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PostPosted: Sun Oct 30, 2011 2:59 pm 
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Hi groovieknave,

For general photography I have a Gitzo GT1541T. I reviewed it here (user review) and Gordon shared his own experiences with it here.

For most of this thread I used a very basic motor-driven equatorial mount on a dedicated tripod. Good enough for unguided astrophotography using a DSLR and fairly wide fields of view for exposures of three or four minutes at least. How long you can go before the stars start to trail depends very much on how well you can align the polar axis and, of course, on the focal length used. These days computerised mounts are a lot cheaper so I might look at something like the Celestron CG-5GT if the budget permitted. I can't recommend it personally but it seems to tick most boxes for DSLR type astrophotography.

My current setup is shown above. It's an ASA DDM60 PRO. This a big budget item and quite unusual technology for the amateur as it has torque motors and high resolution encoders (think 1/100th of a second of arc resolution). The beauty of such kit is zero backlash and, after proper training, an ability to track to sub arc second accuracy over exposures as long as 15 minutes or more unguided. So far I've only been able to do the setup visually with a 480 mm focal length refractor but that was good enough to achieve a 4 pixel tracking accuracy over a period of two hours using an 85 mm focal length lens on my 5D Mark II.

I am looking forward to doing a full setup with a new 980 mm focal length refractor in conjunction with an astronomical CCD later this year. If I am successful then the setup automatically calibrates for tube flexure and atmospheric refraction as well as minor polar misalignment, hence the expected tracking accuracy. That's not to say that I couldn't use an autoguider with the DDM60, just that I shouldn't need to with good setup and a solid permanent pier.

Hope that helps.

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: Sun Oct 30, 2011 3:39 pm 
Cool, I did have a horrible Orion EQ2 mount that died on me so many times when I bought it that I just had to return it. It was only 189$ and I couldn't get any pictures out of it. I was better off with my 30$ tripod. I will have a look at the CG5 mount. But I didn't like the whole polar alignment thing. Maybe just something I would need to practice. I don't plan on putting a telescope on one. I like my Dobsonian too much to bother with anything else.

I'm really just excited to get long enough exposures of the sky at all. I'd love to do 3 minutes at least. Half a minute is fun, but it isn't bringing out the sky how I'd like it too.

I've got a budget of 500-600$ I've been searching around and everyone has very simple things to say about them rather than giving me much information. I do know that it needs to be stable, but it will only be holding my DSLR camera and nothing else. I'm just not sure what people use these days.

Thanks for the info though! I appreciate it!


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PostPosted: Sun Oct 30, 2011 11:35 pm 
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You should look into Astrotrac:
http://www.astrotrac.com/Default.aspx?p=tt320x-ag

As simple and cheap as it gets ;)

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PostPosted: Tue Nov 01, 2011 10:16 am 
Nice! I think the astrotrac is exactly what I am looking for. Now I just need to save the money and buy the travel package...


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PostPosted: Tue Nov 01, 2011 12:33 pm 
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That reminds me... I need to finish writing up my review of the astrotrac some day!

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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: Tue Nov 15, 2011 11:43 pm 
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Hi folks,

Cor, what a frustrating evening! I finally got the modified lens adaptor back last Saturday allowing me to fit a medium format 165mm focal length f/2.8 Pentax lens in front of my new CCD camera. Tonight was clear, in a rather hazy way, so I started manually focussing via a series of 10 second exposures through a green filter. Just as I was closing in on a good setting the clouds rolled in. About an hour later the stars were back but sky transparency was pretty rubbish but at least I was able to complete focussing. Now for the serious imaging, thought I. Wrong!!! :lol:

I had MaximDL controlling the telescope mount as well as the camera and filter wheel and I had a preprogrammed sequence of shots set up. The first was one of an intended three 1000 second exposures through the Hα filter but at the end of that exposure when it downloaded two things happened. First I got a nasty shock because the stars were horribly bloated and then MaximDL gave me a rude message about my not having told it what the focal length of the "telescope" was and it summarily aborted the sequence. Doh, it might have told me it needed more information earlier and it was doubly frustrating as it already knew the field of view of the camera, that information having been entered elsewhere. It uses the information to command a small dither (a few pixels) between shots so that CCD defects may more easily be detected and removed during subsequent processing. For the record I had hoped, in addition to three 1000 second Hα shots and the same number of "darks" to take three sets of 200 second "lights" through each of my red, green and blue filters and, of course, the matching darks to go with them.

The star bloat and lack of fine detail in the emission nebula was simple enough to explain - the lens had dewed up. :oops: A Kendrick 2 inch dew heater (0.3 amp current draw) is now on order. Crazy game as the camera sucks up to 5 amps to power its Peltier cooler but the heat produced gets wasted rather than being directed towards the other end of the imaging train to keep the optics dew free. Hmm, Heath-Robinson would be reaching for lengths of flexible tubing and a small computer case fan at this point... :idea:

Anyway, with the Moon rising well above the horizon I decided to call it quits. Here is the single exposure I took through the Hα filter. It's effectively unprocessed apart from stretching, levels etc as the underlying quality is so poor that it just isn't worth doing the darks, bias and flats stuff. It's a shame because I can see that there's a lot more to come once I get some good data, and a "dry" lens, but I offer it here to show the awesome field of view the 165mm lens plus 52.1 mm diagonal sensor provide.
    Image
The original is 4096x4096 pixels but I've downsized it to 512x512 pixels for display on the forum. The best focus test shot, a 10 second exposure through a green filter and complete with hot pixels and also effectively unprocessed is available here (616 kB JPEG) at full 4096x4096 pixel resolution for those who want to take a look. Stars are sharp in the centre (Deneb is the bright one near the centre) but exhibit some coma, particularly at the extreme top left and bottom right corners.

Bob.

_________________
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: Mon Nov 28, 2011 12:12 am 
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Woo-hoo. Finally a clear night and no Moon. 8)

This evening I managed 5,000 seconds (as five separate exposures) of the North America nebula in Hα light together with three sets of 200 second exposures in each of red, green and blue. Bias and Dark frames also captured but I have yet to do the flats. Hopefully they will be done tomorrow and processing of the data can start on Tuesday.

Bob.

_________________
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 Nov 29, 2011 9:14 pm 
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Processing is going extremely slowly...

As always the issue is how to extract the most out of a set of images without going too far. I've a long way to go yet but I thought I'd share a preliminary Hα image. It's from a stack of five 1,000 second exposures centred at R.A. 20h 45m, Dec. 42° 15' with my Pentax MF 165mm lens wide open at f/2.8. The camera is an FLI ML16803 cooled to -25°C. I'm not particularly happy with the set of Dark frames I'm using but as this is really "first light" with this imaging system for me I've got a lot of learning to do and it would be just blind luck if I got everything right first time around. Anyway, enough excuses - here's an uncropped 800x800 px thumbnail. The full size image, a fairly compressed 2.4MB JPEB, can be viewed by clicking the thumbnail. The star images are not so good in the top left and bottom right corners but overall I'm pretty happy with the lens as it only cost me £150 ($235). 8)
    Image
If you'd like to know where in the sky the camera was pointing then you can see a map here. The outer magenta box shows the approximate field of view inside the constellation of Cygnus.

I think there is still a deal of work to do on that image with maybe just a tad more of the faint stuff to pull out and then there's the less than trivial matter of using the separate red, green and blue images (each from three stacks of 200 second exposures) to get some colour into the image. And that's a whole other can of worms... :roll: :lol:

Bob.

_________________
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 Nov 29, 2011 9:42 pm 
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"a tad more" of the faint stuff? That's damn deep already! Plus the resolution... blows away DSLR imaging.

For ball park "deepness" this is 16 minutes at f/2.8, where I previously managed 4 minutes at f/2.0, but I think I have a major sensor disadvantage with my 3MP* unit at 0C+. I also get funny smears, which I suspect might be due to the sensor and lens planes not being perfectly perpendicular.

Anyway, getting more data tonight? Reasonable skies over me at the moment. Orion finally is up but still in the low level glow right now.

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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: Tue Nov 29, 2011 9:45 pm 
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Hi popo,

No, no imaging tonight. My brain hurts with too much thinking during the day. :lol: :lol: :lol:

Oh, and it's 5 x 1,000 seconds which makes for just over 83 minutes. :shock:

Hope you get some good shots. 8)

Bob.

_________________
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 Nov 29, 2011 9:57 pm 
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Thought deepness varies with the sub time, whereas the total time is more for noise?

My evening of imaging might be over now as a band of patchy low cloud is overhead, unless it blows over soon. Got some 2 minute subs at f/2 and f/2.8 of pleiades to chew through with PixInsight later, if I can remember how to use it!

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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: Tue Nov 29, 2011 11:57 pm 
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Hi popo,

Goodness, I'd have to research that one. I've got a feeling that square roots come into it somewhere. :?

I couldn't resist having a further play. I'm playing a dangerous game with some uncorrected banding (need more Darks, I think) but the offending area is cropped out and yes, I did get a bit more of the faint stuff, hopefully not too much...
    Image
No link to a full-sized image this time. I reckon this image is pretty much as good as I can get without adding colour. Oh dear, so simple to say and yet I have a feeling it might be a real challenge until I get used to how to do it. :roll: :)

Bob.

_________________
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: Wed Nov 30, 2011 3:58 pm 
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As I suspected this colour thing is a lot harder than it seems at first glance. I've got to get on with other things now so I thought I'd share yet another step in the path before I leave the computer and rejoin the real world. :lol:.

I've added colour to the nebulosity but may have done it in a controversial way. Basically I added red to the mid-tones via a set of curves. There's a sort of reasoning behind the dark shades remaining monochrome because that's the way the eye works but when I allowed the saturated reds all the way up into the highlights I plain didn't like the effect. I've added the stars from the Hα image back for now without any attempt to use the colour and/or brightness information I have available from the RGB image. That's a task for another day.
    Image
Comments and criticism are welcome as I'm really struggling to achieve a good "look". :? :)

Bob.

_________________
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: Wed Nov 30, 2011 5:30 pm 
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Interesting trick :) I had a go previously at a false colour H-a only image and that didn't go well so I left it red channel only. Perhaps because of that, I'm not sure I like the whiter parts of the nebula as I think I'm expecting to see red there.

Do you think it would work if you tried to separate the stars, leave the nebula red and overlay white stars back on top? I tried and failed to do that myself previously, as I couldn't separate the stars very well.

Or can you acquire more data and add real colour back in? :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
Tinies: Sony HX9V.


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PostPosted: Wed Nov 30, 2011 6:01 pm 
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Hi popo,

Thanks for the feedback. It is difficult isn't it!

Yes, I actually did separate the stars out so that I could work on the nebulosity separately and tried, but didn't much like the look of, solid red highlights. Maybe I'll give it another go. That separation gives a lot of freedom but potentially at the cost of ending up over-processing said nebulosity.

Bob.

_________________
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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