STF450 companion variable?
Posted 20 February 2012 - 03:12 PM
Tonight I could see the STF450 companion clearly for the first time after several failures but only as rather dim star with may be no more than +11mag when compared for example with the about +10mag stars at the end of Ally's Braid.
This could mean that may be the STF450 companion is a variable star or fading away.
It would be nice if somebody on this forum could recheck this observation. For GoTo users - RA/DE (2000): 03h47m24s/+23°54'52"
Thanks in advance
Posted 21 February 2012 - 05:58 AM
Posted 25 February 2012 - 02:56 AM
I will anyway stay on this topic for the near future to see if there is any change in magnitude
Posted 25 February 2012 - 10:44 AM
Posted 25 February 2012 - 03:24 PM
Posted 26 February 2012 - 06:38 AM
Posted 26 February 2012 - 12:35 PM
Posted 26 February 2012 - 11:11 PM
When your original post appeared, I checked my observing log on this double. None of my notes mentioned anything amiss with the data. Finally had an opportunity to observe this pair again this evening, using a 90mm F/10 achromat at magnifications ranging from 130X to 230X.
I believe Rich's cautionary note above bears somewhat in this case. It is not uncommon for secondary magnitudes to appear fainter than their measured values. Even so, after studying this pair in various portions of the field of view, with both direct and averted vision, both glancing and staring, the pair alone and in comparison to the reddish (another problem in itself) 10th magnitude or so star directly preceding the pair, I have to agree to a degree with you. 9.1 for the secondary is a bit optimistic by a half magnitude or so. At least visually.
Thank you for posting your detailed observations on this double, and welcome to Cloudy Nights and the double star forum. Looking forward to more reports from you.
Posted 27 February 2012 - 10:30 AM
Thank you very much VanJan for spendig time on observing this pair and checking my impression. You must have dark skies to be able to use magnification up to 230X - I have here heavy light pollution and "loose" <+10mag stars if I go beyond 130X. Anyway I will have a look on this from time to time to see if there are any changes to note
Posted 05 April 2013 - 02:34 AM
Posted 05 April 2013 - 06:31 PM
Posted 06 April 2013 - 04:21 AM
Posted 22 December 2013 - 11:13 AM
Yesterday I missed a chance to get again a look at STF450 because the fog raised in the evening so fast that the clear sky got lost within a few minutes. I intended to do this in a quick session with my 60mm travel refractor because meanwhile I have sampled enough limit observations to be sure that STF450 should be not this difficult to resolve with 60mm if the advertised data is correct.
Hope now for the next chance with a stable clear sky and enough time to setup a larger scope with iris so I can go down to the limit aperture.
PS regarding 60mm scope: May be I will also try it with my C9.25 with the 60mm off axis mask delivering usually stunning crisp images with saturated color hues
Posted 23 December 2013 - 04:14 PM
But to be clear - this was no resolution of STF450 but of UCAC4-570-008469 +10.84mag at a position similar to the companion of STF450 but at a distance of ~110" and it seems not very plausible to me that a +9.1mag star should be here in between. Even with a rather small magnification of x100 there should be no problem at all to resolve such a companion at a distance of 5.7".
Posted 23 December 2013 - 04:18 PM
STF 450: 3:47:24.41 +23:54:52 (J2000). Double. Sp: A2V
Sep: 6.2, PA: 263, Year: 2008 7.29-9.1
Telescope: C-8, Observatory: Little Tycho, Date: 2007 Oct 21, Time: 03:00:00
An ordinary sort of pair in the Pleiades, quite overshadowed by the rest of
Note that the WDS data was added well after the observation was made.
Posted 23 December 2013 - 06:34 PM
So I think it likely the secondary star is fainter than the WDS listing, and could be mag 10+, perhaps 11. If it were as bright as mag 9.1 it should appear in Hipparcos.
My observation of this pair 5 years ago was with a C9.25, I didn't record anything unexpected about it at the time; but the larger aperture can disguise issues of magnitude in some cases.
Added in Edit: I had overlooked my more recent observation, mentioned here in another thread, at the end of January this year - looked at STF 450 with the 140mm refractor, and could see the close companion already at 80x, though it was more obvious at 114x.
I'll try again soon with that telescope, and with aperture stops to check how it looks at smaller apertures (probably 100mm and 80mm).
Posted 24 December 2013 - 06:57 AM
Posted 25 December 2013 - 11:25 AM
Further if I apply my pixel count method to this image and compare it with the results I got in my empirical sample for magnitude dependent size of spurious disk I also come to the conclusion that the brightness of the companion is about +10.5mag taking the magnitude of the primary with +7.21mag as reference.
Posted 25 December 2013 - 01:00 PM
Posted 25 December 2013 - 10:05 PM
Magnitude limit of the 60mm refractor? - on aperture, 2.0 mags less than a 6-inch, and a conservative mag limit for a 6-inch is 12.9 (quoted in many books). However a 6-inch often enough goes fainter, say to 13.5 - that would suggest 11.5 for 60mm. In really dark conditions I've seen some experienced observers here quote fainter mags than 11.5 seen with 60mm. So your producer of the refractor is being cautious. Better should be possible.
Posted 26 December 2013 - 02:41 AM
Posted 26 December 2013 - 06:55 AM
Fred - thanks for the explanation regarding USNO A2 magnitudes. I don't know the spectral type of USNOA2 1125-01267467 (I have the catalog on DVD at home but have at this moment no access to it) but your assumptions seem plausible.
Regarding TML for a 60mm refractor: I know that there are so many factors involved that any given number can only be a mean value with some range for deviations - but I think somewhat slightly above +11mag should be possible.
Meanwhile I checked again the photo of Chris for another reference and found also nearby HD 282973 +9.87magV according to Simbad resp. UCAC4-570-008510 +9.98mag.
To make a direkt comparison I arranged STF450A, STF450B, UCAC4-570-008469 and UCAC4-570-008469 side by side - this shows clearly that STF450B is in between UCAC4-570-008469 +10.84mag and UCAC4-570-008469 +9.98mag and certainly fainter than the latter.
Posted 21 January 2014 - 01:50 PM
I don't post here much and I don't do much double star work, but WRAK asked about this double in a photometry thread and I thought it might be interesting to look at it. So I took some video with an Edge8 and qhy5l-ii using C, g', and r' filters (Sloan). I did not have much time so I did not do an elaborate calibration or anything - and this is all raw measurement - but I think it tells the story. Basically the third star is very red, with a color index of 1.65 according to one source (described in a later note below).
Here are stacked images with no processing other than aligning and sub-sampling - and dark subtract. These are stacks of 200 frames at 100ms exposure with no quality culling. The star was lower than I wanted and I believe the atmospheric dispersion in the longer filters causes the elongation - it is not a collimation issue.
So here are the images in clear, g', and r' all at the same scale. They are *not* corrected for extinction or response of the camera, but they tell the main story - the third star is very red.
Posted 21 January 2014 - 01:55 PM
I calculate raw magnitudes and then adjust them relative to the g' value for the primary and its color index from below. This is not intended to be exact but it gives the idea of the relative colors of the stars.
Posted 21 January 2014 - 01:58 PM
I don't know how the mags are assigned or adjusted for visual observers or in the double star lists - but this is more information to go by, including captured images. It's a very red star - so it may not match the listed magnitude - depending on how it's measured.