SharpCap Plate Solving - good/bad news

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stubblejumper
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SharpCap Plate Solving - good/bad news

Post by stubblejumper » Mon Dec 03, 2018 9:05 am

Since my initial GoTo with my iOptron CEM25P mount is not accurate, I wanted to use the plate solving function in v3.2. I set up All Star Plate Solving and SC was able to invoke it. The good news is that SC reported that ASPS had indeed plate solved my location and listed the RA/DEC coordinates. I was using an ASI 1600MM Pro (4/3 sensor) camera and a Nikkor AI 600/5.6 lens. The field of view is roughly 2 deg x 1 deg and that was set up in ASPS. On one of my plate solving attempts, SC adjusted the mount's position. All well and good but the star I used as a target, Schedar, wasn't in the FOV. In a couple of other attempts, I just asked SC to synch the mount. There was some irony that when I did a GoTo to IC11 (Pacman), Schedar showed up! The telescope control program I used was Starry Nights v6. It provided the initial RA/DEC settings for Schedar. I tried to get another GoTo Schedar in SN6 after plate solving but it didn't react. I have Stellarium and Cartes du Ciel but I am not familiar with them.

I would appreciate someone sharing their process for plate solving with SC.

Don

BlackWikkett
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Re: SharpCap Plate Solving - good/bad news

Post by BlackWikkett » Mon Dec 03, 2018 9:44 am

Hi,

I've not used ASPS with SharpCap but have used AstroTortilla. I also use CEM25P and have AT plate solving working usually solves and syncs in about 10-20 seconds once it has the frame to solve. Here's a few things to check that I've found will make solved images and syncs not line up.

1. verify the mount time / date. This will update from GPS once it has synced with enough satellites. Also make sure the device that is running your planetarium software has the same time as the mount
2. make sure you have the correct settings for day light savings time set in the mount
3. make sure your planetarium software and plate solver are using the same epoch. I've found JNOW works with CEM25P

Hope this helps these were all lessons I learned when I set up plate solving.

-Wikkett

stubblejumper
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Re: SharpCap Plate Solving - good/bad news

Post by stubblejumper » Mon Dec 03, 2018 10:35 pm

Thank you BW. I checked that Starry Nights and my laptop showed the same time. I forgot to check the mount's time. It would be an obvious source of error. What hurts my ego is that I wondered about a difference in timing but never thought of the mount.

As for Epoch, I'm lost!

It will be clear tonight, if the forecast is accurate and I intend to try it again. I wonder how Sharpcap knows the Field of View? It has the ASI1600's sensor specs. All Star Plate Solver wants to know the scope's specs so it presumably can calculate the FOV. I know SCap reported the FOV. Something figured it out.

Don

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Re: SharpCap Plate Solving - good/bad news

Post by oopfan » Mon Dec 03, 2018 11:11 pm

Don,

Two common epochs are JNOW and J2000. Most catalogs these days quote coordinates in terms of J2000 which are the RA and DEC of the object on January 1, 2000 12-noon Universal Time (UT). Those coordinates are measured relative to the vernal equinox at that precise time. Unfortunately the position of the vernal equinox changes as time marches forward due to precession caused by the Sun and Moon but also the planets. JNOW refers to the "epoch of date" or more precisely the vernal equinox right NOW at this instant. One can convert RA and DEC from J2000 to JNOW via a complex transformation of coordinates but thankfully software handles that for us. Wikkett is referring to the need to get all participants talking with respect to the same epoch. For example, if your planetarium software is sending J2000 coordinates to the mount but the mount is expecting JNOW then it will be off. These settings should be available in the preferences menu of your mount.

Brian

stubblejumper
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Re: SharpCap Plate Solving - good/bad news

Post by stubblejumper » Tue Dec 04, 2018 12:53 am

And thought it couldn't get any more complex.... You've reduced my confusion but increased my angst!

I don't recall ever seeing a setting for any of the many mounts I've owned over time. I'll check my CEM25P manual. I'll see if Starry Nights or Cartes Du Ciel have a setting.

Don

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Re: SharpCap Plate Solving - good/bad news

Post by turfpit » Tue Dec 04, 2018 1:55 am


stubblejumper
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Re: SharpCap Plate Solving - good/bad news

Post by stubblejumper » Tue Dec 04, 2018 2:33 am

I'm at it again tonight but am going with my Oiii filter and used Cartes du Ciel for telescope control. It slewed me close enough to Schedar for it to be in the FOV, which is better than normal. But after SCap did its plate solving with ASPS, I then went back to CDC to do a slew to Schedar. Nothing happened. Just like last night when I used Starry Nights. I don't know what the problem is other than SCap couldn't update the mounts position so SN and CDC thought they were already centered. Hmmm. I should have checked the handset and compared it to the SCap plate solve results. In 90 minutes the target, IC11/NGC281/Pacman nebula will transit and I'll redo the process. My meridian flips are not that accurate.

stubblejumper
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Re: SharpCap Plate Solving - good/bad news

Post by stubblejumper » Tue Dec 04, 2018 7:00 am

Thank you Dave. I remember seeing that section but I had no idea about what it meant. I am pretty certain that I left it at Equatorial but no recollection about the Epoch entries. I will check when I go out to shut down. The GoTo's after a meridian flip are always worse even when I go back to Zero Position and then use either my handset or Starry Nights or Cartes du Ciel and GoTo Schedar. I did check what my handset showed versus what Starry Nights reported. It was off by a couple of degrees. The FOV for my 600mm lens and ASI1600 is ~1.3 deg by 1.7 deg. It is clear that SCap doesn't adjust the mount's RA/DEC settings. Not sure what to do.

Don

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Re: SharpCap Plate Solving - good/bad news

Post by admin » Tue Dec 04, 2018 8:08 pm

Hi Don,

please post the contents of your SharpCap log after an attempt at plate solving. The logs should contain all the information that will be needed to work out what is going on including the position of the Mount before the solving starts, the solved position and the GOTO executed by SharpCap in order to move back to the original position.

Cheers, Robin

stubblejumper
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Re: SharpCap Plate Solving - good/bad news

Post by stubblejumper » Tue Dec 04, 2018 10:45 pm

Robin - where are the logs stored? I've looked in the SharpCap Captures folder and SCaps program folder.

Don

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