As you can see the 183mm image is much the same brightness despite being taken on a 305mm scope in semi rural skies versus a 435mm scope at a dark site. The CDK image should be much brighter than the 183mm but its not.
This matching pixels to optics, in my opinion, is a very limited theory and there are other factors just as important like QE, read noise, dark current, dark skies, seeing. The effects of mismatched pixels don't seem to me to be that great in reasonable seeing.
Greg.
Last edited by gregbradley; 12-08-2020 at 07:27 PM.
Greg - in this scenario it would be much more fitting to compare SNR from your both cameras when operating on the same scope (same length of total exposure), as Lewis is contemplating replacing his KAF8300 with ASI183 while keeping the same scope.
I believe is you stick ASI183 onto your CDK17 you will see a much weaker signal than from the KAF16200. Alternatively, if you attach KAF16200 to your Honders I suspect the SNR will be stronger than with the ASI183-Honders combo for the same length of total exposure and for the same object.
Debayer in PI. It's smart enough to drizzle off the original bayer matrix. Shoot shorter subs but more of them.
Agreed Marc - last time I imaged, I did that - dither, debayer, drizzle integration etc. And that was using a 9 micron sensor camera and no horrific results - well, no more horrific than my usual mess.
And the new EZ Suite really makes my mess just that little bit tidier.
Greg - in this scenario it would be much more fitting to compare SNR from your both cameras when operating on the same scope (same length of total exposure), as Lewis is contemplating replacing his KAF8300 with ASI183 while keeping the same scope.
I believe is you stick ASI183 onto your CDK17 you will see a much weaker signal than from the KAF16200. Alternatively, if you attach KAF16200 to your Honders I suspect the SNR will be stronger than with the ASI183-Honders combo for the same length of total exposure and for the same object.
Yeah I wanted to do that but I don't think I have the same data from both cameras on the same scope. I'll look again.
The small pixels might give you sharper results, they'll almost certainly get you rounder, less blocky stars... I agree with what's already been said though, I'd try dither + drizzle first which will definitely round up those stars.
What's your typical guide error (total RMS in arcseconds)? What do you use for autofocus (hardware and software)?
The small pixels might give you sharper results, they'll almost certainly get you rounder, less blocky stars... I agree with what's already been said though, I'd try dither + drizzle first which will definitely round up those stars.
What's your typical guide error (total RMS in arcseconds)? What do you use for autofocus (hardware and software)?
Get perfectly round stars. I do dither (up to 5 pixels) and drizzle integrate in PI. Here's an image from last time I imaged last year https://www.astrobin.com/full/mv7lg0/0/
Guide error.... errr.... don't you recall my guide error...essentially, well, none...
Autofocus? No way Jose! Bahtinov and Eyeball Mk.1 for me (zoomed in 300% in MaxIM 6)
Here's my guide error...yeah its in pixels, but I don't use PHD...MaxIM does a FANTASTIC job. Suavi, it is STILL not guiding on a hot pixel (another shot when there was a minor burp here: http://www.iceinspace.com.au/forum/a...e.php?a=225766)
Get perfectly round stars. I do dither (up to 5 pixels) and drizzle integrate in PI. Here's an image from last time I imaged last year https://www.astrobin.com/full/mv7lg0/0/
Guide error.... errr.... don't you recall my guide error...essentially, well, none...
Autofocus? No way Jose! Bahtinov and Eyeball Mk.1 for me (zoomed in 300% in MaxIM 6)
Here's my guide error...yeah its in pixels, but I don't use PHD...MaxIM does a FANTASTIC job. Suavi, it is STILL not guiding on a hot pixel (another shot when there was a minor burp here: http://www.iceinspace.com.au/forum/a...e.php?a=225766)
lol I had forgotten about your hot pixel guiding.
I asked about focusing and guiding because in my experience these are critical to get the most out of your scope and if there was any question there, I'd be focusing (pun intended) on those before even thinking about a different camera.
