I've been trying to figure out the best cameras to use with my scope and more importantly, to understand how to do the calculations, particularly with regard to getting a detailed zoom on an RoI. I have read several threads here and links to the calculation page everyone uses.
I'm also asking for folks to verify that I'm doing these calculations correctly and for any advice that comes to mind.
LS80, 560mm, F7
Solar diameter on a CCD sensor: 6.4mm
H-alpha critical sampling is F#/2.8. F7/2.8 = 2.5µm (smallest possible resolution)
6.4mm/2.5 µm = 2560 pixel minimum to capture the entire disk at native critical sampling.
For full disk, one choice would be the ASI183.
ZWO ASI183 5496x3672. Pixel size is 2.4µm. $699.00
6.4mm/2.4µm = 2667 pixels, so the sun fits. Excellent match to critical size, slightly oversampled. But only 19FPS in full frame. Slow frame rate should be okay for full disk. However, manufacturer states that this is not a good H-alpha camera as it exhibits a grid-pattern noise. They do state that a flat frame will help. They recommend the 1600 or the 174.
So I look at the ASI174 and it's not a match for full disk. Okay. But it's a fast imager. Soo...
My next step is to think about magnified images, but I am not sure how to figure out the best camera for magnified AoI detail. I did the following calculations for the ASI1600 vs ASI174.
Here's what I came to after trying different magnifications:
ZWO ASI174 1936x1216. pixel size 5.86µm. 164FPS. $599.00 (I like the FPS)
2.25x barlow, scope becomes 1260mm F15.75. Solar disk 14.4mm. Critical = 5.625µm. Good match, slightly oversampled. Solar disk = 14.4mm/5.86µm = 2457 pixels full disk. That yields 49.49% of the disk at max height (1216 pixels). That would be about 1/4 of the sun. That seems to be a start for more detailed images.
ZWO ASI1600 4656x3520. Pixel size 3.8µm. 23FPS full frame. $999.00 (slow at FF, unknown cropped)
1.5x barlow, scope becomes 840mm F10.5. Solar disk 9.6mm. Critical 3.75µm. Excellent match.
Disk 9.6mm/3.8µm = 2526. No problem for full disk. With all those pixels, is zooming a good option?...
Q1: Am I headed in the right direction here? Am I doing this right?
Q2: So if I have enough pixels and a good match for critical sampling on the ASI1600, which, of these choices would be better and why?
ASI183 vs ASI1600 for full disk?
ASI174 vs ASI1600 for magnification?
Would either be a good choice at all for magnified RoI imaging? Should I go with the ASI1600 over the ASI183 for full disk because of the manufacturer caution? Both have slow frame rates but I'm thinking that that would be alright for full disk.
Q3: I guess part of what I'm wondering is if people generally digitally zoom in using fewer pixels for Areas of Interest (AoI) or if they try to find a camera/barlow/reducer combo that puts the smaller AOI on the entire sensor. If that's the case, what's the best way of going about figuring out the best camera match, considering frame rate as well?
Q4: Does it really matter whether the sensor size is 5.86um vs 3.8um if I match the scope's focal length to the camera? If so, why/how?
Edited by statfreak, 03 June 2020 - 01:26 AM.