Observing the Solar System Moons

[Allan]

I thought I would start a thread here given the experience and knowledge in the DSF even though it’s not a deep sky topic.

I’ve been putting an effort into observing the solar system moons for the last few years. I’m at 27 so far, and adding some more Jovian moons at the moment with opposition coming.

After two years of constant failure, I finally observed Amalthea a few nights ago. Last season I picked up Himalia, Elara and Pasiphae which are moons I would reasonably expect have been observed by others with decent aperture.

Now I’ve also added Carme and Sinope to the list in recent nights with the 32”, and these are more difficult targets, but ideally placed in the Southern Hemisphere right now. So I guess what I’m interested to know, is if these moons have ever been visually observed before? They were discovered on photographic plates by the big observatories, and I’ve found no records of anyone ever visually seeing them. I have Lysithea and Ananke still on the list that I’m confident I’ll observe over the next month as well.

I would really like to hear from anyone who has any info on this.

[wvreeven]

Impressive observations! And I thought Phobos and Deimos were hard...

[Dragan]

I'm really curious. What is it that you're using to help confirm your observations?

[Paul Alsing]

Any luck yet with Charon?

[Allan]

Impressive observations! And I thought Phobos and Deimos were hard...

It’s all relative I guess. Phobos and Deimos are not that easy when you first attempt seeing them, but like anything get easier with practice. Seeing those two lots of times over the years was certainly great practice for the tougher moons I’ve managed to see subsequently.

[Allan]

I'm really curious. What is it that you're using to help confirm your observations?

I’ll tell you my process Dragan. First I download the ephemeris data from the Minor Planet Centre for the moons. So far I have found the data to be very accurate with all the moons exactly where the MPC said they would be.

At the scope I use Sky Safari 6 with the extended star database down to magnitude 17. I put the moon co-ordinates into Sky Safari and then goto that position and get myself orientated in the eyepiece field of view, and figure out where the moon should be. That process has actually been very quick and easy to do with all the faint moons.

I put the iPad away and then start looking for the moon. Sometimes they are immediately obvious right where the MPC data said they would be, or else I have to get my dark adaption and averted vision going to pick them up.

In all cases I usually spend up to one hour with the moon and it is quite easy to see them move over that time against the background stars. Some of these Jovian moons I’ve seen this week are moving at 14 arc minutes an hour, so 20 minutes is all it takes to see they have moved. So that’s a secondary confirmation to the fact they are exactly where they were supposed to be.

[Allan]

Any luck yet with Charon?

Not yet, but I haven’t attempted it yet this season. I did learn something valuable researching this a while ago. Charon is at max elongation from Pluto when it is at 150 degrees and 330 degrees relative to the planet. So that gives a good observing window every 3.2 days. Last season I was just trying randomly without that knowledge.

The next window is tonight, so I will give it a try. Opposition is July 15 so I should have plenty of opportunities.

[Dragan]

I’ll tell you my process Dragan. First I download the ephemeris data from the Minor Planet Centre for the moons. So far I have found the data to be very accurate with all the moons exactly where the MPC said they would be.

At the scope I use Sky Safari 6 with the extended star database down to magnitude 17. I put the moon co-ordinates into Sky Safari and then goto that position and get myself orientated in the eyepiece field of view, and figure out where the moon should be. That process has actually been very quick and easy to do with all the faint moons.

I put the iPad away and then start looking for the moon. Sometimes they are immediately obvious right where the MPC data said they would be, or else I have to get my dark adaption and averted vision going to pick them up.

In all cases I usually spend up to one hour with the moon and it is quite easy to see them move over that time against the background stars. Some of these Jovian moons I’ve seen this week are moving at 14 arc minutes an hour, so 20 minutes is all it takes to see they have moved. So that’s a secondary confirmation to the fact they are exactly where they were supposed to be.

