This image shows NGC 4945 (Caldwell 83) with Xi Centauri just peaking around the edge of the field .  Xi Centauri has a visual magnitude of 4.88 and it lies just 17 arc-minutes to the east of NGC 4945 so it may present a light scattering challenge for any scope that is not properly baffled.  It has a stellar classification of A0 V and it radiates about 43 times as much energy as the sun, which at a distance of "only" 221 ly,  makes it visually a fairly bright star in the sky.  Its high surface temperature of 10,462K pushes its peak spectral density into the blue end of the spectrum and since blue light scatters quite well in both the atmosphere and from optical surfaces that are not perfectly smooth, we see a strong blue halo around this star using long exposures.  The blue halo is also almost certainly enhanced by the color correction of the field flattener optics in my telescope.  Either way, I could have cropped this image to minimize the halo, but I liked the effect of having this bright star peaking around the edge of the sensor so I left it in.

NGC 4945 (aka Caldwell 83) is an edge on barred spiral with a visual magnitude of 9.3.  It is relatively nearby at a distance of only 11.7 Mly so it is quite large in the sky subtending about 20' x 4'.  It is a Seyfert galaxy with an energetic super massive back hole at its core.  It is thought to be a galaxy with a morphology and size similar to the Milky Way.  The color of this galaxy does not follow the common distribution of colors one might expect from stellar evolution models.  That may because the galaxy appears in a region of the sky with a relatively high extinction value (0.10), which may result in interstellar dust scattering blue light away from the light that we receive.  I don't know for sure if that's the case so this is pure speculation on my part.  Either way, this is a large galaxy with a lot of interesting details so its a great target for S. Hemisphere imagers!

I started this imaging project after visiting the observatory to repair and tune up my telescope.  Here's a quick review of some of what I did while I was there:  First, I removed the QHY600M camera that started failing late last summer.  I took a Moravian C1x61000 with me as a replacement but Moravian changed their design and failed to include an adapter with the camera so my custom made adapter wouldn't fit.  They insisted that the adapter had been shipped but we had to conclude that it was lost in customs because it sure wasn't with the camera!  I had ordered the camera last November and it finally arrived just over 5 months later--literally  just one hour before my flight to Chile departed.  So I didn't have any opportunity to check it out before I left.  Fortunately, I had the foresight to order yet another QHY600M in case the Moravian didn't arrive--so that's the camera that is now on the scope.  QHYCCD kindly agreed to fix the broken camera under warranty so I'll eventually have multiple backup cameras on site.  This camera problem cost me nearly 6 months of headaches along with a lot of lost imaging time and I really don't want that to happen again.

The next thing that I did was to realign the mount to the pole.  The PW4 software showed the PA to be about 1' 40" off in each direction but I couldn't go for more than 2-3 minutes unguided before getting trailed stars.  So I used a Pole Master to realign the scope and we got it really close.  The observatory techs had never used a Pole Master and they were so impressed with how easy and quick it was, that Obstech now has their own Pole Master that they will use going forward.  The strange thing is that we had to turn the screws on the mount quite a bit before we got it aligned.  It had been misaligned WAY more than what the PW4 software reported!  After running a dense sky model, the image below show what PW4 now reports for my PA alignment.  I don't know if the numbers are right but at least the scope can now easily produce nice round stars using 5 minute unguided exposures.  (To be clear, 5 minutes was just the limit of my test.).



Kevin Ivarsen at Planewave kindly spent two days custom tuning my L500 mount.  I had had a LOT of trouble getting the mount to tune properly ever since it arrived in Chile so it was a big deal to finally get the mount working properly!

I installed a new ASI1600 (uncooled) guide camera and tightened the entire auto guider assembly to make sure that it is now absolutely rock solid.  I then spent a couple of hours cleaning all of the optics including the primary mirror, the secondary mirror, and the front surface of the field flatteners optics.  When I was finished, the optics looked better than when I first received them from Planewave (if you don't recall,  they delivered this scope to me with absolutely filthy optics.). My big concern with all the filth on the mirrors shows up in this image.  A little dust doesn't cause much harm but when it gets really dense, light scatter becomes a significant problem.   Scatter creates halos and it can increase FWHM values a bit as well.

After all of my work, I'm still getting pretty low yield out of this scope so I'm still investigating why my imaging runs wind up with so much really poor data.  Frankly this scope doesn't produce much better results than my old C14 did out at DSW.  I won't bore everyone with all the other stuff that I've done to tune up this scope but I'm not yet convinced that I have everything totally under control.  For this image, I set the FWHM and Eccentricity thresholds pretty high and the yields ranged from 20% - 30% over the 4 channels.  I took a LOT of data to create this mage and here's what the FWHM distributions look like.  The seeing monitor isn't always online but it often reports seeing in the range of 1" to 1.5" so I find it perplexing that I often see subs with FWHM greater than 3"--sometimes reaching 4".  I've been in some discussions with @Wei-Hao Wang  lately and he pointed out that my best subs don't correlate well time-wise, which may indicate that something else might be happening to blur the images.  I also often seen double imaging as if the wind were blowing, which is surprising given that this site is generally nearly windless at night.  So, I suspect that something else might be going on.  My general feeling is that this scope in this location should be producing higher yields and tighter star images.  I should mention that very short exposures do produce very tight star images so it's not the optics (which have been tuned up using SkyWave).  My current three prime suspects are:  local seeing in the vicinity of my scope, a pier issue (like the pier touching the observatory structure), or some other strange mount related tuning/performance problem.




This image was color calibrated using SCC and BXT was used to provide deconvolution.  SCC tends to leave a bit too much green for my taste and shifts blue more toward cyan than I like so I've tweaked the color balance just a bit to fix that stuff.  I've noticed that correctly setting the star detection parameters is very important if you want to get the best results from this tool.  I should also add that the same thing is super important for using the SubFrameSelector to measure FWHM values.  It can give totally screwy results if the star selection parameters are not correctly set.  You should always cross check measured values against the FWHMEccnetricity tool to make sure that both tools produce similar results using a few sample images.  I didn't apply any NR to this data so what you see here is what came straight out of the camera and the data stack.  Be sure to zoom in and and take a look around.  This is a pretty interesting galaxy with a lot of interesting details.  I uploaded the data at full resolution so the best view is on the full-screen display; not at the pixel level (it's just too tight).  If you look carefully, there are also some very interesting small galaxies in the background.

As usual, I'm happy to hear feedback so feel free to let me know what you think of the image...or anything else.

John