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RobB

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Everything posted by RobB

  1. I use a hot air gun and solder paste for my smd components.
  2. Wow !! - I'm still waiting for some clear nights to get my first DSO after 20 years away from the hobby. I hope it is half as good as yours!
  3. I was watching this AstroBackyard tutorial last night (trying to soak up as much info before I begin my baby steps in astrophotography). Trevor, at one point, goes into removing halos. https://youtu.be/5GgruZ-1zQ0. I think just after halfway.
  4. I would have thought a local Astronomical Society would take them, assuming they have the storage facilities?
  5. Currently away from home and haven't applied any flats to the image. The processed image above was not from the FITS files but from the jpg. I need to install a FITS application but as I'm connecting my laptop via my mobile I'll wait until late tonight when I get home. Maybe the lines will go away. Not too worried myself but it would be good if they could investigate the issue. I'm using the course as a v.small taster of doing a longer AstroPhysics course. i.e. can I find the time to study. Maybe the PGDip Astronomy from York.
  6. Hopefully I'll be able to take one with my own telescope this weekend although South Devon isn't particularly known for clear skies.
  7. My first image in about 20 years! Taken with the Open University 14" SCT (COAST) on Tenerife last night. A single 120sec frame, BVR filter. A little bit fiddling of light levels by me (total novice here). I'm running thru the short FREE 8 week course "Astronomy with an online telescope"
  8. Hi Leon Also a Radio Ham and also looking to get into Radio Astronomy. Rob
  9. Some of the GPS Disciplined Oven controlled crystal oscillators I've seen so far need the unit turned on for hours, if not a day, to fully stabilise.
  10. The standard for VLBI is Hydrogen Maser. GPS is then used to timestamp the data streams. Rubidium can be used below 1GHz as the errors due to ionosphere path delays are greater than any timing errors due to the Rubidium, and can also be used as a backup. Not sure about a GPS disciplined Rubidium oscillator. Hydrogen Maser drift: < 10 to the power -15 Hz per day Rubidium drift: 10 to the power -13 Hz per day [how can you superscript here?] And if your beam happens to encompass a pulsar you can use that...it will be a lot more accurate! Unfortunately our dishes won't be b
  11. It's a bit long but have a look at this YouTube video - GPS Disciplined Crystal Oscillator. The way GPS works is based on very accurate clocks so you can 'measure' the distance from yourself to a number of satellites. Trigonometry does the rest. To do this the GPS satellites transmit a very accurate timebase/clock. As a side effect the receiver (the one with you) can provide a very accurate 1 second 'tick', the rubidium or crystal (or even cesium) oscillator fills in between each tick. So the oscillator gets a very small correction every second removing thermal drift and aging errors.
  12. Coto - I think the H142-One receiver has a GPS device to stop any frequency drift from the internal local oscillator. i.e. when you looking at 1420MHz it really is 1420MHz your looking at and not drifted to 1420.10MHz once it's warmed up. The clock defines the sampling rate of the SDR. The 'disciplined' part of 'gps disciplined' removes long term drift effects of temperature etc on the local oscillator, while the local oscillator handles the short term stability. And the discipline part needs to done in a way that doesn't cause phase noise (i.e. correcting frequency in sharp jumps).
  13. I had a quick chat with David Lonard and he has used a GPS disciplined clock for 50MHz but didn't go very far, although did prove it can be done for an amateur. At 1420MHz the issues will be magnified. He's now concentrating on locally separated receivers (i.e. RF comes back to one point with one central clock). I'm not convinced the pure Intensity Interferometry (no clock synchronisation) is the way to go (ready and willing to be corrected on this), so solving the clock on a budget is the gateway to VLBI for amateurs. Interestingly he did point me towards XTRX Octopack which includes
  14. That might be my confusion. Been investigating a fair few different VLBI solutions over the last few days. The solution that David Lonard was looking at included a step whereby the feeds were synchronised (don't have the full details yet) in his python FX Correlator code prior to running FFTs in the GPU. This was with a system where both RF ends of the baseline were coming into a single dual channel LimeSDR. He also started looking at GPS Disciplined Clocks. See VLBI Oscillators. My assumption is that, even with a perfectly synchronised timebase, a separate Local Oscillator for
  15. Another item to note. No synchronisation of Local Oscillators required as long as you are direct sampling. I.e no LO required. So 10GHz might be difficult between sites if required. Time stamping of the IQ feeds needs thinking about. I say IQ because you want to time stamp before a non-real-time operating system gets involved. I have both the books I listed above. NOT light reading. Lol. David Wilmer’s YouTube videos are particularly good. One thing I do think is critical is the calibration of the gain of the system which needs to be carried periodically during a scan to
  16. Been wanting to expand my mind into Radio Astronomy and Astro Physics for a while. Attended a IET lecture recently that nudged me to do something about it. So what is required to build a radio telescope that can do a bit more than tell you that we have a sun, moon, Jupiter and a tantalising glimpse of possible spiral arms? i.e. How to get higher resolution on an amateur budget (£2k-£3k). Have started looking into what is required for Radio Interferometry. Scouring the internet has turned up quite a lot of info. However, some of the more interesting amateur works seem to have gone d
  17. Just found this thread having been reading up on 1420MHz Hydrogen line imaging (I'm a radio amateur and professional software developer). Great amount of info here...many thanks to everyone I have noticed that some people are adding Satellite boosters after the pre-amp? Normally the pre-amp should provide enough gain to overcome any feeder losses down to the receiver and also alleviate receiver sensitivity issues, so I'm not sure why they are required? Also the boosters seem to be 75ohm which means a mismatch and consequent signal loss unless there is some matching being implemented
  18. I also hit this until I realised that the 'shooting interval' is time is the period between each shutter 'opening'. Therefore it must be longer than the exposure otherwise you'll be opening the shutter again before its closed!
  19. Wow - An inspiration to all us budding imagers to just try it! In my case I'm a returning imager (from when hyper'ing B/W film was all the rage). This site is reavaluating what is possible. LukeSkywatcher's initial skepticism is the best praise possible Well Done
  20. They were there...I think on the lower floor demonstrating the spectrum of a light bulb. Grabbed some leaflets as they were busy. They also had an SBIG guy on the stand as well.
  21. Welcome from another Sussex member
  22. Thanks Steve Was planning on using the tube but given I was stuck in the Jubillee tunnel at Canary Wharf this morning for more than 90mins I was thinking a nice walk overground would be a pleasant change!
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