ASI AIR Polar Alignment with Guide Camera (Using a DSLR main camera) - Forums

I realize that this might be a dumb and obvious post, but to me this was a breakthrough.

My setup: I have an SVBONY 80mm ED telescope with a 0.8 field flattener/reducer and a Nikon D750 (unmodified) as my main camera. I also have an SVBONY 50mm guide scope with a ZWO ASI120MM camera. I control everything with an ASI AIR Mini.

For the last 2 weeks I struggled to do ASI AIR polar alignment with the main (DSLR) camera. The image download time and subsequent plate solving was long even for short exposures and the process was slow and time consuming. I managed to do it with reasonable accuracy but it took a long time.

I had a recent realization that I could temporarily switch the main camera to the guide camera and do polar alignment with the guide camera! Wow, what a difference! The ZWO ASI120MM provides almost real time images and if I set the image capture to AUTO I can do almost real time adjustments to my polar alignment. I cut my polar alignment time from 30 minutes to around 5 minutes! ( I aim for < 5" accuracy before switching to guiding)

My apologies if this is obvious but it was a breakthrough for me. After the polar alignment is sufficiently close, I then switch the main camera back to the Nikon DSLR and the guide camera back to the ZWO Mini. I consistently get under 0.75" rms tracking error with an unmodified and untuned HEQ5 mount so that works for me.

Is the use of the guide camera for polar alignment indeed obvious for all except me? I realize for those of you with a CMOS/CCD main camera (not DSLR) this is probably a mute point

Neil

I've done this when setting up for lunar imaging. Works pretty good. Kinda have to when using the AM-5 with no polar scope.

Hi Neil

My suspicion would fall on the cable between your DSLR and the ASIAIR Mini. If that cable is droppng a lot of data (without completely failing), then you might see excessively long exposure download times. Short of getting the cable tested, you could try the following:

1. Do file transfers from your DSLR directly to your computer show the same excessive time lags when using the same cable (this suggests the cable has haddeth it and should be replaced)?
2. If you use the same cable to connect the guide scope to the ASIAIR, does it show similar lagging (if so, then it is the cable's fault, so replace)
3. Is your DSLR set to use "WiFi first" for data transfer (some systems will do this, and it means that the DSLR will always try to send a data packet first to the WiFi service, which inevitably fails). Try turning off the DSLRs WiFi service and see if the performance picks up

Frankly, I would not use a guide scope for polar alignment, because:
1. It would need to have perfect axial alignment with your main scope, which is surprisingly difficult, and sometimes impossible
2. The optical quality of guide scopes is often so-so, and as a result the measurement of star position in the polar alignment routine may be worse than so-so and the alignment will be a dog's breakfast

The one situation where I think it is justified to use a guide scope for polar alignment is where your main scope has an exceptionally narrow field of view (like bloody great big SCTs), and cannot see enough stars to properly plate solve the polar asterisms (I'm assuming you are using the ASIAIR polar alignment routine based on multiple stars, not just Polaris - I am in the Southern Hemisphere, and multi-star polar alignment is pretty much essential).

Regards

Tim

Yeah if you go to the full version of PHD2 it offers three additional polar alignment methods and they all use (by definition since it's PHD2) your guide camera. It too is a camera and a telescope after all.

I have the opinion that it would be ok to use the finder scope for polar alignment since it saves so much time in your case. I have this opinion due to devices such as the iOptron iPolar definitely having optics no better than a cheap finder from my experience. With the iPolar, I am able to get very accurate alignments as reported by PHD2.

I also don't think it needs to have perfect axial alignment with your main scope. From what I understand, you are not polar aligning your main scope or your guide scope per-se, but the mount itself. The ASI Air, NINA, any routine, are evaluating the RA axis of the mount.

Tim Anderson:
Hi Neil

My suspicion would fall on the cable between your DSLR and the ASIAIR Mini. If that cable is droppng a lot of data (without completely failing), then you might see excessively long exposure download times. Short of getting the cable tested, you could try the following:

1. Do file transfers from your DSLR directly to your computer show the same excessive time lags when using the same cable (this suggests the cable has haddeth it and should be replaced)?
2. If you use the same cable to connect the guide scope to the ASIAIR, does it show similar lagging (if so, then it is the cable's fault, so replace)
3. Is your DSLR set to use "WiFi first" for data transfer (some systems will do this, and it means that the DSLR will always try to send a data packet first to the WiFi service, which inevitably fails). Try turning off the DSLRs WiFi service and see if the performance picks up

Frankly, I would not use a guide scope for polar alignment, because:
1. It would need to have perfect axial alignment with your main scope, which is surprisingly difficult, and sometimes impossible
2. The optical quality of guide scopes is often so-so, and as a result the measurement of star position in the polar alignment routine may be worse than so-so and the alignment will be a dog's breakfast

The one situation where I think it is justified to use a guide scope for polar alignment is where your main scope has an exceptionally narrow field of view (like bloody great big SCTs), and cannot see enough stars to properly plate solve the polar asterisms (I'm assuming you are using the ASIAIR polar alignment routine based on multiple stars, not just Polaris - I am in the Southern Hemisphere, and multi-star polar alignment is pretty much essential).

Regards

Tim

Thanks, Tim! You know although I have been using DSLR's for a very long time, I had never (until I got the ASI AIR) connected my camera directly to a computer. with a USB cable. After reading your response I tried connecting my D750 to my iPad directly and I discovered that the images download virtually instantly! Whereas they take about 1 minute to download to the ASI AIR. Very curious! I checked that WiFi is turned off in the camera as you suggested. I'll have to try and troubleshoot some more. Given that the downloads to the iPad are fast, I believe that my cable is good.

I have the opinion that it would be ok to use the finder scope for polar alignment since it saves so much time in your case. I have this opinion due to devices such as the iOptron iPolar definitely having optics no better than a cheap finder from my experience. With the iPolar, I am able to get very accurate alignments as reported by PHD2.

I also don't think it needs to have perfect axial alignment with your main scope. From what I understand, you are not polar aligning your main scope or your guide scope per-se, but the mount itself. The ASI Air, NINA, any routine, are evaluating the RA axis of the mount.

Thanks, Chris! I was also under the impression that it was fine to use the guide scope, because as you say we are getting the MOUNT polar aligned, not the scope. My guide scope is not even close to being in axial alignment with my main scope. Some time ago I intentionally moved the guide scope several degrees away from the main scope axis in order to see more guide stars, and I never bothered turning it back! With my polar alignment method I am able to get good tracking and I can take 5 minute subs with round stars so I think my alignment is fine. I have no concerns about the accuracy of my polar alignment - my post was intended to address the SPEED of getting to polar alignment!

not in the topic (never mind)

cs,
Iro

This is what I needed to do before I got a ZWO camera. My Canon DSLR would disconnect constantly during PA, but during imaging it was fine. After 3 or so sessions I realized that my guide camera would work for PA just as well as my DSLR.

This is what I needed to do before I got a ZWO camera. My Canon DSLR would disconnect constantly during PA, but during imaging it was fine. After 3 or so sessions I realized that my guide camera would work for PA just as well as my DSLR.

I capture images from my Nikon D750 on the ASI AIR internal memory and to the best of my knowledge I have never lost a frame. It is just slow to transmit from the DSLR to the iPad for Polar Alignment, hence the desire to use the ZWO guide cam for alignment which loads quickly.

Sounds like many others use their guide cams for polar alignment and I was just slow to realize this!

Last night I polar aligned with my guide camera to within about 5", then switched the main camera back to the DSLR, and I was subsequently able to guide with an RMS error of around 0.5". (HEQ5 mount with a 19 pound payload)

Thanks all!
Neil

I have some questions about the ASIair Mini

1. ZWO says "Live mode requires DSLR/MILC camera equiping with a total pixel number less than 26 million".
What is live mode, is it live stacking?

2. What does ASIair use to platesolve and polar align, the main camera or the guiding camera?

3. Should I be able to take exposures with my 45mp mirrorless camera through the app?

4. What is the name of the cable that I would need to connect my ASIair mini to my Canon R5? Shutter release?

I hope I'm not asking for too much, I'm a newbie. If someone can take the time to answer just one or two of my questions, I would be very happy.

FYI,
Guide cam: asi120mm mini
Mount: AVX
Guidescope: Orion deluxe 50mm
Telescope: C8-N 1000mm Newt

I'll answer as best I can with 3 weeks of experience with the Mini! I have a Nikon Full Frame DSLR, the D750.

1). to the best of my knowledge, yes, supporting "live mode" means that "live stacking" is supported. According to the list from ZWO, at the bottom of this page: https://astronomy-imaging-camera.com/product/asiair-mini/ , my full frame Nikon is supported for Live Tracking although I haven't tried it yet. I am open to being corrected on this given that I don't use live stacking. (The Canon R5 is not on the list as being supported in Live Mode - but do you need it? I have never used it)

2). Plate solving is done on images captured by the main camera. Although (and this is the entire point of this post that I initiated), you can temporarily change the main camera to be the guide camera and do plate solving and polar alignment with it. But after you are done aligning, you need to change the main camera back to your DSLR or mirrorless or whatever you are using as the main.

