12 replies to this topic

[Avitam]

Hello All,

 

My question is a lot more specific than the title may suggest. I couldn't come up with a more creative or specific title.

 

First, a few details of my setup before I get to my question:

 

Mount: Vintage Losmandy GM8 with a 492 digital drive, so strictly push to. 

Guiding: ZWO ASI 120MM-S connected via one of (a) camera to Laptop to GPUSB to mount (poor man's pulse guiding I guess?) or (b) ST4 directly from camera to mount using an RJ12 cable. Guiding using either PhD2 or ASiair although I really prefer PhD2 since it gives me a LOT more control and informatics.  I have not done enough guiding to see a difference between GPUSB vs Standard ST4...looks similar. 

 

I want to point out that I have absolutely no issues with Push To. I understand the convenience of Goto, but I am ok without it. 

 

So that brings me to my specific question: if I don't really care about automated target slewing with Goto, what other advantages does an OnStep like platform offer? I have jotted down a few based on my limited knowledge:

 

1. Pulse guiding vs ST4 guiding? Is the former "better" than the other?  On a good day, I have hit in the ball park 2-3 arc-secs RSS and this is with 0 mechanical upgrades to the mount. I feel this is dominated by mount mechanics and seeing so not spotting an obvious reason why a Goto upgrade will have any bearing on this. 

2. PEC: Currently I do PEC using the 492 controller. I do it whilst autoguiding...I don't have enough data to suggest there is a big difference in tracking before and after PEC, but it's not painful to do. Only downside is I need to do it everytime as there is no permanent PEC option on the 492...again...just an additional 8 mins of my time. But there is NO option to apply externally generated PEC from programs like PEMPro. Is this really a big deal? 

3. Redoing guide calibration everytime: I have read generic statements that with ST4 guiding, guide calibration must be performed close to the target of interest and done for every imaging session, primarily because of the absence of pointing information within PhD2. I am not sure I fully understand this restriction, but I found what I thought is an elegant work-around. I can get Sharpcap to pass on pointing information to PhD2 so during guiding calibration it automatically knows where the guide scope is pointing. I have no idea if this is a substitute for whatever you get with an OnStep like platform. 

 

I am sure I am missing other advantages that I am hoping you all can help me with. 

 

Boiling all of the above to one question: given my specific context, is there any value in me moving to OnStep? 

 

(I am anticipating this will come up, so will try to pre-emptively answer: yes...I have multiple mechanical upgrades to the mount that I am going to do irrespective of Push to vs Goto : brass worms, regreasing, adding springs, higher quality ABEC7 bearings.....). 

 

Many thanks!

 

Avi

Edited by Avitam, 21 May 2025 - 01:15 PM.

[photoracer18]

The term push-to assumes you have either Losmandy or JMI encoders on the mount. Is that correct?

[Inkie]

The motorized setups across the board require inputs and then slewing at the designated speed. It takes time. And a suitable power source. If you set up your mount properly, all you have to do is to manually push the OTA until the requisite coordinates are displayed, and from there you should be within 15-30" of your object.  About as long as it takes to read that particular sentence.

[Avitam]

The term push-to assumes you have either Losmandy or JMI encoders on the mount. Is that correct?

Oh...if that is the definition of push-to, then my GM8 is not that...it's even more old school. To find targets I do one of 2 things : (a) use the manual setting circles or (b) using Sharpcap push to assistant. 

 

So no encoders that guide me...just platesolving in Sharpcap and manually pushing the scope either by hand or using the hand controller. (a) mostly sucks (as expected) but (b) works remarkably well for me....which is really why I asked the original question. 

Edited by Avitam, 21 May 2025 - 03:12 PM.

[Frank Logan]

Oh...if that is the definition of push-to, then my GM8 is not that...it's even more old school. To find targets I do one of 2 things : (a) use the manual setting circles or (b) using Sharpcap push to assistant. 

 

So no encoders that guide me...just platesolving in Sharpcap and manually pushing the scope either by hand or using the hand controller. (a) mostly sucks (as expected) but (b) works remarkably well for me....which is really why I asked the original question. 

If you want some GOTO functionality, you could build a Arduino-ST4 interface microcontroller. Instructions by code writer Kevin Ferrare, can be found here on Github. Having build it, I’m more than happy to help anyone looking to build it for their ST4 enabled and connected handset for dual axis motors. You can find the items needed here; Project boxes, Arduino Nano, TLP521-4 Optocoupler and 6P6C RJ11 wired modular connector.

 

I use this with Stellarium. Point and confirm your coordinates, then pick object to slew to. Great for bad seeing conditions or objects to faint to find on your own.

 

Frank

[macdonjh]

My two cents: 

 

Setting circles work well if your mount is permanently installed and polar aligned very accurately.  If you set up and tear down each night, they are a pain.

 

For visual observation, I don't see any advantage to go-to over push-to.  As Inkie says, push-to might be more efficient.  I use push-to in my driveway.  Until I started imaging, I didn't connect a computer to my go-to mount: I entered object catalog numbers into the hand controller and hit <go-to>. 

 

For photography, though, I am glad I have go-to.  Not so much for the automated pointing, but go-to allows my image capture software to use plate solving results to automatically center my target, even if I can't see it, very accurately.  That would be a serious pain and time-sink with push-to.  

[ABQJeff]

To me GoTo + tracking main advantage vs Push-To + Tracking is for visual.

 

Go-To: 15+ recorded obs per hour of Mag 12 and dimmer galaxies

 

Push To: half that rate and a tough slog if no stars near a faint fuzzy. But if all you are doing is imaging a couple objects the speed of jumping to different places objects.

 

(That being said: I enjoy star hopping with my binoculars for bright objects.)

[Avitam]

To me GoTo + tracking main advantage vs Push-To + Tracking is for visual.

 

Go-To: 15+ recorded obs per hour of Mag 12 and dimmer galaxies

 

Push To: half that rate and a tough slog if no stars near a faint fuzzy. But if all you are doing is imaging a couple objects the speed of jumping to different places objects.

 

(That being said: I enjoy star hopping with my binoculars for bright objects.)

I would consider myself lucky if I am able to shoot more than 3-4 DSOs in a month. That is another way of saying that speed of finding an object is irrelevant to me. 

 

But I do agree...if visual is the main goal (which is not for me...in fact visual is not even a goal) then Goto would be absolutely essential.

[Avitam]

My two cents: 

 

Setting circles work well if your mount is permanently installed and polar aligned very accurately.  If you set up and tear down each night, they are a pain.

 

For visual observation, I don't see any advantage to go-to over push-to.  As Inkie says, push-to might be more efficient.  I use push-to in my driveway.  Until I started imaging, I didn't connect a computer to my go-to mount: I entered object catalog numbers into the hand controller and hit <go-to>. 

 

For photography, though, I am glad I have go-to.  Not so much for the automated pointing, but go-to allows my image capture software to use plate solving results to automatically center my target, even if I can't see it, very accurately.  That would be a serious pain and time-sink with push-to.  

I agree...I only mentioned setting circles because that is what I used to do before I purchased Sharpcap.

 

The setting circles on my GM8 are now redundant....I use the Push To assistant in Sharpcap and along with my hand controller I have absolutely no issues finding/centering targets....takes me < 5-10 mins after a good PA. 

[Avitam]

If you want some GOTO functionality, you could build a Arduino-ST4 interface microcontroller. Instructions by code writer Kevin Ferrare, can be found here on Github. Having build it, I’m more than happy to help anyone looking to build it for their ST4 enabled and connected handset for dual axis motors. You can find the items needed here; Project boxes, Arduino Nano, TLP521-4 Optocoupler and 6P6C RJ11 wired modular connector.

 

I use this with Stellarium. Point and confirm your coordinates, then pick object to slew to. Great for bad seeing conditions or objects to faint to find on your own.

 

Frank

Hi Frank

 

This is interesting. For Goto, I was going to go with either Teen Astro or OnStep. 

 

How do you get true goto without upgrading the motors and the motor controller? Slew speeds on push to mounts are at max 16X sidereal.

Edited by Avitam, 27 May 2025 - 01:05 PM.

[Frank Logan]

Hi Frank

 

This is interesting. For Goto, I was going to go with either Teen Astro or OnStep. 

 

How do you get true goto without upgrading the motors and the motor controller? Slew speeds on push to mounts are at max 16X sidereal.

True 16x sidereal. No different than star-hopping. The Arduino-ST4 interface microcontroller, connects to the Sky-Watcher enhanced hand controller or ST4 port modified basic hand controller through the ST4 port. The Arduino USB mini port connects to your PC, for power and microcontroller functionality. Your guide scope/camera connects to the PC. Manually pick a known DSO or star close to the target. Your microcontroller should already be registered by you in Stellarium as a telescope. Pick the object in Stellarium and centre on it. Pick the target, and the microcontroller through the handset will slew to the target. 8x for basic modified handset, and 16x for the Sky-Watcher enhanced.

 

I think that answers your question.

 

Why not get a One-Step, or other system? This flexs a bit more grey matter, and you get the satisfaction of having built part of the brains of your telescope. You get to keep it simple and continue using 6v DC, so no heavy 12v DC power packs. And it keeps it fun and engaging, as the telescope is just smart enough.

 

Frank

[Avitam]

True 16x sidereal. No different than star-hopping. The Arduino-ST4 interface microcontroller, connects to the Sky-Watcher enhanced hand controller or ST4 port modified basic hand controller through the ST4 port. The Arduino USB mini port connects to your PC, for power and microcontroller functionality. Your guide scope/camera connects to the PC. Manually pick a known DSO or star close to the target. Your microcontroller should already be registered by you in Stellarium as a telescope. Pick the object in Stellarium and centre on it. Pick the target, and the microcontroller through the handset will slew to the target. 8x for basic modified handset, and 16x for the Sky-Watcher enhanced.

 

I think that answers your question.

 

Why not get a One-Step, or other system? This flexs a bit more grey matter, and you get the satisfaction of having built part of the brains of your telescope. You get to keep it simple and continue using 6v DC, so no heavy 12v DC power packs. And it keeps it fun and engaging, as the telescope is just smart enough.

 

Frank

Hi Frank, 

 

This is actually nice. So this is basically a GPUSB but with a microcontroller that actually gives one go-to capabilities. 

 

I have a GPUSB that is use for pseudo pulse guiding already but this seems like an upgrade. 

 

Worth trying as a fun experiment of not for anything else. 

 

Looks like the creator had some interesting upgrades in his to-do list...not sure if he got to them:) 

 

Thanks for pointing this out to me! 

 

Avi 

[Frank Logan]

Hi Frank, 

 

This is actually nice. So this is basically a GPUSB but with a microcontroller that actually gives one go-to capabilities. 

 

I have a GPUSB that is use for pseudo pulse guiding already but this seems like an upgrade. 

 

Worth trying as a fun experiment of not for anything else. 

 

Looks like the creator had some interesting upgrades in his to-do list...not sure if he got to them:) 

 

Thanks for pointing this out to me! 

 

Avi 

He did. The program works great. 

 

Frank