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Question on DSLR + iOptron Skyguider Pro Polar Alignment with Sharp Cap & ZWO Guidescope and camera

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#1 Zanetti2102

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Posted 24 September 2020 - 12:28 AM

Wow I love this site! I have learned so much from all of you and I am thankful for that. So I have been imaging for a couple of years now using an Ha modified Nikon D5500 and a Tamron 150-600mm G2 that has been treating me well, but when I finally decided to start auto-guiding and ran into some issues and wanted to see if anyone out there could provide insight or tell me what I'm doing wrong. Beyond the camera and lens mentioned earlier I have a ZWO 120mm-s and the ZWO 30mm f/4 attached to the hot-shoe and it is very sturdy with no wobble. I get "good" polar alignment in Sharp Cap and PHD2 looks ok +/- 2 arc seconds but the problem is I can get less star trails and longer exposures with out all of this gear! I could get 1 min exposures unguided at 600mm without the guide cam using the built in polar scope, but now I'm at 30 seconds and starting to see star trails with the guide scope. Here is my theory and I welcome all thoughts and suggestions: I think the problem is the guide scope alignment vs. the Skyguider Pro main pivoting axis point is a problem for a accurate polar alignment due to the need to have to "eyeball" the left right movement of the round declination camera/lens mounting block (the round piece that attaches the lens tripod foot or camera to the declination bracket). Does that makes sense? In comparison to telescopes that have the dovetail mount for the guide scope built-in so there in no swivel from left to right like the Skyguider Pro. I'm truly baffled how people are getting 5 minutes of guided exposures on the Skyguider pro with a guide camera mounted anywhere other than using iPolar or something that is placed right in the axis of the polar scope?? Am I way out of line here or has someone figure out a way to perfectly line up there DSLR mounted guide scope on a Skyguider Pro?



#2 mmalik

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Posted 24 September 2020 - 07:35 AM

I think the problem is the guide scope alignment vs. the Skyguider Pro main pivoting axis point is a problem for a accurate polar alignment...

How are you polar aligning? SkyGuider polar scope is of poor quality and doesn't come calibrated. You'll be lucky if you can get it all calibrated/aligned. Best would be to forego of the (polar) sopce based aligning (PA). Use PoleMaster... for PA and don't guide at all if you are imaging less than 3-5 min subs. Note: Even with guiding, you need accurate PA. Regards

 

 

Note: More here...


Edited by mmalik, 24 September 2020 - 03:44 PM.


#3 Zanetti2102

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Posted 24 September 2020 - 11:25 AM

Thanks for the tip. I will need to research this PoleMaster more. For PA'ing I was using the built-in scope and could get up to 1 minute exposures at 600mm. By adding the guide cam/scope and trying to do polar alignment with the guide cam/scope I can't get more than 20 second exposures at 600mm without star trails. The premise of PA with SkyGuider seems wonky. The fact that you need to "eyeball" the 12 o'clock position in the scope in order to get the grid to illuminate is not accurate, but better than trying to PA with guide scope/cam mounted on the camera...which apparently add a whole new layer of guess work. I'm going to try to PA with the built in polar scope tonight and try to guide to see if that helps.



#4 DJL

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Posted 24 September 2020 - 02:33 PM

Peter Zelinka on YouTube uses the same lens with a Nikon DSLR and ZWO guide scope and camera. However he switched from mounting it on the hot shoe to a DSLR L bracket.

 

- Hot shoe: https://www.youtube....h?v=6WuBKfo_KMo

- L bracket: https://www.youtube....h?v=Cl1GD7LgSrY

 

I am doing this with my Star Adventurer, Canon DSLR, L bracket, WO 32mm guide scope and ZWO guide camera. I did a time trial last night up to 4 minutes before clouds rolled in.



#5 mmalik

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Posted 24 September 2020 - 08:53 PM

The premise of PA with SkyGuider seems wonky.

Agree. Know that SkyGuider can only guide on 'ONE' axis (...has only one motor). Accurate polar aligning and balancing (slightly East heavy) is the only way to about guiding. Anything short will results in what you refer to as "wonky" behaviour. Perfect guiding by all means but in the end opt for NO guiding. Regards


Edited by mmalik, 24 September 2020 - 10:34 PM.


#6 17.5Dob

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Posted 24 September 2020 - 09:53 PM

You ABSOLUTELY can't mount a guide cam to your hot shoe....secondarily, you can't autoguide a "camera mount" ..you might improve your results at 300mm, but there's no way  you can use 600mm....even with a quider



#7 Zanetti2102

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Posted 25 September 2020 - 12:23 AM

I have seen Peters videos and I still do not get how anyone using that method whether hot shoe or L-bracket can get a good PA. Just look at the mount/adapter for the lens/tripod foot to the Skyguider Pro?!? It's round with no marks/grooves to tell you if you are lined up in parallel with the mounts central axis. So I tested my theory tonight and looks to be right-on about using the built in polar scope for PA instead of the zwo 120mm-s hot shoe mounted for polar alignment. I just took about 12 - 7 minute long exposures of the Whirlpool Galaxy auto-guided using PHD2 and using the built-in ioptron polar scope for PA + ioptron app and it looks good-no trails... at least for these novice eyes it does. I'll post my results tomorrow. Funny thing is with the goofy polar scope and red markings built-into the Skyguider Pro you still have to "eyeball" that red grid and make sure it is truly straight up/down and left/right and I'm still able to way better results with that method rather than using Sharp cap and the guidescope/camera! Peter and all of you that have mastered 7 minute long exposures at 600mm using the L-bracket or hot-shoe mount guidescope/camera must be REALLY good at eyeballing your alignment with central axis of the Skyguider Pro and your guide scope/camera! Anyway I'm just getting into guiding and wanted to learn more about before buying a real mount. I understand that all of these problems go away once you move to dovetail mounts and a telescope. Hopefully this discussion can help someone else that is having difficulties trying to polar align with a guide camera/scope on a Skyguider Pro. Thanks everyone for your insight.



#8 Zanetti2102

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Posted 25 September 2020 - 10:34 AM

Here is a crude attempt at the Whirpool Galaxy with a D5500 and the Tamron 150-600mm G2 at 600mm stopped down to f/7.1. 12 images taken at 7 minutes exposure each. No flats or bias or noise reduction was used. It is a crop so you can see the stars better.  I used the built-in polar scope in the Skyguider Pro along with the app for polar alignment. Auto-guiding was done with ZWO 120mm-s and PHD2. The Whirlpool Galaxy is very close to the horizon here and there was haze/clouds moving in so I wasn't able to capture much detail. I was impressed that I could get 7 minute exposures without much star trail! I'd like to push it even further...This just proves that trying to polar align on the Skyguider Pro with anything other than a device that is installed exactly where the built-in polar scope is located i.e. iPolar, Polemaster etc. is just not going to yield very good results-unless you are an expert "eyeballer."

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#9 polslinux

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Posted 25 September 2020 - 01:46 PM

7 minutes subs?? :O
Congrats man!! What tripod are u using?

#10 Zanetti2102

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Posted 25 September 2020 - 02:23 PM

Thanks...that was my first time successfully guiding with the Skyguider Pro after being stumped with the polar alignment debacle. The wind was very light last night and I had the tripod on concrete. I'm using this clunky pistol grip Ravelli tripod I got off of Amazon a few years ago but this looks like a re-badge of the same tri-pod:

https://www.amazon.c...ctronics&sr=1-1

Obviously I'm not using the pistol grip. Looking at Stellarium now I should've picked The Pinwheel galaxy since it is higher in the sky. 


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#11 polslinux

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Posted 26 September 2020 - 07:22 AM

Where did I attach the guide scope and camera? To the L bracket?
Can you share a photo of your complete setup? :)
Thanks

#12 DJL

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Posted 26 September 2020 - 10:04 AM

I have seen Peters videos and I still do not get how anyone using that method whether hot shoe or L-bracket can get a good PA. Just look at the mount/adapter for the lens/tripod foot to the Skyguider Pro?!? It's round with no marks/grooves to tell you if you are lined up in parallel with the mounts central axis. So I tested my theory tonight and looks to be right-on about using the built in polar scope for PA instead of the zwo 120mm-s hot shoe mounted for polar alignment. I just took about 12 - 7 minute long exposures of the Whirlpool Galaxy auto-guided using PHD2 and using the built-in ioptron polar scope for PA + ioptron app and it looks good-no trails... at least for these novice eyes it does. I'll post my results tomorrow. Funny thing is with the goofy polar scope and red markings built-into the Skyguider Pro you still have to "eyeball" that red grid and make sure it is truly straight up/down and left/right and I'm still able to way better results with that method rather than using Sharp cap and the guidescope/camera! Peter and all of you that have mastered 7 minute long exposures at 600mm using the L-bracket or hot-shoe mount guidescope/camera must be REALLY good at eyeballing your alignment with central axis of the Skyguider Pro and your guide scope/camera! Anyway I'm just getting into guiding and wanted to learn more about before buying a real mount. I understand that all of these problems go away once you move to dovetail mounts and a telescope. Hopefully this discussion can help someone else that is having difficulties trying to polar align with a guide camera/scope on a Skyguider Pro. Thanks everyone for your insight.

 

The polar alignment scope must be pointed towards the pole star and then you can use a phone app to get as good a polar alignment as possible, manually.

 

There are systems for improving polar alignment - iOptron iPolar camera with software running on Windows or Mac; Polemaster camera with Sharpcap software, Windows only; and ZWO ASI Air Pro connected to a ZWO guide camera and running software on its built in Raspberry Pi and controlled by your choice of iOS or Android phone or tablet. I don't have any of these yet, but I have decided on the ZWO ASI Air Pro because its other features (USB hub, dew heater power supply, capture automation etc). 

