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Photo of Mu Cygni

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#1 Far Star

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Posted 26 October 2019 - 06:09 AM

Last night I took the following photo of Mu Cygni (m = 4.75 / 6.18, sep. (2020.0) = 1,46"), single frame with Canon 800D, APM 140/980 mm SD-Doublet @ f/23 (3.3 x Barlow), ISO 6400, shutter speed 1/250 second:

 

 

Photo-for-Cloudy -Nights.png

 

 

Clear Skies,

 

Ulrich


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#2 flt158

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Posted 26 October 2019 - 07:42 AM

That's an astounding image, Ulrich. 

There are 3 stars here. 

A and B are seriously tight almost in a north - south direction. 

C is not visible of course. It's too faint.  

But D is! Its magnitude is 6.9 at a PA of 44 degrees. 

 

Mu Cygni is one of your best yet, Ulrich. 

Thank you very much. 

 

Clear skies, 

 

Aubrey. 



#3 Far Star

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Posted 26 October 2019 - 04:20 PM

Thank you for your kind words, Aubrey.


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#4 ssmith

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Posted 28 October 2019 - 07:06 PM

Hi Ulrich -

I am having some trouble interpreting your photo. Like Aubrey, I can see three star-like images but their location and scale makes me wonder what exactly you captured.

Are you saying that you captured A,B & D as Aubrey alluded to or only A & B?

The problem arises when you compare the separation of the purported AB pair with the fainter 3rd star which would have to have a separation 123 times the A-B separation if it were D (1.7” vs 197”).

My thought is that one of the images on your photo may be a phantom or ghost image created due to the vibration of the shutter or wind or just unsteady seeing. I have seen this on some of my photos of close pairs.

What is your image scale?

Below is a photo of Mu Cygni that I took which shows just how extreme the separation is between the AB pair and the D component, which barely registers on my photo. I calculated the image scale on my photo to be ~0.16” per pixel after resampling.

It is hard to reconcile my image with yours.

mu cyg cc_120mm 11-15-16 002a_c non linear.jpg

Edited by ssmith, 28 October 2019 - 07:08 PM.

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#5 Far Star

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Posted 29 October 2019 - 05:05 AM

I cannot see a third star in my photo. If you see a third dot, it's probably an artifact that occasionally occurs at such high ISO (6400).

 

I took the photo with a Canon 800D, a 140 mm refractor with a focal length of 980 mm (f/7) and a Baader Hyperion Barlow. The native magnification factor of the Barlow is 2.25x. Between the camera and the Barlow I inserted a 40 mm T2 extension (see the following photo). As a result, the magnification factor of the Barlow lens was increased from 2.25x to about 3.3x (I have tested this). Therefore, the focal length was about 3,200 -3,250 mm.

 

Hence the focal ratio was about f/23. Since the pixel size of the Canon 800D's sensor is 3.7 microns, the focal ratio of f/23 equals about 6 times the pixel size in microns. So I followed the rule of thumb recommended by Jerry Lodriguss in this article:

 

https://www.skyandte...ooting-doubles/

 

 

Canon-800D-Hyperion-Barlow.jpg


Edited by Far Star, 29 October 2019 - 05:20 AM.


#6 ssmith

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Posted 29 October 2019 - 08:15 AM

That's an astounding image, Ulrich. 

There are 3 stars here. 

A and B are seriously tight almost in a north - south direction. 

C is not visible of course. It's too faint.  

But D is! Its magnitude is 6.9 at a PA of 44 degrees. 

 

Here is what we were seeing and interpreting as 3 stars:

 

mu cyg farstar.jpg

 

There is clearly a bit of image bounce and that is why some of us were unsure of what exactly you were showing us.

 

That is a fine split of the AB pair.  If you have the ability to stack multiple images you could clean up the image even more.



#7 Far Star

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Posted 29 October 2019 - 08:42 AM

Here is what we were seeing and interpreting as 3 stars:

 

attachicon.gif mu cyg farstar.jpg

 

There is clearly a bit of image bounce and that is why some of us were unsure of what exactly you were showing us.

 

That is a fine split of the AB pair.  If you have the ability to stack multiple images you could clean up the image even more.

Oh, I see! I think my mount (Vixen SX2 on Berlebach UNI 18) is not stable enough for the 140 mm refractor. Perhaps I need the SXD2.

 

Which camera do you use? Which software do you use for stacking?



#8 ssmith

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Posted 29 October 2019 - 09:17 AM

Ulrich -

 

There are several free stacking packages available such as AutoStakkert:  http://www.autostakkert.com/

 

I have also done manual stacking of a few frames using PhotoShop or Photoshop Elements where each photo is made into a separate layer and then the layers are blended.

 

My go-to photo processing software is PixInsight.

 

The camera I use is an Olympus E-PL5.



#9 Far Star

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Posted 29 October 2019 - 10:04 AM

Thanks Steve!



#10 flt158

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Posted 01 January 2020 - 02:12 PM

Hi Steve and Ulrich. 

I have just come in from observing Mu Cygni. 

I had not studied it since August 2016. 

My William Optics 158 mm F/7 apochromatic refractor was splitting it at 167X and 225X. 

At 140X the 2 stars were overlapping one another. 

But I kept going "wow, wow, wow" as I sussed its colours. 

A is yellow - white. B is pure yellow. 

The spectral classes are F6v and G2v.  

The C star is invisible. 

But the D star is good and gives me assurance I have the correct star. 

 

It's the 1st January 2020 and I already have a real winner here over in Ireland. 

 

Happy New Year all round to you all from Aubrey. 


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#11 dmdouglass

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Posted 01 January 2020 - 06:39 PM

This target (Mu Cgy) is indeed an interesting one.

Also known as STF-2822, and more specifically, the entire "complex" is known as WDS 21441+2845

And also, Herschel H-3-015.  Thus, as a Herschel object, on my target list.  I imaged it back in Aug 2018.

 

I gave up trying to catch AB. But there are 6 pairs in the group:  AB AC AD AF AG and BD

I wanted to capture as much of that as i could.  

My image was with an Edge 8", using an SBig 8300m, binned 1x1, with a resolution of .23 ArcSec/Pixel.

The shown FOV is 13x10 ArcMin. I was using a 2..4x Barlow.

 

To catch the dimer ones... i decided to use a 60 sec image, and stacked 8 of them.

Here is what i caught and measured:

 

.H-3-015-DS-20180828.jpg


Edited by dmdouglass, 01 January 2020 - 06:40 PM.

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