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The Leuven Star Atlas – making a publication quality stellar atlas from scratch

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#1 papics

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Posted 20 June 2017 - 04:23 PM

Dear fellow atlas-enthusiasts,

 

I have been working on my own stellar atlas in my free time since March, and I have arrived to a point where I think it is worth showing, and asking opinions of the wider public. Please head over to my website and read the whole story there: http://papics.eu/?p=3969 (There are of course more and better quality sample pages over there.)

 

LSA_example.jpg

 

I would appreciate any kind of comment / suggestion / criticism (preferably constructive).

 

Best regards,

Peter


Edited by papics, 21 June 2017 - 03:32 AM.

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#2 The Ardent

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Posted 20 June 2017 - 05:00 PM

Peter
I only had a glance at your website / looks great so far.
As a long time user of the atlases you mention, please let me add some opinions.
1. Uranometria 2nd edition is my most used. It does a poor job on constellations like Cassiopeia. Poor thing is cut to pieces and difficult to navigate: for example between page 18 and 29. I'd like a large (size of Sky Atlas 2000) chart centered on Gamma Cas.
2. Rosette Nebula area is cut up also. There are some others.
3. I like the increased scale combined with brightness indicators or ISDA.

#3 The Ardent

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Posted 20 June 2017 - 05:08 PM

Another suggestion: instead of the entire sky, an atlas centered on the Galactic equator , and 15-20 degrees wide?
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#4 Steve Cox

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Posted 20 June 2017 - 06:49 PM

Looks really nice to me, congratulations.  Of course, if there is anything I'd have to critique, I'd only suggest you need to add a magnitude scale to the page somewhere.



#5 vkhastro1

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Posted 20 June 2017 - 07:19 PM

 Very impressive star atlas - an amazing amount of work !!

The Milky Way boundary gradients and dark nebulae outlines are very useful.


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#6 Ragaisis

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Posted 20 June 2017 - 08:18 PM

Shut up and take my money! ;-)

 

Seriously, I'm LIKING this!



#7 papics

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Posted 21 June 2017 - 01:59 AM

Peter
I only had a glance at your website / looks great so far.
As a long time user of the atlases you mention, please let me add some opinions.
1. Uranometria 2nd edition is my most used. It does a poor job on constellations like Cassiopeia. Poor thing is cut to pieces and difficult to navigate: for example between page 18 and 29. I'd like a large (size of Sky Atlas 2000) chart centered on Gamma Cas.
2. Rosette Nebula area is cut up also. There are some others.
3. I like the increased scale combined with brightness indicators or ISDA.

Hi Ray, thanks. Concerning the cutting up of objects, I looked through and the only object that is a bit cut up is the Simeis 147 (Spaghetti Nebula), but it is on two neighbouring pages, so it just needs a flip of a page. There is also a relatively large buffer between neighbouring pages (unlike in Uranometria, where there is no area repeated), this is minimum half degree in declination (so the same half degree strip is plotted on both neighbouring pages), and minimum 3 minutes in RA (much more towards the poles), this way I can make sure that objects plotted on the edges of one page will still be visible in the neighbouring page (and actually if an object is on the edge of one page, that will be further from the edge on the other, thanks to the buffer zone).



#8 papics

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Posted 21 June 2017 - 02:01 AM

Looks really nice to me, congratulations.  Of course, if there is anything I'd have to critique, I'd only suggest you need to add a magnitude scale to the page somewhere.

Hi Steve, thanks! If you look at the sample pages on my website you will notice that the odd pages have the magnitude scales (and all legends that are stellar or connected to celestial line objects), while even ones the legends for non-stellar objects ;)


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#9 catalogman

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Posted 22 June 2017 - 08:00 AM

The readability of the fonts and the suppression of the coordinate grid
are a great improvement over other atlases (esp. anything by Wil Tirion).
The coordinate grid is too bold in the samples on your web-page but the
grid is improved in your attached sample.

 

It is not clear from your sample charts if the arrangement is by increasing
or decreasing RA. If a user wants to rearrange the charts by his preference,
the chart pointers are cleverly placed so they won't interfere with the punch
holes of a three-ring binder. (Maybe move the chart numbers slightly so that
they also don't interfere, and slightly extend the thinner page margin.)

                                                            ---

Unfortunately, the SAC as a database is a very poor choice -- the coordinates
are crude (nearest 0.1m RA, 1' Dec) and there are many ID mistakes. But I see
that you know this and have tried to make corrections: IC 1266 on sample chart
272, for example. (Did you also correct PK 7 + 1.1 = IC 4670?)

 

The most questionable feature of your new atlas is the use of color.  Under a
red light, the observer sees the blue Milky Way and green nebulae as shades of
gray and other colors are not visible at all.  An unbound B&W Field edition of
your atlas would be much less expensive and just as useful.

                                                           ---

When you do find a publisher for the Leuven Star Atlas, please consider using
a major publisher. As a rule, booksellers do not sell works from small or
do-it-yourself publishers, which is why copies of European atlases like Atlas
Coeli Novus 2000.0 and others in your link are so hard to find.

 

                                                                                       -- catalogman


Edited by catalogman, 22 June 2017 - 08:00 AM.

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#10 turtle86

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Posted 22 June 2017 - 09:07 AM


Very impressive work! Looks like you're succeeding in combining the best features of Uranometria, Sky Atlas 2000 and Interstellarum. I actually like your color choices and logical reasons for them. Even if some of them won't show up well at night with a red flashlight (frankly a problem with just about any color in field use), you do avoid red (which would be invisible) and it is to be remembered that the atlas isn't just for field use anyway but also for use as a desk reference. Sure, a black and white atlas might work better in the field, but it's very hard for a paper atlas to be all things to all people, and besides, there are already several excellent black and white atlases out there (Uranometria, Millennium, and Great Atlas of the Stars). On the other hand, there are not a lot of deep printed atlases in color (nothing deeper than Interstellarum I'm aware of anyway), so I think your atlas will be a welcome addition.
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#11 Tony Flanders

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Posted 22 June 2017 - 09:07 AM

Unfortunately, the SAC as a database is a very poor choice -- the coordinates
are crude (nearest 0.1m RA, 1' Dec) and there are many ID mistakes. But I see
that you know this and have tried to make corrections: IC 1266 on sample chart
272, for example. (Did you also correct PK 7 + 1.1 = IC 4670?)

I don't agree with that statement. All catalogs have ID problems; the SAC database is better than most.
 
As for positional precision, why would anybody ever want to know the position of an object better than one arcminute? The overwhelming majority of deep-sky objects are many arcminutes across, so the position will in any case depend on the somewhat arbitrary choice of what constitutes the object's center.
 
In any case, one arcminute is invisible on the scale of a paper atlas.


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#12 Tony Flanders

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Posted 22 June 2017 - 09:28 AM

This is very impressive. I am especially awed by your undertaking to draw the outlines of all those nebulae; that's an overwhelmingly large amount of work, requiring knowledge and judgment as well as vast effort.

 

Obviously, this atlas competes head-on with the Interstellarum Deep-Sky Atlas; they have very similar depth and scale. That's likely to be a problem in getting it published, since the IDSA, for all its many flaws, has already occupied that niche. I would have to spend a long time comparing your atlas to the IDSA both at my desk and outside while observing to comment intelligently on their relative merits.


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#13 catalogman

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Posted 22 June 2017 - 12:13 PM

<snip>  All catalogs have ID problems; the SAC database is better than most.
 

 

You're referring to the "M91-type" objects for which authorities don't always agree.

 

I'm referring to obvious errors, like NGC 2474 = UGC 4114 and NGC 2475 = PK 164+31.1. The

UGC object is actually the double galaxy NGC 2474/5; the planetary is listed correctly in another
line of the catalogue, which makes the error obvious. The OP acknowledges that "[the SAC] has

quite a few mistakes" (see Section 3.3.3 of his homepage).

 

 

<snip>
 
As for positional precision, why would anybody ever want to know the position of an object better than one arcminute? The overwhelming majority of deep-sky objects are many arcminutes across, so the position will in any case depend on the somewhat arbitrary choice of what constitutes the object's center.
 
In any case, one arcminute is invisible on the scale of a paper atlas.

 

 

On deeper charts, faint galaxies (which make up most DSO's) and planetaries require much greater

accuracy. On the OP's atlas, the PA of a small DSO near a star could be visibly affected by 1' accuracy.

 

If I purchase any star atlas, I expect it to use the best data available.   

