Dew 1 - Magnus 0 . 12" session 7/8th July 2024

[Captain Scarlet]

I couldn’t believe it. The afternoon was beautiful and clear and all the forecasts suggested clarity for the whole night. And so it proved. I planned to get out my 300mm Newtonian and set it up round the back, facing South and South-East. The last two times I’ve had this scope out and fully set up, plus another with my 200mm Newt, I’ve had to simply pack it all away again at the onset of solid cloud. Not this time.

All was far from perfect though. The whole night was characterised by a fight with dew, which, on points, I think I lost.

AZ-EQ6 on Planet; top levelled; collimated with scope at around 30 degrees elevation; Nexus DSC attached; SW 50ED/Pan24 super-finder attached; alignment on Polaris and Altair with Delos 17.3 for 106x; around midnight and ready to go.

First stop was Izar, with Delos 10 for 183x, to check the seeing and the thermal state of the scope. The double was split easily enough, the yellow/white and bluish colours on show, but it was a little scruffy. Racking out the focuser I could see swirling tube currents and it was clear the mirror wasn’t “at shape” either yet.

With similar intent, I headed to epsilon Lyrae to see what the Double-Double looked like. Once again, easily enough split in such a large scope, but there was an element to the untidiness that suggested coma to me. I quickly re-checked collimation and sure enough it was a good few millimeters out at the return-face. On re-collimating (and re-finding my target since collimation changes alter the pointing-direction of a mirror), It was MUCH cleaner. Amazing how a seemingly small collimation error makes such a visual difference.

I diverted to nearby Vega for a quick star-test and see how my thermals were doing, and was concerned to see a light haze around the star. I’ve come to recognize this as a dew symptom. Ignoring it for the time being, I selected Messier 11, the Wild Duck Cluster, which I’ve not seen for two years. It was disappointing, the sort of view I’d have expected in a much smaller scope. I checked for dew by pointing my head-torch into the eyepiece whilst looking down the main tube at the illuminated reflection of the secondary in the primary. Dew, oh yes! Lots of it. Damnit.

WARNING: those of a sensitive disposition, please skip this paragraph and look away now – what follows is not suitable for you. My solution to the dew, which in the end only bought me a few minutes, was: I WIPED the secondary with a tissue. SHRIIIEEEK!!!! Yes I know, I know.

Dew temporarily sorted, M11 was transformed. What a beauty of a cluster. Moving on to Messier 15, a globular this time, was similarly satisfying.

I wanted some galaxies, but with dew already making its presence felt again I realized I was losing the battle. So I put in my Nagler 31 for 59x and 1.4 degrees, and selected Messier 31. M110 and M32 were easily seen, but no sign of dust lanes, I suspect the sheen of dew was obscuring them.

I decided, back with the Delos 10, to have a second look at that small OC, Trumpler 1, which I’d stumbled across a month or so ago in my 140 refractor, to see if I could make out that 3rd star as a double. Although the secondary was surely badly obscured, and the overall view was nowhere near as clean as through the frac, I could see that that star was indeed a double. In fact I went to a very dim 406x with the Delos 4.5 to be sure.

I finally attempted Izar again still at 406x, but my mount decided to have a power hiccough just at that point and reset itself. Time to call it a night, by now after 2am.

The transparency of the night was something else. The Milky Way was clear and stark all the way down to the southern horizon. My stop-and-gawp breaks made packing up a lot longer than usual, and rewarded me with two meteors, streaking upward overhead south to north-west through the Great Bear; and an extended view of the ISS, through which, with my 15x56 binoculars, I could easily see for the first time ever, its shape! I was quite pleased with that.

All in all, far from the best session but still so good to get out.

And just for some final visual stimulation, as I didn’t have the energy to capture the MW which would have been amazing, a picture I got earlier during the evening of the 4% Moon. Mercury is detectable but only by extreme pixel-peeping. Mercury was quite sharp and clear through 10x50 binoculars, though.

Bed at 3am, thanks for Reading, Magnus

Edited July 8 by Captain Scarlet

[GordonD]

Lovely report - thanks for posting! It looks like a spectacular location.

[Stu]

A nice read Magnus, despite the frustrations. Maybe invest in a 12V hairdryer to clear the dew from the secondary?

