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Dave Smith

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About Dave Smith

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    White Dwarf

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    Maldon, Essex
  1. 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
  2. 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
  3. 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
  4. 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
  5. 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
  6. 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
  7. That first one at mag 15 looks tricky. What scope and exposure time are you using? I like the second one. Dave
  8. You could come to the VSS day if "Rain stops play" Dave
  9. 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
  10. 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
  11. This is my first variable star measurement since last March. This is largely due to me having problems with Sciatica. I had keyhole surgery on my back at the end of November and am finally ready to continue looking at these fascinating objects. I thought it wise to tackle a familiar object first. It is amazing what one forgets after a lapse, e.g. I initially forgot to turn the camera cooling on and twice had to refer to my own tutorial to use the software! Dave
  12. Well done Graeme. Must feel good to be back again. I was also out last night looking at a HADS star, my first since March last year!!! I will explain later when I finish processing. Dave
  13. That is an interesting curve. Any idea why two peaks? Dave
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