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

Sirius B Feb 17 2017

  • Please log in to reply
18 replies to this topic

#1 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 17 February 2017 - 11:08 AM

Here are a couple of Sirius B captures with a C14 and ZWO ASI 224mc camera and L filter. First one was 0333 UT Feb 17 2017 and the second was 0340 UT Feb 17 2017. I had to work the gain, exposure and gamma sliders in Firecature to detect the pup. - Tom- New Mexico

Attached Thumbnails

  • SiriusB_Feb172017_0333ut_Ashcraft1.jpg
  • SiriusB_Feb172017_0340ut_Ashcraftvh.jpg

  • Illinois, JerryOrr, Abhat and 4 others like this

#2 einarin

einarin

    Ranger 4

  • -----
  • Posts: 360
  • Joined: 23 Dec 2016

Posted 17 February 2017 - 11:13 AM

Good catch. 

Look like single frames but are they ?

What exposure ?



#3 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 17 February 2017 - 12:44 PM

In a private message I have been challenged for measurements to prove that this is actually Sirius B. :) Well, I am just a casual observer and don't have measurement skills. I don't know how to do that. I did post my .avi file at vimeo which, if you look close, you can hopefully see Sirius B bobbing in and out of view. There is a lot of video quality loss in their compression from the .avi file to their own format. Let me know if you can't see it please.

https://vimeo.com/204567898

 

The images provided in the first message were stacked in Autostakkert!

 

Here is my Firecapture text file for general settings. This was barely a quantitative scientific observation, rather just me enjoying the stars and pointing my telescope at Sirius, hoping to capture "B".

FireCapture v2.4  Settings
------------------------------------
Camera=ZWO ASI224MC
Filename=2017-02-17-0333_4-610-4.avi
Date=170217
Start=033328.876
Mid=033349.135
End=033409.394
Start(UT)=033328.876
Mid(UT)=033349.135
End(UT)=033409.394
Duration=40.518s
Date_format=ddMMyy
Time_format=HHmmss
LT=UT -7h
Frames captured=3706
File type=AVI
Extended AVI mode=true
Compressed AVI=false
FPS (avg.)=91
Shutter=9.779ms
Gain=383
SoftwareGain=10 (off)
HardwareBin=off
WRed=99
Gamma=83
WBlue=61
AutoExposure=off
USBTraffic=45
HighSpeed=off


  • Dan Williams and Aleksandr Naumov like this

#4 Aleksandr Naumov

Aleksandr Naumov

    Explorer 1

  • *****
  • Posts: 70
  • Joined: 23 Jun 2014

Posted 17 February 2017 - 01:55 PM

There is no rocket science in measuring the distance in pixels between Sirius and its probable companion.

 

I downloaded 2nd image, this is 640x480 JPEG.

The camera have resolution of 1304x976 and have 4:3 aspect ratio, the same as 640x480.

So I assume original image was proportionally scaled before uploading here. Scale factor is 0.491.

 

Next, I opened this image in MS Paint and determined pixel coordinates of Sirius and its companion.

Sirius center position: x=319, y=241.

Companion center position: x=371, y=219.

 

Next, using Pythagoras theorem, I calculate distance between these:

dx = 371 - 319 = 52, dy = 241 - 219 = 22.

distance = square root(dx * dx + dy * dy) = 56.

 

Scaling back to original frame dimensions, I estimate the distance was more than 100 pixels.

The camera have 3.75um pixel, so linear distance is about 0.375mm.

 

Which is angular distance?

Using following formula,

 

angular_distance = 206265 * linear_distance / focal_length,

 

I calculated 0.375mm corresponds to 19.78".

 

Another calculation of angular distance:

using https://starizona.co...calc_pixel.aspx,

I found that ASI224 on Celestron 14" F/11 have scale of 0.2" per pixel.

 

100 pixels are equal to 20" which is far more than current angular distance between Sirius A and B.



#5 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 17 February 2017 - 02:36 PM

Okay, then is there a star in this position next to Sirius? I would be happy to acknowledge another star in this position. I am not attached to this being Sirius B.  Please let me know. Thanks also for the math.

 

See also Damian Peach's captures of Sirius B:  http://www.damianpea...om/binaries.htm Scroll down the page midway.


Edited by Thomas Ashcraft, 17 February 2017 - 03:04 PM.


#6 Aleksandr Naumov

Aleksandr Naumov

    Explorer 1

  • *****
  • Posts: 70
  • Joined: 23 Jun 2014

Posted 17 February 2017 - 04:02 PM

Thomas,

 

first of all, thank you for your video, and for the link.

I will apply my math to images found there.

 

Is it possible to make simple experiment? Please do if you can.

 

Put Sirius to the center of field, set the gain and other camera settings as you did, then start capture...

then slew telescope at 1x siderial speed so that Sirius appears to the left then to the right from center of field.

 

If there is real Sirius B, it will follow Sirius A and distance between them will not change;

if there is parasitic glare, it will move opposite direction, or distance between A and B will change.


  • Cpk133 likes this

#7 Redbetter

Redbetter

    Gemini

  • *****
  • Posts: 3350
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 17 February 2017 - 08:46 PM

Looks like glare in the video.  I say that because it is moving slightly away from Sirius A as the frames progresses from when the first hint of it appears.  And if you place a ruler against the screen you can see that Sirius A is moving from its original position.

 

Glare/ghost artifacts are easier to detect when the pair is drifting through the field.  The orientation and separation will shift to varying degrees as the bright primary moves across the field and the secondary's position will be different depending on where you place the primary in the field.



#8 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 17 February 2017 - 10:18 PM

Scrutiny is good. Thank you for looking and questioning.



