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 Post subject: Celestron Nexstar 4SE
PostPosted: Sat Nov 22, 2008 6:47 pm 
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Scope tube shown mounted on a photographic tripod.

Yes, this is a telescope. But at the end of the day it is a lens like any other and you can attach a camera to it. It is intended for sky observation, but can also be used terrestrially within some considerations.

The kit

This comes as not just a scope, but pretty much an all in one starter kit for optical observation. Included in the box you get a hefty tripod and motorised mount, so once set up it can track objects as they move across the sky. More on that later.

The scope itself is a Maksutov-Cassegrain catadioptric design. What that means in English is it has lens elements and mirrors in a certain configuration. This particular one gives a fairly sealed unit so maintenance is minimal. Size is also comparatively small for the focal length.

The specification in photographic terms is a focal length of 1325mm and aperture is fixed at f/13. There is a 20 turn knob on the back which moves the main mirror to focus the image.

This scope has two optical ports where you can connect to. A movable mirror at the back of the unit either passes the light out the back, or reflects it through 90 degrees to the side. The side port takes a standard 1.25" eyepiece, and the supplied 25mm one gives an optical magnification of about 53x. Due to the optics involved, the image in the eyepiece is vertically correct but mirrored left-right.

To mount a camera, you can use the dedicated port at the back. An optional adapter is required to connect here, and a T-ring to suit the camera mount. This time, the image is normally aligned as viewed by the camera.

Alternatively, using an optional eyepiece adapter you can connect the camera to the eyepiece port but I think this would result in a mirrored upside down image. The benefit of using the eyepiece adapter is that it will also take standard eyepiece filters which the rear port adapter does not.

Image
The finder is on the upper left. Eyepiece port covered to left. Upper knob on back sets focus. Lower knob flips the internal mirror to direct the light to either the eyepiece or camera port.

Mounts

You can use the scope with a regular photographic tripod. The mount on the scope includes two receptacles which take the standard tripod thread. The only caution I would give here is the scope is relatively heavy, so the tripod head would need to be able to take this. I first tried with a cheap tripod and it would keep slipping however hard I tried to tighten it. Also, with the long focal length, even small vibrations are more easily detectable. So it does need to be sturdy.

Using the supplied mount has its advantages and disadvantages. For starters it is heavy. This might help keep it stable, but you don't want to move it too much. The kit comes with a bubble level to help you flatten it, but you can't leave it fixed on the tripod so I haven't bothered with it.

On top of the tripod goes the motorised mount. This has a wedge which is needed if you want to attempt very long exposures. This aligns one of the degrees of motion so that only a simple sideways movement will track an object. Without this, two degrees of motion are needed to keep an object centered but it will appear to rotate.

The motorised mount has a computer control and various alignment modes. Basically once aligned, it can direct you to any object within view. I haven't tried this mode yet, and have only used the mount manually. Without alignment, you can simply move it up/down and left/right with the control pad.

The motor needs power and there are two main options here. The unit can take 8 AA batteries, or an external DC supply. The batteries last longer than I thought. Then again, the motors don't run that often, and the other main drain is the backlight of the handset controller.

The controller also has many connection options, including the possibility of remote computer control.

While on the mount, I'll also quickly mention the alignment. There is a red dot type finder on the side of the scope. This projects a red dot within its display which appears constant in position even if you move around. So once set up and aligned, you can use this to help you target the scope.

Other practical considerations

Due to the long focal length, you will need to keep any vibration down to a minimum during use. For photography, a remote release is strongly suggested unless you want to wait for the timer on every shot.

Even though the focus knob is 20 turns end to end, the difference between in focus and out of focus is still only a small rotation. Maybe equivalent to 1 hour on a clock. If you have any live view zoom function it will come in very useful here.

Ever heard of diffraction softening? You will now. In practice this scope is diffraction limited with any modern DSLR. What this means is that it doesn't matter how good the sensor is, as the optics are limiting the final image quality giving a soft look. This is not due to any fault in the scope design or build, but those pesky laws of physics getting in the way again. The only way around it is to get a bigger aperture scope.

Image
100% crop. 1/200s, ISO400 on 50D. No PP.

You can use this scope generally in daytime too. The claimed minimum focus distance is 20 feet which is reasonable. Tracking fast moving objects wont be fun as the field of view is quite small plus you have the sensitive manual focus. Stationary objects are much easier. At f/13, it isn't particularly bright so fast shutter speeds will be a challenge.

It may not be visible to the naked eye, but this has enough effective magnification to show up air turbulence causing distortions on images.

Image
100% crop. 1/15s, ISO400 on 50D. No PP. Subject was maybe 1km away.

Due to the mirror lens design, the bokeh is donut shaped.

End

I'm sure I've forgotten some things so I may update this later.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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 Post subject:
PostPosted: Sat Nov 22, 2008 7:14 pm 
Very nice. So with this kit, you can look at stars and presumably your neighbour getting in/out of the shower? ;)


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 Post subject:
PostPosted: Sun Nov 23, 2008 11:57 am 
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Nice review Popo! Looks impressive mounted on the 50D! And I'm sure you'll be able to take some nice shots with it!

- Bjorn -

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 Post subject:
PostPosted: Sun Nov 23, 2008 12:43 pm 
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I think you'll find the 50D is mounted to it, not the other way around XD Given the diffraction limiting I'm now looking at low cost ways to get more resolution...

Actually I'll write more on that later, but the sun is out for a change so I'm going out to make use of it while it's there!

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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 Post subject:
PostPosted: Sun Nov 23, 2008 12:46 pm 
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Hi popo,

Great review - thanks for sharing.

Do you think you might try a focal reducer to get the focal-number down to the diffraction limiting value for your 50D? It won't get you any additional sharpness, of course, but you will get a slightly brighter image (good for extended objects like planets and nebulosity) and, aberrations permitting, you should also get a wider field of view.

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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 Post subject:
PostPosted: Sun Nov 23, 2008 1:04 pm 
Nice review there.

Just out of curiosity, exactly what tripod is that??


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 Post subject:
PostPosted: Sun Nov 23, 2008 3:31 pm 
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Bob, last time I looked I just got confused and forgot about it. I just had a quick look again, and think maybe I'll risk buy a cheap one to try. I don't have exact figures, but the 50D would start entering diffraction limiting somewhere between f/5.6 and f/8. So a 0.5x or 0.6x reducer would put it neatly into that range giving the new spec of 660mm f/6.5 or 800mm f/7.8 respectively.

I do want to try deep sky, although I'm not sure if my location will be light pollution limited. I do have a light pollution filter but I don't know if it will be enough. Planet wise I've recently bought a 2x barlow as brightness isn't the problem, it's size. Jupiter is getting too low too early for me, but Saturn should be getting better.

Longer term I think the affordable way to go wide is to get a Newtonian of some sort. Up to 8 inch seems very affordable. The reason I didn't before was the size of one of these things...

Gregory, You can't really see the tripod in the pics, but it's a Manfrotto 190DB. What you can see is the head, which is a 390RC2. I don't find them that great but they were selling cheap at a local shop at the time.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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 Post subject:
PostPosted: Mon Nov 24, 2008 5:25 am 
Great review Popo, nice gear!

Do the pictures show the scope mounted on the tripod with the motorised mount cos it really doesn't look that big. I always imagined them to be huge pieces of equipment.


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 Post subject:
PostPosted: Mon Nov 24, 2008 7:50 am 
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As said before the pics show it on my photo tripod which I was using earlier to try out some new accessories I got for it. The motorised mount is not shown. What I forgot to do was link to the manufacturer's page here which has more on it.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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 Post subject:
PostPosted: Mon Nov 24, 2008 9:17 am 
Ah I missed that, sorry! Thanks Popo, now it's even bigger than I thought! :D


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 Post subject:
PostPosted: Mon Nov 24, 2008 9:45 pm 
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Time for some practical usage experience. I tried the scope again tonight as it was clear earlier. And now I know the sky a little bit better. Still lots of it left to explore.

First I had a quick go at Jupiter again while on the tripod. It was low in the sky but I managed to catch it through a tree. The standard eyepiece and a 2x barlow gave a combined magnification of about 100x. Jupiter was still a blurry blob with no noticeable features. I saw 3 moons easily, although later looking up a the motions I should have caught the 4th too. Maybe another time.

Next up I thought I'd give the computerised mount another go. I manually pointed it at some random bright specks, which then turned into somewhat brighter specks. Not terribly interesting, so I thought I'd try the auto alignment feature. I tried this before unsuccessfully. This time I tried to be more accurate, and it worked! Once done I could hear a quiet whirring which I assume is the tracking working automatically. So what to see? From a sky map earlier, I thought I'd try the Andromeda galaxy which should be easily in my field of view. I entered it into the handset and was met by the bang of a diagonal meeting the mount as it pointed the scope upwards. They don't give you much clearance at the back end. Taking that off and trying again, it worked, but I saw nothing there. I was going to do a re-align in case that knocked it out, but it was too late. Cloud had moved in and I had to call it an evening.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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 Post subject: Nice work
PostPosted: Fri Dec 19, 2008 7:45 pm 
Hi Popo...


Very nice of you to give such detailed info..

I hv decided to upgrade to a DSLR(Nikon D80/D90)

I was very interested about the idea of using a telescope for both astronomy & terrestrial photography on a DSLR...

This was pretty much what i was looking for.... someone who has tried it...

By the way, how much did the telescope cost you..???

:)


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 Post subject:
PostPosted: Fri Dec 19, 2008 8:15 pm 
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At the time I think it was £340 with computerised mount. But with the economic situation and exchange rate fluctuations, it could be anything especially if you convert around different currencies. I've seen the 6 inch version go for similar amounts tube only, no mount.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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 Post subject:
PostPosted: Sun Jun 21, 2009 7:13 pm 
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Just for fun, I thought I'd see what the maximum magnification of the scope was... note this is camera lens style magnification, not scope style.

Camera was connected using an eyepiece adapter onto an erecting prism on the back. I wasn't at minimum focus distance but couldn't have been far off.

Image

About 38mm across. That's about 1:1.7 or 0.6x. I didn't measure the actual distance but estimate it somewhat over 3m.

Problems with this? Stupidly sensitive to vibrations due to long focal length, and fixed aperture of f/13 means you can't increase DoF nor make it brighter. This is more a concept test than something useful.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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 Post subject:
PostPosted: Wed Apr 07, 2010 3:53 pm 
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Uhm, how much did you pay for the motorised mount+scope?

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Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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