That particular image was quite the mess. From my light polluted backyard, trying to capture this faint fuzzy dust cloud was a monumental exercise in futility. I gave it a go having failed in the past a couple times. The weather held out and I imaged every clear night I had available during those fall months from September to November. Using such a modest scope and a DSLR I really did not have high hopes but I pushed on.
The data was noisy but had some promising signal. After several months of extracting every photon out of the noise in that image I accomplished something reasonable. I’ve promised myself to revisit this object with a bigger scope and dedicated CCD but haven’t yet had the chance. Perhaps next autumn.
Heres the link to the full image on my Astrobin page-
It’s been a long time since I have updated the site or this blog. Life gets in the way and I haven’t had much time for star-gazing. I did get some action in here and there and the absolute highlight was the total solar eclipse.
Here’s the most recent night shots I’ve been working on or completed-
I’ve also been loading up most of my work on Astrobin these days and here is the link:
I took the family out to Kansas City and met up with my close friend Paul and his family. Clouds projections looked bad for our initial plan of watching the eclipse in Independence, Missouri so we hopped in the car and drove east. Passed through Columbia and had dinner. It was fun seeing that old little college town we had live in back in the late 90’s. It had grown and changed quite a bit but still fun to see.
We continued on to St Louis and spent the night. In the morning we game-planned as I checked in with my meteorology buds. The choice was to continue south toward Kentucky or back west. We decided to head south and got going early. As we trekked southward I kept checking the weather, it looked like our best option was to turn back west. I told my friend Paul, lets at least get in the zone of totality and see what happens. We found a little town- “Leslie” Missouri Right on the main totality line. Looked promising.
We found this home on an open field and the nicest guy you’ll ever meet. He said we could set up on his land. Perfect idyllic spot! He called his family over to join us and we setup a tent and had quite the picnic while setting up and waiting. I had set up the cameras, scope, and Mac running the automation program.
Everything was going well then my Mac running “solar eclipse maestro” crapped around 48% obscured- ? Heat.
Brought it back in and it was acting odd but eventually seemed ok.
Set it back up outside and it worked until eclipse max then crapped out again. Now seems bricked. Won’t restart. Guess I’m going to apple when I get home.
In any event, we set up a table and tent. Sandwiches with Sun Chips and moon pies for dessert.
My friend brought his 8 inch LX200 and we had a couple binoculars.
The home owners grand kids came and had a blast looking through the scope.
Totality was simply amazing. I got so caught up that forgot to take the filter off my scope being run by eclipse maestro. It died at Max eclipse so that was worthless.
I had a second camera canon 6D with a Rokinon 14 taking partials every 5 minutes and at 5 min before totality I took the filter off and had it auto 1 image per sec. That worked out well.
I also had a GoPro set up on the camera’s hot shoe and it captured the scene and all our hollering and excitement.
Luckily Very Luckily!! My friends son and I setup magic lantern’s script on his canon with a 300mm lens. That worked beautifully and saved the day given my macs failure and my forgetting to take off the filter.
We were so lucky to find this spot and meet such a generous and great guy. The clouds were thin and the day turned out great. My daughter is already asking when the next one will be!
….well I had promised to follow up on my my AG Optical iDK 10 inch F/6.7 and its long past due. I received the scope last May and between weather, glitches, day job and life, I have had little time to use it or report back.
As I previously noted, I had ordered the scope after speaking with Dave Tandy back in late 2014. It arrived in May 2015 and I set out to mount it and configure it on my MYT……
-the scope weighs in around 32 pounds. It is sturdy and gorgeous to look at. Even my wife who does not relish my insomnia associated hobby remarked that it looks like a work of art! The carbon fiber charcoal black look contrasts beautifully with the machined red.
-mine was the first 10 inch truss model made and you can see it on AG Optical’s web page. During the time that I ordered it, Dave was not supplying the optical reports that he is now issuing with each scope. I wish I knew what my mirrors strehl is but they seem to be well corrected.
