Advice on Saturn

[Matt S]

So this was my first serious attempt at photographing Saturn, so far I've only worked with the Moon, Jupiter and Mars (Saturn is usually blocked / too low for me).

I spent a bit of time setting things up, it was looking pretty good in the eye piece, then I switched to the camera and tried a few shots with/without a 2x Barlow so I'd have a few sets of images to work with. I can't believe this was the first time I found the stabilising feature in Firecapture, but I thought that was handy - made it a lot easier to adjust focus until it looked like I had the sharpest edges.

Anyhow, I was looking forward to processing the results, but I'm a little disappointed with these. I know that some nights you just don't get anything good, but I'd like some thoughts from all you seasoned planet imagers on what I might be missing, or could improve (albeit hard to tell from a couple of roughly processed shots!).

 

Equipment:

Skymax-127

ASI678

2x Barlow 

 

I thought it looked like I had quite a lot colour blurring off to the edges - I usually get quite clean edges with Jupiter, but then that is a lot higher for me. is this, poor focus, or does this look like a symptom of atmospheric dispersion? Saturn at this point wasn't terribly high (Saturday night around 10.30 - SkySafari thinks this was around 15 degrees?).

With Jupiter, I usually try and use the moons as a focal point, any tips for Saturn, I wasn't sure I could see a moon in the shot!

I was generally trying to get ~2 min recordings so I'd have a good number of usable frames, I was really getting only around 20% above the 50% line in AustoStakkert... 

Lastly, any advice on settings in FireCapture you have found worked well for Saturn would be appreciated!

 

[bosun21]

With your camera having a pixel size of 2 you don't need to use a 2x barlow. You want to aim for approx 5 x pixel size to match the focal ratio of the scope. The low altitude of 15° would benefit greatly from the use of an ADC to compensate for the atmospheric dispersion clearly showing in the top image. What frame rate were you capturing at and did you use ROI?

[Kon]

To add to Ian's comments, it seems to be the case of really bad seeing at 15 degrees; your focus is off here too (at this angle you can use the shadow of the rings  on the planet or their edge; if seeing is good you will get hints of Cassini division). Regarding settings, I aim for a 70-90% histogram; I usually do 10-11ms exposure and with Saturn you can capture ~5min before rotation starts blurring features. Worth getting loads of 5min videos and do image derotation in Winjupos. If you can, wait until it is higher up and keep an eye on the jetstream maps as it can cause havoc with seeing.

It is hard to tell if collimation is a bit off or it is due to bad seeing as you have flaring at the planet.

[Matt S]

Thanks both!

8 hours ago, bosun21 said:

What frame rate were you capturing at and did you use ROI?

Yes, I was using ROI and maybe getting between 150 FPS with the Barlow, and 240 without. 
 

2 hours ago, Kon said:

at this angle you can use the shadow of the rings  on the planet or their edge; if seeing is good you will get hints of Cassini division

I hadn’t thought of that! Thank you! I was simply going off the limb of Saturn and aiming for the sharpest edge I could find (I couldn’t discern any detail on the surface so was using the edge as a guide).

I’ll definitely try longer exposures then - I’ve not really worked with WinJupos before. It’s on my list to try - I’d watched a webinar from Damien Peach regarding this and taking hours of Jupiter footage so I’ll certainly try that out. I was trying to get my “technique” for Saturn figured out to start with. 
 

Collimation I think is pretty good (visual targets etc all look good to me) so I’m thinking more focus/seeing issues.
 

I do think I’m going to need to find another spot to observe from though - my current placement(s) mean Saturn is just not very high before it gets blocked and I guess I may need to bite the bullet and buy an ADC too 😁  

one question I do have, in FireCapture there is a setting for ‘use WinJupos naming’. Is that useful to enable if you plan to use it afterwards to derotate footage?

[bosun21]

Yes use the Winjupos file naming in Firecapture in order to allow Winjupos to de-rotate accurately. I use Sharpcap which also has this setting in its capture settings.

[Kon]

Firecapture also had a focus plugin but I haven't used it yet.