Discover the Overlooked issue with FILTERWHEELS! 

Great video, thanks. 3D printed black discs look great, BUT note however that some plastics can be transmissive in the IR!

Opaque filters of any standard size, mounted and unmounted, are available from virtually any astrogear supplier (they're intended for taking dark/bias frames). They're very inexpensive, around US$25. So it's easy to get them to fill any empty slots.

So timely for me! I just started shooting with a filter wheel and was trying to debug this very problem. I have something to try tonight. Thank you! Clear skies

Hi SashaI have the ZWO 5 postion EFW and the LRGB filters and ZWO Narrowband SHO (S-II, H-a & O-III) Imaging Filter Set.I want to the put LRGB in Filter Wheel but want to use the other slot for one of the Narrowband filter which one should I put in there and use a filter drawer for the other two filters in the Narrowband set.

maybe somebody already suggested this to you, but you should add a wider Ha Filter to your filter wheel. Planetary nebula also emit Nitrogen Nii, which emission line lies directly next to the Ha but will be blocked by your 2,8nm filters.

Oh… this could explain some of my flats. Have 1 empty slot in my ZWO filter wheel. To be safe I’ll make sure to cover the empty slot even if it does not matter for me just to make sure. Thanks

I'm not saying this is a proper solution, but it works pretty well. Gaffers Tape. I put it on my filter wheel when I was first getting filters. Cheap. Light. DARK. I had no idea why I felt that the blank filter slots needed to be blacked out, but it was a strong impression. Only have one slot open now, been taped for a long long time...

What an incredible factoid to have under the sleeve…. 🙏🏼

Good catch! CS!

Very interesting. Did you also find that the flats taken for the filters either side of the LUM filter were also affected? One would imagine that there is not much difference between an empty slot and an IR cut filter.

Yes that's a solution...But not a correct one, 1 reason I like to leave 1 filter wheel open is to do some visual viewing without any filter. What the Filter wheel makers need to do a install light baffles to perfect an open filter wheel slot letting in light causing what you had happened.

Excellent info for sure. Now a dumb question...what is this R+ filter you speak of??

Very interesting. Why doesn't L cause the same problem?

Random question. Will these filter wheels work with other cameras? I’ve been looking for a 36mm wheel that has more than 7 slots

Does this not happen adjacent to the Lum filter?

Hi Sascha, So, I have a few questions, if you don't mind, and I hope you can answer them. So, then, does this mean, that you can no longer be able to shoot without a filter, if you wanted too? Is there no other way to block out the light? Could this light leak, itself, have been sealed instead of blocking off your empty slots? Did you ever find out where this light leak was coming from? If you did, find this light leak, where was this light leak coming from? I am looking forward to your reply on my several questions. I have a new 7 filter filter wheel, for 2 inch mounted filters, coming from ZWO, shortly. I was not planning on using all 7 of the slots so I can shoot without a filter, if I wanted too. Since I am using a One Shot Colour camera, ASI2600MC Pro, I would want to use it without filters, in many cases. Anyway, thank you for the video. It was very interesting and informative, as always. I will reply back after I get my new ZWO filter wheel and try it with only 6 filters. Now I am, naturally, very curious to see if I get the same problem when I do my flats. I will check back and let you know. Maybe, since I am using "Mounted" filters it might make a difference. Or, maybe, since it is a different brand it might make a difference. Either way, I promise that I will stop back into this video and let you and the community know what I find out. Thank you, once again, for the video. Sincerely, Richard Williams Astor, Florida 32102 USA!