Guiding with KStars/Ekos/INDI

[wimvb]

@fozzybear: I believe the correct fl is 180 mm. At least that's what I found when googling the subject.

@Gina: I use both the internal guider and phd2 for guiding with a ASI120MM-S and oag. Either works, but I find phd2 more transparent. It's easier to see what's going on, and there are more guide algorithms to choose from. I particularly like ppec (predictive pec). It also has more analysis functionality, should guiding go wrong. The built in guider is based on lin_guider, very basic and more push here dummy than phd. 

 

[alacant]

21 minutes ago, wimvb said:

Either works, but I find phd2 more transparent.

+1.

The main issue with the EKOS internal guider -as with st4- is that you have to calibrate for each new sky position and after a meridian flip: more to go wrong.

I use EKOS with an indi connection to the mount and PHD2 to guide; calibrate once and forget about it.

Or try both. In EKOS it's easy to setup two profiles. One for internal guiding and one for PHD2.

HTH

 

Edited January 20, 2020 by alacant

[wimvb]

... and setting up in Ubuntu is easy. Just connect to the ppa and sudo apt install.

[Gina]

Just realised my ASI 120 is the colour version and I guess I should have the mono version or the ASI 120MM Mini which I could use with my Baader Click-Lock micro-focuser.

Comments please.

[Avocette]

I also have the 120MC-S also and use it successfully with the SW 50mm Evoguide scope. I have used it binned 2x2 which I presume means that the software is effectively summing a cell of RGGB pixels, and also 1x1 both quite effectively (as far as I can tell). So far I've used the Indi internal guider but this thread is encouraging me to try PHD2.

[JamesF]

I think quite a few other people use colour cameras as guiders, too.

James

[don4l]

I'm using the 120MC with PHD2.  I've no idea if the fact that it is colour has had any effect.  It just seems to work.

[NickK]

27 minutes ago, don4l said:

I'm using the 120MC with PHD2.  I've no idea if the fact that it is colour has had any effect.  It just seems to work.

The only issue is that Bayer matrix can confuse some star tracking. If the wavelength of the start if blocked by one of the colours then the tracker may loose the star or find that the star centre point moves irregularly.

Edited January 30, 2020 by NickK
Pesky autocorrect

[don4l]

11 minutes ago, NickK said:

The only issue is that Bayer matrix can confuse some star tracking. If the wavelength of the start if blocked by one of the colours then the tracker may loose the star or find that the star centre point moves irregularly.

I seem to get guiding of 0.6" near the zenith, and about 1.2" lower down.  My imaging hasn't yet reached a standard where this has been an issue, so I haven't bothered learning about it.

 

If I was buying a canera for autoguiding only, then I would have gone for the mono.  As it is, I've played with some planetary and lunar.

[Avocette]

13 minutes ago, NickK said:

The only issue is that Bayer matrix can confuse some star tracking. If the wavelength of the start if blocked by one of the colours then the tracker may loose the star or find that the star centre point moves irregularly.

So would you recommend 2x2 binning in this case? I’m pretty sure I’ve read somewhere that 2x2 binning even for the monochrome 120MM is a good idea when using the Evoguide scope which is 242mm focal length.

[Gina]

Now I have a heavy-duty dual mounting bar for my EQ8 mount I'm thinking I should be able to have an imaging rig one side and guide rig on the other - particular for widefield.  I presume these dual mounting bars are intended for dual telescopes and a dual imaging rig.  The kit is certainly very heavy and rigid.

[Gina]

In fact I'm wondering about the Esprit 80ED and WF rig.  The Esprit has OAG and maybe could provide guiding for the WF rig.  A strange arrangement I must admit.

Edited January 30, 2020 by Gina

[Gina]

The FLO page for the ZWO OAG shows an ASI 120MC-S as guide camera!!  Not the mono version.  Well well!!!

[NickK]

3 hours ago, Avocette said:

So would you recommend 2x2 binning in this case? I’m pretty sure I’ve read somewhere that 2x2 binning even for the monochrome 120MM is a good idea when using the Evoguide scope which is 242mm focal length.

That would probably work well and actually allow a faster frame rate (depending on the seeing).

There is a fl vs binned pixel size but if the guide star image is large enough then a centre mass calculation shouldn’t have a problem.

All my cameras are mono.

 

Edited January 30, 2020 by NickK

[wimvb]

2 hours ago, Gina said:

The FLO page for the ZWO OAG shows an ASI 120MC-S as guide camera!!  Not the mono version.  Well well!!!

I think you're overthinking this. The setup in the image is most likely put together by marketing people. But probably either camera goes. 

[Gina]

Is there any reason I shouldn't use a 55mm f1.8 lens together with ASI 120 for guiding the widefield rigs?  The latter would have lenses of 105mm f2.8, 200mm f4 and possibly 55mm f1.8.  The shorter 55mm lens would make the guide-scope easier to accommodate.  Or would a longer focal length lens be better for guiding?

[JamesF]

You'd probably need to check how stars look.  f/1.8 is really quite fast and they might not make a big enough image on the sensor to be suitable for guiding on.  The aperture seems fine -- it's pretty much the same as a finder-guider after all, but finder-guiders tend to be around f/4 I think.

James

[Gina]

I could stop it down to f4.

I can check it next time there are some stars though.  I could print the bracket(s) and plug it into a USB port on the imaging RPi.  To check the stars in the ASI 120 I could just choose this camera in the imaging section of KStars/Ekos instead of the 1600.

Edited January 31, 2020 by Gina

[wimvb]

Pixelscale 206*3.75/55 = 14"/pixel, roughly. I would say that you are very undersampled. I don't think phd will like that star profile. You could try to cheat phd by giving the guidelens a small defocus.

With a minmo of 0.2 in phd, you'll be looking at an rms of 3" at least. The imaging camera @200 mm will have a pixelscale of 3.9"/pixel. About the expected rms. With a slight defocus and a minmo less than 0.2, it just might work. Try it, and share the results here. I'm very interested to see if it works. 

[Gina]

I've set up my WF imaging rig on my living room table and connected the ASI 120MC-S camera to a spare USB port on the RPi.  Both cameras are ZWO and hence use the ZWO CCD INDI driver.  I am only seeing the 1600 in both imaging camera and guide camera in Ekos and only the 1600 is in the Ekos list of attached items.  What do I need to do to get the 120 working as well as the 1600?

[Davey-T]

Speaking from experience if it's anything like ASCOM you need two different drivers.

Dave

[Gina]

I know of (I think) two people who have done it.

[wimvb]

I have a 174mm and 120mm-s on the same sbc (rock64, not raspberry pi). First of all, you need the usb3 version, but you're safe there. 

Next you need to start up the imaging ccd and guide ccd as indi_asi_ccd (zwo ccd) in your ekos profile. Btw, if you use remote desktop and run ekos on your Pi, you don't need to start indi server first. Ekos will do that for you. 

Once you've started ekos, you should see both cameras in the indi control psnel in ekos and kstars. In all the modules that use a camera, you will be able to select either.

I had problems running 2 zwo cameras from the same sbc before. Hence the use of 2 sbc's. But since I upgraded to ubuntu 18.04 (and now Armbian/ubuntu), I haven't had any problems anymore. 

Edited February 1, 2020 by wimvb

[Gina]

Been playing with driver names and different cameras etc and now have two ZWO cameras in Ekos.  ASI 1600MM-Cool and ASI 174MM.  I added an extra ASI driver and added "_2" to the end.

[JamesF]

I'd have thought the place to start would be to add another driver to your profile.  Then I think you should be able to select which one you want for imaging and which for guiding.

James