Reservations, Smoke, and One Night of Imaging

A few things from a less than fully successful week of dark-sky camping:

Reservations

The initial state park reservations I had were for three nights starting Tuesday. Clouds and rain looked very likely to wipe out the first two nights so I cancelled the reservation and made another for 3 nights starting Thursday when the forecast was much more favorable: one iffy night followed by two that were perfect.  I decided to get everything set up and running that iffy night after seeing the Sun wink out as it set into a heavy smoke layer on the northwest horizon. This turned out to be a good move as this would be the only useable night. The heavy smoke arrived by Friday morning, when two hours after sunrise the Sun was a dim red ball you could look at directly. 

Lesson learned: Minnesota state parks offer same-day reservations.  Next time I'll wait until I'm sure the night will be clear to make my reservation.  All my things are very well organized and I can pack the car and be on the road in less than an hour. My preferred dark-sky camp, Lac qui Parle, is lightly used and usually has unpowered pull-ins available.

Mount Safety Limits

By the time I was ready to shut down that first night my mount had rotated to the point that it was well beyond its safe travel limit. This didn't really matter as looking to Polaris allows much further travel than is usually safe, and the G-11 mount tracks nicely even when it's over-rotated and the counterweight shaft is well beyond horizontal. 

That said, what I expected was a meridian flip sometime around midnight. When that didn't happen I recycled the system and expected go-to would put the scope on the correct side. It didn't. I could see that eventually I'd run the camera against the mount and decided to let it go right up to that point before stopping. 

I got enough frames that night, but in a month when I return to shoot color frames I'll have to stop even earlier in the evening. 

Lesson learned: I need to configure NINA and my Gemini-II mount control to properly handle flips.

Here are two videos that I found useful for doing this and for setting up NINA for flips:

https://www.youtube.com/watch?v=Rk8uOikHPb4

https://www.youtube.com/watch?v=0N0U5chskCQ

There's also a very useful spreadsheet available to members of the Gemini-II user group on groups.io (See the second link above for how to use the spreadsheet.)

I've made the changes to my Gemini-II and go-to now seems to put the telescope on the correct side based on the limits. Seeing if automated meridian flips work will have to wait for a night under stars.

The Coleman Bug Shelter (Previously mentioned here.)

This was my first night out with the shelter, and it worked great--no gnats, no mosquitoes inside. I sat in the shelter linked to the scope with a 16' active USB 3 cable (which was also getting its first all-night imaging test). There wasn't a single glitch. The only awkward part of this is doing polar alignment, when I (and the laptop) need to be at the mount to make adjustments. Once that's done, it's back into the Coleman. It was so comfortable in there that I spent most of the evening relaxing with a good book.

Lesson learned: I'm ready for next year's Nebraska Star Party and its all-night supply of mosquitoes. Will the shelter, even when staked down, be able to endure the winds of Nebraska?

The Results

If the Eagle Lake Observatory setting is Bortle 4 plus a bit, then Lac qui Parle with Thursday night's smoke was Bortle 4 minus a bit: definitely darker than Eagle lake, but certainly it wasn't the Bortle 3 I've seen  there before. Despite that, I gathered 113 luminance frames. Seven were discarded for being in twilight, and one was lost for poor tracking. Adding the new 105 frames to the previously collected 72 Eagle Lake frames brought me to about 4.4 hours of total luminance exposure.

Here is the result, as produced by PixInsight's WBPP and some modest postprocessing of my own:

IFN (luminance, 4.4 hours)

This is much better than my 72-frame image, and it may be all the luminance I need to collect. Using the 3:1:1:1 "standard LRGB model" what's left to shoot is perhaps an hour and a half of each color channel. I have the new moons of June and July to collect my color frames.

Lesson learned: some smoke at a Bortle 3 may be better than clear sky at a Bortle 4+ site.  Given enough good nights I'd still like to add more luminance and get to 6:1:1:1, but good nights around here seem all too rare.

Satellites Galore (with bonus Trek Humor)

These are the satellite tracks rejected by PixInsight. There are a lot of them in 4.4 hours!

"Go home, Tholians, you're drunk"

That's all for this post. In a couple of weeks the moon will go away again and I'll try to get the color data that will bring this luminance to life. 

Reprocessed IFN Using PixInsight's WBPP

The image in the last post was really not very well processed, with the culprit being me. I suspect I twice subtracted bias or something. It was so bad that I decided to reprocess immediately, adding in some color channel data I collected. The best way I could see to avoid messing up again was to plunge right into using PixInsight's popular Weighted Batch Preprocessing script (WBPP).

Was it easy to use? Yes! If you disagree, I suggest watching the series of WBPP tutorials by Adam Block.

Did it work well with all the default settings? Yes, it did for me. The only step I skipped was Cosmetic Correction. I'll have time to learn how to incorporate CC between now and when I need to process new data collected later this month. 

Was it fast? I fed it my 72 luminance frames, 36 color frames, 100 bias frames, 30 dark frames, and 100 channel flats. WBPP made master frames, calibrated my light frames, and registered and integrated the lights, and finished by doing a crop of all four channels. All that in 51 minutes. Wow!

I know there's some sort of WBPP Fast Integration thing that can reduce this even further, but I'm saving that for the future.

