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Old 17-08-2014, 10:53 AM
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Imaging an object over several nights question

I want to image an object over several nights to build up a good signal.

What is the best way or options to make sure the object is in the same position on the sensor night after night. I have read about 'plate solving' however I don't have the software to do this.

I would be interest to here how this is done as many images on this forum are taken over many nights.
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Old 17-08-2014, 11:14 AM
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RickS (Rick)
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Plate solving is the easiest method to guarantee accurate pointing to the same target night after night. Astrotortilla and Elbrus are a couple of free plate solvers. I use Astrotortilla for blind solving and it's very good but it was fiddly to set up...

Cheers,
Rick.
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Old 17-08-2014, 11:57 AM
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Thanks Rick. I might give Astrotortilla a go.

Cheers
Dave
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Old 17-08-2014, 12:02 PM
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Octane (Humayun)
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What image acquisition software are to using?

H
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Old 17-08-2014, 12:03 PM
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You won't regret adding plate solving to your arsenal of tools, Dave!
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Old 17-08-2014, 12:14 PM
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Not sure what image acquisition software you're using, but Sequence Generator pro works with all the hardware you've listed, manages the plate solving via Elbrus, and if you have a robofocus or similar will be able to refocus for you as well. Cheap too!
Cheers,
Andrew.
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  #7  
Old 17-08-2014, 12:18 PM
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I'm currently using Nebulosity 3 for image acquisition.
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Old 22-08-2014, 11:03 AM
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Pinpoint is very good. Easy to set up. Great at blind solving. $US149. http://pinpoint.dc3.com/
Geoff
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  #9  
Old 22-08-2014, 11:22 AM
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AstroTortilla talks directly to Nebulosity 3. It is terrific, once (as Rick notes) you get it tuned.

The trick was to first estimate the scale (arcsec/pixel), then try some solves until I got a fit and then use the reported image dimensions to refine my scale estimate. After a few iterations, I had it nailed. Giving a small margin of error (e.g. if my estimated value was 1.66 arcsec/px, then I would use lower=1.63 and upper=1.69), I was able to get completely consistent fits in under 10 sec - blind. With pointing information from the mount, typical solves take 5-6 sec, and it almost never fails now.
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Old 23-08-2014, 09:20 AM
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http://nova.astrometry.net/upload is my favourite option. I find it's quicker than Astrotortilla, which can be time-consuming to configure and download index files. You can get accurate results uploading a jpg or a Binx4 (this saves time when uploading).

Once I get a solve, I make offset RA/Dec corrections to my mount to get to the target. It usually takes a few iterations to get it spot on.

Sam
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  #11  
Old 23-08-2014, 09:53 AM
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Pardon the hack, but does anyone know if any of these plate solving apps are mac compatible?

Cheers
Andy
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  #12  
Old 23-08-2014, 10:05 AM
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Astrometry is written for UNIX-like systems (like Linux), but Mac OS X is one of those too...check out the Astrometry build instructions... http://astrometry.net/doc/build.html#build

If you have any experience with compiling software in a Linux environment it should be pretty straightforward.

Incidentally, the Windows build of astrotortilla bundles Cygwin, which is a UNIX-like environment that runs on top of Windows.
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  #13  
Old 26-08-2014, 03:02 PM
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+1 Plate solving. There are plenty of links on the internet which describe how this works and how to go about using it (depending on what software you end up choosing of course). Especially with your set up shouldn't be too hard to set up

I personally use MaximDL and the plate solving on the software is amazing. If you decide thats all a bit difficult to set up, this is what I did before I set up plate solving:

1. Get the original image. Do a quick stretch so I can see the stars & object clearly.
2. Find the center of the image. Could use Paint or even just a ruler against your screen
3. Take a 15 or 30sec 2x2 or 3x3 binned image of your current image and then compare the center to the one from the original.

If you dont have EQdirect or ability to use a "Point Here" feature (where you click on the image and it will move the scope to center where you've clicked), its a royal PITA to center an object manually with the hand controller. If you do choose to go down this path make sure you've got your lodestar all calibrated, then center. Otherwise during calibration it will move scope off center and have to frame again!
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Old 26-08-2014, 07:55 PM
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I use the BYO Eclipse feature and overlay an image from the previous session.
If the image isn't oriented exactly the same, DSS can derotate it whilst stacking.
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  #15  
Old 27-08-2014, 10:12 AM
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I probably should upgrade to plate solving err..and automated focus ...buuut I just goto the object, take a quick snap, open a sub from the previous session and compare the positioning by blinking the two in Astroart, I then make any pointing/framing adjustments via the mount control, take another quick snap, do some more adjustments and repeat until I am happy...takes me about 10min usually.

I imagine plate solving would be a good have to do nothing alternative but the above works pretty well exactly the same, just a manual version

Mike
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  #16  
Old 27-08-2014, 12:14 PM
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marc4darkskies (Marcus)
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Quote:
Originally Posted by strongmanmike View Post
I probably should upgrade to plate solving err..and automated focus ...
Do you also get your drinking water from the well on your way back from the out house Mike?

Dave, depends on how often you have to recenter (to account for drift or going off target for focusing for example), what your threshold of pain is for wasting time (instead of imaging) and how accurately you want/need to recenter. Plate solving is required of course but to make your life easier you need to close the loop and have software automatically sense the adjustment to make after the plate solve and then move the mount. I use TheSkyX / CCDAP but I understand Astro Tortilla will close the loop with pointing info from the mount. I think TheSkyX also does closed loop slews now on it's own(?)

When I'm focusing (usually off target), getting back to the target within 3 arc seconds takes 2 iterations and a little over a minute with most of that time being spent downloading 2 plate solve images from my camera. I don't have to lift a finger
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Old 27-08-2014, 12:34 PM
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Quote:
Originally Posted by marc4darkskies View Post
Do you also get your drinking water from the well on your way back from the out house Mike?
Yes but... it is a beautiful bucket

Quote:
I don't have to lift a finger
I still use the yellow pages too, to do my walking
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  #18  
Old 27-08-2014, 03:19 PM
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Quote:
Originally Posted by jjjnettie View Post
I use the BYO Eclipse feature and overlay an image from the previous session.
If the image isn't oriented exactly the same, DSS can derotate it whilst stacking.
oooh I didn't know about this will check it out!
thanks for the heads up!

Cheers

Rusty
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  #19  
Old 28-08-2014, 06:43 AM
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Octane (Humayun)
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I don't know where I'd be without plate solving. Building mosaics tests your patience at the best of times, I can't imagine how much harder it would be without it!

PinPoint is the bomb.

H
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