Topics

Polar alignment through main scope #iEXOS-100 #alignment #sharpcap


Tommy
 

Hello everyone,

I have a newbie question. I am picking up a ZWO asi120mc-s camera that I was going to use on my 50mm Orion guide scope to polar align with Sharpcap. My question is, can I just use this on my main scope to polar align and use it to image as well? Or will the polar alignment only work on my guide scope? I have the iexos-100 Mount and a Astro tech 60ed scope. I also use a Nikon d5600 for imaging. Thanks in advance for the advice.

Tommy


Skull HQX
 

Hello Tommy,

Short answer is no, it won't work.

SharpCap Pro needs an in-camera field of view of between 1 to 2.5 degrees. When plugging your ZWO ASI120MC-S and the Astro Tech AT60ED into a calculator you'll end up with an in-camera field of view of 0.76 x 0.57 degrees. So your field of view is just too tight.

The Orion 50 mm guide scope will give you an in-camera field of view of 1.63 x 1.22 degrees, which would be fine.

Regards


 

Tommy,
 
I've done a polar alignment with my D5300, BYN and Sharpcap.  It did work, but it was slow and clumsy compared to using the guidescope and its camera.  One of those things that you do once, just to see if it you can make it work.  :-)
 
My $0.02 - simpler and faster to just use the guidescope + sharpcap.  Then once polar aligned, disconnect sharpcap and when ready for guiding, connect up PHD2.
 
HTH...
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


FishWithFeet <jeff.paules@...>
 

Hello-

I'm frugal, and use Roberts technique.  I setup the D5300 to shoot 1/3rd second shots at iso 1600.  Pause is set to 2 seconds, 200 frames. 

Then bootup Sharpcap and use folder monitor camera.  

Since I know roughly where polaris should be in the frame now I can get a SharpCap deemed "excellent" polar alignment in roughly 70 frames, or  2 minutes. 

In short since you intend to buy SharpCap regardless you can test it yourself with your camera and know. 

I shoot through a Sigma 150 -600, and I have PA'ed at 150 & 200 mm. I never tried 600mm but not sure why I would.

On Sat, Feb 1, 2020, 11:11 AM Robert Hoskin <devonshire@...> wrote:
Tommy,
 
I've done a polar alignment with my D5300, BYN and Sharpcap.  It did work, but it was slow and clumsy compared to using the guidescope and its camera.  One of those things that you do once, just to see if it you can make it work.  :-)
 
My $0.02 - simpler and faster to just use the guidescope + sharpcap.  Then once polar aligned, disconnect sharpcap and when ready for guiding, connect up PHD2.
 
HTH...
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Skull HQX
 

Considering Tommy uses the iEXOS 100 I'd like to add that if he wants to use the PA method as described by Robert and FishWithFeet above, he should consider buying the optional iEXOS100 Azimuth Adjuster Adapter. Otherwise adjusting the mount will be very hit and miss and frustrating.


 

FishWithFeet,
 
Ahhh... A Sigma and 150-200mm, 1/3s shots!  No wonder you're getting along better.  Are you working unguided? 
 
My D5300 + scope were at 621mm and my PA exposures had to go out to about 15s with that combination (trudge, trudge).   
So I had both the slow exposure rate and the folder setup/teardown time - just didn't make sense vs the faster guidescope w/ its camera.
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


FishWithFeet <jeff.paules@...>
 

Yes, unguided.

I too would recommend the Azimuth adapter.

Full disclosure, I have had the iEXOS-100 roughly 1 week, and with the intermittent clear skies I have been chasing rookie mistakes and have no image to show yet.

My biggest error was leaving my lenses image stabilization on.  So, I could watch my target stay rock solid in liveview, but as soon as I would take a shot I'd get hook shaped star trails with any exposure I over 1/3rd sec.  I'd then park the scope open sharpcap and confirm excellent alignment.  

Solved my user error issue in a different discussion this past Thurs. This was proven by taking daytime photos with the same settings on the mount.  One with stabilization on one off.  Stabilization on resulted in a blurry image, off sharp image.  I get a new clearsky attempt tomorrow.

I'm pretty confident that I will get good images then, because when I would go to to BackyardNikons Drift and Align feature, I could watch my target not budge on the reticle for over 5mins trying to solve my issue.

At 150mm the Sigma is f5.6, so,if the OP's scope is of the same speed same settings should work.

On Sat, Feb 1, 2020 at 11:50 AM Robert Hoskin <devonshire@...> wrote:
FishWithFeet,
 
Ahhh... A Sigma and 150-200mm, 1/3s shots!  No wonder you're getting along better.  Are you working unguided? 
 
