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Hi Gary,
ATel 9418 makes the suggestion that the H alpha emission at least may be present at times weakly even in the normal quiescent state and stays at the same absolute strength but becomes more obvious as the continuum drops (ie constant flux but increasing Equivalent Width relative to the continuum) My spectrum is not really good enough to confirm this though.
I did also have a try with the ALPY at normal resolution (Thanks to the support from the Harold Rildley grant I now have the capability to switch resolution more easily) but the SNR at this magnitude is too poor to show any more than the general continuum shape. I wonder if the Asiago team are still keeping an eye on it with the 1.2m telescope?
Robin
This time it is the confirming spectrum.
at2016gfr was discovered by Tim Puckett’s amateur team 6 days ago but was embedded in the host galaxy and too faint at mag 17.6 for a spectrum.
When I checked on Saturday there was still no confirming spectrum but it had brightened to around mag 16 so I was able to extract a spectrum (confirming it as a type Ia) using the modified ALPY 200 despite a full moon. Guider image and spectrum (compared with best fit from GELATO) attachedCheersRobin
I have a second hand 2 inch flip mirror sitting in a box, bought on impulse after I saw Bernard Heathcote’s combined spectroscopy/imaging setup a few years ago. I still have vague ideas of mounting the LHIRES and the ALPY together on the C11. The Alpy would need a focal reducer though so there may be issues bringing them to focus, let alone ideally making them parfocal.
Robin
Hi Alun,
That is an interesting setup. I have wondered myself if the guide unit (which can be the tricky part of a DIY spectrograph design) could be incorporated into other spectrograph designs. How did you couple the two together? Did you use the reflective slit from the ALPY?
Cheers
Robin
EDIT: Ah sorry, rereading I see you have two separate spectrographs/telescopes. How are you guiding the DIY higher resolution setup?
It really just covers simple applications of the Star Analyser and RSpec so if you have done any spectroscopy already or have been to any of my general spectroscopy talks (Chasing Rainbows, Science from Starlight, BAAVSS workshops etc) then it is probably not worth it. (Tom is a good software writer and speaker but he has mostly picked up his knowledge of spectroscopy from others rather than from personal experience)
Cheers
Robin
Hi Roger,
I am not that familiar with AIP4WIN but it works this way in IRIS. In IRIS, if you want the dynamic range of the combined channel (greyscale) image to be the same as for a single channel, either the multipliers for the three channels have to add up to 1 or the resulting image has to be normalised (The multipliers allow the white balance to be set correctly)
Cheers
Robin
Hi Nick,
The corresponding figures for a 150mm f5 scope under the same circumstances would be ~ 14.2/15.6
Cheers
Robin
Nick said: “I wonder what people would have thought back in 2003 when we had the last transit of Mercury if you had told them that in 2016 we’d be taking pictures like this with a mobile phone!”
Ha! Us webcammers of 2003 would have scoffed at your technology 😉
http://www.threehillsobservatory.co.uk/astro/astro_image_40.htm
This time I was on holiday in Malta and despite various attempts, failed to make contact with any astronomers there so missed it. Thanks to everyone who posted images here !
Robin
Hi Andy,
It looks like your optimisation is paying dividends. My limit at H alpha for verifying faint Be stars was around Vmag 10 with the LHIRES 2400 and C11, though these were much bluer stars of course.
Steve,
I think mag13 should be doable with your setup too. I’ve not tested the limit of my ALPY in 600 form but for example doing the same back of envelope calculation from the other end with my modified ALPY 200, I can get to mag 17, where sky background becomes an issue. The resolution of the ALPY 600 is ~4x higher and your aperture area is ~1/3 of mine giving a 12x factor overall or ~2-3 mags
Cheers
Robin
Hi David,
I modified my ALPY using a 200l/mm grism in place of the standard 600l/mm. This gives a lower resolution but still sufficient for SN classification for example. (I estimate this gives perhaps a 1.5 mag increase in sensitivity over the standard ALPY. I have been down to mag 17.5 supernovae in favourable conditions with this setup on a 280mm aperture C11 so mag 15-16 supernovae should be reachable with an unmodified ALPY)
The modification is fairly straightforward and reversible but requires a bespoke grism which Paton Hawksley (manufacturers of the Star Analyser and the supplier of the grism used in the ALPY) made for me. There are more details of my modified “ALPY 200” on my website here.
http://www.threehillsobservatory.co.uk/astro/spectroscopy_20.htm
Cheers
Robin
Hi Tony,
I have a LHIRES III and an ALPY 600. I would not say the LHIRES is more advanced as such, they just complement each other and fulfill different roles. The ALPY 600 is more “fit and forget” and although the LHIRES is an excellent high resolution instrument, the ALPY is easier to use and performs much better than the LHIRES when used at low resolution. In many ways I find that producing good quality spectra can be more challenging at low resolution than at high resolution. (eg the targets are fainter, the sky background higher and atmospheric extinction correction more important)
Regarding rough guides from acquisition to final spectrum, I gave some very general walk thoughs for Star Analyser, ALPY600 and LHIRES using Vspec and ISIS at the recent BAA workshop at NLO Sidmouth, which can be downloaded here
http://www.shelyak.com/dossier.php?id_dossier=36&lang=2
They may not be totally self explanatory though so I am in the process of writing some words to accompany the slides which hopefully should make them more useful
For ISIS, Christain Buil has some tutorials which take you through the steps, though because ISIS is continuously evolving, the current version of the program does not always match the tutorials
http://www.astrosurf.com/buil/isis/isis_en.htm
Cheers
Robin
Back in the early days of webcam planetary (and DSO) imaging. (~15 years ago) I wrote a little IR FAQ based on my experiences and those of others on the QCUIAG yahoo group.
http://www.threehillsobservatory.co.uk/astro/IR_FAQ.htm
The results achieved these days far surpass what I was getting back then though and I am out of touch with current thinking. The basic reasoning there should still be sound.
Of particular interest may be the test mentioned there I I made on Saturn with and without IR block which showed lower noise if IR was included, no loss of resolution and that it was possible to correct the colour caste caused by the IR leaking past the RGB filters.
The colour camera will almost certainly already have an IR blocking filter so you would need to find out how to remove it to test this out
Cheers
Robin
Hi James,
I would recommend checking out the tracking capability of the the Alt Az mount you are considering. This is much more demanding for Alt Az mounts as, unlike equatorial mounts where all that is needed is a single axis running at siderial rate, both axes have to run simultaneously at varying speeds under computer control. For low cost mounts you may find this rather than field rotation limits the useful exposure time. I have a vague memory of a low cost Alt Az mount (Celestron I think) which could be run in equatorial mode using a wedge which might be a better solution but this would depend on the mount drive software being able to cope with this configuration.
Cheers
Robin
A bit detailed for a forum discussion but ideally could the database fields be read from the fits header? That way the need to enter all the info for each spectrum, with possible transcribing errors could be avoided and any search could then be done based on header information (eg with this you could potentially search for say “all spectra of a particular object covering H alpha at a resolution > 5000 and an SNR > 100” )
re the display of spectra, I wonder if any of the code used this VdS spectroscopy group database might be useful. I have contacts there if interested
http://spektroskopie.fg-vds.de/index_e.htm
(follow the link on the side to “database”)
Robin
Since in principle it is possible to put any data into a fits file there is no fundamental reason why any spectrum profile could not use the fits format. The big advantage is that all the observation and reduction details can then be contained within the fits header provided apropriate keywords are included. The BeSS standard is a good starting point of course but perhaps the header could be generalised and extended to include further useful keywords/flags etc, for example to indicate things like the type of object, level of data reduction etc. Provided the keywords required by BeSS were still present, compatibility with BeSS (or potentially any other database which used a subset of the included keywords) could be maintained (Note also that the BesS database system actually rewrites parts of the the header, ignoring some keywords and filling in others based on the information in the submitted header ie the BeSS input standard header is slightly different from what is held in the database) The “BeSS standard header” generated by ISIS software for example has already been modified in this way with added keywords for the observatory coordinates for example to make it suitable for the simple but more general database (really just lists of spectra currently) already being developed by ARAS.
Robin
