50 replies to this topic

[Eclipsed]

I happened to be looking at Doubles last night too and I was able to barely split the Theta Aurigae using my 8 EdgeHD and a 17.5mm eyepiece and 2x Barlow.  Seeing wasn't great and it was a challenge.

 

I swapped the eyepiece for my SV305 camera and snapped a quick video capture.  Below is one of the better frames.  You can just see the secondary star very close to the extremely over-exposed main star at about the 2 o'clock position:

 

Attached Thumbnails

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[JuergenB]

Tonight I observered theta Aur AB with my 4.7" TSA-120 refractor. Seeing was mediocre (Pickering 5), but the companion was steadily visible with 8 mm (112x) and 5 mm (180x) eyepieces. It was a nice view, much easier than splitting eta Gem (Propus) yesterday at comparable seeing.

 

Juergen

 

 

 

[Sasa]

If the seeing is good (which it MUST be), Theta Aurigae is a piece of cake in a 4", IMO. That is, of course, assuming good optics and a reasonably experienced observer.

Poor seeing can quickly render the faint companion invisible.


Clear skies!
Thomas, Denmark

Yep, I was observing theta Aurigae recently and I was surprised how easy it was in 4" refractor. Not only seeing but also well tempered telescope is important. I know it takes about 15min for my 63mm Telementor to start to show the companion with delta T about 20C.

[Oldfracguy]

I was able to get a nice split a few minutes ago of this 3rd and 7th magnitude 3.9" double using a KK Fujiyama HD-OR 5mm Orthoscopic in a new Askar 120 APO at 168x.  Nice little diffraction ring around the main star, too, and pitch black background sky.

 

I use Theta Aurigae as a test for good seeing, and also as a starting point for finding M37 the old-fashioned way--star hopping:

 

 

 

 

 

 

[lionel]

Last night I tried some challenging doubles with my AT115EDT which I purchased as a stand in for my GTX when doing outreach activities and when viewing with my grandkids. 

 

 It was a clear moonless night with better than average P6 seeing, no wind and a reasonably transparent Bortle 7 sky.  One of my targets near the zenith was Mahasim (theta Aur) which I hadn’t viewed previously.  I spotted and held the dim pinpoint secondary with black space separation from the primary, about 50% of the time at 73x (11T6) and 90% of the time at 115x (7T6).

 

A nice unequal pair for a 4” class scope with low scatter optics.

 

Lionel

Edited by lionel, 04 February 2024 - 06:37 PM.

[Oldfracguy]

I happened to be looking at Doubles last night too and I was able to barely split the Theta Aurigae using my 8 EdgeHD and a 17.5mm eyepiece and 2x Barlow.  Seeing wasn't great and it was a challenge.

 

I swapped the eyepiece for my SV305 camera and snapped a quick video capture.  Below is one of the better frames.  You can just see the secondary star very close to the extremely over-exposed main star at about the 2 o'clock position:

 

 

Last night I tried some challenging doubles with my AT115EDT which I purchased as a stand in for my GTX when doing outreach activities and when viewing with my grandkids. 

 

 It was a clear moonless night with better than average P6 seeing, no wind and a reasonably transparent Bortle 7 sky.  One of my targets near the zenith was Mahasim (theta Aur) which I hadn’t viewed previously.  I spotted and held the dim pinpoint secondary with black space separation from the primary, about 50% of the time at 73x (11T6) and 90% of the time at 115x (7T6). A nice unequal pair for a 4” class scope with low scatter optics.

 

Lionel

 

 

Last year I had a C8 and an AT115EDT outside at the same time.  The C8 provided an exceptional view of M13 compared to the AT115EDT, but when I turned both scopes on double stars, the AT115EDT blew the C8 out of the water.  The stars were pinpoints, with black sky in between.  With the C8 they were mushy cotton balls.  And yes, I did have the C8 wrapped with that "reflectix" stuff, and a long dew shield as well.

 

I have had two other SCTs since then, another C8 and a C6, hoping I would luck out and get a "good one".  Unfortunately, luck was not with me.  I now have an Askar 120 APO, and it has no trouble splitting 1.5" 32 Orionis.  I'm hoping for some exceptional seeing to try for 52 Orionis (1").  I was not able to split any 1" doubles with that AT115EDT, but then my eyes are not the greatest, being by far the weakest link in the optical chain.

 

EDIT:  I neglected to mention that with all three of those SCTs I did not do as has been recommended recently in another CN thread, and that was to back off on all those screws that hold the front corrector in place.  Apparently, many SCTs suffer from having those screws, and hence the corrector retaining ring, so tight that the corrector is under stress and is being warped slightly out of shape, thereby leading to "mushy" or "soft" images:

 

https://www.cloudyni.../#entry13216813

Edited by Oldfracguy, 04 February 2024 - 07:28 PM.

[lionel]

A 115mm scope has a Dawes limit of 1.01” which means it won’t give you a black line split of a 1.0” equal double. There will be partial overlap of the two spurious disks making the star image look elongated in decent seeing but with a noticeable waist like a figure 8,  Technically it is considered just resolved but is not a clean split. That would be the Rayleigh limit which is 1.20” for a 115mm.

 

Lionel

Edited by lionel, 04 February 2024 - 08:35 PM.

[Oldfracguy]

OK, we finally had a break in the clouds and rain, and just a little while ago I was able to get a good look at Theta Aurigae once again.  It was about 8 PM PST from about 15 miles East of San Diego, and Theta Aurigae was almost directly overhead and almost due East.  I estimate the Alt was 85°, and the Azimuth was close to 90°.  I had the scope set up facing due East, and was using a prism diagonal in a refractor, so the view was up-down correct, but left-right reversed.  I was using a magnification of 140x in a 120mm f/7 refractor (KK Fujiyama HD-OR 6mm Orthoscopic), and I could clearly see the little companion star at the 1 o'clock position relative to the main star.

Edited by Oldfracguy, 09 February 2024 - 11:32 PM.

[Brollen]

I’ve been reading that Theta Aurigae is a challenging unequal double and I’ve been wanting over the last few weeks to see how two of my scopes in particular would do. Weather has been lousy here in the mid Atlantic but last night - finally! - it was a nice clear night, no winds and seeing was good. Here in Baltimore Theta Aurigae is high in NW around 10pm, over Camden Yards. Fortunately too, the Birds were out of town and the stadium lights were off.

 

My two scopes I wanted to test, are a very good (probably excellent .. it’s that good) C6 and an excellent SVX102D. I had brought them out Sunday evening to a high balcony around 6pm, letting them cool. It wasn’t till around 9:30 or so that I returned to start looking.

 

In both scopes, I was using my Baader MB II BV’s with the 1.7x GPC. With the SVX102D I used a pair of ES 82° 11mm EPs and to my delight I easily split Theta Aurigae seeing the companion star - dimly but distinctly there. Next was my C6 - the sharpest SCT I have had. With the C6 I used a pair of ES 68° 16mm EPs and again to my delight, just lying outside the first diffraction ring was the companion star - very distinct.

 

A good night of seeing and of star splitting. Clear skies!

Edited by Brollen, 08 April 2024 - 09:34 AM.

[flt158]

Great observation from you, Brollen!

 

I never have a problem seeing all 3 components of Theta Aurigae. 

A and C are easy.  I use the C star to make sure I have the right triple. 

With my William Optics 158mm f/7 apochromatic refractor I can easily see the B star at 140x. 

It is invisible at 112x. 

My separating eyepiece is a TMB 8mm, 

and is very old. 

 

Clear skies to you from Aubrey. 

[CHnuschti]

Was wondering. Did hold on it tonight with 110/660. Quite enjoyable seeing and clarity. With 145x or 190x. Needed a careful look for sure, but the B was well identifiable. A prerequisite of good conditions I would say for midsize refractors.

 

regards

Edited by CHnuschti, 12 April 2024 - 06:00 PM.

