Mobile phone finderscope mount - any good? - Page 2

Steffen · #21 05-01-2015, 05:39 PM

Quote:

Originally Posted by julianh72

SkEye is an Android-only app, so won't work for you, but for Android users, it is vastly superior as a telescope-mounted finder tool compared to SkySafari etc, because of how it works.

Apparently not, since the four points you're making apply likewise to SkySafari.

Except maybe for point number one. I think it is illusory to expect better than 1 degree accuracy from a magnetic compass, it is just swayed too easily by nearby disturbances and loses accuracy when the scope is pointed up high.

FWIW, I've strapped my iPhone running SkySafari to the Dob tube once (it does not have to be perpendicular to the OTA), but the compass accuracy made the whole setup unreliable, esp since the tube is made from steel. It was good enough if I tried finding something faint after first aligning on a nearby star, but on a whole I found it too much effort for too little utility.

Cheers
Steffen.

julianh72 (Julian) · #22 05-01-2015, 05:59 PM

Quote:

Originally Posted by Steffen

Apparently not, since the four points you're making apply likewise to SkySafari.

Except maybe for point number one. I think it is illusory to expect better than 1 degree accuracy from a magnetic compass, it is just swayed too easily by nearby disturbances and loses accuracy when the scope is pointed up high.

FWIW, I've strapped my iPhone running SkySafari to the Dob tube once (it does not have to be perpendicular to the OTA), but the compass accuracy made the whole setup unreliable, esp since the tube is made from steel. It was good enough if I tried finding something faint after first aligning on a nearby star, but on a whole I found it too much effort for too little utility.

Cheers
Steffen.

Steffen,

As far as I can tell, in SkySafari for Android (I don't know about the iOS version), if your device has a compass (pretty well all Androids do), you can't use the Compass / Gyro to get a live-sky view in any orientation other than "straight through" the screen. If I orient my device "screen downwards" and switch to "Compass" mode, I get a view of the ground, not the sky. The Help file does talk about how it might work using only the gyros if you have a device with no compass (iPod Touch and Kindle Fire are mentioned), but I haven't ever used one.

You could be right about the issues of getting better than 1-degree ABSOLUTE bearing precision because of compass interference from nearby metallic objects, etc, but the point is: SkEye doesn't NEED to!

One you have mounted your phone to your telescope, SkEye gets a local 3-axis compass reading which includes local interference from the mount and OTA etc, but once you have aligned on a target star, it is only using the CHANGES in the compass reading to determine CHANGES in azimuth - and it can do this to better than 1-degree precision. It doesn't matter if your initial compass reading is out by 10 degrees - a 1-degree change of azimuth will still generate a 1-degree change on the 3-axis compass reading, and it is this CHANGE which SkEye uses for targeting your telescope. (3-axis compasses work equally well in any orientation after doing the "calibration dance", so don't suffer from issues when you are close to the zenith.)

Steffen · #23 05-01-2015, 09:26 PM

Quote:

Originally Posted by julianh72

f I orient my device "screen downwards" and switch to "Compass" mode, I get a view of the ground, not the sky.

You use the Gyro button (two intersecting ellipses) for that, instead of the Compass button.

Speaking of which, I can't find the Gyro button on my iPhone 6 running Sky Safari 4.3.0.1. No idea where it went. It used to be right next to the Compass button on my iPhone 5 (that's the one I strapped to the Dob).

I know for sure that the iPhone 6 has a six-axis gyro, just like the 5. I wonder whether this is a bug in iOS 8 or Sky Safari 4, but I'm going to find out...

Cheers
Steffen.

julianh72 (Julian) · #24 06-01-2015, 12:40 AM

Quote:

Originally Posted by Steffen

You use the Gyro button (two intersecting ellipses) for that, instead of the Compass button.

Speaking of which, I can't find the Gyro button on my iPhone 6 running Sky Safari 4.3.0.1. No idea where it went. It used to be right next to the Compass button on my iPhone 5 (that's the one I strapped to the Dob).

I know for sure that the iPhone 6 has a six-axis gyro, just like the 5. I wonder whether this is a bug in iOS 8 or Sky Safari 4, but I'm going to find out...

Cheers
Steffen.

I think you might have been using a much older version of SkySafari, or possibly using it on a device with no compass, such as an old iPhone or iPod Touch.

