Second Light: Orion/Helmerichs 200: 6/7th May 2022

[Captain Scarlet]

My last observing report was First Light with my Orion/Helmerichs 200mm, which while enjoyable and Moon-down was characterized by my inability to get my wider eyepieces to focus: my light cone wasn’t poking far enough outside the tube. I’d been limited to 100x magnification and higher only, with my Delos 10 and up just about able to make it.

This time, I’d given each of the 3 collimation screws 3-4 full turns ACW each, pushing the primary mirror an extra few crucial millimetres further up the tube, pushing the focal plane out by the same amount. It worked. The first eyepiece I used for rough Alignment was my Nagler 31, apparently notorious for its out-focus requirement: amongst the very “worst” out there. So I won’t need to drill any more holes further up the tube to re-site the primary’s cell unless I want to attach a camera, for which I have no plans.

For mounting for tonight’s session I decided to go for total overkill and mount the 8.5kg OTA on my AZ-EQ6, the only driven mount I have here, and to use it with the standard SynScan handset. I have a much more capable Nexus DSC, but I wanted to stay familiar with the SynScan.

After rough alignment on Polaris and Arcturus, I pointed my N31’s 2.5 degree field and 32x mag at the Double Cluster, NGC 869. Why it isn’t a Messier object I don’t know. With a 30% Moon and the Sun only 13 degrees down it was still between Nautical and Astro Twilight, so the view was quite bright. Nonetheless beautiful, both clusters in one field at slightly beyond my maximum exit pupil. I revisited it later at better darkness (21.4 IIRC) but at only 20-odd degrees elevation and above one of my distant light-domes, so it was still quite bright.

I also revisited the Cat’s Eye Nebula, NGC 6543, which I failed to find last session, just to confirm I could see it but didn’t bother upping the magnification for a closer look. Another time for a dedicated PN session, I think.

Next was M81 & M82, which were nice in the wide field, but I remember thinking the view was definitely inferior to my 12”. I would normally have had the option of using my OO/H 12” for a night like this, but it’s been in bits lately while I’ve been re-centre-spotting its primary mirror, besides tonight was specifically for the 8”.

I put in my Delos 10, upping my 32x to 100x, and did my “Izar check”. A bit wobbly, but definitely a double with clear space, and I moved on to Eps Lyrae, also nicely defined all round, but not as crisp as at First Light.

Like last time, I moved on to M13, with the Delos 6 for 145x, and the view was astounding. This night was far from perfect seeing, but the transparency was extremely good. My meter for example showed 21.4+ at zenith steadily through the night after Astro Twilight despite the 30% Moon being still well up. Back to M13, though. The view was as good as I can remember, better than for First Light, with stars peppering all the way to the centre. Even hints of the Propeller. I have seen M13 regularly through my 12” and recall being mightily impressed, and impressing others, and have definitively also seen the Propeller through it. But somehow tonight’s 8” view seemed amazing, even considering reduced 8” expectations. I now cannot wait to get my 12” out again, maybe even alongside the 8” to do a real-time comparison.

With Cygnus high enough to be worthwhile, I had a quick look at Albireo: blue/yellow lovely as ever. Not a patch on Almach obviously ;), but still worthy of its name “Jewel of the Sky”.

I put the Nagler 31 back in and selected Sadr, the middle star of Cygnus. I wanted to browse around the star-fields. It was entrancing, with obvious patches of dark nebula too. The first time I’ve really done this actually, as I’ve only recently had a wide-field option out here.

I finished on the Moon, it was a seething wobbly mess. It was directly above Schull a few km distant, and I must have been looking through heat plumes in that direction.

All in all I’m now more than happy with my nearly-finished 8” f/4.4. It has a 1/10 Orion mirror in an Orion CNC cell. The Helmerichs tube is supremely stiff. The focuser is a Baader Diamond Steeltrack with the absolute minimum out-focus I can get away with (about 75-80mm). Its centre-spot has been repositioned to exactly the right place. I don’t feel a finder-scope is necessary for such a fast small scope, so I’ve allocated it one of my Baader Sky Surfer Vs. The only serious modification left to do is to get myself a 48mm or 50mm secondary to reduce the CO to 25% or less; currently it sports a 63mm (CO 31.5%, far too much for my taste). And the rest is essentially cosmetic: I’ll replace all the cheap Orion cross-head fittings with Torx or Hex from accu.co.uk: secondary collimation-screws, primary-cell fixing bolts; finder-shoe bolts.

Thanks for reading.

Magnus.

PS couldn't resist adding a shot I took with the camera on the tripod in the pic at the start

 

Edited May 8, 2022 by Captain Scarlet