Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Io transit and shadow with 150mm Mak-Cass

  • Please log in to reply
16 replies to this topic

#1 ny65

ny65

    Mariner 2

  • -----
  • topic starter
  • Posts: 252
  • Joined: 03 Aug 2020
  • Loc: Ithaca, NY, USA

Posted 12 September 2021 - 03:47 PM

I have been having a ball with my recently acquired Orion 150mm Mak-Cass and enjoying beautiful views of Jupiter and its moons (covered in this thread). Last night, I was trying to catch Io in transit across Jupiter and also its shadow on the planet's disk. Unlike Ganymede and Callisto, observing Io's transit was pretty much impossible with my scope (I was using a Celestron/Agena 8-24mm Zoom EP). I was able to catch its shadow transit across Jupiter, but even that somewhat tenuously. Obviously Io is a fair bit smaller than Ganymede, so I expect it to be harder to discern. I was wondering whether something like Io's transit "should be" easily visible with my scope and EP. The seeing conditions were not spectacular but not terrible either - probably average to slightly less than average perhaps. Am I being too ambitious in trying to see Io's transity clearly with my scope/EP?


Edited by ny65, 12 September 2021 - 04:49 PM.

  • RiderRoy likes this

#2 ngc7319_20

ngc7319_20

    Vanguard

  • *****
  • Posts: 2,412
  • Joined: 25 Oct 2015
  • Loc: MD

Posted 12 September 2021 - 03:58 PM

Io's shadow should be easy with a 150mm.  I watched it last night with 70mm binos.    But Io itself would be difficult -- I've seen it with an 11" but nothing smaller.


  • ny65 likes this

#3 ny65

ny65

    Mariner 2

  • -----
  • topic starter
  • Posts: 252
  • Joined: 03 Aug 2020
  • Loc: Ithaca, NY, USA

Posted 12 September 2021 - 04:48 PM

Io's shadow should be easy with a 150mm.  I watched it last night with 70mm binos.    But Io itself would be difficult -- I've seen it with an 11" but nothing smaller.

Thank you. I think your eyes may be far better than mine laugh.gif - I cannot see anything close to that with my binos! Io's shadow wasn't too bad - I think the seeing last night may have been slightly worse than average. I will try using my 80A blue filter to see if it helps things.

 

Based on your feedback having not seen it with something smaller than a 11", I don't hold out much hope with my 6" Mak. I will keep trying though; perhaps one of these nights seeing is great and I luck out!



#4 ngc7319_20

ngc7319_20

    Vanguard

  • *****
  • Posts: 2,412
  • Joined: 25 Oct 2015
  • Loc: MD

Posted 12 September 2021 - 05:37 PM

Thank you. I think your eyes may be far better than mine laugh.gif - I cannot see anything close to that with my binos! Io's shadow wasn't too bad - I think the seeing last night may have been slightly worse than average. I will try using my 80A blue filter to see if it helps things.

 

Based on your feedback having not seen it with something smaller than a 11", I don't hold out much hope with my 6" Mak. I will keep trying though; perhaps one of these nights seeing is great and I luck out!

Well I was watching Io's shadow with 70mm ED binos at 100x... the 100x helps...  :)

 

As for 150mm Mak -- You might have a chance when Io first enters the disk of Jupiter... or is just departing... Jupiter is dim at the limb and there is some contrast.  But when Io is in the middle of the disk there is very little contrast and it is very difficult.


Edited by ngc7319_20, 12 September 2021 - 05:37 PM.

  • ny65 likes this

#5 ny65

ny65

    Mariner 2

  • -----
  • topic starter
  • Posts: 252
  • Joined: 03 Aug 2020
  • Loc: Ithaca, NY, USA

Posted 12 September 2021 - 06:16 PM

Well I was watching Io's shadow with 70mm ED binos at 100x... the 100x helps...  smile.gif

 

As for 150mm Mak -- You might have a chance when Io first enters the disk of Jupiter... or is just departing... Jupiter is dim at the limb and there is some contrast.  But when Io is in the middle of the disk there is very little contrast and it is very difficult.

Haha, I don't feel so bad about my eyesight now (though it is nothing to write home about!)

 

Thanks for the hint about catching it when it enters or leaves the disk of Jupiter. I have been able to see it just after it emerges from the disk but I will look for it as it is just on the edge.



#6 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 18,967
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 12 September 2021 - 06:36 PM

I suppose your seeing conditions were not as good as the night you observed Ganymede's shadow. Ganymede's shadow is, of course, gonna be larger, but I'm not sure it's really all that noticeable at such a great distance. Both should be very dark and circular, they should look similar. Very importantly, the shadows are very high contrast so Io's shadow should be easily seen as well. Given a chance in good seeing, your 150 MCT is very capable of seeing the shadow. Give it another try on another night. I agree, Io's disc is easier near Jupiter's limb and much more difficult, if not impossible in most cases, near Jupiter's meridian. It's a low contrast problem against the brighter clouds.
  • ny65 likes this

#7 ny65

ny65

    Mariner 2

  • -----
  • topic starter
  • Posts: 252
  • Joined: 03 Aug 2020
  • Loc: Ithaca, NY, USA

Posted 12 September 2021 - 07:33 PM

I suppose your seeing conditions were not as good as the night you observed Ganymede's shadow. Ganymede's shadow is, of course, gonna be larger, but I'm not sure it's really all that noticeable at such a great distance. Both should be very dark and circular, they should look similar. Very importantly, the shadows are very high contrast so Io's shadow should be easily seen as well. Given a chance in good seeing, your 150 MCT is very capable of seeing the shadow. Give it another try on another night. I agree, Io's disc is easier near Jupiter's limb and much more difficult, if not impossible in most cases, near Jupiter's meridian. It's a low contrast problem against the brighter clouds.

Thanks. That was one thing that occurred to me as well since Ganymede is just ~1.5x Io's size. I do think that seeing wasn't quite that good, at least when I got to see the shadow (it was fluctuating quite a bit). I will try another night and also look for Io on Jupiter's limb.


  • Asbytec likes this

#8 DAG792

DAG792

    Mariner 2

  • -----
  • Posts: 283
  • Joined: 21 Mar 2020

Posted 12 September 2021 - 10:52 PM

I have been having a ball with my recently acquired Orion 150mm Mak-Cass and enjoying beautiful views of Jupiter and its moons (covered in this thread). Last night, I was trying to catch Io in transit across Jupiter and also its shadow on the planet's disk. Unlike Ganymede and Callisto, observing Io's transit was pretty much impossible with my scope (I was using a Celestron/Agena 8-24mm Zoom EP). I was able to catch its shadow transit across Jupiter, but even that somewhat tenuously. Obviously Io is a fair bit smaller than Ganymede, so I expect it to be harder to discern. I was wondering whether something like Io's transit "should be" easily visible with my scope and EP. The seeing conditions were not spectacular but not terrible either - probably average to slightly less than average perhaps. Am I being too ambitious in trying to see Io's transity clearly with my scope/EP?

A 150 mm telescope is a very capable scope in excellent conditions. It can even resolve albedo differences on Ganymede. 

If you had a problem seeing Io's shadow, your scope was either not acclimatized or collimated. It could also be that your seeing conditions were bad, but you need to have really, really bad seeing before it becomes hard to see Io's shadow.

I would suspect the collimation.


  • ny65 likes this

#9 ny65

ny65

    Mariner 2

  • -----
  • topic starter
  • Posts: 252
  • Joined: 03 Aug 2020
  • Loc: Ithaca, NY, USA

Posted 12 September 2021 - 11:02 PM

A 150 mm telescope is a very capable scope in excellent conditions. It can even resolve albedo differences on Ganymede. 

If you had a problem seeing Io's shadow, your scope was either not acclimatized or collimated. It could also be that your seeing conditions were bad, but you need to have really, really bad seeing before it becomes hard to see Io's shadow.

I would suspect the collimation.

Thank you.

 

I was able to see Ganymede's shadow pretty well along with its transit and also Callisto's transit a bit back. So, I don't think it is the telescope per se. I also did a star test and it seemed to be pretty good (though this is my first time doing this and I could have been botching it). Also, since it is a Mak-Cass I was expecting that it should hold its factory collimation pretty well (I got the scope just a month back).

 

So, I think the seeing may have been poor. I checked cleardarksky.com and it indicated that the seeing was poor last night (2/5) in my area. I will try again the next time skies are clear and Io is transiting.

 

I will do another star test to check whether collimation is good - I am loath to fiddle with collimation since I don't want to break something that doesn't need fixing, but if it is out of collimation will certainly give it a go.


Edited by ny65, 12 September 2021 - 11:07 PM.


#10 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 18,967
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 13 September 2021 - 05:44 AM

It can even resolve albedo differences on Ganymede. 

 

waytogo.gif 

 

Unbelievable, but true. With a well collimated and thermally stable scope in very good seeing, of course. A little magnification helps, it's easier on the eye. 


  • DAG792 and ny65 like this

#11 ny65

ny65

    Mariner 2

  • -----
  • topic starter
  • Posts: 252
  • Joined: 03 Aug 2020
  • Loc: Ithaca, NY, USA

Posted 13 September 2021 - 08:52 AM

waytogo.gif

 

Unbelievable, but true. With a well collimated and thermally stable scope in very good seeing, of course. A little magnification helps, it's easier on the eye. 

It may be a bridge too far for me right now, but I will watch for this; would be a really cool thing to see...


  • Asbytec likes this

#12 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 18,967
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 13 September 2021 - 10:10 AM

It may be a bridge too far for me right now, but I will watch for this; would be a really cool thing to see...

Yes, it is a cool thing. I never would have thought it possible until I was prodded by an old friend to at least try it for myself. One night when conditions were right (nearly perfect) and Ganymede happened to display a bright "speck" crater (Osiris on Ganymede's limb) toward Earth, it took some time to realize (and verify on JPL sim) such a thing certainly is possible in a modest aperture. Take your time. Get to know your scope, your conditions, and yourself (skills). It'll come. smile.gif


Edited by Asbytec, 13 September 2021 - 10:11 AM.

  • payner and ny65 like this

#13 ny65

ny65

    Mariner 2

  • -----
  • topic starter
  • Posts: 252
  • Joined: 03 Aug 2020
  • Loc: Ithaca, NY, USA

Posted 13 September 2021 - 10:36 AM

Yes, it is a cool thing. I never would have thought it possible until I was prodded by an old friend to at least try it for myself. One night when conditions were right (nearly perfect) and Ganymede happened to display a bright "speck" crater (Osiris on Ganymede's limb) toward Earth, it took some time to realize (and verify on JPL sim) such a thing certainly is possible in a modest aperture. Take your time. Get to know your scope, your conditions, and yourself (skills). It'll come. smile.gif

Thanks for the encouragement - much appreciated!

 

I didn't know about JPL Sim - found it via Google after your post. It will be quite handy - thanks.


  • Asbytec likes this

#14 REC

REC

    Voyager 1

  • *****
  • Posts: 12,254
  • Joined: 20 Oct 2010
  • Loc: NC

Posted 13 September 2021 - 01:03 PM

I saw it last night in my 4" Frac and it was pretty dim, but the black spot was there, in and out at 100x. Seeing conditions are very important. Here in NC we had very good skies, 4/5 on seeing conditions. Not much going on tonight on Jove.

 

How is a star test? Try a fairly bright star and see if you can get a fine point of light on it. Then just go to Jupiter and don't focus it again after the focused star.


  • ny65 likes this

#15 ny65

ny65

    Mariner 2

  • -----
  • topic starter
  • Posts: 252
  • Joined: 03 Aug 2020
  • Loc: Ithaca, NY, USA

Posted 13 September 2021 - 01:51 PM

I saw it last night in my 4" Frac and it was pretty dim, but the black spot was there, in and out at 100x. Seeing conditions are very important. Here in NC we had very good skies, 4/5 on seeing conditions. Not much going on tonight on Jove.

