Hale Telescope Addon v3 officially available

Victory is declared!

V3 of the Hale Telescope Addon is now available at

http://www.lepp.cornell.edu/~seb/celestia/files/hale_telescope_v3.zip
(19MB, expands to 88MB)

See also
http://www.lepp.cornell.edu/~seb/celestia/hale_telescope.html


Have fun!

almost ready to "declare victory"

I haven't been able to spend much time on the Hale Telescope project in recent months. Although there are many more things I could implement, I think that only a couple of them will actually be added before I release it for use with Celestia. As in previous years, I intend to make it available just before Christmas.

In the meantime, I've assembled another "alpha" release for anyone who'd like to try it. The Zip file is 18MB. It expands to 87MB when installed.

Please let me know if you'd like to give it a try.

crane cable drums

Yeah, it's been a while. I've been distracted by other things.

A while ago, I received a picture of the backside of the overhead crane. Examination revealed that I'd left out some rather important components. I've enhanced the model to include its cable drums.

Double Spec

I've been struggling with a low-poly model of the double spectrograph. I can't quite get its proportions right. But here is what it looks like for now.

Triple-Spec

I've started making some low-poly models of some more of the instrumentation. They're not very exciting, but lend a little variation in color and shape...

Here's a view showing the Hale version of the Triple-Spectrometer mounted at the Cassegrain focus as well as on its stand in a storage room. Of course, it wouldn't actually be in both places at the same time. I just haven't written the exclusionary code yet.

For more information about the Triple-Spec, see http://www.astro.virginia.edu/research/instrumentation/triplespec.php

Minor updates

I've only been making minor updates recently to the Hale Telescope addon, being distracted by other stuff. Pictures soon.

Fireworks!

In honor of the day, I've created some animated fireworks for use with Celestia. They're based on highly modified versions of the ScriptedOrbit routines used by the Hale Telescope Addon.


fireworks_v1.zip (236KB)



This shows them going off over crude models of the Washington Monument and Lincoln Memorial.

Flying Carpet available

The flying carpet addon is now avaiable.
I didn't bother to try to keep the carpet level,
so it just moves in straight lines.

I did make the buttons bigger, though.


http://www.lepp.cornell.edu/~seb/celestia/files/flying_carpet_v1.zip (150KB)

Here it is at the entrance to the Hampton Court Maze, which is included in the Addon.

Flying Carpet

It's clear to me that the Hale Telescope Addon won't be ready for some months more since there are so many details that aren't right yet :(

So I've diverted some effort into a project that uses some of the Telescope's Lua control functions. I hope it'll be ready this coming weekend, even though it's only 90% finished ;)

It's a flying carpet.



Here it is hovering over the southern section of the Hale Observatory's property.

I could probably make it available as-is, but there are a few things I'd like to improve.

1. Reorient carpet and its motion relative to local down. This is relatively difficult. Currently the carpet stays oriented with respect to its initial position.

2. Provide some other local surface to navigate -- maybe a maze?

3. Reorient up/down buttons to point up/down

4. Use a picture of a Persian Carpet.

out of order

elevator no work

odd and ends

I added several "easy" things today:

• rotate dome manually
  
• raise and lower windscreen manually(but not really: it either tracks automatically or is down. I haven't figured out a way to track the telescope in azimuth easily.)
  
• raise and lower central lift (seen below)
  

I've been frustrating about the two conventional elevators: one is for freight and one is for people. Implementing the buttons and controls for the elevator algorithm would be a pain. Maybe I'll just chicken out and hang "out of order" signs on them.

Equipment entrance & freight elevator

I've spent some time making the overhead door work. It included cutting a hole in the model of the base, making a separate model of the door, and implementing open/close buttons outside the entrance.

Here it is with the door partially open. You can see the freight elevator shaft in the background. The elevator is only partially implemented. Its up/down buttons haven't been created yet, nor have the doors to the shaft with their buttons.