-The MYT required approximately 40 pounds to balance the scope when outfitted with the camera, OAG, and adapters. The mount seems capable but you are close to the limit and I found that for perfect balance I needed the extension bar. My MYT saga is long and protracted and I will not delve on it here. In the end, I ended up upgrading it to an MX+ and now in retrospect this scope is much better suited to a heftier mount such as the MX+.
For those interested in this scope, I am not stating that an MYT or Mach-1 cannot handle it but just be aware you are close to the limits.
So after a frustrating fall of sorting out issues and trailing stars I finally mounted this scope on the MX+ and immediately saw that it was happy on its new home.
I will outline my setup in the next few paragraphs and relate some of my experiences:
The scope is easily lifted by one person using its side dovetail plates. It slides easily onto the versa plate of the MX+. I find that with my setup using a QSI 683 wsg-8 and ST-i auto guider and spacing adapter, that the scope balances easily just slightly forward of center on the versa plate. I still have ample room forward on the versa plate, and in fact the front retaining bolt does not even engage as the dove-tail on the AG Optical is short. The middle and back bolts secure the scope easily and securely. RA balance is easily achieved with about 50 pounds (I use two 20 pound weights all the way up on the counterweight bar and s smaller 10 pounder slightly farther down).
The TCF-S3i focuser is hefty and very solid. you will need some sort of spacing adapter to reach the focus plane which is about 11 inches back. There is a lot of back focus which is good if you plan on adding a rotator and such. I use the Optec large 3 inch spacing adapter which is secured by three large thumbscrews and then attached to my camera with another three thumb screws. This works but you have to be careful to keep everything centered with all the thumbscrews. I will probably have a precise parts adapter made that will thread onto the camera and thus eliminate one thumb screw junction.
I had a Dewbuster made special with some 5.5/2.1mm 12 V ports. It sits on the top dove-tail plate and I plug-in the two dew heaters (primary and secondary) as well as the fan into it. I am mac based so I ordered my scope without the thermal control system and simply rely on the dew buster. The dew buster is powered via powerwerx power pole distributor. This is the small version that has 4 ports. I have a 12 volt line running through the mount that supplies power to this distributor. This in turn supplies 12V to the dew buster and supplies power to my QSI 683. I also have two USB runs through the mount, one for the guider and the other for the camera. I connect the TCF focuser via a small RJ12 cable to the USB port on the versa plate. The focuser is also powered by the 12v port on the versa plate. In the future I will add a rotator that can connect to the other versa plate USB port and draw power from the dew buster.
I connect the two USB lines from the cameras and one from the mount to an Icron Ranger and then run 150 feet of CAT5 from it to my desktop computer inside. I can control everything from the warmth of my home office.
As an aside, the MX+ is actually surprisingly portable given its capacity and heft. It is an easy thing to simply carry it out on my ATS pier from my basement to my patio. I then add the counterweights and scope and proceed to polar align, T-point model, etc. I can leave the setup outside under a tele gizmo cover for weeks on end without issue or change in my polar alignment.
….full disclaimer. This was my own fault and let it serve as a warning for any fellow OCD sufferers out there. PLEASE WAIT UNTIL YOU HAVE AN IMAGE UNDER THE STARS BEFORE YOU MESS WITH THE COLLIMATION!
You will need to unscrew the primary baffle in order to collimate with a laser or tak scope as it prevents a clear look back on the the corrector lens. Use a Tak scope and laser if you like but keep in mind my experiences below…..
When my scope arrived, I set everything up and used my Howie Glatter laser to check the collimation and alignment. Here are a couple of issues….the slip in nature of the laser does not result in a very repeatable position despite a compression ring. Be careful if you use one, that it is not leaning downward due to gravity as you secure it. This was my first mistake….secondly, it is pretty bright and it is difficult to really see if you have the laser falling back on itself (supposedly there is now a dimmer for these lasers, probably something I will pick up at some point).
So with my laser in hand I noticed things seemed off so I decided to center it all up. All looked good until I got out under the stars….my spider vanes now showed a splitting diffraction spike??? I wasn’t sure what was wrong until I spoke with Dave and then made the acquaintance of one great guy Dan Wilson! Dan has become a great friend and I look forward to sharing a drink with him someday. He has been patient and really helped me with a lot of issues. Dave would confess that Dan really knows these scopes. He tinkers with them frequently, and I am sure he has taken them completely apart!
Turns out that when I was re-centering the laser and I adjusted the spider vane centration, I was actually mis-aligning the opposing spider vanes. The fix required carefully measuring the distances until I had them all equal.
With that fixed I went ahead and finished the collimation with my laser but yet my images under the stars were still elongated, particularly in my upper left corner.
Next I resorted to a Tak collimating scope. Using it was fairly easy and I believed everything was lined up; yet when I checked with the laser they now did not agree at all. What was up?? I could not figure it out…no matter what I did the Tak and the laser would not agree and the stars looked worse! Dan to the rescue…he suggested I loosen all the truss rod connections and actually move the ring until I was well centered using the Tak scope. So as scared as I was, I went ahead and did this with the help of my son. He would adjust the ring while I was looking in with the Tak scope and then I would quickly begin tightening while checking with the Tak scope and he holding everything steady. Once secure I now finished collimating with the Tak scope. Now I checked with the laser and things were very close in agreement. Good enough! I would not do another thing until under the stars.
Dan had shared with me a document he was involved with on Collimation. It can be found here:
I studied this carefully and armed with it in hand, my collimation screws labeled and marked, my large 27 inch iMac taken outside I proceeded to start collimating under the skies. I used the SKYX 3D star profiler to look at the energy levels of my out of focus donuts. I also used a little freeware program written by a fellow paramount user that would create concentric circular overlays on the stars. Using these I was able to really see on the iMac the subtle changes I was making to my stars. I started with collimating the primary which needed barely a tweak. Next the secondary..gradually making the appropriate changes as described in that document and then bringing focus tighter. Re-check the primary, then continue to with the secondary until it looked as good as I could get it.
FINALLY! perfectly round stars in all corners. I used pixinsight to measure eccentricity on a 10 second exposure and it was .36!! Success and relief.
MINOR ISSUES REMAINING
I have a few outstanding issues that are not related to the scope. I have noticed occasional internal reflections particularly on the bright stars. Looking at my Flats particularly using an HA filter one can see the internal reflections that appear to be coming from my imaging train. I also have some pretty bad dust motes on the CCD screen.
At Dan’s suggestion I purchased some Rustoleum ultra flat black camouflage paint and painted the inside of my extenders and adapters. I’ve also gone ahead and cleaned my cameras CCD window. The new Flat looks much better…
I will admit that dust has been a problem for me. Dave supplies a shroud and fabric shower caps that cover the secondary and primary baffles as well as the outer ring. Unfortunately when mine was made there was no primary bucket cover. It appears he now includes this with these scopes. I have asked to purchase one for my scope although it will not secure well due to the design of my scope. He has added threads to the primary ring of more recent models so that this cover will fit secured. I will figure out a way to secure it with velcro and hopefully keep the dust off of the primary. It should be here in a few days.
THE REAL FIRST LIGHT
So after all the issues sorted out, a new capable mount underneath, and a couple clear nights in December I finally was able to acquire a few hours first light with this baby. These two images were just 3-4 hours in Ha and will be completed next season but what I have more than pleased me.
Stars were round and crisp, details sharp and contrast great. I’m happy and ready for some good nights of imaging this spring (if the New England clouds and weather ever cooperate).
CONCLUSIONS AND OBSERVATIONS
The scope is a real winner. I am very pleased with the finish, construction, and in particular the light weight. Once my collimation woes were sorted out, I have not needed to touch it again. It has been several months without any change in the appearance of my stars or collimation. This, despite transporting the scope in and out of the house.
I do not have the Temperature compensation module but using a simple dew heater I have not had any issues with dew.
The fans work quite well bringing the scope to ambient quickly. I have noticed that with the fan at anything other than the lowest setting, my guide star really jumps around. Perhaps there are some gradients or tube currents coming across the primary or secondary but in any event setting it to the lowest setting takes care of it.
I use @focus to automate my focus runs. The TCF-S3i works perfectly with it. In fact I have noticed that the focus barely changes despite significant drops in ambient temperature. These scopes are very thermally stable.
Lastly, Dave Tandy has been great. I have emailed him quite a few times and he has always been patient and responsive. He is a great guy and makes a superb product. This 10 inch Truss iDK that he was more than happy to make me even though the design was closed tube at the time, is exactly what I was looking for…. reasonable aperture, relatively fast and very wide imaging circle that I can grow into.
….back in August I dropped off my first born for college. My boy has been my stargazing buddy since the first time we both saw the milky way together in Cape Cod. I still remember that night so long ago. He was a little over 3 years old and I took him out to the beach with me and just lay there looking up at the sky. The milky way blazed above us and I took him through the stories of some of the better know constellations. Over the years he has kept his dad company during meteor showers, eclipses, and just for a few moments of stargazing.
On the night before moving him into the University of Arizona we found ourselves at the Grand Canyon. We spent several hours gazing at the milky way, looking at the summer constellations, and just chatting about life and the start of his college adventure.
I captured a few images that night. My favorite was selected the November 2nd AAPOD. Truly a special photo for me.
Back in December I decided it was time to part with my old 10 inch LX200. It had served me well over the years, but with my increasing interest in astrophotography over the years the short comings of this scope for astro-imaging became more and more apparent. I was in the market for an astrograph but most were out of the budget in terms of price range. The known players that make the various RC models were tempting but the price just too steep.
So as it happens, I was perusing the cloudy nights posts one night and ran across a thread discussing AG Optical Systems imaging Dall-Kirkheims. They were starting to produce a 10 inch model that was much more accessible in terms of price point. The more I looked into this company, their scopes and owner Dave Tandy, the more intrigued I became.
I set out on a plan- First Sell the LX-200 and various other odds and ends to get some of the cash needed. Then a letter to Santa and She whom must be obeyed 😉
I spoke with Dave Tandy and discussed my interest in a 10 inch scope. I was hoping for a truss design and after a few minutes on the phone, Dave agreed that he could make a version as such. The time line was for a February-March Delivery time frame…I put down the deposit and thus began the wait. Dave kept me well informed on the progress and was very helpful as I set out to plan the odds and end needed to configure the scope when it arrived. There were some delays and finally the scope arrived in the middle of May.
The scope came packed in a crate that Dave Tandy makes for his scopes. The scope was well protected in bubble wrap and a few pieces of cardboard were placed to help keep it in place. The packing was utilitarian…it did the job, but things could have been snugger. The scope clearly rolled a bit to each side but no harm appears done. I would suggest to Dave that a Custom piece of Foam in the crate would be preferable. Further, there was significant dust in the crate which did get on the scope as well. Given the high end nature of this scope and its optics….I would further suggest sealing it in a plastic bag prior to placing in the crate.
In any event, unpacking the scope and lifting out of the box was a cinch. The scope is quite light and easily managed. It comes with two dove tail plates and was easily slid into the versa plate on my MYT mount. I was able to do this by myself without any issues (a far cry from the grunts and exertion of mounting the LX200 on a wedge).
The scopes finish is gorgeous, with a deep red contrasting with the carbon fiber black. There are three built in fans with a controller knob on the back of the scope and primary and secondary dew heaters were pre-wired into place. The scope comes with an Optec TCF-3Si focuser but no adapter for 2 inch eyepiece or camera holder.