3). Check out the list at the bottom of this page from ZWO: https://astronomy-imaging-camera.com/product/asiair-mini/. If it is on the list then yes, otherwise no. I am not familiar with Canons but I see one Canon EOS R5 on the list. Not sure if this is what you have.

4). I used this cable from Amazon for my Nikon DSLR and it works perfectly:
https://www.amazon.com/dp/B07KK6S5HM?psc=1&ref=ppx_yo2ov_dt_b_product_details.

If I look up Canon R5 I see this. I can't claim that it works but it gets good reviews:
https://www.amazon.com/BRENDAZ-Compatible-Mirrorless-Supports-Transfer/dp/B08GRB3FXK/ref=sr_1_3?crid=1P3SZYQRQHKX3&keywords=canon%2BR5%2Busb%2Bcable&qid=1691468126&sprefix=canon%2Br5%2Busb%2Bcable%2Caps%2C142&sr=8-3&th=1

Neil

I'll answer as best I can with 3 weeks of experience with the Mini! I have a Nikon Full Frame DSLR, the D750.

1). to the best of my knowledge, yes, supporting "live mode" means that "live stacking" is supported. According to the list from ZWO, at the bottom of this page: https://astronomy-imaging-camera.com/product/asiair-mini/ , my full frame Nikon is supported for Live Tracking although I haven't tried it yet. I am open to being corrected on this given that I don't use live stacking. (The Canon R5 is not on the list as being supported in Live Mode - but do you need it? I have never used it)

Thanks! I already bought the EOS R5 a while ago. It's really good for photography, so I'm keeping it.

2). Plate solving is done on images captured by the main camera. Although (and this is the entire point of this post that I initiated), you can temporarily change the main camera to be the guide camera and do plate solving and polar alignment with it. But after you are done aligning, you need to change the main camera back to your DSLR or mirrorless or whatever you are using as the main.

I will do that.

3). Check out the list at the bottom of this page from ZWO: https://astronomy-imaging-camera.com/product/asiair-mini/. If it is on the list then yes, otherwise no. I am not familiar with Canons but I see one Canon EOS R5 on the list. Not sure if this is what you have.

Yep, the Canon EOS R5 is on the list.

4). I used this cable from Amazon for my Nikon DSLR and it works perfectly:
https://www.amazon.com/dp/B07KK6S5HM?psc=1&ref=ppx_yo2ov_dt_b_product_details.

If I look up Canon R5 I see this. I can't claim that it works but it gets good reviews:
https://www.amazon.com/BRENDAZ-Compatible-Mirrorless-Supports-Transfer/dp/B08GRB3FXK/ref=sr_1_3?crid=1P3SZYQRQHKX3&keywords=canon%2BR5%2Busb%2Bcable&qid=1691468126&sprefix=canon%2Br5%2Busb%2Bcable%2Caps%2C142&sr=8-3&th=1

Okay, so it needs to connect to one of the ASIair's USB ports. USB-A to USB-C, I get it now.

Thanks for taking the time to write all this and provide the links!

I'll answer as best I can with 3 weeks of experience with the Mini! I have a Nikon Full Frame DSLR, the D750.

1). to the best of my knowledge, yes, supporting "live mode" means that "live stacking" is supported. According to the list from ZWO, at the bottom of this page: https://astronomy-imaging-camera.com/product/asiair-mini/ , my full frame Nikon is supported for Live Tracking although I haven't tried it yet. I am open to being corrected on this given that I don't use live stacking. (The Canon R5 is not on the list as being supported in Live Mode - but do you need it? I have never used it)

Thanks! I already bought the EOS R5 a while ago. It's really good for photography, so I'm keeping it.
2). Plate solving is done on images captured by the main camera. Although (and this is the entire point of this post that I initiated), you can temporarily change the main camera to be the guide camera and do plate solving and polar alignment with it. But after you are done aligning, you need to change the main camera back to your DSLR or mirrorless or whatever you are using as the main.

I will do that.
3). Check out the list at the bottom of this page from ZWO: https://astronomy-imaging-camera.com/product/asiair-mini/. If it is on the list then yes, otherwise no. I am not familiar with Canons but I see one Canon EOS R5 on the list. Not sure if this is what you have.

