Auto iris lens settings

Forums Meteors Auto iris lens settings

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    Callum Potter

    I was womdering if anyone that uses an old plain Watec 902H camera with an auto-iris lens could let me know what settings they use on the lens for Level and ALC?
    (I have a cosmicar/pentax 6mm f/1.4)

    And on the camera shutter on or off, and AGC low or high?

    My video feed seems to be a bit dim…

    Thanks, Callum

    Dominic Ford

    I’d also be interested to hear from anyone who’s getting good meteor captures with the Watec 902H.

    If I recall correctly, the AGC only has low and high settings. As Callum says, the low setting is very dim, so you only record fireballs. The high setting is very noisy. If you stack the frames for 30 seconds you can get some nice deep images, but for meteor searching it’s not great, because the meteors are lost in the noise.

    My solution was to upgrade to a Watec 902H2 Ultimate, which has an AGC knob, so I could tune the gain to a happy medium. But I do gather others are getting on OK with the 902H. I was wondering whether some kind a pre-amp between the camera and the digitiser would help, but Callum tells me he’s tried that and it hasn’t helped!

    William Stewart

    Hi All,

    This document on the NEMETODE website provides recommendations for the various settings (and indeed where some of the difficult to find switches are) on the different versions of Watec 902 (and 910) cameras.

    It should be noted that the original Watec 902H is unable to drive the iris on a DC Auto Iris lens (see page 5 of the document). Removing the plug and applying a voltage across the apporpriate wires fuly opens the iris.

    For the original Watec 902H I’d recommend keeping the Shutter OFF and experiemnting with the (tiny) AGC switch. Depending on the camera itself (depending on when they were made, there appear to be some differences in design / manufacturing tolerances) and local light pollution levels, some report better images in the HI position while others report LO. The factory default is HI. When used with an Osprey 210 video card, the optimal position is usually LO.

    As noted in earlier posts, it’s definitely worth optimising the brightness / contrast settings (usually software sliders).

    Hope this helps.


    William Stewart

    I neglected to mention typical performance of the original Watec 902H. I operate three of these as my main cameras from a resonably dark site (visual LM is about +5.5). Fitted with Computar 8mm f0.8 lenses, stellar LM on the cameras is +5.5 and the faintest meteors recorded are typically +3.2

    Callum Potter

    Thanks for the suggestions Bill & William.

    I did use hi AGC before (with another lens), but the images were fairly noisy, so I switched to low.

    I will try some more experimentation, and rewiring the lens control sounds attractive.

    Will report back on progress…

    Cheers, Callum

    Bill Ward


    The dim images MIGHT be being caused by the level sttings. Firstly let me disclaim by saying I’ve never used a 902H camera for meteor observing. However I have experienced a similar problem in a more professional capacity when I thought I ought to be seeing brighter images than I was.

    Before proceeding does the 902H have a small adjuster screw any where? If so, as in my own case, have the camera on and in a fairly dim setting, ALC low, then slowly (and gently, these little pots aren’t meant to be tweaked too many times) adjust the control screw. The level control adjusts the feedback to the iris and if it’s not set properly even in dark dark conditions the iris may not fully open. (resulting in dim images). If this is the same on the 902H then at some point the iris will open fully irrespective of the illumination and you should see a much brighter image. Once you’ve found when it opens the iris take the pot to the end stop in the same direction. This should in effect keep the iris open under all conditions.

    I’d use AGC low all the time if the above works, AGC high can be VERY noisy with a fully open IRIS.

    Also I’d try “shutter” OFF first. This is related, usually, to the auto shutter settings. On some cameras this shutter really means the electronic exposure. OFF normally defaults to the longest exposure. To test this try it in day light and very quickly it will become apparent if this is the case as the image will saturate out because the shutter speed will not increase.

    Hope this helps,



    PS Also, some video capture cards seem to automatically produce fairly dim images. You may also need to adjust Brightness/Contrast/Gain on the video control panel. I had two dreadful Hauppauge boards that had this problem, every single power up they had to be adjusted. Thay are now in the bin! I’d try sorting the camera first though….

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