Readers of this blog will soon notice how many faint and very faint galaxies must be sought out, if all of the NGC objects are to be observed. While it is theoretically possible to observe the entire list (at least the northern latitude ones, which were all discovered visually) with a 12" scope in good skies, it is not a task for the meek and mild observer. William Herschel discovered most of them with his massive 18" reflector. However, the coating on his mirror was not nearly as reflective as today's instruments. One wonders how delighted he would have been with a light weight, modern 12" scope instead!
The first step in locating faint galaxies is to try this limiting magnitude test. It only takes a few seconds. At 200x using a 12" mirror in normal condition, my limiting magnitude is 16.1. Finding faint galaxies is quite different from seeing faint stars, but this will give you some idea of your observing limits.
The second step is to have a very good star atlas. Never mind using your "go-to" or "push-to" technology. That works for getting you to the general area, but it will not show you a small, very faint object. It does help if a brighter object is close by, but the only certain way to find some of the faintest objects in the NGC list is to star hop. I am going to use five galaxies in Pegasus as my examples, and detail how they were located.
The second step is to have a very good star atlas. Never mind using your "go-to" or "push-to" technology. That works for getting you to the general area, but it will not show you a small, very faint object. It does help if a brighter object is close by, but the only certain way to find some of the faintest objects in the NGC list is to star hop. I am going to use five galaxies in Pegasus as my examples, and detail how they were located.
The five galaxies are 7146, 7147, 7148, 7149, and 7156. All are located on Chart 103 in the All-Sky Edition of Uranometria 2000, just north of the border with Aquarius. The first thing to do is to get familiar with the chart, as well as the specifics of each galaxy. If you are star hopping, the nearest bright star is Alpha Aquari (not shown on map detail). The brightest star on my map detail below is 11 Pegasus. All five galaxies fit within a one degree field, but don't expect to see them at low power.
Uranometria 2000, Chart 103, detail
Notice how few bright stars are near the galaxies. All are in the 8.5 mag. to 9.5 mag. range. A small pattern of four stars south and following 7156 can be noted, and if this tiny pattern can be located, then the game is on. Of course in a 12" scope at low power (60x), those stars look pretty bright. In addition, an entire array of fainter ones are visible, too. To confirm your location as the correct one, try hopping to star 11 from here and back (my push to computer put me right in the field, but I still wished to confirm it). If you have already come from star 11, then you can skip this next step.
There are a few ways to get to star 11. I hopped south to the 7 mag. star on the border with Aquarius. Moving west (right on the map) a faint triangle of stars is reached about halfway to 11, with two stars in Pegasus and one in Aquarius. The two stars forming the short base of the triangle point to a faint star just north following star 11. To confirm you are at star 11, go a bit further west and look for the pattern of stars just west again. Voila!
There are a few ways to get to star 11. I hopped south to the 7 mag. star on the border with Aquarius. Moving west (right on the map) a faint triangle of stars is reached about halfway to 11, with two stars in Pegasus and one in Aquarius. The two stars forming the short base of the triangle point to a faint star just north following star 11. To confirm you are at star 11, go a bit further west and look for the pattern of stars just west again. Voila!
Now, return to the area of 7156. It is time to find our first galaxy. eg 7156 ( 1'.6 x 1'.4: V. 12.5; SB 13.2) is the brightest and the largest of the bunch, and easily located at 100x. If you can't find this one, you will not likely find the others. To see galaxies well the sky must be transparent, meaning little humidity is in the air. Good seeing also helps, but is not as critical as transparency. Good seeing is often at hand when wind is light or non-existent. With a combined mag. of 12.85, a good 8" scope will show this one with a bit of work. In the 12" it is a nice galaxy, large but not very bright at 100x. 150x shows it much clearer, with perhaps a bit of ovalness to the shape. Even better views were had at 187x and 200x, where a large, brighter middle was noted surrounded by an area of fainter haze, unequally bright. It is not a showpiece in a 12" scope, but it is the best of the bunch.
If you are ready to continue, we'll move to a fainter galaxy. If not, keep trying for the first one, making certain of your position. eg 7149 (1'.3 x 0'.9: V. 13.2; SB 13.3) is a bit tricky to find at first. However, once located its nearby star field is a giveaway as to its location. With a combined magnitude of 13.25, this is still well within range of a good 12" with an experienced observer behind it. The galaxy lies midway between two brighter stars shown on the map, and one of them is a distinctive double. Just north of the numbers "46" in 7146 on the map is STF 2830: mag. 8.9 and 11.9 at 27". Try returning to star 11 and reaching it from there. Once this star is located, it is the key to finding the four remaining galaxies. Move north following between it and the brighter star north following 7148. I do this kind of work at 60x, then when I know I am in the area, I go up to 100x. If I don't find anything there, then I go up to 125x. This is where I finally spotted 7149. It wasn't easy at first. It is in a curving line with a faint double star, being third in the procession. It was glimpsed as an oval patch at 150x, 187x, and 200x. Most importantly, a tiny group of four or 5 faint stars lay not far away, south following. They make identifying the galaxy on future visits much easier.
