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Old 05-02-2017, 07:29 AM
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alpal
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Simple idea to improve imaging.

Simple idea to improve imaging.


I use EasyCap software with my QHY9M.
How about a modification to the software that will close the shutter if the PHD guide graph
exceeds a certain limit e.g. more than 1 division -
but will allow for that in the image time so that the subframes are still the same length?
It would be the end of egg shaped stars ruining a picture.
( obviously the shutter would open again as soon as the guide graph was below 1 division )


It is possible to do manually if you had a cable wired into the camera to close the shutter manually
but still keep the KAF8300 running..

cheers
Allan
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Old 05-02-2017, 08:22 AM
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billdan (Bill)
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Hi Allan,

I use ezcap with my QHY12 and as you know its very basic. My version does not support dithering which would be nice.
Also a pause button ( in between frames) when doing a capture run would be good, so I can check focus every hour. Otherwise I have to stop the capture run, check focus and then start a new capture sequence.

I believe the version of ezcap supplied with the latest QHY cameras has more features but not for the original cameras.

Bill
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Old 05-02-2017, 08:29 AM
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Quote:
Originally Posted by billdan View Post
Hi Allan,

I use ezcap with my QHY12 and as you know its very basic. My version does not support dithering which would be nice.
Also a pause button ( in between frames) when doing a capture run would be good, so I can check focus every hour. Otherwise I have to stop the capture run, check focus and then start a new capture sequence.

I believe the version of ezcap supplied with the latest QHY cameras has more features but not for the original cameras.

Bill

I can dither with PHD2 guiding but it's not automatic.
I have to dither & then watch the guide graph till it stabilises
then click EasyCap to start capturing again.
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Old 05-02-2017, 08:51 AM
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jwoody (Jeremy)
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Astro Photography Tool (Free version http://ideiki.com/astro/Default.aspx will integrate with PHD and auto dither, might be worth a look
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Old 05-02-2017, 12:57 PM
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Quote:
Originally Posted by jwoody View Post
Astro Photography Tool (Free version http://ideiki.com/astro/Default.aspx will integrate with PHD and auto dither, might be worth a look

Dunno - but they look like the sort of people who could manage the job.
It depends if the QHY9m allows for a software controlled camera shutter close & open without download of frame.

cheers
Allan
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Old 05-02-2017, 03:13 PM
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Shiraz (Ray)
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sounds like a good idea Allan - maybe you could also consider removing wind-induced mount wobbles if you drive the shutter based on how much signal you get from an accelerometer on the scope?

downsides might be that the shutter would always be reacting after the event - wouldn't be fast enough to do the job with quick disturbances. The shutter will wear out quickly, but that may not be a deal breaker. Maybe a separate liquid crystal shutter would be an idea - faster and longer lasting. Also, the longer sub length will add to the dark current, but again, probably no big deal.

let us know how you get on .

Last edited by Shiraz; 05-02-2017 at 05:59 PM.
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Old 05-02-2017, 10:36 PM
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Quote:
Originally Posted by Shiraz View Post
sounds like a good idea Allan - maybe you could also consider removing wind-induced mount wobbles if you drive the shutter based on how much signal you get from an accelerometer on the scope?

downsides might be that the shutter would always be reacting after the event - wouldn't be fast enough to do the job with quick disturbances. The shutter will wear out quickly, but that may not be a deal breaker. Maybe a separate liquid crystal shutter would be an idea - faster and longer lasting. Also, the longer sub length will add to the dark current, but again, probably no big deal.

let us know how you get on .

Hi Ray,
It's just an idea right now.
I wish I had the circuit diagram of the QHY9m.
The dark frames are no problem as any dark frame of similar length will detect hot pixels &
the dark noise is way below any sky noise.

cheers
Allan
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Old 06-02-2017, 07:27 PM
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Hi Allan,
Using the shutter to select good/bad times of seeing/wind was discussed as far as back as 2006 and implemented by Steve Bell around 2009.
IIRC it doesn't really work very well (minor improvement sometimes) as compared to lucky imaging where the improvement can be substantial if the exposure is short enough (milliseconds). Of course the read noise at such short exposures is a real bummer and a 'zero cam' is required

If you have access to the SBIG yahoo groups archive here are some references:

https://groups.yahoo.com/neo/groups/...essages/141713

https://groups.yahoo.com/neo/groups/...essages/208793

https://groups.yahoo.com/neo/groups/...essages/207977

If you can't access them I could possibly copy/paste the text...if that's allowed?