According to the current FAQ http://skysafariastronomy.com/suppor...skysafari.html :

11. The compass is not working! How do I make your apps show me the sky as I move the phone around?

First, make sure you have an iPhone or iPad with a compass. The original iPhone, iPhone 3G, and iPod Touch all lack a compass, so you won't be able to do this. At most, you'll be able to see the stars move "up and down" as you tilt the phone vertically. If you know where north is on the horizon, you can swipe the screen horizontally to "dial-in" the correct view.

22. Can SkySafari align my telescope for me? Can it use the iPhone's GPS to tell me where the scope is pointing?

No. GPS can tell you very accurately where on Planet Earth you and your telescope are located. But it can't "auto-magically" tell you what direction your scope happens to be looking toward. Similarly, your iPhone has no way of knowing the orientation that you may have chosen when you plopped your telescope mount down on the ground. Our app has to rely on the coordinates reported by the telescope mount controller.

Steffen · #25 06-01-2015, 11:46 AM

Quote:

Originally Posted by julianh72

I think you might have been using a much older version of SkySafari, or possibly using it on a device with no compass, such as an old iPhone or iPod Touch.

No, it was an iPhone 5, but probably running Sky Safari 3.

Bill Tschumy replied to my question:

Quote:

In SkySafari 4, the gyro button was removed because we felt it was no longer needed. We now make use of Apple's "sensor fusion" in which reading from the gyro are automatically used to stabilize and smooth out the compass readings. The only reason the gyro button was there in addition to the compass was for cases where the compass was not working properly.

The gyro button is still there on the iPod touch which doesn't have a compass.

So, there goes the ability to simply strap the phone to the tube...

Not a great loss IMO, those phone sensors are not really accurate enough for this to work reliably. You'd have to re-sync all the time.

Cheers
Steffen.

julianh72 (Julian) · #26 06-01-2015, 01:14 PM

Quote:

Originally Posted by Steffen

Not a great loss IMO, those phone sensors are not really accurate enough for this to work reliably. You'd have to re-sync all the time.

Unless you use SkEye on Android, which actually works very well indeed!

Sorry to keep hammering on at you Steffen, but your experience is with a different product, which was never specifically designed with Push-To functionality as a design objective. (I know this, because I have also spoken to Bill Tschumy about getting this functionality added to SkySafari, and he has indicated that he has no plans to do so.) Push-To was a primary design objective of SkEye right from the start of its development (since a least 2011) - and it works!

No, it's not as good as a computerised GoTo mount, or PushTo encoders etc, but it's a heck of a lot cheaper, and can be used on just about any telescope / mount. My advice would be that anyone with an Android phone or tablet who is looking at options for computerised control of their manual telescope mount should take a look at SkEye - what have you got to lose?

I find that realignment in SkEye is only needed when I point to a completely different part of the sky (more than 60 to 90 degrees shift say), and even then, it is typically only a degree or so out, and takes one quick tap to get a local realignment, which is then good for that whole quadrant of the sky. I generally don't need to worry about realignment if I am viewing within a single quadrant for an hour or more.

(And I'm not alone in this - thousands of happy down-loaders, 4.3-star average rating, and many of the 5-star ratings and the SkEye Pro reviews in particular specifically report the Push-To functionality.)

Steffen · #27 06-01-2015, 03:29 PM

Quote:

Originally Posted by julianh72

I find that realignment in SkEye is only needed when I point to a completely different part of the sky (more than 60 to 90 degrees shift say), and even then, it is typically only a degree or so out

Sorry to keep coming back at you

but that's what I'm talking about. Being a degree off after a 60 degree slew is not acceptable for most purposes, in my opinion (and Bill Tschumy's opinion apparently). The problem is not the software, but the sensors. They just aren't good enough (yet).

Cheers
Steffen.

julianh72 (Julian) · #28 06-01-2015, 03:57 PM

Quote:

Originally Posted by Steffen

Sorry to keep coming back at you

but that's what I'm talking about. Being a degree off after a 60 degree slew is not acceptable for most purposes, in my opinion (and Bill Tschumy's opinion apparently). The problem is not the software, but the sensors. They just aren't good enough (yet).

Cheers
Steffen.

But the point is - I (and other SkEye users) get a LOT better than 1-degree repeatable precision when working within a quadrant of sky, and if I do get a degree or so of alignment error when changing quadrants, it's a trivial one-tap exercise to re-align locally on a bright star, and you're back on better than 1-degree precision again.

The software and sensors are PLENTY good enough for my visual use - despite Bill Tschumy's opinion!

