21 replies to this topic

[Whereisclearsky]

Hi,

 

I think about potentially switching from guiding scope to OAG, but I don't know much about it.

 

Currently my setup looks and is connected like this:

 

2600MC Pro -> ZWO Filter Drawer V2 -> Redcat 61 WIFD

My guide scope is ZWO 120MM Mini.

 

Would it be enough to get OAG like this:

https://www.firstlig...xis-guider.html

 

Attach it to main camera and that's it? Or would I need some other adapters?

 

Also is it a good idea since I'm doing mostly dual band, from time to time normal RGB?

 

Thanks

Edited by Whereisclearsky, 14 March 2025 - 08:42 AM.

[rgsalinger]

That will work but it goes in front of the filter drawer if you are going to be doing any form of narrow band. If you weren't an SWG mount, you could just use longer exposures but with an AM5, I doubt you will be happy with it attached to the camera with the filter drawer in front of it. . 

[Whereisclearsky]

That will work but it goes in front of the filter drawer if you are going to be doing any form of narrow band. If you weren't an SWG mount, you could just use longer exposures but with an AM5, I doubt you will be happy with it attached to the camera with the filter drawer in front of it. . 

Yes was just watching Cuiv and he mentioned it.

 

Is this Askar one good or any other alternative preferably cheaper?

What I like about Askar one it seems to have a focuser build in.

[Whereisclearsky]

What I'm worrying about also is that I've a lot of light pollution, but my guiding camera is ZWO 120MM mini, so not the most sensitive out there.

I could in theory set guiding to few seconds, but my mount is AM5 so it's probably not a good idea... hmmm

[DeepSky Di]

There’s no need to use an OAG with a redcat. I only do it because I switch cameras between OTAs. I like the ZWO OAG-L because it’s the right optical path length to fit into the back space, has a large prism, bolts to the EFW.

[Whereisclearsky]

There’s no need to use an OAG with a redcat. I only do it because I switch cameras between OTAs. I like the ZWO OAG-L because it’s the right optical path length to fit into the back space, has a large prism, bolts to the EFW.

I'm having rotation issues which could be caused by multiple things, including flexture.

This way I wouldn't have to worry about aligning anything.

[Whereisclearsky]

ZWO OAG-L

Would I be able to mount it directly to RC61 WIFD and my filter drawer without having to buy any adapters?

 

So the setup would be 2600MC -> ZWO Filter Drawer V2 -> ZWO OAG-L -> RC61 WIFD

[DeepSky Di]

We really need to figure out what is wrong with the guiding you already have. Adding an OAG is a step for when you already guide successfully and move to a longer focal length like an SCT.

[Spaceman 56]

I honestly don't see a reason to switch to an OAG for such a small focal length device as a RedCat.

 

if you are imaging at 850mm plus then the upgrade might be warranted, but below 700mm I would wonder why ?

 

Deep Sky Di is right. you need to figure out whats wrong with the current system.  

[Yomamma]

I put the regular ZWO OAG on mine and it works great, no more guide scope and a lot more compact unit. I had my ASI2600 on it and the train was the ZWO OAG, ZWO filter drawer, then the ASI 2600.  

 

Edited by Yomamma, 14 March 2025 - 06:28 AM.

[Whereisclearsky]

We really need to figure out what is wrong with the guiding you already have. Adding an OAG is a step for when you already guide successfully and move to a longer focal length like an SCT.

The issue might be flexture, there is no easy way to check for that. I have an issue with image field rotation/shift in my integrations, and I suspect that might be the cause.

I could try to modify my guiding setup to be able to align the scopes, but I like the idea of OAG much more.

I'm thinking about this one, since it has large prism:
​https://www.firstlig...xis-guider.html

Edited by Whereisclearsky, 14 March 2025 - 08:28 AM.

[Whereisclearsky]

I put the regular ZWO OAG on mine and it works great, no more guide scope and a lot more compact unit. I had my ASI2600 on it and the train was the ZWO OAG, ZWO filter drawer, then the ASI 2600.  

