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Choosing a scope


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I am trying to pick out a new scope to do observing and AP.  I found two that I think might be good.  First is a Orion  10" Atlas EQ goto (http://www.telescope.com/mobileProduct/Telescopes/Reflector-Telescopes/Reflector-Telescopes-with-GoTo-Mounts/Orion-Atlas-10-EQ-G-GoTo-Reflector-Telescope/pc/1/c/11/sc/343/24735.uts),  Second is the Celestron Advanced VX 9.25" (http://www.celestron.com/browse-shop/astronomy/telescopes/advanced-vx-925-schmidt-cassegrain-telescope).  Also if anyone has any other suggestions for other scopes please let me know.  Thanks! 

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Hi there. Before you make a decision, please read this book:

https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

It'll give you a good idea of what you need. A large aperture is best for visual but isn't strictly necessary for AP. If you're imaging nebulae, which can be very large, then a small-aperture refractor is good. I use my large-ish Newt for galaxies, planets and other small objects. It's not as simple as one size fits all! The 130mm or 150mm Skywatcher Newts are pretty good for imaging I've been told.

Also, if you want long exposures, you will need a mount that can be autoguided. In fact the mount is the most important part. Some excellent images have been taken with unguided mounts, but guiding is best.

Alexxx

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There are two entirely different kinds of AP, each with its own set of requirements.

Lunar and planetary imaging usually involves relatively inexpensive fast frame (video type) cameras which shoot a burst of images which are then treated as stills, the best being selected and combined. A tracking mount makes this much easier and a tracking equatorial, rather than Alt Az, makes it easier still but motorized alt az will do. When the images are stacked together the software will align them so ultra-precise tracking is not essential. The objects are small so you need a long focal length to give them decent image scale and they are bright so you do not need a fast focal ratio.

Deep sky imaging uses long exposures so very, very precise tracking is the first, absolutely the first, priority. We mostly use autoguided German equatorial mounts though other designs exist. The popularity of the German Equatorial is not without reason but it is not imperative. It is certainly my own choice.

DS targets are often very large so a short focal length is needed to fit them onto the chip. A reasonably fast F ratio, around F5 or F6, makes capture tolerably fast. Faster F ratios come at a 'real world' price of being tricky and fickle and slower F ratios are... painfully slow.

Longer focal lengths require ever more accurate tracking. It is much, much easier to start DS imaging at short focal lengths.

The pixel size of your camera should be matched, up to a point, with the focal length of your scope. If you put a small pixel DSLR in a long focal length telescope you will not be able to resolve the details which the numbers alone would suggest. If you intend to start with a DSLR I would suggest a focal length of less than a metre.

You do not need aperture for DS imaging. Some of the best deep sky images are taken with 80mm telescopes.

And, as Alex said, don't spend till you've read Steve's book!

Olly

Edited by ollypenrice
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I would suggest that you look for a better mount. At least a eq5 with maybe a skywatcher 130pds ota. You can buy both second hand meaning that you will not loose too much should you change your mind. You can buy allot better for that price and have spare change for any extras. But buy the book first especially if you going to buy brand new kit.

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7 hours ago, Sjwoodwalker said:

Sorry...  I live in Texas, USA. Out of curiosity,  why is that mount not a good choice? 

There is absolutely nothing wrong with that mount so far as I know, it is a Skywatcher HEQ5 Pro with a paint job and an Orion badge so it is indeed better than an EQ5.  This forum has predominantly European members so people tend to talk in terms of Skywatcher gear.

The ED80 is a great imaging scope, just be aware that it isn't flat field so to get the most out of it you will need a field flattener.

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I know that refractors and reflectors work differently but I have a 114mm newt and I got some decent photos from it but when I was looking for the Orion Nebula it looked like a fingerprint mark on the lens.  I couldn't see anything until I took some long exposure pics.  Same thing with the Andromeda Galaxy.  Will it be the same with the 80mm refractor? I appreciate all the help y'all are providing. Here is Orion Nebula that I snapped. 

FB_IMG_1473161682084.jpg

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This is little old me explaining focal length in its simplest form. Imagine camera lenses. A wide-angle lens will be short and stubby, e.g. 50mm FL. It has a wide field of view (FOV). Then imagine a very long lens, say 300mm FL, which gets in close to an object and has a small FOV. If you apply that to a telescope, the shorter the FL the wider the FOV and vice versa.

I don't fully understand what 'fast' and 'slow' mean for scopes, but a fast scope gathers more light than a slow scope and is best for imaging. To get this you divide the FL by the aperture. For example my Newt has a 1000mm FL and 200mm diameter so it's 'speed', or focal ratio, is F5. That's quite fast so gathers quite a lot of light and is good for faint objects. My little Megrez frac has a 432mm FL and 72mm aperture so it has an F ratio of F6. Still reasonably fast (using a focal reducer increases the speed). Then you have something like a Schmidt-Cassegrain which might have a 2000mm FL and, say, 200mm aperture to give F10. These are slow and therefore don't gather light so well but also the FOV is small so they're great for planets.

Someone will be along with something more scientific!

Alexxx

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If you have a telescope you can transport to  a dark site you will see more. The human eye cannot see as much as a camera. Whilst a large aperture will see more it is a trade off if it is too big and never gets used you'll then see nothing.  

Choosing one piece of equipment to do visual and imaging is going to be a compromise somewhere. 

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If you've got some spare cash, you could get a cheap, second-hand Dobsonian for visual, poss a 200mm aperture for about £180+ or dollar equivalent? They're on a fork mount so store in a small area, but can be heavy. Some can come with go-to but are more expensive. I don't do visual at all now I've got the AP bug!

Edited by Astrosurf
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