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Old 17-06-2016, 06:11 AM
UBoat
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Anyone using the Starlight Express for DSO imaging?

Does anyone know of user groups for the Starlight Express Ultratar C that publish video or static images that might demonstrate its DSO imaging capability?

I'm putting together an ultraportable kit for hiking into dark sites. Similar concept to the Meade ETX80 but set up for astroimaging and viewing DSO's. The last piece of the jigsaw is to select a camera that is small with low power consumption (< 200mA at 5VDC USB, and capable of stacking on the fly. I'm currently using an ASI120MC which is not quite sensitive enough for my purpose and an Orion G3 deep space mono unit with the cooling unused, which is a bit low on resolution. Both work very well with Sharp Cap for live imaging and stacking.

I'm considering the Starlight Express Ultrastar C and the ASI 224MC. The ASI camera has a useful following of users who have posted quite a few well specified DSO images and the camera looks suitable provided I'm careful with darks and manage the amp glow. The Ultrastar specification looks compelling particularly for its low noise but I haven't been able to find a significant set of examples of its use as an imaging camera - other than images of the ubiquitous M42.

Any advice most welcome. Peter
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Old 17-06-2016, 08:47 AM
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Camelopardalis (Dunk)
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Welcome to Ice in Space Peter!

The sensor in the Ultrastar C is/has been used in many an astro cam previously, although if you're looking to do some long exposure DSO imaging I'd recommend you get a camera with a cooled sensor.

The ASI224 is very sensitive - if you are looking to try something different, it can be quite effective with lucky imaging where the thermal noise takes less of a grip, and using such a technique you could probably forego the cooling.

Another point to consider is that while the two cameras have more or less the same resolution, their pixel sizes are quite different, which results in a very different FOV. The Ultrastar will cover almost 4x the area of sky (assuming the same scope), at the cost of being able to resolve smaller details.
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Old 17-06-2016, 05:41 PM
UBoat
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Thanks for that advice - good idea to look up the chip imaging history rather then the camera- I'll try at the weekend. also very interested in your positive feedback on the ASI224. With a 70mm scope sensitivity is going to be an important issue. Will have to calculate a bit and think hard about the trade-off between resolution and FOV that you pointed out.

There will be a fair bit of natural cooling as the temperature gets to near zero C or below in the Blue Mountains. Coolings not going to be available as I'm hiking and there's a strict weight budget and I need to include hot coffe and a sandwhich or two! I'll carry a freezer suit in the tripod bag; don't really want to wear a freezer suit on the train:~) I'll be using an ultra light weight mount with auto-guiding on an EQ3 and prepared if necessary to stack a large number of frames of about 1 minute to 10 minutes each so the low read noise of the ASI224 will come in handy if that's the camera I choose.
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Old 04-07-2016, 08:35 PM
UBoat
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Trying to understand dark current specifications

I'm still looking for an uncooled imaging camera for use while hiking under dark skies and trying to assess the range of exposure times that are possible for the SX Ultrastar before making a purchase. I've compared with the Infinity camera and note the latter is limited to exposure times of two minutes because it's optimised for live viewing.

The Ultrastar uses the same chip as the Infinity but at much lower power. So I'm not sure that the comparison is fair. Also Optcorp show a specification that says the Full Well Capacity (FWC) is greater than 23,000 e- unbinned, that the Dark Frame Saturation Time is greater than one hour and the dark current less than 0.1 electrons/ second at +10C ambient. This implies a Dark Frame Saturation Time of about 60 hours. This is a factor of two of the uncooled performance at 17degC of my ATIK 314L+ that loses about 3% of its dynamic range to dark current with an hours exposure time.

On the basis of that specification the comparison with my Atik314 and the Ultrastar low power consumption I would assess that exposures of an hour rather than two minutes would be feasible with an Ultrastar but I'm cautious because Optcorp are so conservative in simply saying 'greater than an hour to full well capacity' when their specification suggests 60 hours.

My assessment is naive so I'd be glad if anyone can correct or confirm my interpretation and/or say what exposure times the SX Ultrastar is capable of?

Thanks, Peter
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Old 14-07-2016, 06:20 PM
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There's a huge group using the 825 based ultrastar and infinity for near-live viewing of DSOs.

http://www.cloudynights.com/topic/14...7#entry7325207
And big on ultrstar stargazerslounge

2min limit as not cooled. Atik414 is cooled version and has longer exposure times

Last edited by ChrisV; 14-07-2016 at 06:59 PM.
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Old 16-07-2016, 09:09 PM
UBoat
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Hi Chris,

Those links are perfect for my purpose, particularly the Stargazers Lounge Link.

Very much appreciated your advice, Peter
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