[michael1959]

Date: April 14 around 9pm EDT.

Loc: One hour west of Toronto.

Scope: Tak FC-100DZ (800mm FL)

Seeing: Average. 

 

Theta Aurigae B easily visible at 160X (5mm Nikon SW).

 

I missed B during my first pass at 114X (7mm Pentax XW), but once I knew where it was (at 160x) I went back to detect it at 114X. Though it wasn't stable at this magnification.

[jrazz]

Same.

 

I used my FC-100DC with TPL 9mm (82x) and TPL 6mm (123x) eyepieces.

I thought it was a lovely double showing a bright primary with a fairly dim but distinct secondary. I would have expected the magnitude difference to make the observation harder but this turned out to be easier than that. In fact the secondary was very distinct from the glare of the primary. 

[michael1959]

Jordan/jrazz,

 

This is the second time you've seen a stellar companion at a lower power than I have. My eyes aren't the best, but I wonder whether you might also have excellent seeing in NoCO. Seeing is rarely excellent in SoON. (Nobody calls it that, but I'm going to start now.)

 

I may try simpler eyepieces too.

[Oldfracguy]

Same.

 

I used my FC-100DC with TPL 9mm (82x) and TPL 6mm (123x) eyepieces.

I thought it was a lovely double showing a bright primary with a fairly dim but distinct secondary. I would have expected the magnitude difference to make the observation harder but this turned out to be easier than that. In fact the secondary was very distinct from the glare of the primary. 

You must have had pretty good seeing.  The better the seeing, the more distinct and smaller the little companion star appears, with more black sky between it and the main star.  The A (3rd magnitude) and B (7th magnitude) stars are almost 4 arcseconds apart.  

Edited by Oldfracguy, 15 April 2024 - 06:30 PM.

[jrazz]

It was a quiet night. I also do have very well corrected vision (LASIK) so doubles are easier for me at low magnification.

I find that I prefer the sharpness of the lower magnification of the TPL eyepieces over the TOE.

 

I also thing the lower magnification makes the secondary brighter (along with the primary of course) not sure if that helps me.

 

But yes, I've noticed that I definitely have a preference of lower magnifications and that higher mags do not improve the resolution of the view.

Edited by jrazz, 15 April 2024 - 06:30 PM.

[Oldfracguy]

Being able to see faint companions in doubles and triples requires good seeing first, and then the right size Exit Pupil.  Too much magnification can be detrimental.  For example, with my AT125EDL I can see the F star in the Trapezium, with direct vision even sometimes, only if I hit the right combination of magnification and hence Exit Pupil.  For me, that happens around 140x to 160x with an Exit Pupil between 0.8 and 0.9 mm.

[CHnuschti]

It was a quiet night. I also do have very well corrected vision (LASIK) so doubles are easier for me at low magnification.

I find that I prefer the sharpness of the lower magnification of the TPL eyepieces over the TOE.

 

I also thing the lower magnification makes the secondary brighter (along with the primary of course) not sure if that helps me.

 

But yes, I've noticed that I definitely have a preference of lower magnifications and that higher mags do not improve the resolution of the view.

I second that by all means. Very much my approach. The lesser the magnification and the tighter the separation mostly gives the  best visual for me. And sometimes impressive, how faint companions (among the wider sort) might pop out excellently and in direct view, where just one higher "gear" of magnification brings it already in the range of adverted view.

 

However it does not forcedly apply for very bright stars like Sirius, the intereference ot the lightning might make higher magnification advisable in order to bring the companion as far away as possible.

 

regards

Edited by CHnuschti, 16 April 2024 - 03:48 PM.

[Oldfracguy]

Last night we had pretty good seeing, and I was able to clearly see the small B star quite well.  At times I thought I might have caught a glimpse of the C star using a 125mm APO refractor.  (Theta Aurigae actually has an A, B, C and D star).  If anyone with a larger (8" scope or higher) scope has seen the C star, is it located as shown in this little drawing?

