Mobile phone finderscope mount - any good?

[MortonH]

I noticed this new product on myastroshop. It allows you to mount your mobile phone onto a Vixen/Synta style finderscope dovetail.

http://myastroshop.com.au/products/details.asp?id=MAS-017G1


I've often wondered how well my mobile phone would work as a digital setting circle. Has anyone tried this or similar? From what I've read there can be challenges with the scope/mount causing magnetic interference, plus the question of the accuracy of the phone's sensors in the first place. My phone is a Galaxy S3.

I'm wondering how well this might work with a small scope on an alt-az mount (even a camera tripod) for finding some of the brighter deep sky objects (or Comet Lovejoy).

[Sconesbie]

Looks interesting. I've been looking at ways I can mount my phone on my collapsible dob somehow so I can use Stellarium or other programs. I've found that if I rest my phone on the scope, it doesn't work properly and sends it a bit wayward (much like a magnet does with a compass).

I've even started to play with ideas using Lego to create a phone holder but the flat surface of the lego doesn't sit on the scope very well.

[omegacrux]

That's a neat idea to use with sky-eye
shame my mobile won't support a lot of those app's !

David

[Regulus]

I have been thinking about something like this for a few years and am glad to see it.
However, I have found in the interim, that laying my phone along the tube with bluetac, and using Skyeye in it's Mobile setting, it makes a great push-to, once you do a two star alignment with the software.
Still...... might end up with one. For $30, sheesh.
Trev

[brian nordstrom]

:shrug: I wonder what sort of havoc the metal of the scope , mount and tripod would impart on the GPS , I know my compass in my phone wont work properly when its to close to my scopes ??? .
Great idea and if someone tries one and reports positive feedback I might grab one as well.
Brian.

[LewisM]

I cannot get my GPS/Compass to work a damn near my rig. Points East when pointed at the SCP. :screwy:

Only app I use to any extent is the digital inclinometer app.

[Camelopardalis]

If your mount isn't steel you might be OK...

My phone can't be trusted within about 6ft of my EQ6, admittedly it's a big heavy lump :D

[Mokusatsu]

My experience using an iPad 3 + several mobile apps is the pointing isn't all that great, even without any adjacent metal objects. It is frequently off enough to make it useless as a pointer.

That said, I've done design sketches to make a mount for it on my binocular paralellogram mount, sitting next to the binoculars and coupled with a parallelogram linkage to align them. If I get around to it I'll post a review in the ATM section of whether or not it was any good in practical use.

[julianh72]

SkEye works fine using my Nexus 4 phone or Nexus 7 tablet when attached to my 90 mm Mak - the OTA is aluminium, so not too much steel to upset the compass. It works fine if I just strap the phone or tablet straight onto the OTA with rubber bands, but I also bought a cheap clone "GorillaPod" style tripod on eBay (the ones with the bendy legs) , which has the advantage of being able to mount the phone display in the most convenient orientation.

The nice thing about SkEye is that it allows you to use the pointing function with your phone / tablet mounted in any convenient orientation, not just perpendicular to the display, and this makes it a perfect app for mounting your phone as a Push-To guider.

My suggestion: download the SkEye app and try it with your phone strapped straight onto the OTA - if it looks promising for you, THEN investigate whether you need a more sophisticated mount.

[Mokusatsu]

Thanks for the tip with Skeye, I've installed the free version on my Galaxy phone and it seems pretty good.

Is the Pro version one of those apps that has a fluctuating price and it might be worth my while waiting a few weeks for it to go on special for $1, or is it always $6?

[Mokusatsu]

I glued some scraps nto the side of my dob to make a holder for my Android tablet. I have not tried it on stars yet, last night I was clamping this for strong pva joins. Will let you guys know about its pointing accuracy after tonight.

[Mokusatsu]

Not very impressive... :(

As a goto guide it was pretty lousy in practice I'm afraid. After aligning it with a number of stars and objects I tried to find some stuff with it and it was always quite off.

About the only object I was able to goto and get it in the field of my lowest power eyepiece was M42, and that was only after clearing all alignments and then re-aligning on Rigel and Betelgeuse.

