Unresolved flatfield issue in MaxIm

Despite several days worth of testing, fiddling and communicating on Yahoo groups I have not managed to solve my problem with MaxIm. When combining individual flat field frames with sigma clipping or SD masking the resulting flat field calibration fails to remove dust doughnuts. Working with the same data in Mira I have no problems. I will now generate my dark corrected master flat field in Mira, then use it in MaxIm. In future sessions I will try to use Maxim again - if it continues to fail I'll have to contact Cyanogen directly. Irritating!!!

Good seeing, bad calibration

Details of my (flawed) flat fielding in MaxIm (click for full size version)

Seeing last time out, Feb. 19th, was the best I have experienced so far while working a long focal lengths. Typical stellar FWHM on long exposures was 2.2 arcsec - on most nights I get ~3 arcsec. That was great! Not so great was the calibration problems I encountered in MaxIm DL Pro. I use a SBIG ST10-XE camera and in the past I have used Mira for calibration. I take a bunch of flat fields using the twilight sky and a white cloth in front of the scope. All light and flat frames are followed up with dark exposures of equal length, so there is no need for bias frames. The sky flats vary quite a lot in their brightness due to the increasing sky brightness, but this is normally of no concern since the frames are scaled after dark subtraction to match each other before the images are combined. However, when using the calibration features of MaxIm the flat fielding failed to remove dust doughnuts. When I processed the same frames in Mira the flat fielding went just fine - hence I suspect some problem in MaxIm, either due to my ignorance or due to a bug. I really want to switch to MaxIm since it has many good features that work well. The image below details what I am doing. A few of the original raw files can be downloaded here (28MB) - can someone with MaxIm do a good calibration with this and send me some advice? My email address is mikael.svalgaard@gmail.com - thanks!

Promising weather....

Setting up from scatch....

DMI promised a fair chance of clear weather tonight, so I'm setting up my deep sky astrophoto rig. I have to haul up everything each time, unless I choose to leave it in the garden. Sometimes I do this, if the weather is good and stable, but I'm always worried about thieves or vandals - our garden is practically open space to the public. Target for tonight is IC443 in OIII narrowband. I have been shooting this supernova remnant for the past several weeks, have bagged H-alpha, SIII and RGB already. 

Half an hour later

In the beginning....

Ingrid and me setting up in Siberia

Hello there,


I am starting this blog to share my endeavors into astronomy with the rest of you. I've had a web 1.0 site for years (www.leif.org/mikael), posting finished astrophotos and solar eclipse travel descriptions. But what I really like about this hobby is the PROCESS and the JOURNEY, rather than the final RESULT or DESTINATION. It's like Lego - once you have finished building it just sits there - a bit dead and boring. My daughter, Ingrid, knows about blogs and stuff so she's my tech and moral support. Anyway - that's it for now; just got to figure out what's next.....

-Mikael