Integrated Flux Nebula Mini-Test Result

 Let's get right to the image:

Polaris IFN luminance trial

The total exposure was a scant 1.8 hours (72 x 90 s). NINA ran the acquisition and PixInsight handled the processing. Flat frames were used. The nonlinear stretch was the PI Screen Transfer function and no attempt was made to enhance contrast beyond what it provided.

This is so far beyond my expectations that I don't know what to write. It was a not-very-dark site, the moon was at first quarter high in the ecliptic between Cancer and Leo, and there was a thin layer of smoke aloft. I really didn't expect to get much if any nebulosity in the image. But there it is.

The night's goal was to fully test the imaging setup and perhaps answer a few questions:

• Would go-to compose the image reliably? I started it once, collected a dozen frames, shut it all down, parked the scope and did the entire startup again. Plate solving shows the center changed by 67.5 seconds in RA and 7 seconds in Dec. Translating the RA difference to arcseconds at the equator, it's actually more like 27 arc seconds. That's total shift of about 28 arcseconds. The difference in image axis rotation is also tiny, about 0.11 degrees. So the answer is Yes, go-to works very well!
• Would guiding work so close to the pole? I had made some changes in PHD2--activating multi-star guiding and predictive PEC, and using the calibration assistant to make sure that was done optimally. Through the evening it collected 72 light frames, and only one had to be rejected (when PHD2 timed out after a dither). Tracking was next to perfect. I'm nor sure the ASI 2600 benefits much from dithering, so I'll disable it.
• Some people have indicated issues with field rotation when guiding near a celestial pole. I saw no sign of that. Possibly the excellent polar alignment from PoleMaster should get credit for this.

I do like the composition of the image, with Polaris shifted off center northward and looking as if it's shining light down onto the nebulosity. It's nice to see that the offset doesn't produce any significant internal reflection.

There are issues with this image, though. Although ASTAP reports moderate tilt I don't see any evidence of it. (Maybe it's some sort of algorithmic issue?) There are a lot of vertical bands in this that snuck in during the processing. I'll have to find a way to make sure to avoid them. [EDIT 12 May: see the reprocessed image here.]

PHD2 was doing something that seemed odd. Every now and then it would make a too-large declination adjustment and then follow that with smaller corrections. This may also have been my fault as I had the wrong guide scope focal length entered. This has been corrected, so I'll see if that takes care of the issue. 

Tonight I'll be out again to test my RGB acquisition scheme. Basically, I'll try the good old 3:1:1:1 channel ratio, meaning 24 frames for each color channel. How will the colors turn out?

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!

---------------

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.

---------------

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.

Backfocus & Hocus Focus (a NINA plugin) and a New Image

Backfocus

When I first heard about the focusing plugin Hocus Focus (HF) I was unsure if it was something I wanted. NINA's built-in autofocus seemed to work perfectly. Then I watched one of the Patriot Astronomy videos that demonstrated what else HF can do and I realized I not only wanted it, but I needed it!

HF (created by George Hilios) features what he calls Aberration Inspector. Much of what it does is beyond my ability to intepret meaningfully, much less act on. But it has one key ability: to measure error in backfocus. Having proper backfocus is a problem when using focal reducers.

If the backfocus isn't right, you won't be in focus across the field; if you focus on stars at the field's center, stars in the corners will be out of focus. This is why an old fix for this problem is to focus on stars some distance out from the center. Like most compromises it's hardly a perfect solution: stars in the center and corners will be slightly out of focus.

The better remedy is to get the backfocus as close to correct as possible. Usually this means taking images, examining them closely, guessing the distance of the correction to make, making the correction, then shooting more images, etc. It's time consuming and inexact. Fortunately there's a better way--use Hocus Focus.

HF can quickly estimate the magnitude and direction of your backfocus error during a special autofocus session. Then you can make the correction if you have the proper spacers on hand. And you're done.

I have a Takahashi CR 0.73X reducer That I want to use with my FSQ-106. The CR wants a backfocus of 72.2mm. My camera and filter wheel add to 32.5mm, so I need my adapters to provide 39.7mm.

