#1  
Old 01-08-2019, 07:50 AM
The Mekon's Avatar
The Mekon (John Briggs)
Registered User

The Mekon is offline
 
Join Date: Jul 2007
Location: Bowral NSW
Posts: 677
Ophiuchus doubles / Saturn

Last night observing conditions where I live were superb. Had the 18” out on the back lawn, and after alignment, I usually check by sending the scope to a bright object. Antares was that first target, and with the 7” mask fitted the companion was exceptionally distinct and well separated in the 9mm Nagler at 259x. I had the feeling the night would be really good.
After some globular chasing, I set the scope on Saturn. Now in all my years of observing, I have never claimed the Enke division. But at 259x, there appeared some detail in the outer sections of the ring system beyond the Cassini division. Putting in a 7mm, power now 334x revealed a fine black band near the edge of the ring system. Enke! The crepe ring was also seen well.
Now for some double stars in Ophiuchus. Lambda is always one of my favourites and sure enough there was a river of darkness between the two close stars at 259x
On to 21 Oph. Never seen this split before, but at 259x I could detect the lesser mag companion close up to the primary. Increasing to 334x and this one was in the bag. (and in the log book) Stelledoppie has this pair at mags 5.8/7.3 0.76”
Eta Oph always been out of reach. I was unaware of the PA at the start of the observation, but saw certain elongation in PA 060/240. Checking the records this star is an even double at 0.5” and PA 232.
All up a great night. My backyard is getting more and more subject to local light pollution, but observing double stars is thankfully not affected yet.
I would welcome and comments from others who may have enjoyed the great conditions last night.

Last edited by The Mekon; 01-08-2019 at 03:47 PM.
Reply With Quote
  #2  
Old 01-08-2019, 02:48 PM
bigjoe's Avatar
bigjoe (Joe)
Registered User

bigjoe is offline
 
Join Date: Nov 2010
Location: sydney
Posts: 1,302
Good night of observing John..I'll look tonight..Seems Lambda Ophiuchi is also a triple with a companion of mag 11 only 2' away

At 1.4" Lambda Ophiuchi AB is tough needs good seeing..though done it before..it's not far in between the Superb Alpha Herculis and Jupiter, and not far from brilliant Yellow /RED Xi Bootis a fav of mine to show others.

Cracked brilliant white Beta Muscae last night at .8" Mags AB: 3.1,4 with 925 SCT and 5 Delite at 470x and using BAADER T2 PRISM diagonal, then had some other duties to attend to..

Will check seeing out tonight.
Cheers Bigjoe.

Last edited by bigjoe; 01-08-2019 at 03:30 PM.
Reply With Quote
  #3  
Old 02-08-2019, 12:23 AM
bigjoe's Avatar
bigjoe (Joe)
Registered User

bigjoe is offline
 
Join Date: Nov 2010
Location: sydney
Posts: 1,302
Re doubles.

Too cloudy in Sydney or Penrith area to try.. seeing only passable thursday..Will try again Friday.
Bigjoe.
Reply With Quote
  #4  
Old 02-08-2019, 07:15 AM
Rainmaker (Matt)
Excalibur Industries.....

Rainmaker is offline
 
Join Date: Jun 2019
Location: Canberra
Posts: 61
Quote:
Originally Posted by The Mekon View Post
Last night observing conditions where I live were superb. Had the 18” out on the back lawn, and after alignment, I usually check by sending the scope to a bright object. Antares was that first target, and with the 7” mask fitted the companion was exceptionally distinct and well separated in the 9mm Nagler at 259x. I had the feeling the night would be really good.
After some globular chasing, I set the scope on Saturn. Now in all my years of observing, I have never claimed the Enke division. But at 259x, there appeared some detail in the outer sections of the ring system beyond the Cassini division. Putting in a 7mm, power now 334x revealed a fine black band near the edge of the ring system. Enke! The crepe ring was also seen well.
Now for some double stars in Ophiuchus. Lambda is always one of my favourites and sure enough there was a river of darkness between the two close stars at 259x
On to 21 Oph. Never seen this split before, but at 259x I could detect the lesser mag companion close up to the primary. Increasing to 334x and this one was in the bag. (and in the log book) Stelledoppie has this pair at mags 5.8/7.3 0.76”
Eta Oph always been out of reach. I was unaware of the PA at the start of the observation, but saw certain elongation in PA 060/240. Checking the records this star is an even double at 0.5” and PA 232.
All up a great night. My backyard is getting more and more subject to local light pollution, but observing double stars is thankfully not affected yet.
I would welcome and comments from others who may have enjoyed the great conditions last night.
Thanks for the excellent observing report John, I am hoping for some clear skies tomorrow night, we have a dark sky night planned at Bellmount Forest.
I am taking the 18" and a 4"F8...

Might even cut an off-axis mask to try out.....
Reply With Quote
  #5  
Old 02-08-2019, 08:17 AM
The Mekon's Avatar
The Mekon (John Briggs)
Registered User

The Mekon is offline
 
Join Date: Jul 2007
Location: Bowral NSW
Posts: 677
Quote:
Originally Posted by Rainmaker View Post
Thanks for the excellent observing report John, I am hoping for some clear skies tomorrow night, we have a dark sky night planned at Bellmount Forest.
I am taking the 18" and a 4"F8...

Might even cut an off-axis mask to try out.....
Have great night Matt. The optics of your 18" are superb, but a mask can help fore even the best of scopes!
Reply With Quote
  #6  
Old 02-08-2019, 09:09 PM
ngcles's Avatar
ngcles
The Observologist

ngcles is offline
 
Join Date: Dec 2006
Location: Billimari, NSW Central West
Posts: 1,543
Hi John & All,

Interesting post John. Were you still using the 7" mask when you observed the Encke Division or was it full aperture (I'm assuming the latter)?

