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Post by Deleted on Mar 25, 2016 3:20:48 GMT
Soon I will make a purchase. I will spend about $500 U.S. on a mount and about $400 U.S. on a scope. I like video astronomy, but my wife prefers visual so the setup will be used about 25% visual and 75% video. The mount will be an easy pick, but which scope will be more suited to this work? Is the perfect view from an R.C. and more back focus worth 2" aperture? Or am I completely misinformed in some way?
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Post by howie1 on Mar 26, 2016 0:03:56 GMT
What scopes do you currently have? What camera do you have?
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Post by Rick in NWArk on Mar 26, 2016 2:03:56 GMT
Hi Ward,
I've seen some nice live broadcast views through a 6"RC, for sure. It's a 12lb scope so you'll want a 25lb capacity mount. It's also F/9 so you'll want some focal reduction for shorter exposures (which helps if your mount is not perfectly aligned/tracking). You'll have a decent scale for a lot of objects with 1400mm focal length (but focal reduction will be needed for larger objects, tooO.
Don't skimp on your mount... I'm curious about what you're going with for $500. IOptron ZEQ25 is about $750 and Celestron's AVX is about the same. You might be able to grab one or the other used for a little over $500.
Remember that video cams will give you the results of approximately 3x the aperture.
I've also read about issues getting some cameras to come to focus with some Newtonians, so be careful there.
My best advice is, if you can, try to find someone who is using the scope, mount, and camera combo you want to buy and see some of their results before you click the purchase button.
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Post by davy on Mar 26, 2016 5:45:59 GMT
Hi ward,the scopes you mention are good choices,but as the guys have mentioned a bit more info needed,but here is my outake. The mount is the important part in the set up,,, a tracking mount or goto mount is a must have for video astronomy,,far to much work trying to do it manually. So given the scopes you mention you are looking at a skywatcher heq5 or above for weight wise and stability of scope and camera. Scope wise,visually more aperture is desirable so,8" Newtonian would be my choice for broad range of objects,planetary the r/c scope would be good. Video astronomy wise, a video camera makes any scope perform better and any scope that can achieve focus with a camera is workable,, But and a big but...it depends on what you want to see with your video set up,,,as no one scope will do all. If you have a scope with a slow f-number focal reduction is required, for most video astronomers they prefer short tube fast refractors,like the skywatcher ed80 style of scope,, but for yourself and mrs I would say a bigger aperture scope may be required...if you can tell us her preferred targets we might be able to give better advice to keep both of you happy :-)
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Post by Deleted on Mar 26, 2016 6:40:12 GMT
Thanks for the responses guys! In the past I have had a 12" dob and a Nexstar 6 based video astronomy system. I left the hobby due to the fact that I had so much setup to do just for a session. Recently I inevitably came back to video with a simplified setup. Currently I have 3 scopes...a 114 F3.9 newt, a f4.6 Ar102S2 refractor, and a 130mm F5 Meade newt. My current mount is an iOptron Cube with the counterweight. My cameras are the venerable SCB2000, the LN300, and a 1/2" Mintron. The best scope for video is actually the 114, but the coma is unavoidable no matter the collimation. The 130 is a bit much for the mount and the 102mm refractor has a lot of false color that hides fine detail. With the refractor...even with filters I cannot split Polaris. However it gives the best widefield views.
Rick: the mount I have in mind is the Orion Skyview with motor drives. Now I can get this with the 8" newt for cheap or splurge a little for the RC. If I want this can be upgraded to goto. Where I live is awesome sky for astronomy...the southwestern Arizona desert, but near the Mexican border there are no astronomy buffs who would have similar setups. In Mexico there are probably more astronomy hobbiests, but my town of Douglas is not an educated or scientifically oriented town. If I choose the RC am I back to the drawing board on coma since a focal reducer will be needed?
Davy: My wife likes planetary targets while I like deep sky. When the video comes out she goes in, or will start reading an eBook. She doesn't care about the depth of view...just the quality. I myself have pretty high standards as to what detail I should observe...maybe that is not good? The Hubble space telescope seems to have increased my expectations...even with a small scope...lol.
