Hi Allan, see below re FWHM and I use the 6nm Astronomiks in the Starlightxpress camera.
Mike
Thanks Mike,
my calculations reveal that 6nm is OK where as a 3nm filter would
have been too narrow to pick up Ha given the recession velocity at 61 Mly away.
Redshift 0.005347 https://en.wikipedia.org/wiki/NGC_1232
As for FWHM my Maxim DL can measure it straight off
the FITS files 10 years later or whatever.
Thanks Mike,
my calculations reveal that 6nm is OK where as a 3nm filter would
have been too narrow to pick up Ha given the recession velocity at 61 Mly away.
Redshift 0.005347 https://en.wikipedia.org/wiki/NGC_1232
As for FWHM my Maxim DL can measure it straight off
the FITS files 10 years later or whatever.
cheers
Allan
Using 6nm filters, when deciding if I will bother capturing Ha for a galaxy, I generally use 80 million light years as a practical limit. I don't have Maxim DL.
Using 6nm filters, when deciding if I will bother capturing Ha for a galaxy,
I generally use 80 million light years as a practical limit. I don't have Maxim DL.
Mike
Thanks Mike,
sorry if I was a pain but I was always hoping you would obtain at some stage
FWHM values of less than 1 arc second at your new observatory
to make it the best seeing in Australia.
In Melbourne I'm lucky if I get 3 arc seconds -
many nights were 6 arc seconds.
Yeah, that looks pretty convincing, as does the darker sky. I know nothing about astroart, but a quick browse of astroart 8 seems to show a tool displaying FWHM . I'd encourage anyone wanting to quantify their seeing conditions to quote FWHM. These days I quote average FWHM in arcsecs for each image I post.
Thanks to your inquiry Marcus Courtesy of Allan (alpal) and using MaximDL processing software to analyse the FWHM of multiple stars across the raw Fits Luminance frames, used in this image, confirms an average FWHM of 1.7" with some figures as low as 1.644" which is pretty good and I have seen similarly sharp sub frames on all four imaging sessions done at Eagleview so far...so, fingers crossed, this proves common place up there!
Mike
Last edited by strongmanmike; 29-11-2022 at 12:25 AM.
Thanks to your inquiry Marcus Courtesy of Allan (alpal) and using MaximDL processing software to analyse the FWHM of multiple stars across the raw Fits Luminance frames, used in this image, confirms an average FWHM of 1.7" with some figures as low as 1.644" which is pretty good and I have seen similarly sharp sub frames on all four imaging session done at Eagleview so far...so, fingers crossed, this proves common place up there!
Mike
Hi Mike,
you have done well - a magnificent result for your first light picture.
I don't think anyone else here is getting such good FWHM figures?
Your frame that I checked was a Luminance frame.
I always found that the L frames were always slightly worse than any RGB frames
and that Ha frames gave the best FWHM.
e.g.
if an L frame was 3.3 arc seconds an Ha frame might be 3.0 arc seconds.
therefore your values could be a bit better with RGB or Ha frames -
maybe as low as 1.5 arc seconds?
Hi Mike,
you have done well - a magnificent result for your first light picture.
I don't think anyone else here is getting such good FWHM figures?
Your frame that I checked was a Luminance frame.
I always found that the L frames were always slightly worse than any RGB frames
and that Ha frames gave the best FWHM.
e.g.
if an L frame was 3.3 arc seconds an Ha frame might be 3.0 arc seconds.
therefore your values could be a bit better with RGB or Ha frames -
maybe as low as 1.5 arc seconds?
cheers
Allan
Thanks so much for your help Allan, yes, pretty cool indeed...not to mention that this may not be as good as it gets...who knows, be great to crack 1" one night
Thanks to your inquiry Marcus Courtesy of Allan (alpal) and using MaximDL processing software to analyse the FWHM of multiple stars across the raw Fits Luminance frames, used in this image, confirms an average FWHM of 1.7" with some figures as low as 1.644" which is pretty good and I have seen similarly sharp sub frames on all four imaging sessions done at Eagleview so far...so, fingers crossed, this proves common place up there!
Mike
Further to this and out of curiosity, Allan kindly checked out my first light image and the raw Fits subs returned a FWHM of 2.1" which is not quite as good as the NGC 1232 subs but still pretty all right! I didn't keep any subs from my night of imaging in between but the stars looked pretty good then too, so that's four nights, at least, of pretty good to excellent seeing so far, since start of Oct...so with a bit of luck, this might prove to be a regular expectation
The Full Width Half Maximum (FWHM) is a measure of the quality of an astronomical image based on how much the telescope and atmosphere have smeared a point source (stars) in an image, over several pixels in the CCD. Simply put, it describes how much a point of light spreads out due to the bluring effects of our atmosphere. At the very best sites in the World, this spread is under 1 arc sec, in Australia anything under 2" is generally considered the Holy Grail
Definitely an improvement on both darkness and seeing there Mike. I suspect you will get better seeing when you get southerlies or perhaps a high pressure sits over your position. We have seen quite good seeing at SR when those sort of conditions prevail (which is quite often) and have FWHM results around 1.4-1.7 and sometimes just a bit better. I think with your elevation you should get 1.2" in those sort of conditions with spikes at around 0.7".
I generally don't agree with the comments that Australia is mainly around 2-3". I think that might be applicable to the east coast due to the ranges being in the way of the prevailing air stream. I know there are locations in SA which get sub arcsecond seeing regularly, the upper north of the state for example (which was considered for the AAT installation due to its exceptional seeing). During the drought most places in SA had exceptional seeing and I know that seeing generally was not improved on the east coast. At SR we do get 1.4-1.8" (read via MaximDL whilst imaging) regularly and my images are distinctly sharper as a result of the location over recent years at Clayton Bay. Clayton was great during the drought where we measured with a DIMM readings as low as 0.7" for hours at a time. Sadly that diminished with the break in the drought. Seeing was generally 1.8-2.0" with only some nights around 1.4". Still quite good but not fantastic for sea level imaging.
I am looking forward to your further results to see how much more improved the imaging will be for you going forward.
Definitely an improvement on both darkness and seeing there Mike. I suspect you will get better seeing when you get southerlies or perhaps a high pressure sits over your position. We have seen quite good seeing at SR when those sort of conditions prevail (which is quite often) and have FWHM results around 1.4-1.7 and sometimes just a bit better. I think with your elevation you should get 1.2" in those sort of conditions with spikes at around 0.7".
I generally don't agree with the comments that Australia is mainly around 2-3". I think that might be applicable to the east coast due to the ranges being in the way of the prevailing air stream. I know there are locations in SA which get sub arcsecond seeing regularly, the upper north of the state for example (which was considered for the AAT installation due to its exceptional seeing). During the drought most places in SA had exceptional seeing and I know that seeing generally was not improved on the east coast. At SR we do get 1.4-1.8" (read via MaximDL whilst imaging) regularly and my images are distinctly sharper as a result of the location over recent years at Clayton Bay. Clayton was great during the drought where we measured with a DIMM readings as low as 0.7" for hours at a time. Sadly that diminished with the break in the drought. Seeing was generally 1.8-2.0" with only some nights around 1.4". Still quite good but not fantastic for sea level imaging.
I am looking forward to your further results to see how much more improved the imaging will be for you going forward.
Interesting assessment Paul, we'll see how it pans out over time, for now though I'm happy that Eagleview appears to be a significant improvement over my old site, clearly discernible, both on screen and visually through a scope... even without using MaximDL ...be nice to see less cloud on the east coast though
Quote:
Originally Posted by AdamJL
Time to buy a lotto ticket.. I'd love FWHM figures like that.
Great work, Mike. So pleased to see an image finally come out of the obsy.
Cheers Adam, oh don't worry, we have bought many lottery tickets lately...strangely none have won too much , but we got a $160 win a few weeks ago
Mike - splendid image and what a great way to kick off the new observatory!
The comments re seeing are kinda depressing for me here in Melbourne. Two years ago from my site near Hanging Rock, 1.8" was not unusual. My latest glimpse of the stars on a new moon night didn't manage better 3", and the transparency - or lack of it - quite evident. I've also noticed that measurements of the darkness have deteriorated from SQM around 21.5+ to 21.3 at best -and it shows on faint galaxies.....
Mike - splendid image and what a great way to kick off the new observatory!
The comments re seeing are kinda depressing for me here in Melbourne. Two years ago from my site near Hanging Rock, 1.8" was not unusual. My latest glimpse of the stars on a new moon night didn't manage better 3", and the transparency - or lack of it - quite evident. I've also noticed that measurements of the darkness have deteriorated from SQM around 21.5+ to 21.3 at best -and it shows on faint galaxies.....
Enough! Congrats on this great image.
Mark
Thanks very much Mark, quite happy with the preliminary imaging results
Which Hanging Rock? there are a few, I am thinking maybe the one 60km north-west of Melbourne..? From my experience, during winter and spring last year, the skies over Eagleview were utterly spectacular, returning very high SQM readings regularly in the high 21.90's maxing out at 22.05 a couple of times revealing Mag 7.0 stars, the Gegenschein and the ultra faint Zodiacal Bridge, looking like two Milky Way's in the sky, one bright one faint perpendicular to each other, the transparency was incredible... but after the Tongan explosion in January, the sky seems to have lost it's edge and SQM readings have struggled to get out of the 21.80's and I can actually see the quality has dropped just a fraction...still bloody good of course but there is a difference, hopefully that darkness will return
With a bit of luck, next year will see the last of the Tongan dust settle and a good dry El Nino back
Definitely an improvement on both darkness and seeing there Mike. I suspect you will get better seeing when you get southerlies or perhaps a high pressure sits over your position. We have seen quite good seeing at SR when those sort of conditions prevail (which is quite often) and have FWHM results around 1.4-1.7 and sometimes just a bit better. I think with your elevation you should get 1.2" in those sort of conditions with spikes at around 0.7".
I generally don't agree with the comments that Australia is mainly around 2-3". I think that might be applicable to the east coast due to the ranges being in the way of the prevailing air stream. I know there are locations in SA which get sub arcsecond seeing regularly, the upper north of the state for example (which was considered for the AAT installation due to its exceptional seeing). During the drought most places in SA had exceptional seeing and I know that seeing generally was not improved on the east coast. At SR we do get 1.4-1.8" (read via MaximDL whilst imaging) regularly and my images are distinctly sharper as a result of the location over recent years at Clayton Bay. Clayton was great during the drought where we measured with a DIMM readings as low as 0.7" for hours at a time. Sadly that diminished with the break in the drought. Seeing was generally 1.8-2.0" with only some nights around 1.4". Still quite good but not fantastic for sea level imaging.
I am looking forward to your further results to see how much more improved the imaging will be for you going forward.
Hi Paul,
we discussed it in great detail 7 years ago here: https://www.iceinspace.com.au/forum/...d.php?t=137559
I was always surprised at you excellent FWHM figures from sea level.
I think Mike will break the 1 arc second barrier one night - sooner or later -
just given that at such high altitude he's looking through less atmosphere.
There are some aspects to this discussion on measuring seeing conditions that are worth exploring further but I don't want to bog down Mike's thread more on this issue. To this end I have kicked of a discussion in this thread in the Astrophotography and Imaging Equipment forum on the relationship between FWHM measurements and the image scale of one's optical system. I am very interested in the views of others on this topic.
There are some aspects to this discussion on measuring seeing conditions that are worth exploring further but I don't want to bog down Mike's thread more on this issue. To this end I have kicked of a discussion in this thread in the Astrophotography and Imaging Equipment forum on the relationship between FWHM measurements and the image scale of one's optical system. I am very interested in the views of others on this topic.
Clear skies,
Rodney
Good idea Rod, I'm new to this myself, this is the first time I have ever considered measuring FWHM and didn't even have MaximDL. My main wish/hope, was to simply find myself able to confirm that all the time, effort and investment, to move my observatory to it's new location, was actually going to see an improvement in conditions over my last site , and not that it was somehow going to suddenly provide atacama'esque seeing I was initially just using my eye, honed over many years of looking through and imaging with, telescopes, under varying conditions and in my case actually using the same equipment at different sites, so comparisons were immediately obvious, without some new fangled FWHM palava to tell me what I could already clearly see with my own eyes ...and so far the pretty clear improvement has made me quite happy and somewhat relieved, Maama Mia, thanka goda!
I do however now have MaximDL so, added to my propensity to be mesmerised by my perfect, AP1600GTO induced autoguiding star centroid graphs (I can stare at them for hours ) I will now have fun obsessing over my FWHM from image to image, being elated on the good nights..aaaand positively depressed on the mushy nights.
We can be a funny bunch us astromoners
Mike
Last edited by strongmanmike; 02-12-2022 at 02:23 PM.
There are some aspects to this discussion on measuring seeing conditions that are worth exploring further but I don't want to bog down Mike's thread more on this issue. To this end I have kicked of a discussion in this thread in the Astrophotography and Imaging Equipment forum on the relationship between FWHM measurements and the image scale of one's optical system. I am very interested in the views of others on this topic.
Good idea Rod, I'm new to this myself, this is the first time I have ever considered measuring FWHM and didn't even have MaximDL. My main wish/hope, was to simply find myself able to confirm that all the time, effort and investment, to move my observatory to it's new location, was actually going to see an improvement in conditions over my last site , and not that it was somehow going to suddenly provide atacama'esque seeing I was initially just using my eye, honed over many years of looking through and imaging with, telescopes, under varying conditions and in my case actually using the same equipment at different sites, so comparisons were immediately obvious, without some new fangled FWHM palava to tell me what I could already clearly see with my own eyes ...and so far the pretty clear improvement has made me quite happy and somewhat relieved, Maama Mia, thanka goda!
I do however now have MaximDL so, added to my propensity to be mesmerised by my perfect, AP1600GTO induced autoguiding star centroid graphs (I can stare at them for hours ) I will now have fun obsessing over my FWHM from image to image, being elated on the good nights..aaaand positively depressed on the mushy nights.
We can be a funny bunch us astromoners
Mike
Yes, and a good point in all that is that sometimes we can get lost in the numbers and at the end of the day our eyeballs will be the ultimate judge
I know nothing about astroart, but a quick browse of astroart 8 seems to show a tool displaying FWHM 
. I'd encourage anyone wanting to quantify their seeing conditions to quote FWHM. These days I quote average FWHM in arcsecs for each image I post.
. Two years ago from my site near Hanging Rock, 1.8" was not unusual. My latest glimpse of the stars on a new moon night didn't manage better 3", and the transparency - or lack of it - quite evident. I've also noticed that measurements of the darkness have deteriorated from SQM around 21.5+ to 21.3 at best -and it shows on faint galaxies.....
and SQM readings have struggled to get out of the 21.80's and I can actually see the quality has dropped just a fraction...still bloody good of course but there is a difference, hopefully that darkness will return 
) I will now have fun obsessing over my FWHM from image to image, being elated on the good nights..aaaand positively depressed on the mushy nights.
