As most people already know, the original ZWO filter drawer leaked light like a sieve. They could not be used in any suburban setting unless you wrap opaque material around them.
ZWO then introduced a "new" version, which is just a small change to the removable filter holder, by extending the length of the lip of the filter holder. They must not have used one themselves, otherwise they would have realized that the light leak is not just at the ends of the filter holders, but thoughout the length of the circumference of that lip. So much for that "upgrade."
Just a couple of days ago, I found out that ZWO has release yet another new version of the drawer, and my favorite delear happened to have one last one.
Anyway, this one (mine is a M54 version) appears to have cured any light leak. I tested it with an ASI2600MC, and with a metal M54 cap (Plastic caps often pass IR).
The camera is placed under a desk lamp, so there is probably more light than a typical setup in the dark outdoors.
ASI6200MC is set to 10 dB gain, and 800 second exposure (probably longer than a typical ASI2600 exposure) in ASIImg. The cooler is set to +10ºC (room temperature is at +24ºC). As usual, tons of speckle noise from the IMX571 but no visible leak.
The Max ADU of 65535 is probably caused by couple of bad saturated pixels, and not a light leak, since that would manifest itself as a broader histogram line.
This next picture shows the difference between the two filter holders; old on left, new on right:
You definitely cannot use old holders with new drawer.
This shows the drawer bodies (again, old left, new right):
The thicknesses and even diameters are identical (well, identical to ZWO's machining standards), so any PreciseParts spacers that you have used for backfocus will continue to work.
If you are going to switch to this new drawer, try one first for leaks before you buy more holders for it, since I have only tested a sample of one, and only the M54 version.
Caveat: don't know yet about internal reflections from bright stars. That has to wait until I can actually see stars :-).
The distance of the glass from the sensor may be slightly different too. So, if your vignetting was marginal before, this might push it over the edge.
Chen
