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My Radio Telescope Project


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Good stuff, successful test. You should be able to get a reading from the moon with this setup but it will be very weak compared to the sun. The good or bad news is the winter weather will lower the noise levels. Better for the electronics but not for us?

Great to see some RA being done and old dishes being rescued?

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8 hours ago, Carl Reade said:

Good stuff, successful test. You should be able to get a reading from the moon with this setup but it will be very weak compared to the sun. The good or bad news is the winter weather will lower the noise levels. Better for the electronics but not for us?

Great to see some RA being done and old dishes being rescued?

Hi Carl, thanks for your encouragement.

I can probably do the Moon, because it casts a shadow. But really I'd like to do galactic stuff like Cygnus A. I just have no idea how to align it.

Steve

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5 hours ago, SteveBz said:

Hi Carl, thanks for your encouragement.

I can probably do the Moon, because it casts a shadow. But really I'd like to do galactic stuff like Cygnus A. I just have no idea how to align it.

Steve

Good stuff, successful test. You should be able to get a reading from the moon with this setup but it will be very weak compared to the sun. The good or bad news is the winter weather will lower the noise levels. Better for the electronics but not for us?

Great to see some RA being done and old dishes being rescued?

Hi the dish would have to be used in Ra and declination mode. This is more diy and depending on its mount should be straight forward to do. You would need to mark your Ra degrees around the mount like a compass. Then if you purchase a a declinometer of eBay i think they are branded eagle £4.99 it will give you very accurate readings and it's magnetic. So as you raise the dish the pointer will give you the angle reading.

There are programme out there that will convert equatorial co ords to alt az for your location. So in theory you should be able to use the program to calculate where the object is a few hours ahead and set the dish to them and get a drift scan.

Radio eyes is also a good tool for this but don't think it's free.

Hopefully makes some sense

Carl

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Yep drift scan is a good way to go.

http://www.threehillsobservatory.co.uk/astro/radio_astronomy/radio_astronomy_1.htm

To align on the night sky I clipped a  finder scope to the edge of the dish and aligned that  using the maximum radio signal signal from the sun.  (Picking up the signal  from the new moon during the day for example is good fun - the moon is just as bright in the radio sky even when it is not illuminated)

I did not have any luck picking up any other sources with my small dish though. The signal is very small from these objects at the high frequency being used with satellite TV and the system stability was not good enough be sure that anything real was being picked up.

A Yagi aerial and TV tuner at 600MHz looks like a potentially interesting alternative low cost approach though eg

http://www.backyardastronomy.net/radio_telescope.html

Cheers

Robin

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4 hours ago, SteveBz said:

I'm going to try drilling a Dovetail bar today and throwing the dish onto an EQ5 mount.

Hi Guys,

Well here's the result.  Untested, but looks great.  It just needs motors and/or a goto upgrade kit.  Luckily the dish has a rusty old holding mount at the back.  It is even rusted through in parts, but the dish itself is aluminium and is in good condition.  There are four standard size dovetail bar bolts at the rear and I measured diagonally across two of them a 6mm drill (with a three mm pilot) took out the hole perfectly and the dish mounted first time. 

It is amazingly heavy and I needed an extra counter-weight on the back.  Balancing was easy enough.  So my thought is even with some rough polar alignment (eg a compass and spirit level) I should be able to get the Sun and Moon easily enough and I guess night-time objects will work too.

I probably won't get a chance to test this for a week or two, but I'll post results when I have them.

Here are the photos.  Oh, and I should say, it cost me nothing except a small scratch on the CG-5 when unloading the dish. 

Have fun,

Steve.

Whole dish at 3/4 angle.

2016-09-14 11.27.04.jpg

Mount and tripod from rear

2016-09-14 11.27.29.jpg

 

Weights - it was very heavy and needed much more counterbalancing than the C8.

2016-09-14 11.27.40.jpg

Dovetail bar mounted diagonally across back

2016-09-14 11.28.24.jpg

 

2016-09-14 11.27.54.jpg

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11 hours ago, SteveBz said:

I'd like to see what your connector cable looks like.  How does it all come together?

Regards

Steve.

Hi Steve,

Do you mean the connectors that came in the box?

Your set up is really looking good, you'll have to let us know how it works when you get to test it out.

Jon.

 

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1 hour ago, Asur1984 said:

you'll have to let us know how it works when you get to test it out.

It'll be next week, because there is so much on at the moment, but I'm going to try to do multiple passes, as if I'm stacking the images.

I've just scanned the major radio sources that I am familiar with on my phone app (I use "Star Chart").  I know I can easily see Cassiopeia and Cygnus, but the status of the others seems to be:

  • taurus A - below horizon
  • sagitarius A - a - visible but probably too low in the sky
  • Centauri A - below horizon
  • Orion Nebula - below horizon
  • Omega Nebula - visible but probably too low in the sky

So it seems that I'm left with trying:

  • cassiopeia A - easily visible at the moment from the early evening
  • cygnus A - easily visible at the moment from the early evening.

Have I got that right?

Are there any radio sources available during the day, do you think?  These might be easier.

