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  • 294mc pro and narrowband filter flats problem

Hi all,
I searched for hours online, in forums, in facebook groups… I am overwhelmed.
I have a Redcat 51, paired with a 294mc pro with L-Extreme. I use an amazon flat panel, and never had any problems before.

I have problems taking flat frames since using this Optolong narrowband filter. I have found many people having problems online too with this camera.
I have tried everything. From 0.4 sec to 11 sec flat frames, calibrated with darkflats of course and darks. I keep getting this red pattern all around, it keeps overcorrecting sadly. If Zwo support could help, it would be very great from you guys. I know you are pretty much occupied these days. Thanks anyways.!

    Im having the same issue with the same setup except I'm using the 533mc pro. I've sent a ticket and currently awaiting a reply. I'll post here with any updates I receive.

    Anthony123495
    It is the characteristic of the sensor, and can be calibrated.

    Please try these links.

    https://www.facebook.com/groups/zwoasiusers/permalink/1405257593166618?form=MY01SV&OCID=MY01SV

    https://www.facebook.com/groups/zwoasiusers/permalink/1399824943709883

    Some other customers have the same situation, It is the characteristic of the sensor, and we attached a calibrate method from Simon for your reference, you can try it.

    Things I see regularly are:

    Not using flat dark calibration process - do not use bias on this camera!
    the best results are by using darks that match flats well - use same gain - length and temperatures
    using 28K as ADU value
    ensuring the light source has well balanced channels. - RGB channels must be well aligned else one channel will under / over expose - sadly usually red!
    do not use less than 3s exposures on 294MC pro - less than this can lead to inconsistent values in ADU
    create a master from the short darks and calibrate the flats by using the master and calibrate only - do not optimise
    create a master flat with the calibrated flats
    create a master dark that matches the lights use same gain - length and temperatures
    calibrate the lights - again do not use optimise only calibrate

    using these steps I have not found an issue with my L-ext or Lenh / ZWO duo etc

    most problems I have seen are not following these or stretching flats and worrying about the pattern - yes you will see the pattern sometimes stronger on some setups - not all setups seem to have the same response

    I hope these help but this article did more harm than good as I see it reposted all the time

    294mm show similar patterns but again can also be managed by the above process

        I am using a 294mc pro (3 years old) and the Lextreme filter without these issues. Even short flats are no problem for me.

        But I know the issue exists and I have seen people staking in pixinsight having it but not when using stock settings with deep sky stacker. Give it a try.

        3 years later

        Tech@ZWO

        How do you do more than 3 sec? With the lowest brightness of my flat panel, and auto on the asi air, it is right in the middle of the histogram but at best .7s exp. so around 700ms. Brightest is like 200ms. I thought gain had to be the same for the flats as the lights. Or all of this.

        I am also having the same issue and it's annoying af. https://i.imgur.com/3VydSVk.jpeg left one is no flats at all, middle is 3.3 sec flats with 3.3 second "bias/dark flats" and the right is 3.3sec flats with 1ms bias... so bias time don't mean jack with this cam apparently. I have tried very short ones too, like 200 ms flats. but same issue lfmaoooo.

            navyguy
            3s flats is recommended but not necessary, the most important things is to make sure the ADU value of RGB channel is within 20-40k. you can disable the AutoWB in ASIFitsview to check the value.

                Tech@ZWO Idk, every single place I see has the 294 needing flats longer than 3 or 4 seconds, if not more for getting rid of that pretzel pattern that shows up on flats with like an L-extreme.

                  a month later

                  Similar issue. Using auto exposure on flats with either Tee shirt method or light panel my flats have a redish hue. Equip. 2600MC pro, ASKAR 130 PHQ, Optilong l extreme.

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