11 replies to this topic

[12BH7]

Funny how when you think of viewing moons your mind quickly goes towards - magnification.  I've been relearning what the best magnification is to view Saturn's moons with my telescopes. 

 

What I find, and this was a surprise to me only because I forgot, is that the more I increased the power, the fewer moons I could identify.  With an 8" SCT I can clearly see all five moons, on a good night, using between 76x - 83x. When I up the power I started to see the fainter moons drop out.

 

For those that are new to planetary the moons of Saturn are mostly points of light.  It's always a thrill to see if can identify the five major moons.

[Cpk133]

Funny how when you think of viewing moons your mind quickly goes towards - magnification.  I've been relearning what the best magnification is to view Saturn's moons with my telescopes. 

 

What I find, and this was a surprise to me only because I forgot, is that the more I increased the power, the fewer moons I could identify.  With an 8" SCT I can clearly see all five moons, on a good night, using between 76x - 83x. When I up the power I started to see the fainter moons drop out.

 

For those that are new to planetary the moons of Saturn are mostly points of light.  It's always a thrill to see if can identify the five major moons.

Try expressing performance in terms of exit pupil and compare that across scopes.  To detect limiting magnitude stars / moons, i find 1.2-1.8mm exit pupils work best.  This plays into a discussion with Luxo not long ago where he said that superior optics that put the light into the maxima rather than into diffraction rings or scatter light, can detect faint objects under higher magnification where lesser optics fall below the threshold of detection.  Hard to argue with that logic.  

Edited by Cpk133, 14 November 2024 - 01:59 PM.

[Sebastian_Sajaroff]

On my old 6" F/8, the best magnification to observe Saturn moons was 100x (12 mm, 1.5 mm exit pupil)

Titan, Rhea, Dione and Tethys were easily visible
Japet only if it was on its "bright" side
Enceladus just a couple of times at 200x and that was during a massive power outage that plunged Quebec in darkness. My B8 backyard magically turned into B5.

[quilty]

I'm fine with just 3 of them, mostly. I think I alrady spotted 5 but 3 is the usual number.

About optimum power I think Sat moons are like stars and optimum power depends on eyesight, seeing and magnitude, too.
Those empty magnifications which help a lot at starsplitting don't work here.
My experience is, too some medium power does best at discerning dim light spots. But I'm not sure if exit pupil is the key variable here

Edited by quilty, 18 November 2024 - 10:02 AM.

[12BH7]

Last night under a partly cloudy sky I decided to use the 8". Four moons were visible almost immediately, Tethys kept popping in and out but Dione and Rhea were clear, or as clear as they get.  I "think" I saw Enceladus once, but that could  be more wishful thinking then an actual sighting.

 

When I bumped up the power it didn't help. But at least it didn't degrade the view as much as it had in the past.

 

I'm finding that with my scope has a sweet spot. Not my lowest magnification but somewhere near the middle. I find that I see the most moons using either a 19mm (105x) or 24mm (83x) Panoptic. 

Edited by 12BH7, 18 November 2024 - 09:52 AM.

[quilty]

which to me is quite a low power. About the lowest easily possible with an 8 or 9 inch with 1.25 inch ep. I didn't try too much because spotting Sat moons isn't too thrilling to me.
Might tell though a lot about seeing and scope performance.
Jupe's moons are much more inviting.

That sweet spot I always wonder if such exists for each scope or if it's just an incitenial outcome of factors like
scope, seeing, eyesight, target...

I think any scope's sweet spot for Mars is beyond 300x, yes and at starspotting (or Sat moon spotting) it might be at about 100x. Pinpointness is a key factor here.
And at above 100x stars use to change from pinpoint to star pattern/star mess* in my scopes. (the aperture of which spreads from 5 to 9 inch, thus all in a similar size category

*depends on seeing

Edited by quilty, 18 November 2024 - 10:42 AM.

[12BH7]

which to me is quite a low power. About the lowest easily possible with an 8 or 9 inch with 1.25 inch ep. I didn't try too much because spotting Sat moons isn't too thrilling to me.
Might tell though a lot about seeing and scope performance.
Jupe's moons are much more inviting.

That sweet spot I always wonder if such exists for each scope or if it's just an incitenial outcome of factors like
scope, seeing, eyesight, seeing, target...

I think any scope's sweet spot for Mars is beyond 300x, yes and at starspotting (or Sat moon spotting) it might be at about 100x. Pinpointness is a key factor here.
And at above 100x stars use to change from pinpoint to star pattern/star mess* in my scopes. (the aperture of which spreads from 5 to 9 inch, thus all in a similar size category

*depends on seeing

Yes, that sweet spot is dependent on quite a number of factors. Don't forget that eyesight is one of them.

 

Here in Arizona the seeing has been far below average the last few years. This year seems to be just a bit better, but still not it's normal level.

 

I really don't know why I go out there every night to find those moons. It's just a thing I like to do. 

[quilty]

I feel the same about Sat, Jupe and the moon. And M13, veryfy that it's complete still and no star skipped :-) And looking for the prop.
Others might tell that autistic, well, I don't mind.

Well, the moon is a different thing. there's so much left to discover to me. And all details already discerned once must be confirmed at the next opportunity.
Maybe someone removed them. Reminds me very much to an 1.5 year old baby calling Mom and Pa every once in a while in order to confirm and make sure they still exist and didn't change their names in between.

Edited by quilty, 18 November 2024 - 10:56 AM.

[Sebastian_Sajaroff]

Sky transparency and darkness are both big factors when you’re observing dim moons.

The fact of being too close to their planet (angular distance) will also affect their visibility.

Edited by Sebastian_Sajaroff, 18 November 2024 - 05:25 PM.

[quilty]

by the way, exit pupils:



find out for yourself if you prefer a large or a small one

Edited by quilty, 19 November 2024 - 05:57 AM.

[tturtle]

I saw 4 moons clearly last night at about 300x with my 9.25 SCT, Maxbright II binoviewer and a couple of .965 Takahashi 18mm barlowed eyepieces. I love seeing moons of another planet.

[azure1961p]

Well the thing is that the thrust of the purpose behind appropriate magnification augmenting the observer experience is the conduit the contrast solely around the diffraction pattern that reaches the scope is but a wanton fragment of light paths in many many directions.  That said explains why you use the magnification I stated .

 

Pete