Yep, the Canon EOS R5 is on the list.
4). I used this cable from Amazon for my Nikon DSLR and it works perfectly:
https://www.amazon.com/dp/B07KK6S5HM?psc=1&ref=ppx_yo2ov_dt_b_product_details.

If I look up Canon R5 I see this. I can't claim that it works but it gets good reviews:
https://www.amazon.com/BRENDAZ-Compatible-Mirrorless-Supports-Transfer/dp/B08GRB3FXK/ref=sr_1_3?crid=1P3SZYQRQHKX3&keywords=canon%2BR5%2Busb%2Bcable&qid=1691468126&sprefix=canon%2Br5%2Busb%2Bcable%2Caps%2C142&sr=8-3&th=1

Okay, so it needs to connect to one of the ASIair's USB ports. USB-A to USB-C, I get it now.

Thanks for taking the time to write all this and provide the links!

You are welcome! Good luck and keep us posted on the results!

Neil

I'll answer as best I can with 3 weeks of experience with the Mini! I have a Nikon Full Frame DSLR, the D750.

1). to the best of my knowledge, yes, supporting "live mode" means that "live stacking" is supported. According to the list from ZWO, at the bottom of this page: https://astronomy-imaging-camera.com/product/asiair-mini/ , my full frame Nikon is supported for Live Tracking although I haven't tried it yet. I am open to being corrected on this given that I don't use live stacking. (The Canon R5 is not on the list as being supported in Live Mode - but do you need it? I have never used it)

Thanks! I already bought the EOS R5 a while ago. It's really good for photography, so I'm keeping it.
2). Plate solving is done on images captured by the main camera. Although (and this is the entire point of this post that I initiated), you can temporarily change the main camera to be the guide camera and do plate solving and polar alignment with it. But after you are done aligning, you need to change the main camera back to your DSLR or mirrorless or whatever you are using as the main.

I will do that.
3). Check out the list at the bottom of this page from ZWO: https://astronomy-imaging-camera.com/product/asiair-mini/. If it is on the list then yes, otherwise no. I am not familiar with Canons but I see one Canon EOS R5 on the list. Not sure if this is what you have.

Yep, the Canon EOS R5 is on the list.
4). I used this cable from Amazon for my Nikon DSLR and it works perfectly:
https://www.amazon.com/dp/B07KK6S5HM?psc=1&ref=ppx_yo2ov_dt_b_product_details.

If I look up Canon R5 I see this. I can't claim that it works but it gets good reviews:
https://www.amazon.com/BRENDAZ-Compatible-Mirrorless-Supports-Transfer/dp/B08GRB3FXK/ref=sr_1_3?crid=1P3SZYQRQHKX3&keywords=canon%2BR5%2Busb%2Bcable&qid=1691468126&sprefix=canon%2Br5%2Busb%2Bcable%2Caps%2C142&sr=8-3&th=1

Okay, so it needs to connect to one of the ASIair's USB ports. USB-A to USB-C, I get it now.

Thanks for taking the time to write all this and provide the links!

You are welcome! Good luck and keep us posted on the results!

Neil

sorry one more clarification.... when I said "do you need it" I was referring to Live Stacking, not your Canon EOS R5! I have been Imaging successfully without live stacking.

Neil

Hi Neil
Good tip, thanks for sharing your process.
I have a question though: do you move the 120MM guide camera from your guidescope to put it on the main scope when you do the PA, when you define it as your main camera?
I understand that you have to specify the focal length of the guide scope and main scope in the ASI Air App, and I guess these are not the same. So when you just switch the role of the camera (from guide to main) without moving it physically, the app should assume the main camera is on the main scope, and consider the focal length of the main scope. Not sure if that would be very problematic, but probably a source of confusion for platesolving, since the app needs to know the angular size of the frame it is trying to solve.
Another "benefit" of manually moving the camera would be to solve the issue of the guide scope alignment with the main scope. But as I understood from your responses, this seems to be a non-issue.
Looking forward to hearing more about your process on this detail.
Thanks
Sébastien

I also use guidescope and guidecamera for polaralignment in NINA. It‘s very comfortable as you just have to load another profile. The benefit is faster platesolving because of smaler sensor resolution and it‘s an absolut quite process now. When I did three point polaralignment without polaris visible using my sony a7ra my nightbours gone mad by the permanent clicking of the shutter 😃.

Hi Neil
Good tip, thanks for sharing your process.
I have a question though: do you move the 120MM guide camera from your guidescope to put it on the main scope when you do the PA, when you define it as your main camera?
I understand that you have to specify the focal length of the guide scope and main scope in the ASI Air App, and I guess these are not the same. So when you just switch the role of the camera (from guide to main) without moving it physically, the app should assume the main camera is on the main scope, and consider the focal length of the main scope. Not sure if that would be very problematic, but probably a source of confusion for platesolving, since the app needs to know the angular size of the frame it is trying to solve.
Another "benefit" of manually moving the camera would be to solve the issue of the guide scope alignment with the main scope. But as I understood from your responses, this seems to be a non-issue.
Looking forward to hearing more about your process on this detail.
Thanks
Sébastien

Hi Sebastien,

yes, it is necessary to select the 120MM as the main camera AND ALSO to change the focal length to be that of the guide scope (in my case = 190mm). Then, when you are done polar aligning and you switch back to your main camera again, it is necessary to manually change the focal length back to the correct one (in my case 714mm). You are correct that if you do not select the correct focal length, then plate solving will fail.

I understand that it is an extra step to manually make these changes back and forth - but in my case the time saving in Polar Alignment is worth it!

As Markus pointed out, with other software such as NINA you can set up profiles which will make it easier to select the correct settings. I don't believe that you can set profiles in the ASI AIR but I may be wrong.

Neil

Problem Asiair mini with Canon EOS 600da (Ti3)I have successfully connected my GEM28 with Asiair mini via WiFi. GEM28 and Asiair communicate well with each other.
With PA I have the problem. The main camera is the 600da (Ti3) and the guide camera is the Asi120mc.
After I have started PA, "Loading" appears and nothing moves, i.e. no stars are found. I have a clear view of Polaris!
But when I make the Asi120mc the main camera and start PA, everything runs very well and I can order my GEM28 very well.
Then I switch back to the Canon 600da (Ti3) , Maincamera, and the Asi120mc to the guide camera. When I swap cameras, I always enter the focal length of the main camera used.
When I then approach a target, this is also found well and the routine of the Asiair mini runs (target in the centre).
If I then start an image capture in preview mode, nothing works! Camera does not trigger, picture is not taken?
Frustrated, I give up.
Where are my errors?
Best regards from Germany
Wolfgang

Wolfgang, when you switch back to the DSLR camera, is the slide switch turned on? (green). It will switch off when you change cameras so you have to turn it on each time. If it's not that, it sounds like the ASIAIR is recognizing your DSLR (if not it would not be in the list and you couldn't select it). Is your camera set to Manual and Bulb mode? Are you sure that your cable is working correctly?

Neil

I actually started doing that last weekend, when I put a 3nm dual narrowband filter in front of my main camera. Polar aligning at the start of the night, not fully dark yet, the main camera wasn't able to plate solve sufficiently. The guide scope, without the narrowband filter and wider FOV, worked perfectly.

Hi Neil,
Yes, the green switch is on and the Canon is listed.
Thank you very much.
Greetings Wolfgang

Hi Huib,
Your assumption could be right.
I have an Astronomik CLS clip filter directly in the camera. I will remove the filter this evening and then test again.
I will report back.
Thank you very much.
Greetings Wolfgang

Hello,
unfortunately I couldn't do the test without the filter yet, clouds 😠.
I will get back to you.
Greetings Wolfgang

Hello,
I'm still here.
As already written, I have a clear view of Polaris. I think my problem is that when RA axis is rotated 60 degrees (counterclockwise, when the mount is between you and the north celestial pole) the mount (GEM28) does not find enough stars anymore and thus the Polar alignment is not completed. And to my dismay, after the 60 degree swing, the telescope then points to the neighbour's roof😀😠. That can't go well, I thought.
Last night I switched the guide camera to the main camera again. Then on the Asiair mini I set All-Sky Polar Align to green and started a PA with Asiair mini at the same location. Found enough stars and then a slew of the RA by now about 25 degrees, neighbour's house roof has not yet blocked view of sky, Plate Solving and then moved RA axis again by about 25 degrees, house roof now in view telescope.
Then to my amazement the smiley laughed😀 and the PA was finished.
I must add that I always observe from the same vantage point and do a polar alignment with Asiair with Polarscope on GEM28 before launch.
Then back again and Ti3 instructed as main camera. Bright target (Altair) approached with GoTo, Asiair starts to work but the wheel turns and turns without end. Frustrated 🤬 dismounted and to bed.
Greetings Wolfgang