Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Dither with one and autoguide with the other?

Astrophotography
  • Please log in to reply
9 replies to this topic

#1 jasongabler

jasongabler

    Lift Off

  • -----
  • topic starter
  • Posts: 5
  • Joined: 12 Oct 2020

Posted 16 October 2021 - 12:49 AM

I have an SAP2i and I just got a 2.5mm-to-Olympus (OM-D EM-5 Mark I) shutter cable. I use an ZWO ASI 120mm Mini guide camera with PHD2, connected to the SAP.  I excitedly put it all together, got the SAP to control the shutter, and fired up the dithering only to realize that the SAP's dithering is confusing the PHD2 guiding.  It seems that the movements of the dithering processes causes star loss for PHD2.  Two questions:

 

1) Is this a correct assessment?

 

2) I cannot imagine how, but is there a way to compensate for this?  I would love to use PHD2 to control my camera, but PHD2 doesn't speak Olympus :(

 

Thanks.



#2 alfogator

alfogator

    Sputnik

  • -----
  • Posts: 36
  • Joined: 06 Sep 2015
  • Loc: Pistoia, Italy

Posted 16 October 2021 - 03:34 AM

You might try an image capture software, like NINA: it will control PHD2 and synchronize guiding and dithering.



#3 whwang

whwang

    Soyuz

  • *****
  • Posts: 3,807
  • Joined: 20 Mar 2013

Posted 16 October 2021 - 04:04 AM

Hi,

 

I don't know what SAP2i is.  Based on your description, it seems to be able to trigger the shutter of your camera.  If it can do that, you can try not to use it to dither.  Instead, if you go to PHD2's website, you can find a small APP called dither timer.  It allows you to dither at a fixed time interval.  You can try to sync (manually) the dither timer with your shutter control APP, in such a way that the shutter APP triggers exposure every X minutes and the dither timer also triggers dithering every X minutes.  This is what I do for my camera that doesn't have astro APP support for auto dithering.

 

Hope this helps.

 

Cheers,

Wei-Hao


Edited by whwang, 16 October 2021 - 11:09 PM.


#4 DJL

DJL

    Viking 1

  • -----
  • Posts: 979
  • Joined: 15 Aug 2020

Posted 16 October 2021 - 08:02 AM

Hi,

 

I don't know what SAP2i is.  Based on your description, it seems to be able to trigger the shutter of your camera.  If it can do that, you can try not to use it to dither.  Instead, if you go to PHD2's website, you can find a small APP called dither timer.  It allows you to dither at a fixed time interval.  You can try to sync (manually) the dither timer with your shutter control APP, in such a way that the shutter APP triggers exposure every X minutes and the dither timer also triggers exposure every X minutes.  This is what I do for my camera that doesn't have astro APP support for auto dithering.

 

Hope this helps.

 

Cheers,

Wei-Hao

Confused me for a minute as well. Star Adventurer Pro 2i presumably.



#5 ktran

ktran

    Explorer 1

  • *****
  • Posts: 59
  • Joined: 01 Aug 2018

Posted 21 October 2021 - 12:24 PM

I have an SAP2i and I just got a 2.5mm-to-Olympus (OM-D EM-5 Mark I) shutter cable. I use an ZWO ASI 120mm Mini guide camera with PHD2, connected to the SAP.  I excitedly put it all together, got the SAP to control the shutter, and fired up the dithering only to realize that the SAP's dithering is confusing the PHD2 guiding.  It seems that the movements of the dithering processes causes star loss for PHD2.  Two questions:

 

1) Is this a correct assessment?

 

2) I cannot imagine how, but is there a way to compensate for this?  I would love to use PHD2 to control my camera, but PHD2 doesn't speak Olympus frown.gif

 

Thanks.

This is correct. The Star Adventurer 2i's dithering is for unguided exposures only. It's also an RA-only dither. I also shoot Olympus, and the RA dither is very handy when shooting shorter focal length telephotos unguided.

 

As others have said, you can use another piece of software to control the image acquisition.

 

I do things in a bit more primitive way: I check on my exposures every 5-10 frames or so, and so I just use that opportunity to stop guiding, and nudge the RA and DEC manually for my own sort of dithering.


Edited by ktran, 21 October 2021 - 12:25 PM.

  • jasongabler likes this

#6 chanrobi

chanrobi

    Viking 1

  • -----
  • Posts: 991
  • Joined: 02 Sep 2019

Posted 21 October 2021 - 04:36 PM

The Star Adventurer 2i's dithering is for unguided exposures only.

This makes 0 sense from a logical point of view...??



