Jump to content


Photo

Haas Double Star Book now shipping

  • Please log in to reply
27 replies to this topic

#26 fred1871

fred1871

    Viking 1

  • -----
  • Posts: 846
  • Joined: 22 Mar 2009
  • Loc: Australia

Posted 31 August 2014 - 03:21 AM

 

Last night I decided to take my new Sissy Haas book out for a spin. The transparency was 8/10 and the seeing was 6/10 on Pickering. I was using my 80mm Mayflower on a Losmandy GM-8 with Gemini 1. Observations were made with a 5mm Type 6 Nagler with TFOV of 20.5’ and a magnification of 240X. The GoTo’s were putting the objects in the FOV of the eyepiece each time, so it promised to be a good night.

 

aside from calling out bob's individual star observation reports, which are well done in an informal style, i wanted to point out that he's working at an exit pupil of 0.33 mm, which is also my favorite for close systems.

 

planetary astronomers sometimes try out that double star thing, set up with their usual 2 mm exit pupil, and wonder what all the fuss is about.

 

and ... oh, yes ... double star astronomy with an accurate GoTo system? -- priceless.

 

Bruce, an exit pupil of 0.33mm is what I use for the very tighest systems with 140mm aperture, but I certainly don't use it for everything.

Many doubles separate with less power, and many of them look better with less.

 

Regarding planetary observing - back in the day when I did this with a 10-inch Newtonian, I did not use ~125x (2mm exit pupil) - common magnifications were more likely 250x - 360x with that aperture, exit pupils of 1.0mm to 0.7mm. With a 9-inch refractor on Mars (1980s oppositions), 400x was about right (0.6mm) on the better nights (560x occasionally - 0.4mm exit pupil). 

 

Saturn with a 7-inch apo - 180x -360x (1.0mm to 0.5mm). With my current 140mm refractor, Jupiter is best in the 120x-200x range (1.17-0.7mm exit pupil); Mars will take more power, 230x is good (0.6mm).

 

Overall ? - magnifications I used were similar to those other experienced observers used. And not a lot different from what I use on double stars, though on doubles I do go higher when needing more apparent size, something that can be done with points of light more readily than with contrast features.



#27 drollere

drollere

    Apollo

  • *****
  • Posts: 1498
  • Joined: 02 Feb 2010
  • Loc: sebastopol, california

Posted 31 August 2014 - 02:22 PM

fred, you should understand that you make me weep when you talk about submil exit pupils on planets. i almost never have seeing here along the north california coast that allows such impudence.

 

even so, i've been toured around the planets by other people showing off their scopes, and your standards are unusual in my experience. (but again, most of them also live out my way.)

 

and you're right, as i said ... i use 0.33 (or less) "for close systems".



#28 rcwolpert

rcwolpert

    Viking 1

  • *****
  • Posts: 793
  • Joined: 13 Aug 2012
  • Loc: San Jose, CA

Posted Yesterday, 02:08 PM

 

Last night I decided to take my new Sissy Haas book out for a spin. The transparency was 8/10 and the seeing was 6/10 on Pickering. I was using my 80mm Mayflower on a Losmandy GM-8 with Gemini 1. Observations were made with a 5mm Type 6 Nagler with TFOV of 20.5’ and a magnification of 240X. The GoTo’s were putting the objects in the FOV of the eyepiece each time, so it promised to be a good night.

 

aside from calling out bob's individual star observation reports, which are well done in an informal style, i wanted to point out that he's working at an exit pupil of 0.33 mm, which is also my favorite for close systems.

 

planetary astronomers sometimes try out that double star thing, set up with their usual 2 mm exit pupil, and wonder what all the fuss is about.

 

and ... oh, yes ... double star astronomy with an accurate GoTo system? -- priceless.

 

 

Thanks for the comments, Bruce.  Since I made those Aug 17th observations, I've been in the process of moving my household to two different locations - one on the east coast of Florida, and one here in the San Jose, CA area. Just for the record, I would not recommend this type of move to anyone. It's been one heck of a month, and I miss those double stars!  All my telescopes and mounts went to the Florida location except for the 80mm Mayflower, which will now operate on it's own mount, so I can kiss the GoTo's good-bye for a while. It's back to star-hopping, which has it's own rewards, but on the really positive side, I'm now using a transportable set-up and will be observing from much darker sites.

Back to the exit pupils, while the 0.33 is also my favorite for close systems (and some not-so-close), I do use several different eyepieces depending on what's being observed and the quality of the night. Unfortunately, I still need to meet the moving van on the Florida end of the trip, so it might be another 2-3 weeks before getting back to observing and using the Haas book. I'm having serious double star withdrawal symptoms!

 

- Bob








Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics