Thoughts on creating a target catalog for astrophotographers

Thoughts on creating a target catalog for astrophotographers

Tl;dr : I'm thinking of making a catalog of "good" astrophotography targets. Would you like to be part of this ? What would you want from such a catalog ?

This has been on my mind for a while and it stems mainly from two things: the difficulty of choosing targets after one gets past the most popular ones, and the overwhelming number of images of those few popular targets in the community (looking at you here, M31 and M42). There are a lot of astronomical catalogs, compiled by various criteria, but none of them are particularly well suited (except to provide an ID) to amateur astrophotography.

The Messier catalog contains most of the bright objects but it gets increasingly repetitive with globular clusters for example and completely excludes some types

The NGC/IC is huge and awash with tiny galaxies, going through the 10,000+ objects it contains is completely impractical and many targets are out of reach for more common AP setups.

The Sharpless catalog is only of emission nebulae, a treasure trove at that, but except for a few more well known objects it's rarely used

Catalogs like ARP and Abell are full of challenging and rarely done targets, some well out of reach for almost all astrophotographers, going through them one by one to find a good target is not an easy task

Barnard/LDN catalogs have quite a few nice and mostly accessible targets but they're very rarely done. It's somewhat understandable since in visual astronomy dark nebulae are of little interest and most people come from that, but in AP they can be beautiful targets.

Many more catalogs exist, some containing a few great, accessible and sometimes off-beat targets but since they're so rarely used/mentioned few people explore them. Some great astrophotography opportunities are not to be found in any catalog at all since they are ensembles or interesting groups of different types of objects, there are a few galaxy clusters that get imaged often as well as nebulae groups, but i'm sure there are many more.

Another pet-peeve i have with the currently most used catalogs is the lack of structure, M17 is a nebula, M18 is an open cluster, M19 a globular cluster and M20 a nebula again. When you just need to rule out objects while you're hunting comets that's perfectly fine, but there's a missed opportunity here to have IDs mean something.

What I would like to exist is a catalog made specifically for amateur astrophotographers that gives a diverse, well structured selection of visually interesting targets. No need for 50 globular clusters, no need for hundreds of arc-minute sized galaxies and no need to make some targets (dark nebulae, very large emission nebulae, even interesting asterisms) second class citizens, we could all use a bit more diversity.

As far as I know (and searched) there isn't any catalog that fits this very well and, to be fair, our criteria and constraints are pretty distinct from both visual and research astronomy, so... why not make one ?

As i said, this has been on my mind for a while so I'll share some thoughts :

Targets should be gathered from all types of objects - including "scenes" which would be ensembles of objects.

Targets should be diverse and fairly non-repetitive within the catalog (yes, there would be few globular clusters)

Targets should have an aesthetic/interesting quality

Targets should be classified with the practical needs of the astrophotographer in mind - type, size, relative difficulty, seasonality, declination, etc and this should be reflected in the identifier of the object as much as practically possible

The following is as an example : - Type should be the obvious thing (galaxy, emission nebula, planetary nebula) - identified by a descriptive letter (G for galaxy) - Size should go from ultra-widefield, like 10 degrees field radius or more to a few arcminutes (for a single object target) - identified by numbered classes (1 - very large to 9 - very small) - Relative difficulty is tricky, this should mainly take into account brightness, I think a three tier system would suffice - identified by a lower case letter, a (easy), b (challenging), c (difficult) - Seasonality would identify specifically when an object is highest in the sky during the year at a convenient hour, it would be a more intelligible way to classify by RA. Should be divided into a few sections, not necessarily by the four seasons as that might be to coarse, but could be early and late for each season (so 8 divisions). Can be identified letters in alphabetical order. If you start with A for early spring you end up with H for late winter, as time goes by you just advance in the alphabet so you know which targets are ready for prime time. - Declination should be divided into sections so you know easily if the target is viable from your location, 20 degree increments work well. Identifiers could go from 1 (90° to 70°) to 9 (-70° to -90°), so if you live in the northern hemisphere you know that objects in section 1 are always accessible, objects in class 5 (-10 to +10) are seasonal and going much further after that you can't reach them at all.

Using the first three (type, size, difficulty) to form the identifier we can already distinguish some good info just from the name : G3a could mean a large and accesible galaxy, E6b a smallish and challenging emission nebula, P8c a difficult and small planetary nebula. Add to these a unique number and that could be the object name (G3a-1, G6b-2, E5c-24, etc..)

The last two (seasonality, declination) could be added to the object identifier, but i'm thinking it might be already too crowded, G3a-A4-21 or P8c-D2-85 sure is descriptive alright but probably going too far and they're better kept in the catalog document. I imagine with discussion we can come up with a much better system.

Oh, the catalog would also need a name, AstroPhotography Catalog (APC) seems simple and direct but no need to nail it down for now.

This is something I'd like to work on but I don't think the best results can be achieved with any singular person or closed group creating this, so are any of you interested in putting something like this together ? It would not be a particularly fast process nor would it have a clear end point (can be continually expanded), criteria and structure would need to be brainstormed, established and after that candidate targets would need to be submitted and analyzed. I see this containing over 200 hundred targets before we could say that a first edition is done.

This project would obviously be kind of "open-source", no owner, no way to profit from it, but I think the process of making it would be very rewarding. I've preemptively made a subreddit (/r/apcatalog) for discussion, it is locked for now, but we can start it up if there are people interested in joining in.

To everyone else, what would you expect/want from a ap-centric catalog ?

Submitted September 27, 2016 at 03:48PM by astrophnoob from reddit via /r/astrophotography