[AZ-Observing] Re: SN 2011fe in M101
- From: Jeff <phxjeff@xxxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Wed, 31 Aug 2011 15:24:17 -0700
Hi Ken,
Like most astronomy it depends on the size of the telescope and length
of exposure. It also depends on if you are doing low resolution or
high resolution spectroscopy. The low resolutions, e.g., with a Star
Analyser, can go very faint. I believe I saw some 13th magnitude
spectra with a SA and 8" telescope. I think it was a fairly long
exposure, however. You can do SN (10th mag) easily with a SA and 8"
scope. Meteor spectroscopy can be done with just a DSLR and SA. I've
seen some really neat results of that.
From the Star Analyser User Manual (download at
http://www.patonhawksley.co.uk/faq.html#ten)
:
10 How faint an object can I record?
Like normal astronomical imaging, it depends on the size of telescope,
sensitivity of the camera you are using and your sky conditions, but
because the light from the object is spread out across the camera
detector, objects need to be perhaps 5-6 magnitudes brighter than for
a normal image. (This is one of the reasons professional telescopes
tend to be so huge!)
In practise, the spectrum of the brighter planets and hundreds of
stars down to mag +4 can be recorded using a modest 8 inch (200mm)
scope and a sensitive webcam or planetary imager such as the Meade LPI
or Celestron Neximage. Given good sky conditions, and using the same
aperture telescope with a sensitive monochrome CCD imager such as the
ATIK 2HS, SAC8, DSI Pro, Starlight Express MX5, SC3 modified webcam
etc, recording the spectra of objects down to mag +13 is possible,
allowing the measurement of quasar redshifts and the classification of
bright supernovae to be performed! Integrating Video camera such as
the Mintron 12EV, Stellacam etc and long exposure colour imagers such
as the Meade DSI, SAC7 ATIK 1/2C, modified colour web cams etc will
reach intermediate magnitudes, to record bright comets or the
fascinating supernova candidate Wolf Rayet stars for example.
For my Lhires III with 2400 l/mm grating on my 12" scope I am limited
to fairly bright stars. From the Lhires III manual for my grating and
a SNR of 50 and 60 minute exposure:
Limiting
Telescope Magnitude
128 mm F8 6.5
200 mm F10 6.7
280 mm F10 7.1
355 mm F11 7.2
For units with lower resolution gratings (e.g., a 300 l/mm grating)
Telescope Magnitude
128 mm F8 10.4
200 mm F10 10.7
280 mm F10 11.0
355 mm F11 11.2
Come to Stan's Meeting/Star Party this fall and learn more. Check with
Stan on the details.
Jeff
Hopkins Phoenix Observatory
(187283)
Counting Photons
Phoenix, Arizona USA
www.hposoft.com/Astro/astro.html
International Epsilon Aurigae Campaign
http://www.hposoft.com/Campaign09.html
On Aug 31, 2011, at 2:54 PM, Ken Sikes wrote:
> Jeff,
>
> I briefly looked at the RSect site, how faint of a star can one work
> on ?
> The demo I think used a bright star
>
> Ken Sikes
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