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Case 32 observed

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#1 flt158

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Posted 06 October 2021 - 05:16 PM

Hello, fans of carbon stars. 

 

On Tuesday 6th October 2021 I placed my William Optics 158mm F/7 apochromatic refractor in my Bortle 9 back garden. 

I had excellent seeing conditions and no Moon. 

Therefore it was high time to seek out an extremely faint carbon star in Cassiopeia. 

There was a 20 km/h wind blowing, but I refused to let that deter me from seeing Case 32. 

As I do have a mirror diagonal fitted my north is to the right and my east is down.   

 

The carbon star Case 32 has 2 other designations: GSC 04015-00768 or NSV 173. 

Guide 9.1 DVD states its magnitude is +12.3. 

Simbad gives +13.0. 

And AAVSO gives +13.5 V. 

So is Case 32 too faint for my scope?

 

Its Right Ascension is: 00 hours 29 minutes 08.24 seconds. 

The Declination is: +61 degrees 07 minutes 15.84 seconds. 

 

Its spectral class is C5. 

 

I did find it quite easy to star hop to its rough location starting with Beta Cassiopeiae (2.3 mag) through to 12 Cassiopeiae (5.4 mag). 

I had printed off a Guide 9 map which once again proved invaluable. 

 

There were 3 stars which pointed almost directly to Case 32. 

These were TYC 4015 3101 (10.1 mag), TYC 4015 1359 (10.2 mag) and TYC 4015 3037 (11.3 mag). 

There was also a 4th very faint star which is called TYC 4015 388 (12.4 mag) and it is 4 arc minutes east of Case 32. 

A 5th star, which is less than 3 arc minutes west-south-west of Case 32, has the designation 3UC303-011414 (on Guide 9) and its magnitude is +12.0. 

 

Therefore with the first 3 field stars observed with my 112X Pentax 10mm eyepiece, which gives me 27 arc minutes field of view, I felt I was ready to see if Case 32 was going to be visible to my eye.  

Of course it was not going to be all that easy to see it!

I had to increase my magnification up to 225X to see both TYC 4015 388 and 3UC303-011414, but they were still in the same fov thankfully. 

Indeed it took time to make out I was seeing both the 12.4 magnitude star TYC 4015 388 and 12.0 magnitude star 3UC303-011414 before I spotted Case 32. 

And so I discovered that the carbon star Case 32 is quite a bit fainter than what Guide 9 had suggested (+12.3). 

It was very clear that it was considerably fainter than both TYC 4015 388 and 3UC303-011414. 

 

I would suggest that Simbad's magnitude of +13 is correct.  

That is because of these last 2 field stars.

 

So I'm delighted to say I was successful in my endeavour in observing Case 32. 

And it is orange alright.

Indeed both 3UC303-011414 and Case 32 are 2 orange stars which sit side by side. 

How patient one has to be to see them both. 

 

Case 32 is my 21st carbon star in Cassiopeia and my 107th overall.  

 

Thank you for reading about my latest carbon star observation. 

 

Comments, corrections and images are very welcome. 

 

Clear skies, 

 

Aubrey. 

 

 

 


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#2 hambone20

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Posted 06 October 2021 - 08:39 PM

Nice grab Aubrey!  I'll try to crack that nut next time out.

 

Loren


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#3 dhkaiser

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Posted 06 October 2021 - 08:53 PM

Congratulations on your 107th carbon star Aubrey!  Well done.


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#4 dhkaiser

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Posted 10 October 2021 - 11:09 AM

Aubrey,

 

Interestingly my Guide 9.1 does not have Case 32 in the data base. 

 

I searched GSC 04015-00768 and went straight to it, however it is listed as 12.9 not 12.3.

 

Where did you see 12.3 in Guide 9.1?


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#5 flt158

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Posted 10 October 2021 - 05:18 PM

That is very interesting, Dan. 

 

My Guide 9.1 DVD does state that GSC 04015-00768 has a magnitude of 12.3. 

Simbad gives the same carbon star the designation Case 32. 

 

I'm wondering that your Guide 9.1 is a more up-to-date version.

I have no way of knowing how old my Guide 9 is - sorry!

 

If that is the case (pun intended), I would go along with your version 100%. 

As you well know, there is not much difference between 12.9 and 13.0. 

Therefore I would say your judgement of its magnitude is sound. 

 

Am I getting the feeling you are going to give Case 32 a go?

I wish you the very best before Luna becomes a problem. 

 

Please report back should you do so.

 

Very clear skies to you, Dan, from Aubrey.  


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#6 dhkaiser

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Posted 10 October 2021 - 07:15 PM

Aubrey, yes got my Guide 9.1 within the last year and a half.  So that may account for the discrepancy.

 

13th mag is beyond my telescopes and sky visually, I think it a lost cause for me to attempt it.


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#7 flt158

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Posted 11 October 2021 - 06:10 AM

Hello again, Dan. 

You might just remind me of what is your largest aperture. 

My memory banks are rather rusty. 

By the way, Case 32's magnitude is 13, which means it's a 12th magnitude star. 

Therefore you might have some hope in spotting the alternative designation GSC 04015-00768, 

 

But then again, that might be wishful thinking on my part. 

Still if you can find TYC 4015 388 or the brighter star which Guide 9.1 calls 3UC303-011414, I reckon you're in business. 

No doubt you have printed off a map of the area. 

 

Please give yourself about an hour before you abandon your search for the carbon star, Dan.

Initially you could see it using averted vision. 

Then you might just see it directly after about 10 minutes.  

 

Clear skies from you Irish pal, Aubrey. 



#8 dhkaiser

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Posted 11 October 2021 - 04:36 PM

Aubrey my double star telescope is a Lunt 102mm f/7 refractor.

Magnitude 12 - 13 stars are too faint for me in my bright skies.

 

May have something to do with my 73 year old eyes.  :-)

 

You say, "Case 32's magnitude is 13, which means it's a 12th magnitude star."

Not sure what that means, maybe a red 13th mag star appears as 12th?

 

I have imaged as faint as 15th mag so I might give that a try.

 

Dan


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#9 flt158

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Posted 12 October 2021 - 06:15 AM

Excellent to hear from you once again, Dan. 

 

I had no idea about your age. 

I'll soon catch up. lol.gif

 

I do very much thank you, Dan, for coming back to me with the aperture of your refractor. 

I believe all Lunt refractors are extremely good. 

 

And I will look forward to any image you might produce of Case 32. 

The RA and Dec are above. 

 

Please ignore what I said regarding magnitudes. 

 

Clear skies and good imaging to you Dan and anyone else, 

 

Aubrey. 


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#10 ssmith

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Posted 12 October 2021 - 12:15 PM

Hi Aubrey -

 

Here is an image of Case 32 I took last night.  It is very dim and I am impressed that you managed to view it.  I measured its magnitude as 13.4.  I plan on revisiting it over the next few months to see if the magnitude varies at all.

 

Case 32 Cas C9 10-11-21 15s 5fr.jpg


Edited by ssmith, 12 October 2021 - 12:16 PM.

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#11 flt158

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Posted 12 October 2021 - 05:28 PM

Wow! Most extraordinary image from you, Steve.

Thank you straight from my heart.

 

I see you took this image on 11th September 2021. 

But that's probably ought to be the 11th October. 

But no matter.

I have analysed my Guide 9.1 program with the very same set up as your excellent image and have compared the magnitudes of other field stars. 

I completely agree with your magnitude - Case 32 is 13.4 alright. 

 

Do you remember back in February 2019 you produced an image of Case 717 in Andromeda? 

And we worked out that carbon star was of magnitude 13.2. 

Well Case 32 is even fainter again. 

Therefore I am not 100% certain Case 32 is the faintest star I have ever observed. 

I'm blown away, Steve. 

You've done it again. 

100,000 thank yous.

 

As I said above, AAVSO call this carbon star NSV 173. 

In the VSX section, they give the magnitude range as 13.5 - ? V. 

Can I take it that the letter V at the end refers to a visual magnitude? 

 

I shall talk you again, Steve. 

 

Very best regards from Aubrey. 


Edited by flt158, 13 October 2021 - 06:22 AM.


#12 dhkaiser

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Posted 12 October 2021 - 08:40 PM

NSV stands for New Suspect Variable catalog. 

So Case 32 has been reported as a variable star but has

not been confirmed and added to the catalog of variables.

 

And yes V stands for the photometric V  or visual magnitude.

 

Steve, were you using standard filters to determine the magnitudes?


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#13 flt158

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Posted 13 October 2021 - 06:25 AM

Thank you for helping me out, Dan.

 

I written down in a notebook that piece of important information regarding the NSV designation. 

 

Very best regards from Aubrey. 



#14 ssmith

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Posted 13 October 2021 - 08:26 PM

Hi Aubrey -  

 

You are correct, the date on my photo should read 10-11-21.  The time has expired to edit the photo posted so I will just leave the original photo above as-is.

