Project for a cloudy day

Plot of the regions of sky where my imaging system cannot go without a pier flip.

I sometimes find that my scope can't point at the planned target due to a conflict between the camera and the tripod. The solution is to do a 'pier flip' - i.e. to rotate in RA by 180 degrees. However, after a some time tracking I'll need to flip back because now the camera-tripod conflict arises anew. I'd like to try and map out the regions of sky which are problematic so that I can take them into account when planning. Hence, during this cloudy day I set up in the living room and started mapping out what my limitations are. First, I set the scope on the west side of the mount when pointing at the meridian (I call this my 'normal' configuration), put the RA setting circle at 18hrs. Next, I put the dec. at 0,10,20,30..90 deg and for each value noted down at what (if any) RA value there was a camera-tripod conflict. I then did the same thing with the scope on the east side of the mount (I call this my 'pier flip' configuration). Using a planetarium program (time set to June 24 at midnight  for which RA=18hrs passes the meridian) I then translated my RA, dec. limitation values into az, alt. values. The result is shown in the figure where zenith is in the middle and the horizon runs around the circumference with azimuth angles indicated. For each configuration I have a region where I can't point, shown in red and blue. Now, if only I could figure out a way to use this information in an easy manner to predict if and when pier flips will be required for a given object on a given date. Does anyone know of a good way to do this?

Bubble in Hubble

Bubble nebula using the Hubble palette. Total exposure time is 33 hours.

Finally - I have managed to create an image which is somewhat of a finished product! Sometimes I nearly despair, feeling that I never reach this stage. Instead I fiddle around with calibration, stacking and analysis for weeks and weeks until I start diffusing into other projects, leaving much 'unfinished' work behind me. This morning I got the 'final' stacked, narrowband images of NGC7635 - the Bubble nebula - wrapped up and I vowed to attempt to make something pretty out of it by the end of the day. I chose to use the Hubble palette where SII, H-alpha, OIII are assigned to R,G,B respectively. I also have short exposure length RGB data, but have not yet processed this into something that could be used to create more natural looking stars.

The seeing in this image is ~3.2". It would have been nice to have 2" instead! I have not fallen for the temptation of sharpening and I don't think it would help much.

Earlier today I sent the narrowband images to my good friend, Henrik Bondo, who will attempt to process them into something that has more natural looking colors. So, for many reasons the image shown here is not the final one, after all. We can keep on working on our projects forever - and that's OK!

Full resolution JPG: click here
Some processing details: click here

High thin clouds on and off

Had the AT8RC setup out again last night. Prospects were not very good due to forecasted high, thin clouds and haze. In addition there was a 60% full moon in the sky. Before midnight I did IC417 in OIII light. Inspecting the calibrated images showed that the nebulosity was completely washed out. Sky flux this time was 60% higher than last time I shot IC417 in a moonless and less hazy sky.

After midnight the target was M100 in green light - haze seemed to be less severe then. Comparing to red light data from a few weeks ago with no moon and less haze suggested the images to be of reasonable quality, but not as good. The background ADU was around 2000, compared to ~1000 earlier. I'll do a critical comparison with future M100 green images to find out if last nights run is useful at all - I am not too optimistic!

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