Astro features for digicamControl (PhD guiding)

Use this forum to request new features or suggest modifications to existing features
gwondaleya
Posts: 18
Joined: Mon May 13, 2013 10:12 pm

Yep, cheap adapters suffers

Post by gwondaleya » Thu May 30, 2013 9:53 pm

Yep, cheap adapters suffers from the "diseases" you mentionned. The FTDi ones don't, since you can assign a COM port number, through the use of their soft !(at least COM port doesn't wander in all the tests i have done so far). Cheap microcontroller with built in USB may be a solution, but you need to write a firmware and a PCsoftware for that !

Yep, cheap adapters suffers

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gwondaleya
Posts: 18
Joined: Mon May 13, 2013 10:12 pm

Will try to test that "in the

Post by gwondaleya » Thu May 30, 2013 9:59 pm

Will try to test that "in the field"..when i will have clear skies....(which is, well, seldom the case this year...).
Will see too if we can do something with simulated mount...
Joël

gwondaleya
Posts: 18
Joined: Mon May 13, 2013 10:12 pm

Hi Istvan,

Post by gwondaleya » Sat Jun 01, 2013 1:14 pm

Hi Istvan,

i have tested with simulator and looks like it works correctly :-)
Perhaps a comment about the wait time: actually it take seconds to stabilizize the mount mechanics, not ms.
also the message MSG_REQDIST is to request to phd the error (in pixels) between guiding star and requested position.
When a dithering command is sent, the mount move of a given distance, then the requested position is updated. but it take some time for the mount to move and stabilize to the new position. the MSG_REQDIST request this error in pixels.
"advanced" Tools which are using dithering actually do as following rather than using waiting time
they send a dithering order (MOVE) then they poll the error (MSG_REQDIST) several times (during a given amount of time) to evaluate if the error is lower than a given threshold. when the error is lower than the threshold or the amount of time is finished, they start a new capture.Also the period of polling should not be faster than the guiding star acquisition (called guiding time), this parameter is also to be taken into account.
here is a suggestion (the current way of doing is already working nicely ;-)
the parameters of the command can be:
Move (value between 1 and 5)
timeout (in seconds) which is waiting time or time of polling
guide time which is the time between 2 poll (2 MSG reqDIST)
threshold (in pixels, can be a fraction of pixels) the value of error you accept for the mount to stabilize (if value is 0, you decide to do only a wait time, no poll)
Also the error should be several times lower than the threshold (say 5 to 10 times) otherwise it means that the mount oscillate.

Nevertheless, that's already nice as it is, and it works perfectly (at least with my D90 and my homemade rs232 remote shutter!)
Thanks

Joël

gwondaleya
Posts: 18
Joined: Mon May 13, 2013 10:12 pm

A precision:

Post by gwondaleya » Sat Jun 01, 2013 1:18 pm

A precision:
when i say several times i mean that the error should be lower than the threshold during 5 or 10 polls (and not a division factor :-) )

Joël

Duka Istvan
Posts: 867
Joined: Tue Mar 26, 2013 9:52 pm

A new version with separated

Post by Duka Istvan » Sat Jun 01, 2013 11:58 pm

A new version with separated live view for astro stuff https://dl.dropboxusercontent.com/u/409 ... .0.558.exe not big deal yet but a start to have to talk about.

Kuulapaa
Posts: 5
Joined: Thu Jun 06, 2013 8:10 pm

Very impressive!

Post by Kuulapaa » Thu Jun 06, 2013 8:26 pm

Thanks for the awesome software and especially for this astrophotography feature.

I tested it with D800 and exposure control works perfectly with USB cable. I also tried scripting with PHD (although without mount and active tracking - it's very light in here north so no stars visible until summer goes by;)

DCC seems to send dithering controls well to PHD. For some reason I wasn't able to save script. One feature could be option to move script elements.

I need to find out the actual response to move 1-5 commands. At the moment I'm not familiar what they actually do. Can someone explain them and PHD response to them for me?

Anyway I'm really grateful for your hard work with this!!!

gwondaleya
Posts: 18
Joined: Mon May 13, 2013 10:12 pm

Hi Istvan,

Post by gwondaleya » Sun Jun 09, 2013 10:31 pm

Hi Istvan,
had the opportunity to test it this week end in south of france. Works nicely, and this separated live view is a nice idea, very useful for precise focusing with, for example fwhm.exe or even bafocus, two tools wich measure the "spreading" of a star on the pixels (the less the spreading, the best the focus).
I am happy with the soft! keep the road Istvan!!

Joël

gwondaleya
Posts: 18
Joined: Mon May 13, 2013 10:12 pm

Hi Kuulapaa,

Post by gwondaleya » Sun Jun 09, 2013 10:42 pm

Hi Kuulapaa,
basically the commands to PHD refers to a technique called dithering. The purpose of this is to make move the mount by an amount of few pixels each capture so that some noise called banding (which is related to the way the pixels are organised on the sensor itself). It also help in removing more efficiently hot spots, dark pixels, some part of thermal noise by making these pixels "moving" randomly (relative to the deep sky object you are imaging). The number of the move command is basically the maximum amplitude of the random displacement asked.
Whenyou have done several captures (say 25 pictures) and you stack them to get your final image, since all the "constant noise " moved relatively to the object you photographied, it is numerically diluted and become less important.
(this is quite hard to me to explain that in text and in english, since that's easier doing it in speaking and showing and in native langage)!

Hope's this help. Otherwise, looking in the numerous astro forum on internet by searching for "dithering", you should find a better explanation than mine!!

Kuulapaa
Posts: 5
Joined: Thu Jun 06, 2013 8:10 pm

I command you to move (1-5)

Post by Kuulapaa » Tue Jun 11, 2013 9:45 pm

Thanks, that "movement magnitude" is what I was looking for. Very good explanation on dithering :)

Software itself cannot know the focal length so how does those move-commands reflect in real life - I mean just overall with decent focal lengths (just as a subjective feeling)?

D600
Posts: 5
Joined: Fri Jun 14, 2013 8:10 pm

Astrofeatures

Post by D600 » Fri Jun 14, 2013 8:32 pm

Hello, my first post to this forum. I am a amateur astronomer and a complete remote control kit should include this.

1. Be able to adjust iso, shutterspeed and allow the camera to take more then 30 sec exposures.
2. Control the shutter in a blub mode with an external RS232 port.
3. Autofocus with a V-curve, like FocusMax does. It is a necessary function to have.
4. Measure the size of the star with Full Width Half Maximum value, FWHM.
5. Be able to talk to a external focuser thorugh ascom 6.
6. Be able to take light frames with dark frame substraction for finding stars.
7. A very nice feature is to do a pinpoint astronometry search if the telescope is not pointing exact on the spot that it should point on and do a resolve thorugh a planetary program. Like Cartes du Ciel or similar (not Stellarium).

PHD Guiding is not a relevant feature to have to a DSLR camera since it could not autoguide itself. If the autofocus chip could deliver a picture with stars at the same time the main chip do the exposure. That could be a very nice off-axis guider indeed! I have never heard that it could work..

Look at MaximDL 5 how these feature works.

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