Maybe you're an expert turner of focus knobs, but personally I could never manually focus as well as a properly-configured auto focus routine can do. In addition to that, if your stars aren't looking like little squares at 2.48"/px with a Tak, I'd be guessing you're probably not getting the best focus that you could. You're too undersampled for them to look perfectly round (in single subs, prior to drizzle integration).
As for guiding... it's common to assume that if your stars are round, your guiding is fine, but that only suggests that both axes are equally good (or bad). I can very easily misconfigure guiding to significantly increase my FWHM while still getting round stars. In my experience, solid guiding is the next most important thing.
If there's any question on either guiding or focusing, I'd encourage you to to investigate those first.
Regards drizzle versus smaller pixels. My old ASI294 on my 80mm is just about bang on 2 arcsec per pixel, I recently used drizzle in APP on a set of subs I had and ran it a couple of times at different settings to work out where the noise started to become objectionable. First light with my ASI2600 (3.7 versus 4.63um pixels to make it 1.6 or so arcsec per pixel) was of the same target, unguided and with spacing still to be sorted, but to me the star profiles looked at least as smooth with 20 subs and all the tracking and spacing errors as the drizzled stack of 100 subs.
Paul - I believe 3.7micron pixels are at about diffraction limit for your 80mm, so stars should be round in the subs already, as opposed to 4.6micron pixels that, with good guiding, should give somehow blocky stars. Wondering if FDHM got better (smaller) with the new camera.
I am not paying any attention to image stats yet, not until it is properly set up spacing wise and guided. Subjectively the stars look nicer already with native resolution instead of recovering it via drizzle on more undersampled data.
Regards drizzle versus smaller pixels. My old ASI294 on my 80mm is just about bang on 2 arcsec per pixel, I recently used drizzle in APP on a set of subs I had and ran it a couple of times at different settings to work out where the noise started to become objectionable. First light with my ASI2600 (3.7 versus 4.63um pixels to make it 1.6 or so arcsec per pixel) was of the same target, unguided and with spacing still to be sorted, but to me the star profiles looked at least as smooth with 20 subs and all the tracking and spacing errors as the drizzled stack of 100 subs.
I suppose it says you can get a result both ways.
Both ways are increasing your sampling, which is why both work
Yep, just now having done it both ways I reckon my preference is for good sampling to begin with rather than retrieving more data via drizzle, the noise difference is noticeable, at least to me.
The downside being that the better sampling increases data storage requirements and processing times!
I asked about focusing and guiding because in my experience these are critical to get the most out of your scope and if there was any question there, I'd be focusing (pun intended) on those before even thinking about a different camera.
Maybe you're an expert turner of focus knobs, but personally I could never manually focus as well as a properly-configured auto focus routine can do. In addition to that, if your stars aren't looking like little squares at 2.48"/px with a Tak, I'd be guessing you're probably not getting the best focus that you could. You're too undersampled for them to look perfectly round (in single subs, prior to drizzle integration).
As for guiding... it's common to assume that if your stars are round, your guiding is fine, but that only suggests that both axes are equally good (or bad). I can very easily misconfigure guiding to significantly increase my FWHM while still getting round stars. In my experience, solid guiding is the next most important thing.
If there's any question on either guiding or focusing, I'd encourage you to to investigate those first.
Zero issues with guiding or mount. Maybe my focus isn’t exact but I am not a fan of adding yet more bits on. Been there with AF before, didn’t float my boat - I like actually being out with my scope doing stuff. Automated to me takes away most of the fun of astronomy, and besides, not in it for image glory and fame.
Only reason I was considering a small pixel cam is because of my typical low total time data sets. I am happy with my round stars as is, and if only slightly under sampled given our typical good to excellent seeing here, I can live with it. Better than being over sampled
David doesn’t mean anything to me honestly and I don’t use PHD. So long as it works I don’t chase numbers.
My graph in MaxIM in arcsecond isnt much different. It’s not the mount or guiding I am even remotely interested in, it was simply can I maybe get the stars etc sharper given all else being to my satisfaction.