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Post by Ron Walker on Oct 1, 2022 10:50:38 GMT -7
Posted by: Ron Walker Jun 6 2011, 04:38 PM
I haven't done a review for a while as I have been resisting buying anything new. First of all I'm very happy with what I have and second the economy has put me in a "cheap" frame of mind. However, if the cost of something gets low enough, the planetarium bug bites and that's what happened.
I've always liked the look of the Discovery Ultimate Star Planetarium as it looks a lot like my favorite machine the Zeiss model II. Since I'm always curious as to how the various small hope planetariums perform and am always looking for the best low cost machine to recommend, I was looking for am opportunity to test and review one of these machines. I was not about to pop for the $79 version as I would probably never really use the projector but it sure looked interesting.
Well, the fates looked down kindly and my low bid was accepted so I am now the "proud" owner of one of these devices.
First some basics. It is surprisingly large. This might be me as I find the original Spitz A-1 to be surprisingly large but I don't think so. After all, the Spitz Jr. looks just about the way I expected it to look. This projector stands almost a foot and a half tall on a foot diameter base. Impressive. Did I say it looks like a Zeiss Mark II, very impressive. Unfortunately, that is where impressiveness ends.
The projector is not only large, it boasts a mini-computer and drive motors as well. By imputing a question or requirement (where is the Big Dipper) the motors will drive the device from a vertical stop/storage position via two motors (one for latitude and one for diurnal) and project to the zenith of the room the object or constellation in question. Neat....and the projected stars appear surprisingly round and sharp. I must see what type of bulb they use. This could be a great find, as the star globes are each 5.5 inches in diameter. that means that the bulb at the center is only 2.75 inches away from the pinhole. Wow, what kind of light source is this?
What a deal, a projector with two drive motors, a computer, sharp projected stars, a separate north and south star ball, could it possibly have slip rings, and all for $80 retail. This could certainly be the new small planetarium projector of choice! Wait, something is not right.
Now one must remember that this was obviously a used machine and the instruction manual had been long lost. It would certainly not last forever but it should last a little while.... The latitude drive died after three excursions. Well the motor turns, I can here it, so a gear must be a problem. You get what you pay for I told myself, but the reviews on the Discovery web site tell me otherwise. A lot of problems with everything. But this is my review and those of you that have followed my other rants and ramblings shall not be disappointed. And you all know how much I enjoy taking things apart to see how they tick.
But I said, "Something is not right". One must remember that I am always looking for a true star projector in any planetarium device, one that shows stars correctly under a dome. This technology existed in the original Spitz Jr. so it is not difficult to achieve. But all I see projected on the ceiling above is a cone of stars, perhaps 30 degrees or so, of the constellation requested. Certainly not the half hemisphere that I expected. Also no slip rings, as the machine returned to its original vertical position when a new request was made.
More to come soon, and pictures.
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Post by Ron Walker on Oct 1, 2022 10:51:06 GMT -7
Posted by: moonmagic Jun 7 2011, 01:54 PM
I'm glad you reviewed this one in particular. It also has interested me several times. Surprised to learn that it does as much as it does. Was not expecting it to be a large as it is either.
Understand you are "gearing up" for a bit of a summer "adventure." Hope you have a good fun and safe trip. I know I must not be the only one who is somewhat envious. Wish I had the availability to join in, but not in the schedule or bank account this year. mm
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Post by Ron Walker on Oct 1, 2022 10:51:26 GMT -7
Posted by: Ron Walker Jun 8 2011, 12:15 PM The first thing to look at is the bulbs used. Finding good bright bulbs with small filaments is always exciting. Removing three small screws at 120 degrees allows the removal of the top half of each star globe. A look inside reveals:  Interesting, the bulb is at the bottom of the globe, not the center. Now I can understand two things. Why there is just a cone of stars visible, and why they appear sharp and round. Sharp and round because with the bulb at the bottom of the star globe, an effective star globe diameter of 10 inches is simulated. A cone of stars because with the bulb not in the center, the thickness of the star globe itself would act as a shutter closing off light output for stars further from the point directly opposite the bulb. A look into the star globe from the bulb's pov reveals:  A better look at this effect can be seen from a point further back.  This is bad from this planetarians point of view and explains why the projector doesn't/can't project an entire hemisphere of stars. Perhaps the thinking was that virtually everyone who used this machine would be doing it in a square, flat ceiling-ed room, thus no need for an accurate projection. As an educational tool it will show the constellation talked about and its immediate neighbors, but not in proper perspective to ones location. That is it projects the constellation in question at the zenith (center of the projected cone) and not in the proper location with respect to ones latitude. Now, as I said before, this was used and the operators manual was missing so perhaps I'm missing something, but from what I see, I don't think so. As a projection planetarium in the classic sense, this unit falls flat. One might first assume that with two star globes the unit would emulate the big Zeiss but alas not so. The two star globes are never on at the same time. The southern star ball is an operational copy of the northern one and only lights up when facing up to show constellations around the southern pole. Also note that there is very little difference is the hole size (magnitude) of the stars projected. Also the placement of stars is in question. Look at the big dipper at about 7:30 in the picture above. The bowl stars are just not right. At first I thought this might have something to do with the perspective caused by the placement of the bulb, but no, look at the handle of the little dipper. Those three stars are not in a straight line in my sky. |
