[UBoat]

Hello Ray

Thanks for those useful tips for taking and quantifying noise in darks and flats. Distinguishing the locked in hot pixels is straightforward, but as for the remainder I'll try taking and comparing a series of darks at different exposures and watch for pixels that reproducibly show more dark current than most. In the ASI120 these are clearly linked to the electronics surrounding each pixel but in the Atik such pixels seem randomly distributed. Which all makes sense in light of your explanation.

Do you know if there has been much work done on the 'spatial noise' that might arise from stacking many 1 or 2 minute subs? IE noise introduced by the rotational alignment and stacking of successive images in which pixels may not quite line up, particularly square pixels. Does it degrade resolution more than stacking a few long exposures?

BTW I took your suggestion and have been testing the Atik using a brand new Minigorilla rechargeable battery pack. The operating time is 9 hours drawing on a capacity of 2.8AH at 12V which suggests a current of 300mA for the Atik without cooling. So its capable for a night's viewing. The cooling would add another 500mA and the Atik would then only last about an hour.

No word from SX on example images and no examples from any of the three blogs I've asked, so I'm thinking its very rare for people to use the Ultrastar to record images, which doesn't mean that it can't be done just that people don't.

Many thanks for all your advice, Peter

Hello Greg,

Interesting suggestion to use a DSLR and I can see that a portable system based on it would be very attractive for large FOVs. For my purposes I think the DSLR size and battery consumption would be an issue. If the Ultrastar produces images as well as the Atik 314 in uncooled mode then it would be almost impossible to beat in terms of size, weight and power consumption. Another possible candidate is the ASI1600 CMOS which is less costly and producing some impressive deep space images.

Your point about the computer is very valid but I'm after better load capacity and tracking than a Polarie could provide and will be using the Star Adventurer autoguide and improved polar alignment capability. I also expect to use live stacking; and possibly plate solving for AAVSO work so will be taking a tiny slow antiquated HB netbook that has proven effective and runs all night and can be recharged with the solar panel. Looking forward to tablets becoming fully astroimaging capable!

Many thanks to you also for your advice. Peter