Feature Request - Non Guiding Dithering for Astrophotography

[Jim Waters]

It would be nice if PHD Guide 2 could work with Backyard EOS and be able to ‘dither’ a mount but not actually be guiding the mount.  This would be helpful when imaging at wide F.L.’s (~<300mm) where P.E. is very small in relation to the F.L..  This would simply the setup.  I use dithering to control noise in my images.  I have tried to manually move my mount using the Hand Controlled keeping track of my +- RA and +- DEC movements between images.  It does help to reduce noise.

Surprisingly my mount has little R.A. Periodic Error.  Its major issue is DEC backlash and some cogging but this can be managed by careful polar alignment and balancing.  

My Equipment

• Hyper-Tuned CGEM
  
• QHY PoleMaster
  
• 60mm f/4 Guide Scope w/ Orion SSAG
  
• Canon 6D w/ ‘L’ Lens
  
• Open PHD Guide 2.6.3
  
• Backyard EOS 3.1.9
  

Jim

Phoenix, AZ

[Bryan]

Andy, Bruce

Would this work?

Turn Dec guiding off

Make Min move in RA a big number...1000 pixels.

OR possibly

Turn both RA and Dec algorithms to None.  Will this also disable dithering?

Bryan

[bw_msgboard]

I don’t really understand the original request.  Dithering in PHD2 is accomplished by applying normal guiding, there isn’t any small-scale slewing going on.  So we dither by setting a new lock-point then let the guide algorithms move the star to the new lock position.  If the OP just wants to “jog” the mount by some small amount, there are probably better tools for doing that – e.g. a simple ASCOM client script that would slew the mount by the desired amount.  But as I said, I don’t really understand the request.

 

Bruce

 

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[peter wolsley]

All,

As I understand Jim's question...he would like PHD2 to send dither guide pulses to his CGEM via ASCOM without the need for a guider camera.  I am making this assumption because I don't see anything in his equipment list that could function as a guider cam.  As I understand PHD2 dithering...there needs to exist a guider cam because a dither event is simply generating a small lock position offset.  The resulting error causes PHD2 to generate guide pulses which move the mount so that the camera is repositioned at the new lock position. Jim's current technique of simply using the handcontroller buttons (at speed 1 = 50% sidereal) would do the trick quite well but he has to be in attendance to do this.  For Jim's request...I would expect that PHD2 would need to generate a single random guide pulse in response to a dither.

Andy and Bruce will have the last word.

Peter

[Bryan]

See clipped section from Jim's OP.

Bryan

[Andy Galasso]

On Tue, Mar 14, 2017 at 3:58 PM, Jim Waters <jim.t....@gmail.com> wrote:

It would be nice if PHD Guide 2 could work with Backyard EOS and be able to ‘dither’ a mount but not actually be guiding the mount.

I think this would be best implemented in BYEOS since PHD2 can only dither when it is guiding (by moving the lock position as Bruce said.)  Since you are not guiding, it sounds like you are looking for a small slew followed by a wait for the mount to settle.  BYEOS could do this.  I know of at least one other imaging app that does dithering without guiding in this way (SGP).

Andy

[Jim Waters]

I exchanged emails with BYE support about this request and they said to go through ASCOM and that they aren’t really interested in doing this.  I don’t use ASCOM to connect to the CGEM.  I like to keep things simple.  I just want the ability to move the mount in +-RA and +-DEC (or dither) between subs to help control noise for wide-field imaging - lets say under 300mm.  I have tried this manually with the CGEM Hand Controller and the Canon EOS Utility and it does help control the noise.

 

I have relied on full PHD2 / BYE guiding w/ dithering but if I can eliminate the guide scope / auto-guider I can reduce weight, simplify the setup and use this setup with my Astrotrac. 

IMHO - With my subs usually under 5 minutes, doing wide-field imaging and low P.E. full auto-guiding is optional.

[Jim Waters]

Why can’t you move the mount following a ‘scripted’ fixed or maybe random amount and keep track of where you were and where you have to go?  To make things simpler you can just do this for R.A. and not touch DEC although including DEC would be great.  I am not sure what the user base would be for this but astrophotographers that use Astrotrac's, Star Adventurer's ...etc would benefit.

Jim

On Tuesday, March 14, 2017 at 3:08:42 PM UTC-7, Andy Galasso wrote:

[Andy Galasso]

One possibility would be to add a function to the PHD2 server API to allow scripts or apps (like BYEOS) to initiate a guide pulse. If we were to do that, you would need to be able to call an external program or script from BYEOS to invoke the API function at the appropriate time. Does BYEOS support running an external program or script before each sub?