The WBPP result is so much better. Here is the master luminance after post-processing:

Polaris IFN as processed by PixInsight WBPP

The full scale image is on AstroBin. Because Astrometry.net as employed by AstroBin seems to have issues with this, I'll pass along ASTAP's solution:

ASTAP solve of above image.
North is up; the celestial pole is a little beyond the top edge

This is exactly the composition I want: Polaris sitting at top center and giving the illusion of shining its light down on the nebulosity. Which it probably isn't actually doing, but artistic license is allowed, right? 😏

Not only is that ugly vertical banding gone, the stars are better shaped. ASTAP puts the tilt at only 3% ("none") compared to the previous "moderate." I continue to be amazed that so much nebulosity can be captured with less that two hours of total exposure at a Bortle 4 site with a nasty high-in-the-sky first quarter moon.  

The color image was not adequate and you won't see it here. It looked as if the background flattening of the three channels had gone awry. I'll need to play with the color channels and see if I can do better.

The night I collected the color frames give me hope for my camping trip. PHD2 guiding was almost perfect. Of 36 frames, none were rejected. With dithering turned off there were no hiccups. I retrained PHD2 beforehand, this time with the correct focal length for the guide scope, and it seemed better behaved. 

Reacquiring the image area worked great. The evening was the third time I told NINA to go to the target. It seems to be doing this quite well: almost nothing has been lost due to mistargeting: 

Portion of full image removed by WBPP cropping (red)

Everything considered, it all worked as intended. That's a little scary; I have to wonder what mischief my hardware has planned for me when I take it to the dark-sky campground.

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While the tariff wars have devolved into confusion over what, when, and how much, the Rokinon 135 mm f/2 lens for Canon hangs in there at the same old $449. If you've been watching the astronomy gear dealerships, you've probably noticed that many items are no longer in stock. Buyers seem to be rushing their purchases to avoid the expected higher prices.

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?

My 135 mm Tamron Delusion Ends, It's Plan B now

I really thought I could get away with using my old Tamron lens for imaging Integrated Flux Nebula (IFN), but it's not to be. The number of minuses kept growing as I spent more nights practicing with the setup. I realized that my desire to use the Tamron and was blinding me to the issues that doomed it.

The greatest difficulty was being unable to rotate the field of view in a reproducible manner. This happened every night I used the setup with one night being 45 degrees out of kilter from the others. Keeping the camera orientation consistent between multiple imaging sessions is essential; without this, some of the field will need to be discarded during stacking. It became obvious that the amount of lost field would probably be substantial, resulting in a much retained field of view. The advantage of the wide 135 mm field of view would be lost. I think the cause was the ring clamp I was using to join the lens and camera to the dovetail. To permit manual rotation of the camera this ring had to be loosened and retightened many times, resulting in misalignment.

Image quality was also not what I wanted. There was no reasonable solution for the back focus error and I would be stuck with strong aberration needing to be corrected by BlurXTerminator. I knew some residual aberration remained, and I was concerned that this might show itself during the aggressive processing I would use to draw out the IFN. 

I came to realize that the stepdown ring I was using to produce spikeless stars was causing severe vignetting. While flat frames could somewhat compensate for this, too much signal was being lost -- again diminishing the effective size of the field of view. Using the lens's internal blades to stop it down was an alternative that created large, flaring spikes around the stars. I found this unacceptable.

Plainly, the lens was not up to the purpose and it was time to move to Plan B.

Plan B

The fallback is to use the FSQ-106 + focal reducer operating at a focal length of 387 mm and focal ratio of f/3.65. This California Nebula image used that configuration and gives you an idea of what it can do. The advantages are many over the Tamron: 

• 17% increase in speed (f/3.65 vs f/4)
• A very flat field with modest vignetting  
• An actual rotation ring
• Amenities like autofocus, autoguiding and dithering, easier creation of flat frames, and automatic meridian flipping

This is a much heavier scope to tote around, but the only real disadvantage it has is the smaller field of view. Here's a comparison:

135 mm Tamron field (outer box) vs 387 mm FSQ field (inner box)

The star cluster is no longer in the FOV, which is fine as the IFN is the real target. Does the smaller FOV (about 3.5 x 2.3 degrees) include enough IFN to be worth imaging? This image of Polaris IFN by another imager has essentially the same FOV as my setup will produce. I think there's enough IFN there to make it worthwhile particularly if Polaris can be reduced in size. I'll also compose the image to have Polaris much closer to the north edge of the frame, making more room for the IFN. 

Other aspects of the comparison image are worth looking at.

The scope used was an f/5.5 refractor with a flattener that didn't affect the focal ratio (so far as I can discover). The camera, an ASI 6200 color camera, has a quantum efficiency about the same as my ASI 2600 mono camera. The total integration time was 5 hours and 10 minutes. My thought is that if I want a reasonably deep image with low noise I should try to get at least twice the total time that went into the image. I'll probably use a plan that requires two nights of imaging: 5 hours of luminance one night, 3 hours of Chrominance another night. That's roughly the equivalent of 11.7 hours of one-shot color gathered at f/5.5. 

Yes, I know, that's a LRGB ratio of 5:1:1:1 and instead of the usual 3:1:1:1. I just like working with luminance; one night a few years ago something glitched and I ended up shooting only luminance. The final ratio was 6:1:1:1 and the result was quite nice (in my opinion, of course).

The comparison image was created using 5-minute light frames, which is probably why star colors are muted and Polaris is bloated. I've had much better luck with shorter exposures, and may simply go with 90 s lights. Both of my linked images used 90 s lights exclusively.

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Tariff watch: the Rokinon 135 mm lens (Plan C) is holding steady at $449 and in stock at B&H.

IFN Setup Passes Its First Tests (With Help From BlurXTerminator)

Last night was good for running some tests on my integrated flux nebula (IFN) imaging setup. I was able to take test frames at different exposures (60, 90, 120, 180 and 240 seconds) and test go-to and tracking. Everything came out well, or as well as could be expected and many questions were answered.

Did Polaris throw an internal reflection?

I stretched a 240 s exposure using PixInsight's Boosted Autostretch and there was no evidence of any internal reflections. It's possible something will show up in an image stack, but this suggests even if it does it will be faint.

Was the field suitably free of aberration? 

Here's a visual comparison of the corners and center in one of the 2 minute exposures (click for full scale). This is basically a raw frame; it's only been brute-force flatted and then delinearized with PI's default stretch.

Pretty awful, isn't it? My guess is that the aberration is coming from backfocus being significantly off. How much off, and in what sense? I'd use NINA's aberration inspector to find out, but this is a manual-focus lens. Sadly, my ability to change the backfocus is next to zero. Skip the following paragraph if talk about backfocus bores you :)

My required backfocus should be about 45 mm (44 for the lens plus1 for the filter), and I'm currently at 42.5 mm. The best I can do to increase this is by adding a 0.8 mm thin spacer or whatever the thinnest M42 spacer ring is (probably 5 mm?). Decreasing the backfocus would require a Canon-M42 adapter that's thinner than 10 mm or a filter drawer that's thinner than 20 mm and can be adapted to use 36 mm filters. Increasing the fun is that this lens is actually at heart a Tamron Adaptall lens circa 1980, fitted with a ring to make it compatible with OM-1 cameras. Both date back to the 1970s, so good luck finding things to take advantage of any of that. And yes, I looked into having a custom adapter built, both Canon to M42 and Olympus OM to M42, and they can't do it in a way that works for me (not to mention it would be $$$ if they could).

Fortunately the aberration can be adequately dealt with using BlurXTerminator (BXT). The corner diagram below shows how well BXT fixes things using the very non-aggressive settings of zero for both its "Sharpen Stars" and "Adjust Star Halos" parameters:

The improvement is almost miraculous. All the corners look sharp. So the lens passes this test thanks to processing with BXT.

Can the lens reach a decent focus?

The focus you see is the result of a few minutes of shooting test frames and making very tiny manual adjustments (just like in the old days before I had an electronic focusing motor). I think it's quite good. Yes, I'd love to have NINA do the focusing for me, but that's not going to happen.

I will need to stabilize the focus wheel to avoid accidental movement; a piece of tape should work.

Was there tilt?

A first look at tilt as calculated by ASTAP gave this.

It's not so much tilt around one axis as it is a sign of the aberration. ASTAP considers the tilt severe (see the small text along bottom of image). After BXT has been run the results confirm the improvement seen in the second corner diagram above: 

Star size outside the center is dramatically reduced and ASTAP now considers the tilt to be "almost none." This means I won't need to add the tilt plate or shims.

What about the mount and Go-To?

The mount slewed to Polaris and plate solved without fault. Manually correcting the rotation was simple and fast. The required rotation was only eight degrees, so the riser wasn't necessary and will be removed.

How was the tracking?

The center stars in the pre-BXTcorner diagram were nice and round so I'll assume tracking is close to perfect. The corner stars in the post-BXT are fine, too, so there's no appreciable field rotation in a 2 minute span.  I use PoleMaster for polar alignment, and it provides almost no visible rotation even over a multi-hour session, so I think that tracking should be more than adequate.

In other words, there's no need to add autoguiding or fiddle with PEC.

Were there any composition issues?

The amount of camera rotation required was only eight degrees from the filter wheel's long-axis up position, meaning that the riser wasn't needed. I'll remove it and the system will be a little sturdier.

Oddly NGC 188 was not quite where I wanted it. It's a touch close to an edge than I expected. I'll have to look at the instructions I gave NINA.

Summary

Everything worked better than expected with help from BXT! Basically, the system is ready for field use, although a little more work remains to get it set up for dew control. Because BXT removed the aberration using very nonaggressive settings, I don't think it will damage the IFN.

A major concern was the mount: would it behave itself for a target so close to the celestial pole? It slewed and centered on the target without difficulty. Manual rotation was easy and the riser won't be needed.

I think the ASI-2600 will do fine without dithering, but I may try that anyway with the PixInsight manual dithering tool.

It looks like almost any exposure will serve well; even a 4-minute exposure had nice round stars; I think I'll probably use 2 minutes for all four channels.

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My reading of Hugo Award winning novels is winding down. I skipped back to the 2000 winner, A Deepness in the Sky, by Vernor Vinge, and it was slog to get through. A few times it was almost a DNF (did not finish). I just couldn't connect with the author's writing style, his use of many side characters that were of little consequence, and the too-happy ending that seemed rather forced. For some reason he felt compelled to add a bloated epilog that served mainly to punish readers. Most of the Hugos have been worth reading, but not this one.

Up next is the 1939 Retro Hugo Award winner, The Sword in the Stone by T. H. White. Yes, it's that sword in that stone; the story has spawned a number of adaptations (the 1963 animated version by Disney is probably still the best known.

This will be the end of the Hugos for me, at least for a while. Maybe I'll start another reading marathon when my wife has her other knee replaced.

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It's lithium battery maintenance time: all the batteries have been fully recharged and then discharged to about 50% of capacity. Just before Northern Nights Star Fest I'll be bringing them up to full charge and selling/swapping them at 80% below list price. I'll provide a full description of what I'm bringing to NNSF in an August post.

A Few More Days to Clear Sky?; A Product to Avoid

Spring progresses slowly, but it appears that next Tuesday night (today is Saturday) will finally be clear and suitably dark for testing the things I need to verify about my IFN imaging setup before it goes on the road. In the meantime I've been putting together the traveling kit so that I can have all the cables and such needed for the project ready. It's also been time to top off all my lithium batteries. 

Lithium batteries are remarkably tolerant of abuse. The can abide deep discharges if you can get them to a charger within a day or so. Almost every lithium battery of any reasonable size now includes a battery management system that prevents too-rapid discharge or overcharging. The batteries also tolerate temperatures that I wouldn't! 

Maintaining a lithium battery is easy, too, even in the seasonal sport of astrophotography. At the end of the imaging year, just make sure they're they've been discharged to about 50% capacity, then every three months bring them up to 100% and back down to 50%. When you resume imaging and their use becomes more continuous just keep them fully charged. 

Yesterday I started the springtime full charge of the battery pack I use to power my laptop, and it revealed something I should have known. The pack in question is a pair of 15 Ah batteries in parallel, so I thought to use my 10 A charger.  The pack's only port is a 12 V automotive socket and the charger was sending 10 A through a fused automotive plug. All was fine for a while, but then the charger indicated it had shut itself off and there was a faint aroma of overheated plastic. That's never good.

Inspection of the plug showed the fuse was intact, but that the coiled spring at the base of the fuse was misshapen and the plastic around it had melted. Supposedly 12 V plugs can handle 120 W (10 A @ 12 V). At the point it started to overheat it was probably being asked to handle around 135 W, which evidently was too much for it. I suspect the rating for the plug I was using was well below this; I've seen some that are only rated for 60 W. 

I use one of these plugs to run power to my laptop, another to feed the mount, and a third to power the rest--CCD camera cooling, dew preventer, and USB devices. The total of all these rarely approaches 50 W and is typically more like 25 W, with a little going to the mount and the rest pretty much evenly split between the laptop and camera plugs. Although I've never had an issue with the plugs during imaging this current limitation is something to keep in mind if I ever change equipment. 

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At first glance this Astromania dew preventer looks like a great deal. A 10-inch strap with on-off switch and easily adjustable power control. And the connections are compatible with common 12 V power sockets. What more could you want for a mere $20?

From that buildup you can probably guess it was not quite a great deal. It was a pretty bad one, really.

I connected it to my primary power box and tried it out. I started with the toggle switch off and the power control rotated to the off position. My power box reported 0 W, 0 A. Good. Then I flipped the toggle on. Immediately the Current rose to 2.1 A and the strap started to warm up. In fact, it got quite hot: too hot to wrap around a cameral lens without risking damage. Obviously the controller was somehow defective. With the Controller at it's full-on setting the current was 2.4 A. Were I not a Vine reviewer, I would have returned this immediately. 

But there was another problem, the strap itself. Most straps are very flexible and have no problem conforming to the cylindrical shape of optics. This one won't do that. The plastic lining of the strap is thick and very stiff, and even working it for a while by hand didn't get it to wrap around a 135 mm lens without a few big gaps.

So it was a complete fail and got one of my rare 1-star reviews. Setting aside the problem with the strap the only way this would function is if you could control the current with some other device. And you would want to first make sure the strap connecter would be compatible with your device's strap socket. (It couldn't work with my Pegasus Powerbox or any of my other manual Kendrick controllers, for example. Yes, you could make an adapter for this, with a 5.1x2.5x3 socket on one end and an RCAphono plug on the other. But why bother.) 

Poor Weather & Caregiving: Renewing my Science Fiction Reading; The Tariffs at Work: Rokinon 135mm f/2 Lens Price Update:

Note that this post has little to do with astronomy or astrophotography, so if that's your only interest save yourself some time and move along 😉 

I've been astro-inactive for a while. There haven't been many opportunities for imaging; spring of 2025 in Minnesota has been cold and cloudy at night and sporting occasional snowfalls that recoat the ground. More important is that my wife had knee replacement surgery near the end of March; I've been home acting as her caregiver until she regains her mobility so even if the weather had been cooperative I really couldn't have be going out all night for imaging sessions.

What I've been doing instead is taking advantage of waiting room time by reading recent science-fiction novels. Given my age it's hardly a surprise that most of my sci-fi reading in the past has been of Golden Age authors (Asimov, Heinlein, and Clarke) with some of the 1960s and 70s anthologies of other authors mixed in. Larry Niven features large in these because I like hard sci-fi. I'm not entirely stuck in the past, though. I've read most of Ursula Le Guin's novels, much of Connie Willis's work, and several books by David Brin. And yes, even all three Three-Body Problem novels (more or less).

For My wife's post-op month I decided it was time to see what current sci-fi writers are creating. I decided the Hugo Awards would serve as a good guide and started reading my way through the last decade of winning novels. I hesitated at first given that the Hugos include fantasy but decided blending in some "soft" fiction would be good way to grow out of the hard sci-fi rut I was in.

Here are the first two weeks of intensive page turning summarized in capsule reviews, with a few notes for people who don't want to read certain types of content. The year shown is that of the associated Hugo award.

2024 Some Desperate Glory, by Emily Tesh.

This is the story of a woman born and raised on an asteroid fitted out as a militarized stronghold. It's the last, best hope of humanity to resist the conquest of the Majo, a collection of alien species slowly expanding its influence through the galaxy. 

Tesh writes in a way that challenges you to keep up with the story; her style reminded me of Le Guin's in The Lathe of Heaven. While some reviewers semi-dismissively lump the story into the "space opera" category, I think it has some significant things to say about both technology and humanity. The plot leaned a little too much on the deus ex machina trope, but the pacing kept me from being overly bothered.

Content Notes: AS, SC and a whole lot of violence.