                                                                                                                       -- catalogman



#14 papics

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Posted 22 June 2017 - 01:14 PM

First of all, thank you everyone for the feedback, and keep the criticism coming! ;)

 

The readability of the fonts and the suppression of the coordinate grid
are a great improvement over other atlases (esp. anything by Wil Tirion).
The coordinate grid is too bold in the samples on your web-page but the
grid is improved in your attached sample.

 

It is not clear from your sample charts if the arrangement is by increasing
or decreasing RA. If a user wants to rearrange the charts by his preference,
the chart pointers are cleverly placed so they won't interfere with the punch
holes of a three-ring binder. (Maybe move the chart numbers slightly so that
they also don't interfere, and slightly extend the thinner page margin.)

                                                            ---

Unfortunately, the SAC as a database is a very poor choice -- the coordinates
are crude (nearest 0.1m RA, 1' Dec) and there are many ID mistakes. But I see
that you know this and have tried to make corrections: IC 1266 on sample chart
272, for example. (Did you also correct PK 7 + 1.1 = IC 4670?)

 

The most questionable feature of your new atlas is the use of color.  Under a
red light, the observer sees the blue Milky Way and green nebulae as shades of
gray and other colors are not visible at all.  An unbound B&W Field edition of
your atlas would be much less expensive and just as useful.

                                                           ---

When you do find a publisher for the Leuven Star Atlas, please consider using
a major publisher. As a rule, booksellers do not sell works from small or
do-it-yourself publishers, which is why copies of European atlases like Atlas
Coeli Novus 2000.0 and others in your link are so hard to find.

 

                                                                                       -- catalogman

 

The grid is actually pretty thin, but since the atlas is rendered in vector-graphic format, if I convert these pdf files to png samples, or when looking at them on the screen of a computer (without zooming in a lot), they are rendered thicker, that's just how pdf viewers and conversions work. If you download the original pdf samples and print them with a good quality printer you will see that they are actually really thin.

 

The arrangement is in decreasing RA (you can actually see it in the filenames on this image: http://papics.eu/blo...2017_LSA-11.png), that is the only thing that makes sense, in my opinion. Otherwise you have to fold to the opposite direction than where you seemingly want to go (e.g., you would want to see the field that is on the right edge of a double page but then you would flip to the left?!?). I hope I am not the only one who thinks this is the only logical choice :)

 

I am fully aware of the issues with the SAC, but this was a very good database to set up things with, since it had all the different kind of objects, so I could write all the necessary functions to display them. Also, it has a good list of objects that are interesting for amateurs, but for example, it does not contain the complete NGC/IC catalog. It is true that a good star atlas must have a good catalog, not only fancy design, and I also feel like that while my stellar catalog is perfect, the deep sky catalog is not (as mentioned in the future plans section). But I have the framework set up now, I could always set up a different catalog to feed into it, and I can make things better. Now of course here comes the difficult part. Building a custom deep sky catalog is not a one day job, and I was playing around with this atlas in my free time. I need to see what are the best options here, and I am of course open to suggestions. The ID mistakes in SAC mainly come from them not crossmatching separate catalogs when building their database, that seems quite clear to me. But back to building a DSO catalog from scratch: just yesterday I received - from an amateur - a catalog of ~10200 asterisms. But I don't want to fill the atlas with asterisms (of course some of these are actual NGC OCs, that I either already have, or do not mind). Then how do you decide which ones to include? And then if someone of the millions of amateur astronomers has a favourite object and it is not included that will be a tragedy for them. I know. It would be to me. But you can not include all objects in a printed atlas, for that you have the computers and the various planetarium software. Here you need a good balance in objects of different types, and a sensible magnitude and size range. I can not include 50000 objects on a 344 page atlas. There is just not enough space. Concerning the coordinate precision, on the current scale having a 0.5' precision for the DSO (since the coordinates are rounded to the closest arc minute, so the actual precision is minimum 0.5', and not 1') does not hurt (we are talking about +/-0.13 mm, when 16 mm = 1 degree), since even the smallest 10th magnitude star is much larger than that, and the symbol size for the smallest planetary nebulae is in the same ballpark. Yes, in a 4x zoom-in close up chart this would be already up to a 0.5 millimetre, and that is not something I want. So yes, I am not 100% satisfied with the DSO catalog, but it is complicated.

 

Thanks to how the atlas is set up, I could produce a BW version in less than a minute (just change a few colour variables in the script, nothing else), so that is not an issue. One of my main motivations in this project was to make a pretty atlas, so the main goal is still the colour version.

 

Before considering any publisher, I want to get to a level where I am fully satisfied. And I am very critical, so that is still far. :)



#15 Starman1

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Posted 22 June 2017 - 03:25 PM

 

Peter
I only had a glance at your website / looks great so far.
As a long time user of the atlases you mention, please let me add some opinions.
1. Uranometria 2nd edition is my most used. It does a poor job on constellations like Cassiopeia. Poor thing is cut to pieces and difficult to navigate: for example between page 18 and 29. I'd like a large (size of Sky Atlas 2000) chart centered on Gamma Cas.
2. Rosette Nebula area is cut up also. There are some others.
3. I like the increased scale combined with brightness indicators or ISDA.

Hi Ray, thanks. Concerning the cutting up of objects, I looked through and the only object that is a bit cut up is the Simeis 147 (Spaghetti Nebula), but it is on two neighbouring pages, so it just needs a flip of a page. There is also a relatively large buffer between neighbouring pages (unlike in Uranometria, where there is no area repeated), this is minimum half degree in declination (so the same half degree strip is plotted on both neighbouring pages), and minimum 3 minutes in RA (much more towards the poles), this way I can make sure that objects plotted on the edges of one page will still be visible in the neighbouring page (and actually if an object is on the edge of one page, that will be further from the edge on the other, thanks to the buffer zone).

 

Incorrect.  Uranometria has an 8min of RA (2 boxes) overlap between successive charts horizontally and 1° of Declination, vertically.

It doesn't have an overlap across the binding because left and right charts are one continuous chart.


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#16 Starman1

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Posted 22 June 2017 - 03:42 PM

Dear fellow atlas-enthusiasts,

 

I have been working on my own stellar atlas in my free time since March, and I have arrived to a point where I think it is worth showing, and asking opinions of the wider public. Please head over to my website and read the whole story there: http://papics.eu/?p=3969 (There are of course more and better quality sample pages over there.)

 

LSA_example.jpg

 

I would appreciate any kind of comment / suggestion / criticism (preferably constructive).

 

Best regards,

Peter

I like it, and think your approach is good, and that the atlas will be very useful for many observers.

The number of DSOs is way too few for my 12.5" aperture, used in dark skies, but, like the Millenium Sky Atlas a while back, that doesn't mean it's not a good atlas.

If you added up to 30,000 or more objects, an atlas of this scale would become very crowded and the overlap of identifying designations a real problem.

I like your approach to plotting the Milky Way, for example, and large nebulae.

 

However, there is always a risk in using connect-the-dots depictions of constellations, as there have been several different pattern sets in the last 40 years, and some are not very good (i.e. don't connect

enough dots).  To use such on a star atlas of large size, such as the Tirion Atlas 2000, helps with page identification at a glance.  On a larger scale atlas, however, the section of a 

constellation so depicted doesn't help that much, and it could even be a problem if the observer didn't like the constellation patterns you picked.  I'd advise against it for general distribution,

even if you like it for yourself.

 

The magnitude 10 limit for stars is a good one.  Kudos.

 

As for the SAC database, be aware that all its star cluster positions (open and globular) have been corrected per the data in the book "Star Clusters" by Archinal & Hynes and represent the most current, corrected, catalog of star clusters available.  You state that you made corrections to DSO positions.  I hope no correction was applied to star clusters, since much other on-line data is filled with errors--especially for catalogs like the Ruprecht clusters, where many on-line lists had positional errors of up to a degree (!).  I have no comment about other coordinates, since I did not have a hand in correcting them, nor checking them against a modern, corrected, reference, like NED or SIMBAD.

 

I also do not know if the positions and identifications of NGC objects in your list have been corrected per the most recent Historically-corrected data from The NGC/IC.org group or Wolfgang Steinicke's more recent corrections.  In some cases, continuing an error (the NGC90/91 switch, for example) may be called for because of all the literature concerning these two objects, all of which used incorrect identifiers, i.e. if 100 years of scholarly studies are all in error, then perhaps the error has become the accepted norm, regardless of the historical roots of the error.  I hope you used at least the NGC/IC.org data or Steinicke's data for your NGC information rather than the older, and more error-ridden data often found on-line.