Andy

[bw_msgboard]

This doesn’t make any sense to me.  I’m looking at your equipment list and you’re all set up to guide – guide scope, guide camera, PHD2, the whole package.  So why don’t you just guide?  Is it because of BYEOS?  Regardless of how this is done, you have to get coordination between the imaging app and whatever software is doing the guiding and dithering.  Can BYEOS do that?  If it can’t, then I don’t think you’re going to get anywhere.  At the very least, BYEOS needs to be capable of finishing an exposure, running a script or batch file, waiting for the script to complete, then starting the next exposure.  If it can already do that, then you can let PHD2 guide and dither as its intended to do.  Alternatively, you could use a time-driven dither with PHD2 and somehow define the BYEOS sequence so that it isn’t exposing when the dither happens.  In any case, I really can’t see any value in trying to implement a blind guide pulse feature in PHD2.

 

Bruce

 

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From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of Jim Waters

Sent: Tuesday, March 14, 2017 4:54 PM
To: Open PHD Guiding

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[steve]

El 15/03/2017 a las 00:34, Jim Waters escribió:
> I just want the ability to move the mount in +-RA and +-DEC (or
> dither) between subs

Hi. I understand you want to mount the camera on the mount. No guiding.
Just the mount tracking. If so, APT will do it; it dithers according to
the focal length of the lens and the sensor you use. No guiding needed;
you set the dither you want in pixels. Just take PHD2 out of the mix.
Maybe BYE doesn't have that yet? HTH and clear skies, Steve.

[Jim Waters]

Because I really don’t need to if the SW supports non-guided dithering.  As I mentioned in the other emails it simplifies the setup and reduces weight.  I can just attach a DSLR with a wide-field lens to the mount and be done with it as far as setup is concerned.  It becomes more attractive with Star Tracking mounts such as the Astrotrac and some others.

 

Is there a document that describes in detail the interface and handshaking protocol between PHD Guide 2 and BYE?  I would like to walk through it. I have recently retired after 30+ years as an Sr. Enterprise Architect / Computer Systems Engineer and would like to developing an app to do this.  If I later find out that it’s impossible to interface this app with BYE I will just code the app to fire off the Canon camera and capture the subs to the camera SD card.

 

Are the following doc’s readily available

• PHD Guide 2 to BYE Interface / Handshaking Protocol Doc.
  
• Canon SDK Doc’s.  I suspect I can get the SDK for Canon.

As for as value of this feature you may be right.  The user base may be small but I think there will be users that will use it.

Jim

[Brian Valente]

I could see that being handy for folks looking for a much simplified field setup, I’m just not sure PHD2 (as a guiding app) is the place for it.

 

The guys over at hutech have a standalone guider, and they were making noises about having an open platform, might be worth a look to see if it’s closer?

 

https://digiborg.wordpress.com/2016/09/26/new-palmtop-controller/

 

 

Thanks

 

Brian

 

 

Brian Valente

Brianvalentephotography.com

[Jim Waters]

Many thanks :).

[Jim Waters]

Thanks for the heads-up.  Just walked through your website - really nice work!

Jim

[Andy Galasso]

On Wed, Mar 15, 2017 at 3:02 AM, Jim Waters <jim.t....@gmail.com> wrote:

 

Are the following doc’s readily available

• PHD Guide 2 to BYE Interface / Handshaking Protocol Doc.
  

Jim,

PHD2 supports two communication interfaces, an older PHD1-compatible interface and the newer PHD2 interface. We can add a new function to the PHD2 interface to move the mount via a guide pulse.  You could then invoke that method from a script or application to move the mount without requiring PHD2 to be guiding, You would be telling phd2 "guide fox X miliiseconds in this direction (N/S/E/W)". PHD2 would only need to be connected to the mount and would not need to be guiding and would not require a camera connection unless your mount selection is "On-camera".

Alternatively, you could use ASCOM to do this already without any changes to PHD2.

Andy

[Jim Waters]

Andy - Let me check out ASCOM first. Thanks for the input and URL's.  Jim

[mar pal]

Not sure of this helps or not but check out this post on cloudy nights regarding dithering without guiding:

https://www.cloudynights.com/topic/543976-how-to-dither-using-backyard-eos/