At what altitude (of the target) is an ADC worth considering?

[ONIKKINEN]

Saturn will be at 14 degrees for my latitude of 60N this year and i think that would definitely benefit from an ADC. I just dont know if an ADC will salvage that so not sure if i would want to spend on that right now. Jupiter will be at 30 degrees, so im not sure if an ADC is strictly necessary here as its not super low anymore. Mars will be at 54 degrees, so probably not that important.

So, where do more experienced planetary imagers draw the line on whether an ADC is helpful, or even a must have accessory for the best possible images?

Here is what Saturn looks like without an ADC at 14 degrees:

Completely separated RGB and a boiling view. Only glimpses of the cassini division appear here and there so im not sure an ADC will significantly improve it, but could be wrong so looking for advice.

[CraigT82]

Some excellent info here…

https://skyinspector.co.uk/atm-dispersion-corrector-adc/

Long and short of it is it depends on your imaging FL. Bigger scopes/longer focal lengths will gain an advantage even at higher elevations. With a big scope and OSC cam 1 arc second of dispersion would be visible in the image and so you’d benefit from the ADC up to 55 degrees alt. Of course if you’re less fussy you may not care about 1 arc sec of dispersion and may be happy to just align the channels in post. 
 

OSC cameras also generally require an ADC at higher elevations (black line in chart) than you could get away with a mono camera.

 

 

 

Edited August 6, 2022 by CraigT82

[ONIKKINEN]

39 minutes ago, CraigT82 said:

Some excellent info here…

https://skyinspector.co.uk/atm-dispersion-corrector-adc/

Long and short of it is it depends on your imaging FL. Bigger scopes/longer focal lengths will gain an advantage even at higher elevations. With a big scope and OSC cam 1 arc second of dispersion would be visible in the image and so you’d benefit from the ADC up to 55 degrees alt. Of course if you’re less fussy you may not care about 1 arc sec of dispersion and may be happy to just align the channels in post. 
 

OSC cameras also generally require an ADC at higher elevations (black line in chart) than you could get away with a mono camera.

 

 

 

Thank you, this site answered all the questions i had in mind. Also many questions that i didn't know i needed to ask, great read!

Atmospheric dispersion is a lot stronger than i realized, and looks like i really do want to have one to get the best out of OSC imaging with any altitude of target really, as nothing in the ecliptic rises anywhere close to the zenith.

[Pete Presland]

An ADC has  certainly helped my images, but it is still tough down at those altitudes.

[Cosmic Geoff]

I have found some dispersion correction needed at higher altitudes than I expected.  It is also possible to correct for dispersion in processing software, e.g. Registax, but this is best reserved for fine tweaking if you see residual dispersion, not a substitute for a glass ADC.

Also note that if you shoot in IR you should not need an ADC (except maybe in extreme cases).

Edited August 7, 2022 by Cosmic Geoff

[ONIKKINEN]

41 minutes ago, Cosmic Geoff said:

I have found some dispersion correction needed at higher altitudes than I expected.  It is also possible to correct for dispersion in processing software, e.g. Registax, but this is best reserved for fine tweaking if you see residual dispersion, not a substitute for a glass ADC.

Also note that if you shoot in IR you should not need an ADC (except maybe in extreme cases).

So far i have just stacked with align RGB option checked in AS!3 and the channels are aligned, but obviously that will not fix the blur within the different colour channels. I will be shooting with an OSC camera (the new 678MC once i have it) and didn't plan on doing IR. But maybe one day will dabble in IR since the camera has a decent QE at near IR.

2 hours ago, Pete Presland said:

An ADC has  certainly helped my images, but it is still tough down at those altitudes.

Indeed, its a dice roll whether Saturn shows anything interesting in an eyepiece/camera at its current altitude. It will take all the way to 2026 until Saturn will be at 30 degrees or more, so while i am patient, i would prefer to get a good image without waiting for 4 years first.