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Double Star images

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#1 Brian Risley

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Posted 15 January 2013 - 12:44 AM

I was really surprised about how easy it was to image some double stars with a CPC-800 and a SPC-900 webcam.
I utilized an Ultima 2x shorty barlow with just the visual back, no diagonal.
I am attaching images of Rigel, Sirius, the trapezium (6 stars if you look closely) and Jupiter, all taken without touching the imaging stack. I really love the CPC, I had alignment right on, for almost all the objects I went after, the objects were in the imaging window! These images are single frame raw dumps out of the avi files.
I never realized how easy it was to do this. (We also did Sirius with a C-11 with an Orion Imager, and had very similar images when the gain was adjusted to keep Sirius from blooming too much. The imager blows out the SPC-900 on faint objects, but with Sirius, the best images were very similar.)
Brian

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#2 jimarshall

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Posted 15 January 2013 - 12:07 PM

Beautiful images Brian,
I would never have guessed that the SPC 900 could image Sirius b. I would like to try this since I have never had any luck seeing it visually...what settings did you use and should I even bother to try with a C-8 and SPC900NC?

#3 TG

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Posted 15 January 2013 - 12:54 PM

Congratulations on capturing Sirius B. I've always visually wanted to spot it but its too low for us and the weather in winter is uniformly bad.

Tanveer.

#4 Brian Risley

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Posted 15 January 2013 - 09:33 PM

I was really surprised to get it, and only felt for sure I had it when I compared it to Rigel. I just set things to max (or near max) on gain and adjusted the exposure time til A did not blow it out, I think I was near max exposure. I used a Celestron Ultima 2x barlow, so I suspect you would need something like that. Jim, a C-8 and the SPC is exactly what I used.
We did try to visually see b in the CPC-800, but we couldn't.
Brian

#5 jimarshall

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Posted 16 January 2013 - 12:02 PM

I was really surprised to get it, and only felt for sure I had it when I compared it to Rigel. I just set things to max (or near max) on gain and adjusted the exposure time til A did not blow it out, I think I was near max exposure. I used a Celestron Ultima 2x barlow, so I suspect you would need something like that. Jim, a C-8 and the SPC is exactly what I used.
We did try to visually see b in the CPC-800, but we couldn't.
Brian

Thanks, I'll give it a try when the weather clears.

#6 GeneT

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Posted 16 January 2013 - 05:29 PM

Very nice and very interesting!

#7 Ed Wiley

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Posted 16 January 2013 - 06:35 PM

Double star imaging is my major activity these days. I capture with a DMK21 through my D-K, measure them and then publish the measures in JDSO. It is a great citizen science activity and I can easily justify new equipment by saying: "But Honey, its for science." :grin:

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#8 drksky

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Posted 16 January 2013 - 07:27 PM

What kind of exposures are you using with the DMK21? I'm curious about possibly doing something like this as well. What kind of aperture is needed? Is it possible to do something like this with a scope as small as 130mm refractor?

#9 Cepheus Elf

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Posted 17 January 2013 - 05:53 PM

Great images!! I've taken some double star images of wider pairs with my dslr, but i might have a go at some closer pairs!!

Mick

#10 Ed Wiley

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Posted 17 January 2013 - 06:02 PM

Hey Tony:

I have seen JDSO papers using small refractors and Celesctron NexImage (<$100) video camera. You can also use DSLRs in picture or video mode, CCDs and even cell phones. If you happen to have a DMK21, then use the same kind of techniques the planet guys use. For example, I will take 1000 frames of video at the fastest possible speed that shows both stars and does not saturate either star. (Trial and error rules here!) For bright pairs of more-or-less equal magnitude I have gone as fast as 1 millisecond (1/1000). On faint pairs as slow as 2-3 seconds.

If I was thinking "pretty picture" rather than "science" I would use a color camera. But color cameras can also be used for "science pictures," they are just not as sensitive.

Good work can certainly be done with a 130mm refractor, you just have to pick the appropriate pairs. You are not going to be able to split a 1" pair with a 130mm scope, but there are plenty of wider pairs. The trick is to pick some fairly bright ones of more-or-less equal magnitude and try your luck with something on the order of 15-20" separation and then try closer until you reach your limit.

best sources of information are looking through JDSO articles and Florent Losse's web pages:

http://www.jdso.org/
http://www.astrosurf...fosaf/index.htm
(See English link "The webcam is a micrometer")

Clear skies, Ed

STF73AB: 324.4d, 1.1"
stack of 100/1000
16 milliseconds

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#11 drksky

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Posted 17 January 2013 - 06:43 PM

Thanks for the information, Ed. While I don't have a DMK21, I have a Flea 3 on the way. It's CMOS instead of CCD, but I can't see how that would make a difference. I may have to give it a try.

#12 Ed Wiley

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Posted 19 January 2013 - 12:30 AM

Hi Tony:

In fact, many prefer the Flea to the DMK. Give it a try!

Ed

#13 freestar8n

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Posted 19 January 2013 - 04:32 AM

Here is zeta bootes from July, 2011 when it was about 0.53" apart. Lumenera on C11 with Sloan r' filter. Stack of 9 selected frames with no sharpening.

Frank

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#14 Ed Wiley

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Posted 19 January 2013 - 11:53 AM

Nice, Frank! Up until now I have done all my imaging with a 8" DK but recently picked up a C-11 Edge. Your images gives me hope that I can get closer with the C-11. Obviously the optical quality is up to the task.

BTW: for those who are interested in measuring these close doubles: REDUC has a "surface" routine that corrects for separation errors that occur when the pair is "tight."

Ed






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