They may or may not be good enough for other people's expectations, but as I point out - it's a zero-cost experiment if you have access to an Android phone or tablet. No, it won't be as accurate as a good set of encoders on a Dob, or a well-aligned computerised GoTo mount, but it can be a whole lot easier than having no targeting assistance at all for a lot of novices.

My targets consistently land well within the FoV of a low to medium power eyepiece (yes, even when doing "big" jumps from one quadrant to another, which is the only time the "big" 1-degree errors creep in), from where I can centre them visually (if necessary), and then switch out to higher power as required.

(Seriously - please don't pre-judge SkEye's capabilities for PushTo targeting based on the limitations of SkySafari in this one respect. SkySafari is still my preferred app for all other functions.)

Mokusatsu (Australia) · #29 06-01-2015, 07:20 PM

Well, it was terrible for me. Couldn't get better than 5 degrees of precision. That's a lot of sky!

I was using an LG Gpad 8.3. I'm not sure how sensor precision stacks up in my tablet vs others, so I can't comment on its performance otherwise.

My telescope is all wood, the only magnetic stuff in it is a small amount of steel in the eyepiece and focuser and the screws. We can't blame the scope!

Travis

Regulus (Trevor) · #30 07-01-2015, 07:32 AM

Mokusatsu,
Can I ask why you mounted the phone on the side of the scope? I would have thought flat along the top would be preferred.
I mount mine flat on the top of a SK 150Mak and I get a reasonable return. Although you do need to do a quick alignment when you move an appreciable distance across the sky from you initial alignment. This is quite quick taking only a minute, or two at the most, and there are usually a few bright stars that can be used in the new area you want to look at.
Always calibrate the phone because it may have been effected by magnetic fields throughout the day, or since you last used Skyeye.
Watch this on calibrating the compass. It doesn't need huge figure-8 movements as I once thought. (the video is 3 minutes): https://www.youtube.com/watch?v=k1EPbAapaeI
I use a Samsung Galaxy Note II. As mentioned in the thread, some hardware is better than others and, although I don't know where mine falls on the scale of things, it gives a good result.
You can see in the video link that an LG model just won't calibrate but I suspect it may not have the sensors at all.

creeksky (Pete) · #31 07-01-2015, 09:07 AM

This is very brilliant I have SkyEye on my Galaxy 1 phone,all I need now is a telescope

Would a mobile phone car mount( the ones with a suction cap )work to stick onto the scope?

Mokusatsu (Australia) · #32 07-01-2015, 03:06 PM

Why would flat along the top be preferred? Having it on the eyepiece face of the scope makes it easy for me to align on stars for example, when I have Sirius in the middle of the field I can hit the button to say it is centred, without having to lean over my scope and possibly move the telescope with my belly!

Also, putting it close to the alt-bearings did less to unbalance my scope.

I just did a side by side comparison between my iPad 3, my LG Gpad 8.3 and my Galaxy S3 phone, running compass apps.

No two devices agreed with each other very closely, but the LG was clearly the outlier. Its response to rotation was also less than reassuring. I can see how Skeye would get a little confused if those inputs are what it's working on! According to specs lists, the G Pad has all of the standard Android sensors including compass, gyro and accelerometer. What the specs don't seem to mention is that these sensors are apparently rubbish!

I will trial my S3 and report back on how it goes. I think though the best long term plan would be for me to spend the $143 and purchase BETI bluetooth DSCs, which would be more accurate than any phone.

Travis

Quote:

Originally Posted by Regulus

Mokusatsu,
Can I ask why you mounted the phone on the side of the scope? I would have thought flat along the top would be preferred.
I mount mine flat on the top of a SK 150Mak and I get a reasonable return. Although you do need to do a quick alignment when you move an appreciable distance across the sky from you initial alignment. This is quite quick taking only a minute, or two at the most, and there are usually a few bright stars that can be used in the new area you want to look at.
Always calibrate the phone because it may have been effected by magnetic fields throughout the day, or since you last used Skyeye.
Watch this on calibrating the compass. It doesn't need huge figure-8 movements as I once thought. (the video is 3 minutes): https://www.youtube.com/watch?v=k1EPbAapaeI
I use a Samsung Galaxy Note II. As mentioned in the thread, some hardware is better than others and, although I don't know where mine falls on the scale of things, it gives a good result.
You can see in the video link that an LG model just won't calibrate but I suspect it may not have the sensors at all.

julianh72 (Julian) · #33 07-01-2015, 03:49 PM

Quote:

Originally Posted by Mokusatsu

I will trial my S3 and report back on how it goes. I think though the best long term plan would be for me to spend the $143 and purchase BETI bluetooth DSCs, which would be more accurate than any phone.

