On Jun 19, 2021, at 2:40 PM, Dwight Fujita <kojifujitafodder@...> wrote:

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Probably late to the party, seeing as Brian Valente started uploading tutorial videos on the subject.? Thought I'd share here in case others might find the information useful.

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I use Ekos/KStars, since I can run it on a cheap passively cooled Raspberry Pi4.? More powerful PCs have active cooling on their CPUs, and I was finding the condensation on cold days had a tendency of gumming up delicate notebook PC fans.? Astro cams use active cooling too, but I find they are better designed to handle cold weather.

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A few months ago (March 2021), KStars made an improvement to their polar alignment tool.? Using plate solving and some spherical geometry, the tool allows you to polar align anywhere in the sky.

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The tool takes three images at different RA rotations to determine your polar alignment error.? It then asks you to select an anchor star that you use to reposition your polar alignment using your alt/az knobs.? You can use the tool at any declination in the sky.?

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I can't see Polaris from my usual observation location, and in the past I've used drift alignment in PHD2.? PHD2 drift align works well, but you need to drift for a significant amount of time to get accurate results.? I'm able to get good polar alignment much faster with 2-3 iterations of the KStars tool.

Thought others might find this info useful,

Dwight

On 19 Jun 2021, at 16:41, Dwight Fujita <kojifujitafodder@...> wrote:

I use the my main scope for the alignment procedure, fl=1000mm on a 3.8um sensor, or about 0.78"/pixel.? I've done it with my guide scope (253mm, 2.9um, 2.36"/pixel) and it also works fine.

I can't see the pole from my imaging location, so I usually point my optics at the equator.? Azimuthal adjustments are usually good the first time, but I sometimes need to retry dialing in the altitude adjustment.? Usually after the first try my misalignment is <5'.? After the 2nd attempt it's usually ~1', so the 3rd time is usually to verify the result.

Sensitivity to polar misalignment is different depending on what part of the sky you point at, and in my case, the procedure ends in the western sky.? My guess is that flexure and gearing backlash throw off positioning of the reference star when I make adjustment to the alt-az knobs.

The alignment procedure gives repeatably good results after I've correctly set my alt-az knobs, so I'm pretty sure the problem occurs after the 3rd image capture and when I make adjustments.

My guess is that this would work much better if I could point my scope at the pole.? Even with iterating the procedure, it's still faster than drift aligning in PHD2.

Thanks,
Dwight

On Sat, Jun 19, 2021 at 02:39 PM, Dwight Fujita wrote:

Probably late to the party, seeing as Brian Valente started uploading tutorial videos on the subject.? Thought I'd share here in case others might find the information useful.

HI Dwight

you're not late to the party at all :)

There are too many options to cover them all, but it's good to hear about this one.

if you happen to know and can recommend a good tutorial on this approach (or if you have the time and inclination, record one yourself) we'd love to include it in additional resources "roundup" that i think i will do as well

Magnus,
Thanks for the great link.? I didn't know Hy Murveit posted such a detailed write-up.? He recently appeared on The Astro Imaging Channel to talk about some of the new features in KStars:


It dawned on me that I should try to end the procedure close to the meridian.? Altitude adjustment should be orthogonal relative to any RA error caused by backlash.? Azimuth dials in quicker probably for the opposite reason.? I could try reversing the direction of the slew after the 1st attempt, or doing the procedure east of the meridian.? Perhaps someone has already thought of this on the forum thread above.

Les,

Getting the KStars environment to work is a bit of an adventure in itself.? You can install KStars in Windows (if that's what you currently use), but I don't think there is ASCOM support.? You would need to connect to a *nix machine over a network like an RPi, a PC with Linux, or a Mac.? Gemini is already supported in INDI (I use ethernet) as well as the ZWO cameras that I use.? There are pre-baked retail packages that use KStars for RPi, or you could try the free Astroberry image that includes things like PHD2.

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My suggestion is that you buy the largest MicroSD card you can find, because the plate solving index files you need to download separately do take up quite a bit of space.? I wouldn't try the online solver, offline solving is WAY faster.

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Thanks,

Dwight