How to Sew the Halley's Comet Quilt Block: an Easy 10" Block that Creates a Stunning Lattice Design

I decided to include cutting instructions for a 15" finished block too. I wrote the tutorial for the 10" size so you will need to substitute the larger pieces if you make a 15" block. 

• Light (White): 4 - 4" squares, 1 - 3.5" square, and 4 - 3.5" x 6.5" rectangles
• Medium (Aqua): 4 - 4" squares, and 4 - 3.5" squares
• Dark (Blue): 4 - 4" squares, and 8 - 3.5" squares

Make four Snowballed Rectangle units using the Light 2.5" x 4.5" rectangles, and the Dark 2.5" squares. This unit goes together just like half of a Snowball block except that you use a rectangle for the base. You can find my tutorial for making a Snowball block at https://fabric406.com/blogs/fabric406-blog/how-to-sew-a-basic-snowball-block

Here are the first steps, going from top to bottom: 

• Mark a diagonal line from corner to corner on the back of the 2.5" squares and sew a 2.5" square to one corner of the Light rectangle along the marked line. Note the orientation of the marked line.
• Match the corners of the 2.5" square and press.
• Open up the 2.5" square and trim the seam allowance.
• Refold.
• Repeat for a total of four units.

Step 6:

Repeat Step 5 on the opposite corner of the Light rectangle for a total of four Snowballed Rectangle units like the ones shown below.

Center Unit:

Step 7:

Lay out the four Step 4 Half Square Triangle units, the four Medium 2.5" squares, and the Light 2.5" square in a typical Nine Patch configuration as shown in the picture below.

 

Step 8:

Sew the units into three rows.

Step 9:

Press the seam allowances toward the Medium squares as shown in the picture below.

Step 10:

Sew the three rows together - this makes a cute block all on its own!

Step 11:

Press the seam allowances toward the center of the unit as shown below.

Sashing Unit:

Step 12:

Lay out and sew together a Step 2 Half Square Triangle unit and a Step 6 Snowballed Rectangle unit. Press the seam allowance toward the Half Square Triangle unit as shown below. Repeat for a total of four units.

Putting It All Together:

Step 13:

Lay out the Center Unit, the Step 12 Sashing units, and the Step 3 Half Square Triangle units as shown in the picture below.

Step 14:

Sew the units into three rows as shown.

Step 15:

Press the seam allowances toward the Step 12 Sashing units as shown below.

Step 16:

Sew the rows together to complete the block and...

Step 17:

Press the seam allowances away from the center of the block.

Layout Ideas:

This is the basic 4 x 4 layout using colors similar to the tutorial. I think this is also the prettiest layout because of the lattice design that appears.

This is the same layout as above but with a 2" pieced sashing and Light cornerstones added.

Here's an alternating layout. Every other block is has a snowballed square in the center instead of a nine patch like the main block.

This alternating example also uses a modified main block for the alternating block. In this case, I kept the nine patch center unit but eliminated the rest of the block.

This is an on-point layout with narrow (1") sashing and cornerstones in a complementary color and background (Light) fabric used for the setting triangles.

And this is another on-point layout - this time with a simple chain block used for an alternating block that extends into the setting triangles.

Conclusion:

I enjoyed sewing this block together. While some of the seam intersections got a bit thick, the block turned out nice. I especially like how the Halley's Comet creates the lattice design in a quilt!