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Iota Ursae Majoris in a Vixen VMC 110L

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#1 Magnetic Field

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Posted 03 January 2020 - 04:53 AM

How do you do?

 

It took me four observing nights and some google search until I saw light at the end of the tunnel.

 

Just for the record: The following observing report is based on a location in my native country in a valley in the Alps (latitude approx 47 degrees) and not in the UK where I live for most most parts of the year. I mention it now: Delta Ursae Minor is easy to split as well. However, Sirius is just to low at the horizon (all I saw the last 2 weeks is a mushy red-blue coloured ball).

 

The magnitude is 190x with a 6mm Vixen NPL (note I did some modifications and the true focal length of my Vixen VMC 110L is different to the factory set up: https://www.cloudyni...i-prism-fitted/ )

 

Note: Left-hand and Right-hand are reversed in my Vixen VMC 110L due to the prism.

 

Can anyone please comment on the following Iota Ursae Majoris:

 

 

Fig1grab.jpg

 

Fig2grab.jpeg

 

Fig3grab.jpg

 

Fig4grab2.jpg

 


Edited by Magnetic Field, 03 January 2020 - 05:01 AM.


#2 Magnetic Field

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Posted 03 January 2020 - 10:14 AM

How do you do?

 

It took me four observing nights and some google search until I saw light at the end of the tunnel.

 

Just for the record: The following observing report is based on a location in my native country in a valley in the Alps (latitude approx 47 degrees) and not in the UK where I live for most most parts of the year. I mention it now: Delta Ursae Minor is easy to split as well. However, Sirius is just to low at the horizon (all I saw the last 2 weeks is a mushy red-blue coloured ball).

 

The magnitude is 190x with a 6mm Vixen NPL (note I did some modifications and the true focal length of my Vixen VMC 110L is different to the factory set up: https://www.cloudyni...i-prism-fitted/ )

 

Note: Left-hand and Right-hand are reversed in my Vixen VMC 110L due to the prism.

 

Can anyone please comment on the following Iota Ursae Majoris:

 

 

attachicon.gifFig1grab.jpg

 

attachicon.gifFig2grab.jpeg

 

attachicon.gifFig3grab.jpg

 

attachicon.gifFig4grab2.jpg

The period of Iota Ursae Majoris is 2000 years.

 

Thence the whole thing does not make sense (a change of position angle of 80 degrees within 6 years).

 

 

It would be great if people post here what they see in their 4" telescopes (or bigger):

 

I tried to find some up to date information but with no avail. Does anyone have got access to a reliable source of position angle for 2019?

 

Thanks


Edited by Magnetic Field, 03 January 2020 - 10:15 AM.


#3 dmdouglass

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Posted 03 January 2020 - 01:00 PM

Current Stelle Doppie listing is:

08592+4803 Iota UMa

HJ 2477   2017  A,BC  106 Degrees  2.2 (ArcMin) Seperation

HU 628    2017  BC  206 Degrees  0.9 (ArcMin) Seperation


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#4 Magnetic Field

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Posted 03 January 2020 - 01:27 PM

Current Stelle Doppie listing is:

08592+4803 Iota UMa

HJ 2477   2017  A,BC  106 Degrees  2.2 (ArcMin) Seperation

HU 628    2017  BC  206 Degrees  0.9 (ArcMin) Seperation

I think 106 degrees could work also in my case but still does not explain the massive discrepancy between Skychart's 82 degrees and even more so Moore's 2 degrees.

 

I am quite sure I have split it (although I admit it requires a good night otherwise the companion is overpowered by the brighter main star and washed out in mediocre seeing).

 

Again where did Patrick Moore got his info from? He also lists Iota UMajoris with a distance of 7.4".

 

Btw: 2.2 ArcMin is a typo?



#5 dmdouglass

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Posted 03 January 2020 - 04:00 PM

You asked:

Btw: 2.2 ArcMin is a typo?

 

 

Ahhhh. Yup !  Make that ArcSec please.

Thanks for the "catch"...



#6 c2m2t

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Posted 04 January 2020 - 01:18 AM

Hello MF!

Your first diagram is reasonably representative of what the current WDS data indicates. To be more correct, your companion star would reside below the travel line given the present PA of 106.2 degrees. Possible answers to your query are:

1 - you are looking at the wrong star

2 - somehow your image is getting turned the 90d

 

The Delta mag of 6.07 is significant and in spite of the 2.21"of separation, this is going to be a tough split for 4.5" optics, especially if the seeing is below average. There is going to be significant glare even with good conditions. Are you tracking the star, ie, equatorial mount with drive motor?

 

Cheers, Chris

Attached Thumbnails

  • HJ 2477+HU 628-Data.JPG


#7 Magnetic Field

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Posted 04 January 2020 - 02:41 AM

Hello MF!