For now I have mounted it indoors- at least until the pollen season ends. I used a Kendrik power hub velcro’d to the side plate from which to feed power to my dew-controller box that I placed on the upper dove tail plate that in turn will power the dew strips and the fans The focuser will by controlled by the Sky X and powered through the versa plate. I am awaiting a 3 inch to 2 inch adapter from Optec which will allow me to connect my camera. Stay tuned for first light in the weeks to come……
I had one last night of imaging back in late January prior to the onslaught of winter. My backyard is now the “Tundra” with weeks of winter still to come. I went after the M106 area during this last imaging run. My plan was to use my little wide field WO Zenithstar 66 refractor and capture M106 and all of the faint fuzzies which are present in this area of the sky. I had hoped on several nights amounting to 12-18 hours but the blizzard derailed me at 6 hours.
I really did not plan on processing this image yet but with no imaging possible for the foreseeable future I decided to play with what I had. I was quite surprised with the amount of detail this little refractor captured. After a plate solve of the image I determined that I went to about magnitude 19! Thats deeper than I ever thought possible given the aperture and my suburban skies.
I have had several inquiries as to my processing workflow for this image so I decided to post it here. The image processing is a little un-orthodox as will be described below.
Williams Optics Zenithstar 66 Semi APO @ F/4.7
Canon Full Spectrum T3i
Astronomik UV/IR Clipin Filter
Astrophysics Mach One GTO
Guiding with Stellarvue 60mm Finderscope-Costar guider and PHD2
Image Scale: 2.86 arcsec per Pixel
64 x 5 minute exposures at ISO 1600 total of 5.3 hours
Processing in PIXINSIGHT
1. Calibration with SuperBias, Master Dark and Master Flat.
2. Image Integration using Linear Fit method at default values.
At this point I proceeded with my normal workflow which begins with a crop of the edges followed by DBE and Background Neutralization. What I encountered was a dramatic change after DBE resulting in the original very smooth image becoming noisy and difficult to process further. I posted a pixinsight forum topic on this issue (http://pixinsight.com/forum/index.php?topic=8248.0) and received some good advice. Despite this advice however, I continued to have difficulty. I therefore thought to try something a little un-orthodox and forego the DBE step during the linear portion of processing. Rather I proceeded as follows after cropping the edges:
3. Background Neutralization: Upper limit set just above the highest background reading which in this image is approximately 0.08
4. Color Calibration: I set structure detection off, using the galaxy for White reference and an area of background for the Shadows Reference. The Low limit for the white was set just above the noise level and the High limit for the Shadows was set just above this noise level as well ~0.02. I use the output reference masks to make sure the settings are correct.
5. Deconvolution: I create a luminance clone of the image and use the STF settings with Histogram Transformation to stretch it. I create a star mask with large scale set to 3 and the noise threshold set to .25 thereby creating a mask that will only cover the large stars. I do not use the dynamic PSF but rather create it manually in the deconvolution tool by zooming up on my stars and adjusting the deconvolution settings to approximate the star appearance. I apply the luminance mask and create previews. I then experiment with the deringing settings using 20 iterations of deconvolution until I am able to dial in the correct settings for the image. In this image I ended up using 50 iterations with deringing set at 0.008 using the star mask for local support at 0.80.
6. Noise Reduction: After Deconvolution I perform a first pass at noise reduction using TGV through an inverted luminance mask.
7.Histrogram Transformation: I use the HT tool to stretch the image in 3 steps making sure not to clip the shadows.
8. DBE: Here is my un-orthodox step. I used DBE in the non-linear stage carefully placing samples across the background of the entire image and using subtraction. I think it resulted in a much smoother cleaner result.
9. High Dynamic Range Compression: I apply an inverted star mask and use the HDRMT with Median transform selected and to lightness and lightness mask. After experimenting I found that employing the tool at 2 layers followed by a second application at 6 layers provided the best detail development in the galaxy core.
10. Star Control: I now like to use the morphological selection tool as described by Carlos Milovic to obtain some subtle star shrinking. I use the Selection method at 0.2 for selection, 0.1 for the amount and use 7-10 iterations. I set the two ways at 5 elements and a circular and diagonal structure.