2023 Nettle & Bone, by Ursula Vernon

Characterized as a dark fairy tale, this is pure fantasy with kingdoms, princesses, and spell-casting godmothers. It reads as an adult, grittier take on childhood fantasies. I had a little trouble with what seemed like a sluggish start, but once the author started adding supporting characters the pacing improved greatly, becoming a mix of humor and drama.

And then there's the scene in the Goblin Market, which alone is worth the price of the book.

2020 A Memory Called Empire and 2022 A Desolation Called Peace, both by Arkady Martine.

At one level these explore the ramifications of a technology that permits the transfer of knowledge, experience, and to some extent personality from one person to another. (The method here is strictly technological and not biological as with the symbionts of Star Trek.) The focus is on a woman thrown into the role of ambassador to a galactic empire. She's only somewhat prepared for what happens, and part of the fun and terror is her having to cope with an alien (albeit human) culture. The author's world-building is based on real past human empires and is fascinating to see unfold.  

Fans of Babylon 5 may wonder if the author intentionally borrowed from that TV series. The protagonist comes from a large, rotating space station (some of the descriptions could fit the Babylon 5 station). There are jump gates that permit movement through the empire and the empire itself resembles what the Centauri might have become if not checked by other spacefaring races and their own lapse into decadence. There's even an aged, ailing Emperor with intrigue between those maneuvering to be his successor. Oh, and let's not forget the mysterious attacks by large, shimmering black, and cloaked vessels from far jumpgates. They sometimes scream as they depart.

I don't mean any of that as complaint. If you want an extensive empire with far-flung possessions spanning tens of parsecs, you need to explain some way of getting around that old wet blanket Einstein. Jumpgates, wormholes, warp drives, hyperspace, folded space, infinite improbability drives, or whatever, numerous authors have already explored the territory. As long as you don't steal technology by its proper name (Sheewash Drive, for example) you're fine. The story is more important than the mundane tech bits.

The quality of the writing is what matters, and in these two novels it more than compensates. 

Content Notes: AS, SC

2021 Network Effect, by Martha Wells

This is the fifth entry (and first novel) in a series call the Murderbot Diaries. I've only read the  introductory novella (2017's All Sytems Red) , and it was a fast, breezy, and intriguing read. Network Effect is a full-length novel and it's recommended that one read everything leading up to it before taking the plunge. So I'm making the collection a birthday gift suggestion and it might be my reading material for this summer's Northern Nights Star Fest (if I'm not stuck at home when her other knee is replaced!)

Content Notes: Lots of violence, as you might expect when the protagonist is named Murderbot. 

2019 The Calculating Stars, by Mary Robinette Kowal

It's no spoiler to say this is an alternative history novel. If you don't mind reading about the many injustices inflicted on 1950s women and minorities (both religious and racial) this is an enjoyable throwback novel that in many ways is very remindful of the 2016 book and movie Hidden Figures.

The story combines both hard science and social commentary. The writing is adequate, occasionally rising to excellent -- particularly at the conclusion. This is the first book in a series of three.

My suspension of disbelief was mildly tested by what I felt like was an overstatement of what the described technology was capable of doing.

2016 The Fifth Season, 2017 The Obelisk Gate, and 2018 The Stone Sky, all by N. K. Jemisin

Yes, an unprecedented three consecutive Hugo awards!

These are world-building carried to an amazing extreme. At this time I'm in the third book and would love to explain what's happening, but my understanding of it is a work in progress. Riding along with the characters as they try to understand what's happening to their world is a big part of the fun. 

The story unfolds in a rather unconventional manner, but that's in keeping with the plot. I'd say more, but it's almost impossible to do so without resorting to spoilers.

Content Notes: Quite a bit of violence, much of it like something from a very dark version of Frozen. 

2015 The Three-Body Problem, by Cixin Liu (translated by Ken Liu) 

This wasn't read during this month's blitz, but I'm including it to round out the decade. This introduces a very alien culture and instantiates the Dark Forest answer to the Fermi Paradox. I enjoyed this book, but found the subsequent two novels (The Dark Forest and Death's End) so unreadable that I hopped rapidly through them to reduce the pain.

Content Notes: Mind-numbing content (mainly in book three and the second half of book two.) 

Content Notes for those to whom these things are important:

AS: Alternative sexualities. I found these were important to the plots, but you may feel differently.

SC: Non-gratuitous Sexual Content. Interestingly, it was The Calculating Stars that had the most explicit sex, suggesting that the author was making the story compatible with readers of romance novels. The only sex scene that felt a little out of place was in A Desolation Called Peace. (And no, I'm not going to tell you what chapter it was in so you can just skip right to it.)

All the stories involve spoken vulgarities, and most feature violence of varying degree.

If you're someone who resents anything that seems the least bit "woke," I'd suggest you stick to the Hugo winners from several decades past. Better yet, focus on the Retro Hugo Awards that recognize works from 1939 to 1954. Two of my favorite stories are there, Asimov's 1951 winner Pebble in the Sky (the first sci-fi I read) and Clarke's 1954 nominee Childhood's End. The latter is an amazing story, and it only lost the award because it was up against the equally amazing and iconic Fahrenheit 451 by Bradbury.

Just so you know, my wife's recovery is coming along wonderfully, and I truly hope that my next post will include some astrophotography news. 

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Tariff Watch:

[UPDATED : On April 5 the B&H Rokinon 135mm lens Canon EF version price rose to $479, $30 up from what it was on April 4. It's now up $110 from it's pre-tariff price in early February of $368. That's an increase of 30%. 

But hold on! The price dropped back down to $449 on April 6!  Was yesterday's price hike an error, or a preview of what happens when they need to restock? Wait and see!