 

How is a star test? Try a fairly bright star and see if you can get a fine point of light on it. Then just go to Jupiter and don't focus it again after the focused star.

Thank you. I could see the shadow itself (though not quite stably) but the transit was not visible. Your seeing is much better than what I had the night in question - 2/5 at my location.

 

Thanks for the tip re: using a bright star as a focus and then moving it to Jupiter while retaining the focus state. I will try this. I don't think focus itself is an issue since I have gotten fairly good in tweaking this in fine increments though it is quite sensitive and defocuses if I as much as touch the telescope.



#16 YossiZ

YossiZ

    Mariner 2

  • -----
  • Posts: 220
  • Joined: 21 Mar 2021

Posted 18 September 2021 - 05:59 AM

I have been having a ball with my recently acquired Orion 150mm Mak-Cass and enjoying beautiful views of Jupiter and its moons (covered in this thread). Last night, I was trying to catch Io in transit across Jupiter and also its shadow on the planet's disk. Unlike Ganymede and Callisto, observing Io's transit was pretty much impossible with my scope (I was using a Celestron/Agena 8-24mm Zoom EP). I was able to catch its shadow transit across Jupiter, but even that somewhat tenuously. Obviously Io is a fair bit smaller than Ganymede, so I expect it to be harder to discern. I was wondering whether something like Io's transit "should be" easily visible with my scope and EP. The seeing conditions were not spectacular but not terrible either - probably average to slightly less than average perhaps. Am I being too ambitious in trying to see Io's transity clearly with my scope/EP?

I use a SW 150mm Mak so what I managed to see might give you an idea.
Last night I saw a "shadow" and didn't remember that there was supposed to be one. Checking in Skysafari, I realized that it was Callisto itself transiting. Callisto is relatively dark in its colors and I guess this is why it was easily visible on the background of Jupiter in magnifications between 110 and 220, with average or a little more than average seeing.
In August there was a double transit of Europa and Ganymede. I could see both shadows and Ganymede, but couldn't see Europa. Again Ganymede is relatively dark but Europa is smaller and has brighter colors probably similar to the background. I guess I used a magnification of 220 or 270.
I don't remember watching a transit of Io visually, but I took the attached image and animation of images in two different occasions. I think it might be possible visually in excellent conditions only, and maybe not against yellow-orange background.

2021 08 21 2221 7 CapObj lapl4 ap225 RS Bal wav2


JUP animation2 pipp

Edited by YossiZ, 18 September 2021 - 12:25 PM.

  • payner, Jaimo! and ny65 like this

#17 ny65

ny65

    Mariner 2

  • -----
  • topic starter
  • Posts: 252
  • Joined: 03 Aug 2020
  • Loc: Ithaca, NY, USA

Posted 18 September 2021 - 09:03 AM

I use a SW 150mm Mak so what I managed to see might give you an idea.
Last night I saw a "shadow" and didn't remember that there was supposed to be one. Checking in Skysafari, I realised that it was Callisto itself transiting. Callisto is relatively dark in its colors and I guess this is why it was easily visible on the background of Jupiter in magnifications between 110 and 220, with average or a little more than average seeing.
In August there was a double transit of Europa and Ganymede. I could see both shadows and Ganymede, but couldn't see Europa. Again Ganymede is relatively dark but Europa is smaller and has brighter colors probably similar to the background. I guess I used a magnification of 220 or 270.
I don't remember watching a transit of Io visually, but I took the attached image and animation of images in two different occasions. I think it might be possible visually in excellent conditions only, and maybe not against yellow-orange background.


 

Thanks for your comments, YossiZ, and the beautiful images - they are quite stunning! I may get some hints on how to do astrophotography based on your gear...

 

I happened to see Callisto's shadow on Jupiter last night as well but the moon itself was already outside Jupiter's disk by the time I started viewing. I will try to catch Europa's transit; it may be hard since it will be similar to Io, I think. I have been using a #80A color filter recently and it does seem to help improve the view, but I haven't used it yet to catch the transits.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics