234 replies to this topic

[stanislas-jean]

Well, if we have a look at wikipedia, there are about 200 photometric systems in use in past and now.

Coming back on this T Crb topic, how to operate?

 

Filters:

the system in use visually seems to be with the use of johnson filters UBVRI (defined histotically for visual measurements).

Buying the set of recognised filters, it costs more or less 1000 usd.

We may use color filters, cheaper when following the BAA paper based on tests.

Here is:

https://britastro.or...VRI_filters.pdf

where a W38 and a 400-700 filters is similar to a U bessel filter; a W56 and a W12 similar to the V bessel filter, etc...

 

A calibration is needed to match with the ccd chipset in use.

 

Procedure to be used, given through the paper of the AAVSO

https://www.aavso.or...Manual_v1-2.pdf

 

These are general ideas. Now for T Crb, with the hardware to be used.

How with a dslr, already for other bodies,

How with the ss50 equipped with a 462C, with a tele and any other chipset

conditions needs to be settled prior to operate to keep confidence in the results.

Commencing the debate, the discussions?

 

Nothing more yesterday 31st july 20H30 UT.

Good skies.

Stanislas-Jean

[Redbetter]

I don't know how the imagers are doing their reporting to AAVSO, but I do know that it is reported in the appropriate bands:  V, B, R, etc.  Comparison stars are used.  All you have to do is generate a light curve on the site and sift through the data.

 

But a simpler way for observing is just using the Mark I eyeball to look up at the sky to see if T CrB has reached naked eye brightness.  Or one can use a modest telescope (even in town) to examine the field and use an AAVSO chart to make a visual estimate with stars calibrated to the visual magnitude system.  The Argelander method works well for this.  Last night I arrived at 10.2 V mag.

 

For those being more precise, an interesting thing arises when looking at the AAVSO photometry information for the comparison stars.  I like to pull up the more precise data with more significant digits for the calculations, and drop to the tenths at the end.  (I am not reporting my results to AAVSO so as not to contaminate their data sets.)  This addresses some incontinuities/inconsistencies I have noticed with various fields and visual estimates submitted to the AAVSO database when tracking changes in other stars.  

 

For instance the 9.8 mag comparison star on AAVSO's charts lacks APASS magnitudes, but AAVSO's field photometry table lists it as 10.061 V mag, while the 10.6 mag star nearest T CrB is 10.566.  Using the nominal values on the charts to match AAVSO's data sets for comparison, I get brighter results for T CrB (10.0 V mag last night.)  I assume that the 9.8 is some sort of historical carry over to keep the datasets on the same basis.  Unfortunately, I find that magnitude at odds visually with the relative brightness of the 10.2 mag star and the 10.6 on the chart.  The steps simply don't look right to me for 9.8.  

[stanislas-jean]

Actually the question is not that.

Numbers have significance and the difference of 0.2-0.5 magnitude noted from a way to another is, but its significance is not defined.

What the ancients did on T Crb are mailnly visual, photographic for a part and there was differences between the 2 ways.

Capturing images is easy, visual requires activity and experience for measuring something at 0.02+/- acuracy.

Already.

But making something consistent, what can be the procedure to be used, hardware and reference stars?

AAVSO publishes field of stars with magnitudes, color index is avoided...

In fact what they want?

I remembered the occultation of a star by the satelite Triton of Neptune 2-3 years ago. The question was set also, the question was to capture something unfiltered in the aim of collecting the light decrease and increase in order to analyse the Triton atmosphere...

There was an international call about, with the correct procedure rather unknown.

Coming back to T Crb, questions are:

- filtering is needed?

- how to use the reference star maps established visually for imaging?

- which calibration of the chipset is needed (not the dark and the illumination), chipset spectral responses are different from one to an other?

If somebody can answer those, personnally I cannot.

 

Nothing occured yesterday the 1st august evening.

Good skies.

Stanislas-Jean

Edited by stanislas-jean, 02 August 2024 - 04:30 AM.

[Redbetter]

No the question "is that" for visual observing.  I have noticed the discontinuities in AAVSO maps before.  The .1 mag rounding of the reference stars is part of the problem, since good visual observers can demonstrate precision better than that.  (Half magnitude steps for me can run about 0.07 magnitude.)  The rounding problem of the reference magnitudes also limits the accuracy, sometimes shifting the results .1 mag or more based on the stars chosen.

 

There is a lack of self-consistency in some of the reference magnitudes.  Ideally one would want reference set photometry taken together, rather than mixing and matching as seems to be happening with this particular group.  The 9.8 star seems to have the worst precision and accuracy of the group in the current magnitude range, and that is problematic whether visual or imaging.

 

I am not sure what you are talking about with respect to color index.  It is measured and known by AAVSO to be a potential confounding problem with both the reference and variable stars.  The "ancients" didn't know T CrB existed, too dim.

 

Good luck with your imaging questions, you probably need to check the "Scientific Amateur Astronomy" sub-forum for answers to questions like that since getting more precise instrumental measures is their bailiwick.   Th DSO forum is primarily for visual observing, so not the best place to get an imaging question answered.

[stanislas-jean]

Thanks for responding.

Sure what was done in past, visually, were proceeded  with filters for taking into account color index (IC) of the star in reference.

Blue stars, yellowish-green, and, reddish. This corresponds to the light spectrum of each star.

Therefore magnitude shifts may be fixed between "colored" stars.

Sure that experienced visual observers could reach the 0.02 magnitude accuracy for stars of same IC index and between.

No question for me.

As you mention for ccd imaging, we stay in fog...

The ccd chipset spectra response is not the eye spectra characteristics, under the light levels in cause.

I don't know also how to make connection between those two ways, visual and ccd, filtered or not.

Question remains.

But, for what I am sure, don't know what we do, for the moment, for getting an actual significance of data for what it is aimed by scientists...

Good skies.

Stanislas-Jean

[Redbetter]

 

Schaefer has done some good work compiling and evaluating the various sightings.  However, there is one very irritating thing he states in a 2013 publication with regard to the refuted 1842 claim by John Herschel:  "Third, not only did Herschel apparently not see below sixth magnitude, but it is very unlikely for anyone to see to V=7.06 under any conditions."  Wow.  What an absurdly incorrect assumption...which he then goes on to refute by stating, "This is not to say that it is impossible to see to V=7.06 under optimal conditions, as, for example, I have recorded Stephen O'Meara (one of the premier visual observers for the last century) as seeing stars as faint as V=8.2 from the top of Mauna Kea."

Following up on this, on Saturday night I was at my dark site with the clear, smoke-free sky running 21.4 mpsas overhead (around half a magnitude from pristine in terms of light pollution.)   I took a look around CrB to see what stars I could pick up naked eye beyond the main asterism.  Ones that I was certain of (before looking at my charts) were LY Serpens (6.89 V mag), HD 140664 (7.31 V mag), and HD 144287 (7.1 V mag).    I also had numerous indications of HD 144004 (7.69 V mag) and HD 142053 (7.5 V mag) but had less positional certainty of these two.  

 

That 7.1 mag star was not particularly difficult, and when I checked it turned out to be the very one that Schaefer claimed Herschel or anyone else would be "very unlikely to see" naked eye "under any conditions."   So while John Herschel used opera glasses rather than naked eye for this star, it is one an observer might expect to detect under the much darker skies of the 1800's.   At the time of the purported observation Herschel was 50 years old--seven years younger than I am.

 

I turned to the field around T CrB with the 20" to observe two extremely faint galaxies, IC 4587 and CGCG 137-9.  IC 4587 is ENE of T CrB, a little brighter than 15 V mag, and my notes described it as "xS, xF, ave SB, round, decent brightening to mid, w/xxF stellar core" at 278x. CGCG 137-9 is around 15.2+ V mag, masked in the following glare of a 9.3 mag field star.  I described it as "vvS/xS, xF/xxF, low SB smudge oval just W of ~10 mag star. Only slight brightening to center." at 278x.

[Redbetter]

And now we are 5 weeks from the end of Schaefer's window based on the dip.  This is the final 16% of the prediction range.  At this point I have little confidence that the dip determines the timing of the nova.  Even if it went off tomorrow night, I wouldn't attribute it more than a 50% chance of actually having been predictive...and if that it comes with a much wider set of error bars than advertised. 

 

I don't see a likely cause and effect correlation between what produces the dip and actually reaching the critical mass to kick off the nova.  However, if someone can go into detail about what is happening throughout the cycles, what the mass accumulation rate looks like at the surface and what is happening with the giant companion star, it could be enlightening and change my view/understanding.

 

On Tuesday night I roughly estimated T CrB as being the equal of the "9.8" (or whatever magnitude it actually is), maybe even a half step brighter. That was at 156x with the 20" and the stars in this aperture under dark sky are somewhat brighter than I would like for precise comparison.  Over the coming week or so we will see if this cycle's brightening continues or begins to ebb.

Edited by Redbetter, 08 August 2024 - 01:01 PM.

[stanislas-jean]

Nothing new yesterday evening 20H30 UT!

 

Regarding the processus of acquisition, it is well admitted by unistellar the internal filter 400-700nm is usable with the chipset 347C.

Therefore for the ss50, internal filter 400-700nm and the 462C chipset as well.

It is to be sure the chipset is not saturated at the issue and for the beginning of the hypothetic rise 1min of exposure can be correct, less time near the maximum, 15-20s applied on epsilon Crb and Alphecca is correct.

On the 2 scopes dark are applied already, automatic in the processus.

Star comparisons would be the gaia catalog involving 0.1-0.05 magn. uncertainties, the tycho catalog up to magn;12.1.

If this is enough this is suiting me.

Good skies.

Stanislas-Jean

[canukLX90]

Astrodon NIRL and L filter images for interest.  T CrB appears to be brighter in the NIRL band >700 region.

 

Attached Thumbnails

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[stanislas-jean]

Hi,

Here is a great information!

Picture in NIR segment with data.

Good skies.

Stanislas-Jean

[Redbetter]

Of course it is brighter in the red, that is the nature of the system, normally dominated by the light of the red giant.  That is why the star shows up red in images.

[Tropobob]

Unfortunately, there is no visibly-obvious change tonight.  (I just finished checking.)

[Sebastian_Sajaroff]

I observed it 2 nights ago. Still ~ mag 10

[Tropobob]

There is still no change.  I checked it about 20 mins ago.  

[PEterW]

I note that CrB is west of south after sunset and so the window of observing if/when this thing pops would appear to be closing. Hoping for either a quick bang or a nice delay till the spring….

Peter

[Tropobob]

No change tonight either.  

 

I keep reporting this because the Moon is bright atm and I think a lot of people monitor this with imaging, but they stop doing this under bright moonlight.  (I am just assuming: I could be completely wrong.)

 

A lesser reason is that for me, my night is the day in the USA. So my observations gives an indication of the current status of T Corona Borealis when it is not visible to readers in the USA. 

Edited by Tropobob, 16 August 2024 - 06:17 AM.

[Dave Mitsky]

There's a webinar on T CrB at 9:30 a.m. EDT tomorrow.
 

https://www.cloudyni...r#entry13610126

[Tropobob]

Nothing has happened again today.   

[stanislas-jean]

No sensitive variation on T Crb.

If nothing occurs for next short times, this mean the physical model is failing.

Period favorable is not achieved nevertheless.

Good skies.

Stanislas-Jean.

[Tropobob]

There are still no changes, as at 10 minutes ago.   

[Tropobob]

Nothing again, as at 10 mins ago. 

 

Conditions are much more challenging tonight with the SuperMoon and clouds becoming a nuisance.  (Its looks like my fortunate run of clear nights may be just about be ending.)  

[Tony Cifani]

Nothing again, as at 10 mins ago. 

 

Conditions are much more challenging tonight with the SuperMoon and clouds becoming a nuisance.  (Its looks like my fortunate run of clear nights may be just about be ending.)  

Thanks for checking. I'm excited to see this happen.

[Dave Mitsky]

There's a webinar on T CrB at 9:30 a.m. EDT tomorrow.
 

https://www.cloudyni...r#entry13610126

I "attended" the webinar and found it to be interesting even though the presenter's prediction of when that the nova will occur may not be accurate.

[Redbetter]

I "attended" the webinar and found it to be interesting even though the presenter's prediction of when that the nova will occur may not be accurate.

As we are closing in on a mere 3 weeks remaining in his window, did he say anything about that, such as any revisions he would like to make based on what has happened/not happened so far?  Making predictions based on a model is not a bad thing, but when the prediction seems to be failing it can reveal unexpected things about a system.  It has been my experience that we have often learned more fundamental things from such failures than the successes (since the successful predictions can still be coincidental.)  That includes personal experiences during troubleshooting.  

 

Was there anything particularly new/interesting that you came away with that you were unaware of before?

[stanislas-jean]

Hi,

A picture of T Crb taken during the blue moon, strong moon light with the evscope equinox2, 1min exposure.

Still nothing new.

Good skies.

Stanislas-Jean