Stripe pattern: Baader UHC-S + ASI1600MMPRO + street light - Forums

Topic starter

Sep 21, 2020

Dear All

In my black and white photos of the galaxies you can easily see this annoying stripe pattern especially in the lighter grey parts of M 101.
In my photos of the nebulas you cannot see this pattern.
Therefore it must have to do with the filter typ as a first guess.

For the nebulas I used the Baader Ha filter. For the galaxies I used the Baader UHC-S filter.
Could it be possible that this pattern is dependent of the manufacturer of the filter?
Should I try another manufacturer e.g. an Astronomic CLS-CCD filter or so?
Could it be possible that this pattern is a kind of polarization?
Should I try to rotate the filter of about 90°?

I don't know what to do to get rid of this pattern.
Can anybody help out there?
Thanks a lot.

Best Regards
Hans

Hans Widmer

Topic starter

Sep 25, 2020

I think I can answer my own question.
I have identified that I had used the same darks and bias for the galaxies pictures which I had used for the nebula pictures.
My exposure settings for the nebulas is gain 200 and offset 30 because of the Ha filter.
But my exposure settings for the galaxies is gain 50 and offset 13 because of the UHC-S filter.
I made now a new set of darks and bias with gain 50 and offset 13 and used them for the calibration of the galaxy NGC 5907 pictures and the stripe pattern has vanished.
Obviously the setting of gain and offset matters for the darks and bias.
I think the problem has solved.
Result:
I have to develop the pictures of the other galaxies again - with the correct darks and bias.
I guess that I will never make the same failure again.

Helpful

Christian Vulpescu

Sep 26, 2020

Wow. Hans, that was very good. I have the ASI 1600 mm Pro cool and hat the same problem but with nebulas.
I will try your method.

Christian Vulpescu

Nov 25, 2020

I have the ASI1600 mm pro, too and had some vertical and horizontal banding. It disappeared after dithering.

Helpful

Hans Widmer

Topic starter

Nov 25, 2020

Christian
Because I always do dithering without guiding and use drizzle integration functions on PixInsight I have no experience how my pictures would look if I wouldn't dither and drizzle.
Hans

Christian Vulpescu

Nov 28, 2020

Hey Hans,

You do it right if you dither. I've tryed it once on the Wizard nebula without and the result was a lot of banding.
This was my first and last time, I have had banding issues with the ASI 1600MM Pro.

Best regards,

Christian