Altman 902 optics

[Smayniac]

I've read up on the threads on the 902 here and don't see my question. I read over the spec on the light and discovered it's designed with a pair of 4.5 x 9 lenses in the forward positions. Has anyone tried, or does anyone have thoughts on bumping those to 4.5 x 12 lenses to increase the focal length and therefore the throw and intensity of this unit? Altman says the beam angle range on this device runs from 33 to 45 degrees, kinda wide for a followspot, if I can get it down to 20 or 25 degrees I can get that much more light on stage in a more useful size pool.

thoughts?

thanks,

Bob

[church]

I've read up on the threads on the 902 here and don't see my question. I read over the spec on the light and discovered it's designed with a pair of 4.5 x 9 lenses in the forward positions. Has anyone tried, or does anyone have thoughts on bumping those to 4.5 x 12 lenses to increase the focal length and therefore the throw and intensity of this unit? Altman says the beam angle range on this device runs from 33 to 45 degrees, kinda wide for a followspot, if I can get it down to 20 or 25 degrees I can get that much more light on stage in a more useful size pool.

thoughts?

thanks,

Bob

a 4.5 by 12 is an unusual lens so expect them to be difficult to find. I would not expect the light output to be great, the aperture of a 4.5 diameter lens is small and you will probably find the light out the front is not what you would expect. The optics design of the 902 is well beyond its sell by date. I played similar games with a Dynaspot which is of similar vintage it was interesting to change lenses etc but in the end it did not even come close to the performance of my S4 on a stick - so I sold it.

Good luck

[Les]

If you're feeling adventurous, you might consider losing the 4.5" stepped lens in the back as well as the mogul prefocus socket and replace them with either an ENX (you'd need a fan), or a TP-22 socket and ellipsoidal reflector. You may or may not need additional lensing -- I know that I tried a similar setup on an old Little followspot without adding lenses and had decent results... Just don't scrap the old parts so you can go back if it doesn't work out.

In essence, you'd be recreating a semi-modern zoom ellipsoidal optic train because the stepped lens in the rear is primarily gathering the light from the lamp. An MR or ellipsoidal reflector would take care of that for you. YMMV because similar such spots such as the 1000Q and Comet use a rear plano-convex lens just in front of the iris, but a single lens up front. You apparently already have dual lenses, but I am unfamiliar with the 902 optics so I don't know the position of these lenses. I am mostly going off of memories from Dynaspots and my old Little spot which were similarly set up optically. This post is totally assuming you have an old stepped "conza" lens right in front of a honking mogul prefocus lamp.

You wouldn't help your field any, but you'd get more light in the beam.

[church]

If you're feeling adventurous, you might consider losing the 4.5" stepped lens in the back as well as the mogul prefocus socket and replace them with either an ENX (you'd need a fan), or a TP-22 socket and ellipsoidal reflector. You may or may not need additional lensing -- I know that I tried a similar setup on an old Little followspot without adding lenses and had decent results... Just don't scrap the old parts so you can go back if it doesn't work out.

In essence, you'd be recreating a semi-modern zoom ellipsoidal optic train because the stepped lens in the rear is primarily gathering the light from the lamp. An MR or ellipsoidal reflector would take care of that for you. YMMV because similar such spots such as the 1000Q and Comet use a rear plano-convex lens just in front of the iris, but a single lens up front. You apparently already have dual lenses, but I am unfamiliar with the 902 optics so I don't know the position of these lenses. I am mostly going off of memories from Dynaspots and my old Little spot which were similarly set up optically. This post is totally assuming you have an old stepped "conza" lens right in front of a honking mogul prefocus lamp.

You wouldn't help your field any, but you'd get more light in the beam.

Les offers a better approach - I tried this with my Dynaspot by taking the guts from an overhead projector which used the ENX lamp with a series diode and installing it in the Dynaspot. I was able to leave the original mogul lamp socket in place, I removed the condensor lens before the iris. It produced more light than the DTJ 1500W lamp. I eventually refitted all the dynaspot bits and sold it because while it worked it was still not as good as a S4 on a stick. It was fun to play with. The optics are very ineffecicient compared with modern designs - huge lamp filaments and small diameter lenses.

Re the lenses both the 902 and the Dynaspot use a 4.5 * 2.5 * 6.5 conza before the iris.

The Dynaspot centre lens is a: 4.5 * 6.5 for the dynaspot and a 4.5 * 9 for the 902

The front lens is a 4.5 * 9 for the 902 and a 4.5 * 12 for the dynaspot

[Smayniac]

Thanks All,

I convinced my producer to throw down for a source four and iris which I plan to mount on the stand from the 902. I came to the conclusion that while I could get the lenses and make the changes, I still wasn't sure it would make the light any more viable in our space. So, new nineteen degree on it's way; now I just need to find the fitting for my old spot stand to half inch bolt.

Someday we'll have the money for a real spot and the S4 can go into my regular lighting inventory.

Bob

[church]

Thanks All,

I convinced my producer to throw down for a source four and iris which I plan to mount on the stand from the 902. I came to the conclusion that while I could get the lenses and make the changes, I still wasn't sure it would make the light any more viable in our space. So, new nineteen degree on it's way; now I just need to find the fitting for my old spot stand to half inch bolt.

Someday we'll have the money for a real spot and the S4 can go into my regular lighting inventory.

Bob

you will also find a balance yolk useful, these can be purchased or made yourself. You can also make a spigot by welding a nut to the top of a piece of tube that will fit inside of your stand. I also installed a cheap bearing on the stand between the extension pipe and the base pipe to give smooth pan operation

[JD]

The 902 always was a "head scratcher" for me. How could something use so much power and put out so little light?!

I do recall someone who modified one to use an FLE lamp (360 watt) and changed some other things around, basically converting it to a clunky version of a "Luminator." I checked through the forum here and didn't find it, so I assume it was outside the forum.

If there are few color changes involved, the S4 stick would be the way to go. There are external booms available so that can be added. The only drawback is the lack of a fast douser, so your in's and outs involve using a lamp dimmer. The other way would be to go with an Altman Luminator. http://www.altmanltg.com/altman-ligh.../luminator.pdf which will give you many times the light output at a small fraction of the wattage draw. (Have one myself.) They have a very smooth douser and a built in boom so you have a full featured spot. They run about $950.

At 100 feet:
902........ 10 fc with 1,500 watt lamp
Luminator 38 fc with 360 watt lamp