SteveBz

So my SDR was indeed shorted. The new one seems to work in that the LNA light comes on. Good news. However, my signal is amazingly noisy. I have no idea why. There is no signal whatsoever, even though I'm apparently in the middle of Cygnus: If I ramp up the Median Smoothing I still get nothing. I can't believe the antenna doesn't work, it's so simple! Noisy cable, maybe? I'll just replace it and see. Kind regards Steve.

Hi Zi Hao, So impressive. I love the ultra light dish. Did you make it yourself or buy it? The waveguide is also very nice. I like how you've mounted it with the collar. I might try the same idea. You have the same NooELec H1 as me, so I'm pleased to see that it works. You're definitely ahead of me. The fact that the LNA comes out at a right-angle could put extra torque on the port. I've put an elbow on mine to avoid that. I also seem to have short circuited my rtl-sdr. There is no dc voltage on it at all, even after I switch it on🙄, which I didn't realise you had to do. I've ordered a second one. I just added a baby antenna direct to the sdr without an LNA - for testing the software. Bad idea. Can I ask you, have I understood that right? Did you need to active the bias tee? No one else has mentioned this at all. Good luck. Steve.

Hi Zi Hao, I forgot to ask, rereading your post, did you manage to get any results from this or have you not deployed it yet? I'd love to see your build and setup including software. Kind regards Steve.

So here's the dish all plumbed in and ready to go: And here's the first connection. It seems to be the same as with no aerial, so I think maybe there is a broken connection. I'll try a continuity test. But as it's dark, I'll just cover up the LNA and do it at the weekend. I might even buy a shorter cable as this is old and 25 m long. Maybe a new 2 m cable would be better. It goes: Dipole=>LNA(NooELec H1)===========25 m cable===============>RTL.SDR=>Powered USB hub=>RPi with H-line-software. Regards, Steve

For me the performance is slowed down by uploading the whole sample file from the Pi to my pc. If it just returned the answer requested (Eg the max S/N ratio) that would be much quicker over the network. Or indeed the integral. I might play with it and let you know. Tx Steve.

That's perfect. If I run python3 H-line.py - t on my RPi, then I can run a query from my pc every 5 minutes or so and plot the result. I don't really think it needs a rewrite, it's quite clear, but I'll happily chat about improvements if you like. Kind regards, Steve.

And here's the finished product. I guess I'll need to dismantle it to get it through the door 🙂. Then it needs a bit of a tidy-up. The next question is software. I've managed to get @Coto's Virgo software running on my PC, but not on the RPi3b+. I don't want to damage my current setup, so I have a 128GB SD card on order from China to see if I can get it working with a fresh install. The other option is @Victor Boesen H-line-software, which I got running on the RPi3b+. In both cases I'm not quite sure how to turn the sampled output into an integrated signal (ie the total flux in 1420 +/- 50 MHz), for each sample. I'd like to get a skymap of the 21cm line intensity in the way both the above authors have on their respective pages.

Hi Lucas, How did you set up the radio? I'm just waiting for parts at the moment and I'd love to see how other people are doing it. Steve.

I can't remember where I found this paper, but it covers all the calculations very nicely and compares antennae. Scroll to section 7.5. Steve. Hydrogen_1.pdf

And here is the finished feedhorn/cantenna: Monopole connected to port. Monopole/port mounted 9.3 cm from base. Final product with NooElec SAWbird H1 Premier LNA and RTL.SDR. Now comes the challenge of mounting it at the focal point. S.

Hi Zi Hao, I hope you're well. Thanks for your input. Yes, that's about what I calculated/found. 28 cm overall length, 9.3 cm distance from monopole to back, 15cm diameter, 4.9 cm length of monopole. Nealy finished. I'll post a photo of the antenna when it's done. Kind regards, Steve.

Hi People, What does a focus star look like? I have a Newtonian F/5 200mm/1000mm plus a Canon DSLR and I'm trying to autofocus. I'm thinking 15 secs on a Mag 6 star at ISO 1600 is good and then an HFR calculation what do you think? Up until now I've been maually selecting the star in advance, but sometimes I forget to check the Dec, or RA and for large constellations these can be below the horizon (this is usually sub-optimal 🙂). So I'm thinking a little SQL and selecting DEC of DSO target +/- 10 degrees and RA of DSO target +/- .5 hrs and Mag 5.5-6.5 for the focus star. I then loop round, adjusting the fine focus programmatically until the HFR is a minimim. Will this work? Kind regards Steve

Hi People, I've decided to start work on refurbishing my profile photo. This is quite a long and arduous voyage as obviously I have to start with the rust. I've decided to drop the EQ5, as it's not really strong enough and revert to the original motorised mount with it's RA motor rotated by 90 degrees. Ie the Earth is the RA motor and the RA motor is the Dec motor (RA is the new DEC, I could say). I spent most of this week with the wire brush attachement to my drill cleaning up, coating with Hammerite rust treatment, undercoating and finish coating the mount while waiting for parts from Amazon US and UK, AliExpress, Ebay to arrive. In particular: 150 mm x 500 mm aluminised pipe + separate 150 mm end cap RTL.SDR software radio dongle SAWbird + H1 LNA SMA Connector and various others. The dish is 130 cm diameter with a 47 cm focal length, making it f/2.8 if that means anything here. 😀 Here are some photos: Adjusted, painted, motorised mount. Hammerite rust treamement and some undercoat. Fully undercoated support plate (it's VERY rusty) Topcoat, also Hammerite. Cantenna, cut down to 28 cm with angle grinder and then sharp edge ground down with emery disk. Cantenna with end cap. Cantenna undercoat. Cantenna topcoat. There are a number of measurements which it is hard to get right. The length of the 'can' is variously given as anything from 14cm to 38 cm (including the choke). The correct answer seems to be 28 cm. It's calculated as 'at least' 3/4 of the wavelength in the waveguide. Apparently the wavelength in the waveguide is not 21.1 cm, but more like 37 cm after other interactions are included. 28 cm seems to be the right answer. I'm waiting for the topcoat to dry before assembling the dish and mount for the next exciting installment. Any warning, advice, observations or encouragement happily received. Kind regards Steve.