#7 ktran

ktran

    Explorer 1

  • *****
  • Posts: 59
  • Joined: 01 Aug 2018

Posted 21 October 2021 - 05:04 PM

This makes 0 sense from a logical point of view...??

It's a feature introduced in the Star Adventurer Mini and the new 2i model. Both of these can be controlled via a wifi app. You set your exposure time and dithering range in arcmins and the Star Adventurer will fire a DSLR or mirrorless camera shutter for you, and dither a pseudo-random distance between exposures.



#8 whwang

whwang

    Soyuz

  • *****
  • Posts: 3,807
  • Joined: 20 Mar 2013

Posted 21 October 2021 - 08:51 PM

This makes 0 sense from a logical point of view...??

 

This makes huge sense.  I hope my small light-weight mount can do that, so I won't need to guide to dither while shooting wide-angle.


  • ktran and galacticinsomnia like this

#9 jasongabler

jasongabler

    Lift Off

  • -----
  • topic starter
  • Posts: 5
  • Joined: 12 Oct 2020

Posted 23 October 2021 - 07:04 PM

Hi,

 

I don't know what SAP2i is.  Based on your description, it seems to be able to trigger the shutter of your camera.  If it can do that, you can try not to use it to dither.  Instead, if you go to PHD2's website, you can find a small APP called dither timer.  It allows you to dither at a fixed time interval.  You can try to sync (manually) the dither timer with your shutter control APP, in such a way that the shutter APP triggers exposure every X minutes and the dither timer also triggers dithering every X minutes.  This is what I do for my camera that doesn't have astro APP support for auto dithering.

 

Hope this helps.

 

Cheers,

Wei-Hao

Yes, as everyone's probably figured out by now, SAP2i is the Star Adventurer Pro 2i. 

 

I really appreciated @ktran 's response.   I mostly shoot DSOs with the 40-150mm PRO at 150mm, and sometimes 300mm with the 2x teleconverter. (That's 300mm and 600mm, respectively, for you full-frame people.). So, I almost always need guiding.

 

It's funny. I can connect the computer (with PHD2) to the SAP with the autoguiding camera as an intermediary. And I can connect the SAP to the imaging camera to control the shutter. But PHD2 cannot control the camera through the autoguiding camera+SAP.  If that were possible it really would solve this problem.  After all, in terms of the electronics, the SAP's ability to control the shutter is nothing fancy. Why do you think this hasn't been implemented? Does the communication standard between the computer+PHD2 and the autoguiding camera not support that sort of command?  I mean, it can tell the mount how to correct RA axis rotation, how much more difficult could it be to fire the shutter?



#10 ktran

ktran

    Explorer 1

  • *****
  • Posts: 59
  • Joined: 01 Aug 2018

Posted 23 October 2021 - 09:18 PM

Yes, as everyone's probably figured out by now, SAP2i is the Star Adventurer Pro 2i. 

 

I really appreciated @ktran 's response.   I mostly shoot DSOs with the 40-150mm PRO at 150mm, and sometimes 300mm with the 2x teleconverter. (That's 300mm and 600mm, respectively, for you full-frame people.). So, I almost always need guiding.

 

It's funny. I can connect the computer (with PHD2) to the SAP with the autoguiding camera as an intermediary. And I can connect the SAP to the imaging camera to control the shutter. But PHD2 cannot control the camera through the autoguiding camera+SAP.  If that were possible it really would solve this problem.  After all, in terms of the electronics, the SAP's ability to control the shutter is nothing fancy. Why do you think this hasn't been implemented? Does the communication standard between the computer+PHD2 and the autoguiding camera not support that sort of command?  I mean, it can tell the mount how to correct RA axis rotation, how much more difficult could it be to fire the shutter?

Unfortunately, the Star Adventurer's shutter control functionality is very limited, and very explicitly in the manual it states that autoguiding and the unguided dither don't mix. I can't comment on using PHD2 or NINA. I use the SA with a standalone autoguider (which is not the way things are trending these days), and manually dither after every half hour or so (10 frames at 3 mins each).

So really, I think the path you're following isn't going to lead anywhere fruitful. The main target audience of the Star Adventurer family products is really the wide angle milky way landscape crowd. Those of us who push the limits a bit are more or less on our own :)

 

A small correction though: there's no such thing as the "Star Adventurer Pro" or SAP. It's the Star Adventurer or Star Adventurer 2i. The "Pro" refers to the "Pro pack" of accessories, which includes the wedge, the DEC bracket and counterweight. It's a bit nit-picky, but it's a common mistake ppl make.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: Astrophotography



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics