My Aqualine is very yellow if nipple is not "up"

[Scrooge2]

I have a 400 watt, 10K, Aqualine-Bushke bulb that is VERY yellow when the nipple is not up. When the nipple is up, the color is more blue/white, although the intensity does appear a little less to my eyes. This one is not a case of a bad connection, because I took it out and back in several times to test this.

I also used it on a different socket. On this other socket, no matter how I screwed the bulb in I could not get the nipple in the up position. I guess the threads were different on this socket, if the nipple was up then it was too loose to connect, and I couldn't tighten it enough to go around again to get in the right position. Anyway, on this socket it was again very yellow.

I haven't been home since reading this article to look at where the arc is, so that may have some bearing too. I realize this is anecdotal at best, but on my bulb there is an extreme difference. If not in the correct position the color is yellow, yellow, yellow. There is even a 6500K right next to it, and the 10K is definitely more yellow.

[ January 17, 2002: Message edited by: Scrooge2 ]</p>

 

[MattM]

Richard -

I believe you may have missed the main issue regarding the nipple position on MH bulbs.

I don't recall reading any anecdotal claims that there is an intensity difference in the direction of the nipple, or a color temperature difference in the direction of the nipple.

The anecdotal claims I remember reading were that the overall color temperature was different depending on the nipple position and then only for bulbs mounted horizontally - the nipple position is irrelavent for vertically mounted bulbs.

The belief is that the nipple, when pointing down, holds most or all of the mercury droplet contained in the envelope. Incomplete vaporization of the mercury then leads to a different color temperature or difficulty in firing the bulb.

I don't know if there really is a difference, as I have not tested these assertions, but I feel that the testing you did for your article didn't really look at this specific issue either.

 

[npaden]

Richard,

If you could wade through this thread I think it might give you some additional insight into the hobbyist claims on the burn position in regards to the nipple direction.

Here is the link to the thread on reefcentral: RC Nipple thread

I was disappointed to not see a graph for the 10K Ushio in a horizontal burn position as well. I would also like to see the test repeated if possible with the light intensity and color temp tested with the bulb in the horizontal position first with the nipple up and then again with the nipple down. The test would be from a bulb mounted identically except for the nipple orientation and could be done at a set distance below the bulb with intensity readings directly below the bulb and then readings a bit to each side. To offset burn in time possiblities, I think the test would be best if performed with relatively new bulbs and after they have run for a week or so of 8 hour on off cycles in each position. There could be a slight drop off in intensity simply due to burn time, but with just a few weeks this shouldn't be much of a factor.

Looking forward to more articles.

FWIW, Nathan

 

[rharker]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by MattM:
<strong>Richard -

I believe you may have missed the main issue regarding the nipple position on MH bulbs.

The belief is that the nipple, when pointing down, holds most or all of the mercury droplet contained in the envelope. Incomplete vaporization of the mercury then leads to a different color temperature or difficulty in firing the bulb.
</strong><hr></blockquote>

Matt, in most discussions there have been few qualifications regarding nipple recommendations. Invariably there have been broad sweeping statements that MH bulbs work better with the nipple up.

When MH bulbs first fire the metals are not fully ionized, so there's a chance that metals collect in the nipple, but as a bulb burns, the metals are ionized. That's why a bulb starts out considerably more yellow than it ultimately ends up.

One problem in these discussions is that no one distingushes between double ended and single ended bulbs. I tested single ended bulbs, the most common in the hobby. Whether my findings can be extended to double ended bulbs is a matter that remains to be determined.

Richard Harker

 

[rharker]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by npaden:
<strong>Here is the link to the thread on reefcentral: RC Nipple thread[/U]</strong><hr></blockquote>

To judge the significance of your photos in the thread we need to know how they were made. The biggest problem with digital photos is white balance. The camera will try to adjust to what it considers "white" which when photographing metal halide bulbs is more or less a guessing game. One can make an Iwasaki look very white or very yellow in a photo depending on how it is photographed and what it is photographed beside.

The two bulbs in your photos look to be a different color, but calling one "yellow" assumes that the other is white. Unless you've measured the color temperature of each bulb (as I did in my tests), all we can conclude is that one looks yellow compared to the other.

In regards to whether it is "degrees Kelvin" or just "Kelvin" you are correct in the context of black body radiation. It is quite common, however in photometry to refer to color temperature as "degrees Kelvin." In the context of the discussion, my usage was consistent with convention.

Richard Harker