I'd like to polar align the mount properly, but I don't think I can with the dish on it, so I'd have to align it after dark and then mount the disk.  I think this is too hard, so I'll try manual alignment with a compass and level.

I hope the low accuracy of the beam will mitigate the less than perfect alignment.

What mounts do you have available for your dish?  I think an eq3 would hold it, but I'm not sure how you'd align it.  Sky dishes are offset from the perpendicular (119 degrees is popping into my head) , so maybe you could manually correct it by adjusting your dec position by 29 degrees or something.

Regards,

Steve.

Just adding some coordinates for the record:

Orion (M42 - Orion Nebula):α= 5h 35m 17s, δ= +4°36'32"

Taurus A (M1 - Crab Nebula): α = 5h 34m 32s,δ= +22°00'52"

Virgo A (M87): α= 12h 30m 49.4s, δ= +12°23'28"

Sagittarius A (): α= 17h 45m, δ= -29

(M17 - Omega Nebula): α= 18h 20m 26s, δ= –16°10'36"

Cygnus A (): α=19h 59m 33s,δ = +40°43'41"

Cassiopeia A (): α= 23h 23m 24s, δ= +58°48'54"

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7 hours ago, Carl Reade said:

Hi I would concentrate on Cass A first and see if it can be detected with you current setup. Another interesting experiment would be to set it so the Milkyway goes through a 24 hour drift scan to see what you get. Liking the mount by the way?

Hmm...  Why do you suggest Cass.  I was thinking Cygnus, because I think it's a available during the day (after all its already overhead early evening). That way I could align to the afternoon sun and then go to Cygnus A.

Maybe I could do the same with Cassiopeia but it's lower in the sky. Which gives the stronger signal?

Regards

Steve.

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8 hours ago, Carl Reade said:

Hi I would concentrate on Cass A first and see if it can be detected with you current setup. Another interesting experiment would be to set it so the Milkyway goes through a 24 hour drift scan to see what you get. Liking the mount by the way?

Ok.  Just looked it up. Cass has twice the signal flux.

Maybe I'll try both.

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8 minutes ago, robin_astro said:

What wavelength are you looking at? Flux is very wavelength dependent. Cas A flux drops off fast with increasing frequency so Tau A flux (Crab Nebula) for example is similar to Cas A at 11GHz but  1/5 as bright at 600MHz

A common reference paper is 

http://adsabs.harvard.edu/abs/1977A%26A....61...99B

(table 2)

Cheers

Robin

I haven't filtered it yet, I'm just using total flux, but as my dish is 1.3 m across (spherical not parabolic) and maybe about the same radius, it's that sort of wavelength.  I imagine it's in the low GHz range (eg 1-5).

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16 hours ago, robin_astro said:

The LNB will have already filtered out most of the wavelengths. A typical Ku Band sat TV LNB will be designed to just pass ~10-13GHz

Robin

Hi Robin,

Well the lnb label had faded away. Here are some photos of it in case anyone recognises it:

tmp_10774-20160917_091529537705526.jpgtmp_10774-20160917_091540-966498657.jpg

Thanks

Steve.

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I think it is most likely to be Ku band which is the normal band for sat TV in the UK these days.  The alternative would be C band at 4GHz (which was mainly popular in the US and generally used large dishes a couple of m or more across, known as BUDs or "Big Ugly Dishes")

Provided you are already  reliably "seeing" the moon, you could try for Tau A, high in the morning  sky currently.  The drift scan of the sun or moon will give you your beam width (probably ~2 deg) giving you an idea how accurate your aim needs to be. 

Cheers

Robin

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20 minutes ago, robin_astro said:

I think it is most likely to be Ku band which is the normal band for sat TV in the UK these days.  The alternative would be C band at 4GHz (which was mainly popular in the US and generally used large dishes a couple of m or more across, known as BUDs or "Big Ugly Dishes")

Provided you are already  reliably "seeing" the moon, you could try for Tau A, high in the morning  sky currently.  The drift scan of the sun or moon will give you your beam width (probably ~2 deg) giving you an idea how accurate your aim needs to be. 

Cheers

Robin

 Great I'll try Wed or Thurs and post back.

Steve.

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4 hours ago, robin_astro said:

I think it is most likely to be Ku band which is the normal band for sat TV in the UK these days.  The alternative would be C band at 4GHz (which was mainly popular in the US and generally used large dishes a couple of m or more across, known as BUDs or "Big Ugly Dishes")

Provided you are already  reliably "seeing" the moon, you could try for Tau A, high in the morning  sky currently.  The drift scan of the sun or moon will give you your beam width (probably ~2 deg) giving you an idea how accurate your aim needs to be. 

Cheers

Robin

Hi Robin,

I haven't tried the Moon yet.  In fact until it was mentioned here I didn't even know it produced a radio signal. 

We have a lot of trees in our garden, so the Moon isn't always visible except when it's very high.  At the moment it's just behind the tops of the trees.  Earlier in the year it was in full view.

I might polar align the mount at night, throw a tarpaulin over it, and then test the setup with the Sun the next day.  That will give me the beam width, and then I can try some of the other Radio objects.

Regards

Steve.

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