 

The guide scope does not point at the pole. In fact it can point anywhere but some directions give better results than others.  The goal is to correct the errors in the polar alignment, and those errors are smallest at the pole and biggest far away from the pole. People typically align the guide camera with the main camera's lens or telescope. I guess if you were photographing Polaris, the guide scope would be pointed at the pole :-). 

 

Peter Zelinka suggested a 30mm ZWO guide scope and mini guide camera could be attached to a DSLR. Initially he did this on the camera's hot shoe, but if there's any wobble in the attachment, the guiding goes wrong. So his next idea was to attach the guide scope to his camera's L bracket using an Arca Swiss clamp. His method still relies on a single screw between the Arca Swiss clamp and the guide scope, meaning that if push comes to shove, the guide scope could rotate around that screw. I will post a photo of my arrangement which involves more clamps but prevents any possibility of rotation. I am also using a William Optics mini guide scope, https://williamoptic...uide-32mm-scope.

 

The components of the guiding system are a guide scope with guide camera, guide camera attached to mount via the ST4 cable (which looks like a US telephone cable) and guide camera attached via USB to a computer running PHD2. 

 

I run PHD2 on Mac but Windows and Linux are also available. PHD2 chooses a star and observes it moving while the mount is running. If the star appears to move in RA, it sends speed up or slow down corrections to the mount. For Star Adventurer and SkyGuider, only RA movement is possible. Dec guiding must be turned off in PHD2 for these mounts as there is no automated Dec movement. For mounts with Dec automation, PHD2 also sends Dec correction. 

 

I think it's very valuable to get guiding running on Star Adventurer or SkyGuider, as it's a step in the learning curve, and once you get over it, you're ready for the next step up in capability. 


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#13 DJL

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Posted 26 September 2020 - 10:56 AM

The DSLR is attached to a Really Right Stuff L bracket, which has a magnetically attached allen key built in to the base. The side bracket has to be extended to allow the USB cable to fit.

 

The WO Uniguide 32 has 3 1/4" 20 screw holes. I found a Leofoto lens plate with slots and 2 1/4" 20 screws.

The 2 way Arca Swiss clamp has a lock preventing rotation, and can be taken apart and reconnected at any of the possible 90 degree angles. 

 

Downside - it adds weight and is not balanced side to side. I am not using an Arca Swiss clamp to attach the main camera to the mount. I keep the Peak Design Clutch on the camera partly because it's fiddly to take off and partly to add safety while I attach the camera to the mount. The clamps and lens plate will be useful camera bag accessories when the guide scope moves to the William Optics telescope handlebar that it was designed to fit :-).

 

 

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#14 Zanetti2102

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Posted 26 September 2020 - 11:27 AM

That is helpful and is a very nice setup for mounting the guide-scope to the camera, but that doesn't really address the pivoting of the lens/camera mounting to the Skyguider Pro itself which makes a guide cam useless for polar alignment. It's the round nature of the sky guider pro's mount (see picture). This is what I was referring to as far as being being very difficult to align with the scope or pivoting axis of the Skyguider Pro. There are no marks indicating that you are parallel with SGP polar scope. I've heard of some people putting a mark on this round adapter and on the tripod foot of the lens to get lined up for polar alignment, but that sounds like way to much variability. The other option is using a fixed arca-swiss plate on the SGP, but then you lose all ability to adjust declination.

 

Also, I have the metal hot shoe adapter for the guide cam with the 2 locking pins and it does not wobble. I was able to to take 7 minute exposures so that part is all good. I'm just going to use the built-in scope since 7 minutes is great to me! 

 

IMG_2263.jpg

 

 



#15 DJL

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Posted 26 September 2020 - 12:01 PM

This video explains different mounting hardware and balancing for SkyGuider + telescope or lens and also for Star Adventurer - pricy and heavy but super nice William Optics parts or cheap and light Arca Swiss plate and iOptron "micky mouse ears" part. https://www.youtube....h?v=F4QxvZmdavc. Either way you should be able to rotate an Arca Swiss clamp for Dec orientation. I don't use an Arca Swiss clamp on the Star Adventurer - there's a Dec clutch for rough adjustment and worm screw for fine adjustment.



#16 Zanetti2102

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Posted 26 September 2020 - 10:05 PM

I love Peters videos and he does a good job but I still don't see an alternate solution for the built-in polar scope, iPolar, PoleMaster or any concoction that goes in the central pivoting axis for polar alignment. Maybe this is just a misunderstanding on my part, but as far as I see it polar aligning with a guide scope/guide camera on the Skyguider Pro does not work! (unless someone has McGyvered' a guide scope/cam into the recess of the built-in polar scope) That was my main problem and the mickey mouse ears approach is to blame. Maybe if we leave it at that, then others may find this helpful.




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