Dilemma and Delights in Doubles

[Bombardon (Eugene)]

I suffer a major double star dilemma. I find that whether atmosphere or telescope settling in this problem remains. If I leave my 10" F5 to settle on the grass for 30 minutes, I usually end up with moisture everywhere, If I start viewing straight away, deep sky is not a problem but close doubles look disappointingly like poor collimation. Last night a case in point. I stayed with Gemini for an hour and while the Eskimo nebula(NGC2392) was perfectly clear and the striking M35 oc showed crisp bows of stars, some reasonably close doubles such as Lambda Gemini. sep 9.7" and Delta Gemini sep. 5.8" were impossible in a 9mm eyepiece. After about half an hour and just as the tissues reached the findercope, I suddenly had a brilliant scope, Rigel was easy and the two mentioned above and more became a breeze. Seeing seemed the same but moisture started to cover everything. Main mirror and diagonal were ok. I have never used the fan built into the main mirror. Would this help? I have tried a sheet over the lot and have considered a temporary tarp arrangement. I do know I get more moisture than most in the area as I am near a river and pretty low down. Do I go down the track of heaters everywhere or have a just a bad hell hole in my backyard? All suggestions will be borne with fortitude

[The Mekon (John Briggs)]

Eugene, you are not alone in having this difficulty early on in the evening.

I have 18" F4.5 so it takes quite a while for things to stabilise - its kept in the garage by day and right now as the sun is behind the trees, it is out trying to cool down with the evening. Of course the night air is always dropping faster than the scope. I have a full set of dew heaters which do help later on, but the biggest help I find with double stars is my off axis mask. I have made a 7" one which makes the scope work at around F11 and really improves double star performance. I suggest you make a 4" one that sits between the secondary vanes. Your scope will work at F12 - focus without the mask and then set the mask over the tube. Instant best focus spot!
My mask is a bit of wood veneer, painted black with Velcro fasteners.
Cost is nothing so give it a go. It does not work so well on very faint stars. Many commentators have scorned these masks over the years, but I find disagree with them and reckon they are not observing under difficult conditions.

[Bombardon (Eugene)]

Many thanks, John. I will try the mask. Tried a later start tonight but foiled by clouds at 10 p.m. The sweet spot in the westerlies in Winter( when they have nearly blown out) is usually my best time. However, Northern horizon gems have a short life at my latitude.

[The Mekon (John Briggs)]

I had good conditions from 2100 -2230 last night. Cloud rolled in just after 2230. Used the mask to resolve 32 Orion - lovely clear split. Also I noticed that with the mask, the E & F stars in the trapezium were clearer and more distinct than without. I could see both at full aperture and they were a lot brighter but the F star was being outshone by the C star and not as easy to pick up without the mask.

[Bombardon (Eugene)]

Good work on 32 Orion last night, John. Sissy Haas gives it 1.2" sep. I have much to explore in Orion when I get the mask sorted out. The Trapezium has rarely been crisp for me in the 10' all summer with just a hint of E component. In another century, John. I figured my finest mirror, a 12" F9!! would you believe. In those days figuring fast mirrors was considered a job for the experts I could always see ABCDEF with it on clear nights. Sadly got rid of it to a willing buyer, after that test, Main reason for sale: High Stepladder and ageing knees! I always knew a good night was coming up when the Antares aqua companion popped out at sunset.Weather looks better tonight. Still have a list for Gemini. Fingers crossed