The fact that it is the first time in a long observing career you, as a very experienced telescope user, have seen the Encke division shows just how difficult and how elusive a target it truly is.

Personally, I've only certainly seen it twice in almost 50 years behind (or beside) a telescope.

Best,

L.
Reply With Quote
  #7  
Old 03-08-2019, 08:00 AM
The Mekon's Avatar
The Mekon (John Briggs)
Registered User

The Mekon is offline
 
Join Date: Jul 2007
Location: Bowral NSW
Posts: 677
Thanks for your comments Les.

Observation at full aperture. My mask is very easy to put on and off the scope, being held in place by two small Velcro patches. I keep it handy to flip on and off at will.

The Encke division (or more commonly "Encke Gap") was seen only near the vertex of the ring system - the best place to pick it out.
I did a quick google to find out what telescope Encke first observed the gap with but failed to find this out. I note some observers on Cloudy nights claim to have seen it in as small an aperture as 8" !!
Reply With Quote
  #8  
Old 03-08-2019, 08:28 AM
Rainmaker (Matt)
Excalibur Industries.....

Rainmaker is offline
 
Join Date: Jun 2019
Location: Canberra
Posts: 61
Quote:
Originally Posted by The Mekon View Post
Thanks for your comments Les.

Observation at full aperture. My mask is very easy to put on and off the scope, being held in place by two small Velcro patches. I keep it handy to flip on and off at will.

The Encke division (or more commonly "Encke Gap") was seen only near the vertex of the ring system - the best place to pick it out.
I did a quick google to find out what telescope Encke first observed the gap with but failed to find this out. I note some observers on Cloudy nights claim to have seen it in as small an aperture as 8" !!
I expect that many are confusing the Encke Minima with the Encke Division.
I have seen the Minima in several scopes and thought I saw a hint of the Encke Division in the TEC 200 Maksutov but couldn't really claim it .....

I have seen it for certain just once in each of my 18" Dobs from the rural skies near Coonabarabran. It really is very elusive. Trying again tonight....
Reply With Quote
  #9  
Old 03-08-2019, 10:29 AM
ngcles's Avatar
ngcles
The Observologist

ngcles is offline
 
Join Date: Dec 2006
Location: Billimari, NSW Central West
Posts: 1,543
Encke gap?

Hi Rainmaker, John & All,

Quote:
Originally Posted by Rainmaker View Post
I expect that many are confusing the Encke Minima with the Encke Division.
I have seen the Minima in several scopes and thought I saw a hint of the Encke Division in the TEC 200 Maksutov but couldn't really claim it .....

I have seen it for certain just once in each of my 18" Dobs from the rural skies near Coonabarabran. It really is very elusive. Trying again tonight....
Yes this issue was the subject of some discussion here during the last apparition of Saturn in 2018:

http://www.iceinspace.com.au/forum/s...d.php?t=168492

Let's remember the gap was first observed by James Keeler (for whom the even thinner Keeler gap is named) using the 36" refractor at Lick Observatory. It is only 325km wide (less than 1/10th the size of the Cassini Division)and has an angular diameter of about 0.05 arc-seconds when viewed from Earth. The Cassini Divison is about 0.8 arc-seconds

I feel that many claiming to see the Encke gap through relatively modest telescopes (ie 25cm and less) are mistaking the Encke minima (a broader trough in surface brightness of Saturn's "A" ring) for the actual gap that is very close to the edge of the A ring.

While I'm happy to concede it is possible to observe high-contrast features like the Encke gap in instruments where the angular diameter of the gap is less than the Dawes Limit (see my "Observable -v- Resolvable" post in the other thread), seeing features approximately 1/16th the Dawes limit (or less) just isn't possible. I would be very sceptical of claims it is truly observable in telescopes less than about 25-30cm aperture. This is consistent with my own experience, yours and John's -- it is a very, very difficult feature to see, only occasionally observable in large amateur instruments. As I said elsewhere, I've seen it with certainty twice -- once with 31cm at x367 on a night of exceptional seeing in 2000 and again about 3 years ago with 46cm at x464 on a night of almost singular seeing at Mudgee. On that night, this dedicated deep sky observer and a number of others spent about 4 hours going from Mars to Jupiter to Saturn over and over at powers of x462 to over x550 with 46 and 50cm telescopes and sometimes not seeing the merest quiver in the eyepiece image for 30-40 seconds at a time.

That's not for one minute saying people are lying or falsifying their observations, but simply characterise such claims as probably spurious observations or mistakes. The so called "canals" on Mars are an excellent example.

We all make mistakes. I know, I've certainly made my share of 'em.


Best,

L.

Last edited by ngcles; 03-08-2019 at 11:00 AM.
Reply With Quote
  #10  
Old 06-08-2019, 11:46 AM
Rainmaker (Matt)
Excalibur Industries.....

Rainmaker is offline
 
Join Date: Jun 2019
Location: Canberra
Posts: 61
Quote:
Originally Posted by The Mekon View Post
Have great night Matt. The optics of your 18" are superb, but a mask can help fore even the best of scopes!
Alas even superb optics could not see through the thick clouds that rolled in at dusk..... instead we retired to the motorhome for a cuppa and chat...

It sure is an elusive little gap, I might have to go to Coolah for some serious aperture
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 06:45 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Meade Australia
Advertisement
NexDome Observatories
Advertisement
SkyWatcher Australia
Advertisement
OzScopes Authorised Dealer
Advertisement
Celestron Australia
Advertisement
Lunatico Astronomical
Advertisement
Astronomy and Electronics Centre
Advertisement