Edited by Starman1, 22 June 2017 - 03:52 PM.


#17 papics

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Posted 22 June 2017 - 05:34 PM

First of all, thanks for the feedback!

 

 

 

Peter
I only had a glance at your website / looks great so far.
As a long time user of the atlases you mention, please let me add some opinions.
1. Uranometria 2nd edition is my most used. It does a poor job on constellations like Cassiopeia. Poor thing is cut to pieces and difficult to navigate: for example between page 18 and 29. I'd like a large (size of Sky Atlas 2000) chart centered on Gamma Cas.
2. Rosette Nebula area is cut up also. There are some others.
3. I like the increased scale combined with brightness indicators or ISDA.

Hi Ray, thanks. Concerning the cutting up of objects, I looked through and the only object that is a bit cut up is the Simeis 147 (Spaghetti Nebula), but it is on two neighbouring pages, so it just needs a flip of a page. There is also a relatively large buffer between neighbouring pages (unlike in Uranometria, where there is no area repeated), this is minimum half degree in declination (so the same half degree strip is plotted on both neighbouring pages), and minimum 3 minutes in RA (much more towards the poles), this way I can make sure that objects plotted on the edges of one page will still be visible in the neighbouring page (and actually if an object is on the edge of one page, that will be further from the edge on the other, thanks to the buffer zone).

 

Incorrect.  Uranometria has an 8min of RA (2 boxes) overlap between successive charts horizontally and 1° of Declination, vertically.

It doesn't have an overlap across the binding because left and right charts are one continuous chart.

 

You are right, I mixed things up here.

 

 

Dear fellow atlas-enthusiasts,

 

I have been working on my own stellar atlas in my free time since March, and I have arrived to a point where I think it is worth showing, and asking opinions of the wider public. Please head over to my website and read the whole story there: http://papics.eu/?p=3969 (There are of course more and better quality sample pages over there.)

 

 

 

I would appreciate any kind of comment / suggestion / criticism (preferably constructive).

 

Best regards,

Peter

I like it, and think your approach is good, and that the atlas will be very useful for many observers.

The number of DSOs is way too few for my 12.5" aperture, used in dark skies, but, like the Millenium Sky Atlas a while back, that doesn't mean it's not a good atlas.

If you added up to 30,000 or more objects, an atlas of this scale would become very crowded and the overlap of identifying designations a real problem.

I like your approach to plotting the Milky Way, for example, and large nebulae.

 

However, there is always a risk in using connect-the-dots depictions of constellations, as there have been several different pattern sets in the last 40 years, and some are not very good (i.e. don't connect

enough dots).  To use such on a star atlas of large size, such as the Tirion Atlas 2000, helps with page identification at a glance.  On a larger scale atlas, however, the section of a 

constellation so depicted doesn't help that much, and it could even be a problem if the observer didn't like the constellation patterns you picked.  I'd advise against it for general distribution,

even if you like it for yourself.

 

The magnitude 10 limit for stars is a good one.  Kudos.

 

As for the SAC database, be aware that all its star cluster positions (open and globular) have been corrected per the data in the book "Star Clusters" by Archinal & Hynes and represent the most current, corrected, catalog of star clusters available.  You state that you made corrections to DSO positions.  I hope no correction was applied to star clusters, since much other on-line data is filled with errors--especially for catalogs like the Ruprecht clusters, where many on-line lists had positional errors of up to a degree (!).  I have no comment about other coordinates, since I did not have a hand in correcting them, nor checking them against a modern, corrected, reference, like NED or SIMBAD.

 

I also do not know if the positions and identifications of NGC objects in your list have been corrected per the most recent Historically-corrected data from The NGC/IC.org group or Wolfgang Steinicke's more recent corrections.  In some cases, continuing an error (the NGC90/91 switch, for example) may be called for because of all the literature concerning these two objects, all of which used incorrect identifiers, i.e. if 100 years of scholarly studies are all in error, then perhaps the error has become the accepted norm, regardless of the historical roots of the error.  I hope you used at least the NGC/IC.org data or Steinicke's data for your NGC information rather than the older, and more error-ridden data often found on-line.

 

I like the idea of plotting constellation lines even at this scale because they help guiding the eyes to the brighter stars. Since the magnitude scale covers a very wide range, I feel like that without the lines the brightest stars don't pop enough, but I don't want to plot them larger, because then they will be too big.