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Post by Ron Walker on Oct 1, 2022 10:51:54 GMT -7
Posted by: Ron Walker Jun 8 2011, 12:32 PM With the operating star globe pointing straight up (putting the north pole directly centered above) the bulb operates at the bottom of the star globe. As the projector rotates around, the bulb on a gimbal and with some small weights, always remains at the bottom position (straight down) of the globe. Rotating the projector 180 degrees results in a bulb position as this:  At this point the opposite star ball would be operating as the light from this lamp would illuminate the central core of the projector. Placing the projector on its side and supporting the lamp support ring shows the gimble very clearly:  The bulb itself looks very much like a Mini-Mag Light bulb. I have one around here somewhere but I can't find it right now (getting old is bad for the memory), however I can compare it with our tried and true Stinger light bulb:  The Stinger bulb is on the right and the glass envelope is substantially larger. What counts is the filament size and in that they are virtually identical. As Ken has pointed out, the larger envelope is better for a lot of reasons I won't repeat here. Still to come, the planet projector. |
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Post by Ron Walker on Oct 1, 2022 10:52:16 GMT -7
Posted by: Ron Walker Jun 8 2011, 03:47 PM On the side of this instrument is the planet projector:  This is an optical projector with a plastic lens. The projection port (blue and to the left) can be manually moved from horizon to zenith by hand. Turning the round dial and aligning the name of the object you wish to see with the projection barrel projects the requested image. Removing the knob allows access to the lamp which is a small flashlight bulb, the kind with a lens on the top.  A close up look at the knob reveals a film strip of images right behind the lens when in the projector.  This bulb will go on when the planets button is engaged on the control panel. The computer will talk about the object requested but the operator must set the slide correctly behind the lens. To facilitate this, the material on which the names of the objects are printed contains a green phosphor and if exposed to a bright light before the room is darkened, it will glow to allow easy reading and alignment. |
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Post by Ron Walker on Oct 1, 2022 10:52:39 GMT -7
Posted by: Ron Walker Jun 8 2011, 04:15 PM Looking inside the base reveals the electronics.  Power comes in from a wall wart as 6 volt DC current. It is sent to the power supply board to the top of this picture. A small speaker in the center faces directly upward so everyone around the room can hear about the subject selected. At the bottom is a large dial volume control which to my old ears needs to be all the way up all of the time. To the right one can see a substantial amount of wiring disappearing into the "computer" which faces the operator with a small back lit readout providing the same information as the audio commentary. This I imagine would come in handy if you wanted to be your own lecturer or wanted to keep the audio silent. From the power distribution board to the top, there are several small plugs that take and receive information from various places around the projector. As you would imagine, a substantial number go into the central core because most things happen there. These wires are hidden inside one of the legs of the machine but can be seen here.  All in all this is a most sophisticated machine for the money. I am actually surprised as to what you get both mechanically and electronically. But IMHO all of this engineering does not make up for the units basic failing. As a planetarium projector (and that is what I'm judging) it falls short. It will not show the entire canopy of the night sky from horizon to zenith. As a teaching instrument it both succeeds and fails. Yes it shows the constellation and those adjacent to it, but fails in not placing said constellation it the owners night sky. Constellations are not all directly overhead all of the time. Also (as mentioned before) most of the constellations don't really look like they should look. That is truly an error that could have been easily avoided. I will continue to delve into this unit. I need to see why the diurnal motor isn't driving the projector. Then it will go with others in my collection and probably not be used much at all. It is interesting that with all the technology packed into this unit, the Spitz Jr. still does a better job as a planetarium projector and educator. |
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Post by Ron Walker on Oct 1, 2022 10:53:04 GMT -7
Posted by: mcherron2 Jan 2 2014, 08:32 PM
Ron,
Did you ever determine the projector bulb used in the Ultimate Star Planetarium? My daughters has burned out and the manual does not specify a replacement. only a defunct customer service number to call. Discovery Channel customer service was no help at all. I looked at Radio shack and and found a 12V and a 2.5V krypton bulb that looked similar size, but you mention the 6V power supply so I do not think either is correct. You mention a similar tried and true bulb, but I do not know the source or specs to look for.
I swapped the southern hemisphere bulb into the North as this is the only one that works in night mode, but obviously this is only temporary fix.
Thanks for your help in advance,
Mike and Arianna
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Post by Ron Walker on Oct 1, 2022 10:53:39 GMT -7
Give me a couple of days to get into the unit again to find out the voltage the bulb runs on and a good replacement. If I forget blink.gif (and at my age I often do) please just post a gentle reminder to jog my memory.
