Hi again
Ive always wanted to try and image part of the Vela Supernova Remnant, embedded in the larger Gum Nebula.
This is pushing my gear and light polluted skies hard getting it, but here it is, along with finder charts.
Image is 2x10 mins modded 350D, 10 inch F5.6 newt, UHCS filter and MPCC, processed in Iris.
Some high cloud about at the time.
Scott
Wow!!!
Another good one glade to see somone going after the faint stuff .
This would be a great area for a long exposure and get the SN up.
Now that I've ( almost ) finished messing around with the 10" SN mods maybe we can have a shoot out , your way ahead of me with DSLR processing though so I may need some help.
Thanks.
Zane, your SN would be ideal for this object. I imagine your skies would be a a fair bit darker then mine . Is your SN F3.5? gee thats nice and fast, would have no trouble capturing the Vela SN Remnant under a dark sky.
Scott
Would 100 1 minute shots work, for those who cant get polar alignment spot on for a 10 minute shot?
Hi H0ughy,
the problem with 1 minute shots is that your signal to noise ratio will be poor.
I have always gone for longer individual exposure times because it improves the signal to noise ratio especially with DSLR cameras.
Even without perfect polar alignment you should be able to do 10 minute shots - oh! that's right your relying on an autoguider. I guess it can't do it, have you even thought about replacing the autoguider with your own eyes and guiding the scope "manually" ?
Would 100 1 minute shots work, for those who cant get polar alignment spot on for a 10 minute shot?
Interesting question Houghy.
Paul is correct in that longer shots do result in improved signal to noise ratio. However, stacking 100 shots would improve the signal to noise ratio by a factor of 10 (square root of the number of shots). Stacking 10 shots only improves the S/N ratio by 3.16. Of course, the S/N ratio is much better to start with. There is some loss using the many shots idea though. Other calculations and my own experience suggests the 100 x 1min shots would be the equivalent of about 70-80 min of longer exposures.
Thanks.
heres a reprocessed version. I did it from scratch, even includingan offset image (a 1/400sec dark frame) for Iris to work on. I religiously followed the proceedure in Iris pre processing function. Then I played with the colour balance, flat fielding never seems to work properly, despite taking proper flatfields (with sheet of A3 paper over end of scope with floodlight some distance away lit), so I had to use gradient xterminator and manually dodge some darker areas out. Heres the result. I think I will re-image this with the camera n/r on in the future
Scott
Paul is correct in that longer shots do result in improved signal to noise ratio. However, stacking 100 shots would improve the signal to noise ratio by a factor of 10 (square root of the number of shots). Stacking 10 shots only improves the S/N ratio by 3.16. Of course, the S/N ratio is much better to start with. There is some loss using the many shots idea though. Other calculations and my own experience suggests the 100 x 1min shots would be the equivalent of about 70-80 min of longer exposures.
Cheers
Hi H0ughy and Itchy,
Just another tid-bit as well, ISO-200 on the Canon 300D without doubt gives me the best signal/noise ratio compared to other ISO settings. Oh and Parameter Set 2 on the camera uses less in-camera processing (DGIC or whatever they call it) of the image than does the default setting of Param. Set 1.
Just another tid-bit as well, ISO-200 on the Canon 300D without doubt gives me the best signal/noise ratio compared to other ISO settings. Oh and Parameter Set 2 on the camera uses less in-camera processing (DGIC or whatever they call it) of the image than does the default setting of Param. Set 1.
Paul
Thanks Paul. I'm not aware of what the parameter sets actually do. It would be worth a try.
Just another tid-bit as well, ISO-200 on the Canon 300D without doubt gives me the best signal/noise ratio compared to other ISO settings. Oh and Parameter Set 2 on the camera uses less in-camera processing (DGIC or whatever they call it) of the image than does the default setting of Param. Set 1.
Paul
OK for the uninitiated, what does it do and how do I find it (i have no idea, only had the canon a few weeks)
OK for the uninitiated, what does it do and how do I find it (i have no idea, only had the canon a few weeks)
geeday mate,
Param. Set 2 reduces the amount of in-camera sharpening and color enhancement, so that dark frame subtraction and subsequent computer processing will yield better results (bearing in mind you can't really astrometrically calibrate images from a DSLR, since in-camera processing alters the original data before you get to see it).
uhm err, from memory press the camera's menu button, skip to the first menu, you'll see "Parameters" change it to "Param Set 2".
Yes I guess its best to get the data as un processed as possible right off the sensor, just like in Astro CCD imagers.
Scott
That's right Scott,
Using Param Set 2, uses less in-camera colour manipulation and less sharpening of the image. But even with Param Set 2, the DGIC? processor in the camera still alters the original image data before you get to see it. It would be great is Canon had another Param Set which told the on-board image processor to just give us the image as is without any adjustment - then we'd be able to properly calibrate images and take astrometric measurements from them. Oh well - it's still a value for money astro-imager.
