Dear AB friends,
Increasingly I am struck by the depth and beauty of some of the wide-field images posted here on Astrobin.
I find myself increasingly using some of these images - including those I have generated myself - to act as a substitute sky atlas to find objects for follow-up study.
This led me to thinking whether AB users could work together to produce an atlas of the sky that would be of general use to everyone.
Now AB is an incredibly valuable resource with many hundreds of thousand images already, but I am not sure it it has the uniformity, homogeneity and completeness that would characterise a true survey. I may be wrong in this assumption, and I would be happy to be corrected below. [The wonderful heat map of image centres on AB does suggest that the entire sky is well covered with images here, but the real question is how uniform is the image data]
There are many other surveys out there, but none designed specifically for those of us looking for nightly targets. I use telescopius and the DSS, but the reproduction and uniformity still make in sub-optimal (at least for me). And none to my knowledge that has such a crowd-sourced origin, which I think it kind of cool. Not to say potentially good promotion for AB. [I am also writing this in the shadow of the IP theft discussion, and I really wanted to spotlight the potential for good the internet, particularly this community, has.]
Having been a professional astronomer, associated with a number of surveys I noted down what I would want from a survey design to maximise its usefulness with the bracketed values initial suggestions]
1) Regular field centres, with 10-20% overlap. [10degree field centres, 15x15 degree areas, mosaicing likely to be required ]
2) Uniform pixel scale [10arcsec/pix]
3) Uniform passband/colour [RGB or OSC]
4) Uniform depth and image quality. [SNR=60 at 22.5mag/arcsec^2, standard PI WBPP processing pipeline with SPCC and BXT/NXT]
Since the sky just over 40000 square degrees, then field centres spaced 10 degrees apart would result in a survey of just over 400 separate areas., with individual fields being 12 x 12 deg in size.
To some extent, this is tailored to the type of survey equipment that appears to be quite common on AB - the fast 135mm telephoto camera lens. Such an area could be covered in two overlapping panes using a full frame sensor or four x APSC size at a scale of 10arcsec/pixel.
Longer focal lengths up to 200mm would also be suitable (more mosaicing required, and some binning up) and down to 100mm (no or little mosaicing - but possibly some drizzling)
The passband would initially be broadband - achieved either through LRGB or OSC.
Uniformity will be crucial. Although I would not propose to make a mega-mosaic about of all the fields, people would need achieve a degree of uniformity over the panes contributing to their individually mosaiced frame. Clearly there are many out there who can do this brilliantly well, but until recently I struggled. However, I do find that with the new PI WBPP processing script including local normalisation and autocrop, plus SPCC and the RC Astro Blur/Noise Xterminator tools, I can get good uniformity between moscalced panels.
Then there is the issue of depth, and the one I am the most unsure about. In a Bortle 2 sky with an f/2 system, I can get to a SNR of around 90 at 10arcsec/px for 22.5mag/arcsec in 2.5hours. This is deep - and possibly overkill. I would be interested to hear from those who might want to take part, just what a realistic limit should be. It will depend of typical camera speeds and night sky brightness, and probably should be two much more than 3 hours per panel.
Given this wonderful confluence between hardware and software, I do think the time is right to attempt something like this as a new generation of community sourced astro-photography atlas. But it needs people to do it.
At over 400 fields [field centres would be distributed randomly to volunteers based on latitude, with the poles perhaps needing some special attention]., this survey would need a few volunteers. Even if people were to do more than one patch, I don't think it feasible to do with less than 100 volunteers. And take a couple of years.
Are there then many people out there with the right kit, right skies and inclination to spend a night or two imaging a random bit of the sky for the "greater good". I don't know. And finally there is a question of workload. It is a huge job to coordinate, but I am happy to stick my hand up. Having said that, it will rely at lot on individual contributors to take processing a significant way [to the end of the linear processing regime?] following a largely prescribed pipeline. [PI being the most obvious, simply because of the number of users].
The poll included with this note might help assess whether this idea is just unnecessary, stupid, crazy or possible. Note that responses are just to assess feasibility, you are not signing up to anything yet!
Comments on the survey design parameters would also be welcome.
Clear skies!
Brian
Increasingly I am struck by the depth and beauty of some of the wide-field images posted here on Astrobin.
I find myself increasingly using some of these images - including those I have generated myself - to act as a substitute sky atlas to find objects for follow-up study.
This led me to thinking whether AB users could work together to produce an atlas of the sky that would be of general use to everyone.
Now AB is an incredibly valuable resource with many hundreds of thousand images already, but I am not sure it it has the uniformity, homogeneity and completeness that would characterise a true survey. I may be wrong in this assumption, and I would be happy to be corrected below. [The wonderful heat map of image centres on AB does suggest that the entire sky is well covered with images here, but the real question is how uniform is the image data]
There are many other surveys out there, but none designed specifically for those of us looking for nightly targets. I use telescopius and the DSS, but the reproduction and uniformity still make in sub-optimal (at least for me). And none to my knowledge that has such a crowd-sourced origin, which I think it kind of cool. Not to say potentially good promotion for AB. [I am also writing this in the shadow of the IP theft discussion, and I really wanted to spotlight the potential for good the internet, particularly this community, has.]
Having been a professional astronomer, associated with a number of surveys I noted down what I would want from a survey design to maximise its usefulness with the bracketed values initial suggestions]
1) Regular field centres, with 10-20% overlap. [10degree field centres, 15x15 degree areas, mosaicing likely to be required ]
2) Uniform pixel scale [10arcsec/pix]
3) Uniform passband/colour [RGB or OSC]
4) Uniform depth and image quality. [SNR=60 at 22.5mag/arcsec^2, standard PI WBPP processing pipeline with SPCC and BXT/NXT]
Since the sky just over 40000 square degrees, then field centres spaced 10 degrees apart would result in a survey of just over 400 separate areas., with individual fields being 12 x 12 deg in size.
To some extent, this is tailored to the type of survey equipment that appears to be quite common on AB - the fast 135mm telephoto camera lens. Such an area could be covered in two overlapping panes using a full frame sensor or four x APSC size at a scale of 10arcsec/pixel.
Longer focal lengths up to 200mm would also be suitable (more mosaicing required, and some binning up) and down to 100mm (no or little mosaicing - but possibly some drizzling)
The passband would initially be broadband - achieved either through LRGB or OSC.
Uniformity will be crucial. Although I would not propose to make a mega-mosaic about of all the fields, people would need achieve a degree of uniformity over the panes contributing to their individually mosaiced frame. Clearly there are many out there who can do this brilliantly well, but until recently I struggled. However, I do find that with the new PI WBPP processing script including local normalisation and autocrop, plus SPCC and the RC Astro Blur/Noise Xterminator tools, I can get good uniformity between moscalced panels.
Then there is the issue of depth, and the one I am the most unsure about. In a Bortle 2 sky with an f/2 system, I can get to a SNR of around 90 at 10arcsec/px for 22.5mag/arcsec in 2.5hours. This is deep - and possibly overkill. I would be interested to hear from those who might want to take part, just what a realistic limit should be. It will depend of typical camera speeds and night sky brightness, and probably should be two much more than 3 hours per panel.
Given this wonderful confluence between hardware and software, I do think the time is right to attempt something like this as a new generation of community sourced astro-photography atlas. But it needs people to do it.
At over 400 fields [field centres would be distributed randomly to volunteers based on latitude, with the poles perhaps needing some special attention]., this survey would need a few volunteers. Even if people were to do more than one patch, I don't think it feasible to do with less than 100 volunteers. And take a couple of years.
Are there then many people out there with the right kit, right skies and inclination to spend a night or two imaging a random bit of the sky for the "greater good". I don't know. And finally there is a question of workload. It is a huge job to coordinate, but I am happy to stick my hand up. Having said that, it will rely at lot on individual contributors to take processing a significant way [to the end of the linear processing regime?] following a largely prescribed pipeline. [PI being the most obvious, simply because of the number of users].
The poll included with this note might help assess whether this idea is just unnecessary, stupid, crazy or possible. Note that responses are just to assess feasibility, you are not signing up to anything yet!
Comments on the survey design parameters would also be welcome.
Clear skies!
Brian