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Post by Ron Walker on Oct 1, 2022 10:54:18 GMT -7
Posted by: Ron Walker Jan 4 2014, 06:02 PM
The original bulb is designed to run at 5-6volts and pulls roughly 1/2 an amp. My guess is that it is powered directly from the wall wart but without a tad more research and wire tracing I can't be sure yet. The Stinger bulb (a favorite here at OCP) runs at a little less then 4 volts but pulls substantially more current at around 1.5 amps. I'm not sure if the power supply would handle the extra load. A voltage dropping resister would need to be placed in line with the lamp to protect a filament burnout. The biggest problem that I would worry about is that the lamps are turned on and off by electronic (transistor) switches. I don't have a schematic so I have no way of knowing how much current these circuits will hold. More later.
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Post by Ron Walker on Oct 1, 2022 10:54:40 GMT -7
Posted by: Ron Walker Jan 5 2014, 11:35 AM The more I think about it the less I would recommend the use of a Stinger or mini-mag bulb. Both require some minor electronic surgery and if you are not proficient in the art of soldering I would not attempt it. There is also the problem of the extra current load that could do harm to the mini-computer in the projector. Better to try and find a direct replacement for the lamp. As you may have read, an extremely small filament (required for pin-hole star projection) usually goes hand in hand with a very low voltage. Six volts (required in this case) is pushing the upper limit for a small filament. There are a number of small bulbs called "grain of wheat" which could be suitable for this purpose, but most tend to have a "V" shaped filament. I did find a small lamp only an 1/8 inch in diameter and a 1/4 inch long for a reasonable price of $0.59 which should be electronically compatible. Not having actually had one in hand I cannot comment on the filament size so this is purely experimental. Do to the design of the projector, the end of the bulb needs to to smooth and rounded which is hard to find in such small lamps. They are available here: www.mpja.com/60V-Micro-Lamp/productinfo/8982%20LAYou would need to trim the wires down to a small bi-pin to fit them into the socket but they should be electronically compatible. Since the light is only used off of the end of the bulb, the "V" shape (if indeed this lamp has that shape) should be kept to a minimum. I have ordered from these folks several times and the only drawback is the shipping cost for very few items. I normally wait until I have a bunch of things so as to lessen the shiping cost per item. However, you could call them and see if they might just mail a bulb or two for experiment sake. I will probably get some of these with my next order as I am always looking for new and useable bulbs but I am not at all sure when that time would be. Other then a large filament one never knows exactly how bright the lamp will be at its rated voltage. If it is a single strand "V" shaped filament, it will not be as bright as a tightly wound one. Again this is an experiment with an unknown result. |
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Post by Ron Walker on Oct 1, 2022 10:55:20 GMT -7
Posted by: jimzone Jul 8 2014, 07:48 PM
QUOTE(Ron Walker @ Jun 8 2011, 03:47 PM) *
On the side of this instrument is the planet projector:
This is an optical projector with a plastic lens. The projection port (blue and to the left) can be manually moved from horizon to zenith by hand. Turning the round dial and aligning the name of the object you wish to see with the projection barrel projects the requested image. Removing the knob allows access to the lamp which is a small flashlight bulb, the kind with a lens on the top.
A close up look at the knob reveals a film strip of images right behind the lens when in the projector.
This bulb will go on when the planets button is engaged on the control panel. The computer will talk about the object requested but the operator must set the slide correctly behind the lens. To facilitate this, the material on which the names of the objects are printed contains a green phosphor and if exposed to a bright light before the room is darkened, it will glow to allow easy reading and alignment.
Is there supposed to be an additional lens in front of the bulb? The unit I bought at Goodwill had a broken wire on the bulb socket that I soldered back, so now it turns on and off with the Planets button. However all I see are unfocused blobs of light of different colors when I move from one planet to the next. There appears to be a missing lens (?) Also, there's no audio commentary about the selected planet that you mentioned. I don't know how to get that to work -- no user manual and I can't find one to download. Thanks for any help!
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Post by Ron Walker on Oct 1, 2022 10:55:53 GMT -7
Yes, there is a lens in the flared blue tube extension off of the black tube making a simple slide type projector. I have this unit in several pieces right now trying to repair a motor drive. When I get that part fixed and the machine back together I will see how to get the audio. As I remember one just pushed the button marked planets on the front and it gave its talk. Make sure the volume control on the right side of the unit is turned up.
I have no book either. Perhaps if someone out there has one thay could scan it and post it.
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Post by Ron Walker on Oct 1, 2022 10:56:23 GMT -7
Posted by: JMeade Nov 6 2014, 03:20 PM
QUOTE(Ron Walker @ Jul 9 2014, 11:20 AM) *
Yes, there is a lens in the flared blue tube extension off of the black tube making a simple slide type projector. I have this unit in several pieces right now trying to repair a motor drive. When I get that part fixed and the machine back together I will see how to get the audio. As I remember one just pushed the button marked planets on the front and it gave its talk. Make sure the volume control on the right side of the unit is turned up.
I have no book either. Perhaps if someone out there has one thay could scan it and post it.
Hello, I have a book that I have scanned in PDF format.
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