Sidereal Clock

Wanting to feel I'd actually accomplished something, I decided to make a very tiny piece of the telescope Addon available.

siderealclock.zip
(34KB, expands to ~100KB)

It displays the current sidereal time at its location within Celestia. Sidereal time is defined to be the hour angle of the vernal equinox. Operationally, that means it's the Right Ascension of an object that's precisely overhead.

Alpha test?

I think this project is about 90% completed, but you know what they say: the last 10% takes 90% of the time ;)

There are lots more things to do, but all of the major functions have been implemented.

If anyone is interested in giving it a try, please make a comment here. I can make it available for anonymous download, so you don't have to provide an e'mail address if you want to preserve your anonymity.

Size:
o Addon Zip file: 16.5 MB, expands to 74MB on disk (cmod model files aren't very compact); Celestia + telescope with control desks is about 250MB when fully loaded into RAM.

Performance:
o 15-20fps on a 3.4GHz P4-550 + Nvidia 7800GTX

I'd be interested in knowing what kind of performance is seen on other systems. I fear it may be unacceptably slow on many configurations. :(

Minor bugs

Not much to report for the long weekend: I only fixed a few minor bugs which don't have much effect on what's visible. E.g. the transfer of manual orientation commands to the telescope wasn't working right. I'd left out an if statement.

coude flat frustrations

The central Coude flat supposedly can be controlled manually. Presumably this is necessary when using the telescopt in the 5-mirror coude configuration so that the central flat reflects light to the mirror in the Coude arch. Its angle has to change as the target changes in declination.

Unfortunately, I don't see any controls on either control desk which can actually change that angle. I started to implement one of my own (using a little artistic license :) ). I even got so far as to create an indicator dial with fiducial marks. I then realized that to do it with enough precision would require 3 (or 6) dials, just like the controls for the telescope itself. I then gave up on that idea. For now I expect to only implement the "automatic" mode and let the mirror change its own angle. (or not).

What else? Oh, yeah, I added some details to the description of the Easter Egg. That text is all encoded rot-13, so its easily decoded, but not readable at first glance.

I also started implementing the code for the RA Rate meter. It shows how fast the telescope is moving in RA in seconds of RA per hour. The guage has a selectable maximum value of 300 or 3000 sec/hour, so it obviously can't show the absolute speed, which would be about 3600 sec/hour. I'll assume it's supposed to show the difference from that.

Easter Eggs

I spent some of the weekend implementing an Easter Egg: an undocumented feature that you have to hunt for. It's not much of a puzzle, but it's something people have asked about several times on the Celestia Forum. I have an idea for another one, although that one is more of a rotten egg than a painted one ;)

balance meter

I've done about half of the work to add the balance meter and associated selection switch. Still to do are to illuminate the balance lights, label the meter and make the switch and meter move.

moderated comments

Please make comments!

I've changed the comment requirements from registered Blogger users to anonymous but moderated. I hope I don't regret this.

One person mentioned to me that he didn't make any comments here because he didn't want to register for yet another account that he'd never use again. Allowing only registered Blogger.Com accounts was an attempt to minimize spam. Spammers are (I hoped) unlikely to have Blogger accounts. By changing it to allow moderated anonymous postings, people without Blogger accounts can post comments, but they won't be seen by anyone but myself until I OK them.

buttons, buttons.

I didn't accomplish much this weekend: I only added a couple of unlabelled/nonfunctional buttons to the pulpit and holders for its lamp. No pictures.

Observing at the Cassegrain focus

Last evening I spent some time on the observer's platform that used to be used some years ago when people visually guided the telescope while recording data at the Hale Telescope's Cassegrain focus.

p.s. Although it isn't obvious in the picture above, the simulated observer's platform automatically follows the Cassegrain focus around, elevating the little green man as necessary. I've briefly considered implementing manual steering controls, but have tentatively decided it'd be too much effort for too little gain. At any rate, in the picture below, he's photographing Neptune.

Pulpit update

Celestia v1.5.1 is now available on SourceForge for Windows, MacOS and Linux! It fixes some bugs and includes support for many more languages. Development effort on v1.6.0 continues. If we're lucky the official release might be this fall.

