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Reflector or Mak-Cass for cameras?


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Hi all,

Photographing the recent ISS Transit in front of the moon with just my camera (A Canon 7D + 70-200IS + 2X Extender, image attached to inspire me further) reawakened a hunger that I've had since childhood for stargazing and made me want to get more in to astrophotography so I've started looking at telescopes both to stargaze and maybe photograph some of what I'm seeing. My research has already told me I'm going to need a T-Ring for my camera, as well as something capable of tracking the object I'm looking at so I know (guess?) I'll need something motorized which is fine because I'd already planned on going that way anyway.

I've currently narrowed my search down to 2 scopes. Comparable in price, and from the same manufacturer (SkyWatcher) so I'm really left looking at the features and what makes each scope different. 

SkyWatcher 127/1500 EQ3 Maksutov Cassegrain vs SkyWatcher Star Discovery 150/750 Reflector 

So I'm hoping I can get some help differentiating between the 2 and make sure I'm assessing them correctly. Based on what I'm reading I've summarised them as follows.

The 127/1500 Mak-Cass has a smaller aperture (5"?) but a longer focal distance (1500mm) is going to give me an f/ratio of 11 if I'm working things out right, which means I might get sharper images at higher magnification but my catalogue of available objects might be less.

The 150/750 Reflector has a larger aperture (6"?) but a shorter focal distance (750mm) so I'm going to get an f/ratio of 5; I'll be able to see more distant objects but they might not be as sharp due to the faster lens.

At this stage I'm probably more interested in planetary viewing (the thought of snapping a photo of Saturn or Jupiter gives me shivers) but I expect I'll want to graduate to other objects fairly quickly. All things being equal, what would you recommend? Thanks in advance for your input. :)

-Bob

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Always go for the larger aperture... The shorter focal length can be compensated for and extended with Barlow lenses or shorter focal length eyepieces... But I recommend to get the largest aperture you're willing to spend money on.

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For planetary imaging you will want a long focal length scope but that will not be easy for DSOs where a short focal length will be much easier. So, ideally, you will need two scopes (at least). Mount is crucial for imaging and should be your first consideration.

Peter

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Reality is you should go for the reflector, the Mak/SCT would be OK for Saturn and Jupiter but not the DSO stuff.

Do not get mixed up that a good visual scope will be a good AP scope, the requirements differ.

At extremes a good AP scope is the William Optics Star 71, a good visual is a 10" reflector - note the difference.

Oddly for planets the Mak/SCT is likely better, you drop a webcam in, take a video and in some software select the best 30% or 20% and stack those frames. So actually very easy. The "problem" is that you have Saturn and Jupiter and occasionally Mars. The Mak/SCT's are too slow for DSO imaging and long exposures.

The more flexible and useful scope is the reflector, however for a 150 you are looking at a mount like the HEQ5 or iOptron CEM25 as a minimum, and even then there are a bit close. THe physical size of the 150 will make it prone to any breeze. One serious option is a 150 for visual and get a smaller scope, probably refractor for AP later.

Also the DSLR may not get a focussed image on the sensor as the standard 150 is intended for visual, you will have to consider the 150PDS for imaging, the mirror and focuser are slightly differently positioned. This then means you could need a short extension tube for visual to get the eyepiece correctly places,

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Welcome to SGL

I have a Mak 127 and it is a very good wee scope. Great for the Moon and planets and take a reasonable magnification at 250x in the best conditions, more often used at 200x. The contrast is good and I have had some very good views from it. Having a long focal length it is fairly forgiving on eye pieces. The Moon is stunning thorough the little Mak.

It is very light and I treat it as a grab and go on its goto mount. Where it falls over is with the dimmer larger DSO's. They are often larger than the Moon and have a lower surface brightness. So an F5 reflector with a 150mm apeture would have a wider field of view and grab the dimmer bigger DSO. At F5 eye pieces need to be considered.

Skywatcher have good scopes. But what lets them down is the accesories supplied. The stock 20mm and 10mm ep's are not up to much, ditto the barlow and diagonal supplied with the 127 mak. Those items would be the first target for an upgrade. I have a 12'' SW dob and the stock ep's and barlow are the same.....not so good but ok for a starter.

From reviews and seeing folks reports on SGL one of the best tubes in the Skywatcher range seems to be the 8'' dob or the 8'' Newtonian on an EQ mount.

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I don't think the Skywatcher Sky Discovery is suitable for astrophotography. The instructions do mention using it with a camera (for terrestrial photography) but only if you remove the scope and attach the camera directly to the mount. The focuser on the scope is its weak point and only 1.25" when you want 2" and the mount is alt/az when you need an eq mount. If you want a Skywatcher Newtonian for imaging then you need something from the Explorer -DS line.

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Hi all, 

Thanks very much for your input. I've definitely got a lot to learn and consider! 

I think at this stage I'm going to go with the Reflector, but I've asked the shop where I'm making enquiries if they can recommend something with an 8" aperture instead, and I've put the EQ5Pro mount on my wishlist for down the track. I think getting out there and enjoying things visually will be a good enough start (the best scope is the one you use, right?) and then I can pursue the photography passions later on down the track as I add more equipment.

I've suffered from Gear Acquisition Syndrome with my camera hobby, I suspect I'm going to get a severe bout of G.A.S. with telescopes too. :D

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Ok, maybe I'm going a little crazy with G.A.S. already but if I increase my budget I can get the HEQ5 GoTo mount, and combine it with a Saxon 200mm x 1000mm Reflector. I'll get a larger aperture and a better mount.... nothing wrong with the idea in theory?

I can combine mounts / scopes from different brands, right? They all use a universal mounting system? And for eyepieces, that's standard as well, right, just grab the ones I "need" and go?

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So I see a lot of the suggestions have to do with the mount and wind stability. Would I be better off getting a Dobsonian instead? My only concern getting a Dobsonian is that I can't change the OTA at a later time. Other than that, they seem to be a pretty solid choice?

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If you want to get into astrophotography, you could do a lot worse than buying this book before parting with your hard-won readies: http://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

If visual is your thing, then the best bank for the buck comes from a Dob. I got a second hand 10" with eyepieces, a Telrad and other goodies thrown in for just over 200 quid of a well known auction site last year. I had to do a 300 mile round trip to pick it up, but it was worth it! :)

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Ok, maybe I'm going a little crazy with G.A.S. already but if I increase my budget I can get the HEQ5 GoTo mount, and combine it with a Saxon 200mm x 1000mm Reflector. I'll get a larger aperture and a better mount.... nothing wrong with the idea in theory?

I can combine mounts / scopes from different brands, right? They all use a universal mounting system? And for eyepieces, that's standard as well, right, just grab the ones I "need" and go?

The HEQ5 is a great idea, if you want to image though it will be much easier to start out with a small short focal length refractor like an ED80.

It may not actually be possible to bring a DSLR to focus in the Newtonian you mention, that type of scope is notorious for limited back focus of the are not designed with imaging in mind.

There is no problem mixing mounts and scopes from different manufacturers.

I think you have a bit of a misunderstanding on what the f ratio of he scope means for astro imaging, it is somewhat different to normal photography. In normal photography you get a better depth of field with higher f ratio, with astro imaging this is not the case as all the light is coming into the scope parallel there is no foreground.

For Astro imaging a high f ratio is considered a bad thing, high f numbers are called 'slow' and will require much longer exposure lengths than low f numbers which are called fast.

You should aim for f5-7 to start out with, slower than f7 will require really long exposure but faster than f5 will start to be difficult to focus and also exacerbate any distortions in the optics.

/Dan

Sent from my iPad using Tapatalk

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