Regards,
EB
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Old 06-02-2017, 08:49 PM
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Quote:
Originally Posted by ericwbenson View Post
Hi Allan,
Using the shutter to select good/bad times of seeing/wind was discussed as far as back as 2006 and implemented by Steve Bell around 2009.
IIRC it doesn't really work very well (minor improvement sometimes) as compared to lucky imaging where the improvement can be substantial if the exposure is short enough (milliseconds). Of course the read noise at such short exposures is a real bummer and a 'zero cam' is required

If you have access to the SBIG yahoo groups archive here are some references:

https://groups.yahoo.com/neo/groups/...essages/141713

https://groups.yahoo.com/neo/groups/...essages/208793

https://groups.yahoo.com/neo/groups/...essages/207977

If you can't access them I could possibly copy/paste the text...if that's allowed?

Regards,
EB

Hi Eric,
Thanks - I can't view those links.
I know that lucky imaging is better but of course it only works on bright targets.

I just noticed on my last imaging session that although my PHD dx/dy
guide graph was saying 0.19 rms to 0.25 rms there was an occasional
blip where the guide graph went above one division.
I thought - wouldn't it be nice to watch the line increasing towards
one division & close the shutter for 1 to 3 seconds to not collect that bad data.
Keep the shutter closed until the guide graph had stabilised.

It seems so simple that it must work.

It's possible that I could wire in something - a cable with
a button on the end to close the shutter on my QHY9 & do it manually
as there doesn't seem to be any software that can perform this simple process.

cheers
Allan
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Old 12-02-2017, 09:57 AM
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Quote:
Originally Posted by ericwbenson View Post
Hi Allan,
Using the shutter to select good/bad times of seeing/wind was discussed as far as back as 2006 and implemented by Steve Bell around 2009.
IIRC it doesn't really work very well (minor improvement sometimes) as compared to lucky imaging where the improvement can be substantial if the exposure is short enough (milliseconds). Of course the read noise at such short exposures is a real bummer and a 'zero cam' is required

If you have access to the SBIG yahoo groups archive here are some references:

https://groups.yahoo.com/neo/groups/...essages/141713

https://groups.yahoo.com/neo/groups/...essages/208793

https://groups.yahoo.com/neo/groups/...essages/207977

If you can't access them I could possibly copy/paste the text...if that's allowed?

Regards,
EB


Hi Eric,
I joined the Yahoo group & have read all those links.
They seem to think it would work but want a software solution -
which is fair enough.
It would be much easier than having to wire up a cable up & do it manually.

I have also contacted QHY for a circuit but have received only a component overlay & a small photo.
If I do this mod I want to open the camera only once & install it.
You can't just wire in your own circuit without knowing what's there
other wise you could back feed voltage into the camera shutter driver
IC - Integrated Circuit - & risk wrecking it.

I think I need to ask them to make a software upgrade as their
software does control the shutter.

Other comments on Yahoo -
" the idea is a poor man's AO7. "
That's true but also an AO7 can chase the seeing giving worse results
& you need a bright star to run an AO7 at 10hz - a lot of mucking around
& not always possible.

cheers
Allan
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  #11  
Old 15-02-2017, 11:10 PM
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Latest news - shutter control in the middle of taking a picture.

QHY kindly sent me the details of the circuit as per attached pics for the shutter circuit of the QHY9m.
The chip is an L298P - easily found on google -
it's a dual full bridge driver.

It's NOT just a matter of connecting 2 wires up to do this modification.
I'll have to think about it.
I can't just drive pins 7,9,13,15 as I would be back feeding voltage into
their sources - another chip - not shown.


Anyway - I have a starting point to work with.
Also - QHY may put this idea into their software on the next revision
which would be fantastic & a lot easier than trying to wire in hardware.

cheers
Allan
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