TILT!

Yes, it's that enemy of flat fields: tilt in the optical train. 

Recall -- or don't, since I'm going to repeat the information anyway -- that my first choice for imaging the Polaris-area integrated flux nebulae was an old Tamron 135 mm f/2.5 lens that stopped down to f/4 is quite a nice lens. Second choice is to use my FSQ-106 with a 0.73X focal reducer that gives me a nice wide field. The FSQ is wildly higher in quality than the Tamron, but the only time I've imaged with the focal reducer it produced results that barely adequate: stars were noticeably elongated on one side of the image. 

I'll need to use the FSQ + focal reducer if for some reason the Tamron proves to be problematic. That means it's time to chase down the tilt problem and get it fixed.

What dawned on me recently was that there was enough back focus to allow me to use the tilt plate that came with the ASI 2600 camera I use for imaging. I had removed the plate to make the ASI compatible with my DSLR. The fact is that the ASI has largely made the DSLR superfluous; I'm  unlikely to image with it again. The tilt plate can therefore come out of storage and get back into action. Here's the present situation:

The configuration of interest here is the bottommost one. The reducer requires that the camera sensor be at a very specific distance from it: 72.2 mm. Currently there's a 12 mm M42 spacer in the optical train. Replace that with the tilt plate and a 7 mm spacer and it's all good (aside from some very thin spacers). 

Now, how to use the tilt plate? Let's start by verifying that it's the optical train and not the sensor that's out of whack. To do that correctly, I'd need to rotate the camera relative to the optical train and see if the effects of the tilt moved with it. I'm going to cheat a little and assume that if the field is flat for the native imaging mode (f/5) the sensor is fine.

Here's the ASTAP measurement of tilt in a single luminance image taken with native mode (f/5):

ASTAP report of field flatness for FSQ-106 & ATI 2600

So you're probably asking, "what the heck is that?" The numbers next to the yellow lines are the area-averaged half flux diameter (HFD) of the stars. The HFDs essentially measure how pinpoint the stars are, and they can be affected by focus quality, seeing, and aberration and tilt problems. A perfect telescope with perfect optics and perfect seeing would have very small numbers in this diagram.

Tilt will introduce variations in HFD that are in the direction of tilt. So how does one assess these numbers? ASTAP does that for you. If you look along the bottom edge of the above picture you'll see it assesses the tilt at 6%, which it judges to be "almost none". Great! This suggests that the native optics are adequately tilt-less--and by extension that the sensor is reasonably perpendicular to the optical axis.

Now here's the ASTAP analysis for a luminance frame taken using the reducer (f/3.65):

Same as above, but with the focal reducer

ASTAP says the tilt is 19% (moderate). It also confirms my eyeball judgement that the tilt is largely oriented along the long axis of the sensor. 

(Yes, you could deal with some star elongation in post-processing, but isn't it better to not have to do that? This brings us back the the first defense against tilt, a tilt plate.)

The ZWO tilt plate works using three adjustment screws arranged in an equilateral triangle, much like the tilt screws for adjusting a small Newtonian objective mirror. What I'll do is to orient the plate so that one of the adjustment screws is in the direction of the tilt, like so:

Orientation of ZWO tilt plate: blue arrow = tilt direction, red dots = adjustment screws

This way the adjustment screw at that left vertex becomes the primary one to adjust. Note that ASTAP has an option to provide a 3-point analysis which may be easier to interpret in some cases.

The process of correction is basically repeating the sequence of imaging, analyzing, and adjusting. It's another new skill to learn and put to use, which is good. There doesn't seem to be much to it; I'll let you know how it goes.

Unfortunately this won't work for the 135 lens; it has no spacers to swap out for the tilt plate. Should I find it needs correction, I'll probably use these things. I might get that and see if it's all I need for correcting the focal reducer tilt, too. If these shims work for that it would eliminate the need for a tilt plate and make it easier to change from one configuration to another. 

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At least it's March now. A few inches of snow is coming in the next day or so, just because it can. Almost time to make my reservations at Lac qui Parle!

[Added 5 March, it was more like 9 inches.]

Update: Risers

Last time I mentioned that my setup for imaging integrated flux nebulae won't allow a rotation range quite up to the 180 degree minimum I'll need. I mentioned a riser would probably be needed.

What should show up on Amazon Vine for review the next day but this: 

Car seat risers.

Yes, they're car seat risers for when you're not tall enough to drive your vehicle. This set comes with two 1" and two 1/2" spacers, nicely drilled through. The bolts are provided to fit the car model of your choice and are entirely too large for my purpose, so they go in the odd bolts jar.

One problem with these is that the edges of the spacers are too far from the hole and extend into the movement of the camera, keeping it blocked. When I realized this I thought all was lost because these felt as if they were made of metal and probably difficult to work with.

They're not!

What exactly they're made of is a mystery. An ordinary hacksaw cuts them with relative ease producing a sort of black, plasticky "sawdust," so I assume they might be made from some sort of composite material. In fact, it looks as if these might be created with a 3D printer. 

Whatever their composition, two minutes of hacksawing shortened one of the ends. With a quick trip to Home Depot for a M6 1x40mm bolt it was ready. It turns out the 1" spacer is sufficient, providing over 180 degrees of rotation.

Camera on riser. It may look a little precarious but it's solid with very little flexure

It's ready for the next step: assessing image quality. Will there be nasty internal reflections? Given that this is a new lens/sensor pairing will it produce a flat field at infinite focus? Will the lens to sensor separation need adjustment? Questions questions questions!

Spring is in the air -- today's high was at least 52F.  A week ago it barely managed to make it up to -2! I know, it's not April yet. Even worse, it's still February, the month that never ends!

Cabin Fever Dreams About Imaging IFN

Yes, it's mid February, the 2025 Nebraska Star Party mailing has arrived, and cabin fever is raging as temperatures are forecast to hit -18 F. Obviously that makes it a good time to play indoors with the imaging setup and ponder about the integrated flux nebula imaging I talked about last time.

The Setup

Here's a picture of the tentative setup that doesn't use guiding: 

Non-guiding setup

There's not much to it: camera, electronic filter wheel, lens, and "Frankenhub" for USB 3, power, and Dew control. This will be my "Version 1" to try at first. If it doesn't deliver adequate star shapes, I'll move on to Version 2 that includes guiding:

Same as in image above, but with guider swapped in for the hub

The hub will be a part of this, too. I'll attach it somehow to the underside of the dovetail or the G-11 saddle. This photo shows my old Orion StarShoot guider mainly because it can run off the ASI 2600's USB 2 port.

Note that in both setups the filter wheel limits camera rotation to a range of about 150 degrees, meaning there's a small (8%) chance I won't be able to get the exact composition I want. A suitable riser would fix this, so I may have to do some shopping.

I'm still eying that Rokinon 135 f/2 lens with a hefty measure of lust. Basic frugality stops me, and the truth is that I really am curious about how well the old Tamron lens performs for this task. The Tamron was about $90 in 1980; in 2025 dollars that's $342, close to the Rokinon's price before the tariff wars started up. While I've been writing this the price of the Rokinon has jumped from $368 to $409, an increase of 11%. 

PEC Training

This was a nice idea but after reading about what PEC is most useful for I doubt I'll bother with it. The focal length here simply isn't long enough for PEC to matter in any significant way. If tracking is fine unguided without training PEC, fine. If tracking isn't adequate I'll just use the setup that allows guiding. Many if not most commenters suggest that at short focal lengths guiding alleviates the need for PEC.

Guiding (if used)

The consensus seems to be that if one is using PHD2 and ASCOM guiding as I am (instead of ST-4) one should do PHD2 calibration by aiming the scope near the intersection of the celestial equator and the meridian. This is basically a do-once thing, only needing to be redone if you make a change in guider's orientation relative to the mount, such as rotating it around its optical axis. Once calibrated you can slew "anywhere" and it will guide properly.  I'm not entirely sure if it's possible to have guiding when aimed at a pole, or even at a declination like that of Polaris (3/4 of a degree from the pole). I'll find out if I decide to use autoguiding.

Dithering

Regardless of whether or not guiding is used, I'll want to dither. Even though it chews up some time I think it helps. If I'm guiding I'll try to use PHD2 dithering; if that works, fine. If not I'll dither with NINA. 

Acquisition

I would normally be tempted to use long exposures times for such a low surface brightness object like IFN. The problem is that long exposures tend to saturate stars; as a result, they lose their color. I want to keep that color as a contrast to the pale IFN. 

That means I'll need to use relatively short exposures of two minutes or less. Look at this image built from 90 s light frames to see what I think are ideal star colors. Yes, they're muted compared to what you see in a lot of images but I think they're more "natural" looking. (Never get me started on the rampant oversaturation of color in modern images!) 

Test images will reveal the optimal exposure length.

I'm going to shoot total exposure in the L:R:G:B ratio of 3:1:1:1. Maybe even 6:1:1:1. There's nothing magic about this, I just like to lean on luminance. That image I linked to was 1:1:1:1. Nice color, but not a lot of detail. More luminance might have helped. 

For convenience I'll probably shoot only luminance the first clear night under dark sky. That simplifies taking flats, focusing, and gives me some freedom about where I shoot the complementary color frames. Ideally those could get taken the second night under dark sky, but two consecutive clear nights in April in Minnesota? Ha ha.

If I only get one luminance night I can process that and see how well the IFN shows up in it. That will give me a sense of how much more is needed.

Any binning that gets done will be in post-calibration processing.

Composition

Using the celestial pole as frame center won't work well with NGC 188, which I want to include in the image. I'll ask NINA to put Polaris at frame center with NGC 188 in one corner. 

It should look sort of like this:

Planned IFN FOV (red box)

Combining Sessions

Given the hours of total exposure I'll want, this will certainly require multiple sessions scattered across several nights. This means I'll need to have NINA slew, center, and rotate consistently. Can NINA and my G-11 do this for a target so close to the pole? I'll have to find out.

Processing

Every new image brings new things to learn in processing. My Veil Nebula mosaic project taught me not only about mosaics, but also more about color calibration and background flattening. It also led me to acquire new tools like NoiseXTerminator, StarXTerminator, StarNet2, and the script StarReduction.  I expect this project will be no different!

The Weather

Camping may be deferred until May's new moon. Around the time of the April new moon the average daily low temperature is around 34 F. Great for keeping the camera cooled, but a little too chilly for this camper (I use a tent). Things improve in May, when the average lows are in the upper 40s. Still quite brisk, but much more bearable. I'll probably use April as my prep month, taking advantage of friend's warm house, and make camping reservations for May.

So that's my (over)thinking at this point. Before heading out to the state park I'll need to do a few things:

• See if NINA can slew/center/rotate for the intended composition
• Shoot some test exposures to assess unguided tracking, and switch to the guided version of the hardware if it can't. These exposures can also be used to judge exposure time, and if the lens suffers from distracting internal reflections
• Collect maybe a dozen or so frames of each color channel making use of NINA dithering and verify that star color is adequate
• It might be useful to verify that my stop-down ring is actually giving me f/4. This can be done indoors at any time using my flat panel

Aside from that last item all I can do for now is play with the hardware and wait patiently for warmer weather. Spring can't come soon enough!

