Every once in a while, I realize that my technique and equipment has improved enough that I ought to reshoot a subject. In this case, it was Messier 33. Previous data of this object was used as the basis of my PixInsight Tutorial. This is four hours of RGB data binned 1x1. Luminosity was extracted from the RGB data with a ratio of 1:1:1.
I wanted to see what would happen if I used 20m Ha subs instead of the 10m subs on the Dragon Head. I ended up using them both. I also gather additonal SII data so that now has 8 subs. Total Integration time is now 10.8 hours. The additional subs definitely made a positive difference.
As mentioned in my last blog entry, "The Value of Darks", I was able to gather some more data on the Dragon Head, IC 1340 before clouds rolled in. All told, I added 3 more HA and OIII subs and was able to gather 3 SII subs as well. This brought the total to 9 HA subs of 10m each, 9 OIII subs of 20m each, and 3 SII subs. Getting the HA and OIII subs up to 9 a piece was good because it meant I was able to use Winsorized Sigma Clipping instead of Percentile Clipping. Unfortunately with only 3 subs of SII, I still needed to use Percentile Clipping for that Channel. Total integration time is now up to 5.5 hours.
I processed the data, this time using darks, bias, and flats for everything. I also used the Hubble Palette since I now had SII data. SII was assigned to red, Ha was assigned to green, and OIII was assigned to blue. The extra data and better calibration processing helped bring out some fainter nebulosity that was not visible in the Bi-Color image. I need to get more SII data but this is coming along quite nicely.
As before, tone mapping techniques were used.
I have been not using darks lately, other than to establish a bad pixel map (cosmetic correction in PI). I just wasn't sure there was any value in them other than finding those bad pixels. Between dithering and the cosmetic correction, I thought any remaining problems were down in the noise (so to speak).
In my latest image with IC 1340, the dragon head, I noticed a very faint band. I haven't noticed this before, probably because I haven't been using such narrow band filters. But it was clearly there. When I checked my bias frame, nothing was showing in that location. But when I checked a long exposure dark frame, sure enough, the band was there.
I decided when processing some additional data I gathered last night to try processing with and without a dark and see what happened. Sure enough, the dark removed the band. I'll be using them again, at least for this narrow band work.
First the image processed without a dark. Notice the very slight band just to the left of the left portion of the nebulosity.
Second, the Image using Darks in addition to the Bias and Flats used in processing the first image.
The Southern portion of the Eastern Veil Nebula reminds me of a dragon head. I've wanted to capture the Veil for sometime, but it is best as a narrow band target. Since my field of view with the AT8RC is small compared to the Veil, I needed to pick a portion of it and the Dragon Head was beckoning (this portion of the Veil is called IC 1340).
Since my OIII data from the Pelican, IC 5070 was quite faint, I decided to up my OIII subs to 20m (binned 2x2). This turned out well, but such long subs were no where near as necessary since this target turns out to be very bright in OIII.
Unfortunately, as sometimes happens with my OAG, after the Meridian Flip, PHD was unable to get the guiding going again. I woke up around 4 in the morning to discover this and at that point it was too late.
Still I got 6 HA subs of 10m a piece, and 6 OIII subs of 20m. So total integration time is 3 hours.
This was processed as a bi-color image with the HA assigned to Red and the OIII assigned to Green and Blue. Tone mapping techniques were used.
My new Astrodon 3nm OIII and SII filters arrived yesterday. Installing that precious hardware just about had me holding my breath.
In my alternate universe, the skies are always clear after I get new Astro gear. Sure enough, the skies cooperated. I had a hard time deciding on a target but ended up going after IC 5070, the Pelican Nebula because I knew it was fairly bright, at least in Ha. As it turns out, it is a LOT less bright in OIII and SII. In particular, there isn't a whole lot of Oxygen.
Here is the resultant image:
Sunday night, Aug 10th was a much ballyhooed Super Moon. It was closer to us than average and therefore slightly larger than normal and particularly bright. I didn't pay much attention to it but I should have. I imaged Sharpless 2-115. Normally, I don't have trouble imaging in HA regardless of the phase of the Moon. But I ended up with very significant gradients. That combined with the dimness of SH 2-115 led to trouble processing.
I ended up stacking before and after the meridian flip separately (since the gradients were opposite). Then I applied the DBE tool in PixInsight to them separately to get rid of the gradients. Then I stacked the results together. Processing then proceeded as normal. It was more trouble but at least it did the trick.
This one reminds me a bit of a brain with the various folds. The embedded cluster in the middle left is Berkeley 90.
On July 30th, the Moon was not much of a factor and I decided to go after a reflection nebula. IC 5076 is definitely on the more obscure side of things but it is located in Cygnus near the North America Nebula, NGC 7000, and so is well placed this time of year. In the same field is NGC 6991, an open star cluster that is rather poorly separated from the field. I ended up with an hour of luminosity data, and a total of 4.5 hours of RGB data (90 minutes in each channel).
Since this isn't imaged very often, it doesn't have a common name that I am aware of. But to me, it looks like a swallow because of the subtly split tail of the nebula. Hey, someone has to name these things!
NGC 6991 is centered to the left of the nebulosity and includes the area where IC 5076 is located. There are two distance measurements given in Simbad, one for 700 parsecs, and the other for 1400.
IC 5076 is thought to be some 5700 light years distant (1750 parsecs) according to Wikipedia. The bright star located within that is causing it to shine is HD 199478, a variable star that varies between magnitude 5.65 to 5.84.
I imaged Messier 29 on Tuesday night, July 29th, but only got around to processing it on Saturday. The pattern of its stars have been described as a small dipper or as a cooling tower. To me the later description is closer to the mark. It is embedded in faint emission nebulosity and I wanted to pick that up so I used RGB and HA.
Here are my occasional thoughts on Astrophotography, Astronomy, and whatever else catches my attention.