the ultra low end of video astronomy
Posted 19 March 2013 - 09:40 AM
Viewing the video stream often does look better to me too but many video hosting sites seem to impart additional compression which doesn't help the images.
It's very clear that any more than slight tweaks can really make a substantial improvement in an image and this would now be something that isn't representative of the "live" image thus the comments about not posting images that have been extensively processed. ATL's great images show this progression very clearly as do many of Nytcam's images.
I think the best course of action is to post as many details about an image as possible. That way folks can better understand, interpret, and compare the images.
Posted 19 March 2013 - 09:46 AM
Posted 24 March 2013 - 04:25 PM
Are you creating these images using prime focus, or are you using an afocal setup?
Posted 24 March 2013 - 04:54 PM
Posted 24 March 2013 - 05:47 PM
Posted 24 March 2013 - 08:33 PM
Posted 24 March 2013 - 08:47 PM
To first order, one can say a detector is equivalent to an eyepiece whose focal length equals the detector's width. And so a 6mm wide CCD is about equal to a 6mm eyepiece. But this is open to debate, for one can choose a longer f.l. eyepiece having a small apparent field or one of a shorter f.l. but larger apparent field and have the same field of view.
Far better to simply state the field width, in degrees or arcminutes. This is unambiguous.
Posted 24 March 2013 - 09:13 PM
Posted 24 March 2013 - 10:21 PM
Example, a 6mm wide chip with a 1,200mm focal length has a field width of:
ARCTAN ( 6 / 1200 ) = 0.286 degrees = 17.19 arcminutes.
Note that for such small angles it's valid to simplify like this. For larger angles, exceeding approximately 10 degrees, the correct formula is:
(ARCTAN ((CCD width / 2) / focal length)) * 2
In other words, you first calculate the semi-angle due to the tangent function, the multiply this by 2 to get the full angle.
Posted 31 March 2013 - 01:34 AM
Posted 31 March 2013 - 11:23 AM
Posted 31 March 2013 - 11:49 AM
Posted 31 March 2013 - 05:55 PM
Posted 31 March 2013 - 07:58 PM
Posted 31 March 2013 - 09:11 PM
Posted 01 April 2013 - 12:57 AM
Posted 01 April 2013 - 09:58 AM
Since you obviously have good dark skies you might try pushing the f ratio down a bit again. On big objects like the flame you could try your .5x focal reducer, perhaps with some relaxed spacing (little closer to the sensor if possible). That way you won't need as much in focus travel (which will likely be the biggest obstacle to using the focal reducer with your new scope). Yeah there will be more background noise but a little tweaking of brightness and contrast on the display side will likely help.
The horizontal banding seen is likely electrical noise. What are you using for a power source for your Matrix video camera? What are you using to display/capture the images?
Posted 01 April 2013 - 04:32 PM
I do have dark skies for the most part. The city of Agua Prieta Mexico is about 6 miles away and it makes some light on the southern sky...but not too bad. I think I would be considered to be in a blue zone not far from green according to LP maps.
Posted 01 April 2013 - 05:31 PM
I try and swap stuff wherever practical to see if that changes anything. Sometimes just re routing the power and video cables (keeping them more separate) can help.
Do you have a 12v battery or another AC 12v power supply that you could try with the camera?
A different video cable?
Do you have a cheap video monitor to try in place of the netbook?
Maybe a different USB frame grabber?
You can sometimes try flipping a two prong plug in an AC outlet around (if it doesn't have a wide and narrow prong which "keys" the plug to the socket) to change the grounding.
While quite rare a tougher cause to figure out is when there is something else running in your house (or your neighbour's) that is causing the electrical noise. Things like old fans and air conditioners (and compressors in fridges and freezers) are notoriously electrically noisy.
Posted 01 April 2013 - 06:34 PM