sokubus

thanks all, I will change the backfocus and redo the flats and than replicate all in a new session. Will keep you up to date about the progess.. Thanks for all the help!

thanks, here a link to the files: https://drive.google.com/drive/folders/1nFkVcIZzbFh58U6johaOC2_ydKlmDtIV?usp=sharing would be great if someone can clarify how much back focus, I need now to add from the 6II Flattener and if this is always set to 7.1mm and I exclude this when measuring the back focus. Got a bit confused now how best to approach this.

thanks to all, so just to summarize if I understand this correctly? I will set the Flattener to 7.1mm (this will always be 7.1 regardless of the rest of the imaging train as I will measure from after the flattener???) from there measured I need a 55mm back focus incl Filters or does it need to be 62.1mm according to this diagram?? I have the camera with 17.5mm Camera to Filter wheel adapter 2mm Filter wheel 36mm Filter 3mm so that;s in total 58.5mm so thats it... ???? no spacer etc. and i am already 3.5mm over due to filter? I read that I could screw the camera onto the filterwheel and to get rid of the 2mm spacer. Shall I do this as well? Thanks for all your help

thanks, not really. street lights are far away and i used a red headlamp during the session. Will sort the backspacing issue now, thanks a lot for that help. Really appreciated!!!

Hi, I am struggling with my first imaging, and I am not 100% sure I have put everything correctly together to achieve the right back focus. My setup is as follows: Zwo Am5 mount, WO 81 GT, WO 6III Flattener, ZWO 36mm EFW, ZWO EAF, ZWO 2600MM and Antila LRGB and Narrowband Filters. My fist images are looking like follows: (see upload) this is with a Luminance filter Where is the blurry ring coming from? I have done calibration frames but you can still see it in photoshop. To achieve 55mm backfocus I have used the I am unsure if this is correct because after the flattner the WO 81 GT is below f 5.4 ??? I have used 7.1mm as disctance on the 6III Flattener.... any ideas? Thanks a lot soku