Very interesting. What about equipment? What scope are you using? Typical power, exit pupil etc? I find this fascinating considering I've never really come across anyone doing this type of observing.

[Allan]

Very interesting. What about equipment? What scope are you using? Typical power, exit pupil etc? I find this fascinating considering I've never really come across anyone doing this type of observing.

I have a 32” SDM with Lockwood mirror at my astro property. I built a ROR observatory for it which is a nice luxury.

Typically most of this observing I do at 516x to over 1000x if required, so a 1.6mm exit pupil or less. I had two years of failures at trying to see Amalthea, and eventually the key was using my Denk Binoviewer with 10mm ZAO II’s at 619x. So I use all sorts of mono and bino eyepiece combinations depending on the situation.

I’ve written of this a bit on Cloudy Nights, but no one there seems aware of anyone observing the really faint moons. As you say, not a lot of people doing it for what ever reason. But I find it fascinating and challenging. It’s possible no one has ever visually seen the group of Jovian moons I observed this week. That’s why I thought I would pose the question here given the knowledge of some of the members.

[Dragan]

I have a 32” SDM with Lockwood mirror at my astro property. I built a ROR observatory for it which is a nice luxury.

Typically most of this observing I do at 516x to over 1000x if required, so a 1.6mm exit pupil or less. I had two years of failures at trying to see Amalthea, and eventually the key was using my Denk Binoviewer with 10mm ZAO II’s at 619x. So I use all sorts of mono and bino eyepiece combinations depending on the situation.

I’ve written of this a bit on Cloudy Nights, but no one there seems aware of anyone observing the really faint moons. As you say, not a lot of people doing it for what ever reason. But I find it fascinating and challenging. It’s possible no one has ever visually seen the group of Jovian moons I observed this week. That’s why I thought I would pose the question here given the knowledge of some of the members.

I have a slightly off topic question for you since you've touched on it in your post.

Minimal element eyepieces such as your ZAO (or ortho's) vs multi-element EP's such as Naglers and Ethos and which is better to eek out the faintest detail seem to come up time and time again. What are your findings when it comes to such faint observations? Which perform better in your particular style of observing? Do you find the orthos provide better light transmission? Do you prefer the wider FOVs of other EP's? (I believe I know your answer but I need to ask)

I was curious to see that you use binos. Do you not find a loss of transmission using binoviewers?

I find all this very interesting!

[Allan]

I have a slightly off topic question for you since you've touched on it in your post.

Minimal element eyepieces such as your ZAO (or ortho's) vs multi-element EP's such as Naglers and Ethos and which is better to eek out the faintest detail seem to come up time and time again. What are your findings when it comes to such faint observations? Which perform better in your particular style of observing? Do you find the orthos provide better light transmission? Do you prefer the wider FOVs of other EP's? (I believe I know your answer but I need to ask)

I was curious to see that you use binos. Do you not find a loss of transmission using binoviewers?

I find all this very interesting!

To start with the binoviewers, yes I find there’s a significant light loss when using those. I only use them on brighter solar system objects. But having spent two years trying to see Amalthea without any success, I decided to try the bino on that moon. It is still relatively bright, around magnitude 14.5, but hidden in Jupiters glare. The two eye, bino summation thing worked first time out and I got my first look at Amalthea.

My strategy is to use Ethos or Delos to find the location and then start looking for the moons. Obviously then depends which ones I’m looking at and their magnitude as to whether I pull the ZAO’s out. What I see often is a moon that might be averted vision in the Delos becomes often direct vision through the Abbe Orthos. Sinope at magnitude 18.2 is tough enough that I just use the ZAO’s to observe it.

I see much better light transmission through the minimum glass eyepieces when using the 32”. But my mode of use is to always start with the widefields and finish with the Abbe Orthos. Interestingly, when I applied the same principle to the 12” I had for a long time, I couldn’t really see much of a difference between the two classes of eyepieces. The performance gap seems to grow as aperture increases.