First Proper Light with the Vixen GPD2 - Saturn & Caroline's Rose 12th Sep 2024

[Captain Scarlet]

I couldn’t believe it. The afternoon was beautiful and clear and all the forecasts had suddenly changed to suggest clarity for the whole night. And so it proved.

Those were almost the same words I used to start my last report-worthy observing session, but that was more than two months ago, in early July. Three or four times since then, I had actually gone to the trouble of setting up only to have to put it away after weather rolled in. Extremely frustrating.

Yesterday, all the circumstances fell into place. I wasn’t too tired. I had a free late afternoon to set up in leisurely fashion. I had nothing on early the next day to prevent a late night.

I’ve had just one quick look at Saturn this apparition, a couple of weeks ago, literally only ten minutes before cloud rolled in. There’s been mention lately of Caroline’s Rose, so that got a look. Jupiter and the Pleiades featured.

My latest mount is a Vixen GPD2 equatorial, which I bought as a purely manual mount but added a Skywatcher EQ5-style motor kit to drive the RA axis. I hadn’t yet had a proper extended session with this and I wanted to acquaint myself with how to use it in the field. That ruled out using my 12” newt – at around 22kg all-up, too heavy – so my Stellarvue 140mm at 12-13kg it was. At around 12-13kg this scope exceeds the ~10kg published stated capacity of the GPD2, but that figure seems conservative to me. The mount lives in my utility room right next to a SkyTee2, which has no official payload AFAIK but I’ve seen photos of people happily putting crazy stuff onto it, way beyond my 140mm (by the way I have seen “that” photo of the failed Skytee2). The radii of the GPD2’s RA and Dec axes are significantly bigger than those of the Skytee2: the GPD2 is altogether visibly chunkier. Add in the superior quality of the engineering in the Vixen (obvious in use), and I’m confident the Vixen will comfortably win any payload competition. So I have no problem loading the Vixen with 12-13kg of refractor. My only concern was whether the RA motor could handle the moment, which it turned out, it did.

I pointed the mount North, levelled the mount head, attached counterweights and OTA and awaited darkness. What, levelled an EQ mount? I hear you ask. I’ve pre-set the mount’s Latitude bolts to point the mount exactly 51.4 degrees up from a level tripod-top, so once I’ve aimed the flat side-plates to my North aiming-point, I can be sure the RA axis is pointing sufficiently accurately at the NEP for visual use. And it makes my EQ “Go-To” method work (about which more below), which would be irritatingly inaccurate if I used only a rough polar-align method.

My first target was, naturally, Saturn. To get the scope pointed in the right place I tried to imagine myself leaning over at the same angle as the RA axis and trying to “intuit” the RA and Dec axes as left-right and up-down from a bent-sideways position. I got there in the end, but it wasn’t pretty. Also, using the axis clutches to try to point at a particular place then fine-tuning with the slow-motion knobs I could see was going to become frustrating, perhaps a deal-breaker.

Still, I got to Saturn in the end, engaged the RA motor clutch and started viewing. So lovely to have it kept in the field of view at high magnification. However, it was still quite early and Saturn was both rather low and over the heat-plumes of a handful of illegally-built (no planning permission, causing local silent outrage, and permanently-lit) camping-pod/huts further up the hillside. Saturn was a bit wobbly, Titan and Iapetus were visible and just the merest hint of Tethys off to the “left”. But no sign of Rhea, which I knew was supposed to be below the left-hand ring. Still, nice to see the nearly edge-on rings.

I moved on to Caroline’s Rose open cluster, having read much on here recently. I checked where it was on SS, and having my Nikon 18x70s to hand as well, confirmed its position. It was an obvious smudge through the bins.  But how to wrestle the manual EQ mount to point at it? I tried the “leaning over” method, but being so high up, it was difficult. Hmm. At this point I realized I was being an idiot. I quickly went back to Saturn, found it, checked its Declination coordinate in SS, and set the Dec setting-circle on the mount to that value. I then looked up the Declination value for Caroline’s Rose, released the clutch and turned the mount to that Dec value. Then all I needed to do was open the RA clutch, rotate it round until it was sure enough pointing directly at the target. Fine movements could then be done with the RA motor controls and the Dec slo-mo knob. The better your initial polar alignment, the better this works, obviously.

A few words about the RA motor controller. It’s a very basic (Skywatcher) handset with four buttons, 8x FWD, 8x back (so not very fast and certainly not for slewing large distances), 1x fwds and 1x back, plus an on/off button and N/S button. In the very centre is a green LED to show that power is on. That LED, in the dark when you are dark-adapted, is BLINDING. Today I covered it with a layer of flock material. Power is a 6v input, for now provided by the supplied 4-pack of D batteries. I’d like to find a rechargeable 6v unit at some stage.

Pleased with myself for working out how to manually “goto” with an EQ mount, I found and observed Caroline’s Rose. I used too much magnification at first, and was not at any stage able to see the faint stars behind the brighter ones. The rose-character I couldn’t really discern, even backing off the mag to as low as 30x (31 Nagler). I was definitely in the right place, I’d checked the surrounding star-patterns. By the time I got to it, the Moon had set and it was at least 21.3, so Moon-washing wasn’t the culprit. I’ll try again on another night and with a larger scope.

I returned to Saturn. By now it was both higher and well past the heat-plumes. And I could easily see Rhea, invisible before, plus Dione off the top of the right-hand-side ring. There was plenty of colour and detail on the planet, the rings and where they crossed the disc. Very satisfying.

At one stage (actually exactly 2313 because I immediately texted my Astro group “bloody hell, did anyone see that?”) whilst swapping between eyepieces, the whole landscape shockingly lit up as if daylight, like lightning but lasting perhaps a second or two. Everything was bright white. It cast my shadow towards Saturn, so I whirled around to catch the final moments of a meteor Bolide exploding, breaking up into five or so pieces and themselves exploding, low to the NW. It was the brightest meteor I have ever experienced, by a long way. And yet I’ve found yet who noticed it, very odd.

Lastly, Jupiter was high enough for a look, but sadly he was still too low for a good view. Wobbly and some CA. It was my first view of him this season, though. I moved on to the Pleiades, always so lovely to see the refractor-sharp stars of all sizes, others so bright, and a hint of the hazy nebulosity. By now my eyepieces were starting to fog with a tell-tale haze around objects which definitely was NOT nebulosity, and I was getting cold so time to pack up. As I was doing so, around 0130 with leisurely return trips, I measured 21.60 at zenith, and the naked-eye transparency was extraordinary. Mars was obvious by now too, and very red. On nights like this I always pack up slowly to stop and gawp. And no hint of any Aurora.

Thanks for reading, Magnus

 

Edited September 13 by Captain Scarlet

[CraigT82]

Very nice read Magnus, good use of the setting circle can’t remember the last time I read about anyone using those! Do you still have the AZEQ6 or is that just reserved for heady duty lifting? 

[Captain Scarlet]

Thanks Craig. Yes I still have the az-eq6, but that takes two heavy-load trips or a wheelbarrow whereas I can carry this tripod-pier-mount out in one go. It seems the former is consigned to the 12” from now on.

[lunator]

The GPD2 is a very good mount

I have it as a second mount and it always performs well. 

Mine came with my OMC250 which is a pretty heavy scope.. it always managed the weight ok. If you want the correct drives then the DD3 drive system is basic but well built. 

cheers

Ian

[Stu]

Lovely report Magnus. I’ve probably only caught Caroline’s Rose well a couple of time, can’t recall which scope or power I used, will have a trawl around and see if I can find my notes.

[Nik271]

Great report, Magnus, enjoyed reading it. By the way I power the skywatcher RA motor for my EQ5 with a lithium power bank. The deliver 5 volts at 2 amps and it's sufficient to run the handset and the motor. Mine lasts for ages.