Comet C/2014 Q2 Lovejoy has passed perihelion and is now fading as it travels outward on its long period orbit. Its orbit has changed a bit due to the interactions with the inner planets during its recent apparition. It has gone from an 11,000 year orbit to an 8000 year orbit. Makes you wonder who and what will be during its next visit…
In any event, this was a beauty of a comet, the best I can recall in years. I had a few opportunities to image it during the last few weeks….despite the clouds, snow, ice, and frigid temperatures always conspiring against me!
Now with it fading and the full moon approaching there will most likely be no further opportunities.
I went ahead and processed my final data run. This has been a difficult comet to image. Yes it is bright and shows up easily on short exposures. But its long tail against the backdrop of stars posed a difficult problem in terms of combining images using the star freeze technique.
No matter how aggressive my sigma clipping algorithm there would always be star trail ghosts. I’ve settled on a new process ….kinda….still needs some tweaking but this is what I did:
1.Calibrate the subs using Bias, Darks, and flats.
2.Star Align and integrate to obtain an image of sharp stars and blurred comet.
3.Comet Align and integrate to obtain an image of sharp comet and few residual stars. I used sigma clip in Pixinight with a high setting of 0.05 and low of 1.0
4. I then created a clipped luminance mask for the comet only image and applied it inverted. Then using morphological median with a diagonal structure I ran 7 iterations with amount set to 0.3. This removes some of the ghost trails.
5. I then use convolution to further blur the background of the ghost trails.
6. Clone stamp any residua
7. Then regarding the sharp star image-it was difficult to remove the blurred comet. I gave up and thought to myself I only really need the stars so why not just use two consecutive images which will show the stars and the comet both sharply. Yes they will be noisier but it might work.
8.I took the sharp stars and comet image made up of two consecutive 2 minute exposures and applied MLT for noise reduction, then DBE, Background Neutralization, Color calibration and a deconvolution.
9.I did a linear fit between the stars/comet and comet only image.
10. Histogram transformation to each but using the same parameters.
11.Using the lighten blending I combined the two images.
12.Futher noise reduction, resetting black point, Local Histogram equalization, and final exponential stretch. Reset the black point and increase saturation with a lum mask.
Here’s the final image. I’m pretty happy with it at low resolution but if you blow it up you will see artifacts and noise. I think this process might work but it needs more tweaking.
Wednesday night….home from work….clouds parting. Quick check of the scope nights app and YES! Its going to be clear!
oh oh…..9 degrees F….I pause. oh what the hell, just bundle up right? 😉
So out I go at twilight. Take mount outside….line up approximately north. Rough daytime polar alignment routine. Mount scope, counterweights, camera, guider, balance….dark approaches.
Start up laptop, connect PHD, Nebulosity, Sky safari…..polar alignment routine. I get close….close enough…Ok go to Deneb, sync mount, focus camera, focus guider, start guiding routine.
All check….meanwhile… I realize I don’t feel my toes and fingers anymore…..ok just a few minutes more. 😐
I shoot my flats, then slew to comet. Quick 30 second shot…yes…good bright sweet comet! Ok…nudge the framing….just right….ready….start sequence. Two minute exposures and track on stars.
Head inside to the looks of my family….”your nuts” they say….why are you out there in this cold?!!
There’s a comet to be had!! 😉
After thawing a bit and grabbing some soup, I find some hand and toe warmers. Bundle up with the big parka and head back out. All is good, I have 20 two-minute exposures. Next I try to shoot with guiding on the comet for a potential movie…
All goes well and its 11:30pm so I go shut everything down. Damn its so cold the computer is sluggish, the track pad won’t work and my Mach 1 GTO Hand-controller is unresponsive. I disconnect it and bring it inside for a few minutes. That does the trick, when I reconnect I am now able to park the mount and finish shutting down and call it a night.
…well the new england weather pattern of clouds, rain, freezing drizzle, snow, bitter cold continues. No chances to image in weeks…what to do? Well I had some incomplete data on NGC 7822 that I have been accumulating.
