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Equipment Discussions >> Video and Electronically Assisted Astronomy

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chasing photons
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Reged: 03/19/13

Loc: Minnesota
Re: Which one will work best? *DELETED* new [Re: Chris A]
      #6341285 - 01/28/14 03:30 PM

Quote...

"Just thought I would jump in here and add my thoughts about this. David you must remember that video cameras use much smaller CCD sensors than actual CCD imaging cameras. By having a 1/2" sensor or even smaller makes the FOV very limited for most DSO's. Unless you plan on only observing planetary nebulas or certain NGC's or PGC's type galaxies, you really need to have two very different scopes. Yes using a C14 in Hyperstar mode for an f/1.9 or 675 mm focal length will provide more resolution than a C8 in Hyperstar mode for an f/2 or 406 mm focal length, but the photons will be collected onto the CCD sensor at almost the same rate, however, the C8 will have slightly less then 2 x the FOV. Many of the very common DSO's require when using a 1/2" CCD sensor 200 to 500 mm focal length in order to fit the object of interest into the FOV and even one of the largest **fastest** scopes like the C14 Hyperstar cannot fit the bill. This is why the 70 to 100 mm aperture refractor tend to be so popular amount us video observers and yes we have larger aperture scopes for the smaller objects.

Aperture is only king when it comes down to viewing into your eyepiece using your eye(s). When it comes down to video observing aperture benefits mainly globular clusters and the extra needed resolution only when the object can fit the FOV.

Chris A
Astrogate "

+1 to Chris

for the most accurate, clear and complete explanation so far.

I try to remember the important points for imaging like this:

Think small focal ratio for faster integration.
Think small focal length for larger field of view.
Think larger aperture for higher resolving power (more detail).

Remember that larger apertures will have longer focal lengths, even at very fast (hyperstar) focal ratios.


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David PavlichAdministrator
Transmographied
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Reged: 05/18/05

Loc: Mandeville, LA USA
Re: Which one will work best? *DELETED* new [Re: A. Viegas]
      #6341349 - 01/28/14 04:03 PM

Quote:

David

Let me try and explain from a real life example. If I use my 80mm refractor on an object like M27 let's say. I can expose for 30 seconds and with no focal reduction (F7 scope) I am shooting at 600mm and my FOV is 39' x 26' Then I crank up my C11 and with reducers (F3) I can get down to just over 800mm. And my FOV is 28' by 20'.

Ok. So what gives? Ignoring the vignetting from the high reduction the C11 can produce that same image in terms of colors and brightness in much less time like 10 seconds. So yes you gain with aperture in terms of speed yet there is a give back. In my extreme light pollution the background in the 80mm is darker and there is more haze from the sharp reduction in the C11. Moreover as I mentioned there is
Likely to be vignetting with such extreme reduction.

I use my C11 more than my 80mm. But now that I have two video cameras I am planning to use them both at the same time on both scopes to get the best of both worlds

Hence the solution is easy. Have at least two telescopes, a larger aperture and a smaller one and have at least two video cameras.

Easy


Al




And this is the solution I've been waiting to hear! Multiple scopes which is no different than imaging with a CCD or viewing through an eyepiece. You can have the brute force of a 16" Meade SC and never view M45 in all its glory, but in the same breath, you can have an 80mm LZOS triplet apochromat and never see NGC 891 from my backyard. M45 will look good in the 80 and NGC891 will leap out of the eyepiece with the 16" Meade.

My interest, and I should have stated this earlier, is the small stuff that looks like a smudge in a typical backyard 10 or 12" scope, ie, my favorite hard to see object from my backyard due to light pollution NGC891.

Suffice it to say, when it's all boiled down, there's not a heckuva' lot of difference when comparing FOV and image scale between visual, imaging and video.

David


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Chris A
scholastic sledgehammer


Reged: 02/03/07

Loc: Toronto, Canada
Re: Which one will work best? *DELETED* new [Re: David Pavlich]
      #6341364 - 01/28/14 04:08 PM

David to be honest I really do not think that an 11 to 14" scope is a large aperture scope. I would say it is decent size aperture but not large. Now when were talking about a 16 + inch scope now that is large, but my feelings have not change from what I previously wrote.

My reason from moving up from the C9.25" to the VRC10" scope was not for the extra little aperture. ** It was for the corrected flat field that was required for my MC Universe and for the high quality optics. I also use an 80 mm f/6.2 TMB triplet refractor for the wide field objects and also high quality Canon lenses for the extreme wide field objects.