---

Sunday evening I managed to corrupt some of the telescope's Lua Scripted functions so everything stopped working. Since I'd done a checkin of the broken code to my svn repository, it seemed that I'd lost most of that day's work -- several hours worth :( Fortunately, I managed to find the typos and fix them in about 30 minutes this morning while doing laundry. *whew*

More functionality has been added to the simulated control pulpit.

1. The Coudé arch and Coudé axis flat are now controllable. The arch is raised and the axis flat is lowered when the telescope is used in the 5-mirror-Coudé configuration. (That doesn't actually happen any more because the Adaptive Optics' laser now occupies the Coudé room.) The design of the axis mirror assembly is loosely based on one of Russell Porter's drawings of the Right Ascension drive. I haven't located any photographs of it.

2. Indicators rotate when the control switches for the telescope's counterweights are turned on. The realtime balance meter is not yet implemented. Hopefully I'll be able to change its balance values depending on which instrument is mounted in the simulation.

3. The pulpit's illumination lamp can be turned on and off. The lamp glows but does not actually cast any light. Maybe some future version of Celestia will make that possible.

4. The pulpit's cover opens and closes. I had to take some artistic license with that. I used the same design for its open/stop/close buttons as are used for the doors of the storage rooms. Both the pulpit cover and those doors are manually controlled in real life, but simulating a pushbutton is a lot easier in Celestia.

5. As with the main control desk, the simulated pulpit has an additional "on/off" button which causes the control switches and dials to be drawn. Celestia runs about 20-30% faster when they're not drawn.



In this picture, the pulpit is on the left, while the right half shows the raised arch and lowered axis flat.

Coudé Flat Control

Implementing some of the pulpit controls has required rewriting some of the existing control functions. That's somewhat annoying, although I tried to improve them while I was at it.

The Coudé Flat controls are a good (bad?) example. The crane rotates down and places the flat on the central support column. Then it releases the flat and rotates back up again. The base of the flat is one model: it can rotate back and forth 90 degrees, between the default South-looking orientation, which reflects light toward the Coudé room, and an East-looking orientation, which reflects light toward a spectrograph in the telescope's East arm. The Coudé Flat mirror assembly is a separate model: it can either be at a fixed 45 degree tilt, for reflecting into the East arm, or it be manually or automatically tilted so it continuously reflects light toward the Coudé room as the telescope changes its Declination angle.

Previously the crane was a single model, separate from the models comprising the Coudé flat. None of the parts of the crane model moved, so in V2 its clamping mechanism passes (inappropriately) through the models of the flat when the crane rotates up after placing the flat on the central support.

However, the Pulpit includes a control for the crane's clamping mechanism. V3 now has two crane models. One of them includes a complete model of the flat, with the crane's clamping mechanism holding it securely. The other crane model has the clamping mechanism in the released position, so it'll clear the mirror's models as the crane rotates up and away. In other words, selecting the Pulpit's "place mirror" switch swaps the two crane models and changes the visibility of the parts of the mirror models that are on the support column.

I very briefly considered animating the clamp release. However, the crane has too many articulated pieces; some of them rotate, some translate and some do both. Each of them would require separate ScriptedOrbit and ScriptedRotation functions, carefully adjusted to match their motions with those of the other pieces. Maybe someday Celestia will implement animated bones (models which are constrained to stay in proximity in specified ways). Then I'll consider redoing this.

As a side-effect, I also had to redo how the Coudé flat model was controlled. That isn't entirely finished: I haven't done the code for the switch that moves control from the Pulpit to the Desk. Currently both are active simultaneously.

Here's a picture of the crane when it has just released the Coudé flat on the central support. Note the state of the Pulpit controls.

Seconday mirror covers & pulpit in use

This morning's progress: I added the covers of the secondary mirrors and animated them. When commanded from the pulpit, the appropriate secondary mirror is lowered into position while its covers open. This picture shows this happening for the first Coudé secondary, the one used for the 3 mirror Coudé light path. The mirror is in the process of going down and its covers are opening.

I originally designated this the 2nd mirror for the 5 mirror light path. After an afternoon nap I realized how wrong this was. Both Coudé mirrors have the same focal ratio of f:30. Although not obvious from this angle, the mirror that's halfway down in the picture below is raised a foot or so above the others. As a result, the length of the light path that it reflects is about 9 feet shorter than the length reflected by the lower Coudé mirror. The 3 mirror Coudé light path is shorter than the 5 mirror path, so the upper Coudé secondary has to be the one used for the 3 mirror path. It took me about 20 minutes to interchange their rotation parameters and switches.

Pulpit

No, people don't give sermons here :)

Here's my start at implementing the Hale Telescope's control pulpit, which is located at the south end of the telescope. It is still missing the counterweight balancing meters and some associated labels and switches.



Oh, and its door isn't shown either, only its hinge.

Controlling the telescope

The major features of the next version will be its control desk and the separate control pulpit. Here's the control desk. Its layout is pretty much finalized, although its functionality hasn't been fully implemented. Maybe one more display dial will be added if I can decipher the blurry picture. All the switches go up and down or 'round about, but I need to finalize the details of what some of them cause to happen. Switch action is simulated by clicking on labels -- they're implemented as if they were radio buttons.

Opposite ends of the telescope

Here are some more closeups of the primary mirror and its mirror cell. The mirror's pyrex glass and its waffle pattern were major innovations at the time it was designed, as were its counterweighted supports.









At the other end of the telescope are the focal point of the primary mirror and the secondary mirrors which magnify the image and reflect it to the f:16 Cassegrain and f:30 Coudé focal points. The prime focus cage includes adjustable supports which move the secondary mirrors and the prime focus instruments up and down +/- 1.5 inches.

Comparing versions

Here are some comparisons of a typical feature: the telescope's mirror cell and cassegrain cage as implemented in v1, v2 and v3 of the Addon. (Unfortunately, Celestia still has problems depth sorting transparent objects, so the cassegrain cage's grillework isn't shown properly.)

Hale Telescope for Celestia

Since I'm not an experienced blogger, I've gotta decide what to write. I've decided it might be of interest to some people if I wrote about the developments in the most recent Addon that I've been working on for Celestia: a model of the 200" Hale Telescope on Mount Palomar.

Information about previous versions of this Addon is available at
http://www.lepp.cornell.edu/~seb/celestia/hale_telescope.html

More information about the Hale Telescope and Mount Palomar Observatory can be found at http://www.astro.caltech.edu/palomar/hale.html and at http://palomarskies.blogspot.com/

Celestia is a 3D astronomical visualization program which has become significantly more sophisticated in recent months. Information about Celestia is available at http://www.shatters.net/celestia/

The initial version of the Addon includes a relatively low resolution model of the telescope which always pointed toward a fixed target. If you wanted to change it, the target had to be changed by editing an SSC file (the type of file which is used by Celestia to define objects.) I don't recall how long it took to create that version, several months, I think. It was published just after Christmas in 2006.

V2 of the Addon includes a more detailed model and makes it possible for its user to type commands to point toward various targets and to manipulate some of the model's components -- opening and closing the cover for the mirror, for example. (Details are at the Web site mentioned above.) Most of these updates happened over a period of about 3 months in the fall, and it was published just before Christmas in 2007.

Both versions are available at http://www.lepp.cornell.edu/~seb/celestia/hale_telescope.html

V3 of the Hale Addon is what I'm working on now. The models of the telescope and of the observatory dome are both getting more details. The telescope model is getting more holes cut into it. Less is more! The real telescope has many access holes not shown in the existing models. The support structure for the primary mirror, for example, has more than 40 of them.

The other major enhancement is the addition of two control desks. They emulate the controls which have been used for the real telescope. Instead of having to type textual commands to control the model, one can click on buttons and switches to make the telescope operate. These days, the Hale Telescope is primarily controlled from a computer, but I think that simulating its old fashioned controls is more fun.

More to follow -- maybe even a picture or two!

CelestiaGuru

So, OK, it's a little overdone. But it's the nick I use on YouTube, so I might as well be consistent.


http://www.youtube.com/user/CelestiaGuru