We will leave 7148, companion to 7149, for later. It poses a whole new series of problems that must be dealt with. Instead, return to STF 2830. To locate eg 7147 (1'.1 x 0'.9: V. 13.5; SB 13.3) move slightly following the double star, and look just a few seconds south. I noticed a "V" shaped group of six stars pointing south, three on each side with the south end narrower. 7147 lies near the center of this configuration. It took me a long time to finally notice it, though once found it becomes obvious (of course!). It was observed at 150x, 187x, 200x and 250x, though it became very faint at the latter. With an average mag. of 13.4, this one is very similar to 7149, but perhaps a bit more faded.
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A crude but fairly accurate sketch of eg 7146 (left) and 7147 (right). North is at the top. Note the arrowhead star pattern, which is just south following STF 2830.
7147 is paired with eg 7146 (0'.9 x 0'.6: V. 14.3; SB 13.4), being notably fainter and smaller. As a result, the search for it took some time as well. It takes patience and perseverance to find some of these faint galaxies, but once found they are more easily seen. If you can see 7147 at 150x, then you are probably looking at 7146! Note that arrowhead of stars, and find the row that is preceding the others (watch and see which stars go out of the field first--those are the ones you want). Center them in your field, and look between and following the middle two stars. It is noticeably elongated, but very illusive and ghostly. I saw it best with averted vision at 150x, 187x and 200x. With a combined mag. of only 13.85, it is (on paper) the faintest of them all. It's larger size makes it easier to find than upcoming 7148, but not by much. If you can glimpse 7146, you are doing really well!
If you have been fortunate in your hunt, then be prepared for the final and bigger challenge. If you have not found these first four galaxies yet, then keep trying off and on when conditions allow. eg 7148 (0'.5 x 0'.4: V. 14.8; SB 12.4) is a beast! Don't be fooled by that surface brightness figure! With a combined mag. of 13.6, it is the 2nd faintest and by far the smallest of the group. It is so small that nothing short of a pinpoint location chart will help to find it. Don't rely on luck; it doesn't work well with these smaller galaxies. I tried for awhile the first night and gave up. Here is what I do when that happens.
I use this website to help me pinpoint faint galaxies and planetary nebulae. Where it says "Go To Object" at the top, type in 7149 (they do not list 7148!). A teeny weeny galaxy will pop up amidst a terrifying star field. You should have already seen this galaxy. Try and find that distinct little star pattern just following it (left side). Now drag the map south from 7149 and you will soon come across 7146 and 47, old friends by now. Now drag the map north from 7148 and you will see a very small, yellowish galaxy, with some elongation. It is attached to a very faint star (or likely it is another galaxy). That is eg 7148. Now back out one click, and you will see the target galaxy in relation to 7149, and a bright star north following (shown on Uranometria). Sketch those three objects in rough (the bright star and the two galaxies, one of which is your target), then proceed to add two more stars to your sketch. Note that the target galaxy makes a rough triangle with a blue star preceding it and an orange one north following. With these five objects sketched in, you are ready to find and conquer the fifth and final galaxy in our first challenge round! Those final two stars you sketched in are about mag. 13.5 to 14.5.
On the next perfect night, return to 7149 (I went back and found them all again--for several nights afterward I could picture all five galaxies perfectly in my head before falling asleep, along with the helpful stars!). Using your location sketch in the field, (and Uranometria) locate the bright star, then the two faint stars. You are now ready to add some power and use averted vision. Good luck! I saw it at 187x with averted vision. It was tiny and round, and of course faint. The star attached to it was too faint for me to see, but the galaxy will pop out at you from time to time, looking like a tiny, very faint planetary nebula. Be patient! While there isn't much to see with these smaller, dim galaxies, training your eye to see them is an important step to finding all of the NGC objects.
Lastly, remember to keep things in perspective, too. You are looking at another GALAXY! It isn't just a faint little round fuzzy thing. I've noticed that I now have much more appreciation for semi-faint galaxies, such as the other four in this list besides 7148. And I have now located dozens of these tiny ones. Following a very challenging session like this one, try to imagine how impressive those spring Messier galaxies will look now!
Lastly, remember to keep things in perspective, too. You are looking at another GALAXY! It isn't just a faint little round fuzzy thing. I've noticed that I now have much more appreciation for semi-faint galaxies, such as the other four in this list besides 7148. And I have now located dozens of these tiny ones. Following a very challenging session like this one, try to imagine how impressive those spring Messier galaxies will look now!
Mapman Mike
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