Yes, it’s time for galaxy season again! Last nights learning experience yielded a rather beautiful field — filled with a whole suite of galaxies! Dominating the center of this field is NGC 5033, located in Canes Venatici, a small constellation right under Ursa Major. If you look carefully at the full frame, you’ll notice an asteroid happily trucking along to the left of NGC 5033. Way off to the right is a an odd duckling, NGC 5002. Super tiny PCG 2085892 lay slight above and to the right of the midpoint of these two.
This image was captured with the SBIG STL 11000, with 60x15x15x15 LRGB. The AO-L was running around 2.5 Hz and the Optec TCFSi was used for focusing. By the way, this setup, with Stellarium, enables fully automated remote imaging so long as you can remote desktop (VNC is my case) to a computer running it all. Despite the preponderance of stars in the field, it took some serious finesse to actually get one to come into the OAG!
However, the night was not without frustration. For the second time now, I’ve plugged in my SSAG’s autoguiding cable into the SBIG camera and autoguiding port on the CGE Pro. This doesn’t work! One must use the cable provided by SBIG (presumably the pins are wired differently). However, instead of obvious errors, it merely doesn’t guide. Of course, the AO-L enables great guiding without mount controls but eventually the tip-tilt prism is tipped and tilted as far as it can go! Furthermore, this tends to confuse Stellarium and the scope will enter “drift mode” where it simply starts moving in some direction very slowly (as if it were being autoguided in one direction continuously).
After a few hours, the secondary mirror on the AT10RC decided to dew up. Dew is an insidious beast because it’s easy to confuse with soft focus. Hairdryers are great cures, but next time I’ll be sure to bring out a heater strip for the secondary. Unfortunately with the open tube of the AT10RC, it’s difficult to get the hairdryer in place to be able to de-dew the secondary without also sticking your hand in there to redirect airflow (and burn yourself in the process).
The TCFSi also was actually very weird. On previous nights I’ve used a compression band to hold in my camera. However, as the camera’s are getting heavy these bands tend to not hold well. I use a bungie cord to keep things together but it doesn’t prevent slip and rotation very well. Since a “close call camera drop” a few months back, I’ve since moved to dovetails and am quickly appreciating their incredible rigidity. But imagine my surprise when the TCFSi started at 9280 steps @ 6.4C, racked way in to 9160 @ 5.8C but then only down to 9140 @ 4.2C. Later in the night when it was nearly 2C, I racked it back OUT to 9230. I can’t explain any of this other than to speculate it may have been related to overall equipment cooldown issues.
Last, but not least, processing these LRGB images is still turning out to be a challenge. Like most things, the more often you do it, the easier it gets… First, it’s been awhile since my darks were built so the first pass put tons of holes into the images. I redid the darks and moved over to bad pixel maps (I don’t know why anyone uses darks anymore). And, despite retaking flats, there are still a few donuts. Furthrmore, there was a massive gradient across the field in chromatic ugliness! Gratuitous applications of GradientXTerminator brought these under control even though they wre not completely eliminated.
The whole “1×1″ luminosity and “2×2″ RGB thing is getting a bit easier to handle now. Previously I was bouncing back and forth between photoshop and nebulosity to get these images together but as it turns out, nebulosity has a “scale” feature under the “image” tab which allows you to scale up these RGB’s and then perform the final save-each-file alignment. Then it’s very simple to use the LRGB color synthesis tool to get the image ready for photoshop.
So, what’s your LRGB process look like? What software do you use, what order to do apply what transforms? Let us know!