My D5300 + scope were at 621mm and my PA exposures had to go out to about 15s with that combination (trudge, trudge).   
So I had both the slow exposure rate and the folder setup/teardown time - just didn't make sense vs the faster guidescope w/ its camera.
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Skull HQX
 

On Sat, Feb 1, 2020 at 06:09 PM, FishWithFeet wrote:
At 150mm the Sigma is f5.6, so,if the OP's scope is of the same speed same settings should work.
Unfortunately his Astro Tech AT60ED + ZWO ASI 120MC-S combination provides far too little field of view to do PA using SharpCap. 
Alternately, if he uses his Nikon D5600 with the AT60ED the field of view would be 3.74 x 2.49 degrees, which seems too large for SharpCap to use.

But this is all getting a bit far from PMC-Eight related topics. ;)


Tommy
 

Thanks for the info. Could I just make azimuth adjustments via explore stars slewing? Or is this not possible?


 

Tommy,
 
Nope.  Think about what the axes of your mount are doing during tracking and it should become clear.  
 
In a perfect world, the RA axis is in line with the celestial pole. The RA's tracking rate is basically countering the Earth's rotation, and the stars ahead of it appear to stay in the same place.  The DEC axis lets you aim the scope to either side of that rotational axis.  
 
So, let's say that that you did set the altitude on your mount's RA axis reasonably well, but just plunked the tripod down without much concern for the azimuth.  In other words, you have a poor Polar Alignment.  But one way or another, you do manage to slew to a target of interest and track.
 
What happens next?  Well, the RA axis will rotate, but it will not rotate in line with the celestial pole, so your target will drift away on you.  
 
If you are doing unguided AP, you should see streaks quite quickly from a bad PA.  If you are guiding, PHD2 will try to stair-step the DEC and RA movements to keep your target centered and your stars round, but there are limits to this, and where those limits are will depend on the size of the error, guiding and imaging resolution, target location, etc.  Might be ok for a given session, might not.  It's not uncommon for AP'ers to sometimes deliberately leave a small error in their PA, just to keep the DEC gears moving slightly - but we're talking minor, not major.
 
Bottom line, a good polar alignment is a prerequisite for good tracking. You didn't say which mount you have, but I assume from the question that you have an iExos-100, which does not come with an azimuth adjuster (the EXOS2 does come with one).  
 
The Az adjuster is recent option, and some here were doing creditable AP long before that. I think nudging tripod legs and fiddling with mount head bolts were the usual techniques for doing the Az adjustment, back in the day.  Just do the best with what you have - but the Az adjuster will help you get a better PA faster.  FWIW...
 
As to Explorestars, that's mostly for visual, rather than AP.  For AP, you'd likely use something based on either ASCOM or INDI - but that's really a whole 'nother thread's discussion.
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


FishWithFeet <jeff.paules@...>
 


I just thought I'd close the loop.  I posted this photo elsewhere on the forum, however I did want to say that the PA through SharpCap allow this photo of 80 stacked 30 sec. Exposures unguided.

I also aligned without the Azimuth adjuster in under 2mins, but I'm not sure this technique is best for the longevity of the equipment.

Same setup, 200 1/3rd iso 1600 photos, folder monitor camera.
 
In ShapCap polar align, dial in Altitude.  Then as per the SharpCap process your Right Ascension is parallel to the ground.  Using the counterweight bar I find that I can make fine adjustments with a little huge forward or back to get it "left" or "right"

During the capture process the mount fell out of alignment a few times (noticed by trails) I was able to also use this technique between exposures to counteract the drift.

I still think the AZ fine adjusters are the way to go, but I ran into an issue where I ordered mine from Andromeda to get free shipping.  The sell the old version of the part that does not have the pieces needed to use with the iEXOS stock mount.  If you do decide to buy this, buy from Explore Scientific direct.


Skull HQX
 

On Wed, Feb 5, 2020 at 05:36 AM, Jeff Paules wrote:
I also aligned without the Azimuth adjuster in under 2mins, but I'm not sure this technique is best for the longevity of the equipment.
I'm not sure what you mean exactly. Can you elaborate? 

Regarding the resulting picture. It looks good Jeff. The core isn't overexposed and there is nice detail. For constructive feedback I would say regarding color, on my calibrated screen, the nebula is a bit too purple and the skyglow/larger nebulae a tad too blue/cyan. The core should be teal colored. But only if you'd ask for such feedback! ;) It's a good result as it is already.

Clear skies!


Jeff Paules <jeff.paules@...>
 

Skull HQX

I really do appreciate the feedback, and given the forum rules I wouldn't mind going into more detail with you in another space.