 

 

 

 

[CHnuschti]

No, it is in the same line like AB. Was not aware of it, on the second look on the system after that knowledge I was able to just so detect C with adverted view, with 110/660. Quite at the limit. PAs are 305 and 300°. There is also a D, easy in comparison, probably that what is marked as B in your sketch.

 

https://www.stelledo...?iddoppia=22645

 

regards

Edited by CHnuschti, 16 April 2024 - 04:55 PM.

[Mike McShan]

I checked my log and found that I observed it January 28, 2017 with my 4" APO at 135 X. I didn't take as good of double star notes as I do now, so no comment other than splitting it. Seeing was 9/10, which I'm sure helped. I am putting it on my observing list to revisit it now that this thread has peaked my interest.

 

Clear skies,

Mike 

[Oldfracguy]

No, it is in the same line like AB. Was not aware of it, on the second look on the system after that knowledge I was able to just so detect C with adverted view, with 110/660. Quite at the limit. PAs are 305 and 300°. There is also a D, easy in comparison, probably that what is marked as B in your sketch.

 

https://www.stelledo...?iddoppia=22645

 

regards

I should have mentioned that the drawing back in Post# 44 is how I saw the star arrangement when looking through a 90° star diagonal, so the stars are correct up and down, but are left-right reversed from their true positions.  Will that make a difference?

[CHnuschti]

I should have mentioned that the drawing back in Post# 44 is how I saw the star arrangement when looking through a 90° star diagonal, so the stars are correct up and down, but are left-right reversed from their true positions.  Will that make a difference?

Well, yes?. The PA=position angle is counted positive counterclockwise when using an Amici Prisma=RACI right angle correct image=like it would be seen by eye or binocular.

 

Using a mirror diagonal, image gets horizontally mirrored, the PA then is to count positive clockwise.

 

This against the imaginary north direction, which you have to figure out over charts or by other means.

 

In e.g. skysafari, if you switch on the equatorial grid over settings>grid and reference>equatorial grid, then it is displayed directly in the chart, of which one direction is always the north direction. Might be of help.

 

https://www.astronom...ble-star-fever/
https://en.wikipedia.../Position_angle

 

Belongs really to the basics of double star observation, you should familiarize with it.

 

regards

[Oldfracguy]

I was able to find a source for the positions of all the four stars in the Theta Aurigae system:

 

 

 

 

Those C and D stars I have seen many times, but I thought they were just nearby faint stars that were not associated with the main pair A and B since they are so far away, comparatively speaking.  I was thinking that the C and D stars were closer to the main star, but it's not the case with Theta Aurigae.  

 

[fred1871]

Simplest way to get the basic information is the WDS, or Stelle Doppie.

 

The WDS version runs

 

05597+3713STT 545AB    1871 2019  125   7 304   2.1   4.2  2.60  7.2  A0V       +044-074 +026-077 +37 1380 NO   055943.24+371245.9
05597+3713STT 545AC    1782 2019   25 286 300  35.3  56.4  2.60 11.1  A0pSi     +044-074 +001-003          NL S 055943.24+371245.9
05597+3713STT 545AD    1823 2019   18 352 349 125.1 139.2  2.60 10.10 A0pSi     +044-074 +001-000 +37 1379 NS   055943.24+371245.9

 

Or, in Stelle Doppie

 

SHOW NAME CST SAO COORD WDS_NAME LAST OBS PA SEP MAG1 MAG2 D_MAG ORB
Show Mahasim Aur 58636 05 59 43 +37 12 46 STT 545 AB 2019 125 304 4.2 2.60 7.20 4.60 Y
Show  Aur 58636 05 59 43 +37 12 46 STT 545 AC 2019 25 300 56.4 2.60 11.10 8.50
Show  Aur 58636 05 59 43 +37 12 46 STT 545 AD 2019 18 349 139.2 2.60 10.10 7.50

 

In SD the layout makes it easier to read than this de-formatted version

Edited by fred1871, 19 April 2024 - 03:45 AM.