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.

Getting Real in the Year of the Coronavirus

Old business first. Last time I looked at the idea that a 100W solar panel would be more than adequate for replacing the energy spent in a previous night of imaging. What needs to be realized about this idea is the uncertainties that come into play with it. Here are a few:

• I rarely image for an entire night as assumed. In fact, I can recall doing so on only two occasions. Usually either fatigue sets in or the sky goes cloudy and you lose a couple of hours.  
• Getting four or five consecutive nights clear all night is not something that happens often. In my experience the rule is maybe half the nights of a star party are clear.
• Some imaging sites are quite dry (like Nebraska) and active dew control isn't needed for the first several hours. This eliminates one of the larger power requirements.
• Starting with a fully charged laptop (which is almost always the case) greatly reduces its power consumption. 

In other words the estimates I made for required energy were probably overestimates. So I feel safe in saying that the panel in consideration will be adequate. It's not going to be able to run an air conditioner or refrigerator, but it will be fine for imaging.

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Now let's get to the topic of the moment, if not the decade, COVID-19. As I write we know that this virus is relatively contagious, spreading across the country, and tough on older people. Active cases are showing up in Minnesota and Nebraska, and doubtless will appear in South Dakota in the coming days. [Update: The day after posting this South Dakota reported 5 cases with one fatality.] Right now the cases are being contained through quarantine; what the situation will be by mid July and the Nebraska star party it's impossible to know. A safe guess is that the virus will be widespread by then and that most group activities will be suspended; NSP may not even happen. Another consideration is that my wife and I are both in our 60s and stand a significant chance of requiring medical assistance should we become ill with the virus. Because of that my current thinking is trying to avoid the illness at least until the end of the year and the release of a possible vaccine. Even without the creation of an effective vaccine it's hoped that doctors will learn how to better treat the illness.

Avoiding getting sick relies on some simple fundamentals:

1. Avoid people who may be infected. Given the asymptomatic spread of the virus this means avoiding pretty much everyone. Especially to be avoided are being in close quarters with many people, such as might happen on a cruise ship or commercial airplane.
2. Wash one's hands thoroughly and often
3. Avoid touching one's face

This is what we will be doing for the next year and hoping to catch some luck. Barring a minor miracle I won't be at NSP this year or any other star parties. My back yard will be safe enough I hope, so I'll try to do some astronomy from there!

Good luck to you in the coming year, it's going to be a difficult one for all of us!

Another Imagining Year Ends; Solar Panel Recharging of Batteries.

Bye-bye, 2019

Winter has fallen onto the region with a loud thud. Snow depth is now seven inches and the temperatures are near normal (for the next week, anyway). For a warm weather person like myself this essentially means outdoor astronomy is in hibernation until spring.

It remains possible that I may use the imaging platform at Cherry Grove, but I can't say I'm in the mood for that at the moment. So let's see what else there is to do.

I have some mirrors that are in polishing/figuring stage, so I could get back into those.

There's always the task of learning image processing software, but if things continue on like they have the last two years with awful weather there's no rush.

I could do some programming and try to quantify the meteor reflection data I collected a couple of years ago. But instead, let's have...

More Power Fun!

One thing that intrigues me is solar power for recharging batteries at remote sites. A few years ago when I priced this out solar panels were too expensive compared to buying batteries. But with the continuing decline in panel prices it's time to reassess.

The first step is to determine my power needs. This is the product of my imaging setup's power requirement and the number of hours spent imaging in a typical evening. The first is something I've measured; my current setup (mount, laptop already charged, dew heaters set higher than usual at 50%, CCD with cooling at 70%, autoguide camera) setup draws about 3A. That means I can image with about 40W of power.

Next we need to know how many hours this power will be needed in an evening of imaging. Let's consider the cases of an equinox and summer solstice at 45N latitude, and for each imaging through either nautical, astronomical twilight, or full darkness.

Summer solstice: full dark 3:20, astronomical twilight and darker, 5:31; nautical twilight and darker, 7:10; civil twilight and darker, 8:25; sunlight, 15:35.

Equinox: full dark, 8:31; astronomical twilight and darker, 9:42; nautical twilight and darker, 10:57; civil twilight and darker, 11:50; sunlight, 12:11.

Let's say you image during astronomical darkness and start up about a half an hour before that for polar aligning, target acquisition, and letting things settle. Depending on the time during the summer you will be using power for about 6 hours (solstice) or 10 hours (equinox).

Multiply the above hours by 3 amps and you get 18Ah (solstice) or 30Ah (equinox). These are what you need to put back into the battery after an all night imaging session. (In terms of energy in watt hours, these are about 216 and 360 watt hours.


[Digression: My primary battery is 50Ah. Draining that by 18Ah is only 36%; a 30Ah draining is 60%. By August 1 this has changed to a drain of 22Ah or a 44% drain.]

At this point it's tempting to say a 100W solar panel can bring a battery back up to full charge in only a few hours. Can it? There are a few wrinkles to consider that can reduce that 100W:

• Clouds: Cirrus are no problem, but typical fair weather cumulus can drip power by anywhere from 8 to 20% [ref]. Total overcast drops power by 50 to 75%.
• Heat: Higher temperatures are doubly bad. Panels become less efficient as the temperature rises, and AGM batteries are better off being charged at lower voltage. For typical NE afternoon temperatures (37C or 95F) this leads to a panel efficiency drop of about 2.5% and an increase of about 6% in battery charging time.
• Resistance losses can be minimized by using wires that are heavy enough for their lengths. In my possible system this means using 12AGW throughout and keeping the runs reasonably short, and should not be a factor.
• Charge controller efficiency. MPPT controllers generally have an efficiency in the area of 95%.
• Panel orientation isn't a big factor so long as you can keep the panel face reasonably perpendicular to the sun. This means turning it hourly and using some kind of adjustable altitude brace.

In the worst case it's a hot, overcast day (which are rather mutually exclusive) and we multiply 100W times 0.5 for overcast x (0.975x0.94) for a 95F day x 1.0 for resistance loss (none) x 0.95 for controller loss x 0.86 for being 30 degrees off perpendicular all day. In other words, that 100W becomes 37W. 37W times total daylight time minus two hours is about 500 watt hours (solstice) or 370 (equinox).

Conclusion: Even in an unlikely worst-case situation a 100W panel + MPPT controller should be able to do nightly recharges adequate for imaging using my setup.