Guide Scope Options - Opinions, Please...

[Ian McCallum]

I was thinking about the combination of HiteAstro USB ST4 Guider and Svbony SV105 (fitted to a finderscope), connected to my laptop and EQ5 Enhanced motor drive for guiding.  Would this combination work or is there something better, but not extortionately expensive?🤔

[rickwayne]

If you're connecting to a laptop anyway, why not just use pulse guiding? Am I missing something? It's nice not to have to recalibrate every time you slew the scope.

[Ian McCallum]

4 hours ago, rickwayne said:

If you're connecting to a laptop anyway, why not just use pulse guiding? Am I missing something? It's nice not to have to recalibrate every time you slew the scope.

I'm not sure, to be honest. 🤔 These are DC motors, not stepper ones. I'm not sure if the stepper type use pulsed width modulation. 🤔

[rickwayne]

Pulse guiding has nothing to do with the type of motor, fortunately. It uses a connection (usually USB) to a mount's controller logic to emit pulses to tell the sidereal tracking circuitry to go faster or slower. So-called ST-4 guiding is an older (still viable) setup where the computer sends commands to the guide camera via USB, and the camera issues a signal over a cable connecting the camera to the mount.

If you're going to use the computer for mount things like slewing the scope to its target, you already have a USB connection between computer and mount anyway, so you may as well just use that for guiding too. That connection lets the mount tell the computer where it's pointing, which allows the guide software to adjust its commands to compensate for declination -- the magnitude of corrections will be different for different parts of the sky. With ST-4 guiding, the computer is only talking to the guide camera so has no way of knowing where the mount is pointing. So you have to do a calibration run so that the computer knows how much correction to apply to make the image move by N pixels on the guide camera sensor.

I'm not familiar with that mount so I don't know exactly how to connect which bits to what.

[Ian McCallum]

7 hours ago, rickwayne said:

Pulse guiding has nothing to do with the type of motor, fortunately. It uses a connection (usually USB) to a mount's controller logic to emit pulses to tell the sidereal tracking circuitry to go faster or slower. So-called ST-4 guiding is an older (still viable) setup where the computer sends commands to the guide camera via USB, and the camera issues a signal over a cable connecting the camera to the mount.

If you're going to use the computer for mount things like slewing the scope to its target, you already have a USB connection between computer and mount anyway, so you may as well just use that for guiding too. That connection lets the mount tell the computer where it's pointing, which allows the guide software to adjust its commands to compensate for declination -- the magnitude of corrections will be different for different parts of the sky. With ST-4 guiding, the computer is only talking to the guide camera so has no way of knowing where the mount is pointing. So you have to do a calibration run so that the computer knows how much correction to apply to make the image move by N pixels on the guide camera sensor.

I'm not familiar with that mount so I don't know exactly how to connect which bits to what.

I'm interested in learning more about the ST4 method, so I'm doing more reading up on it.  It's all rather new to me, as you can probably tell.🙄

[alacant]

11 hours ago, Ian McCallum said:

interested in learning more about the ST4

Hi

If you want to stick with st4, we'd recommenend, in addition to the camera - mount connection...

...connection as an aux device between computer and mount. This will allow you to both re-use your calibration and add the ability to control telescope pointing from the computer too.

Cheers and HTH

 

Edited December 25, 2021 by alacant

[Ian McCallum]

41 minutes ago, alacant said:

Hi

If you want to stick with st4, we'd recommenend, in addition to the camera - mount connection...

...connection as an aux device between computer and mount. This will allow you to both re-use your calibration and add the ability to control telescope pointing from the computer too.

Cheers and HTH

 

What did you have in mind? Can you give me an example, please? 

[alacant]

17 minutes ago, Ian McCallum said:

What did you have in mind?

Assuming the mount has a suitable port, just as you envisage, but with the addition of a mount to laptop cable.

HTH

[Ian McCallum]

19 minutes ago, alacant said:

Assuming the mount has a suitable port, just as you envisage, but with the addition of a mount to laptop cable.

HTH

The mount doesn't have a suitable port, only the Enhanced controller does....

[alacant]

11 hours ago, Ian McCallum said:

doesn't have a suitable port

ST4 it is then. On camera only.

There's an overview here.

Good luck and HTH

Edited December 26, 2021 by alacant

[bobro]

There are messages in this thread which may be confusing, so it's useful to go back to basics. In summary:

• The 'DC Motors'  as mentioned for the EQ5 Enhanced Motor Drive are stepper motors. The drawback is that they are highly geared (to maximise battery life), which means they are much too slow for goto use. Nevertheless, they work well for accurate tracking and guiding with a suitable setup.
• Guide cameras do not have to be the route for sending guiding corrections commands to a mount - this can be separate to the guide camera. As an example, a programmed Arduino or similar USB-ST4  device can receive guiding commands and operate relays to guide a mount via ST-4. Nevertheless, a sensitive guide camera with ST-4 (e.g. ASI120) can make for a reasonably cost effective way to combine the two functions and may be a better solution than the (mature) ST-4 Guider and SV105 (discontinued sensor) mentioned at the start of this thread.  PHD2 is a great way to guide and supports most hardware.
• The 'Enhanced Controller' has an ST-4 port for guiding corrections only. It cannot be used for goto.

 

 

 

[Ian McCallum]

I'm very much leaning towards the ZWO ASI120MM mini camera, with an adapter for a SW 9x50mm finderscope.