ZWO Filter Drawer

[Grierson]

I always update my darks library during the daylight hours but when the weather is cool and cooling the camera doesn't present an unnecessary strain on the 294. To date I have had no problem. Having recently purchased a ZWO filter drawer and added it to the light path I am disappointed to to find how much light leaks round the holder making the produced darks useless. Taping round the holder 'cures' the problem but I wonder if I have a poorly machined example or is this typical of the ZWO filter drawer. Any comment from users of this piece of kit would be appreciated. Thanks - John     

[Craney]

oh-err... I've just ordered one from FLO !!!

I'm watching with interest.

[Mctoot]

54 minutes ago, Craney said:

oh-err... I've just ordered one from FLO !!!

I'm watching with interest.

I was thinking of ordering one too… will be interested to see how you find it. 

[Davey-T]

I bought the Baader one after hearing reports of light leaks on ZWO version but it still has light leaks.

Dave

[Budgie1]

I had one of the ZWO filter drawers arrive this morning from a fellow SGL member, so I've not had chance to try it out yet.

I always thought that Darks were for the likes of sensor noise, hot/cold pixels and amp glow on the camera sensor, so what was in front of the sensor didn't matter. On advice I read on here somewhere, I remove my ASI294 from the scope and just put the cap over the sensor for shooting my dark libraries, which I'm about to start doing for the coming season. 

I've had a look at mine and I have two filter holders with it. When I hold a head torch behind the drawer I can see light coming through between the joint where the magnets are.

This only happens on one of the filter holders because the other one has an extra lip which covers this gap and I can't see any light through this holder when it's pressed fully home.

Here's the difference between the two:

The images of the filter holders on FLO, both the main kit and the spare holder, both show the lip on the holders but maybe the one I have is an earlier version?

Now I know about it I can work around it with some tape to cover the gaps, or just get another holder. I'll still make my dark libraries with the camera off the scope though.

Edited July 15, 2021 by Budgie1

[Grierson]

Martin, I would agree that all that is needed to produce darks is the covering of the sensor. (And of course timing and cooling) However, in my case it has always been far easier to produce the darks with the camera in situ by capping the ‘scope. The fact that the drawer leaks light leads me to wonder what impact that will have on images when the kit gets some use in the coming months.

[Davey-T]

I also got light leaks on flats  using the Badder filter draw, ended up putting the scope in a cardboard box to do them otherwise have to do them at night.

Dave

[Budgie1]

@Grierson , I'd be interested to know whether your light leak problem was from a holder with or without the lip? I noticed on mine that the one with lip did let some light through but that was because it wasn't fully seated correctly. A little push to seat it and it was fine.

I've only had the ASI294MC since January but I will stick with the same gain & offset throughout the coming season (late August to early May for me up here). So I intend to build a darks library for each exposure length I'm likely to use so I can reuse the masters for each through the season. Unless I notice any issues creeping in which may be darks related.

Where the light leak may be an issue is when creating flat-dark frames the following day, in which case I'll see if black insulating tape will sort it.

[Grierson]

Dave that is clearly the way to go.

Martin, my version has ‘lips’ with the arc of the holder resting ON the drawer body when fitted. I notice that the holder of the ‘ZWO Filter Drawer for EOS Lenses’ is actually countersunk in to the body when fitted. Could it be that ZWO has learnt a lesson?