Saturday, April 29, 2023

Imaging a Favorite Visual Target (M44 - Beehive Cluster)

Working on the New Camera


Sunday night April 9th (2023) was a clear night. Clear nights have been far and few between this year. Took the opportunity to work on optimizing the setup for my camera. In January of this year, I purchased my first Dedicated Astronomy Camera, the ZWO ASI2600MC Pro. Quite the step up from my DSLR. In the few opportunities that I've had to use the camera, confirmed that I have sensor tilt (the sensor is not square to the optical path). Spent the first night working on that, with some success (took the tilt from Severe to mild). The skies were amazing and I stopped making adjustments. Will need to make a few more subtle tweaks next clear night, didn't want to waste any more imaging time. Since it was a work night, was looking for a target that didn't require many hours of integration. Aha! M44, The Beehive Cluster. This checked a few boxes like: didn't require many hours of exposure, would be a good target to evaluate impact of adjustment as it's all stars, was well placed in the sky, and I love looking at this cluster through binoculars. Star Clusters aren't necessarily the "sexiest" choice of targets compared to Nebulae and Galaxies, but I have a soft spot for them, so this won't be the last cluster I image.

Messier 44 (M44) also known as The Beehive


What is it?

Messier 44, also known as The Beehive or Praesepe, is an open star cluster located in the constellation of Cancer. Unlike many of the Nebulae and Galaxies we image, open star clusters are great visual targets. M44 is even Naked Eye visible from dark skies, appearing as fuzzy star. Optical Aid, preferably binoculars or a wide field refractor (in my opinion) will reveal the individual stars. binoculars will reveal about 75 stars with larger telescopes revealing more. The cluster contains about 100 members, most of which are M dwarfs. The mass of the cluster is about 500 times the mass of our Sun. The best time to view this cluster for northern latitude observers is from February through May.

How big is it?

M44 is about 95' (arcminutes) in diameter. The cluster is 16 light-years across.

How old is it?

The cluster is about 600 -700 million years old.

How far is it?

577 light-years or 177 parsecs from Earth.

How to find it?

When we observe many of the objects that we typically image with our visual observing equipment, we typically don't see the same color and details. This does not make visual observing less valid or impactful, just a different experience. However, star clusters are an (generally speaking) exception. They will also punch throw light pollution, of course the view is always better in dark skies. Star clusters like M44 are often excellent objects to observe in binoculars and telescopes with a wider field of view due to their angular size in the night sky. for perspective, M44 is 95' across and the Full moon is only about 30'. These factors combine to make star clusters an excellent choice for visual observation for a wide range of astronomers and their respective equipment. Personally, this is one of my favorite springtime targets to visually observe.

Finding M44 is pretty easy even though the constellation of Gemini is a very dim constellation. Refer to the finder chart below and follow these steps:

  1. Find the bright star Pollux in the constellation of Gemini, in the West-Southwest sky this time of year (late April/early May).
  2. Find the bright Regulus in the constellation of Leo. Look for the Sickle asterism or the backwards question mark. Regulus will be the bright star at the bottom. At the time of this blog post (late April/early May) Regulus is high in the sky almost due South, just past the Meridian, towards the West, at dark. The Meridian is an imaginary line in the sky from North to South, dividing the celestial sphere into East and West.
  3. Point your binoculars or your telescope's finder almost halfway between both stars to find the cluster of stars.

Finder Chart for M44

Image Details:

Capture Date: 04/09/2023
Location: Eden, NY
Telescope: Explore Scientific ED80 Essential Series Air-Spaced Triplet Refractor
Camera: ZWO ASI2600MC Pro
Mount: Sky-Watcher USA EQ6-R Pro
Exposure: 178 exposures at 30 sec each for a total exposure of 1.48 hours / Gain 100 / Offset 50 / -10°C 
Software: NINA, SharpCap Pro, PHD2, and PixInsight



Sunday, April 2, 2023

A Journey Down a Rabbit Hole with Galaxies in my Image of M81 & M2

What led me down the Rabbit Hole?

