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Equatorial mount telescope double star observing

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#1 betaman42

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Posted 12 April 2013 - 04:25 PM

I'm really curious about double star observing and making measurments but my alt/az dobsonian isnt that easy to work with so I'm weighing my options. I've been considering getting an equatorial mounted telescope but I'm not sure what apreature size is best, which type is best reflector or refractor. In other words I'm looking for a really nice but not to expensive equatorial mount telescope that's capable of double star tracking and measuring.thanks!

#2 WRAK

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Posted 12 April 2013 - 04:37 PM

Any scope of reasonable optical quality will do it. Aperture is only a question regarding separation you want to be able to resolve in terms of Dawes criterion 116/D_mm giving arcseconds for equal bright doubles of about +6mag.
Wilfried

#3 betaman42

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Posted 12 April 2013 - 05:48 PM

Do you suggest a mounted reflector refractor as in know the differences between them but not in the context of double star observations

#4 Ed Wiley

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Posted 12 April 2013 - 07:01 PM

It depends on what you want to measure and how you are going to use the measures. If for your own pleasure, then you can go one route. For example, just about any decent scope with tracking and an astrometric eyepiece will give many hours of enjoyment. If you are thinking about joining those of use who measure and publish the measures, then you will probably go another route. If this is your goal, I suggest googling JDSO and looking at some of the papers citizen scientists have published. There are all sorts of ways to take and good (=publishable)measures can be obtained from surprisingly small apertures and modest mounts using any variety of telescopes and measuring tools, including astrometric eyepieces, DSLRs, video cams, CCDs, etc.

Regarding scopes, I use a Dall-Kirkham and an SCT. I can't afford to house an 8" or 11" refractor much less buy one.

I do hope you will consider getting into measuring for publication. We are a small group compared to the variable star community and there are lots of doubles.

Clear skies, Ed

#5 betaman42

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Posted 12 April 2013 - 08:20 PM

Thanks for the info Ed..yeah I'm more interested in actually punlishing results it's the coolest thing to be able to go beyond an amature and contribute to science! Ive read jdso publications and that's agood place to start ill still be weighing my telescope options in tbe meantime any more suggestions anyone feel free to comment

#6 buddyjesus

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Posted 13 April 2013 - 12:15 AM

i share your enthusiasm and wish to someday publish some measurements of my own. What is your budget again?

My ideal set up would be something like this. https://www.astronom...unt_p20046.aspx The aperture is good, this will double as a grab and go, and you can use goto with imported coordinates to find the doubles that are neglected.

Another option is to get a clearance cg5 with either a 6" reflector or a 4" refractor.

#7 WRAK

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Posted 13 April 2013 - 07:19 AM

The method used for measurements should also have an impact for the choice of scope. If you intend to use the standard 12.5mm eyepiece you will need at least a magnification of x400 if you want to measure separations below 10 arcseconds. This means an aperture of at least 200mm or more and a focus length of 2500mm if using a x2 Barlow - meaning an 8" f12 refractor or with less cost and bulk an 8-9" f12 folded optics reflector - best with an open tube to avoid problems with temperature issues and dew.
Wilfried

#8 Ed Wiley

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Posted 13 April 2013 - 10:10 AM

Hi Betaman42:

While you are thinking -- check out REDUC.

http://www.astrosurf...fosaf/index.htm

Webcams are very powerful tools for measuring doubles. The actual imaging is similar to that done by planetary imagers, reeling off frames and "freezing" the seeing. Tracking only has to be good enough to keep the pair on the frame, so you don't need a super mount. IMHO if yo are serious about publishing useful results a webcam is the tool of choice regardless of scope choice.

Clear skies, Ed

#9 betaman42

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Posted 13 April 2013 - 11:00 AM

Yeah that's another area o uncertainty..I'm not sure if I should use something like a celestron microguide or a webcam.I not too familiar with the use of a webcam though an also should I be looking at a telescope that has a drive?thanksS

#10 WRAK

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Posted 13 April 2013 - 05:05 PM

If you are satisfied looking at pictures on your PC then you maybe need not even a scope but can use existing images.
Wilfried

#11 Ed Wiley

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Posted 14 April 2013 - 06:53 PM

betaman42: If you are going equatorial and if you have a laptop and want to measure and publish, then please think webcam or DSLR if you have one that captures video.

Ed

#12 betaman42

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Posted 15 April 2013 - 02:02 PM

What are some webcams that work well for double star measuring because doing research I read that most are just good enough for capturing planets moon sun ect

#13 Ed Wiley

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Posted 15 April 2013 - 10:35 PM

Right, betaman42, most imagers use webcam for solar system work, but if you follow the link I left above for REDUC you will see how they are used for measuring double stars. Losse tells you exactly how to do it and provides many examples.

Ed






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