Forum Replies Created
-
Posts
-
That’s a very worthwhile thing to do.
IRAF is used by lots of people to very good effect – especially by professionals. People can save a lot of effort and money this way, but the learning curve can be steep. Did much of the IRAF command line code get integrated into GUIs?
Could a case be made for doing this under Cygwin? Does IRAF run under that? What are the advantages? I know STARLINK has appeared under Cygwin.
Yep. AstroArt6 can do photometry, astrometry and relative photometry (batch processing). Look under the Tools options. You have to set up the Star Atlas so its looking at the same lump of sky as your image, which can be a little fiddly, but it works well enough. When I was measuring images of PV Cephei it seemed to produce pretty acceptable results – though I cannot say precisely how accurate as I wasn’t using a V filter.
I find AstroArt very easy to use, but I have been using it since version 3 🙂
Thanks for the sanity check Callum. Have checked my files and the £15k system I worked with was SWIR and purchased about 4 years ago and worked at 12bits. Didn’t realise they were so much more sanely priced now (though still out of range for us mortals).
Which of the Kites was that price for?
I thought EMCCDs usually clock in at around £15,000 so they are a bit of a niche market. Hope you manage to find a donor.
The QE can be very good – and some go out into NIR (1.8micron) but many are stuck with a maximum integration of 1/25 seconds, a slightly unpredictable gain control and an 8 bit output format. So for dim targets its probably actually cheaper to co-mount 2 OTAs and use 2 CCD cameras at the same time (arranged so the start of readout of one initiates the integration of the other).
Nice idea though.
Am curious.
What is it people generally use AIP4WIN for?
Which parts of the image/data process is it seen as essential for?
There are obviously alternatives for much of what it does.
Yep. Defect pixels are those that cannot be relied on: being either too sensitive, too insensitive or just plain whacky in their behaviour. When a chip contains that many pixels its not surprising that a few are not perfect.
I also tend to create my defect map using the master dark. I measure the standard deviation and image background (Statistics option if using AstroArt) of the dark and then set the threshold at background + 5 x standarddev. The Starlight 694 I use doesn’t have many defective pixels and that usually cleans them up. My approach is overkill perhaps, but its adaptive and does lend itself to processing automation – I still sometimes use the Starlink CCDPACK image reduction system under Linux.
But if you always use the same camera temperature and binning, then a hardwired threshold derived by experiment should be fine – as Robin has found.
It is usually the case that the best way to change an organisation, is from within. Why not stand for Council?
Alternatively, write a paper correcting the perceived error or start a thread here.
Its worth remembering that your suggestion opens the way to the vindictive pedant whose only pleasure is criticism – and astronomy has some of those. We’ve seen it in the past. Its not fun to watch.
Take your point. 1100 announced 2011. The 70D in 2013.
Also agree that the handling of noise is important. The later Canon DIGICs do seem better at that.
Anyone out there with new and shiny cameras willing to try the same thing and share the results?
With a little filtering and a comparatively small aperture, its suprisingly easy. I recall an afternoon session at the Cody Society using their 150mm F15 to spot stars of 4th magnitude (hard) and 3rd magnitude (pretty easy) when looking at the darker parts of a blue sky. The scope wasnt GOTO, but did allow very good manual pointing accuracy.
Wish there had been some initiative like this available in1994 when CCD imaging was just becoming available to amateurs.
Or was there and I just didnt notice?
Was it just me, or is the point spread function for the “event” tighter than that of the moon seen on the extreme image right?
Any dusty debris seen by imagers subsequently?
Well you certainly cannot rely on the Bayer matrix to do the filtering. On a Lumix I own theres enough leakage of light to take a photo during the day with a filter that cuts off light at a shorter wavelength than 820nm. Green lawns look like snow!
In the UK – given its dirty and humid atmosphere – hard UV certainly isnt a problem (well, it didnt seem to be for me) though the definition of where the UV starts and blue ends may vary and the big worry is how fast a refractors focus goes to pot as you move toward the blue – may get bad sooner than you think.
But even with reflective optics, the colour balance will still be off as the blue and green images will still contain a contribution from the near infrared – that can blur out fine contrast features.
Personally, if the camera already has a blocker but you have a professional quality blocker to hand its worth experimenting using the camera with both filters, your professional filter only and with only the in-camera filter and comparing. You do have to be very certain of your filter quality.
Sorry Martin. Just for once I reckon you are wrong. I reckon I have a book out that sells slower than yours.
Was impressed by the fact it was on a russian free download site and on one of the US rent-telescope time type sites as a pdf before I even had a hard copy in my hand.
I’m amazed anyone ever writes any books anymore.
I think you will find that laser ranging sites like Herstmonceux do not issue NOTAMs every night they work. I believe they operate by always having staff with the system and making sure the sky is clear of aircraftby visual inspection while the laser is active.
Their laser is a tad brighter than those most people use at star parties.
No reason at all you cannot do photometry this way. Keep the exposure short, position the target at the field centre and use a comparison star close to it and if the flat fielding and dark subtraction is okay you will get good results.
Of course DSLRs are a bit noisy, so combined with the use of a short xposure it can mean a lot of exposures are needed.
In Wiltshire, not far from Salisbury Plain, there were some tasteful high altitude wisps of cloud before the penumbral stages, but by the time the eclipse was underway they had mainly melted away leaving a clear, if not very transparent, sky.
As the night went on and the temperature dropped to 3C some mist started to form, but this was mainly near watercourses. Pretty nearly ideal conditions.
A dark eclipse with an orange tinge. If my blood looked that colour, I would see a doctor quick!
I didnt think any colour was apparent until the umbral phases. Is that the general perception or is my colour vision poor?