Your first diagram is reasonably representative of what the current WDS data indicates. To be more correct, your companion star would reside below the travel line given the present PA of 106.2 degrees. Possible answers to your query are:

1 - you are looking at the wrong star

2 - somehow your image is getting turned the 90d

 

The Delta mag of 6.07 is significant and in spite of the 2.21"of separation, this is going to be a tough split for 4.5" optics, especially if the seeing is below average. There is going to be significant glare even with good conditions. Are you tracking the star, ie, equatorial mount with drive motor?

 

Cheers, Chris

I am sure I looked at the right star.

 

The star chart on the right panel in Figure 1 is actually what I see with the unaided eye.

 

My mount is a bog standard Vixen Porta alt-az. And as I said left and right are reversed in the eyepiece.

 

110 degrees or so actually would work.

 

Regarding glare. I took me 4 nights.*** The first 3 nights didn't really show the companion. But I knew there is something wrong because it was nearly impossible to focus the main star in bad seeing because I always ended up with a spike (where I now know the companion sits).

 

Any 4" telescope owners out there who want to challenge my observation. Would be great to get a confirmation or rebuttal (also for Delta Ursae Minor).

 

 

***I don't think there is a good correlation between Jet Stream and seeing. Although it is true that good seeing often comes with a low jet stream (you can zoom in and click on your location to get a value forecast: http://www.chilescop...tream-forecast/ ). But on Thursday 2nd Jan 2020 the seeing was quite good for zenith regions and also the jet stream at my location was very low (<<40 knots). Also in my valley with a Bortle 3 skie  often you wake up in the morning with heavy fog. This means visibility is often not that great while observing (fogs starts to slowly build up during the night) but this helps with double star glare issues. For example NGC 2403 (mag 8.5, 23'x12') is an easy object for my Vixen. But  NGC 4236 (mag 9.5, 23'x7') is a very difficult object.

 

 

Thanks


Edited by Magnetic Field, 04 January 2020 - 02:55 AM.


#8 c2m2t

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Posted 04 January 2020 - 09:52 AM

Good Morning MF!

Given that you are certain that you are looking at the correct star, how certain are you that you are seeing a star at the position you have indicated...approx. 90 degrees from where the companon should be? Is the magnitude indicative of the 9.2 that is listed in the data? This system is well documented with 75 observations/measurements since it was first recorded so I don't think there are issues with the data. I have been imaging double star systems for 10 years now and have discovered systems with much fewer observations where the magnitude was significantly different from the data. Another CN contributor and I have prepared several papers on these systems which have led to data changes in the WDS. But with 75 observations, it would surprise me if the magnitude data is sufficiently off.

 

May I make a suggestion...what about observing another system in the same area that has a separation of say 5 arc-seconds...a system that has components with a similar magnitude. I did a little hunt and found Wasat in Gemini, a.k.a. STF 1066. This should be quite easy to star hop to. Stellar mags are 3.53 & 8.18 with a separation of 5.4 and a PA 234 degrees. This should allow you to assess your optics and sky conditions and get a feel for what you should be expecting with Iot UMa.

 

Next opportunity I have, I will attempt an observation with a 5"achromat F8.3 on an alt-az mount and see if I can resolve tyhis pair.

 

Cheers, Chris.



#9 Magnetic Field

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Posted 04 January 2020 - 11:07 AM

Good Morning MF!

Given that you are certain that you are looking at the correct star, how certain are you that you are seeing a star at the position you have indicated...approx. 90 degrees from where the companon should be? Is the magnitude indicative of the 9.2 that is listed in the data? This system is well documented with 75 observations/measurements since it was first recorded so I don't think there are issues with the data. I have been imaging double star systems for 10 years now and have discovered systems with much fewer observations where the magnitude was significantly different from the data. Another CN contributor and I have prepared several papers on these systems which have led to data changes in the WDS. But with 75 observations, it would surprise me if the magnitude data is sufficiently off.

 

May I make a suggestion...what about observing another system in the same area that has a separation of say 5 arc-seconds...a system that has components with a similar magnitude. I did a little hunt and found Wasat in Gemini, a.k.a. STF 1066. This should be quite easy to star hop to. Stellar mags are 3.53 & 8.18 with a separation of 5.4 and a PA 234 degrees. This should allow you to assess your optics and sky conditions and get a feel for what you should be expecting with Iot UMa.

 

Next opportunity I have, I will attempt an observation with a 5"achromat F8.3 on an alt-az mount and see if I can resolve tyhis pair.

 

Cheers, Chris.

110 degrees should work.

 

The following not to scale but you get the idea.

 

The second Figure from Skychart (stars labelled 3.12 and 3.13): Another possibility there is a close star nearby that is not part of the double system. The latter would also correspond to my observation. The more I think about it this solves the mystery.

 

 

Fig6.jpeg

 

Fig7.jpeg



#10 c2m2t

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Posted 04 January 2020 - 02:29 PM

Hi MF!

Something is amiss here. I am assuming that the second mag. 3 star you are referring to is Kappa UMa a.k.a. Talitha Australis and A1585. From Aladin I get a separation in the order of 1.153 degrees. At a magnification of 172.5x (1035/6) (focal length of scope divided by the focal length of your EP), I do not think you can have both Iota and Kappa CMa in the same field of view. 

 

I have attached an image from Aladin with notes to support the discussion. There are a number of stars that are dimmer but very much closer to Iota CMa that may be figuring into what you are seeing at the EP. I would strongly recommend that next time out. you have a look at Wasat first and confirm that what you are seeing is indicative of what the data is saying and once you have confirmed that, move onto Iota CMa. You may want to add a few longer focal length ep's to your equipment for the session. You should get a nice separation of Wasat with a 10 to 13mm eyepiece. This should provide you with a better idea of what you should be expecting with Iota CMa.

 

Good luck!!

 

Cheers, Chris.

Attached Thumbnails

  • HJ 2477+A 1585-Notes.jpg


#11 Magnetic Field

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Posted 04 January 2020 - 03:07 PM

Hi MF!

Something is amiss here. I am assuming that the second mag. 3 star you are referring to is Kappa UMa a.k.a. Talitha Australis and A1585. From Aladin I get a separation in the order of 1.153 degrees. At a magnification of 172.5x (1035/6) (focal length of scope divided by the focal length of your EP), I do not think you can have both Iota and Kappa CMa in the same field of view. 

 

I have attached an image from Aladin with notes to support the discussion. There are a number of stars that are dimmer but very much closer to Iota CMa that may be figuring into what you are seeing at the EP. I would strongly recommend that next time out. you have a look at Wasat first and confirm that what you are seeing is indicative of what the data is saying and once you have confirmed that, move onto Iota CMa. You may want to add a few longer focal length ep's to your equipment for the session. You should get a nice separation of Wasat with a 10 to 13mm eyepiece. This should provide you with a better idea of what you should be expecting with Iota CMa.

 

Good luck!!

 

Cheers, Chris.

Okay. False alarm with a background star.

 

Btw: my focal length is 1150 mm (and not 1035 mm) due to my prism modification and a 6mm ocular gives 0.25 degrees (also confirmed with a star drift method).

 

Back to square one: please 4" owners have a go at it. I claim I can split Iota Ursae Majoris.

 

By the way: I checked my log book and there is an entry from last week: "Double stars: Gam01 Leo, WDS STT 545 (in Aurigae), Alpha and Delta Gemini: easy to split, Ma9 and Ma10". Info: Ma9 and Ma10 are my code for the 8mm and 6mm Vixen NPL eyepiece.

 

Edit: How did you get 1.15 degrees separation for Iota Ursae Majoris and  TYC 3420-2149-20 (designation according to Skychart, mag 3.13 in the Figure). The following screen shot shows Skychart's view of 0.5 degrees:

 

Fig8.jpeg


Edited by Magnetic Field, 04 January 2020 - 03:37 PM.


#12 c2m2t

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Posted 04 January 2020 - 06:11 PM

Hi MF!

The separation of 1.153 degrees comes directly from Aladin. Kappa CMa is the closest mag. 3 star to Iota CMa. I have no answer for what Skychart is generating for you. 

 

To satisfy your wish for a check with 4" optics, I'll use my SW100 ProED refractor to make my observations.

 

Cheers, Chris.


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#13 c2m2t

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Posted 04 January 2020 - 06:40 PM

Hi MF!

Here is a screen shot from Aladin from which I arrived at the 1.153 degrees distance measurement between Iota and Kappa CMa. This is an actual image generated by one of the many sky surveys which have been produced over the years. I believe we  can trust the information.

 

Cheers, Chris.

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  • HJ 2477+A 1585-Notes-2.jpg


#14 fred1871

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Posted 04 January 2020 - 06:59 PM

Ummm... how did we get from Kappa UMa to Kappa CMa? - from Ursa Major to Canis Major?


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#15 c2m2t

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Posted 04 January 2020 - 10:31 PM

Hi Fred!

Good catch....my error!! :-) should read UMa!!

 

Cheers, Chris?



#16 Magnetic Field

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Posted 09 January 2020 - 03:28 AM

Okay. False alarm with a background star.

 

Btw: my focal length is 1150 mm (and not 1035 mm) due to my prism modification and a 6mm ocular gives 0.25 degrees (also confirmed with a star drift method).

 

Back to square one: please 4" owners have a go at it. I claim I can split Iota Ursae Majoris.

 

By the way: I checked my log book and there is an entry from last week: "Double stars: Gam01 Leo, WDS STT 545 (in Aurigae), Alpha and Delta Gemini: easy to split, Ma9 and Ma10". Info: Ma9 and Ma10 are my code for the 8mm and 6mm Vixen NPL eyepiece.

 

Edit: How did you get 1.15 degrees separation for Iota Ursae Majoris and  TYC 3420-2149-20 (designation according to Skychart, mag 3.13 in the Figure). The following screen shot shows Skychart's view of 0.5 degrees:

 

attachicon.gifFig8.jpeg

To avoid a double post I refer the reader to post #42 in

 

https://www.cloudyni...m-fitted/page-2

 

I wonder if  Delta Ursae Minoris has also a close nearby background star which I mistook for the faint companion (like I did for Iota Ursae Majoris).




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