Using the ZWO asi1600mm with an 8RC

[Mr_42tr0nomy]

Hey y’all!

So my ATIK 414m is in the shop for a diagnostic.. if all goes aray, I will be in the market for a new camera. The ASI1600mm is up there in my top picks but my question is.. how will it do with my RC at it’s native FL (1625mm). I will be completely oversampled and imaging at .49”/pix. Will or will this not be detrimental? 

Best regards,

Teagan

[vlaiv]

It actually goes pretty well with RC8 - you can bin 2x2 your subs in software after calibration and prior to stacking to give you ~ 1.0"/pixel. You can also try some "novel" techniques to give a bit more sharpness to your images - do one stack of binned subs, and one stack of native resolution that you later resample to x2 smaller res using some good resampling algorithm like Lanczos. Then you blend in native/resampled image in bright areas (good SNR) for a bit more resolution.

For that chip size you will not need field flattener - you will hover need a good collimation to get good stars to the edge (and good focusing, of course, to combat slight field curvature at that size - don't focus on stars in frame center - 1/2 to 2/3 from center towards the edge is a good "zone" for focus).

Main problem when working on this resolution is seeing and quality of your mount. You need something like less than 1.5" seeing and 0.5" RMS guiding to get sharp images at bin 2x2. Otherwise it is a very good combo.

Here are some sample images with this combo (about 2h each, L with LPS filter, red zone):

[Mr_42tr0nomy]

Thanks for the details! And great images. Luckily my mount and guiding are up to the task and perform very well every night. Seeing on the other hand is usually poor. 

Im glad to hear that I won’t need to buy a FF/Reducer. The larger chip in the 1600 already gives me a wider FoV than I would like but that’s why cropping exists ??, haha.

The one thing that’s really pulling me towards the asi1600 is the short subs and low read noise. My 414 has much bigger pixels and a very narrow but wonderful FoV...(.82 ”/pix) the downside is that 30 minute subs, although easy to achieve, is quite risky. 

Were those images you posted binned 2x2? They’re very smooth as well?

 

[vlaiv]

1 hour ago, Mr_42tr0nomy said:

Thanks for the details! And great images. Luckily my mount and guiding are up to the task and perform very well every night. Seeing on the other hand is usually poor. 

Im glad to hear that I won’t need to buy a FF/Reducer. The larger chip in the 1600 already gives me a wider FoV than I would like but that’s why cropping exists ??, haha.

The one thing that’s really pulling me towards the asi1600 is the short subs and low read noise. My 414 has much bigger pixels and a very narrow but wonderful FoV...(.82 ”/pix) the downside is that 30 minute subs, although easy to achieve, is quite risky. 

Were those images you posted binned 2x2? They’re very smooth as well?

 

Yes, both binned 2x2. Not sure exactly how each of them was processed, I have two different approaches that I've tried. First is to stack native resolution and then bin result 2x2 prior to any additional processing (while image is still linear). Other is to bin each sub after calibration. Second approach is less intensive in terms of file sizes and processing. Only "drawback" of CMOS sensors and short sub duration that I've found is amount of data in processing. In single session, you can end up with as much as tens of gigabytes of data. I use 1 minute subs - each sub after calibration is around 64mb ( 4656×3520 x 4 bytes per one float number). That totals to 15GB for 4 hour session (240 subs). If I bin each sub 2x2 after calibration, then I end up with "only" 3.7GB of subs for stacking

 

[Mr_42tr0nomy]

1 hour ago, vlaiv said:

Yes, both binned 2x2. Not sure exactly how each of them was processed, I have two different approaches that I've tried. First is to stack native resolution and then bin result 2x2 prior to any additional processing (while image is still linear). Other is to bin each sub after calibration. Second approach is less intensive in terms of file sizes and processing. Only "drawback" of CMOS sensors and short sub duration that I've found is amount of data in processing. In single session, you can end up with as much as tens of gigabytes of data. I use 1 minute subs - each sub after calibration is around 64mb ( 4656×3520 x 4 bytes per one float number). That totals to 15GB for 4 hour session (240 subs). If I bin each sub 2x2 after calibration, then I end up with "only" 3.7GB of subs for stacking

 

Wow thats a lot of data! This is still all hypothetical as I may not even need a new camera. After reading your responses though it seems as though there’s a way around any issues I may have??