I shot about 2 hours worth through an Ha filter back in late summer. I was using my old Canon 1000D which was astro-modified. The results seemed reasonable until I compared it to the new data obtained with my much quieter Canon T3i which was full spectrum modified.
Heres the original quick look of the Ha data. No processing other than a quick stretch:
….there’s a strange banding pattern seen. This is known to occur with some DSLR images when the Darks and Light subs don’t match well. Further, using the noisy camera at 10 minute exposures and not dithering makes it much worse.
I gave some thought to this and also considered the fact that the images were being shot through an Ha filter. This essentially restricts the data to the R photo sites on the chip. So whats going on in the Blue and Green? Nothing….just noise.
So if you consider that I am shooting light subs and flats through this filter, and calibrating with Bias, flats, and Darks that contain all channels….I may be injecting noise into the other channels. I decided to do an experiment and proceed with stripping out the CFA0 channel (Red Pixels) from the light frames, Bias, Dark and Flats. I created new Master calibration frames using only the CFA0 channels. I then calibrated the CFA0 light subs with the CFA0 only Master BIAS, MasterDark and MasterFlat.
The Result was quite startling. Much of the peculiar banding noise was suppressed. The image is still noisy but much improved. Here is a panel analysis of both methods. Pay particular attention to the upper corner panels. Much smoother wouldn’t you agree?
So what about OIII data?
I gave this some thought and had some discussions online with the DSLR image processing group and Pixinsight forums. I decided to again use the Extract CFA process in pixinsight and split out the channels. This time I used the CFA1, CFA2 (green) and CFA3 (blue) channels and threw out the CFA0 (red).
I made master Calibration frames for each and then calibrated each set of CFA channels from the light subs using their appropriate CFA master. I then proceeded to align and integrate them all together as if they were monochromatic images and create a final OIII image of blended blue and green channels given that OIII is truly in between these two wavelengths.
Alternatively ( I have not done this yet but will probably try it) I could have integrated all CFA1’s, CFA2’s and CFA3’s separately and then recombine them using the Combine CFA process in pixinsight to create the final OIII.
Honestly, I am not sure there would be a difference or what is more scientifically sound.
So after doing this, I also processed the OIII data the way I used to without isolating the cfa channels. By this I mean:
1.Calibrate OIII exposures with a Master Bias, Master Dark, and Master Flat (shot through the OIII filter).
2. Debayer using Superpixel method so as not to pollute the G and B channels with noise from R.
3. Extract G and B channels
4. Register G and B channels
5. Integrate G and B channels together and create final OIII image.
The difference this time was not visually discernible. I measured the noise using the Pixinsight script and the difference was negligible but in favor of the first method using the CFA channels.
Why? Two reasons I think. First, I shot the OIII data with a Full Spectrum Canon T3i which is significantly quieter. Further, this data was obtained at 20 degrees F where as the Ha data was obtained in the summer at 70 degrees F. Secondly, I dithered the OIII exposures which is known to significantly improve noise in DSLR images.
I have obtained some SII data on this object using the Canon T3i and it is equally smoother and quieter than the Ha data.
Thus far I have 120 minutes of Ha, 270 minutes of OIII, and 170 minutes of SII. I clearly need more SII data, and I think I am going to re-shoot the Ha data with the quieter camera.
Here’s a stab at Hubble Palette (R=SII, G= HA, B= OIII) with what I have thus far. The Noisy Ha data is coming through but all in all I am satisfied given the lack of data thus far.
….clearly I need more SII data.
In any event I kept playing with the data and other palettes. I finally settled on a more natural appearing palette based on HOO. I used 80% Ha and 20 % SII for the Red channel, 100% OIII for the Green and 80% OIII with 20% HA for the Blue channel. Using this I am representing the SII and Ha in its appropriate Red wavelength and by adding HA to the Blue channel I am getting some H beta representation.
Heres the final image using that palette and more noise reduction and processing.