I have been neglecting my blog. I know its bad and I feel guilty. I have taken to writing articles for Info Barrel and just could not stop the torrent of writing inspiration I have been having of late (I have no clue why I have been so inspired. It seems like everytime I sit at my computer, I am compelled to write. Maybe this is not such a bad thing lol). So I figured it was about damn time I started doing some updates for my blog. I have been keeping busy since the last observing blog (observing from Gilroy), mostly with imaging from Solstice Canyon in Malibu, and also from suburbia. I will probably do another spotlight on imaging from urban settings now that I have a handle on good objects to image from suburbia, but for now here is my blog on imaging dim fare from Solstice Canyon!
The need for faint photons
"NGC 6960 Western Veil Nebula, Cygnus"
It has been a while coming back to imaging the Veil, but as they say patience is virtue. My successes with imaging dimmer objects over the past couple of months have been very encouraging, so much so I decided to go for objects such as the Helix Nebula (NGC 7293) in Aquarius, the Veil Nebula (Western Veil NGC 6960 and Eastern Veil NGC 6992) and the Crescent Nebula (NGC 6888) in Cygnus. This blog is all about my exploits in bagging these harder objects. Seeing how I have had limited success imaging with the Orion SkyGlow filter and the Meade DSI CCD from light polluted skies, I figured I stand the best chance of success imaging from the darker suburban skies at Solstice Canyon, my usual imaging site. This site, although not the best, does provide sufficiently dark skies for me and my scope to not have to worry about using the SkyGlow filter. Another plus point is that since I am imaging in the canyon, wind is not much of a problem in comparison to imaging from say Mount Pinos and Lockwood Valley. Both the latter offer much darker skies, but due to their elevation (over 8000 feet above sea level), wind is a constant problem, even with subs as short as 30 seconds. Since it was the new moon weekend, I decided there and then that I was going to head out, even with the rather discouraging weather reports. Both weather.com and accuweather.com gave the same prediction, partially clear with clouds covering a good proportion of the skies. Fortunately for me I ignored this and went anyway. Made two trips out to Solstice Canyon since my last blog and both conditions were similar, dismal weather forecast but excellent skies on both trips out. The moral of the story is only trust Clear Sky Chart!
"NGC 6992 Eastern Veil Nebula, Cygnus"
Anyways I stuck to my usual routine on both trips out. Leave home about 9.30pm...get there about 10pm, setup the scope and then start my session by checking the GOTO accuracy. On both trips I had with me my 70mm Travelscope OTA mounted on NexStar GOTO mount. I found this combo to be a killer imaging setup since the views are wider, and I can expose for longer (up to 42 seconds without trailing). The only drawback is I cannot reduce the focal length further as the scope does not come to focus with the Orion 0.5x focal reducer. Oh well no worries there. I can also safely say that the images I am getting with the Meade DSI II OSC are heaps better than what I was getting with the original Meade DSI I. The amp glow on the top right corner seems to be all but eliminated, and the spurious color pixels are kept to a minimum, provided the sensor temperature (Envisage gives you a real time readout...neat!) is at 12 C or lower. With this, I have been systematically re-imaging some of the better and brighter objects that were done previously with the Meade DSI I (among these M8, M20, M22, M4, M11, M16, M17 are you seeing a trend here...yup summertime DSO's before they disappear for another year!). I also did visual on both session and had with me my StarSeeker II 130mm f/5 on the first trip there and the 102mm f/10 refractor on the trip last weekend (24th of October 2014).
The wraiths of the cosmos
"NGC 6888 Crescent Nebula, Cygnus"
Coming back to topic. The main idea for these trips was to bag faint DSO's. I have not been successful in imaging the Eastern and Western Veil in Cygnus. The Eastern portion is much brighter and easier to image in comparison to the Western portion, the bit that goes through 52 Cygni!). I did give these objects a test run from my light polluted playground in Culver City. While the stacked images were swamped with noise (even with stacking of multiple subs), the nebulosity was clearly visible after post processing in PS. Encouraged by this I set out to re-image them from Solstice Canyon. As always the wraith like nebulosity was not visible on single exposures. I collected 20 subs of 30 seconds, both in FITS and TIFF format for stacking later.
Since I was in the Cygnus area, I decided to also shoot for the Crescent Nebula. This is another faint bubble that is borderline visible with narrowband filters visually. Again, much like the Veil Nebula nothing was visible on the single exposures. I took 20 subs of 30 seconds in both file formats to stack and play around with later.
The final dim object on my wish list was the Helix Nebula in Aquarius. This object, while not as dim as the previous objects, presented a challenge as it is a southern object and does not rise very high in the sky from Los Angeles. As such I had to deal with high background and noise, despite taking multiple exposures. Again I did 20 subs at 30 seconds each. I find in general this seems to be sufficient to bring out fainter nebulosity while improving signal to noise.
I also re imaged some of the challenging and fainter (but not as faint as the ones listed above) objects, even from suburbia. Redid M1, the Crab Nebula in Taurus and NGC 2023, the Flame Nebula in Orion. Both only required 15 subs at 30 seconds and were quite pretty with post-processing.
Preserving them for prosperity
"NGC 7293, Helix Planetary Nebula, Aquarius"
Speaking of post-processing, here is the current protocol I use. Open images in MaxIM DL and use the combine function. Select two stars for alignment (here you can discard images that are less than ideal) and then use the built in histogram function to get a decent image (not over exposed). Save the images as 16 bit TIFF images as PS cannot handle FITS (with the FITS images you have to use the combine color function to bring all channels into a single image (R-Red, G-Green, B-Blue, L-Luminence). I do all my post-processing manipulation in PS after doing the initial stacking of subs (6 up to 20 subs depending on object).
In PS, I use mainly the curves function to bring out faint nebulosity. I usually raise the the curve bit by bit. Then I use the Levels function to get the color balance and background to object ratio correct. The final product is then saved as two copies (don't forget to dark subtract too prior to manipulation), one in TIFF format and one in JPEG (to share on FB, Instagram, My Blog, etc.).
I was very pleased with the results I got. Let me know what you think of my images! Next change (hopefully in the next few days), I will explore imaging from light polluted skies. Till then enjoy!
