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Can I use SharpCap's plate solving function during CGEM alignment?

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#1 Borodog

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Posted 03 December 2021 - 05:15 PM

After powering up my CGEM I go through the 2 star + 4 calibration star alignment procedure, where you align in the finder (I use a green laser instead) and then re-align in the eyepiece. I generally skip the second step because I have a camera in already and I use SharpCap's plate solve feature to correct any slews. But can I use the plate solve feature during CGEM alignment during the procedure? As in, slew to first star, correct with green laser, , plate solve in SharpCap, hit Enter and Align on the hand controller, next star?

 

 



#2 gcardona

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Posted 03 December 2021 - 05:28 PM

If you plate solve you don't even need to align. The plate solver and Sharp Cap should center your target regardless of the alignment procedure (polar alignment is required, however.) The 2-star + other stars alignment is used to calibrate the goto in the mount when using the hand controller, so if you don't use the hand controller to center your targets, no need to align. That's the advantage of plate-solving.


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#3 John O'Grady

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Posted 03 December 2021 - 05:37 PM

If you plate solve you don't even need to align. The plate solver and Sharp Cap should center your target regardless of the alignment procedure (polar alignment is required, however.) The 2-star + other stars alignment is used to calibrate the goto in the mount when using the hand controller, so if you don't use the hand controller to center your targets, no need to align. That's the advantage of plate-solving.

Gabe is right on this money with this advice.

I used to have a CGEM and would do a one star alignment, get the mount pointed and centered on something like Mizar.

Not needed, you just need to make sure the mount is initialized set to the home position then go from there.

 

The first platesolve on the initial slew is likely going to fail, but provided you have fail over to blind plate solver setup, that should recover.

From there, platesolves with ASTAP or platesolve2 should work from there.  I haven't had my CGEM mount for ~4 years, so it is possibly I am forgetting a step.

 

EDIT: Not having used sharpcap, I'm not familar with it's platesolving mechanism.  So, I'm assuming it has a blind plate solver option (or failover).

 

Good luck - John


Edited by John O'Grady, 03 December 2021 - 05:40 PM.


#4 Borodog

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Posted 03 December 2021 - 05:45 PM

Hmm. But if the mount is not accurately aligned, won't all the slews be significantly inaccurate requiring a lengthy plate solve every time? Or are you saying that somehow the first plate solve can make all the rest of the slews accurate? How can that be, given that it takes 6 stars to accurately align the mount? Not trying to be argumentative, just trying to understand. If what you're describing works, it would be great, because it would save boucoup time during setup.

Edited by Borodog, 03 December 2021 - 07:15 PM.


#5 robbieg147

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Posted 03 December 2021 - 06:28 PM

I only do some form of alignment if doing visual which is not very often and I would normally use Starsense.

 

For imaging you just need to be accurately polar aligned, do some form of quick align, slew to your target which will be off, plate solve and sync and job done.

 

I would stay on the same target all night, but if you wanted to slew to another target just repeat the slew / plate solve.

 

I don't use blind plate solving which takes a bit longer, but I would not call this lengthy just a few minutes.



#6 gcardona

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Posted 03 December 2021 - 06:32 PM

Hmm. But if the mount is not accurately aligned, won't all the slews be significantly inaccurate requiring a lengthy plate solve every time? Or are you saying that somehow the first plate solve can make all the rest of the slews accurate? How can that be, given that it takes 6 stars to accurately align the mount? Not trying to be argumentative, just trying to understand. If what you're describing works, it would be great, because it would same boucoup time during setup.

Your first solve will sync the mount to the sky position, like doing a 1-star alignment. Subsequent slews will be accurate enough to get the plate solver to center correctly.



#7 Mark Lovik

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Posted 04 December 2021 - 02:17 AM

If you use a camera to polar align, camera to plate solve and center ... who cares about the process if it works for you.

 

I use sharpcap to polar align and platesolve (during one star alignment) .. no eyepieces or long process necessary.   For alignment ... slew to the first star, platesolve and center, then press the align button.  If you are polar aligned and have no cone error (or stored from a previous 3 star) you should have clean goto with a simple 1 star alignment.  Use the first bright star for refined focus.  No muss and no wasted time.  Plate solving tends to be faster for me when I start out with a clean goto.   I also tend to use the main scope and camera for all of this. ... as long as the max fov is a half degree or better.

 

I got up last night, setup my mount and scope, polar aligned, mount one star alignment w/ platesolve, fine focus on the mount align star, setup a dark for the night.   Was actively imaging comet Leonard and M3 in under 30 minutes ... the last 5-10 minutes was fooling with framing the 2 objects.  So get a clean process as a habit and stick with it.  Get so you can almost do it in your sleep ... just about did that last night.  I no longer even bother with any finder.

 

PS ... I imaged with my doublet apo last night.  It could handle the abrupt temperature change within 30 minutes.  My larger triplet or SCT need longer to cool down before things settle, so I need to set the scope outside a bit before starting the process.  


Edited by Mark Lovik, 04 December 2021 - 02:33 AM.



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