 

I only corrected a very few positions (mostly for a few small bright nebulae, where they should have clearly been centred on a central star), most of the corrections were regarding sizes (or PA), and all corrections were based on the DSS images, and never on catalog data. (With dark and bright nebulae I have checked all entries manually while drawing the larger ones, so I corrected every small mistake I have noticed.)

 

I have not done the full coordinate cleanup and cross-checking with the data of Wolfgang Steinicke's NGC-IC project although I have downloaded the data and used it to clean up a few entries in the SAC. (I cleaned up all entries in the SAC where galaxies were very close to each other and it was not clear which component is which.) I have this on my to-do list. Of course here I again need to make a decision: include all NGC-IC objects (with a magnitude/size cutoff), or just the ones that are already in the SAC and take the data from the NGC-IC for these. (I am leaning towards the latter, or an at least magnitude limited sample.) Also, some objects will be in the SAC with not the NGC-IC primary name, so in any case this boils down to a catalog matching algorithm... As written already above in a previous reply, assembling a good deep sky catalog is a very complex, and unluckily very subjective process. Coordinate precision is objective, but object selection will never be.


Edited by papics, 22 June 2017 - 05:40 PM.

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#18 Starman1

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Posted 22 June 2017 - 05:52 PM

Sounds good.

Then there is finding a publisher, as the author, Christopher Watson, of the ill-fated SkyGx atlas found out.

His would have been 6 volumes, with stars to magnitude 12, ~3570 pages and ~$1000.

Yours will be much easier to get published.



#19 catalogman

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Posted 22 June 2017 - 07:35 PM

<snip>

 

The arrangement is in decreasing RA (you can actually see it in the filenames on this image: http://papics.eu/blo...2017_LSA-11.png), that is the only thing that makes sense, in my opinion. Otherwise you have to fold to the opposite direction than where you seemingly want to go (e.g., you would want to see the field that is on the right edge of a double page but then you would flip to the left?!?). I hope I am not the only one who thinks this is the only logical choice smile.gif

 

<snip>

 

 

You are visualizing the charts as pieces of a jigsaw puzzle.

 

Instead visualize the sky as a coordinate grid. To locate a particular RA and Dec,
turning forward in the book and seeing the RA numbers run backwards feels like
thumbing forward through a book and seeing the page numbers run backwards.

That's why to some observers (like me) increasing RA is the preferred arrangement.

 

Accommodating both arrangement preferences would introduce a unique feature to the

Leuven Star Atlas and make it stand out in the crowd.

 

                                                                                                       -- catalogman


Edited by catalogman, 22 June 2017 - 07:35 PM.


#20 catalogman

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Posted 22 June 2017 - 07:54 PM

 

<snip>

 

The ID mistakes in SAC mainly come from them not crossmatching separate catalogs when building their database, that seems quite clear to me.

 

<snip>

 

Perhaps you're referring to the numerous duplications that need to be cleaned up (NGC 20=NGC 6,

NGC 21=NGC 29, etc.)  Other errors are easy to spot (e.g., Ced 62 listed twice). Because the SAC

dates from 2010, I'll bet that all of the NGC/IC misidentifications from the 2003 edition of the PGC

have been picked up as well.

 

                                                                                                              -- catalogman



#21 catalogman

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Posted 22 June 2017 - 08:00 PM

 

<snip>

 

 Concerning the coordinate precision, on the current scale having a 0.5' precision for the DSO (since the coordinates are rounded to the closest arc minute, so the actual precision is minimum 0.5', and not 1') does not hurt (we are talking about +/-0.13 mm, when 16 mm = 1 degree), since even the smallest 10th magnitude star is much larger than that, and the symbol size for the smallest planetary nebulae is in the same ballpark. Yes, in a 4x zoom-in close up chart this would be already up to a 0.5 millimetre, and that is not something I want. So yes, I am not 100% satisfied with the DSO catalog, but it is complicated.

 

<snip>

 

Another reason for using accurate positions is to plot the relative PA of galaxies in pairs or groups.

In these cases, the SAC catalogue can seriously mislead the observer.

 

                                                                                                  -- catalogman



#22 catalogman

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Posted 22 June 2017 - 08:17 PM

<snip>

 

 Building a custom deep sky catalog is not a one day job, and I was playing around with this atlas in my free time. I need to see what are the best options here, and I am of course open to suggestions.

