The Start of a Mosaic

It's been kind of wild since the last post. We've had many days of air quality alerts, most of which have been for excessive surface ozone, a byproduct of smoke and sunlight and "normal" air pollution. Smoke at times thickened to concentrations similar to what was seen earlier on the East Coast. It wasn't healthy at all; hospitals reported a surge of people with breathing difficulty.

The air quality did improve for a bit and I was able to get out and do a little imaging. In fact, I managed to start one of my learning projects!

One item on my to-image list is a mosaic of the Veil Nebula that spans both the east and west sides. The Veil isn't immense like Barnard's Loop, but it's large enough to require something like a 250mm lens to fit it all in a single frame. My FSQ-106 has a focal length of 530mm and it really needs something like a 2x3 mosaic to encompass the Veil. That's 6 frames, and at about 2 hours exposure time for each it will make a good summertime project that could last into September.

Despite the ever-present smoke I was able to collect the data for subframe 1 which includes most of the East Veil (NGC 6992) and the Network Nebula (NGC 6995): left click the image below, then right click the enlarged image and choose "Open Image in New Tab" to see the image at 1/2 scale:

 

 

For fun, here's a try at a starless version using StarNet2 in PixInsight:

 

This is LRGB with all exposures 120s, L = 20 lights, R = 11, G = 12, and B = 12.

I think I dark-clipped this a little in my processing haste, but it will get another processing eventually.  Here it is tucked into its place in the eventual mosaic:

 

6995 is in the overlap area between subframes 1 and 3. The next target will be subframe 3 to complete the Eastern Veil and give me some practice using PixInsight to create a mosaic.

Some other tidbits from this too-rare night of imaging:

• The QHY-5II guide scope was flawless with over two hours of guiding without a single disconnect. It really does need USB3, it seems. 
• Not only that, but tracking errors were limited to 2 frames in 58. A rate of 1 bad frame in 29 is a lot better than the 1 in 6 that I had experienced earlier this year.
  
• NINA's Advanced Sequencer finished subframe 1 and started subframe 3 imaging without any attention on my part. This was the first time I had tried this. I wasn't willing to do another two to 3 hours of imaging so I reluctantly shut it down at that point.
• More NINA: Its mosaic feature is nicely integrated into the Framing Assistant and sets up the Advanced Sequencer for all the subframes with simplicity.
• Even More NINA: If you want to use the Framing Assistant with images while you're someplace without Internet, go to the NINA download page and grab the Offline Sky Map Cache file (2 GB) It replaces the existing cache folder AppData >  Local > NINA > Framing Assistant Cache. Don't forget to change the Framing Assistant Screen's Image Source setting to Offline Sky Map! Incidentally, installing this allows you to zoom out and use Framing Assistant like a (rather strange) planetarium.
• I seem to have gotten the hang of PI Deconvolution. I don't know why it was so temperamental before, but the key seems to be in the Deringing settings. A Global dark of 0.03 to 0.02 seems to work well, with Global bright typically between zero and 1/2 of Global dark.
  

 

Smoke and the June New Moon; A Couple of Things Fixed (maybe)

This week would be a prime time for heading out to Lac qui Parle state park for some dark sky imaging. But there's some serious smoke action ruining that plan. Here's what the smoke looks like from space.

The location of Lac qui Parle State Park is given by the red dot

Fortunately for the health of people in the Dakotas and western Minnesota it's all far above the ground and the air we breathe. 

This is a blue light satellite image from late in the day of 12 June. Both Dakotas are under multiple smoke decks; you can see the layering across western Minnesota where each layer casts a shadow onto the layer beneath it. The eastern edge of the smoke is slowly pushing eastward. 

 I can't say I'm confident this will clear out during the coming new moon weekend of 16-18 June. Western Canada continues to burn.

It's already complicated trying to forecast clouds and adding smoke makes it all the more difficult. Clear or cloudy? Transparent or murky? The decision to travel an hour or more to a dark sky location has become an exercise in nowcasting.

In some ways this is much the same as a cloud deck. It may not be opaque, but the extinction is formidable. In the image below of north central south dakota you can see contrails at flight level casting shadows onto the smoke!

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Two issues may have been resolved last night. The glitchy behavior of my QHY5LII guide camera was absent with the USB cable connected to a USB3 port, and I got a beautiful PHD2 calibration after I turned off the mount's PEC. This has not been a problem in the past, so I wonder if the PEC file become corrupt while it sat unused this winter. It's going to stay off until I have a chance to retrain the mount.

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I've also learned how to use NINA to acquire images for mosaics, and have set up a file to perform a six-panel mosaic of the Veil Nebula. The first two panels will complete the East Veil.

Opening Night, 2023 (M44 & NGC 6823)

Basically, my first attempt at using a state park failed. Not because of the park. It was the weather, of course. And smoke. There's not much advantage to imaging from a dark sky site when the transparency is severely reduced by a layer of heavy smoke. The camping reservations for the May new moon were canceled and I'll try again in June. 

Last night the smoke relented and even though it was a first quarter moon I got some imaging done from the club's Eagle Lake observatory site. There was time for only two targets, M44 and NGC 6823. As expected there were some rough spots, but I think some things were learned, too.

NINA

Nina  had one glitch and one nice feature I was using for the first time.

I could not get NINA's advanced sequencer to accept multiple targets; Trying to add M76 to M44 resulted in two entries for M44. I'm fairly sure I had forgotten some necessary step as this had worked before.

The NINA manual rotator worked wonderfully and let me get the images properly framed by hand. It took only a few adjustments to get within the "good enough" orientation range.

PHD2

I initially had the scope slew due south to the celestial equator for calibration. Under normal circumstances during calibration you'll see PHD nudge the mount first in one direction and then back to the starting point, then do the same along a line perpendicular to the first direction. While doing the second line it wandered a bit before doing as expected. PHD let me know it wasn't happy; at the conclusion of calibration it announced that the calibration was suspect. The mount had been polar aligned, balanced, and so far as I could see no cables were dragging, so it's a mystery to explore next time. 

Evidently the guiding calibration was good enough, as it kept the stars round in most frames.

Periodically guiding would go badly off in both RA and Dec, producing bad stars. I suspect cable snagging, but maybe it's related to the calibration issue? Either way, it's going to be something to look out for next time.

Guide Camera

I started the evening using a QHY5L-II-M guide camera, a finicky little device. Last night it frequently stopped so I swapped it out for my ancient Starshoot Autoguider. The SSAG is not terribly sensitive, but it works!

Past experience with the 5L, powered by the USB connection, suggests it's picky about the input voltage. Last night I connected through one of the convenient USB2 ports on my ASI 2600. Next time it's going to straight to a USB3 port on my Pegasus Powerbox. Maybe that will clean up its act?

Mount balancing

Confession time: While I do always try to balance the mount, I don't generally practice "east heavy" imbalance. That's going to change after last night. Initially with "near-perfect balance" tracking was only so-so. Restarting with the mount rebalanced to be east heavy significantly improved tracking, just as everyone says. If only I would pay attention

Now the images... These are preliminary processing results: neither makes use of deconvolution or sharpening. Both images were acquired the night of first quarter moon, with only about 25 degrees between the moon and M44.

M44

 

M44 is one of those objects that in my opinion is best imaged by a system that gives the stars diffraction spikes. The spikes can provide a sense of separation between the cluster and the field stars that simulates the visual impression this big cluster has in a wide-field scope. I know there's software that can add spikes, but that kind of "artistic" modding is not something I want to do.

[ Details: ASI 2600 mono ccd, Takahashi FSQ-106 @ f/5, 11x60s for each channel of RGB. Image resized to about 20% of full scale. If you look along the lower edge left of center you'll see my master flats from 2022 are obsolete.]

This result suggests that an RGB imaging scheme of 12x60s for each channel may be adequate for quick imaging of bright open clusters, and that 60s exposures are short enough to preserve star color. 

Next is NGC 6823:

 

NGC 6823 (and NGC 6820 if you know where to look)

NGC 6823 is a combination open cluster and bright nebula. The cluster is 7 arcminutes in diameter (about 1/10th the size of M44) so this is a test of what some of the smaller clusters in the Astronomical League's Open Open Cluster list may look like if I use the same camera and optics to image the list.

Can you tell 6823 is in Vulpecula? Look at all the stars, and how those stars are driven to red near-extinction by their light scattering through light years of interstellar gas and dust. 

[There is some confusion around 6823 and 6820, with 6820 often referred to as the emission nebula around 6823 (see The Night Sky Observer's Guide Volume 2, for example). This doesn't agree with the definition of 6820 being a reflection nebula. If you look a plate solve of the 6823 area, you'll see 6820 is centered around a small blue nebula well offset from the cluster of stars within 6823. This is also where SIMBAD puts it. You can barely see it in my much-reduced image as a tiny smudge just outside the upper left quadrant of the emission nebula. My color calibration doesn't get 6820's color correct.]

[ Details: ASI 2600 mono ccd, Takahashi FSQ-106 @ f/5, 21x60s blue + 20x60s green + 19x60s red. Image resized to about 40% of full scale.]

Those light frame counts tell you that I lost 12 frames out of 72. That's 1 frame in 6 and clearly is not adequate.

And what's next? Waiting for a clear night. What I'd like to see is how a full moon affects open cluster imaging. And when it's new moon time again, the boring spring sky will be at least partially replaced by the sky of summer.