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PostPosted: Thu Jun 07, 2012 5:32 pm 
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On DMK31 vs 41, I'm thinking the 41's greater area would help more than the frame rate (I'm not a big fan of doing mosaics). It's half the frame rate, so ok you need double the run time for a given frame count, but you gain the bigger area... I'd even consider the 51 if it wasn't the big jump in cost.

I'm also wanting to go the video route for lunar since I'm seeing limited 99% of the time. No two DSLR frames ever come out the same!

SCT is on my long term wish list. A hyperstar on that would be my deep field dream machine, if I wasn't light pollution limited. Not to mention the budget.

Definitely wanting to go mono since over 75% of my astro imaging is now narrowband for light pollution and specific area imaging. Which is why I had my mini rant on mono vs colour sensor costs earlier!

I did find out at work we're getting a bonus in the next pay packet. Dunno how much it will be yet, but I might be able to bring forward a bit of purchasing...

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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: Thu Jun 07, 2012 6:02 pm 
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The Sensor on the DMK31 is smaller then the DMK41 so its the same principle applied to crop sensor.On my Lunt LS60 , the sun almost fit completely in the DMK31, it does take 2 images mosaic to get a full sun surface image but on the other hand, I need less magnification for prominence. For the sun, DMK41 and even the DMK51 is best because resolution always win, if you don't need the FPS.

I hope it works out for you. I already share some of my solar work I did with the DMK31 so its a pretty good little camera. The DMK41 can only be better *wink*.

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Canon T2i (550D)- Tamron 17-50 F2.8 Non-VC, Sigma 70-200mm F2.8 EX DG OS HSM, Canon EF-S 55-250mm F4.5-F5.6
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PostPosted: Thu Jun 07, 2012 6:09 pm 
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I have heard the DMK41 on PST would give a full sun, which is in part why I locked in on that. There's always barlows if I need more... but the 40mm aperture of the PST is likely the bigger limiting factor here.

If I can go back a step here, guiding for the sun was mentioned earlier... how does that work in practice? Does guiding software recognise the sun, or is there some other indirect method? I've got some ideas for the latter, but don't want to be barking up the wrong tree if there's a simple way of doing 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: Thu Jun 07, 2012 6:23 pm 
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In my HEQ5 mount, I set the tracking to Solar. problem solved. Most tracking mount have 3 modes : Lunar, Solar, standard tracking (Default)

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PostPosted: Thu Jun 07, 2012 6:32 pm 
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Weren't we talking about guiding as opposed to tracking? I never get great polar alignment even when I can see Polaris. It isn't happening in daytime!

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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: Thu Jun 07, 2012 6:33 pm 
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no guiding. I use tracking for solar. That is sufficient. I use my iphone compass apps with the true north option to roughly polar align in daytime. If you want to do any sort of guiding, polar alignment will be become an must for you.

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Canon T2i (550D)- Tamron 17-50 F2.8 Non-VC, Sigma 70-200mm F2.8 EX DG OS HSM, Canon EF-S 55-250mm F4.5-F5.6
http://www.astronomyphotography.com


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PostPosted: Thu Jun 07, 2012 6:43 pm 
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To clarify, at night I can currently get accuracy better than about 1/10th the distance between Polaris and actual north, but unguided that still sucks for anything other than a short exposure (minutes). I'm hoping guiding will iron out the residual error.

At day, I use a different viewing spot for the sun than I do for deep sky so I can't just copy my night position. Just pointing to north isn't close enough and I still have to regularly fine tune the aim every few minutes or so depending on how bad it is on the day. Again guiding should fix that, and in this application field rotation is a non-issue since fractions of a second exposures aren't going to be a problem!

Unless there's a better way (for example, using the video feed of the sun?) then I was thinking of a separate guide cam connected to a wide angle lens. That should reduce the apparent size of the sun to a small enough point to look like a star. With a solar filter to reduce the intensity of course.

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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: Thu Jun 07, 2012 6:49 pm 
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I don't know anyone who would do Solar guiding. repointing every few minutes is no big deal. Like I said, the iphone compass apps is very useful and can get you close enough.

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Canon T2i (550D)- Tamron 17-50 F2.8 Non-VC, Sigma 70-200mm F2.8 EX DG OS HSM, Canon EF-S 55-250mm F4.5-F5.6
http://www.astronomyphotography.com


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PostPosted: Thu Jun 07, 2012 7:18 pm 
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Hmm... maybe I am getting a bit carried away with wanting to guide everything :D It if moves, guide 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: Thu Jun 07, 2012 8:09 pm 
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the better your polar alignment, the less your guiding cam has to sent correction to the mount which then increase the exposure time without trails. Polar alignment/ level mount is crucial to a good guiding. One doesn't go without the other. Let me find you a link to a great tutorial on DSO imaging and best practice. Its eluding me now.

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Canon T2i (550D)- Tamron 17-50 F2.8 Non-VC, Sigma 70-200mm F2.8 EX DG OS HSM, Canon EF-S 55-250mm F4.5-F5.6
http://www.astronomyphotography.com


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PostPosted: Thu Jun 07, 2012 9:55 pm 
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You don't need to tell me about polar alignment, it just doesn't go accurately enough with what I currently have. And without a fixed mount I can set and forget, I can't afford to spend the whole evening tweaking it by drift method.

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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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