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Digital inclinometers, how much accuracy needed?

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#1 Men2Boyz

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Posted 01 October 2020 - 01:44 PM

Digital inclinometers have been in use for quite a few years now by people here. They are built with accuracies of +/- .1 degree, +/- .2 degrees and +/- .3 degrees. Does having high degrees of accuracy matter or is repeatability a more important factor? Are readouts usually in  .1 degree or .01 degrees increments? Has anyone compared +/- .1 against +/- .3 and found that there is a real difference in ability to locate DSO? Finding non backlit digital inclinometers is becoming more difficult and none of the backlit ones are dark site friendly. What are the features you feel are most important?



#2 halx

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Posted 01 October 2020 - 02:00 PM

The better the resolution the easier to research a particular specimen properties. So I would target a 0.01 device (0.05 is a more typical option). And I would not rely on any side by side comparison of models here, as even between two specimens of the exact same kind you will most likely have a noticeable disagreement.

 

For the accuracy in locating DSOs with an inclinometer the king is the star chart which can show you all stars you could possibly see in your particular telescope around your target (e.g. with the full USNO UCAC4 database of stars limited to your instrument's "penetration"). As regardless the resolution and accuracy of your inclinometer you also have the crude Azimuth issue and frequent axes misalignment issues (both can be improved to a good extent using dedicated software, which allows you to re-align on a nearby star for every DSO). So, some star fields recognition is in order anyway, unless you are hunting for M42 and alike DSOs exclusively smile.gif

 

For the darkness adaptation preservation, the obvious option - add a piece of red film over the screen. You can aso cut off the LCD LED track on the PCB or paint the LED head dark red (these LCD screens usually have the LED(s) easily accessible, unlike TFT screens for example). So just disassemble your device and evaluate your options/skills*resources ratio for each.


Edited by halx, 01 October 2020 - 02:15 PM.

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#3 rhetfield

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Posted 01 October 2020 - 02:12 PM

Accuracy and repeatability only need to be good enough to get the target into your eyepiece.  That will of course vary based on your setup.  As an example, I can expect 0.25 deg accuracy on my azimuth and maybe 1 degree on altitude with my setup, but have a 2 deg FOV, so it works.

 

Also consider slop/backlash in your Alt and Az bearings.  I had to take apart my azimuth axis and work on it because there was enough slop in the bushing to add 1 degree inaccuracy to that axis.

 

Finally, have a way to ensure that your inclinometer is zeroed on true level.  Otherwise you really will be off.


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#4 jcj380

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Posted 01 October 2020 - 02:32 PM

Before I got push-to encoders, I used a Wixey. Not sure how accurate it was supposed to be, but it was usually off by up to half a degree compared to what Sky Safari was telling me even after zero adjusting it.

I just noted the difference and added or subtracted it to/from the SS value. It wasn’t super accurate, but it usually got me the target in a low power field. Totally agree with using a chart for identifying field stars to help.

I covered my display with red taillight repair tape - 2 layers.
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#5 halx

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Posted 01 October 2020 - 02:43 PM

Also consider slop/backlash in your Alt and Az bearings.  I had to take apart my azimuth axis and work on it because there was enough slop in the bushing to add 1 degree inaccuracy to that axis.

 

Finally, have a way to ensure that your inclinometer is zeroed on true level.  Otherwise you really will be off.

The former would never work perfect on a real Dob mount without sacrificing its smoothness and steadiness or ease of use, but might be skipped altogether employing the software I've mentioned.

The latter is a bit more tricky than what rhetfield has suggested. E.g. my inclinometer has an integrated bubble level for easy calibration, however, when you mount it on the OTA (standard magnetic base with the V grove) you might realize that the optical axis of the scope has an unknown angle with the OTA side wall at that mounting spot. And it might be random along the OTA as well. The proper software can fix that issue very well. Otherwise, you should use the same mounting spot all the time (I saw folks putting a sticker there), measure that error after each re-collimation, and if sufficient apply it in your mind.


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#6 SonnyE

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Posted 01 October 2020 - 02:55 PM

I have and use a Smart Level head for my setting up. It works to 0.1 degree accuracies.