 

<snip>

 

But back to building a DSO catalog from scratch: just yesterday I received - from an amateur - a catalog of ~10200 asterisms. But I don't want to fill the atlas with asterisms (of course some of these are actual NGC OCs, that I either already have, or do not mind). Then how do you decide which ones to include? And then if someone of the millions of amateur astronomers has a favourite object and it is not included that will be a tragedy for them. I know. It would be to me. But you can not include all objects in a printed atlas, for that you have the computers and the various planetarium software. Here you need a good balance in objects of different types, and a sensible magnitude and size range. I can not include 50000 objects on a 344 page atlas. There is just not enough space.

 

<snip>

 

By thinking about how to limit the charts, you will be creating an atlas better than the "standard" atlases.

(Compare, for example: the optically invisible radio sources plotted on Uranometria 2000.0).

 

First experiment with a planetarium program in crowded fields to determine the brightest magnitude limit

(target mag) at which the field at your atlas scale begins to get cluttered.

 

To build a DSO catalogue from scratch, you would then have to:

 

#1) find catalogues of each object type

#2) within each catalogue:

  - galaxies: ID and mark objects brighter than the target magnitude.
  - bright nebulae: Use the brightness scale in some catalogues to ID and mark prominent BN's.
  - planetaries: Use the SAC magnitudes to ID and mark objects brighter than the target mag.
  - star clusters: Use the SAC mags to ID and mark OC's and GC's brighter than the target mag.
  - dark nebulae: Use a photographic star atlas to ID and mark prominent DrkN's.
  - LMC/SMC:  Use a photographic star atlas to ID and mark prominent objects.

 

#3) extract these marked objects to make catalogues for your atlas

 

It sounds complicated, but the final result will be more accurate than trying to fix someone else's

shoddy work.

 

Welcome to the unglamorous and thankless world of cataloguing!

 

                                                                                                                    -- catalogman



#23 catalogman

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Posted 22 June 2017 - 08:26 PM

<snip>

 

As for the SAC database, be aware that all its star cluster positions (open and globular) have been corrected per the data in the book "Star Clusters" by Archinal & Hynes and represent the most current, corrected, catalog of star clusters available.  You state that you made corrections to DSO positions.  I hope no correction was applied to star clusters, since much other on-line data is filled with errors--especially for catalogs like the Ruprecht clusters, where many on-line lists had positional errors of up to a degree (!).  I have no comment about other coordinates, since I did not have a hand in correcting them, nor checking them against a modern, corrected, reference, like NED or SIMBAD.

 

I also do not know if the positions and identifications of NGC objects in your list have been corrected per the most recent Historically-corrected data from The NGC/IC.org group or Wolfgang Steinicke's more recent corrections.  In some cases, continuing an error (the NGC90/91 switch, for example) may be called for because of all the literature concerning these two objects, all of which used incorrect identifiers, i.e. if 100 years of scholarly studies are all in error, then perhaps the error has become the accepted norm, regardless of the historical roots of the error.  I hope you used at least the NGC/IC.org data or Steinicke's data for your NGC information rather than the older, and more error-ridden data often found on-line.

 

 

Here's an on-line source of accurate star cluster positions (both OC and GC):

 

  http://cdsarc.u-stra...t?J/A A/558/A53

 

And I would add Corwin as a recommended source for NGC/IC identifications:

 

  http://www.haroldcorwin.net/ngcic/

 

Prof. Corwin did preliminary NGC/IC corrections for the first edition of Uranometria 2000.0 in 1987,

so he has had more experience than the other authors. His recent corrections for galaxies have

been incorporated into NED (he was a professor at CalTech, which hosts NED.)

 

                                                                                                     -- catalogman


Edited by catalogman, 22 June 2017 - 08:27 PM.


#24 The Ardent

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Posted 22 June 2017 - 08:32 PM

Catalogman, why don't you donate all your catalogs to this project? It will cement your legacy.

#25 papics

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Posted 23 June 2017 - 01:54 AM

 

<snip>

 

 Building a custom deep sky catalog is not a one day job, and I was playing around with this atlas in my free time. I need to see what are the best options here, and I am of course open to suggestions.