#9 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 17 February 2017 - 10:25 PM

Here are two prior images of possible Sirius B from October 22 2016 and October 21 2016. Sirius B is more pinpoint looking in better seeing back then.

 

 

Attached Thumbnails

  • post-35898-0-72712500-1477167317_thumb.png

Edited by Thomas Ashcraft, 17 February 2017 - 10:38 PM.


#10 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 17 February 2017 - 10:34 PM

Here is possible Sirius B from Oct 21 2016.

 

 

Attached Thumbnails

  • post-35898-0-75116300-1477067303-2.png


#11 Redbetter

Redbetter

    Gemini

  • *****
  • Posts: 3350
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 18 February 2017 - 02:23 AM

I can't tell you if the images are correct since I don't know the image scale or the orientation employed (straight thru, diagonal?)   Sirius B is not hard visually for large aperture scope at this time even in poor seeing in my experience, so the best way to verify is visually.  For something with similar separation you could image Rigel with the same configuration.  That will provide a separation of about 1 arc second less than Sirius B, but is much easier to see visually, even in an 80mm scope.



#12 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 18 February 2017 - 10:41 AM

Rigel B with same straight through setup configuration.

 

Attached Thumbnails

  • post-35898-0-65546100-1477149039.png


#13 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 18 February 2017 - 10:43 AM

 

Is it possible to make simple experiment? Please do if you can.

 

Put Sirius to the center of field, set the gain and other camera settings as you did, then start capture...

then slew telescope at 1x siderial speed so that Sirius appears to the left then to the right from center of field.

 

If there is real Sirius B, it will follow Sirius A and distance between them will not change;

if there is parasitic glare, it will move opposite direction, or distance between A and B will change.

Will try this when the weather clears next week. Thanks.



#14 Redbetter

Redbetter

    Gemini

  • *****
  • Posts: 3350
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 19 February 2017 - 01:09 AM

I am not sure what to make of the images.  There is a big diffraction spike in two them, not sure what that is from and why it is absent from the 3rd.  Orientation of the spike is different in the second, I don't know if this implies a different camera orientation, or non equatorial starting field location or something else. 

 

Assuming the October 22nd is approximately oriented as shown, then it is probably a good match for PA and separation if the images scale of Rigel is the same.  I determined this by measuring from the center of the stars to the center of the companion on the screen. 

 

The October 21st image, if aligned the same way (assuming the diffraction spike has turned), is not showing the companion if the image scale is the same.  The separation and PA of the brightest of the multiple secondary points are wrong (and the brightest one is far too close.)  In fact, if the overall image rotation is within a few degrees of the 22nd, and the diffraction spike is the only thing that shifted noticeably then it is likely masking Sirius B.  There is a very subtle brightening of the upper edge of the first bright node of the spike at the right distance.  It is possible that it is hidden there.

 

Visually with the 20" I can see the Pup even on the diffraction spikes as the orientation changes during the evening if the seeing isn't too bad.  The vanes on mine are extremely thin considering the aperture, and this is far enough from the center of Sirius that the effect of the Pup on the spike becomes additive rather than masking.



#15 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 19 February 2017 - 10:15 AM

Redbetter wrote: "There is a big diffraction spike in two them, not sure what that is from and why it is absent from the 3rd."

 

Hi Redbetter. Thanks again for your analysis and measurements. That spike is from a 3/4 inch pole that holds a windbreak a couple of feet in front of my telescope.

 

Just to reiterate. I have been casual in these observations and have not been scientific regarding camera orientation from session to session. If I post in the future I will put a little more effort into it.

 

Clear and steady skies.



#16 xHarry

xHarry

    Vostok 1

  • -----
  • Posts: 158
  • Joined: 02 Nov 2016
  • Loc: Lafayette, Ca

Posted 20 February 2017 - 03:22 AM

Thomas,

I will try to photograph Sirius A & B as soon as the weather clears. But I am just learning how to use my equipment. 

But let me ask, could there be a barlow in your train?

 

Harry



#17 dotnet

dotnet

    Ranger 4

  • -----
  • Posts: 313
  • Joined: 27 Jun 2013
  • Loc: Australia

Posted 20 February 2017 - 05:29 AM

The camera have resolution of 1304x976 and have 4:3 aspect ratio, the same as 640x480.

So I assume original image was proportionally scaled before uploading here. Scale factor is 0.491.

[...]

100 pixels are equal to 20" which is far more than current angular distance between Sirius A and B.

If however the image was cropped, rather than scaled, we arrive at a distance of about 10 arc seconds, which is the correct distance between Sirius A and B.

 

So, was the camera image scaled or cropped?



#18 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 20 February 2017 - 10:50 AM

Harry wrote:  "Thomas,

I will try to photograph Sirius A & B as soon as the weather clears. But I am just learning how to use my equipment.

But let me ask, could there be a barlow in your train?"

 

Regarding the images at the start of this thread: No barlow but I think I had an atmospheric dispersion corrector in place at the time. I am not sure how an ADC changes things like focal length. I am new to this as well.



#19 Thomas Ashcraft

Thomas Ashcraft

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1578
  • Joined: 10 Dec 2007

Posted 20 February 2017 - 11:08 AM

Dotnet wrote : "If however the image was cropped, rather than scaled, we arrive at a distance of about 10 arc seconds, which is the correct distance between Sirius A and B.

 

So, was the camera image scaled or cropped?"

 

I did not crop or scale. But I am not sure what Autostakkert does in its process. I think Autostakkert centers the image so maybe that has an effect?

 

Here is an unprocessed single frame screen grab from the original .avi file.

Attached Thumbnails

  • SiriusFeb172017_0333utscreen-grab.png



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.







Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics