Telescope magnitudes

[glactus]

Meade 16 inch telescope

Here's a magnitude formula for telescopes (under excellent and dark skies.)

With a 4 inch telescope, some people have been able to see Pluto. 4+5log(100)=14

With an 8 inch telescope, it is possible to get this result:
4+5log(200)=15.5 magnitude. Under dark skies, you may be able to see up to 15.5 visually.

With a 16 inch telescope.
4+5log(400)=17

With a 36 inch telescope.
4+5log(900)=18.77 or 18.8

Different models give different results, as do different locations.

For instance, telescopes close to the equator give clearer vision on dark nights. This is because dust particles in the atmosphere work their way to the poles like drift wood in a fast moving stream work their way to the edges.

So you would thing that this theory would make viewing in the South Island of New Zealand almost impossible as here at this latitude all the dust particles accumulate, but ah!! that is not so.

As a matter of fact, because of this high atmospheric dust,
violent thunder storms accumulate in this area, cleansing the skies so finely that the night sky becomes crystal clear, enabling a cluster of stars beside the Southern Cross to shine like jewels, a sight to behold, and named - "The Jewel Box"


The Sombrero galaxy

[starrdawg]

Hes not talking about "visual telescopes".

I cant help you on the X-ray version Iron, but radio telescopes operated by "amateurs" on the ground are typically 24 foot diameter or larger depending on the local zoning laws.

That size limit came from the "old days" of C/Ku band satellite TV.

I used an old C-Band dish with a changed LNB rotary feedhorn for a few years until neighbours complained to the town council about the "ugly thing" in my backyard and had to take it down.

Just as well, as I couldnt afford the necessary very expensive scanning receivers to do a decent job anyway.

[Andy Mac]

Dec 2, 2010 11:19:25 GMT glactus said:

Here's a magnitude formula for telescopes (under excellent and dark skies.)

Appreciate the info but what is an 'excellent and dark sky'?

[starrdawg]

Thats something both of us can only dream about, Andy.

"dark...excellent" can ONLY be found in the high deserts of New Mexico, and Arizona in the US. Us "urban" dwellers dont have any hope of ever seeing a sky like that.

[glactus]

No Matter where we live, it seems that there are evenings when viewing the heavens is impossible, so we have to make the most of it I guess.

Here in Queensland we have cloudless weather for months, but the heat haze can be present till well after midnight, so you can see that even when there's no clouds to be seen, conditions may not be perfect for us Astronomers.


The Black Eye galaxy

[starrdawg]

Andy and I have similar problems called sky pollution that has nothing to do with weather.

Urban expansions with their ever-present sodium-iodine floodlights have made the sky unusable at any time.

[glactus]

Starrdawg. You mentioned that you made a radio telescope in your back yard. Would you like to tell us more about it. sounds interesting.


The reflection nebula

[starrdawg]

C/Ku band satellite TV was relatively popular here for about 10 years until the new 1 meter dish's were introduced. All satellite TV systems here now use the small dish which operates at much higher frequencies (2 Ghz+) making the old style systems obsolete.

You could pickup a used C-band dish (24 foot) as "scrap metal" from most people. Or simply offer to take it down for them, and they would give it to you.

Those dish assemblies were called "button hook" antennas as the feedhorn was attached to the focal point by a pipe/tube that looked like a button hook.

The feedhorn, LNB, and down converter module had to be replaced as the bands used for radio astronomy are totally different than TV. I used modules from Scientific Atlanta for that purpose.

The scanning receiver was from Watkins-Johnson, and the computer tracking software was a modified version of the HRD software package.

Only had it up for 3 months before the city threatened to fine me for the "ugly device" in the back yard. So I took it down and sold off the parts. Oh well.

Building something like that from "scratch" would cost many $$$, but you can find most of the parts on Ebay at reasonable prices.

[glactus]

Good one. At least you had a go Eh! and some satisfaction too.


M 106

[Andy Mac]

Dec 5, 2010 12:19:28 GMT starrdawg said:

Only had it up for 3 months before the city threatened to fine me for the "ugly device" in the back yard.

You've only got yourself to blame RJ - I told you at the time that you should have painted it pink!! ;D ;D

I think you should tell your local council just how lucky they are. Here in Oxford, one of the minor 'personalities' - a chap called Bill Heine (who is well known for this endless battles with our local council) had this shark stuck into the roof of his house (which is only around a five minute walk from mine). Needless to say, the council objected & as Heine refused to take it down, there started a long & protracted legal battle which must have lasted for well over a decade. The shark is still there BTW & has certainly helped in terms of attracting tourists (and therefore business) to Oxford.

Attachments:

[starrdawg]

Pink would have made it worse Andy. It was painted "camo", but like you there is always some "nutter" in the neighbourhood who would complain about anything including sharks in the roof.

C/Ku band TV antennas used to be fairly common in the early days of satellite TV (1970's) in N. America, but were expensive, needed lots of real estate to swing the dish, and hard to maintain.

Everything now is those little 1 meter dish systems, that are dirt cheap, and have hundreds of HD/3D channels on them.

Now if we could just get rid of the old "farts" that run the council....

[glactus]

He would probably be able to have his shark here as the council has set a precedent and has it's own bullock and pineapple.

You would get away with your big dish too, Starrdawg.

The Bullock is outside the city of Rockhampton which is a beef producing area, and the Pineapple is the logo for a tourist complex called "The big pineapple".






The Crab

[starrdawg]

I see those items are great for tourism, whereas my "dish" only attracted nasty comments from neighbours.

The same person responsible for his "mean mindedness" in the council, is now under investigation for fraud, so I guess in a way I get "even".

There is a roadside diner out in California that has a full size Super-Connie aircraft suspended above its building to draw in customers. Seems to work, and the place has actually been in several movies over the years.

Makes me wonder what they would charge me for a now retired Shuttle.

[glactus]

Starrdawg, I have moved my reply to off topic.
(Road signs)


Starburst galaxy