For my first run of the Aberration Inspector I had this:

• M56 to M48 adapter, 12.1mm
  
• M48 to M42 adapter, 16.5mm
  
• M42 spacer ring, 10mm

These add to 38.6mm. Close, but 1.1mm too small. The Inspector told me I needed to add 3 focuser steps to the backfocus, which is the right sense of change, but the magnitude seems off. 

One of my focuser's steps is about 0.004mm (30mm/8000steps), so 3 steps is a mere 0.012mm. My assumption is that somewhere in how I set up NINA or HF a factor of 100 error sneaked in. If that's correct, then the correction it's suggesting is to add 1.2mm.

So I added two thin spacers totaling 1.2mm and ran the inspector again. Here is the result 

As you can see (if you click the image to enlarge it), the Inspector now says the error is zero steps and the difference in star quality between center and corners is almost imperceptible. I think it's safe to say that I'm now within 0.1mm of having correct backfocus!

This means the next clear night I'm going for a larger target, maybe the Elephant's Trunk, M31, or the entire Veil!

Some incidentals for those of you who like miscellaneous information...

• All of the goodness of fit (R squared) values were 1.00
• This was performed without polar alignment or guiding, the exposure time was 2s through my luminance filter
  
• I had to increase the autofocus backlash from 450 to 600 steps. I should probably redo all my filter offsets, too, if only to see if they have changed. The autofocus step size was unchanged.
  

New Image

I've imaged the two nebulae (IC 59 and IC 63) near gamma Cas before, and it was time to revisit that to see how I have progressed. 

Here is my 2009 attempt

This poor image was tortured with wild stretching and clipping, then oversaturated to show some color. 

In 2022 things are looking better: better mount, better camera, better telescope, better processing. Here is the full frame

And here is the nebular part of the image at full scale

Acquisition details are at AstroBin. 

What really surprised me about this image was that it looks so good for having so little data. It's based on about 82 minutes total exposure spread across the LRGB channels. And short exposures, too: only 90s each! 

The optical performance of the FSQ is--at least to me--breathtaking.

 

First Image using NINA, PixInsight

I'm going to start this post with the credits. Usually these are left for the end but the amount of help they've given me earns them top billing.

For using NINA and associated plugins, you could not do better than to watch closely the many tutorials created by Patriot Astrophotography . Chad's presentations are concise and clear; even when he suggests some of the technical portions might be a little on the dull side, they're anything but.

Also well worth viewing are tutorials by the Cuiv, The Lazy Geek . His tutorials are often in demonstration form and tend to be more informal than Patriot's.

You probably already know this great reference for PixInsight, Inside PixInsight by Warren A. Keller. It's been my main resource for starting LRGB processing.

----------

Although I hated to do it, my first clear night in quite a while was dedicated to playing with NINA's autofocusing (AF). 

AF starts at a good (but not necessarily great focus position). From there it racks your focuser out by several "step sizes," takes an image and analyzes it, then racks in a step size and reimages, continuing until it has taken however many steps you specified. Because every geared focuser has some backlash (which has a first guess value of zero distance), that first inward rack will be soaking up that backlash. If your step size is smaller than the backlash no change in focus will result. Through iteration you work you way to producing a nice bowl-shaped hyperbolic curve with the minimum at the point of best focus.

In doing this you will determine two values: step size and backlash. Patriot Astro has a great video showing you how to do this. I was able to determine the values for my FSQ-106-mounted Pegasus FocusCube and was able to get hyperbolic fits with R^2 values uniformly 1.0. 

A second convenience that NINA provides is the use of filter offsets; these are basically the distance by which your filters are not parfocal with a reference filter (usually taken as the luminance filter). Using filter offsets allows you to move from filter to filter without having to go through an AF sequence. This saves you time that you can use for collecting light frames.The process of measuring offsets is automated by a plugin called Darks Customs, and this video explains how to use it. So how parfocal are Astrodon LRGB filters? Very! 