Ok, I went down a rabbit hole on trying to identify and understand the distances to background galaxies in a recent image of the M81 & M82. I have a strong interest in finding a background galaxy that is about 380 million light years distant from Earth. Why? Well, one of the places I'm active in doing Astronomy outreach is Penn Dixie Fossil Park & Nature Reserve. The fossils found at there are about 380 million years ago. Scott Roberts from Explore Scientific calls astronomers "Hunters of Fossil Light". I find this sentiment particularly inspiring, especially due to my ties with Penn Dixie. This is what's behind my goal of finding a galaxy 380 million years away. I want to find fossil light that matches the fossils at Penn Dixie.

I recently acquired a new camera for astrophotography, a ZWO ASI2600MC Pro dedicated astronomy camera. In late February there was a rare and brief window of clear skies. Perfect for experimenting with the new camera on my imaging rig. I captured just under two hours worth of exposures on M81 & M82. The resulting image came out ok. Definitely could benefit from more time on this target. 

An astrophoto of M81 & M82 by Ernie Jacobs
Processed image of M81 & M82 from 2/25/2023

Finder chart for M81 & M82 to show their position in the night sky
Where to find M81 & M82 in the night sky.

Annotating the image in PixInsight

After processing the image in PixInsight, I plate solved the image. What is plate solving? Specialized software compares the stars in the image to a database and precisely locates the image in the night sky. This enables identification of objects contained within the field of view of the image. I used PixInsight's image annotation script to identify and display objects captured in the now solved image. I was blown away by the result.

annotated image showing many galaxies contained within the field of view of the image of M81 & M82
Annotated image of M81 & M82. Look at all of the galaxies!

Identifying the objects in the image

If you Zoom in, there is something there for almost every object identified. That something can be a smudge, a faint spot or a tiny streak. Experimenting with the annotation script, I discovered the result could output to a text file. This text file was imported into Excel and I began the process of trying to identify the light travel time for the objects identified in the image. Using Jason Guenzel's article "How To Identify Objects in Your Astrophotos" from the May 2022 issue of Astronomy Magazine as a guide, The Sinbad Astronomical Database and The NASA/IPAC Extragalactic Database (NED) were used to identify the light travel time to most of the objects identified in the annotated image. 


Object List from the annotated image of M81 & M82

In the table above, the designation of "M' indicates the object is the Messier catalog, 'NGC" New General Catalog, "PGC" Principle Galaxies Catalog, & "ARP" Arp's Atlas of Peculiar Galaxies. The distances from Earth to the main objects in the list are given in Megaparsecs (Mpc) and Million light-years (Mly), as they were easily found in Wikipedia. For the remainder of the objects, the light travel time is given in Gigayears (Gyr) form SINBAD and NED. One Gigayear is one billion light years. For example, in the table above, the light travel time for the galaxy PGC28018 is 0.215 Gyr or 215 million light-years and for PGC28056 that's 1.506 Gyr or 1.5 billion light-years. 

Mind Blown!

In this hobby it's "normal" to throw around unfathomably large numbers. I don't think our limited human experience allows us to fully appreciate the scale of these numbers. Let's look at the difference between one million and one billion as an example. One million seconds is about 10 days and one billion seconds is over 30 years! I don't know about you, but this blows my mind and is a large part of what fascinates me about this hobby.


I hope you enjoyed my trip down this rabbit hole. 


Clear Skies!
Ernie

Image Details:

Capture Date: 02/25/2023
Location: Eden, NY
Telescope: Explore Scientific ED80 Essential Series Air-Spaced Triplet Refractor
Camera: ZWO ASI2600MC Pro
Mount: Sky-Watcher USA EQ6-R Pro
Exposure: 55 exposures at 120 sec / Gain 100 / Offset 50 / -20°C each for a total exposure of 1.83 hours
Software: NINA, SharpCap Pro, PHD2, and PixInsight


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