My mount has very little metal at all in it. There is the focuser, the mirror cells, spider and some screws. It's otherwise all wood. I wonder if my observing chair, which has a steel frame, might have interfered, or my colourbond steel shed which was 5m away... but if it won't work in the vicinity of these then it's really not all that much use to me.

This was with an LG G Pad tablet.

I'll give my Galaxy S3 phone a go next. Hopefully its performance will be better.

It's a shame, I was pretty stoked about the possibility of having cheap goto on my old dob.

[skysurfer]

The problem is that the whole setup is limited by the low accuracy of the inclinometer of the cellphone or tablet.
Horizontal (the compass) it is dramatically inaccurate it can be serveral degrees off.
Vertically it is better but no more than 1 degree. The inclinometers used in construction are way better, to 0.1-0.2 degrees. I have such a one for using on my altazimuth scopes (8cm tabletop refractor and 40cm Dobson).
I tried Skeye on my Galaxy Note 2 but it was rather useless. Not Skyey but the hardware of the cellphone.

[Mokusatsu]

There is some mention in the documentation of support for Bluetooth hardware digital setting circles. Are they significantly better than this and how much do they cost?

Edit: I found the cost, BETI is specifically mentioned as supported by this app, and that device costs $130+ GST. http://www.astrodevices.com/products/BETI/BETI.html

Still... are these any good? Can I realistically expect to be able to align on a couple of stars and then put any object I like into at least a low power eyepiece with an otherwise blind GOTO?

[OzEclipse]

Steel OTA's will cause problems as will the stepper motors if your mount is motorized. Stepper motorscontain very powerful permanent magnets that will throw the compass off.

There is a gps based device sold by Celestron now discontinued -
http://www.celestron.com/browse-shop/uncategorized/skyscout-personal-planetarium

Andrews and others are still advertising it so they may still have them in stock.

[julianh72]

It might vary with the device, and it may not work for everyone. It may be very tricky if the OTA is made of steel, but a lot of users get good results if you can mount the phone a 100 mm or more from the steel tube.

It certainly makes a difference if you calibrate the compass beforehand. (Turn on the compass, then wave the phone / tablet in a large figure of 8 a couple of times is the usual way.)

I regularly and repeatedly get better than 1 degree accuracy in both azimuth and Altitude with my Nexus 4 phone strapped onto my 90 mm Mak on an EQ2 mount. (I use the compass and inclinometer of my phone to first get a polar alignment of better than 1 degree, and then use SkEye to help me find my targets.) The Mak has an aluminium tube, which certainly helps, but the phone is only mounted about 200 mm from the mount which has a lot if steel, but doesn't worry the phone's compass.

One thing that I really like about SkEye is that you can realign on a nearby target star, and then you can get surprisingly good local alignment when you're chasing targets in the general vicinity of your latest alignment star.

[Wavytone]

Morton,

The only decent solution is to use a mount with encoders and a Sky-Fi gadget, so you can hold a smart phone or tablet wherever it suits you, and have it show where the scope is pointing.

I tried both Sky Safari and the Theodolite app on my iPhone 4 and iPad 3 and while its a nice idea, it has a few problems.

1. To be any use as a finder you need accuracy of the order of ~ 1 degree, or better. Otherwise you're wasting your time.

2. Using the earths magnetic field to measure azimuth is not good enough for a finder. It's good enough for a compass as a crude navigation instrument, but not good enough for astronomy. The magnetic field has an offset to true north, this has to be compensated for. Unfortunately this offset is not constant, it varies according to your location and it varies with time, and it is also screwed with right royally if there is an aurora - this will cause a noticeable shift in the earths magnetic field. This variability is both unpredictable and sufficient to make software-based finders unpredictably unreliable...

3. Altitude. The iPhone/iPad sensors are good enough for altitude measurements, the resolution seems to be about 0.1 degree, however you must calibrate whatever software you're using.

4. It is extremely inconvenient, ergonomically. I attached my iPad to the front of my scope to see if it would figure out where the scope is pointing, and whether it was useable as a finder. Unfortunately it suffers from a very obvious problem - near the horizon its OK but at high elevation I rapidly got a bad crick in my neck from trying to get under the damn thing and look up at it.

In conclusion this idea doesn't work and when there is a far better solution at a reasonable cost I don't see why anyone would bother: Using a mount with encoders solves the accuracy problem - it's trivial to fit encoders that measure to 0.1 degree. Using Sky-Fi or similar to integrate the mount and encoders with a smartphone or tablet such that you can hold it anywhere you like solves the ergonomic problem as well.

