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Some Doubles in Cassiopeia

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#1 Rustler46

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Posted 09 November 2019 - 01:15 AM

My short-term goal for double star observing is to examine some pairs in Cassiopeia. This constellation will be well placed for the next few months. While Burnham's Celestial Handbook has over 100 pairs listed, I used Sissy Haas' book to pare that down to a more manageable 40. If I go for no more than 10 pairs per night, this will provide several nights' enjoyment. Nowadays my method for finding any celestial object is to make use of a go-to mount. Decades of using a star atlas and finder scope has lost its allure for an aging body. To control my G-11 mount I'll be using my iPad Mini running SkySafari-6 Pro with the Cassiopeia observing list.

 

My observations will be made by describing in words what is seen, making use use of a digital voice recorder. Sometimes this is difficult when the surrounding field is complex. I may try sketching or photographing the more interesting ones. For sketching colorful pairs I'm looking forward to using a method shared by frank5817. That involves pencil on white paper with stars colored with the complementary color. That way when the sketch is inverted to form white stars on black background, a star sketched with blue will appear as red. Some adjustments in Photoshop may be used to match what was seen.

 

My current telescopes of choice, a Celestron-11 and an AT115EDT refractor, will provide an interesting contrast. Now all that's missing is a clear night when I'm free to enjoy these double stars. Thanks to Aubrey for highlighting Cassiopeia!

 

C-11 & AT115EDT On G-11 Mount-1.jpg

 

Best Regards,

Russ


Edited by Rustler46, 09 November 2019 - 09:49 PM.

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#2 Astro-Master

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Posted 09 November 2019 - 01:57 AM

Sounds like a good project, be sure to check out Iota Cass. my favorite triple in Cass.  Looks like you have a nice setup with the 11"SCT and the AT115mm on the G-11, how well does the mount handle the load?

 

I have a 180mm Intes Mak-Cass and a Stellarvue 105mm APO, I should try mounting them together on my CGEM II.


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#3 Rustler46

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Posted 09 November 2019 - 02:50 AM

Sounds like a good project, be sure to check out Iota Cass. my favorite triple in Cass.  Looks like you have a nice setup with the 11"SCT and the AT115mm on the G-11, how well does the mount handle the load?

 

I have a 180mm Intes Mak-Cass and a Stellarvue 105mm APO, I should try mounting them together on my CGEM II.

Yeah, Iota Cas has been a target of mine on 4 different nights - 2 with a 10-inch Newt and 2 with the C-11. It's a nice, colorful triple variously showing:

  • greenish (3rd component)
  • white/golden 
  • yellow/reddish/gray
  • yellow/reddish/bluish

This shows how color perception is quite variable from night to night and with different telescopes. Strangely the bright primary of spectral type A3 is actually bluer than its two companions of spectral types F5 and G7. But the observer's perception of color is what it is.

 

For visual use the Losmandy G-11 handles the C-11/AT115EDT combo quite well. It must be pushing 50 lbs. payload, though I believe the mount has a 60 lb. limit. There must be around 40 lbs. of counterweights. So careful balance is necessary. I've also used a C-8/115 APO combo with the same mount.

 

Your Mak/APO would provide a nice comparison. I've found at times the larger scope's light-gathering and resolution is an advantage with doubles. Other times the smaller APO gives the better view.

 

Russ


Edited by Rustler46, 09 November 2019 - 03:25 AM.

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#4 fred1871

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Posted 09 November 2019 - 07:05 AM

Yeah, Iota Cas has been a target of mine on 4 different nights - 2 with a 10-inch Newt and 2 with the C-11. It's a nice, colorful triple variously showing:

  • greenish (3rd component)
  • white/golden 
  • yellow/reddish/gray
  • yellow/reddish/bluish

This shows how color perception is quite variable from night to night and with different telescopes. Strangely the bright primary of spectral type A3 is actually bluer than its two companions of spectral types F5 and G7. But the observer's perception of color is what it is.

 

Hmmm... I'd expect spectrum A3 (white, perhaps a hint of blue) to be "bluer" than types F5 (light yellow) and G7 (deep yellow, perhaps hinting orange?). Of course, differing colours affect our perceptions through contrast  when observed together ....

 

And sometimes a warm colour in a star that's not bright enough - with the scope being used - to stimulate colour vision properly, can approach the "all cats are grey in the dark" effect, and grey can suggest bluish. Colour vision is, I'd agree, not as predictable as might be expected.


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#5 Rustler46

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Posted 09 November 2019 - 08:03 PM

Hmmm... I'd expect spectrum A3 (white, perhaps a hint of blue) to be "bluer" than types F5 (light yellow) and G7 (deep yellow, perhaps hinting orange?). Of course, differing colours affect our perceptions through contrast  when observed together ....

 

And sometimes a warm colour in a star that's not bright enough - with the scope being used - to stimulate colour vision properly, can approach the "all cats are grey in the dark" effect, and grey can suggest bluish. Colour vision is, I'd agree, not as predictable as might be expected.

