As we say goodbye to summer and get ready to welcome in autumn, I thought I would offer not one, but two challenges this month to bridge the seasonal change. Both appear right next to each other in our sky but are millions of light years apart. And both require all the aperture you can throw at them to be seen.

One of the classic challenges facing deep-sky observers at this time of year is spotting the Ring Nebula’s central star, the progenitor sun that started it all some 6,000 to 8,000 years ago. Seeing the Ring's central star is one of those tests that every visual amateur needs to take at one point or another.

Looking through observing handbooks, reading on-line deep-sky logs, speaking with friends and colleagues who I consider to be seasoned veterans, and my own personal experience all seem to show that spotting the central star takes nothing short of "the perfect storm." Unless everything comes together just right, the star will remain hidden from view.

You might be wondering what all the fuss is about. After all, the star is listed as 15th magnitude, which is dim, but within the grasp of 15-inch (38cm) telescopes, perhaps even less under dark, transparent skies. So then, why is the central star so difficult through even the largest backyard scopes?

Here’s an interesting observation that I have noticed time and again when trying to see the central star. Seeing the star requires transparent skies, but not necessarily dark skies. Many amateurs equate one with the other, that dark skies are transparent skies, and vice versa. Not so.

From a stargazer's perspective, sky conditions can be divided into three categories: transparency, seeing, and sky darkness. "Transparency" refers to how clear the sky is, while "seeing" refers to the steadiness of the air mass overhead. Clouds, haze, humidity, and artificial and natural air pollutants all adversely affect both in different ways. Finally, "sky darkness" speaks to the ambient level of background light. Light pollution raises this level. People often confuse the terms transparency and sky darkness. It is certainly possible to have a city sky that is more transparent than a rural sky, but because of the lower level of sky darkness (due to urban light pollution), fainter stars will still be visible from the country site, even with its poorer transparency. 

But to the topic here, I have seen the central star on several occasions through my 18-inch (46cm) reflector from my naked-eye limiting magnitude 5 suburban backyard, but have missed it entirely on many other occasions using the same equipment from markedly darker sites. Why? Those other sites were darker (i.e., less light pollution), but the sky was not as transparent. That increased level of haze lowered the contrast between the star and the surrounding nebulosity just enough to mask the star.

That brings us to the second ingredient to seeing the star: seeing. Without steady seeing conditions, atmospheric turbulence will blur the star just enough to blend its already low-contrast glow into the Ring's donut hole. Without both conditions -- exceptional seeing and transparency -- the central star will evade even the most careful search. But it still takes more than these. Your telescope's optics must be clean, as well. Any contamination, notably skin oils on the eyepiece's eye lens, will be enough to lose the star.

Take a look at this amazing image of M57 and IC 1296 posted by CN member tolgagumus in the CCD/CMOS Astro Camera Imaging & Processing forum back in September 2018. It's the culmination of almost 30 hours of data collection taken with a Planewave 14-inch (36cm) CDK modified Dall-Kircham scope and a Finger Lakes Instrumentation MLx694 CCD imager at DSW Remote Observatories in Rowe, New Mexico.  You can read more details about the image by following the link back to the forum.

A faint, far-off barred spiral galaxy floats in the same field as you try to eye the Ring's central star. Can you also spot IC 1296? It is a tougher task than its 14th-magnitude rating would imply. That's because, as we have seen so often before, the galaxy's surface brightness skews the integrated magnitude. In 15-inch-plus (38cm+) telescopes, 14th-magnitude galaxies are fairly routine. That's assuming their light is concentrated evenly across their disk. In the case of IC 1296, the central hub of the galaxy is nearly stellar in appearance, while its broad spiral arms are unusually faint.

Back in August 2013, a Type-II supernova, SN2013ev, appeared in IC 1296. Even though it barely cracked 16th magnitude, it was actually easier to spot than its home galaxy because its feeble light was concentrated into a point source.

IC 1296 is just 4' northwest of M57, near a diamond of four 11th- to 14th-magnitude stars, as shown in the accompanying sketch and image. More specifically, it is positioned 20" southeast of the star at the diamond's northern facet. Proper magnification, in addition to dark skies and properly collimated optics, are key to spotting its dim glow.

I can probably count on one hand the number of times in the past half-dozen years when I have seen both of these challenges through my 18-inch (46cm) scope from my suburban backyard observatory. Summer haze, air turbulence, and light pollution quickly extinguish both. But on those rare evenings when the humidity is low, the seeing is calm, and the Ring is high in the sky, the elusive central star and its tiny galactic companion shine through. Indeed, under superior skies, telescopes as small as 10 inches (25cm) have shown both, so be sure to give it a go.

Have a favorite challenge object of your own? I'd love to hear about it, as well as how you did with this month's test. Contact me through my web site or post to this month's discussion forum.

Until next month, remember that half of the fun is the thrill of the chase. Game on!