 

Earlier I had looked up "Case 32" on the AAVSO database but it came up empty - I wasn't aware of the NSV 173 identifier - it also goes by 000-BPD-660 .

 

There is only one recoded observation in the AAVSO database and by some "Happy?" coincidence it was made on Oct 5 - the day before your original Posting on Case 32.  It also came up with a visual magnitude of 13.4.

 

Case32 AAVSO obs.jpg

 

Dan - to answer your question - I don't use any photometric filters but I make my measurements using the green channel from my photos.  I regularly post my observations of 6 or so variable stars on the AAVSO database and record them as "Tri-Color Green" measurements.  

 

In the case of Case 32 my Green Channel magnitude measurement was 13.35 and to transform it to a V-band magnitude  I subtract 0.03 (my transformation coefficient) which gives a V band transformed magnitude of 13.38 - not too different from the visual magnitude recorded by GATH above.  Now that I know the proper identifiers I will post my observation to the AAVSO.

 

The photo I posted in reply #10 was from a stack of 15 second exposures.  Here is a close-up Photo of Case 32 made with a stack of 40 second exposures that goes a bit deeper.  I love the chain of 16 and 17 magnitude stars that trail away to the north-east - they remind me of a string of pearls.

 

Case 32 Cas C9 10-11-21 3200 40s 8fr PCC NonLinear ATWT crop.jpg


Edited by ssmith, 13 October 2021 - 11:26 PM.

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#15 dhkaiser

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Posted 13 October 2021 - 08:51 PM

Thanks for the explanation Steve.  Impressive photography and photometry.


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#16 flt158

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Posted 14 October 2021 - 06:07 AM

Hello Steve - that was me!!! 

I'm Gath. lol.gif lol.gif

 

By the way it's all terribly weird. 

The AAVSO people realised I had been interested in the carbon star Case 32 or NSV 173. 

They even sent me a personal email; even though I never made such a request. Weird!

 

I hope you don't mind, Steve. 

But when I saw your image and you stating that Case 32 has a visual magnitude as 13.4 I took liberty by using this magnitude as an acknowledgment of your estimate 

And after all I had seen this star on Tuesday 5th October just a few nights before your image. 

That's why I'm taking it as magnitude 13.4. 

Sorry about that, Steve.

Please express your feelings if I have done wrong.  

I will accept your judgement on the matter. 

 

Very best regards from Aubrey. 



#17 ssmith

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Posted 14 October 2021 - 12:01 PM

Hi Aubery -

 

It all makes sense now.  When I looked at the observation by GATH it sounded vaguely familiar but I couldn't make sense of the Observer code GATH.  I assume the "A" in GATH stands for Aubrey ?

 

Thinking it over I think you should either edit or delete your observation.  You could edit your observation to give a "Fainter Than" Magnitude estimate if you can recall your impressions from that night. 

 

You can then revisit the star and come up with your own independent magnitude estimate.

 

The AAVSO doesn't list any Comparison Stars in the vicinity of Case 32 so here is a plot of some comparison stars that I have put together.   The best comparison stars will have a color index similar to the target star but as you can see all the stars in the FOV are distinctly white in color which makes magnitude estimating a bit tougher.  

 

Since a primary goal is to determine if the star is "variable"  it is perhaps more important to note any relative change in magnitude in comparison to the surrounding stars rather than coming up with a hard and fast number.  Since you are operating so close to the visual limit of your scope it will be interesting to see if at some point the star simply disappears from your view.

 

There is also the possibility that the range is so small that the star remains relatively constant over a long period of time.

 

Many Carbon Variables seem to have a period that falls in the range of 300-400 days so I would recommend checking on it every 3 to 4 weeks.  This star is also circumpolar so it has the advantage of being visible year-round.

 

Case 32 Cas C9 10-11-21 3200 40s 8fr UCAC4 Comp Stars crop.jpg


Edited by ssmith, 14 October 2021 - 12:21 PM.


#18 flt158

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Posted 14 October 2021 - 12:31 PM

Thank you for your advice, Steve. 

 

Lesson learnt. I will delete and maybe observe Case 32 again in due course. 

 

Although I always stop observing Cassiopeia at Christmas. 

You see the constellation reaches my zenith and there is just no way I can observe this wonderful constellation at the end of each year because the focuser is colliding with my Berlebach Planet alt-az mount. 

 

Kind regards from Aubrey. 




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