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Grooving with Mr Struve


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I’m still experimenting with eyepiece combinations for the Evostar 72ED. I can more easily use the 72ED on the Sky-Watcher AZ5 mount than the Altair 60EDF which is a tad rear-heavy (I should have bought the Takahashi FS-60 lol).  I save the 60mm Altair for a 2” diagonal and heavier accessories. It’s also usually deployed on the heavier Vixen Porta II/TL-130. 




The Vixen combo is also reserved for my bigger refractors and 127mm Maksutov. With the 72ED the 1mm-0.5mm exit pupil (70x to 140x) is covered by the Tele Vue Nagler zoom. The 9mm T6 Nagler covers the 1.5mm exit pupil with the 19mm Panoptic at about a 3.2mm exit (22x). This is perfectly fine for most open clusters, stars, asterisms and DSO’s that can be viewed with a small refractor. 




However, I sometimes like to use a high contrast (OIII) filter to view some nebulae and deep sky objects, especially in the Summer Triangle. Basically I need a 4mm exit pupil at least. The 24mm Panoptic gives me this, but it’s a tad bulky in my nylon bag when included with the other EP’s. I have a collection of 1.25” OIII filters. My newest is an Astronomik which I only got to use once (with a Baader 35mm Eudiascopic). I have an old 1.25” Lumicon, a Celestron, Explore Scientific and Baader OIII filters among others. Before I became ill I planned to compare their individual efficacies and write about it.




This never materialised. I also misplaced the Astronomik OIII, until now (Swiss cheese brain syndrome?). I originally planned on using a 32mm TV Plossl. This has an enormous 27mm field stop, larger than average eye lens, and, let’s face it, it is a bloody huge Plossl! I daylight tested the 32mm with the OIII. I’ve never taken much notice of the ‘coffee cup’ (as in like looking through liquid coffee) arguments about TV coatings on certain eyepieces. Supposedly Al Nagler’s argument was that the coatings were a bit of a fiscal ‘compromise’ ($) with the original equipment manufacturer. 




In comparison I seriously thought the 32mm Takahashi Abbe orthoscopic had far better transmission and better contrast than the 32mm TV Plossl. Eventually I settled on the ‘Mighty Twenty Five’ or 25mm Tele Vue Plossl.




The transmission was almost as good as the Takahashi and I got an adequate exit pupil with just under three arc degrees of TFOV (about the same field as the 19mm Panoptic). 




I took almost a year off stargazing due to ill health (including some hospitalisation), fortunately I’m a tad stubborn, so in late 2023 I started to get out under the stars again. Eighteen of those twenty one sessions in 2023 were with small apochromatic refractors. I use apertures of 72mm and 60mm predominantly because they are so much easier for me to use. I understand aperture fever but sometimes you have to work with what you’ve got. I've often been mocked for using small scopes (you know who you are: SGL, SkySearchers) and I've never quite understood the mentality of someone who derides the disabled. After all, it says more about them than me. I’ve literally had brain damage so I tend to forget a lot. My brain probably resembles Swiss cheese. Come to think of it, I can’t even remember where I put my Swiss cheese (or even if I have cheese products of any geographic origin).




I found the Ring Nebula aka M57 and the sublime dual stars known as the ‘Double Double’ (Epsilon Lyrae) on the oddly bright 10th of May (during a possible Carrington Event). I hadn’t seen them since the Summer of 2022. I knew there were other interesting objects in Lyra, but my Swiss cheesed brain just was not computing (probably runs on cheesy Windows). So, I checked back on some of my astro logs. Then I remembered the other Double Double. Yes, would you Adam’n’Eve it? There is another beautiful double pair in the constellation of The Lyre (and that’s no lie lol).




I was set-up with the 72ED at about 00:05 BST, 19/5/24. Conditions were above average, no real jet stream problems although there was an 80.8% illuminated Moon (Virgo). Which wasn’t helping particularly.




I just had to test the 'Mighty Twenty Five' on the plethora of open clusters in The Summer Triangle although it seemed to take a few minutes to locate Brocchi’s Cluster. It was then that I noticed a faint and slight green glow in a line roughly east-west right at the zenith. It stretched across the sky. Not unlike viewing a dim nebula through an OIII filter. Even though there was a bright Moon I could still see it. It couldn’t be the Milky way, which I could also just about see, regardless of the near 29° Virgo Moon. This may have been my eyes desperately trying to compensate for the devil’s searchlight of a Moon, or it may have been the still apparently visible Aurora Borealis. 




The ‘Coathanger’ was beautifully framed with the 25mm TV Plossl. This time I found the Ring Nebula again quite easily after a short while, again with both the Nagler zoom and the 9mm T6.  Eta Bootis split nicely with the zoom as well. I managed to get a nice view of Polaris and the Engagement Ring. Eventually I just had to try the Astronomik OIII. Although it took me a few minutes to find the ‘apple core’ of M27. The Astronomik had above average transmission and was well contrasted, and although I was only observing at about a paltry 17x, the apple core was unmissable. I blame the Moon for the difficulty I had locating both Hercules globular clusters. Although they looked quite good considering.


Struve 2470 and 2474 are an interesting pair of double stars in Lyra comprising of SAO (Smithsonian Astrophysical Observatory) 67867 and SAO 67870 as the northern pair. With SAO 67879 and SAO 67875 as the more southerly double. Because of their similarity to Epsilon Lyrae they are often referred to as the ‘Other Double Double’.

This little collection of stars are an often overlooked foursome. The group can appear quite dramatic when first discovered as both pairs of stars are almost parallel. They are probably best observed around a 50-80x magnification, depending on conditions. The Struve pair are not too difficult to find as they make a loose triangle with ᵦ Lyr (Sheliak) and ᵞ Lyr (Sulafat).




It took me only a few minutes to locate Struve 2470 and 2474 and they made my night. The colours were beautifully defined, I see them with yellow, yellow-white, blue and lilac hues depending on the particular star. 80-90x seemed to be the optimal magnification. I split more doubles, Lyra seems to be chocablock with them lol. As 03:00 approached I swept the south for the Sagittarius Star Cluster. I think I got a hint of it with the 25mm, but the now low Moon was causing problems. All in all, it was a good three hour session with the 72mm Evostar.



*Austin Powers voice*: “Struvey baby … “


Edited by Nightspore
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An entertaining and detailed report. I’m impressed you can stay up so late/early! Thanks for posting.

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4 hours ago, Anaximander said:

An entertaining and detailed report. I’m impressed you can stay up so late/early! Thanks for posting.


Thanks. I was surprised that I stayed out so long too. I've only had 7 sessions this year, the conditions were decent (the Moon was a PITA) and there was a fair bit to observe. It was pleasantly warm, and relatively dew free. Anyone would think it was summer lol.



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