OK, very nice. On Google there were very many different callibrations of Uranus and I wasn't sure which were right. But the response is very off, I agree. I'll look again if we get another clear night this side of the summer 😅 Kind regards Steve.

Is this anywhere near the right calibration and response correction (not divided by 29 Ari)?

OK, great. I can just use the dispersion from my last star and then do a 1 line calibration on the main star. Then in the meantime I'll just use old files to do the response correction approximately. Then I'll try to use either a corrected 29 Ari, if I can, or a library star to do the division. (PS I didn't realise that the colour of Uranus would be so beautiful - mesmerising - might try to get a longer and more in focus photo too) Kind regards Steve.

Hello People, Well I took up Robin's challenge. Very low in the sky. The shed roof cut off half the image!! But just to show you it was the right object here's a quick snap in all her glory: The greeny blue was quite unexpected! My 29 Ari was a bit over exposed, so I may need to play with that a bit, but in the meantime here's the Uranus spectrum with some old biases and darks (I may refresh them if I need to) and stacked in Siril then cropped and spectrum from Bass. No response file applied. My first question is, I don't even know where the H-Beta line is, if there is one. Have I got it right? What to do next? I'll work on the 29 Ari file in the meantime, but could I not use a standard library spectrum? Thanks Steve.

Hi Robin, I was so excited by your suggestion. I thought it would be really interesting and quite challenging, however, I've just checked its location and I see it's almost bang on the ecliptic. Sadly I don't think I can get that low. I normally work on about 35-30 degrees Declination in the South. But I guess this must vary by time of year. Wednesday is looking good, I'll take a photo as low as I can and platesolve to see how low it is. Kind regards, Steve.

Hi Gents, I had so many hiatuses with getting this Bresser 114/500 to piggy-back my mount. I'm back now to where I was 6 months ago! Anyhow it seems to be working. Bresser f/4.4 mounted on my main scope on an EQ6 with a QHY5iii178mm and SA100. It worked well last night, so here it is (63 And - B9v) 50 exposures stacked in Siril with darks and flats corrected and calibrated in Bass with an old response file from before. Everything's changed but it seems to work. Obviously I need to update the response file. (NB Just updated with darks and biases. Much smoother response) Does anyone have some nice ideas for spectroscopy in the current season, assume we get any more clear nights? Kind regards Steve.

Hi Ken, Yeah, I thought it was nicely dated😁 So the other option might be a focal Reducer, but I don't want to introduce chromatic aberration into the optical stream. Would that work (maybe to replace one of the spacers I have now between the SA and the sensor). What would you recommend? Have a good day. Kind regards Steve.

Hi Ken, I just bought an etx 90 as a piggy back for my sa100, but focal length is 1250 mm and that really lowers the resolution. My cheap bresser 114/500 is much crisper. That said I imagined a 76/300 would be even better. What do you think? Kind regards Steve.

So now we have a minimum viable product, here: WhatsApp Video 2021-09-12 at 16.15.41.mp4 There's a slight bounce on the close function, which I'm working on, but basically it more-or-less works. Here is the unit. Does anyone recognise it. I'm trying to find the user manual to set the stop limits properly. Now to think about a few bit to add to stop it flying off in a storm. 😅 Kind regards Steve.

Nice. I'll look into that. Actually, I'm quite pleased with the results and the setup. I don't really want to go more complex at this stage. I automated the slide-off roof on my shed at the weekend with an old garage door opener I found on ebay, which makes things a lot easier. As I mentioned before the reason I'm doing all this is that I'm also doing a project on binary stars with a colleague. Theory is great, but actually looking at stars really helps to keep it real. Even just chatting here with you about Zeta Lyrae brings clarity to the issue. I saw the description 'binary star' on Zet01 Lyr, but not Zet02Lyr and I thought oh, they missed one, but your clarification about the 4.3 days and the spectral binary really helped shed light on the situation for me. So it's all very well being theoretical, but looking at it in real life really brings a new dimension to ones understanding. Kind regards Steve.

So it's a hierarchical system. 6 Lyr is the brighter one and it has a close invisible companion only detectable because of it's variable effect on the spectrum. 7 Lyr is fainter and may be a wide companion for 6 Lyr. So the nice strong spectrum I have is for the brighter star (ie 6 Lyr), but I don't have the resolution to show the detail you showed earlier. Do you think I could improve the spectrum I got, or is that pretty much as good as it gets with the SA? I was pretty sure you had some better resolved ones. Kind regards Steve.

Actually, that's a fantastic resource. I shall look into it more.