Dave Smith

It's worse than that really. Having opened the dome in the right direction, I control everything from indoors in the warm. While it is imaging I can be eating a meal, watching TV or having a whisky !! It can go wrong as it did last week, one of the two wasted nights, when I fell asleep for two hours to find that the scope must have hit the mount and had done its own meridian flip. I didn't realise it could do that!! Dave

This is one I like as it is quite close to Polaris and so I don't have to worry about moving the dome or to lift it on to the POD table. Dave

At last I have managed a long session on this star without any saturation. This one seems much more symmetrical than normal HADS stars (steep rise and slower decline) Dave

Good work Graeme. Any idea why the second one is more noisy even though it is brighter? Dave

Thanks Graeme. See my response to Whirlwind. At least some good news, Patrick has been able to extract a period from the results which fits in with the previous pattern. Dave

Thank you very much for your reply. My initial thought was that your possible explanation was not the reason because I had tested the signal strength at the beginning of measurements but then I examined the output file and found that a very large proportion of my readings were saturated but not at the beginning. It looks as if the sky became more transparent rather than high cloud appearing. It is a lesson learnt although rather severe to have two nights wasted due to the same error. I am rather relieved that the cause has been revealed. Without your post I would not have thought to check that out, so thanks again. Dave

I was in two minds as to whether I should post this or not. I have decided that it is worth showing that everything does not always go smoothly with variable star photometry. This particular star has a period of nearly 5 hours and so to get a decent range requires most of the night. Recently the sky has been clear all night and day so a good opportunity to get results on this long period HADS star. Here are the results for the first night, Sunday night 22/23 March 2020. It started well but then YUCK. The comparison star plots also showed increased noise. There was a little mist that night and so I put it down to that. The next night was also clear so I repeated measurements on the same star. Equally YUCKY !!! That night there was no cloud (that I could see) and again no jet stream. Wondering if it was a software problem I did the analysis again using MaximDL but it gave the same result. By the way, in both cases the exposures were for 60 seconds binned 2x2. Last night was also clear but I couldn't face doing it again so I had a play with the guiding of my scope. So far with variable stars I have not used guiding with my EQ8 mount but there is a very slow drift which I wanted to eliminate, although not urgent for my variable star work. Ho Hum I do need a good night of readings. I have not submitted the above results to the BAA or AAVSO. Dave

Well done Graeme, keep up the good work. This is the first HADS star I ever tried but at that time was unaware of the project. I have spent two nights this week on V467 Dra which has a very long period but unfortunately the seeing/transparency must have been rubbish as the results after a short decent period were very scattered. I did submit them to Patrick but I guess he was unable to get the period as they haven't appeared on his chart. Dave

Thanks. I would agree with that. I have also observed this star twice now and nothing like that on the first occasion. Dave

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