Here's a bit of research I did on Iota Cassiopeia, using some references available. The colors reported for the A, B & C components are:

  • Yellow/lilac/blue (Celestial Objects for Common Telescopes, Vol. II, Web, 1859)
  • Yellow/blue/blue (Field Book of the Skies, Olcott & Mayall, 1954)
  • White/white/orange (Stars - Iota Cas, Kaler, 2004)
  • Lemon-yellow/blue/  (double stars for small telescopes, Haas, 2006)

It's interesting on Professor Kaler's Stars Website, the page for Iota Cassiopeia lists the spectral types as:

  • Iota-A - A5 peculiar
  • Iota-B - F5
  • Iota-C - K1

He notes for colors:

  • "While A and B are both white and fairly colorless, C is on the orange side."

 

SkySafari lists the spectral types as A3, F5 & G7, with colors of white, yellow-white and yellow (or blue).

 

So colors and spectral types of the components are different in different sources. The Stars - Iota Cas article is an interesting read. There are so many fascinating things to learn about the doubles we observe.


Edited by Rustler46, 09 November 2019 - 11:08 PM.


#6 Rustler46

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Posted Yesterday, 02:18 AM

Of the 40 pairs in the Haas book that were also in the SkySafari Doubles observing list, 12 had previously been observed. So in leu of a clear night, I’ll report previous observations:

 

Σ 3053 - 5.8/7.2 magnitudes @ 15.2 arc-seconds

  • Yellow-orange and bluish, well separated - (AT115EDT @ 73X)
  •  Golden-yellow & definite blue - (C-11 @ 160X)

Σ 3057 - 6.7/9.3 magnitudes @ 3.8 arc-seconds

  • Yellowish? primary, plenty of separation, huge brightness contrast - (AT115EDT @ 160X)

Σ 3062 - 6.4/7.3 magnitudes @ 1.5 arc-seconds

  • Secondary reddish, some separation, large brightness contrast - (AT115EDT @ 320X)
  • Elongated, notched sometimes separate stars nearly in contact - (C-11 @ 160X)

Σ 10 - 8.0/8.6 magnitudes @ 17.5 arc-seconds

  • Good separation, no color apparent, 11th mag. C component @ 55 arc-second - (AT115EDT @ 73X)

Σ 16 - 7.6/8.8 magnitudes @ 5.9 arc-seconds

  • Reddish? secondary, some separation, large brightness contrast - (AT115EDT @ 146X)
  • Yellowish primary, secondary just looks dim - (C-11 @ 160X)

Σ 48 - 7.8/8.0 magnitudes @ 5.4 arc-seconds

  • 11 & 12 mag. companions @ ~30" forming equilateral triangle w/ first pair - (C-11 @ 255X)

Σ 170 – 7.0/8.2 magnitudes @ 3.2 arc-seconds

  • White/reddish? - (C-11 @ 255X)

Sigma Cassiopeiae - 5.0/7.2 magnitudes @ 3.0 arc-seconds

  • White/yellow?, well separated - (C-11 @ 255X)
  • White/bluish, tight pair, unequal - (C-11 @ 255X)

Alpha Cassiopeiae – 2.3/9.0 magnitudes @ 71 arc-seconds

  • Nice brightness contrast; easy, well-separated - (C-11 @ 67X)
  • Nice wide, contrasting pair; yellow/white - (C-11 @ 255X)

Eta Cassiopeiae - 3.5/7.4 magnitudes @ 13.4 arc-seconds

  • Colors variously described as yellow/red, yellow/rust-red, white/reddish & yellow/reddish-brown - (10-inch Newtonian @ 60-120X on 4 different nights)

Gamma Cassiopeiae - 2.2/10.9 mags. @ 2.1 arc-seconds

  • Sometimes can see a little 11th magnitude secondary tucked in there pretty close, lively seeing, [ΔM nearly 9 magnitudes!] - (AT115EDT @ 73X)

Iota Cassiopeiae – 4.6/6.9/9.1 magnitudes @ 2.7/6.7 arc-seconds

  • Well separated secondary seems yellowish - (10-inch Newtonian @ 78X)
  • Greenish 3rd star close to primary emerges with increased magnification - Beautiful! - (10-inch Newtonian @ 104X)
  • Farther component seems golden in comparison to white primary; second companion occasionally peeks out from the swollen disc of the primary - (10-inch Newtonian @ 156X)
  • Yellow/reddish/gray; striking triple star! - (C-11 @ 255X)
  • Yellow/bluish/reddish; nice tight trio w/ good brightness & color contrast; very striking - (C-11 @ 255X)

 

These observations are nothing special - just snippets of what I had recorded at the time. Maybe they will be interesting for comparison purposes. The telescopes used included an AstroTech AT115EDT APO triplet refractor, a GSO Newtonian 10-inch, and a Celestron-11 XLT. The varying colors reported show, at least for this observer, how color perception varies with instrument, magnification and perhaps by changing sky conditions. More to come as opportunity arises.

 

Edit:

​While I'll likely concentrate on the doubles that haven't been observed before, Gamma Cassiopeiae seems intriguing. That 9 magnitude ΔM and close separation will merit another look for sure. 

 

Best Regards,

Russ


Edited by Rustler46, Yesterday, 07:16 PM.

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