Happy 2025! It's That Time Again: Imaging Plans for the New Year

It's usually folly to plan a summer of imaging. Sure, clouds and smoke could spoil things, but why not give it a  try? 2025 might just turn out to be an exceptional year! State Park camping and two star parties! Let's go!

APRIL/MAY

The first new moon of the 2025 camping season is on April 27th, a week after Easter. So any time within a few days of that should be dark enough for deep imaging. Likewise the dark moon in May, which may be better (i.e., warmer) for camping.

The late spring sky doesn't offer much to image at the focal length of my FSQ-106 (530 mm), aside from groups of galaxies and a few clusters. There is one wide-field subject that has always intrigued me: integrated flux nebulae, or IFN. Here's a nice summary of what IFN is and is not, and where to find it.

Probably the best known and most frequently imaged IFN is in the direction of M81 and M82. Instead of that I'll go for the IFN near Polaris.

Imaging near the north celestial pole has some interesting aspects. Because the apparent movement of stars there is so slow it's common for people to suggest not using autoguiding when imaging at relatively short focal lengths. To do without guiding you need a near-perfect polar alignment; a well-trained periodic error correction is very helpful, too. PoleMaster provides alignment that's close to perfect, so that's covered. But I do need to train PEC and that will be one of the first things I do this spring. 

Associated with guiding is dithering, which I like to do. Is it possible to dither and not guide? Yes, with NINA's built-in dithering. I'll have to learn how to use this, and hope it works well. If it doesn't I'll probably just not dither.

I've never targeted anything so close to a celestial pole; A little testing suggests that my G-11 is fine with having NINA slew from counterweight-down it to the pole. What I'm not entirely comfortable with is NINA trying to center it there; will it get lost making excursions back and forth across the meridian? Is Polaris far enough from the pole to make centering a nonissue? 

Regardless of where the target is there's always the question of what imaging gear to use. The key characteristics of IFN are that it's very low surface brightness and extensive in size. That sounds like a job for short focal length and fast focal ratio, right? Here are my best options for the optics:

• Takahashi FSQ-106 (FL 530 mm, f/5);  Pinpoint stars, but smallish field and rather slow
• Takahashi FSQ-106 + focal reducer, (FL 387 mm, f/3.65); Pinpoint stars, very fast, but smallish field
• Tamron lens, (FL 135 mm, f/4.0); Fits NGC 188 in field, overmounted (not a bad thing), very fast, no autofocusing

Here are two trial images made using the Tamron. An H alpha image of the Lambda Orionis Ring from 2015 and an LRGB image of the Sadr area from 2016. Both used an ST-8300 mono camera, and I can't say my processing was particularly good (I was still using ImagesPlus). How well it works with my ASI 2600 camera is unknown right now. Will it need spacers? Will there be tilt problems? Will it show internal reflections when put on a relatively bright star like Polaris? I won't know until the weather warms up and I can shoot some frames. 

If the 135 doesn't work out I might go with the FSQ + focal reducer. Its ability to support autofocusing is some compensation for its small FOV. Maintaining the FSQ's focus will be important for dealing with the long all-night sessions (6+ hours in April, about 4.5 hours in May). With a small lens like a 135, it's easy to minimize thermal FL change and prevent dew formation (as suggested by KathyAstro) by wrapping a long dew prevention strap around it. 

Finally, there's the issue of exposure time. I'll probably use my standard 120 s @ gain 100 for luminance and try to collect as many frames as possible. If tracking is an issue, I can drop it to 60 s, but if stars stay nice and round, I might increase this up to as long as 300 s. Shorter exposures will be fine for the color channels; in fact, those might only be 60 s  @ gain 0 to keep stars from saturating. Some experimentation is needed!

JUNE/JULY

The Nebraska Star Party typically occurs close to the end of July, a bit too late in the year for imaging my desired target of the Antares/Rho Ophiuchi region. In June the situation is much better, and a good time for imaging it comes after the third quarter moon of June 18. The Antares and Rho Ophiuchi nebulae should look fine together at 135 mm. 

July is wide open for imaging much of the Milky Way, including the M8/M20 tandem. This pair will fit nicely into a single frame using the FSQ-106 with its focal reducer. Also available is M16, which nicely fits the FSQ native field.

LATE AUGUST

It's Northern Nights Star Fest time, and I'll continue collecting frames for the Soap Bubble. Recall that the Bubble had just started to show up with about six hours of frames collected in 2024. Continuing on this target in 2025 should put me over 12 hours of total exposure. Barring losing time to more Aurorae. 😁

SEPTEMBER/OCTOBER

The Iowa Star Party (2025 date TBD) will be a good time to gather more frames for either the IFN, the Soap Bubble, or some other target that suggests itself. Another possible target is IC 348.

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Obligatory Power & Battery Update 

As an Amazon Vine reviewer,  I have been able to get the components needed to replace my old 100 W solar panel and charge controller with a smaller, much lighter 50 W unit. Thank you, Vine!

Today wasn't ideal (high haze and tree branches) but it managed to supply 35 W. The charge controller seemed to work fine, and in an hour it boosted a 10 Ah LiFePo4 battery at rest voltage 12.96 V to 13.26 V. The meter suggested 20 Wh had been added to the half-charged battery. That's compatible with the rest voltages.

The real test will be when the sky is fully clear and the panel gets hot in the sunlight. I'll take it camping and see what it can do.