I basically use it to level my tripod prior of assembly, and any time I want to check inclines.

I originally got it to do set ups in my shop. But it has been invaluable for my Astroimaging as well.

 

I think I prefer to have the best accuracy I can get. I always strive for 0.0° accuracy.

Just like I strive for the best Polar Alignment I can get with Sharpcap.

I consider accuracy a fun challenge.



#7 junomike

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Posted 01 October 2020 - 04:23 PM

IMO they work relatively well for known DSO's you're after however I wouldn't recommend them for finding new (to you) "Faint Fuzzies" as you can't be certain you're actually looking at what's supposed to be there.


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#8 John Fitzgerald

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Posted 01 October 2020 - 04:29 PM

My azimuth circle with digital inclinometer works well enough to get the object in the center third of my finderscope with 5 degree field.  Good enough for me.  Very easy to star hop from there.


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#9 luxo II

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Posted 02 October 2020 - 04:57 AM

There are Clinometer apps for smartphones that resolve to 0.1 degree and can be calibrated... I know it may seem wacky but if you have an old iPhone 4 say that still works, you could install the Clinometer app on that, slap it on your dob with some Velcro or blutack, and you’re good to go.

And it works in all three axes which a simple Clinometer does not.

Best part is the display has nice big digits and you can control the brightness and apply a red filter.

Edited by luxo II, 02 October 2020 - 04:59 AM.

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#10 Jon Isaacs

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Posted 02 October 2020 - 05:11 AM

I have an older Craftsman digital level. I rarely use it but I have experimented with it and sometimes use it for hunting down Venus and Mercury in the twilight.   It reads to +/- 0.1 degrees and in my comparisons on objects using Sky Safari, it seems to be about that accurate.  It takes essentially no time to stabilize, it reads out in near real time. 

 

With a Dob, collimation can be an issue. 0.1 degree over 40 inches is less than 2mm and will not affect the performance if primary axis is off 0.1 degrees but it will affect DSC and GOTO accuracy as well as a digital level. 

 

The digital level is reading the actual elevation angle of the tube so the inherent errors that come from the base being out of level and issues with the bearings are essentially zero.

 

Jon 



#11 jcj380

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Posted 02 October 2020 - 07:54 AM

Somebody posted this trick to zero / horizontal adjust a Wixey:

 

Aim at Polaris ideally or other bright star.  Zero Wixey.  Lower altitude until meter reads negative of star’s alt.  Zero meter again.  You should now be true horizontal.  Check by going back to Polaris.



#12 clearwaterdave

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Posted 02 October 2020 - 08:06 AM

I made this one for my push-to and it works all good.,I have used these to find Venus and Jup in the daytime.,as well as for night gazin.,cheers.,

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#13 Men2Boyz

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Posted 02 October 2020 - 10:31 AM

The responses have been both informative and very creative as I expected from the CN community. It seems that no matter what inclinometer tool is employed, ability to read star maps and developing star hopping skills will be needed to be successful in finding targets. 



#14 S.Boerner

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Posted 02 October 2020 - 12:28 PM

One thing I've always wondered about...

 

The inclinometersI've seen always have a calibrate/zero button.  The problem I see is I don't have a clue if the surface I calibrated it on is really level.  That's particularly true if I'm out in the field in the dark.  Sure I could use a bubble level on my OTA but then the inclinometers would only be as accurate as my bubble levelingtongue2.gif



#15 decep

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Posted 02 October 2020 - 02:05 PM

Unless you are spending a LOT of money on an inclinometer, it is probably better to say that they may be precise to 0.1 degree, but accuracy is probably lower.

 

I would not expect accuracy to be much better than 0.5 degrees in most cases.



#16 Old Rookie

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Posted 02 October 2020 - 02:10 PM

One thing I've always wondered about...

 

The inclinometersI've seen always have a calibrate/zero button.  The problem I see is I don't have a clue if the surface I calibrated it on is really level.  That's particularly true if I'm out in the field in the dark.  Sure I could use a bubble level on my OTA but then the inclinometers would only be as accurate as my bubble levelingtongue2.gif

You zero it out on a bubble level to start.  The Wixey that I use "remembers" level.  It gets me in the ball park.  And you're right, the Wixey is only as level as your eye when you zero it out.



#17 Old Rookie

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Posted 02 October 2020 - 02:12 PM

The responses have been both informative and very creative as I expected from the CN community. It seems that no matter what inclinometer tool is employed, ability to read star maps and developing star hopping skills will be needed to be successful in finding targets. 

That's exactly right.  Even if you're using dsc's like Argo Navis, Sky Commander or Nexus DSC, you still need an atlas or charting software to examine the  area where the telescope is pointing.  Expecially if you're looking for faint galaxies at the limits of your instrument.  



#18 junomike

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Posted 02 October 2020 - 05:53 PM

Somebody posted this trick to zero / horizontal adjust a Wixey:

 

Aim at Polaris ideally or other bright star.  Zero Wixey.  Lower altitude until meter reads negative of star’s alt.  Zero meter again.  You should now be true horizontal.  Check by going back to Polaris.

 

Used this procedure and it works great.


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#19 Ps191

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Posted 03 October 2020 - 04:21 PM

Somebody posted this trick to zero / horizontal adjust a Wixey:

 

Aim at Polaris ideally or other bright star.  Zero Wixey.  Lower altitude until meter reads negative of star’s alt.  Zero meter again.  You should now be true horizontal.  Check by going back to Polaris.

That's a good trick. If you want to be able to tweak setting throughout the night as you observe one cleaver amateur astronomer I seen built an adjustable base for his inclinometer. After rough levelling he'd center a star, look up the current altitude in his favourite program and adjust the inclinometer until it read what the computer said. I wish I could remember his name, he has equipment reviews on YT and lives in North or South Dakota.

FWIW his adjustment was simply two bolts (in homemade base fastened to OTA or mount) perpendicular to OTA and in a line with optic axis. The bolts were 4-5 inch apart. Spring added on each bolt, followed by metal strap with two oversized holes for bolts. Strap held on by windnuts. Magnetic based inclinometer attaches to metal strap which created adjustable altitude in relation to optic axis.



#20 don314

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Posted 03 October 2020 - 07:16 PM

Wixey has several models, The WR365 has a "permanent absolute level setting", and 0.2 degree accuracy & repeatability.  About $40 on amazon.

I'm doing AP on a portable setup, so I use it to set the mount altitude when I change locations, works great for that application.



#21 don314

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Posted 03 October 2020 - 07:21 PM

Note - above is for rough alignment.  I do final PA Using SharpCap



#22 Jon Isaacs

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Posted 03 October 2020 - 09:45 PM

Unless you are spending a LOT of money on an inclinometer, it is probably better to say that they may be precise to 0.1 degree, but accuracy is probably lower.

 

I would not expect accuracy to be much better than 0.5 degrees in most cases.

 

I am not a big user of digital levels but I find the technology intriguing.  I have two, an older Craftsman model that I use for finding Venus and Mercury in the twilight as well as various home uses, measuring the angle of one of our power poles, the pitch of the roof.

 

The Craftsman checks out as being accurate to +/- 0.1°, probably better. This can be determined by "swinging it" on a flat (not level, just flat) and noting the readings. If they're equal but opposite in sign, that's a good measure of accuracy. 

 

Mounting the level on a refractor tube and comparing the level to Sky Safari for a target centered at high mags is also a way to get a feel for the accuracy. The Craftsman does well in this.  I assume the optical axis of the refractor and the mechanical axis are identical or at least parallel. A reasonable assumption for a quality refractor. 

 

It's about 6 or 7 inches long so that good. It reminds quickly, essentially real time. In my mind, it would the ideal level expect that it's light is bright green.

 

Bubble levels can be quite good though one would want to check the level too. In the laboratory I was in charge of, we had a Starrett Master Precision level. It was a simple bubble level that weighed several pounds, one full division was 0.0005 inches per foot.  That's about 8 arc-seconds and it could be read to a rather small fraction of that...

 

Jon

 

This is where the Wixey 365 enters the story. It's not a responsive, not quite as accurate but uses a non illuminate LCD so it's not the problem with ruining ones night vision the craftsman presents.




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