Where are the broadcasters on NSN using the "big reflectors"?? There are a lot more objects that are a fair size then just M45 & M31. When it comes to *video or imaging* how do you increase photon capture with aperture, please explain this? An equal focal ratio of both scopes will collect the same amount of light within the same time frame. The reason why globular clusters look nicer in a larger aperture scope when it comes down to video or imaging is because of the resolving power and that is it.

Chris A
Astrogate


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Chris A
scholastic sledgehammer


Reged: 02/03/07

Loc: Toronto, Canada
Re: Which one will work best? new [Re: scopenitout]
      #6341377 - 01/28/14 04:14 PM

For me this would be the only exception if I had only one chance to own one scope. The C11 with Hyperstar when used with a Mallincam or any other video camera that offers a 1/2" CCD sensor would fit the majority of objects from fairly large nebulas or open clusters to really small planetary nebulas/galaxies.

Chris A
Astrogate


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Dwight J
scholastic sledgehammer
*****

Reged: 05/14/09

Loc: Lethbridge, Alberta, Canada
Re: Which one will work best? *DELETED* new [Re: Chris A]
      #6341379 - 01/28/14 04:16 PM

A case in point: I use several scopes for astrovideo to achieve different results. I use a C6 @F2.8 for wider fields like open clusters or M31or M42 that will not fit the field of either my C11 or C14 regardless of how much I can reduce them. Being able to vary the focal ratio and, thus focal length of a scope gives it versatility that Newtonians have a hard time doing because of limited inward focus travel. You can move the primary mirror or modify the truss tubes but this isn't the easiest task. Then it becomes less than optimal for visual use. The VRC's @F8 are modified to work well with focal reducers to get down to the astrovideo sweet spot of F5 or less.
I have seen amazing images done on large Newts but M27 filled the field of view. And that was at F3. Nice for small objects but it would take a week to look at the Veil Nebula.


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Chris A
scholastic sledgehammer


Reged: 02/03/07

Loc: Toronto, Canada
Re: Which one will work best? *DELETED* new [Re: gary-sue69]
      #6341381 - 01/28/14 04:16 PM

Gary that would be an awesome combination and adding a focal reducer for both scopes into the equation would be even better.

Chris A
Astrogate


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Chris A
scholastic sledgehammer


Reged: 02/03/07

Loc: Toronto, Canada
Re: Which one will work best? *DELETED* new [Re: chasing photons]
      #6341403 - 01/28/14 04:27 PM

Thank you Todd. There are just so many different size objects in the universe that one scope does all even with reducers just cannot cut it. David and others who think along the same terms must also keep in mind that these larger scopes will require a big expensive mount and if you do not have a permanent observatory good luck to you setting up & tearing down at each and every session. Even the big Dobs have their limitations when it comes down to tracking (unless you buy the Servocat system or equivalent) and where they can function in certain altitudes (limited towards Zenith where this is usually the best area of ones sky).

Clear skies,

Chris A


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Chris A
scholastic sledgehammer


Reged: 02/03/07

Loc: Toronto, Canada
Re: Which one will work best? *DELETED* new [Re: Dwight J]
      #6341406 - 01/28/14 04:29 PM

Great explanation Dwight and great to see you here again!

Cheers,

Chris A


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Chris A
scholastic sledgehammer


Reged: 02/03/07

Loc: Toronto, Canada
Re: Which one will work best? *DELETED* new [Re: David Pavlich]
      #6341418 - 01/28/14 04:35 PM

No David the key point that you mentioned was this "My interest, and I should have stated this earlier, is the small stuff that looks like a smudge in a typical backyard 10 or 12" scope" and therefore you will require a larger aperture scope in order to allow you to get the *fastest* focal ratio possible while maintaining a decent *image scale*.

Chris A


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David PavlichAdministrator
Transmographied
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Reged: 05/18/05

Loc: Mandeville, LA USA
Re: Which one will work best? *DELETED* new [Re: Chris A]
      #6341432 - 01/28/14 04:43 PM

Quote:

David to be honest I really do not think that an 11 to 14" scope is a large aperture scope. I would say it is decent size aperture but not large. Now when were talking about a 16 + inch scope now that is large, but my feelings have not change from what I previously wrote.

My reason from moving up from the C9.25" to the VRC10" scope was not for the extra little aperture. ** It was for the corrected flat field that was required for my MC Universe and for the high quality optics. I also use an 80 mm f/6.2 TMB triplet refractor for the wide field objects and also high quality Canon lenses for the extreme wide field objects.

Where are the broadcasters on NSN using the "big reflectors"?? There are a lot more objects that are a fair size then just M45 & M31. When it comes to *video or imaging* how do you increase photon capture with aperture, please explain this? An equal focal ratio of both scopes will collect the same amount of light within the same time frame. The reason why globular clusters look nicer in a larger aperture scope when it comes down to video or imaging is because of the resolving power and that is it.

Chris A
Astrogate




The big aperture screen captures that I mentioned that Jack shows us at our meetings were from star parties where guys with big dobs have Mallincams. I'll have to talk to Jack to get particulars, but there is no denying that there were some impressive images.

You sort of made my argument by saying that larger apertures work good for resolving globular clusters. Why wouldn't they resolve other objects as well? And there's a reason why research telescopes are getting bigger, not smaller. They resolve better than small scopes.

Like I said in a previous post, one scope will not do everything whether it's video, visual or CCD/DSLR imaging. I know that without ever owning a video camera. And that is what has been stated here. You wouldn't use an FSQ106ED if your goal was to image nothing but planetary nebula. And you wouldn't use a C14 non-hyperstar if your goal is to image big objects like M45.

Still, if you want better resolution, you need aperture. There's a reason that Hubble has a 2.4 meter mirror and not a TOA150.

David


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Chris A
scholastic sledgehammer


Reged: 02/03/07

Loc: Toronto, Canada
Re: Which one will work best? *DELETED* new [Re: David Pavlich]
      #6341470 - 01/28/14 05:08 PM

David I have tried my best to explain to you in simple terms what I have learnt over the past 20 years starting out as a visual observer, CCD imager and finally ending up the pass 6 years observing with a video camera. I really see no point going forward with this discussion since your mind is set and it is just a waste of time. I really cannot see how you can state these facts regarding "video/aperture" since you have not even used an astro video camera.

BTW - those images that Jack is showing you are captured at Chiefland which is Florida's dark sky location. Dark skies are another equation but we won't get into that right now

Chris


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csa/montanaModerator
Den Mama
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Reged: 05/14/05

Loc: montana
Re: Which one will work best? *DELETED* new [Re: Chris A]
      #6341522 - 01/28/14 05:42 PM

Let's get back to assisting the OP with his questions.

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gary-sue69
sage
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Reged: 07/19/07

Loc: Maybee MI.
Re: Which one will work best? *DELETED* new [Re: Chris A]
      #6341540 - 01/28/14 05:51 PM

I will have a roll-off permanent observatory. It will be remote controlled

How well will a AT65EDQ 65mm f/6.5 ED quadruplet work compare to the Meade Series 6000 80mm f/6 ED triplet apo? or is the AT65EDQ to small? there was a lot of picture I saw on the web that was great. But they used a DSLR.

Edited by gary-sue69 (01/28/14 06:03 PM)


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A. Viegas
scholastic sledgehammer
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Reged: 03/05/12

Loc: New York City/ CT
Re: Which one will work best? *DELETED* *DELETED* new [Re: gary-sue69]
      #6341573 - 01/28/14 06:09 PM

Post deleted by csa/montana

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gary-sue69
sage
*****

Reged: 07/19/07

Loc: Maybee MI.
Re: Which one will work best? *DELETED* new [Re: A. Viegas]
      #6341595 - 01/28/14 06:23 PM

read my first post. that will explain, this is for a mallincam. which is a video camera.

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Chris A
scholastic sledgehammer


Reged: 02/03/07

Loc: Toronto, Canada
Re: Which one will work best? *DELETED* new [Re: gary-sue69]
      #6341680 - 01/28/14 07:12 PM

Gary the AT65EDQ 65mm f/6.5 ED quadruplet will have a focal length of 423 mm and the Meade Series 6000 80mm f/6 ED triplet apo will have a focal length of 480 mm. Either both scopes will be great for wide field observing with a Mallincam. The AT65EDQ 65mm will have a very slight edge in FOV but the Meade Series 8000 80 mm will be a bit faster. I would go if I had to choose between the two for me it would come down to cost but if they cost almost the same then the Meade Series 6000 80mm f/6 ED would be my choice.

Chris


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gary-sue69
sage
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Reged: 07/19/07

Loc: Maybee MI.
Re: Which one will work best? *DELETED* new [Re: Chris A]
      #6341727 - 01/28/14 07:35 PM

Thanks for all the help. I think at less with the great info I know which way to go

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Chris A
scholastic sledgehammer


Reged: 02/03/07

Loc: Toronto, Canada
Re: Which one will work best? *DELETED* new [Re: gary-sue69]
      #6341989 - 01/28/14 10:11 PM

your very welcome Gary all the best.

Chris


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BJS
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Reged: 05/23/09

Loc: NW Ohio
Re: Which one will work best? *DELETED* new [Re: Chris A]
      #6348934 - 02/01/14 11:36 AM

Gary

I am close to you in Toledo. Send me a PM. I have used a MC with similar scopes as you originally asked about.

Brian


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