[Here are the numbers for my FocusCube: step size = 35 and backlash = 450. Filter offsets are luminance = 0 by definition, red = +7 focuser steps, green = -6, blue = -1; The narrowband Baader filter offsets are Ha = -52, O3 = -20, and S2 = -48. For perspective, the FSQ focuser has a travel of about 30mm; this corresponds to about 8000 FocusCube steps. The distance in mm for an offset is therefore equal to 

offset in mm = offset in steps * 30mm / 8000 steps = offset in steps * 0.00375

The largest RGB offset is therefore 7 * 0.00375mm or 0.02525mm. That's 1/38th of a millimeter!

Another way to think about the offsets is to compare them to the step size, which can be thought of as the travel needed to change star diameter by 25 to 50 %. An offset of 7 is just 1/5 of the step size, so using the offset in this case may lead to some improvement over assuming parfocal,  but it probably won't be much.]

Getting AF ready was one night's chore. The second night was doing a trial image using the Advanced Sequencer. Using filter offsets made for a very simple sequence: Cool the camera, unpark the mount, run AF on the luminance, slew and center on NGC 188, start guiding and shoot 20 frames of each filter in the order of offsets from negative to positive: green, blue, luminance, and red. (This ordering means the focuser  only moves in one direction, eliminating the need to deal with backlash.) The triggers for this were AF after a significant change in star width and to dither every third light frame. 

Almost everything worked perfectly. But--it was crazy windy and that gave PHD2 fits while trying to recover from dithers. This resulted in a number of frames that had terrible stars, and those triggered AF runs that wasted time. I need to apply a better settling time the next gusty night. 

AF worked to perfection. Stars for each filter were near perfect. My target was NGC 188, an open cluster near Polaris. Processing in PI resulted in this image.

I had trouble dealing with the light pollution and the end result is a rather blotchy image. I'm sure flats would have helped a lot. 

New moon is coming up, so weather  permitting there will be more imaging!

 

Jumping the APT ship for a ride with NINA

I hopped on the imaging automation wagon reluctantly because I'm very old school. My mounts had go-to that I seldom used; star hopping and a good finder were all I needed, right? Absolutely! I did the H400 pushing a non-electronic 10" Dob from star to star to H object, and it was fun. All I needed was a red light, star atlas, and dew strap for the finder.

Then I started imaging and kept right on hopping. That worked for awhile, but then it became evident (only because someone pointed it out to me) that I spent a lot of time hopping when I could have been collecting photons. Reluctantly I started to move into the 21st Century. A friend suggested a setup that included planetarium and acquisition software. 

The planetarium part was easy enough as I liked Stellarium's simplicity. For acquisition I already had ImagesPlus.  IP and photoshop handled my calibration and image processing needs. After completing the Astronomical League's Bright Nebula list I switched from CCD to DSLR and I changed to BackyardEOS for acquisition.

Then things happened.

I became involved with the creation of a club imaging platform. This brought me into contact with more modern imagers, and they gently suggested I modernize. For the platform I surveyed available acquisition software and put APT and SGP on the short list. APT looked horribly complex (partly due to the clunky interface) and the way SGP worked seemed counterintuitive to me. The decision was made by someone else after I left because of the pandemic, but for myself I decided on APT.

Next, a friend wanted me to learn PixInsight so that I could teach him. I knew PI was a fine package, and that eventually I'd want to wean myself from Photoshop, so PI became the third leg of my imaging tripod: Stellarium, APT, and PI.

Which was how it stood until yesterday when I revisited NINA. In 2019 I had considered NINA briefly but thought it was too new, too undocumented, and too undertutorialed (if that's a word). And since it was Open Source and free, I had concerns that it might wither and have a premature death. Now it's 2022 and none of those concerns are valid. So it is time to revisit NINA. And after a day inside seeing how well it plays with my equipment I'm ready to switch.

First and only somewhat important, NINA looks great. Better yet, the style of NINA complements its large set of features; it seems, at least to me, incredibly intuitive. I've already had a dry run with NINA and my complete imaging setup, and I'm ready to try it out when we have a clear night.