Regarding elaborating I'll do my best:

1.       Set-up and level the tripod & snug tight your mount to tripod know (located under the tripod middle)

a.       Not to be too insulting, but I messed this up.  Please check to make sure your bubble level works, if not find a fix.  Mine was way off.

2.       Attach and balance camera w/ lens

a.       Balance RA

b.       Balance Dec

3.       Attach your camera to your imaging software

a.       Power on

b.       Connect cable

c.       Connect button in software

4.       Start an imaging plan

a.       200 frames

b.       Iso 6400

c.       Pause 2 sec.

d.       Same images to a folder you know, make sure it’s empty

5.       Open SharpCap

a.       Choose folder monitor camera

                                                                                       i.      Select the folder you pointed your imaging software to

                                                                                     ii.      Press play

6.       Start up Polar Align

a.       Follow the Tutorial

                                                                                       i.      Solve home position – next

                                                                                     ii.      Solve 90D Dec turn – Next

                                                                                   iii.      Adjust to the SharpCap Numbers

7.       Solving to SharpCap numbers

a.       Use the altitude knob to zero in the up / down number in SharpCap

                                                                                       i.      Once your within 00:00:XX where xx is any number & you’re good

b.       This is the part I’m not sure I’m a huge fan of – To zero in the left Right in SharpCap with your thumb and finger grab the tip of your counterweight bar and push the bar forward for “right” and pull backwards for “left”

                                                                                       i.      This will pivot the mount on the Azimuth axis, but since you are extended so far out of the center of rotation you are able to make really fine adjustments quickly.

                                                                                     ii.      This will add torque to the counterweight bar and possibly loosen the bars connection to the axis over time.  Not sure, but likely.

c.       Do this till your Left right reads 00:00:XX were XX is any number, and you should now have an “Excellent” polar alignment in SharpCap

 

Using this method I’m able to get an excellent polar alignment in SharpCap in under 70 frames or (.333+2)*70=163.31 secs. Or 2.72 minutes.

 

Since Orion was just nearly directly above me I was able to use this grab the counterweight bar tip adjustment to do drift alignment corrections on the fly when I noticed a few frames in a row with identical trails.

 

Does that clarify.

 

And again, thanks for the photo feedback.  Quickly, as for the color you’re right.  I initially balanced my blacks by choosing a black point for reference and getting each the R, G, and B to all read the same numbers.  Ensuring the sky is black, and thus the image is color corrected.  But then while “juicing” saturation things got wonky and I edited it on the fly.  I’ll review my process to correct this error. 


Jeny@
 

I'm curious if somebody tried to plate solving with guide scope and SharpCap? I believe SharpCap can use Astrotortilla for it.


On Sat, Feb 1, 2020 at 10:48 AM, Tommy
<darko7411@...> wrote:
Hello everyone,

I have a newbie question. I am picking up a ZWO asi120mc-s camera that I was going to use on my 50mm Orion guide scope to polar align with Sharpcap. My question is, can I just use this on my main scope to polar align and use it to image as well? Or will the polar alignment only work on my guide scope? I have the iexos-100 Mount and a Astro tech 60ed scope. I also use a Nikon d5600 for imaging. Thanks in advance for the advice.

Tommy


 

Jeny,
 
Not quite sure what scenario you have in mind, but FWIW, Sharpcap does not need a separate Astrotortilla installation to perform a Polar Alignmnent.
 
If you're talking about using Sharpcap to do a plate solve on your imaging target through your guidescope and then use something else to run a different camera (say, BackyardWhatever and a DSLR...) through your imaging scope, that would not likely be a good idea.  I think you'd want to do the plate solve on what the *imaging* camera sees.
 
The whole point of plate solving is to get your target centered quickly and reliably in the field of view of your imaging camera.  Your guiding FOV and your imaging FOV are unlikely to be the same, let alone precisely aligned.  If you are using a control program of some kind for your imaging camera, the thing to do is get Astrotortilla (or equivalent) integrated with THAT.  
 
I use BackYard Nikon with mine, integrated with Astrotortilla, and plate solving really is magic. :-)  
 
HTH...
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Tommy
 

I just picked up the AZ adjuster for my iEXOS-100 mount and polar aligned via Sharpcap. Wow what a difference with the AZ adjuster, so much easier. Thanks for the heads up. I got an excellent my first time out in under 10 mins. It will only get easier as time goes on. Now I just need to figure out how to perfect my star alignments!
--
Cameras: Nikon D5600, ASI ZWO120
Scope: Astro-Tech 60ed, Orion 50mm
Mount: ES-iEXOS-100