Hello to all Minicam8 users.
I experience a substantial halo when I use the blue filter, that result in a blue halo around the brightest stars.
Anyone else have this issue? Do you have any suggestion on how to deal with it in post processing?
Olivier
Not a Minicam user, but are you sure your blue filter has the correct side facing the sensor? I remember reading a while back that the Minicam filters have two slightly different sides.
Olivier,
As a minicam user, I never noticed this effect. Maybe The0s is right.
Which filters are you using, the 7nm or the new set of 3nm ?
I have the 7nm…
Here is is a comparison of the 3 channels.
I’m pretty sure I put the filters (7 nm) in place in the right direction, following the “V” signs on the side. Can it be that the sign was wrong (it was hand made). How to tell?
📷 image.png
andrea tasselli:
I very much doubt that has anything got to do with filter orientation (for a BB filter, such as RGB, that is). A lot more to do with the refractor being used.
Thanx for the responses. You mean it could be chromatic aberration? I’m using a Takahashi FS60C and I don’t see any halo on my OSC camera (asi676mc).
I will test the camera on a reflector to rule this out.
Olivier G · Feb 21, 2026, 05:09 PM
Thanx for the responses. You mean it could be chromatic aberration? I’m using a Takahashi FS60C and I don’t see any halo on my OSC camera (asi676mc).
I will test the camera on a reflector to rule this out.
ASI676MC has an UV-IR window. You probably will not see any bloat
I suspect the blue bloat is due to UV sensitivity. The Minicam8 blue filter has good transmission (up to 80%) until 400nm.
It is better to have the UV cut at 400 or 420nm.
On this page Minicam8 seems to have an AR window. Changing it to an UV-IR cut glass will eliminate it.
When I was imaging with a cheap achromat and IMX585 OSC even with a color correction filter, still got blue bloat. Used this formula in pixelmath to correct it.
R= R
G= G
B= 1.5xG - 0.5xR , basically creating a synthetic blue channel.
Hope this helps.
ZigZagZebraz · Feb 21, 2026, 08:40 PM
ASI676MC has an UV-IR window. You probably will not see any bloat
I suspect the blue bloat is due to UV sensitivity. The Minicam8 blue filter has good transmission (up to 80%) until 400nm.
It is better to have the UV cut at 400 or 420nm.
On this page Minicam8 seems to have an AR window. Changing it to an UV-IR cut glass will eliminate it.
When I was imaging with a cheap achromat and IMX585 OSC even with a color correction filter, still got blue bloat. Used this formula in pixelmath to correct it.
R= R
G= G
B= 1.5xG - 0.5xR , basically creating a synthetic blue channel.
Hope this helps.
Very helpful thank you! I will search for a filter to cut UV higher than 400 nm.
I looked for the Minicam8. Unfortunately none is available. The 19×12mm (i think) is custom made.
But, the Sloan filter Cyan for Minicam8 has a good cut off for UV. But, it is not pure blue.
If you can stick in a 1.25” filter somewhere to experiment, get a Celticbird one from Amazon. It has cut off below 420nm and above 680nm. Just like an Astronomik L3. On Amazon, I got one for USD15 or so. I have looked for a 2” one from them, they do not have any.
