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Equipment Discussions >> Electronically Assisted Astronomy

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A. Viegas
Pooh-Bah
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Reged: 03/05/12

Loc: New York City/ CT
Re: Which one will work best? new [Re: gary-sue69]
      #6337545 - 01/26/14 08:42 PM

Gary - The LX850 is a great mount, congrats!!

The FLT-132 is an excellent APO. If you are planning on doing some serious AP in the future its a great scope. If you are just going to do video-astronomy then its probably overkill from what you can achieve using a similar sized Achro or even a larger SCT and focal reducer.

For the price of the FLT-132 I would instead get a SCT OTA 8-12" and a smaller 80-100mm refractor to piggyback on top. Giving you the best of both worlds...

just my 2c

Al


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RichardHC
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Reged: 09/18/13

Loc: South Australian Riverland
Re: Which one will work best? new [Re: Dragon Man]
      #6337733 - 01/26/14 10:17 PM

"With Video, 'Focal Length' is the most important factor to keep track of......."

Good dissertation Ken. I'm very new to this but already I can see that having a range of FLs available on the basic instrument is going to be the way to go.

I had looked at RC scopes and there's no doubt they produce a wide aberration-free field but with a 1/2 or 1/3 inch CCD (or CMOS) you aren't using a wide field so my decision has been to uses a fast Newtonian (8" F4 GSO Imaging Newtonian) which has the other major advantage of being cheap.


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Relativist
Post Laureate
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Reged: 10/11/03

Loc: OC, CA, USA
Re: Which one will work best? new [Re: RichardHC]
      #6337947 - 01/27/14 12:29 AM

That's exactly why I chose the AT8IN. You will be happy to know that my MCX2 comes to focus without issue.

In fact, I was considering for a while seeing if I could get a 10" f/3 made. The main reason I didn't get that is time & money. They are not readily available and custom jobs.


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David PavlichAdministrator
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Reged: 05/18/05

Loc: Mandeville, LA USA
Re: Which one will work best? new [Re: Relativist]
      #6338254 - 01/27/14 08:23 AM

Quote:

That's exactly why I chose the AT8IN. You will be happy to know that my MCX2 comes to focus without issue.

In fact, I was considering for a while seeing if I could get a 10" f/3 made. The main reason I didn't get that is time & money. They are not readily available and custom jobs.




While it's quite spendy, the 10" PowerNewt is f2.84. And if you remove the flattener/corrector, it's a standard f4. It's made for 65mm back focus with the flattener in place.

David


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gary-sue69
sage
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Reged: 07/19/07

Loc: Maybee MI.
Re: Which one will work best? new [Re: Dragon Man]
      #6338442 - 01/27/14 10:25 AM

Quote:

Quote:

For video astronomy, aperture is king. And since you'll be reducing it anyway, the long focal length of the big Meade will just overpower the refractor. For the conventional, everyday objects, either would be fine, but when you start to poke around more distant, diffuse objects, the brute power of the Meade will be the ticket!

David




Sorry but no David.
That is a common misconception coming from years of peoples Imaging habits.
With Imaging, Aperture often is King.

With Video, Aperture is NOT.
It can actually work 'against' you.

With Video, 'Focal Length' is the most important factor to keep track of.
If you want to video observe small objects, use a slow scope with a medium to long focal length (often meaning a larger aperture).
If you want a wider FOV use a Focal Reducer.
If you want to video observe very large objects like the Sun, Moon, large Nebula, large Galaxy Clusters and open star clusters, use a short focal length, not a fast focal ratio.
For example, a 12" f5 is fast but is too long (1200mm) in focal length to assist in wide FOV video observing.

Whereas, a 600mm focal length scope will give a much better result, especially when focal reduced to 300-400mm.
The most common scopes to fill this spot is the ED80 refractor and 120mm f5 Achromat Refractors, and SCT's with Hyperstar (but not because of its aperture, but because of its short focal length).
There are also optimised RC scopes that work well because they have been set up for Video work.
They are called 'VRC telescopes'.

The trick is to get the focal length down, not necessarily the aperture up. Video Astronomy cameras are sensitive enough to not be handicapped by less aperture.





Hi Guys. I am a little confused, From rocks web site. They do look sweet, but even though they are built for rocks video camera. They have long focal length. VRC12T 2432 mm focal length F/8 Here is the info from his site.

Pictured Above is the New VRC12T Now in Stock!
After a long wait, MallinCam has received its first batch of VRC12T (Video Ritchey-Chretien) 12" optical truss tube. At 52.8 pounds including the supplied dual speed focuser, this work of art is truly within the reach of the most discriminating Live Video CCD observer and Videographer. It also works for any large sensor DSLR, Cooled CCD cameras. At F/8, It will provide excellent imaging platform.

* Center spotted secondary mirror made of Quartz with 99% reflectivity non-tarnishing multi-layer dielectric mirror coatings.

* 3 built-in cooling fans in rear cell.

* Two inch dual-speed Crayford focuser with 1.25" adapter.

* Carbon fiber with Serrurier truss tube design with CNC-machined stainless steel and aluminum components.

* Low thermal expansion quartz primary mirror with 99% reflectivity non-tarnishing multi-layer dielectric mirror coatings.

* Two Large D type "Losmandy" Dove tail on top and bottom.

* Comes with 3 sets of spacer rings to achieve perfect focus with any imaging cameras.



* 2432 mm focal length F/8



Intro Price:

Retail price 4995.99. MallinCam Intro price on the first batch 3999.99 US funds plus shipping


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mclewis1
Thread Killer
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Reged: 02/25/06

Loc: New Brunswick, Canada
Re: Which one will work best? new [Re: gary-sue69]
      #6338506 - 01/27/14 10:54 AM

Gary,

There's nothing really special about the VRCs ... they are the popular GSO RC scopes with the primary mirror moved slightly. There is nothing unique about them with respect to Rock's cameras. Rock's cameras use the industry standard C or C/S mount sensor spacing just like virtually every other video camera on the market.

The VRCs and regular GSO RCs will work with any video cameras and any appropriate focal reducers. The slightly different placement of the primary mirror means slightly different use of the spacer rings. For example with a particular setup you may need two rings on the regular GSO model and maybe only one on the VRC.

The VRCs may get a once over from Rock before shipping ... but that also means a scope will have traveled around a bit more than a US sourced GSO RC scope for a US customer.

The $4K price is certainly a very good price, but I would first make very certain that you can get one at that price since there is some friction between Rock and GSO over that number.


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gary-sue69
sage
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Reged: 07/19/07

Loc: Maybee MI.
Re: Which one will work best? new [Re: mclewis1]
      #6338576 - 01/27/14 11:42 AM

Thanks Mark. good info

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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? new [Re: Dragon Man]
      #6338666 - 01/27/14 12:27 PM

Quote:

Quote:

For video astronomy, aperture is king. And since you'll be reducing it anyway, the long focal length of the big Meade will just overpower the refractor. For the conventional, everyday objects, either would be fine, but when you start to poke around more distant, diffuse objects, the brute power of the Meade will be the ticket!

David




Sorry but no David.
That is a common misconception coming from years of peoples Imaging habits.
With Imaging, Aperture often is King.

With Video, Aperture is NOT.
It can actually work 'against' you.

With Video, 'Focal Length' is the most important factor to keep track of.
If you want to video observe small objects, use a slow scope with a medium to long focal length (often meaning a larger aperture).
If you want a wider FOV use a Focal Reducer.
If you want to video observe very large objects like the Sun, Moon, large Nebula, large Galaxy Clusters and open star clusters, use a short focal length, not a fast focal ratio.
For example, a 12" f5 is fast but is too long (1200mm) in focal length to assist in wide FOV video observing.

Whereas, a 600mm focal length scope will give a much better result, especially when focal reduced to 300-400mm.
The most common scopes to fill this spot is the ED80 refractor and 120mm f5 Achromat Refractors, and SCT's with Hyperstar (but not because of its aperture, but because of its short focal length).
There are also optimised RC scopes that work well because they have been set up for Video work.
They are called 'VRC telescopes'.

The trick is to get the focal length down, not necessarily the aperture up. Video Astronomy cameras are sensitive enough to not be handicapped by less aperture.





I guess those images I saw from someone's really big reflector were anomalies then. So what you're saying is that a C8 because it has great focal length is going to give better results than 20" f3.3 Newt?

Sorry, but if I were to do video astronomy and because I'd have but one telescope, it would be the biggest scope that I could stuff into my 8X8 rolloff.

David


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jrcrillyAdministrator
Refractor wienie no more
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Reged: 04/30/03

Loc: NE Ohio
Re: Which one will work best? new [Re: gary-sue69]
      #6338859 - 01/27/14 02:06 PM

Quote:

With Imaging, Aperture often is King.

With Video, Aperture is NOT.
It can actually work 'against' you.




Imaging is imaging. The chip doesn't know what kind of camera it is in. Aperture can never work against you. Focal length determines what image you will capture. Aperture then determines the S/N ratio attainable for a given exposure time because for a given focal length aperture determines F ratio. For a given focal length, smaller aperture = slower optics and vice versa.


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mclewis1
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Reged: 02/25/06

Loc: New Brunswick, Canada
Re: Which one will work best? new [Re: David Pavlich]
      #6338863 - 01/27/14 02:07 PM

David,

I agree, I'd also want the biggest aperture I could handle in a permanent or semi permanent setup (with accurate tracking, fast f ratio, and good accessibility). It would simply give me the most targets to view but if I wanted more flexibility for things like also showing others many of the show pieces in the sky I would prefer the C8 running at f3-4. That shorter focal length would nicely frame the bigger popular objects like M42, M8, M7, etc.

To me a C8 with a variety of focal reducers and Barlows and something like a Mallincam video camera is the goldilocks of video setups (not too big, not too small ... just right). Under reasonable skies it'll go deep enough to show challenging Hickson and some of the Arp type objects while still offering a great fov for those larger showpiece objects. With a 2-3x Barlow it's planetary images are very crowd pleasing as well.

It's aperture and focal length are enough to observe a wide variety of objects, and because the C8 is also light weight and compact it can be comfortably mounted on entry level goto EQ or Alt Az mounts. With that portability I'd be more inclined to quickly get it setup even on those marginal nights (so more observing) plus I'd be comfortable taking the setup to local outreach opportunities or good dark sites.

Sure a 20" would let me get finer details out of small galaxies and planetary nebula and show more stars in the globular clusters but if I also want a scope to use outside of my backyard something like that c8 is probably going to be my first choice.


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Dragon Man
Carpal Tunnel
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Reged: 03/07/06

Loc: Snake Valley, Australia
Re: Which one will work best? *DELETED* new [Re: David Pavlich]
      #6340319 - 01/28/14 07:36 AM

David, I do NOT say small Aperture is the best for Video.

I am saying Large Aperture isn't King. My words were "With Video, 'Focal Length' is the most important factor to keep track of."
'To keep track of'. If you want the video view to be clearer brighter and with more contrast, get the focal length down, and that is usually achieved by reducing the aperture. Larger apertures give longer focal lengths.

How many people own 20" f3.3 Newts? That is a whopping 1676mm focal length! Great for looking at tiny Planetary nebulas and inside Lunar Craters.

And your statement of "Sorry, but if I were to do video astronomy and because I'd have but one telescope, it would be the biggest scope that I could stuff into my 8X8 rolloff" tells me you have no real idea of the problems you will face, until you actually try using a mega scope with a very small sensitive 1/2" video camera sensor.
Unless you enjoy a FOV of only 10 Arcminutes or less, and low contrast.
Even in Imaging, an Imager captures a Large FOV because of the size of the Sensor. With the lack of a large format sensor we (Video Astronomers) compensate by creating a larger FOV on a small sensor by reducing the focal length.

I am not saying don't use large aperture scopes.

And to John Crilly,
You say:
"Imaging is imaging. The chip doesn't know what kind of camera it is in. Aperture can never work against you. Focal length determines what image you will capture. Aperture then determines the S/N ratio attainable for a given exposure time because for a given focal length aperture determines F ratio. For a given focal length, smaller aperture = slower optics and vice versa."

To start with, you say "Imaging is Imaging". But we aren't 'Imaging'. We are observing. S/N ratio is an Imaging term we aren't highly concerned with like Imagers are. With the cameras used in Video, Aperture CAN be your worst enemy if you go too large. Unless you want a close-up of very small objects.

Small aperture = fast optics because of the shorter focal length. We aren't talking about focal ratio.
As an example, 2 scopes with the same focal ratio, f5, give totally different FOV results because of their Focal lengths. One is 600mm focal length, the other is 1200mm focal length.
Yes, the one with 1200mm focal length is going to collect more light, but also give a very narrow FOV.

Because of the high sensitivity of the sensors used in Video Astronomy Cameras you don't need the HUGE apertures that are preferred with Traditional CCD Imaging.
What is preferred (and often necessary) is a wider FOV to allow the sensor to give a brighter image, with smaller sharper stars and more contrast. Quickly.

And your other statement "The chip doesn't know what kind of camera it is in."
You are assuming that all sensors are equal.
Video sensors are wayyy more sensitive, needing less integration time. Which means even small aperture scopes will collect the light faster than an Imaging camera.

Even the Mallincam VRC Scopes have a medium to large aperture but they have also been optimised to work well with Focal Reducers to give a nice FOV. Rock Mallin has spent a lot of time on research to make sure they work well and give a good FOV.
And obviously Large aperture SCT's work very well when used with Hyperstar or heavy focal reduction.
They work to bring the Focal Length down.

This is not a competition between Imaging and Video. It is about the difference between Imaging and Video.
The Video sensors, being more sensitive, need far less light collecting time. They can turn an 8" scope into the equivalent of a much larger scope.
So the user doesn't need to go bigger, the camera will do it for him.

I hope this post isn't deleted as readers may learn from it, about the fact that Aperture isn't the King with Video, just a nice thing to have if you want a tighter FOV.
Video works well at almost any aperture, but aperture IS NOT King.


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David PavlichAdministrator
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Reged: 05/18/05

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Re: Which one will work best? new [Re: Dragon Man]
      #6340514 - 01/28/14 09:49 AM

My exception to your answer is the "large aperture can work against you". Why is it that I see terrific images on NSN from guys using C11s and C14s? All I can judge by is what I see on the screen. Optical theory is great, but when I see terrific images on the screen and they're coming from big scopes, I have to assume that the combination works well. That's the basis for my reply, nothing more, nothing less.

David


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Dragon Man
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Reged: 03/07/06

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Re: Which one will work best? new [Re: David Pavlich]
      #6340612 - 01/28/14 10:38 AM

Quote:

My exception to your answer is the "large aperture can work against you".
David




Yes, just like I said. 'Can', not 'Does'.
My exception is your unfounded statement: "For video astronomy, aperture is king" when it isn't.
Yes, I too see 14" SCT's giving fantastic results with Focal Reducers or Hyperstar. Tom is a great example.
But try using the same camera in a huge Reflector. The bigger you go the harder it gets to get a decent result. So how can that be 'King'?

You will also find that larger Reflectors have trouble reaching 'In' focus with these cameras especially with a Focal reducer.
I am not just making this stuff up. I have tried all this, and read results of other peoples attempts too.
If you get the chance to use a Video Astronomy camera, try it in all sorts of aperture sizes, different focal lengths, and styles of scopes (SCT, Reflector, Maksutov, etc), and then see if you still agree with your own statement "aperture is king".

I hope you do get to try Video Astronomy as it is very rewarding in an Instant Gratifying way.


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scopenitout
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Reged: 08/24/13

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Re: Which one will work best? new [Re: Dragon Man]
      #6340764 - 01/28/14 11:33 AM

Using my C-11 and Mallincam Xtreme with a Hyperstar lens, I'd say that combination hits the "sweet spot" for aperture/focal reduction.

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gary-sue69
sage
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Reged: 07/19/07

Loc: Maybee MI.
Re: Which one will work best? new [Re: Dragon Man]
      #6340782 - 01/28/14 11:40 AM

Thanks to all. I have learned a lot, like always on CN. more info I get the better decision I can make. keep it up an thanks.

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Chris A
Pooh-Bah


Reged: 02/03/07

Loc: Toronto, Canada
Re: Which one will work best? *DELETED* new [Re: Dragon Man]
      #6340835 - 01/28/14 12:12 PM

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


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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]
      #6341027 - 01/28/14 01:32 PM

so a Meade LX850 12"OTA F/8 and an 80MM Series 6000 ED Triplet APO F/6 would be the way to go?

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David PavlichAdministrator
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Re: Which one will work best? *DELETED* new [Re: Chris A]
      #6341159 - 01/28/14 02:28 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




You used to use a C9.25, no? And now you're using a 10" RC, no? The 9.25 was non-Hyperstar and the RC is used at its native focal length with reducers. Am I correct so far?

Then why is it that when Jack brings images taken from screen captures only (no processing) do I see such great images from some of the guys that have their video cameras, mostly Mallincams, in their big reflectors? Like I said, IF I ever do the video thing, I'd use a big scope.

I can see how something like M45 or M31 wouldn't fit in the FOV, but that's pretty common with long focal length visual stuff as well. My sense is that you increase photon capture with aperture. If that doesn't help, then why bother with anything more than a 4 or 5" refractor? There must be a reason that you chose a 10" aperture scope over a 5" aperture scope.

And when it comes to Hyperstar, you still have that aperture to suck in the photons. What I'm gleaning from this is that why fool with Hyperstar when you can get a 5" refractor with the same focal length. But...you have 5" of aperture, with, say, the C11 Hyperstar, you have the shorter focal length, BUT, you have 11" of aperture. How can that not be better than the 5" of aperture?

David


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dragonslayer1
Pooh-Bah


Reged: 02/25/12

Loc: SLC, UT
Re: Which one will work best? *DELETED* new [Re: David Pavlich]
      #6341219 - 01/28/14 02:55 PM

Hey David, I can only comment on the 9.25 as thats what I have... It can be a real struggle to get the f/r fast enough to get good pictures because the more you try you start running into vigineting etc. There are some that get awesome pics, lets say M51 with small scopes and it seems mine takes twice as long exposure to get half the image.. Mine is not edge or faststar, Kasey

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A. Viegas
Pooh-Bah
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Reged: 03/05/12

Loc: New York City/ CT
Re: Which one will work best? *DELETED* [Re: David Pavlich]
      #6341244 - 01/28/14 03:05 PM

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


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