3 replies to this topic

[Sreekar]

I am new to solar imaging, but fell into it having seen the totality on April 8th. I have been into DSO imaging for a while and own several cameras and telescopes. Recently found a DayStar Quark on Astromart for a good price. So now I am left scratching my head on how to get started with solar imaging, and trying to put a setup together. 

 

Here is my final imaging train:

Sky watcher Evostar 80ED > Optolong UV/IR filter > 80 mm 2 inch Extender tube > DayStar Quark > ZWO 1.25" T mount > [ASI Camera]

 

I am trying to figure out what camera I should use with this setup. I own three cameras now (a) ASI 224MC; (b) ASI 533 MC; © ASI 1600 MM. I am leaning towards the ASI 224 MC, but I realize the pixel math to f-ratio doesnt work out well. 

 

My cameras: Pixel size in micro meter * 5 => 3.75 * 5 = 18.75 

 

My setup: Telescope (f7) * 4.2x barlow inside the Quark => 7 * 4.2 = 29.4

 

Here are my questions:

(a) Should i buy a new camera? If so, which one?

(b) I have seen Youtube videos where folks have used a 533 sensor and collected low frame rate videos and produced beautiful images of the sun. So should I use my ASI 533MC in place of ASI 224MC?

© What is the net impact of having a larger f ratio on my telescope? Will this make my image blurry? 

(d) Would I be gaining any benefit from getting a different camera, taking into account seeing and other factors?

 

Thanks in advance!

Sreekar

 

 

 

[MalVeauX]

Hi,

 

Critical sampling of 656nm on your camera's pixel sizes are:

 

IMX224 (3.76um) critically samples 656nm at F14

IMX533 (3.76um) critically samples 656nm at F14

MN34230 (3.8um) critically samples 656nm at F14

 

All your cameras sample 656nm the same. The 224 has less pixels, so faster FPS, but its a color sensor and loses resolution and sensitivity to that. The 533 & 34230 are both large pixel cameras with slower FPS but can be region of interest cropped down to a narrow FOV with faster FPS. The 533 has the latest pixel tech and is a little better, but its a color sensor and so it loses resolution and sensitivity. That leaves your 34230 sensor as the only mono sensor, so its likely the one to use out of this bunch perhaps. You can of course use any of your cameras here. But faster FPS is needed to lucky image and you're forced into fine image scales with telecentric systems so they will be sensitive to seeing.

 

But, you're of course oversampling on them all because your telecentric system is F29.

 

Your option is to use a focal reducer (and likely vignette a bit due to the blocking filter size of the Quark, 12nmm) or get a new camera.

 

The new camera of choice would be the IMX432, because it has 9um pixels and critically samples 656nm at F33. That would match your system and not need a reducer. 120+ FPS full pixel array.

 

A) The IMX432 makes the most sense, no focal reducer needed, samples 656nm at F33, 120 FPS, etc.

B) Ultimately it doesn't matter, both are not ideal as color sensors, try both since you have them and compare results after cropping region of interest to get closer to 100 FPS or better

C) Seeing is everything, so yes you are limited by seeing, 80mm in 656nm needs about 2 arc-seconds to critically sample, if seeing is worse than that it will be blurrier

D) Undersampling is the only way to deal with seeing, or using a smaller aperture to reduce image scale, etc. Lucky imaging is how you deal with poor seeing. Faster FPS is your friend.

 

Very best,

[Tapio]

Mono camera is best for Ha Sun imaging.
So your asi1600mm could do.
You could try your 533mc too to compare.
Try what you have now before you buy new.
Notice you get only a part of sun with your scope and Quark.

[Sreekar]

Thanks a lot Marty for the detailed explanation. Very informative. I will definitely start hunting for a good deal on a IMX432 camera. 

 

Thanks Tapio for the suggestion. I will try my 1600MM and see what I can capture. I did some test runs with my 224MC, but it makes sense to do some experiments with the 1600 MM while I find a good solar replacement camera.