 

<snip>

 

But back to building a DSO catalog from scratch: just yesterday I received - from an amateur - a catalog of ~10200 asterisms. But I don't want to fill the atlas with asterisms (of course some of these are actual NGC OCs, that I either already have, or do not mind). Then how do you decide which ones to include? And then if someone of the millions of amateur astronomers has a favourite object and it is not included that will be a tragedy for them. I know. It would be to me. But you can not include all objects in a printed atlas, for that you have the computers and the various planetarium software. Here you need a good balance in objects of different types, and a sensible magnitude and size range. I can not include 50000 objects on a 344 page atlas. There is just not enough space.

 

<snip>

 

By thinking about how to limit the charts, you will be creating an atlas better than the "standard" atlases.

(Compare, for example: the optically invisible radio sources plotted on Uranometria 2000.0).

 

First experiment with a planetarium program in crowded fields to determine the brightest magnitude limit

(target mag) at which the field at your atlas scale begins to get cluttered.

 

To build a DSO catalogue from scratch, you would then have to:

 

#1) find catalogues of each object type

#2) within each catalogue:

  - galaxies: ID and mark objects brighter than the target magnitude.
  - bright nebulae: Use the brightness scale in some catalogues to ID and mark prominent BN's.
  - planetaries: Use the SAC magnitudes to ID and mark objects brighter than the target mag.
  - star clusters: Use the SAC mags to ID and mark OC's and GC's brighter than the target mag.
  - dark nebulae: Use a photographic star atlas to ID and mark prominent DrkN's.
  - LMC/SMC:  Use a photographic star atlas to ID and mark prominent objects.

 

#3) extract these marked objects to make catalogues for your atlas

 

It sounds complicated, but the final result will be more accurate than trying to fix someone else's

shoddy work.

 

Welcome to the unglamorous and thankless world of cataloguing!

 

                                                                                                                    -- catalogman

 

I agree with this, and I have partly already done it. For example for the dark/bright nebulae, and the LMC/SMC that is exactly what I did. But I guess you are also aware that all published catalogs have issues. For example for the dark nebulae I was looking at the original plates of Barnard, and some of his identifications are quite questionable (regions that are barely noticeable star-rich than the surroundings), and his outlines are very rough compared to what I have drawn based on better photographs of the sky. In this case I only took his numbers, but I made better outlines. There is no guarantee for any catalog that it will be without errors. Just to keep it in mind.

 

 

<snip>

 

As for the SAC database, be aware that all its star cluster positions (open and globular) have been corrected per the data in the book "Star Clusters" by Archinal & Hynes and represent the most current, corrected, catalog of star clusters available.  You state that you made corrections to DSO positions.  I hope no correction was applied to star clusters, since much other on-line data is filled with errors--especially for catalogs like the Ruprecht clusters, where many on-line lists had positional errors of up to a degree (!).  I have no comment about other coordinates, since I did not have a hand in correcting them, nor checking them against a modern, corrected, reference, like NED or SIMBAD.

 

I also do not know if the positions and identifications of NGC objects in your list have been corrected per the most recent Historically-corrected data from The NGC/IC.org group or Wolfgang Steinicke's more recent corrections.  In some cases, continuing an error (the NGC90/91 switch, for example) may be called for because of all the literature concerning these two objects, all of which used incorrect identifiers, i.e. if 100 years of scholarly studies are all in error, then perhaps the error has become the accepted norm, regardless of the historical roots of the error.  I hope you used at least the NGC/IC.org data or Steinicke's data for your NGC information rather than the older, and more error-ridden data often found on-line.

 

 

Here's an on-line source of accurate star cluster positions (both OC and GC):

 

  http://cdsarc.u-stra...t?J/A A/558/A53

 

And I would add Corwin as a recommended source for NGC/IC identifications:

 

  http://www.haroldcorwin.net/ngcic/

 

Prof. Corwin did preliminary NGC/IC corrections for the first edition of Uranometria 2000.0 in 1987,

so he has had more experience than the other authors. His recent corrections for galaxies have

been incorporated into NED (he was a professor at CalTech, which hosts NED.)

 

                                                                                                     -- catalogman

 

Thanks, I will have a look. I definitely like that Prof. Corwin has a Creative Commons Attribution-ShareAlike 3.0 Unported License, unlike Wolfgang... Unluckily it does not have magnitudes, diameters, etc, only positions...


Edited by papics, 23 June 2017 - 02:03 AM.



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