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Post by davy on Mar 26, 2016 10:25:40 GMT
Hi ward,think the soloution is two separate systems,think your wife would be happy with scopes you have already,you pointed out false colour ,i have the skywatcher st102 refractor and know what you mean,I would suggest you look along the line of a doublet refractor given the view and quality you want from video,the sammy does just under 10 sec and ln300 under 20 sec in sense up and will be good on refractor with a focal tube,I use the skywatcher ed80 with the skywatcher matched focal reducer/flatner and you will find that a good setup for video..and. second-hand may be in your budget.im in scotland,so rick would be better advice wise in usa prices. the mount is always going to be the week link I feel,,i have my set up with canon 600d on skywatcher allview and its on the bad side of its limit,clutch has to be rumped up tight not to slip,I also have eq3/2 pro its better due to counter weights.but heq5 is my next big buy,,,
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Post by Deleted on Mar 26, 2016 15:38:04 GMT
Well Davy, having 2 high end setups would be nice, but while my budget is not determined by what I earn...more like what I can buy without freaking my wife out...lol. My AR102 is a doublet, but has a very short focal length...star field views with it are very nice, but for high magnification work it isn't suitable. An ED doublet of about 6" would be awesome, but then I am in to serious money and serious weight. I am sort of leaning towards the RC idea currently because it is a planetary scope but will do deep sky with a focal reducer, and I happen to coincidentally have a 2" Meade .63 (I think) focal reducer from my old setup several years ago. It is worth noting that my old setup with computer...monitor...scope...cameras, and a ton of wires attracted the attention of the border patrol here on the AZ/Mexico border. They seemed to have me under not so subtle surveillance for quite a while...lol. For now I am just viewing on a screen...I may add a mini DVR unit sometime soon. Ultimately my goal is to have a medium size setup that only takes a few minutes to deploy. Right now it can be carried out in 2 hands with one trip. I really need to figure out some good cable management...
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Post by davy on Mar 26, 2016 17:13:42 GMT
Came to the right place then,lol. Your ar102 should do the business,in video it's not all about the scope aperture like astrophotography,our cameras do the work we go deeper into space with short scopes with a fast f number..in visual its all about gathering light to the eye,,,our cameras do away with that,so your scope being a doublet will be great,,fire on a focal reducer to give you more of a fov and make scope faster,,job done.
Davys portable array is what you need,big plastic toolbox,fit a 22ah 12v golf cart battery into it...cctv dvr with built in hard drive,,they come with mains to dc adapters now,,make a cable to battery and to camera,even the mount,I mounted a 15" computer monitor to inside top lid of tool box..you can split av feed to a usb grabber and have laptop control as well. All packed away in one tool box.
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Post by davy on Mar 26, 2016 17:16:31 GMT
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Post by Rick in NWArk on Mar 27, 2016 4:50:04 GMT
Ward,
For imagers, the conventional logic is the scope needs to be less than 50% of the stated mount capacity (20 lbs in the SkyView Pro case). But with Video, I think you can go up to 3/4 without problems. That would be 15 lbs and the 6" RC is 12 lbs, so you should be good to go if you choose that.
You can definitely do visual thru the RC -- the only drawback is like an SCT -- you have to get real low to see objects that are near the zenith.
For me, I'd be nervous about the Newt - I'd be worried that limited in-focus could rule out many video cameras. I'd read up on others' experiences using Newts and video cams. Or maybe some of the other guys can relay their experiences.
I wonder what the border patrol thought you were doing!?
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Post by Deleted on Mar 31, 2016 3:24:32 GMT
Nice portable array Davy. Very convenient especially when setting up at a remote site.
Ward, I started out with a Meade LXD-75, 6" Schmidt-Newtonian on a LDX-75 GEM. The rig (~ $750 new in 2011) was a pain for visual as the eyepiece was always at an inconvenient angle. Once I got into video astronomy, the camera doesn't care what angle it is at - much easier and safer for me. Low cost rigs are available that will work fine for video astronomy, just watch the f ration, under 5 is preferred. Even 6" optical tubes with a video camera and light pollution filter will provide nice views of many deep sky objects in suburban skies. I saw the Horsehead nebula from my backyard with my 6" OTA and a Mallincam Extreme 2.
I have a 10" RC on a G-11 GEM and my daughter has a double fork mounted Celestron Edge 11HD. She exclusively observes visually and I have to agree with Rick that visual observing near the zenith is tough on an alt-az mount. Of course if you use a diagonal and a video camera - its no problem with the fork mounted SCT or RC. I love my G-11, but I have to admit an alt-az is much easier to transport and setup. So for portable visual observing with occasional video work, I would definitely go alt-az with an 6 or 8" RC or SCT. Modern video cameras can capture very decent images in 30-45 sec or less so field rotation isn't much of an issue.
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Post by ChrisV on Mar 31, 2016 23:54:12 GMT
That portable array is really nice Davy. I got a
Back to this post - I'm struggling to see how an RC and SCT compare. Could someone explain the pros and cons of each - in terms I can understand. If they have similar focal lengths then is it down to differences in optics, or other stuff, or is it just all brand dependent ?
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Post by davy on Apr 1, 2016 7:24:18 GMT
Cant help myself,never had one :-)
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Post by howie1 on Apr 1, 2016 13:08:04 GMT
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Post by Dragon Man on Apr 1, 2016 13:51:29 GMT
Cant help myself,never had one :-) Me either. And I've only ever looked through an SCT once, and never seen through an RC. So I'm no help either Even the Meade SCT in our clubhouse is a fake. It was donated because it had a broken corrector plate so I replaced it with Perspex (Plexiglas) so we can show visitors the workings of a Cassegrain telescope
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Post by ChrisV on Apr 3, 2016 1:23:00 GMT
Thanks for the link Howie.
You've got to wonder about a 6" RC (or even and sct). It looks like 50% obstruction by the secondary, so you are getting down close to 4" ?
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Post by Dragon Man on Apr 3, 2016 11:55:10 GMT
Yes Chris. You only get a certain percentage of the light gathering with a Cassegrain/RC style telescope. In fact it's the same with all reflector telescopes. Anything that uses mirrors has a percentage of its light absorbed by the optical surfaces, and a large percentage of it's light path blocked by the secondary mirror.
"Refractors also have the highest light transmission – the percentage of the light gathered by the scope that actually reaches your eye. Refractors typically transmit 90% or more of the light they collect, compared with the 77% to 80% transmission of reflectors and 64% to 75% of catadioptrics. Then take into account the light blocked by a reflector or catadioptric's diagonal or secondary mirror, which can reach a hefty 15% to 20% additional light loss in some scopes".
That comes out to totals as high as a 47% loss of light for a Reflector and up to a 56% loss for a Catadioptric.
Reflectors using a 'Planetary Secondary Mirror' lose even more light as a percentage of light is not collected by the smaller secondary mirror. With a small Planetary Secondary mirror much of the light simply passes back past the secondary and out through the front of the scope back into space. Great for Planetary use, but poor for Deep Sky Observations.
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Post by howie1 on Apr 3, 2016 16:56:11 GMT
Atl, interested to hear if you have decided?
In case you haven't, and given your budget, have you thought of 2nd hand? In which case the following option will give your existing small sensor cam's the best chance as well as satisfy the vis stuff ... 2nd hand 8SE OTA only, 2nd hand Orion or Skywatcher GoTo GEM, 2nd hand 0.33 reducer. Sell your 0.63 reducer and all your other stuff to fund it.
Don on NSN regularly broadcasts with this OTA and 0.33 reducer and a GEM of some sort ... and gets great results. It is a combo which will satisfy your criteria of scope for the missus (higher power and good visually), and with the reducer good for both image scale and F ratio for your cameras you already have. Importantly, should come into your budget range second hand and with getting rid of some of your existing stuff.
You'll notice my thought are for GoTo as I think a non GoTo would be a real PITA with high focal length (for your missus) combined with your small sensor cams (which will behave like 5mm eyepieces yielding even more magnification).
Importantly, it's proven combo as per Don's broadcasts. The meade/celstron 0.33 reducer is no longer made but they do come up on forums for sale. Don's is from Optec so still being made though expensive. The Optec is camera specific and spacers are important but it works very well for him. His camera is also small sensor which also minimises vignetting with such strong reduction.
So yet more food for thought if you havent gone and bought yet.
cheers
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Post by Rick in NWArk on Apr 4, 2016 15:47:19 GMT
Thanks for the link Howie. You've got to wonder about a 6" RC (or even and sct). It looks like 50% obstruction by the secondary, so you are getting down close to 4" ? Buuuuut.... remember sensitive video astronomy cameras can effectively triple your aperture (or more)
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