Guys,

I have a test version of a little web app that I'd like you guys to help me test.

Its an app which calculates the transit times (in UT) of the GRS (Great Red Spot on Jupiter. If this works out I have a whole pile of such ephemeris type scripts ready to deploy.

webtreatz.com/component/option,com_wrapper/Itemid,83/

Please don't share this address outside of these boards just yet as this is very much a beta test.

Thanks for any feedback.

Update - 21 June 08

I've added a Sunrise/Sunset/Twilight calculator;

webtreatz.com/component/option,com_wrapper/Itemid,84/

Hi Dave,
looks great !
One thing if possible, do the dates gave to refresh back to Jan1 2008 after you run it?
Why bother with the password thingy.
Would a button showing the next 7 days be useful? like the ISS passes in heavens above.
The only thing now is will the weather allow us to actually test it anytime soon.

Hi Dave,
looks great !
One thing if possible, do the dates gave to refresh back to Jan1 2008 after you run it?

Good point.

Why bother with the password thingy.

The calculations take up processing time on a hosted server, therfore I don't want messers clicking like mad for no good reason. Also to prevent robots from farming the data. Also helps limit 'denial of service' attacks.

Would a button showing the next 7 days be useful? like the ISS passes in heavens above.

Excellent idea.

The only thing now is will the weather allow us to actually test it anytime soon.

I'm actually pretty confident about the timings. It's all of the sort of useful suggestions you mentioned above which I really want to hear about

Dave G,

This is great! I've just used it. It's a nice handy calculator.

What about the second red spot and the more recently manifested small red spot? ( for fussy astronomers like me).

Thanks for sharing this useful tool.

Eamonn A
MPC J62
www.kingslandobservatory.com

What about the second red spot and the more recently manifested small red spot? ( for fussy astronomers like me).

See I knew this place is awash with great ideas. Very little change is needed to predict times for other features.

Nice work Dave.
I think the suggestions above are very good and I can't add much more than that at this time. I just cross-checked it with todays times from the S&T page and it's looks pretty accurate.
www.skyandtelescope.com/observing/object...piters_Red_Spot.html
However, your calculator allows a month's worth of calculations, which is very handy.
Thanks for sharing it here.

Good going Dave, it does work. I hope the times it gives are correct!

See I knew this place is awash with great ideas.

Then how about a picture representation?


Kidding!

Also, I am sure you can add a line of code to read the date on one's own computer everytime that applet loads, therefore defaulting to that person's date. A handy technique to just simply going to your applet on the web, and if already defaulted to that date (for both date options given), simply click 'Calculate', and voilá - you have that days/nights time(s).



Seanie.

Here is another idea,
How about io/europa/ganymede/callisto transit times along with shadow transit times, now that would make it even more useful.

Hi Dave,

I've tested it in Firefox 3 and it worked fine.

I found the passwords a bit difficult to read tho' (maybe I need my glasses changed).

Michael.

I found the passwords a bit difficult to read tho' (maybe I need my glasses changed).

Good, its not just me who thought that! Or perhaps I'll see you in specsavers!

Looks good DG, any plans to share the code or even the algorithms used? I'd be pretty interested in seeing whats involved in the calculation.

Cheers,
~Al

Cool, I can find out if I'll ever be able to see the red spot through the 5 minute gap in the trees next door.

Now I just need a calculator to find out what times Jupiter is in the gap every night and then compare results to find a match :wink:

On a serious note, is this calc not a bit moot for the next 2 or 3 years for us here though. Will we be able to see/image the GRS with 15-20 deg altitude seeing anyway or will this calc come into its own in about 2011 for us.

While you are at it Dave, can you write one for transits of the ISS across the disc of the Moon and Sun as visible from Ireland? Should be a *simple* task for someone like yourself.
:wink:

While you are at it Dave, can you write one for transits of the ISS across the disc of the Moon and Sun as visible from Ireland? Should be a *simple* task for someone like yourself.
:wink:

Would you beleive I'm on that one. I've already written code to calculate a satellites XYZ vectors as per NORADs SGP4 algorithm. I've done the bit to transform these into alt/az co-ordinates for the ground viewer. Where I'm at now is finding an effecient way to calculate actual pass timings. This involves a lot of calculus and I was never brill at calculus. I've also been playing with Ed Moran's java ISS transit code and made some interesting mods. I removed much of the restrictions such as 160km radius and 11 day limit. The problem I see with turning all this into a web app is it involves a huge amount of processing. That's why Ed Morana (I think) used a client side java applet, to push the processing burden to the users PC.

Looks good DG, any plans to share the code or even the algorithms used? I'd be pretty interested in seeing whats involved in the calculation.

Albert, the algorithm used is described in the book 'Astronomical Algorithms' by Jean Meeus (Willmann-bell ISBN 0-943396-35-2). The algorithm used here is described on pp 277-283. For anyone interested in such calculations this is 'The Bible'. As for the source code, it is so highly custom it would be pretty meaningless in many ways. When I'm done with all this I might be able to publish the PHP class module which is in effect the heart of the calculations. The problem is unless you know what your looking at even that would be hard to use.

A better approach might be to compile all my work into a dll class which could be used in your favourite spreadsheet or other app.

Hi Dave,
I found the passwords a bit difficult to read tho' (maybe I need my glasses changed).

Me too, however lookin g at that again may have to wait. I found that you never have to click the word refresh button more than once or twice max to get one thats easy to read. My intention is that thiese types of app are used not that frequently, so maybe this isn't such a bad thing.

Here is another idea,
How about io/europa/ganymede/callisto transit times along with shadow transit times, now that would make it even more useful.

Another one in progress. This is obviously a completely different app to the GRS transit calculation. Nonetheless, I have written code to calculate the co-ordinates of the 4 moons. Its on my list to put this into a format to provide event timings.

Also, I am sure you can add a line of code to read the date on one's own computer everytime that applet loads

Excellent idea and I can make it so the 'to' date is 7 days ahead thus including Dave Lillis's idea in one swoop.

Albert, the algorithm used is described in the book 'Astronomical Algorithms' by Jean Meeus (Willmann-bell ISBN 0-943396-35-2).

Ah... I've been looking for a copy of that for years (at a reasonable price!) but never managed to pick it up. I've read some software modules/classes based on the book but its hard to understand the reasoning behing the calculations without the book.

I do have Practical Astronomy with your Calculator which is good, but does a very poor job of explaining how the algorithms work too!

Ah... I've been looking for a copy of that for years

My copy is one of my most valued books and as such I protect it with dear life. You would be welcome to borrow it at some point in the future but at the moment you couldn't find a crow bar big enough to prise it away from me

Very nice Dave,

Very useful

Hi Mate,

That is a great programme well done

Guys,

I've now added a Sunrise/Sunset/Twilight calculator here;

webtreatz.com/component/option,com_wrapper/Itemid,84/

Once again feedback would be appreciated.

This time I made some changes;
The page state is preserved between submissions;
The default start date is today's date and the default end date is today + 7 days;
Please tell me if the captcha without the background is more readable;

Thanks for helping me test this.

PS: Before you mention it, the determination of your location is based upon your IP address and so is very hit and miss. It should get your country right and I'd be interested to hear how good it is at guessing your city too please

Hi Dave,

The text is much easier to read. It is guessing my location correctly but I'll try the 3G connection later and see if it works.

Michael.

I'll try the 3G connection later and see if it works.

That will be interesting. I would expect the location it gives will be the location of the base station of your service provider.

Its much easier to read, although it thinks I'm in Dublin.