Travis

Yes, it will be more accurate.

Don't forget you need to buy and install a pair of encoders as well.

michaellxv (Michael) · #34 07-01-2015, 04:28 PM

Quote:

Originally Posted by julianh72

One you have mounted your phone to your telescope, SkEye gets a local 3-axis compass reading which includes local interference from the mount and OTA etc, but once you have aligned on a target star, it is only using the CHANGES in the compass reading to determine CHANGES in azimuth - and it can do this to better than 1-degree precision. It doesn't matter if your initial compass reading is out by 10 degrees - a 1-degree change of azimuth will still generate a 1-degree change on the 3-axis compass reading, and it is this CHANGE which SkEye uses for targeting your telescope. (3-axis compasses work equally well in any orientation after doing the "calibration dance", so don't suffer from issues when you are close to the zenith.)

Julian,

I tried SkEye on my lightbridge (lots of metal) without much success. This post suggests I should retry? I had it mounted on the aluminium struts, is this going to be far enough away from top and bottom sections? I may have to look at something better than velcro to hold it.

If I can get FOV accuracy in a 30mm EP that's better than not using it.

julianh72 (Julian) · #35 07-01-2015, 05:36 PM

Quote:

Originally Posted by michaellxv

I tried SkEye on my lightbridge (lots of metal) without much success.

Have you read the user guide?
http://lavadip.com/skeye/media/skeye_user_manual.html

Did you check out the suggestions for mounting your phone onto your scope?
http://lavadip.com/3081_skeye__ideas...ne_mounts.html
There's a link to a post with photos by a Cloudy Nights member who attached his phone to a 16" LightBridge to use SkEye here:
http://www.cloudynights.com/topic/35...4#entry4540597

Did you calibrate the compass before attaching your phone / tablet to your telescope? (This is essential!)

Did you have Sensor Fusion turned on? Did you experiment with different Sensor Fusion Sensitivity settings? (My Nexus 4 and Nexus 7 work fine using "Normal" sensitivity.) Did you see the warning that "Higher sensitivity may reduce lag but may increase jitter"?)

Did you have Indirect Mode turned on?

Did you have Magnetic Field Warning turned on? Did it alert you to any problems with abnormal magnetic fields? Does your telescope have a steel tube / truss, or is it non-magnetic? If so, you may need to find a different way to mount your phone onto your scope, to get it further away from the magnetic metal components.

If you've been through all of this, and can't get good results, it may just not work for you, your phone, and / or your telescope.

Regulus (Trevor) · #36 07-01-2015, 06:41 PM

I think that having it vertical to the direction of view might upset the operation of the compass/gyroscope/inclinometer and that flat along the top of the tube would work better since it is face up and flat the way it is when u hold it. May not be necessary and just my wrong view of things though.
I just bluetak mine to the top of the tube, but being a mak this is not inconvenient to use it this way.
Interesting to note too that in the video link I posted, an LG failed miserable at calibrating the compass.
Here's an interesting idea on mounting Skyeye on a tube on a Galaxy Tab
https://www.youtube.com/watch?v=B2k_oWac-pk

Julian's comment about Sensor Fusion is also important. I found Normal to be far better than more sensitive setting.

Trevor

Regulus (Trevor) · #37 07-01-2015, 06:46 PM

Just discovered the Youtube link I posted is on the Lavadip link Julian posted too.

michaellxv (Michael) · #38 07-01-2015, 10:37 PM

Quote:

Originally Posted by julianh72

Have you read the user guide?
http://lavadip.com/skeye/media/skeye_user_manual.html

Who reads the user manual

I will take a look at your suggestions and see how I go.

Yes, I do get the abnormal magnetic field warning, I assumed it was from the metal on the telescope.

AG Hybrid (Adrian) · #39 08-01-2015, 01:30 AM

Interesting read. Seems like a lot of trouble mounting it on your scopes. I place my phone on a stalk I installed on the side of my base. I point my scope at targets while looking at my phone. I would find it too distracting while observing if it was even at chest height, let alone near the focuser.

Mokusatsu (Australia) · #40 08-01-2015, 02:10 AM

So, I tried again with my Galaxy S3 phone. The results were a little better, but I still had to search around for an object after guiding to it. It was not good enough to put an object into my lowest powered eyepiece even if I'd aligned it to a very nearby star.