Forum Replies Created
-
Posts
-
Could a short term solution be for the submitter to have the option to disable plate solving where it is obviously incorrect or otherwise inappropriate
Cheers
Robin
Living near the wettest place in England, dewing is ever present hazard for me but with this specific ATIK camera model which I have been running for many years the only time I have had a dewing problem has been when water got into an SCT when it got rained on making the air inside the telescope particularly humid. The dew then was on the outside of the camera window and drying out the telescope solved the problem. If this is a reoccurring problem (eg with an open tube telescope) this is where a specific dew heater for the camera could help. The other possibility though is dewing internal to the camera, either on the inside of the camera window or on the sensor cover glass (this can actually be frost if the sensor is cooled,as here). In the ATIK cameras, this is prevented by making the chamber in front of the sensor hermetically sealed and the air kept dry by a desiccant tablet. If the dewing is on the inside it is because the air in the chamber has become wet (either over time or because the seal has failed) In this case opening the chamber in a warm dry environment, introducing dry air and recharging the desiccant as ATIK recommend will solve the problem, though the solution may be temporary if the chamber is leaky.
Cheers
Robin
The ability to upload multiple images against an observing report rather than having to construct a composite image would be useful eg
https://britastro.org/node/23284
Robin
It could be the desiccant tablet needs changing. This is easy on the later ATIK cameras but you have to take the back off the 314 to get to it. I have not yet had to do it but have this page bookmarked in case I do
https://forums.atik-cameras.com/index.php?topic=571.0
Cheers
Robin
Yes it is real. I also see it in a Star Analyser spectrum I took a couple of days ago. It is a blend of several lines ~4500-4600A unresolved at the Star Analyser resolution Here it is overlaid on a spectrum from David Boyd in the BAA database (red)
(It looks quite intense relative to H gamma because H lines are narrow compared with the Star Analyser resolution so are reduced in height)
Cheers
Robin
V-I is a ratio though so should be independent of the actual flux under some scenarios eg partial obscuration by a completely opaque medium or by one which semi-transparent but absorbs equally at all wavelengths. We can therefore rule out these scenarios based on this. I agree though for scenarios where there is an additive effect eg starspots (or like your flares) the absolute magnitudes need to be considered to separate out the two components. Fortunately there is plenty of V mag data and the spectra cover the full passband so the spectra could be converted to absolute magnitude
The amateur spectroscopic monitoring was very extensive and as far as I know remains untapped by professionals. It would be interesting to know how our data fits the various models.
Cheers
Robin
I mean for identification (ie shorthand to identify the line in question) not for stating the measured wavelength. (I can measure that to a precision of up to 0.01A). In papers on astrophysics you only need to say for example Na 5890, Na 5896, He 6678, DIB 6613 etc for the reader to know the line you are talking about. That’s what I meant by avoiding the ugly decimal point.
nm I can cope with (though the need to include a decimal point when defining well known lines is ugly). It is the use of Janskys for flux in optical spectra instead of the traditional (but definitely not SI) erg/cm2/sec/Angstrom that really throws me when I see it as being based on frequency, it completely changes the shape of the spectrum.
Actually I debated that briefly. The wavelength range in the images is approximate as the dispersion is non linear and it is a crop and I could not be bothered to work out the exact wavelengths to the nearest Angstrom. I used nm as 10 Angstrom was close enough 🙂
This relatively modern paper sums it up (I did not realise before that some of these lines do not always track the dust or even each other)
When I first saw it I expected it to be atomic in origin because it looks so narrow (Think NaD or K 7699 interstellar lines) but I found no matches. Apparently it is probably (I should say possibly, nothing seems very clear from the literature I have found) formed by a high molecular weight PAH molecule but exactly which one is not clear. It is fascinating that something that is seen in so many spectra and has been known about for many decades is still a mystery
Cheers
Robin
Perfect ! Thanks David. (I had tried underlining but that did not work so did not explore further.) I have changed my recent post. I think Bold, Italic looks quite good 🙂
Cheers
Robin
An R~5500 LHIRES spectrum of Halpha/He I 6678 last night.
Lots of evolution over a day in spectra in BAA database
The interstellar line at 6613 is strong too. (I did a bit of Googling on that last night and it seems although it is thought to be molecular in origin, the species does not seem to be known. Does anyone know more about this )
Long exposure astro cameras with higher dynamic range are certainly better for photometry but I played around with 8 bit camera photometry a few years back and found it was possible to do high(ish) precision photometry with 8 bit cameras (even exoplanets, just) provided you sum many frames to get the counts. eg
http://www.threehillsobservatory.co.uk/astro/Photometry_GO_Com.htm
http://www.threehillsobservatory.co.uk/astro/TrES_1.htm
One thing to watch though with these cameras is that the gamma is set to 1 so the response is linear.
Cheers
Robin
http://www.astronomerstelegram.org/?read=14224
The confirming spectrum was taken with an ALPY600 and 10 inch telescope
(Here it was clear earlier last night but the arrival of the alert in my in box coincided with that of the clouds)
Robin
Another spectrum at ~12 days past maximum. Still bright at ~mag 14.5 but interfering moonlight reduced the SNR. Significant evolution since the pre maximum spectrum
https://britastro.org/specdb/data_graph.php?obs_id=8176%2C8020&multi=yes&legend_pos=ne
but still a good match to a typical type Ia