 

What is your guide camera and bortle?

I have a 120mm mini and Im not sure it would work since it’s not the best camera.

 

Also got a lot of light pollution.

 

edit:

I guess you are using 220mm mini

Edited by Whereisclearsky, 14 March 2025 - 08:43 AM.

[Yomamma]

I have used the asi290mm mini and now I use the asi174mm mini. The 290 worked well since the 51 runs at 4.9 fr but the 174 is a lot more sensitive and you can lower the exposure time

[rgsalinger]

Adding an OAG eliminates a wide range of possible flexure issues. Every telescope I've owned since 2011 has been equipped with an OAG. Setting one up and keeping it attached to the camera or wheel, gives you zero setup time. I pulled out an old camera/OAG combination after over a year about a week ago. The stars in the OAG were perfectly focused. 

 

I think that the only issue with using one with a filter drawer is whether or not you can get stars, if the drawer contains an NB filter. I don't really think that the OP needs a better camera. My advice is that if the budget is not a big issue, get the necessary adapters and see what you can achieve. 

 

I don't think that you can even buy a 290 anymore?? With a QE of almost 80 percent for the 174, I'm not sure how much more "sensitive" a 290 would be. The QE of the 120 is similar. I choose my guide cameras based strictly on the focal length of my systems. I find that all of them have roughly the same sensitivity, the issue is the size of the chip. 

Edited by rgsalinger, 14 March 2025 - 12:47 PM.

[Whereisclearsky]

Adding an OAG eliminates a wide range of possible flexure issues. Every telescope I've owned since 2011 has been equipped with an OAG. Setting one up and keeping it attached to the camera or wheel, gives you zero setup time. I pulled out an old camera/OAG combination after over a year about a week ago. The stars in the OAG were perfectly focused. 

 

I think that the only issue with using one with a filter drawer is whether or not you can get stars, if the drawer contains an NB filter. I don't really think that the OP needs a better camera. My advice is that if the budget is not a big issue, get the necessary adapters and see what you can achieve. 

 

I don't think that you can even buy a 290 anymore?? With a QE of almost 80 percent for the 174, I'm not sure how much more "sensitive" a 290 would be. The QE of the 120 is similar. I choose my guide cameras based strictly on the focal length of my systems. I find that all of them have roughly the same sensitivity, the issue is the size of the chip. 

The OAG would be mounted straight to telescope, then filter drawer and a main camera, so the filter wouldn't affect the guider.

I was told by someone that 120mm mini might be not sensitive enough, and that since my RC61 is 300mm and guide scope is 120mm, I will get less stars probably.

 

So I'm not sure, I don't want to spend too much, if I could only buy OAG without anything else then I could give it a go.

 

Perhaps there is someone with similar setup?

Edited by Whereisclearsky, 14 March 2025 - 12:51 PM.

[rgsalinger]

If you mount the OAG next to the telescope you are going to have trouble getting it par focal with the telescope. You will, I think, need a spacer because the main camera is going to be at least 30mm behind the OAG prism. Looking at the ASKAR unit I don't think that you have the much adjustment on it. Then, with the guide camera so far back, it's unclear how much sky you are going to get. Try it is always the best advice but look for a thread in spacer. 

[Whereisclearsky]

If you mount the OAG next to the telescope you are going to have trouble getting it par focal with the telescope. You will, I think, need a spacer because the main camera is going to be at least 30mm behind the OAG prism. Looking at the ASKAR unit I don't think that you have the much adjustment on it. Then, with the guide camera so far back, it's unclear how much sky you are going to get. Try it is always the best advice but look for a thread in spacer. 

And why does it matter how far main camera is from the OAG?

[rgsalinger]

They have to be parfocal. The distance from the OAG prism to the guide camera chip has to be the same as the distance between the prism and the main camera chip. Normally, that would be 24 or so mm for the popular ZWO cameras, including yours. If you interpose a 14mm thick filter drawer between the OAG and the main camera, then the guide camera needs to move out 14mm. Then you're going to have a smaller image circle to work with. I suspect that with your short focal length, if you get a spacer you'll be OK so it's really just a warning. 

[DeepSky Di]

And why does it matter how far main camera is from the OAG?

Because a single focus setting of your telescope has to be correct for both main camera and guide camera. If the prism is too far away from the main camera then the guide camera will have to be way out of the OAG.

[Whereisclearsky]

Well it sounds like too much hassle... and £££

So I guess I will pass on that idea.

 

Thanks though

[DeepSky Di]

So Whereisclearsky, there's a problem somewhere in this rig. I thought you had posted a photo of it but I can't' find it - if you did you could just post the link here. Same with the guide log.

 

The rig is AM5 + 2600MC + RedCat 61 WIFD + ZWO 32 mm guide scope and 120MM (mini?) guide camera + ASIAIR. Something isn't working leading to field rotation.

 

The issue could be poor polar alignment; there was an ASIAIR bug in approx October 2024 that made polar alignment wrong and consequently star were oblong.

 

Here are the things I'd like to ask about:

- what ASIAIR version is being used? Update to the latest if possible.

- what ASIAIR polar align version is being used? There's an original polar alignment function and a new one. The new one does not need to see the pole. However, switching to the original one would be a good diagnostic step.

- Check polar alignment by starting with mount in home position, polar aligning, going to a target, sending mount to home position again and verifying that the polar alignment did not become significantly different.

- Clear the guiding calibration every session (for now). Guiding can go crazy if you don't do this.

- verify everything is correctly assembled and nothing is wobbly - tripod spreader, telescope attachment to dovetail, guide scope attachment to handlebar

- check guide camera focus.

- check ASIAIR config - location, focal length of RedCat and guide scope

 

I'm certain that something simple and obvious is wrong; if so rest assured we have all been there. Best wishes.

[Whereisclearsky]

So Whereisclearsky, there's a problem somewhere in this rig. I thought you had posted a photo of it but I can't' find it - if you did you could just post the link here. Same with the guide log.

 

The rig is AM5 + 2600MC + RedCat 61 WIFD + ZWO 32 mm guide scope and 120MM (mini?) guide camera + ASIAIR. Something isn't working leading to field rotation.

 

The issue could be poor polar alignment; there was an ASIAIR bug in approx October 2024 that made polar alignment wrong and consequently star were oblong.

 

Here are the things I'd like to ask about:

- what ASIAIR version is being used? Update to the latest if possible.

- what ASIAIR polar align version is being used? There's an original polar alignment function and a new one. The new one does not need to see the pole. However, switching to the original one would be a good diagnostic step.

- Check polar alignment by starting with mount in home position, polar aligning, going to a target, sending mount to home position again and verifying that the polar alignment did not become significantly different.

- Clear the guiding calibration every session (for now). Guiding can go crazy if you don't do this.

- verify everything is correctly assembled and nothing is wobbly - tripod spreader, telescope attachment to dovetail, guide scope attachment to handlebar

- check guide camera focus.

- check ASIAIR config - location, focal length of RedCat and guide scope

 

I'm certain that something simple and obvious is wrong; if so rest assured we have all been there. Best wishes.

Yes that's my setup, and I'm on latest Asiair firmware, had same issue on older.

AM5 mount firmware updated lately.

Had the same issue with Skywatcher mount before, this is one of the reasons I've switched to AM5, this and not having to balance it lol.

 

I've tried both options of PA already unfortunately.

 

 

 

- Check polar alignment by starting with mount in home position, polar aligning, going to a target, sending mount to home position again and verifying that the polar alignment did not become significantly different.

I will for sure give this a try, but I'm pretty sure it will show different values since it often does it even without touching anything, lol.

 

Thanks