanks Stu. I didn't realise I had a back problem because the pain was in the legs. Hopefully all will be well before long. There is a whole group of stars, HADS stars (High Amplitude Delta Scuti stars), with these short time periods. It does seem a bit mind boggling that such large objects can be oscillating in and out at such a frequency. This particular star seems to have more than one frequency of resonance. Dave

Many thanks Graeme. My problems are all due to getting old 🙁 . By the way, are you by any chance going to the BAA Winchester weekend or the VSS meeting in Northampton on 9 May? Dave