Backyard Stargazing : Messier Object Slew-Fest and Eyepiece Shootout

in astronomy •  4 months ago


Photo : Orion 100mm achromat refractor on EQ Skyview mount and custom wood tripod.

An impromptu session presented itself, so I set up the mount and tripod in the backyard. I put the OTA (Orion 100mm F/6 achromat) on the mount, polar align, and by then the sun is set and the sky is surprisingly clear - despite the forecast of gloom by both the CSC and the local weatherman.

Recently I have been on an eyepiece-buying spree, trying to determine what exactly I like in an eyepiece. (I'm still figuring all of this out to settle on some equipment I will use for the long term, instead the constant ongoing gear shuffle my life has been for months now) ... I had some new ones to try out last night : Vintage Celestron 6mm ortho volcano-top, a couple of vintage kellners (just for kicks, I knew these wouldn't make the cut), and a Televue 20mm Plossl. I had high hopes for the new TV Plossl.

While the scope was cooling down, I ducked inside (eyepatch on like a pirate), dripped myself a cup of hot Sumatra, went back outside (8x42 binoculars in hand) and waited for my eyes to adapt.

My first target was the M42 complex. I slewed around, using my 2" 42mm GSO SV ep as a finder. Once I zeroed in on the nebula, I tried out a succession of eyepiece and barlow combinations on it. As the minutes passed observing M42 and it's immediate environs, my eyes got more adapted, and I lingered on M42 for a long time - very long. For an hour, I switched eyepieces until I decided which combinations I liked best. For the sake of brevity, I will leave out less notable combinations.

On M42, hands down, the TV 7mm T1 Nagler is the default eyepiece. At ~86x, the nebula exhibits much detail, streamers and some hints of mottling are evident. Overall color impression is still grey-bluish with none of the hints of green sometimes reported by others (and myself in a 25x100 binocular) ... Interestingly, my second-favorite combination to use on M42 is the 28mm RKE and 2" 2x GSO barlow. This yields about 1.2 degrees at 42x, giving a nice comfortable, bright view. Eye relief on the old RKE is fantastic, and the eye lens spans the entire unthreaded barrel. I can sit back comfortably, with my glasses on, and take in the entire view. Carefully fiddling with the microfocus yields a view that is sharp across most of the field, even at f/6. The 28 RKE is a definite sleeper. As an eyeglass wearer, I cannot speak enough about comfortable eye relief and the RKE delivers with flying colors, even at 42x. Plus, I love the "cool" feel to the view (cold) and the view seems brighter than the much-hyped TV 20mm Plossl.

Which reminds me - I am disappointed by the TV 20mm Plossl. Frankly. And this surprised me. The RKE 28 blows it out of the water. No kidding. Your mileage may vary, but to my eyes (and for my tastes) the RKE 28 provides a superior view. Of course, the magnifications between the TV 20 and the RKE 28 vary - 30x versus 21x. So a direct comparison is unfair. But I can still compare the enjoyment I derived while viewing M42 with the two eyepieces - and, the RKE wins hands down. The TV provides a nice view, but the eye relief is shorter and one must roll back the rubber cup and get down close (and remove one's eyeglasses) to see the entire field. When doing this, one is rewarded with a sharp view across the entire field. But I get the feeling, and some will argue this, that light transmission in the TV was not what I expected it to be. Again, the RKE appeared to win out here. Sure, the magnifications were a little different, so the exit pupil and brightness differs. Apples and oranges. But my gut says the RKE gives the brighter image, mm to mm.

Barlowed, the RKE beat the TV again. When barlowed, I can still sit back at a distance with my glasses on and see the entire 1+ degree field at 44x. The TV requires me to get down close and wear it like a contact lens to see 60x w/ a .8 degree field. I will say this much though : on-axis, the TV is the sharper eyepiece, just barely. Again, though, the increased magnification might be working in it's favor, but it did seem sharper (by a slim margin) and the overall view was much "warmer" in the TV on all targets. So I guess it is true what they say - TV eyepieces are indeed warm.


Photo : a selection of my gear - eyepieces, filters, barlows, etc.

Briefly now, favorite ep combos for various DSO's :

M41 : RKE 28 barlowed.

M44 : GSO 42 w/ barlow element threaded onto the ep for 1.5x
(this framed the cluster quite nicely and gives a bright, sharp view)

M50 : RKE 28 barlowed.

M35 : RKE 28 barlowed.

Saturn : T1 7mm "straight" and barlowed. Saw hints of Cassini at 86x. Image scale much bigger barlowed at ~172x, but a little softer with no sign of Cassini. WO VR-1 filter helps, but overall impression is still a little soft. Of course, seeing was not so good, so 172x is pushing it from my backyard in an 4" f/6 achro. 6mm Ortho gives a nice sharp view at 100x, with Cassini evident, but it will not come to focus using the barlow. Tragic, because the ortho was promising on all targets - crisp and bright, but small FOV.

Coma Star Cluster - RKE 28.

So, even though this was not intended as an eyepiece "shootout", it turned out that way. Even though I did not log many targets, I spent considerable time on each one. Slowly tracking it across the sky for a half-hour or more, using various ep combos. To my surprise, the RKE beat out the TV 20. With a TV Widefield 15mm on the way, and the RKE holding it's own, it appears the TV 20 will go on the trading block. No need for it.

My favorite targets of the night were M42 and M44. I spent well over an hour on each, probably two hours total on the M42 area. After being fully dark-adapted, I looked long and hard at the nebula using the 7mm T1 barlowed. A good amount of subtle texture was seen and the nebulosity fanned out on each side of the view, all the way out to the field stop. Nice. Using averted vision, a number of faint stars would wink in and out of sight from within the mass of nebulosity. I thought I detected ever so briefly, a 5th element of the Trap. I could be wrong and probably was. But once or twice I did spy a phantom point of light in the right place - but it was too elusive to claim.

Clear dark skies,


All of my astronomy and science articles :

Photos : all photos by me, Mike Gilmer (Galactic Stone)

Note : an earlier version of my report appeared on the Cloudy Nights website.

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