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Old 04-12-2020, 11:31 PM
ecuador
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"Hop" polar align on iOS

Hi. I develop the (quite popular I am pleased to say) iPhone/iPad app Polar Scope Align Pro. I am always trying to improve polar alignment for all users, and from the feedback, it seems that the S. Hemisphere is usually a struggle (that darn SCP area is so empty of bright stars) so that many users end up using the app's "rough" daytime alignment tool and have to do drift alignment if they want more.
I recently implemented a Push-To functionality on the app and included a "hop to" option, where you first manually find a bright nearby star to calibrate your phone's gyro & compass before pointing to a target, and it got good user reports, as a calibrated compass seems to have an accuracy of half a degree or less despite interference, which is actually quite a useful accuracy.
You might see where this is going. I am thinking of adding a "Hop Polar Alignment" function to the app. If you can't see σ Oct in your Polar Scope, perhaps you can see β Hyi, or even Miaplacidus, Atria etc. The app will give you a list of stars that are above the horizon and up to say 30 degrees or so from the SCP, you choose one, target it with your polar scope (or your green laser for some mounts with a laser finder like the MSM), hit sync on the app and the familiar daytime alignment tool will start, but with a calibrated compass.
I thought I'd gauge interest, especially if some people might want to beta test it, as the weather is miserable here in the UK and I don't see me trying things outside for a while.
TIA
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Old 04-01-2021, 02:50 AM
ecuador
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I don't yet have any South Hemisphere testers, but this is how the current beta works:

- You get a list of recommended bright stars that are above your horizon and not far off the CP (there is a button to let you use any Mag 5.0 or brighter star though).

http://www.iceinspace.com.au/forum/a...9&d=1609692023

- In the example, Atria was selected, so you move your mount to make Atria centered in your polar scope (or pointed by your alignment Laser if you have something like the MSM rotator instead).

http://www.iceinspace.com.au/forum/a...0&d=1609692023

- Hitting "Calibrate" when Atria is centered in your polar scope (and probably not centered on the uncalibrated app), gives the app a reference point to adjust the compass/gyro, so it can guide you to the Celestial Pole using your altitude/azimuth adjustments.

http://www.iceinspace.com.au/forum/a...1&d=1609692023

Edit: Hmm, images show inline in my preview, but not after posting. Not sure what I do wrong.
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Old 04-01-2021, 09:22 AM
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vlazg (George)
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Great ap, use it a lot.
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Old 13-01-2021, 09:41 AM
RugbyRene (Rene)
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Hi,

Just like to say that I love your app and I use it to do a rough PA during the day. One question: is the accuracy of the PA affected by interference from the metal in the mount if I place the phone in the saddle?

Rene
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Old 15-01-2021, 07:04 AM
ecuador
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Quote:
Originally Posted by RugbyRene View Post
Hi,

Just like to say that I love your app and I use it to do a rough PA during the day. One question: is the accuracy of the PA affected by interference from the metal in the mount if I place the phone in the saddle?

Rene
Glad you like it. The quick answer is "most likely". It will depend heavily on the specifics of your mount, phone, location etc. Removing it, making big "8" movements in the air and trying again may help, but users who want to make it a bit more reliable come up with various ways of mounting it away from the metal.

It all depends on what you want it for. E.g. I made the daytime alignment tool to use with my Star Adventurer during the '17 eclipse. Mounting it on the star adventurer was enough for my solar eclipse session, the tracking was decent to keep the sun in the DSLR frame for quite a long time.
For night time astrophotography even with wide lenses it requires effort, which is why I am adding this new tool.

PS. The beta is open for anyone interested - just pm me your email.
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Old 15-01-2021, 09:59 AM
RugbyRene (Rene)
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One more question. Do the compass/polar align tools take into account magnetic declination or do I need to adjust my heading?

Rene
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  #7  
Old 16-01-2021, 02:58 AM
ecuador
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In general, for iOS, apps can request true north or magnetic north heading from the system, however, they might only get magnetic north back if the, user has particular device settings (e.g. compass calibration turned off), so the app developer has to deal with that.

My app in particular will request true heading from iOS, it will check what it got and if magnetic north was returned instead, the magnetic declination will be calculated for your location using the latest World Magnetic Model and applied.
There's also a display of your magnetic declination in the bubble level / compass tool.

tldr: Polar Scope Align will always use true north (magnetic declination included in the calculation), for other apps it would depend on the particular app.

Quote:
Originally Posted by RugbyRene View Post
One more question. Do the compass/polar align tools take into account magnetic declination or do I need to adjust my heading?

Rene
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