January 15, 2022

Palomar 2 & Pal 2 with the Hubble (Jan. 2022)

 

 

Palomar 2 is 34 kiloparsecs from the galactic center, one of the most far-flung globular clusters.  That makes it about 26 kpc (+-4) from us (about 85,000 light years).  That is why Pal 2 looks so small.

Another obstacle makes Pal 2 hard to study: the cluster sits behind a cloud of dust, and the cloud is not uniform but covers different parts of the cluster differently.  The cloud makes it hard to obtain reliable star magnitudes.  A 2020 study (Bonatto & Chies-Santos) says the cloud "leads to severe photometric scattering related to differential reddening." 2689. But the study heroically sorts through Hubble data to reach an informed estimate of the cluster's distance.  (The study also gives the best current color-magnitude diagram for Pal 2.)

The same study at 2693 posits that Pal 2 contains 140,000 stars.  Too bad it's so far away. It would be stunning to see it close up.

This image is 21x900" with the Atik 460EXC through the 203mm Synta ONTC Newtonian at f/4.9 using an Astronomik CLS filter.

But---there is Hubble data, as the study says, so I went to Hubble's Legacy Archives and fetched it.  It was taken in deep red and broadband, so the colors below are just a good guess.  Once I had the Hubble data, I figured, hey, why not add it to my image?  So here first is my image with the Hubble data added in---my collaboration with the Hubble on Pal 2.  You can see the stars are a lot brighter.  I can reach mag 20 from my backyard in one night, but the Hubble data goes down to mag 25 or so.  Adding this to my data makes the cluster a lot brighter, though shrinking the Hubble scale to fit my images more or less means that that data shows only the brighter stars and clumps, so the Hubble data does not really add stars to my data as much as it makes everything brighter.

Here is my Hubble collaboration on Pal 2:

And here is my version of the Hubble data from the Hubble Legacy Archives:



November 27, 2021

The Horsehead Nebula (Fall 2021)


OK, it's not like I've never taken an image of the Horsehead Nebula, but I haven't with this scope and camera.  This one took four nights and includes only frames east of the meridian (till the tree blocks the view). I was happy to capture signs of four or five Herbig-Haro objects identified in this paper.

This is 56x300" with the 203mm Synta ONTC Newtonian at f/4.95 with the Atikc 460EXC and an Astronomik CLS filter.

November 23, 2021

Jupiter: Double Shadow Transit (Nov. 23, 2021 or UT Nov. 24, 2021)

 

Sometimes the sun and one of Jupiter's moons line up so that the moon's shadow crosses Jupiter's face. The shadow looks like a black spot on the planet. Tonight two shadows crossed Jupiter together---a photo op! The right shadow is Ganymede's; the left is Callisto's. In between them is the Great Red Spot. To the right and below the planet, you can spot the moons themselves, Ganymede nearer Jupiter and Callisto further away.
 
This image was shot through my wonderful 6-inch f/8 Newtonian telescope with a QHY5iii485c. 5,268 subframes were taken and 60% of them stacked and sharpened to make this image. The scope is Dobson-mounted, so I dragged the scope twice to make Jupiter transit across the camera chip three times.  I'd have used the CFF290 on the NJP, but I can only see Jupiter from the north end of the yard, where I can't see the north star to set up my mount (OK, yeah, without drift-aligning, but we all have our limits).

Lunar Eclipse (Nov. 19, 2021)

Canon T3i through the SkyWatcher ED80 with 0.85x reducer-flattener: this was about 3:11 a.m. CST on Nov. 19.  The eclipse was never full, and the camera couldn't handle the dynamic range.  Through the eyepiece, the moon was stunning!

November 20, 2021

NGC 206, an OB association in the Andromeda Galaxy (Fall 2021)


What looks like a cluster of blue stars in this image (and was called a cluster by Edwin Hubble) is actually a large association of young type-O and -B stars (hot, large, and bright) that shines 2.5 million light years away in the Andromeda Galaxy.

This image is 44x1200" with the Atik 460EXC, 203mm Synta ONTC Newtonian at f/4.95, and an Astronomik CLS filter.

November 17, 2021

M103 (Nov. 2021)

This simple but striking cluster in Cassiopeia was captured with 29x300" using an Atik 460EXC through the 203mm Synta-ONTC Newtonian at f/4.95 and an Astronomik CLS filter.  Seeing was actually pretty bad the night of capture.

October 16, 2021

M29 (Oct. 2021)


I've always been interested in M29.  It's a simple, beautiful little cluster in a constellation (Cygnus) cluttered with interesting things.
 
I didn't realize that controversy existed over which stars belonged to the cluster.  It turns out that some of the bright stars above---in what look like a cluster---do not!  The problem is that the stars are too far away to measure their proper motion across the sky.  Also, dust extinguishes light along our line of sight by several magnitudes.  Without knowing the stars' intrinsic brightness, their distance is harder to infer.
 
But a study published in 2014 helps resolve these concerns.  The study carefully compares the spectra of the stars with their brightness and the brightness of stars in the local vicinity to better estimate their distance and the effect of dust (another, larger 2015  study by many of the same authors examined extinction in the area of the cluster). The 2014 study estimates that at least 15 stars lie together at 2.2 kpc, about 7,100 light years.
  
The stars numbered in this image (linked here from the study) are probable cluster members:
 

 
Some of the brightest stars in the cluster fail the test.  The white star in the top row (HD194378) and another bright star in the bottom row (HD 229238) are probably not cluster members. The study reminds us that space is a busy place full of unexpected surprises; sometimes line of sight alignment tricks us into thinking items come as a unit.
 
My image is 22x180" with the Atik460EXC through the 203mm Synta ONTC Newtonian at f/4.95 and an Astronomik CLS filter.