Easy Doubles Near The Messiers

I'm starting a new category of double star lists.  These will be easy doubles within a 4 degree radius of the various Messier objects.  Working the Messier list is popular with amateur astronomers, and here's a way to toss in a few double stars to boot.  Being only 4 degrees away keeps the double within close proximity of the Messier and also no further away than the diameter of the outer circle of a Telrad finder.  I'm hoping this will make it easier on those folks in light polluted skies and those that don't have goto mounts.  Again, these should be splittable in a minimum 4" scope.  The smallest separation is 5 arc seconds.  There should not be too many pairs with stars dimmer than mag 10, although there will be a few dimmer than that to test your optics.  Mag 12.5 will be about the limit.  Note: since many of the Messiers are close to each other, there will be some occasional overlap and redundancy of doubles across the lists.  The lists are here.

Sirius' Companion Still Alludes Me...Seriously

Sirius is high in the southwest by dark at my location.  Last night I had fairly clear skies and decided to try out a new Celestron 6” SCT.  In addition to the OTA, I’ve also added a GSO low-profile Crayford focuser for SCTs, so I tested that as well.

As it turns out, the seeing was average, but transparency was horrible due to haziness.  The NELM must have been ~2 because I could barely make out Polaris during the alignment process.  In fact, I wasn’t even certain that I had aligned on Polaris until the mount slewed to the first alignment star, which happened to be Sirius, and found it okay.

Sirius did not appear as bright this evening as I’ve known it to be, so that confirmed my suspicions about the transparency.  I started with a 24 Pan (62x, 65.3') and through the C6, it was nice and stable, with no “boiling” effect.  I used the main focus knob and got what I thought to be very good focus via the CCW method.  Next, I tried the Crayford fine focus knob and was able to get that little extra tweak to a sharp pinpoint.  I barely had to turn the knob to achieve this, but it was noticeable.  I was able to see a hint of the first diffraction ring.  Next, I swapped out the 24 Pan with an Astro-Tech Paradigm ED 12mm (125x, 28.8').  Again, I used the main knob for course focus, went CCW to fine focus, but then used the Crayford and got that extra little tweak.  This extra tweak provides more defined diffraction rings, too.  With the Paradigm, I could make out two distinct diffraction rings, which were surprisingly steady.  Alas, I was unable to resolve The Pup, though, despite a long observation through the 12mm.  I knew approximately where it should be and thought I saw it once with averted vision, but could not repeat that.

I spent about an hour, off and on, trying to split Sirius and The Pup.  I didn’t actually expect to do so with the C6, especially when I realized how bad the transparency was.  Still, it was a good opportunity to get out and test the C6 and the Crayford focuser for SCTs.  The optics are perfectly collimated, with excellent patterns in and out of focus, so nothing bumped in shipping.  Unfortunately, the bad seeing conditions prevented me from confirming the scope's magnitude limit.  I was unable to see any star dimmer than about mag 6 or 7, which may have also lent to my inability to see The Pup (mag 8.5).  The Crayford provided what I hoped it would, better pinpoint focus, but I feel it’s a bit pricy for the results.  As little as I had to turn the fine focus knob, I’m satisfied that my normal SCT focus procedure is working well.  What little extra I get from the Crayford is probably more suited to AP applications rather than visual.

Orbiting Binary Indication

You may start to notice a few of the Primary IDs are listed in bold and red.  I'm now using this to indicate a confirmed binary that has a measured secondary orbit.  An example of this can be found in the challenging doubles in Leo list.  I'll eventually go back through some of the older lists and also make this notation where I didn't previously.  At some point, I may even create special lists of only true orbiting visual binaries.  It seems like there might be some interest in this, especially for amateurs who want to attempt to make astrometric measurements themselves.

Challenging Doubles - By Constellation

I've been trying different filters with Sky Tools and finally decided upon a good set of criteria for challenging doubles.  I think many of these will still be splittable through a small refractor, but probably a 6", or greater, aperture would be best for the tighter ones.
The lists are here.

Filter Criteria:

Separation is ≥ 1" and ≤ 3"

Minimum brightness for the primary is mag 10

Visibility is filtered for urban light pollution levels

Easy Doubles - By Constellation

Another set of lists I've been working on contain easy doubles within the various constellation boundaries.  These lists can grow fairly large since even the smallest constellation can cover a lot of sky.  You can download them here.

Easy Doubles Near Bright Stars

Currently, I'm working on lists of doubles that are within 4 degrees of a specific bright star.  The bright stars I choose are typically mag 3, or brighter, and typically used as an alignment star for most goto systems.  The inspiration for these types of lists is, again, my location in a light polluted area.  My Naked Eye Limiting Magnitude (NELM) is ~3 from my backyard, so I know these lists will contain doubles that I can split.  Additional criteria includes scope aperture - most of the doubles in these lists should be splittable with a minimum 4" scope.  You can download them here.

Let's Get Started

I started this blog as a way to share lists of double stars that I compile for viewing.  Because my backyard location is in a heavily light polluted area, most of the lists contain easy, or fairly obvious doubles that are not too difficult to split.  However, I occasionally view from a dark site, so I like to challenge myself with a list of difficult splits.  Thus, I will also post lists of very challenging doubles from time to time.