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Guiding with KStars/Ekos/INDI


Gina
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Not sure this is the right/best forum to post this but... 

I have been using the above software/firmware with RPi to run a wide field imaging rig and with a reasonably well set up mount and short exposures I haven't needed guiding.  The last time I used guiding was with Windows software and PHD with OAG.  Now I would like to use longer exposures and not get star trailing.  I don't think I will need very accurate guiding with the widefield rig.  I know there are two ways of guiding - software or ST-4 cable and guide ports on the guide camera and mount.  Would the latter be a suitable option?  I have only used software in the past (PHD) but wondered if the guide ports and cable would offer a simpler solution.  I expect to use a separate guide scope as OAG is not practical with a camera lens AFAIK.

Any advice would be much appreciated.

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so; Guide Camera -> Mount rather than Guide camera -> RPi -> mount ?

ST4 simply says nudge N/S/E/W and the length of pulse is how long the nudge is (the auto guider port on the NEQ6). There isn't any logic or protocol to change speeds etc. If the hand controller decides it's going todo something then it will cause a problem with the tracking. 

Most cameras are simply cameras - ones with an ST4 port simply pass the computer image to the computer, the computer analyses and instructs the ST4 pulses back to the camera though USB. Autoguider cameras that analyse the image inside the camera short cut that - and you'd not need to worry about the computer guiding (it doesn't know about the computer).

INDI has a guider module;

Quote

Ekos Guide Module enables autoguiding capability using either the powerful built-in guider, or at your option, external guiding via PHD2 or ln_guider. Using the internal guiding, guider CCD frames are captured and sent to Ekos for analysis. Depending on the deviations of the guide star from its lock position, guiding pulses corrections are sent to your mount Via any device that supports ST4 ports. Alternatively, you may send the corrections to your mount directly, if supported by the mount driver. Most of the GUI options in the Guide Module are well documented so just hover your mouse over an item and a tooltip will popup with helpful information.

So basically set INGI guider up for internal guider, connect the ST4 ports up and away you go.. you don't need to remove the handset and use the PHD-style dongle to replace the handset controller.

It's not as advanced as PHD2 but more info here: https://indilib.org/about/ekos/guide-module.html

Edited by NickK
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If you have INDI controlling the mount already then I'm not sure there's anything to be gained, and probably more to go wrong, by getting involved with ST4.

What I've done so far is to connect both the imaging camera and guiding camera up to Ekos (you need to tell it which is which and obvious stuff like that) and use the internal Ekos guider to guide the mount directly.  It's worked well enough with the default settings to get round stars on 15 minute exposures with my NEQ6, though my polar alignment is fairly good to start with so it's perhaps not having to work too hard.  My recollection is that you're running a fairly recent version of Kstars etc.  I did find a few issues on earlier releases where things didn't seem to work quite as well as they should, but those do appear to have been ironed out in more recent versions.

The one thing Ekos doesn't do is automated dithering.  For that reason I might find myself moving to PHD in the future, but I'm not feeling a pressing need right this minute.

James

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Thank you both.

I have a selection of cameras I could use for guiding, one complete with lens.  I would need to check which ones INDI supports - pretty sure the ASI120MM-S is supported.  I forget which other cameras I have ATM - they're out in the observatory.  Should be able to plug the guide camera into a USB RPi port or ASI1600 USB hub and add the INDI driver. 

My KStars is Build: 2019-07-02T16:59:38Z, James.  15 minute exposures would be fine and much better than the 4m maximum I'm currently using.  My mount is the EQ8 and virtually the same as the NEQ6 - uses the same driver.  Looks like this should be relatively painless.  Thank you.

Edited by Gina
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I'm using a 120MM-S as a guide camera at the moment.  It works painlessly.  I set it to bin 2x2 and just let Ekos get on with it.

I'm using Kstars 3.3.8+201911300001 (and I think there's a later release that I haven't upgraded to yet), but I believe it was v2 I was having problems with.  The default release even for Mint19 is 2.9.4.