[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. I am not aware of any comparable iOS app. (But SkySafari is my pick of the "planetarium apps" for all other functions - and is available on both iOS and Android.)

1. I get better than 1 degree accuracy on both axes with SkEye. It has the ability to do a local "re-calibrate", so that you use SkEye to navigate to an easily identifiable target star in the general vicinity of where you are planning to observe, then "align" it to that star, and then you get better than 1-degree precision over that whole field of sky (60-degree range, say). When you swing to a new quadrant of the sky, if the alignment isn't good enough (it generally is!), just realign it to a new local star and carry on.

2. SkEye includes the local magnetic deviation to automatically know True North from Magnetic North, based on your location. (In fact, any decent smartphone compass should be able to do this. Compass deviation variation with time occurs over a scale of years , not minutes or hours, so a simple look-up table is all that is required to get better than 1-degree precision.)

3. Calibrate the compass by waving the smartphone in a figure-of-8 a couple of times before relying on it for accurate Azimuth control, but then it works just fine.

4. Ergonomics - this is where SkEye is really clever. Most "planetarium" apps in "compass" mode show you the sky view "straight through" the smartphone, perpendicular to the back of the phone. This means that to use the smartphone as a finder, you need to mount it EXACTLY perpendicular to the OTA. With SkEye, you mount the phone / tablet firmly onto your telescope in any convenient position / orientation - e.g. strapped straight onto the tube (as long as it isn't made of steel), or mount it at a convenient offset using a bracket of some sort. Then you tell SkEye what you are actually looking at through the telescope, and it works out the offset angles between the phone's orientation and the telescope's orientation. When you swing the telescope in azimuth and / or altitude, you swing the phone through the same differential angles, so SkEye can work out how much you have moved on both axes, and what you are now pointed out. Simple, but very clever, and as I said, I think it is still a unique feature.

[julianh72]

Sorry, I don't know whether it is ever on special - like all Android Apps, once you have purchased it, the Play Store shows it as "Already Owned" and doesn't display the purchase price any more.

I paid for the Pro version not so much because I "need" the extra features, but because I think the app is good enough that the developer deserves to be paid for his efforts. (I'm one of those strange people who is actually happy to pay a reasonable price for useful software - I have even been known to donate to "Beer-ware" and "Postcard-ware" app developers!)

[julianh72]

I have two telescope mounts - an EQ-2 with a motor-drive, and a Celestron SLT computerised Go-To mount, with a Bluetooth controller plugged into the handset.

I can control the SLT mount with SkySafari 4 Plus on my handheld phone or tablet, and this is certainly my preferred mounting, but using SkEye on my phone on my 90 mm Mak mounted on the EQ-2, I have both a computerised GoTo telescope and a computerised Push-To telescope. (Being a motorised EQ mount, once I have aligned the mount and found a target using SkEye, the motor-drive will easily hold it in view for 30 minutes or more.) This lets me use both telescopes at once - and the Mak / EQ-2 combo is a really handy grab'n'go portable telescope. (And SkEye will even work if all I have is a really basic light-weight Alt-Az tripod.)

SkEye is a free app if you have an Android phone (or about $6 for the Pro version), and I can mount my phone to the telescope with nothing more complex than a rubber band - but I lashed out and spent $5 to get a cheap "gorilla-pod" type flexible tripod which lets me mount the phone at a more convenient viewing angle:

http://julianh72.blogspot.com.au/2014/08/a-simple-push-to-controller-for-your.html

All-in-all, a much cheaper option than encoders and Sky-Fi, and well worth trying before spending a lot of money on a more sophisticated solution.

[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.

[julianh72]

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]

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]

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/support/faq/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]

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

Bill Tschumy replied to my question:



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

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]

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

:D

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]

Sorry to keep coming back at you :D 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]

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! :D 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]

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]

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]

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]

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

[julianh72]

Yes, it will be more accurate.

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

[michaellxv]

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]

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_for_phone_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/350422-the-evolution-of-a-lightbridge-16/page-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]

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]

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

[michaellxv]

Who reads the user manual :shrug:

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]

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]

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.