Plate solving

[PESKYWAABBIT]

So I take photos using BYEOS with my Canon DSLR. I have a Altair Astro guide camera hooked up to PHD2 which is plugged into the HEQ5 mount to correct for guiding. I have read about plate solving and I was curious. Does plate solving ONLY gives you the ability to get into the same place as a previous night by giving your EQMOD the right data to allow for easier multiple night data stacking and is not for guiding or part of the guiding mechanism itself.

Say I want to start trying this plate solving malarky. Would I:

Setup my scope, Polar align, 3 star align, Plate solve using a photo from my DSLR and not my Guide cam? and then continue to use PHD with guide cam to guide? 

Any replies are much appreciated.

 

[Vox45]

Plate solving uses a photo of a star field (from a guide scope or main camera, it does not matter) and searches in a catalog of stars to match that star field to the same pattern of star. 

You can easily test this by uploading a photo you already have and it will solve it and give you the name of the objects and coordinates

http://nova.astrometry.net/upload

You do not need to do a 3 star alignment. Plate solving is giving you the exact coordinates your mount is pointing to, so 3 star alignment is redundant.

-> polar alignment is needed to prevent field rotation on long exposure and it helps guiding a lot

-> 3 star alignment is to tell your software where the mount is pointing. Plate solving does the same thing as long as you sync when you get the platesolver solution

-> guiding is not related to plate solving, it only keeps you mount from drifting due to bad PA or mecanical errors of your mount

In my routine :

(1) I polar align using plate solving. In my case I use Ekos and Indi (a linux set of tools and protocol a bit like ASCOM/Eqmod)

(2) I then point my target using my sky atlas softaware (Kstars) and ask it to slew to that target

(3) the plate solving tool takes a photo that is then solved using the astrometry index that I have downloaded locally on my machine (and RPI3 in this case)

(4) When the exact coordinates has been "solved" The software updates my mount coordinates to that solution

(4) The mount is then moved to get closer to the target and the process is restarted until it gets within a predefined acceptable range of my target (30'' for example)

so without any 3 star alignment I usuall get my target smack in the middle of my camera sensor after 3 or 4 iterations 

So in your case you could use a photo from a previous session and ask the software to solve this photo and slew to the exact coordinates... that is possible as well. Or you could just point to the same target in your skychart software. Both methods are valid.

Edited November 13, 2019 by Vox45

[bottletopburly]

Plate solving is nothing to do with guiding, I use Apt  which has the ability to platesove built in once configured not used byeos so unsure if that has , I don’t even use a finder scope , i polar align using sharpcap, then switch to Apt  take a picture blindsolve , sync mount I can now slew to any object and if I platesolve off a previous nights image and use Goto ++ in APT slew to within a few pixels its that accurate.

[don4l]

If you can get platesolving to work, then I would say you should do it.  The easiest solver that I found for Windows is ASTAP.

I use platesolving in a few different ways.

I make a note of the Ra, Dec and rotation angle so that I can get back to exactly the same spot over several nights.

 

I also use the fact that Cartes du Ciel can display platesolved images.  This means that if I platesolve my current image and do a Sync, I can see if I am exactly on target. 

I use CCDCiel for my image acquisition and CCDCiel can display a platesolved image "frame" in CdC.  If this frame precisely matches the image that is already displayed in CdC, then I know that I am on target, and my camera is rotated to exactly the correct angle.  This framing only takes a couple of minutes and doesn't involve anynumbers.  Everything is done just by looking at the screen.  I hope this makes sense.

[dannybgoode]

I’ve just started playing with plate solving so I can acquire targets much more easily. So far I’ve managed to get APT to speak to speak to All Sky Plate Solver and blind solve an image I took where I just missed M81. APT then feeds the coordinates to, in my case Stellarium, and this shows me exactly where I was pointing. You set your scope and sensor up in Stellarium and it will put an overlay of what area the sensor is capturing. 
 

From there your can see what adjustments are needed to exactly frame your target. 
 

This was done in the safety of my dining room but tomorrow, assuming the clouds stay away, then I’m going to try it all live. 
 

Guiding is a fiddle once you’ve got PHD2 talking to the guide cam and got the guidescope focused. Really is very easy

[cjdawson]

In addition to using plate solving to line up the image night after night.  I also use plate solving in my polar alignment process.   I've used both the ZWO AsiAir  Polar alignment (I think it's running PHD2 under the hood) And Sharpcap Pro Polar alignment tool.    Both use platsolving to visually track that the scope is correstly aligned on the pole star.     Doing this has made my polar alignment a whole lot easier and much much much better at the same time.   I was lost without it.    Using platesolving to frame an image is also a nice to have for multiple sessions.

[Robny]

Curious......

How does platesolving help with PA? 

When doing PA you are aligning your mount against Polaris hour angle by adjusting the mounts AZ and Latitude, where as platesolving aligns and syncs your telescope position so you are targeting the correct place by adjusting and syncing its RA and DEC coordinates.....it does not adjust your AZ and Latitude?

Just wondering...

[discardedastro]

What cjdawson is describing isn't quite platesolving - just star tracking (track stars near the North and you can calculate the PA error, and then correct it).

[dannybgoode]

10 minutes ago, discardedastro said:

What cjdawson is describing isn't quite platesolving - just star tracking (track stars near the North and you can calculate the PA error, and then correct it).

To add to this - the plate solving comes into the equation simply so the software knows which bit of sky the scope is pointing at. 
 

From there the software knows which star is which then used to calculate the drift alignment. 
 

The more I dabble is this hobby the more I realise that there are some exceptionally clever people who quite freely give up their time to write software that makes our lives easier . How they work out all this stuff is beyond me!

[Robny]

Wasn't reading it correctly, my own PA routine uses plate solving when I use Sharpcap Pro to PA 

😂😂

[dannybgoode]

1 hour ago, Robny said:

Wasn't reading it correctly, my own PA routine uses plate solving when I use Sharpcap Pro to PA 

😂😂

Spot on. That’s exactly what it does. Plate solving just works out where your scope is pointing