James

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I've used both ST4 and Pulseguiding.

I don't really notice any difference in practice between the two.

If you use pulseguiding, then you are sending the pulses down the same cable that is already connected to the mount.  So it is simpler to connect up.

 

 

 

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24 minutes ago, JamesF said:

I'm using a 120MM-S as a guide camera at the moment.  It works painlessly.  I set it to bin 2x2 and just let Ekos get on with it.

I'm using Kstars 3.3.8+201911300001 (and I think there's a later release that I haven't upgraded to yet), but I believe it was v2 I was having problems with.  The default release even for Mint19 is 2.9.4.

James

Thanks.  What lens or scope are you using for the guiding and what FL for the main imaging?

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I have two rigs running at the same time at the moment.

The first is an 80ED (600mm fl) for imaging without reducer/flattener, with an ST102 (500mm fl) guidescope.

The second is a TS Photoline 72 (432mm fl) with a focal reducer/flattener taking it down to 340mm fl and an ST80 guidescope (400mm fl).

Mostly because that's what I had :)

James

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If you have a suitable camera mount, you could perhaps use a second 200mm lens for the guidescope.  Could make quite a neat package.  I wonder if one of the ones that you've said isn't quite as sharp as the others would be adequate.  I feel sure Olly has said before now that focus isn't hypercritical on guiders, so perhaps the same applies if the lens is not pin-sharp.

James

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Just to add to this I've been using Ekos+PHD2 for quite a while without issue. The PHD2 setup in the Ekos rig is really straightforward - just enable the server, switch the guider to PHD2 in the Ekos profile, and hit connect in the guide tab - there a few edge cases where it can get confused but restarting PHD2 rapidly fixes those and most nights it's trouble-free.

I would say that PHD2's guiding engine seems to do much better than Ekos', but given the relative volumes of effort into each perhaps unsurprising.

If you're using indi_eqmod then just using pulse guiding via that will work great and is definitely the easiest setup to deal with.

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I might try using PHD2 later when I use a telescope for imaging rather than widefield with lenses but only if the Ekos guider isn't up to scratch - using PHD2 adds complication.

25 minutes ago, JamesF said:

If you have a suitable camera mount, you could perhaps use a second 200mm lens for the guidescope.  Could make quite a neat package.  I wonder if one of the ones that you've said isn't quite as sharp as the others would be adequate.  I feel sure Olly has said before now that focus isn't hypercritical on guiders, so perhaps the same applies if the lens is not pin-sharp.

James

I have 3 200mm lenses altogether so I could make up a triple rig with two ASI1600 cameras for imaging and the ASI120 as guide camera.  Yes, I am aware that good focus/resolution isn't needed for guiding and that slight defocussing is beneficial.  I've done that in the past with my guide camera.

Edited by Gina
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I can't recall the pixel size of the X2.  If you're guiding with a short focal length perhaps the one with the smaller pixels would be better?  No reason not to try them both from a software point of view though.  The 120MM-S might perhaps be easier to mount on the lens unless you can get the correct T2->C thread connector in a suitable length for the Lodestar (to achieve focus).

James

Edited by JamesF
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I use PHD2 with an ASI120mm coupled to a Skywatcher 9x50 finder scope which is 180mm FL  - so if you do decide to go back to PHD2 one of your 200mm scopes will work great. I have used it with both ST4 and just pulse guiding. The latter is the easier way to go as ST4 was always going into recalibration if you pointed the scope somewhere else.

So many ways to achieve good guiding nowadays

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16 minutes ago, JamesF said:

I can't recall the pixel size of the X2.  If you're guiding with a short focal length perhaps the one with the smaller pixels would be better?  No reason not to try them both from a software point of view though.  The 120MM-S might perhaps be easier to mount on the lens unless you can get the correct T2->C thread connector in a suitable length for the Lodestar (to achieve focus).

James

X2

Quote

Pixel size: 8.2uM x 8.4uM, Image format: 752 x 580 pixels

ASI120

Quote
Resolution 1.2Mega Pixels 1280×960
Pixel Size 3.75µm

Looks like the ASI120 would be better for a widefield rig.  Maybe the SX for telescopes with OAG as I have used that setup before.  The OAG has the right thread.  I have also used a separate finderscope as guidescope before.

Edited by Gina
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19 minutes ago, Gina said:

I have the Starlight Xpress Lodestar X2 Autoguider.  Wonder if this would be better than the ASI120MM-S

I doubt that it matters much.  You will be well within recommendations with either.   The Lodestar will have a slightly bigger FOV, but that won't be an issue with either camera.  I'm using a 120mc on an ED80  (600mm F7.5) and I never have a problem finding a guide star. ( I usually guide with a 2s exposure time.)

If it is much easier to connect up, and focus, one camera, then I would use that.

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28 minutes ago, Gina said:

I have the Starlight Xpress Lodestar X2 Autoguider.  Wonder if this would be better than the ASI120MM-S

That's what I use connected to a SW Finder telescope 190mm focal length. My image scope is a SW ED80 of focal length 510mm when using the 0.85 focal reducer/flattener. I only use ST4 guiding.  I have found KStars/EKOS/INDI works fine guiding this set up most of the time.  I used to use PHD in Windows but since guiding is included in KStars I use the internal guider. It is less sophisticated than PHD but it works. 

I particularly like the plate solving alignment routine in KStars which I believe has improved my polar alignment considerably and hence my guiding. I get a guiding accuracy of about 0.75" RMS most of the time with the occassional wobble due to extraneous factors like wind shake etc.  I'm satisfied with the roundness of my stars with 5 minute exposures, but I suspect some connoisseur astrophotographers wouldn't be.  

Hope that helps and good luck with it. 

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15 hours ago, Gina said:

All this seems so much easier in KStars/Ekos/INDI with RPi. than it was in Windoze!!  The more I use it the more I'm impressed!  😀

Amazing to think that something the size of this can do everything including astrometry!

B7B110AF-762F-44C5-AFD1-4F5C4DA285FA.thumb.jpeg.e2cf6727fa65d60d6f0e02e6069f154b.jpeg

Just playing around - the build on this is 2016 and the first 64bit self compilation of many INDI/Kstars things.. so I’m seriously considering updating it to correct many package errors stopping upgrades etc.

 

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I use the Stars/Ekos on my RPi4 and it just works.  Platesolving, GoTo, Focussing, Filter Wheel control, Target selection and image Sequencing and Guiding both using PHD2 or the inbuilt guiding tool.

The developers keep adding new features on a regular basis like the new linear focussing option this last update, or the improved image viewer.

The planetarium part in KStars is just as easy to use as Stellarium or Cartes de Ciel.

Cant fault it. 

Making use of the USB3 ports increased speed for accessing the file system on a SSD makes huge difference to its performance. 

Edited by wornish
typos
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The C2 uses eMMC for system drive (16GB) so ~12sec power-ready but only has usb 2.0 - fast enough for an SSD image store. With passive cooling - no vibrations too. I use UBECs to convert from 12V to 5V - small but powerful enough :)

Like the RPi it does everything in a box :)

Just trying to pick up courage to reinstall from scratch! Will probably do that tomorrow.

 

Edited by NickK
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I second the use of  eMMC modules, my main Indi systems (Odroid XU4, Rock64 & RockPro64) all use them, sooo much quicker to boot\load\save etc...  they are all running Ubuntu 19.10 \ Mate x64  & Indi\Ekos.

I run everything locally, on the SBC's, & remote into them using XRDP …..

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Just a question on skywatcher finder 9x50 what is the correct FL as I see two different lengths in this post and does it make any difference for PHD2

Skywatcher 9x50 finder scope which is 180mm FL and

SW Finder telescope 190mm focal length

Does anyone know the correct FL or I can enter either in PHD2 and 10mm is neither here or there. I use mine with a ASI120mm does an exact FL improve guiding?

Regards

Andy

 

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