First Pass at the Veil Mosaic

I finally had enough data to make a very flawed Veil mosaic. Here it is at 1/5 scale:

Click for 1/5 scale image

And here is the link to download the full-scale image. You can use the cloud site's .jpg to look at it, but I suggest you use your own image viewer. Minor advisory, this is a large image, about 10K by 10K pixels and the file size is 12.5Mb.

You should immediately see some interesting things in the full image, some of which I'll detail here. I'll start with the major flaws (all the images below are at full scale if you click on them).

1) What's the big circular thing?

Bad Flat!

This is in the upper left mosaic panel, and results from improper calibration (using an outdated flat, rookie mistake.)

2) What's all that noise?

So Noisy!

Again in the upper left mosaic panel and comes from not only the poor calibration but also insufficient data.

3) What's with all the black pixels?

Pepper Spray

This is found in the upper and middle left panel; it results from pushing the panel a little too aggressively in one post-processing stage.

4) That green thing can't possibly be right!

Streaks to Left of Center: Not Really Green!

So far as I know there aren't any green nebulae. For reasons I don't understand this feature shows up rather strongly in the green channel compared to the red and blue channels; it's quite strong in luminance. I've seen one other LRGB image of this area, and it didn't have these green bits, so I must conclude something in my processing is at fault here.

The Dastardly 52 Cygni

There was one other flaw I had to skate around. I used the script Star Reduction from Blanshan and Cranfield to perform star reduction. It requires a starless image; this can be made either using StarXTerminator (aka SXT) or StarNet2. I used SXT, and it had a lot of difficulty with Magnitude 4.2 52 Cygni (see above image). It essentially suppressed the northern end of NGC 6960! So I switched over to StarNet2 and it handled things fine. 

Notice that StarNet2 didn't handle it 100% cleanly either, giving it what look like (but aren't) diffraction spikes. Looks kind of cool, I think, but then I grew up as a Newt user.

Now for some positives:

1) No seams. I used Photometric Mosaic, and not only didn't it produce seams, but it avoided the pinched stars that GradientMergeMosaic plagues me with. 

2) Color calibration by SpectrophotometricColorCalibration (SPCC). I can't say enough positive about SPCC. My old workflow made color correction very fiddly, with the result depending on how I felt the day of processing more than any sort of objective measure.

3) Not narrowband. For good reason the Veil is usually imaged in narrowband, but that results in false colors. It's nice to see things more as they "really" are (aside from a Green nebula).

4) Not oversaturated. In my opinion oversaturation is very common now. I've said before that a guiding principle of processing should be that less is more; this idea applies to sharpening, stretching, and also color enhancement. I did bump this a half step using ColorSaturation, but pushing it further seemed like too much of a good thing.

5) Reasonably sharp. Here's a neat feature at the south end of of the East Veil. This looks good thanks mainly to BlurXTerminator (BXT). In fact, aside from the one issue seen in SXT, I think the triad of BXT, SXT, and NoiseXTerminator (NXT) is difficult to beat.

An Optical Spiral That's Probably Not a Real Spiral

   

I suspect this curly-thing at center is nothing more than an undulation in a plane seen edgeways, but it does look fun.

So, with those issues listed above this thing obviously isn't done yet. The other night I shot additional light frames for the two panels that suffered from noise (along with same-night flat frames), and I think I can make sure that pepper spray of black pixels can be avoided.

This means doing much the processing over again, but that's life.

Iowa Star Party Imaging

I'm back from the Iowa Star Party! This is held each year at Whiterock Conservency; the observing field is located about five miles southeast of Coon Rapids, and 60 miles from the center of Des Moines.

2024 ISP had some differences from my previous attendances:

• This year's October party was much more pleasant than the steam baths provided by the usual summer dates. Every night had nice cool sleeping weather for us tenters
• The usual evening banquet wasn't prepared on-site and served in the picnic area; instead it was catered and held indoors at the very comfortable Bur Oak Visitor center. It was moved to lunchtime so that it wouldn't interfere with public night. The earlier time also allowed us to be at the field well before dark
• The field was in great shape, and the addition of a modern bathroom / shower facility was very welcome. I had the distinction of setting up farthest from the bathroom, so it was easy for me to get my daily steps in!
• Saturday night was clear, but the high winds during the day put a lot of dust in the air and really enhanced the brightness of local light domes, which have grown much more prominent in recent years. The low, very dark southern horizon may be thing of the past

But let's get to the imaging.

Friday night I was all set up, polar aligned, and ready. First target was Panel2 of my Veil Nebula mosaic, and the scope was doing its slew, center, and rotate thing. But it never finished because something was causing it to throw errors related to the mount control. 

The usual power cycling didn't clear it. What followed was several hours of swapping cables in and out and trying every other remedy I could imagine. Eventually I started to get the sense that the problem was my Pegasus Powerbox, so I recabled everything to remove it from the USB data flow (it remained acting as a 12V power hub, though). This worked, but it left me with no way to power and control my dew straps. Thank goodness it was as dry as it was, dew prevention was not needed that night or the next. 

To confirm where the fault was, I ran a USB cable to the Powerbox but did not connect anything to its output USB ports. The same errors returned suggesting that simply having the Powerbox as an active USB device was enough to cause the problem. 

I've read that the Powerbox can be harmed by connecting a 12V input line to its Adjustable Voltage port, and I know I've done that at least once recently. The poor Powerbox may have run afoul of Stupid User Error and had finally given out at ISP. Bummer. 

Anyway, I was up and running again and was able to collect light frames for my Veil mosaic.  I got everything I needed for Panel 2 Friday night, along with luminance for Panel 3 and a full set of flat frames. Saturday night I collected RGB for panel 3, along with some frames for the odd object seen in Panel 6 data.

Here is the Panel 2 LRGB result (click to see 1/4 scale version):

Panel 2 (NGC 6974, 6979, Pickering's Triangle, and the northern tip of NGC 6960)

Here is Panel 3: 

Panel 3 (NGC 6995, IC1340, and the Southern Knot) 

I've started to work on the full mosaic and noticed that my Panel 1 luminance frames were badly flatted and need to be reshot. If I can manage that this week, next time I'll have a first attempt at the full Mosaic!