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PostPosted: Tue Sep 30, 2008 9:49 pm 
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Now the days are getting shorter in the northern hemisphere, it's time for me to work on my winter photography plans. Specifically going astro! I've been interested since I was little, but rarely put it into practice with observing by anything other than naked eye. And my few attempts with normal camera lenses have been interesting but I do want to move up a level.

Telescope wise, I have no idea what I need/want. I do want a motorised equatorial mount. Computerised auto-alignment would be a big plus. I have read through other previous posts here but I think I still need some pointers.

Subjects - whatever I can see I guess. For starters, the moon in detail and planets. At least surface detail on Jupiter, resolving GRS would be really nice.

I do live in a city so light pollution is a bit of a problem. I don't know how far out I need to go to get much clearer skies. Weather allowing of course. I wonder if a low pressure sodium lighting filter helps much? Only found one so far, almost wondering if they really exist...

Focal length/magnification/etc - no idea. With a 300mm camera lens, Jupiter's disc is only a tiny handful of pixels wide currently. So I'm guessing "as much as possible" might not be too bad? Providing it's usable, I'm guessing something around 3000mm will be fine.

T-mount... here I'm a little confused. I have what's sold as a T-mount adapter. One side fits on camera. One side has another screw thread for whatever else. It is my understanding that on here you screw the appropriate adapter for the telescope eyepiece. However, in Gordon's video, it's shown as a single item. I can imagine the two parts being made as one, but what is the correct terminology for the mount? I've also heard it called T2-mount. Ooh, reading some more, I now also see it called T-ring. edit: suddenly it becomes clearer. I got the ring, just need the other bit to join to scope.

Further to that, on a quick search I see you can either put the camera at the prime focus of the scope directly, or leave the eyepiece in place, with or without lens. What is the “short version” impact of leaving the eyepiece in? I assume it gives effectively a focal length increase at the cost of light? Likewise digiscoping?

My budget is open. I don't want to go crazy, but at the same time I do want something that will not leave me looking to replace sooner than later. Over £500 for the system is not a problem, but the further up you go, I'll need more convincing that it's worth it.

For an example of something that looks interesting, how about the Celestron C8-NGT? Seems to go for around £650 in the UK. 8 inch (203mm) aperture, 1000mm focal length, f/4.9. My initial feeling is the focal length is a bit short so if I got this, I will need to use some techniques to effectively extend it. Their spec does claim a photographic resolution of 400 lines/mm, but I don't know how that compares to typical DSLR sensor resolution and therefore estimate the useful focal length that could be extracted.

Random thought. The use will be mainly for astrophotography... but at 1000mm, I'm wondering will it double as a rather bulky daytime telephoto too? Obviously at 30kg I'm not gonna hand hold it :D

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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
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PostPosted: Fri Oct 03, 2008 11:49 am 
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No one got scope advice around here?

I've just been pointed in the direction of another similar model by a seller: link. Need to read up on it more myself.

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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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PostPosted: Fri Oct 03, 2008 1:40 pm 
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Hi popo,

My apologies but I read your initial post and it contained so many questions I gave up. :oops:

I'm short of time again today so I'll just point you to a store that I've used in the past.
It's worth 'phoning after having had a browse through the web-site. Ninian is knowledgeable and very helpful. OK, he runs a business so he'll try and sell you some kit but if you are nice to him he'll also sometimes offer a small discount, especially if the currency rates are going in the right direction. Good luck.

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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PostPosted: Fri Oct 03, 2008 5:18 pm 
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Fair enough :) It's hard to get a lot of info into a short amount of writing. Next time I'll have to post one question to start with, and drip feed the rest once you've bitten :D I've managed to more or less answer most parts except for the most important one, the scope.

The ultra short version of what I want to get is:
A "decent" scope with motorised equatorial mount, computer controllable
Some way of connecting a DSLR (T-mount ring+tube=sorted)
Light pollution filter (found some now!)
Battery pack as needed for powering mount (no problem)

So that still leaves the scope. It looks like Newtonian designs give the most light at moderate focal lengths, at the expense of relatively large physical size and weight to move around. Debating if it's worth going to one of the Cassegrain types. Smaller physical size, longer focal length at cost of higher f-number and price.

So I'll have to dig deeper at the link and see what I come up with :)

_________________
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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PostPosted: Sat Oct 04, 2008 12:13 pm 
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If you want to do astrophotography with a DSLR you need a scope with a big enough focal plane diameter to cover the chip. Just about the only thing at non-astronomical (sorry) prices is the Takahashi FSQ-106, and that'll still set you back several grand. True Technology sell these.
Greg

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Nexstar 11 GPS, 2 x Sky 90, M25C, MaximDL, Photshop CS3, Noel Carboni's Photoshop actions, 7 foot Pulsar fibreglass dome, Canon 40D, 100mm macro lens, 28-200mm zoom lens, 17-55mm f#2.8 zoom lens, 100-400mm zoom lens, 1.4x converter, 2x converter.
http://www.newforestobservatory.com/
http://www.flickr.com/photos/12801949@N02/


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PostPosted: Sat Oct 04, 2008 12:20 pm 
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Ooh, that has never come up in my research before. I assumed that since everyone sold SLR adapters for a long time, there was no problem even at 35mm format. Got any references to this potential problem?

_________________
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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PostPosted: Sat Oct 04, 2008 7:13 pm 
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No reference - only years of experience. As Bob says - it's probably worth giving Ninian a call (or visit).
Greg

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Nexstar 11 GPS, 2 x Sky 90, M25C, MaximDL, Photshop CS3, Noel Carboni's Photoshop actions, 7 foot Pulsar fibreglass dome, Canon 40D, 100mm macro lens, 28-200mm zoom lens, 17-55mm f#2.8 zoom lens, 100-400mm zoom lens, 1.4x converter, 2x converter.
http://www.newforestobservatory.com/
http://www.flickr.com/photos/12801949@N02/


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PostPosted: Sat Oct 04, 2008 8:18 pm 
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Still learning :) Just found out an altazimuth mount on a wedge should remove the need for an equatorial mount, which significantly widens the choices at the lower end and makes things a lot cheaper!

_________________
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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PostPosted: Sat Oct 04, 2008 10:14 pm 
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An altazimuth mount on a wedge IS an equatorial mount - a poor one. You are putting a tuning fork over at a funny angle that the scope (plus altazimuth mount) was not really designed to operate at. The whole thing is much more sensitive to vibration than bolting the altazimuth mount straight down onto a pier or tripod with the "tuning forks" vertical (alt-az mode).
Greg

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Nexstar 11 GPS, 2 x Sky 90, M25C, MaximDL, Photshop CS3, Noel Carboni's Photoshop actions, 7 foot Pulsar fibreglass dome, Canon 40D, 100mm macro lens, 28-200mm zoom lens, 17-55mm f#2.8 zoom lens, 100-400mm zoom lens, 1.4x converter, 2x converter.
http://www.newforestobservatory.com/
http://www.flickr.com/photos/12801949@N02/


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PostPosted: Sat Oct 04, 2008 10:42 pm 
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That makes sense... in my limited observation I took an equatorial mount to be specifically one of those with the counterweights etc. as opposed to be a general type.

From my perspective, I have no idea how seriously I'm going to get into this. Like photography in general, there's always something "better" and more expensive, but I need to find where the line is for realistic value.

For example, this Celestron NexStar 4 SE seems to be a the lowest cost option to tick my requirement boxes. The wedge is built in to the bundled tripod, and they even have dedicated features for astrophotography.

Edit: thinking more, I wonder how small this is? How far could you go with photography lenses?

_________________
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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PostPosted: Tue Oct 07, 2008 12:34 pm 
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I've gone and ordered the NexStar 4 SE along with the related camera adapter. I know it's small, but I figure it'll be good enough for starting out and getting some practice in. I can always go much bigger later if my interest keeps up. With a little luck I'll get it this week, and then can only wish for a clear sky to try it with.

_________________
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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PostPosted: Tue Oct 07, 2008 1:16 pm 
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Hi popo,

Congratulations on your choice. Here's wishing you "Dark Skies". 8)

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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PostPosted: Tue Oct 07, 2008 4:41 pm 
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Got confirmation it has been dispatched and I will hopefully get it tomorrow :D And looking out of my window right now, I can see blue! So there's a chance I might even get a try tomorrow night.

Forgot to say earlier as I was in a rush posting from work, but thanks for the advice in this thread. I didn't make use of the contacts as from their sites, that's at a level far beyond where I'm looking for now. But as and when the upgrade itch starts to kick in, I'll be back :D

_________________
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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PostPosted: Tue Oct 07, 2008 4:58 pm 
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Hope to see some shots of you soon Popo, congrats with the choice!
Which camera will you use to take shots of the moon?

- Bjorn -

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PostPosted: Tue Oct 07, 2008 5:13 pm 
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Of me or from me? :D Well, there is this month's assignment...

For now I can only use the A350 as I don't have a T-ring for the Olympus yet. Speaking of which, I need to go to ebay now...

_________________
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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