[Captain Scarlet]

21 minutes ago, Stu said:

A nice read Magnus, despite the frustrations. Maybe invest in a 12V hairdryer to clear the dew from the secondary?

Can you recommend one? I have looked before but all the searches provide promising links, then simply direct you to corded dryers. I lose the will to live quickly, and give up.

I do have a corded hairdryer which I’ve used in this scenario, but the extra hassle running out the trailing sockets etc is too much. Also the last time I used it, I blew warm air down the tube, a whole load of moisture immediately condensed out and layered the primary with dew as well! I felt really stupid, though I did find it quite interesting. That was the last time. A 12V might be low enough power to prevent that happening.

[Stu]

8 minutes ago, Captain Scarlet said:

Can you recommend one? I have looked before but all the searches provide promising links, then simply direct you to corded dryers. I lose the will to live quickly, and give up.

I do have a corded hairdryer which I’ve used in this scenario, but the extra hassle running out the trailing sockets etc is too much. Also the last time I used it, I blew warm air down the tube, a whole load of moisture immediately condensed out and layered the primary with dew as well! I felt really stupid, though I did find it quite interesting. That was the last time. A 12V might be low enough power to prevent that happening.

Had a quick search on Amazon and it shows a few there which are 12V with ‘cigarette lighter’ style connectors. Not a recommendation but here are a couple of examples:

https://amzn.eu/d/05Q7PrE7

https://amzn.eu/d/049LFlBf

 

[Zermelo]

I have one from Amazon that looks identical to the first of @stu 's links.

Having two settings means that it can be operated in a "gentler" mode. I measured the current drawn as 0.5A for the lower setting and 14A for the higher, which may blow a fuse in some power tanks.

I have yet to use it in anger!

[magnahrl]

Magnus, thanks for an excellent report. Though you had some issues which I for sure can recognize I still long for the darkness to return here at 57N. By the way, some years ago I tried a hairdryer to fight dew on the corrector on my C8. Doubtful effect apart from stealing lots of power from my battery😟

Magnus A.

[bosun21]

Are you using a dew shield Magnus? I have found that using one keeps my secondary clear of dew throughout my session. You have my sympathies as dew can be a real joy killer. Great read Magnus.

[Captain Scarlet]

14 hours ago, bosun21 said:

Are you using a dew shield Magnus? I have found that using one keeps my secondary clear of dew throughout my session. You have my sympathies as dew can be a real joy killer. Great read Magnus.

I do plan to make a stray-light / dew shield. The tube was originally specified for a shorter focal-length mirror, so I’ve eked out every cm by putting the spider right at the entrance to the tube. A while ago I accidentally ordered a 60m x 1.5m (!!!) roll of acetate sheet so I can make one out of that, I also have a spare yoga mat which would also do. I need to decide.

[josefk]

On 08/07/2024 at 22:32, Zermelo said:

I have one from Amazon that looks identical to the first of @stu 's links.

Having two settings means that it can be operated in a "gentler" mode. I measured the current drawn as 0.5A for the lower setting and 14A for the higher, which may blow a fuse in some power tanks.

I have yet to use it in anger!

Is it fairly quiet @Zermelo - if quiet i would add this to my "car pack" set-up for emergencies or even for drying the outside of the OTA etc before putting it away. I HATE dew!

[josefk]

Nice skies as always @Captain Scarlet and descriptions. Shame about the dew incursion/curtailment. Is that an estuary or wetland near you? i suppose with either some low level damp in an evening is a hazard.

[Captain Scarlet]

4 hours ago, josefk said:

Nice skies as always @Captain Scarlet and descriptions. Shame about the dew incursion/curtailment. Is that an estuary or wetland near you? i suppose with either some low level damp in an evening is a hazard.

It’s the sea, known as the Carbery Isles or 100 islands. Essentially the North Atlantic. We’re at 95m elevation. That night and the next saw a particularly heavy dew. I don’t mind too much, actually my last few sessions aside from that have been remarkably free of dew.

[Zermelo]

4 hours ago, josefk said:

Is it fairly quiet @Zermelo - if quiet i would add this to my "car pack" set-up for emergencies or even for drying the outside of the OTA etc before putting it away. I HATE dew!

It's pretty quiet on the low setting