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04 and 05/01/2022 Dobbist picks on Orion and Andromeda


cwis

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After a couple of months of cloud interspersed with a few short sessions with the ST80 I finally got the chance to drag the 10 inch dob outside. Goodbye tiny pretty pinprick stars, hello big fat fluffy stars but so many, many more of you. Goodbye pleasant soft circular stars towards the periphery, hello scratchy coma!

04/01/2022

Clear Outside had been warning me about the possibility of two evenings of clear skies for a few days, so I was READY! I dropped the dob outside on the 4th while it was still light, made sure the power pack was charged for my heated vest, checked collimation (OKish - looks like secondary mirror has moved ever-so-slightly) and got out there for a couple of hours.

To a large degree I was trying to remember how it all worked - I had a quick look at Orion, toured around the sky and took in the Pleiades (nicely nebulous with the dob - can't make up my mind whether that's my eyes or actually really there!)  but spent most of the session on Andromeda - it was high up so nice and clear (M42 seemed quite wobbly to me at that time) and I wanted to have an extended session to see if I could finally spot M110. I've found M32 easy to spot, even with the ST80, but even with goto, never spotted M110. Also I've managed to seize my drummer's throne height adjuster so higher targets were far more comfortable.

I finally managed to spot M110 with inverted vision after star hopping using the dob view in Sky Safari to place it in the centre of view in the 24mm (50x) UFF. My mistake was expecting it to be compact like M32 - it's much more diffuse and seems a lot dimmer (Bortle 5). I used my new secret weapon to increase eyepiece contrast ( a black t-shirt draped over my head) Should be easier to spot from now on!

05/01/2022

Got outside to a cold dew covered telescope - I like to let it cool slowly with the cover on - seems to attract less dew while it cools. While I was out there the dew on the grass froze  - minus 2 I think.

 

A slightly better prepared session on the second night with a repaired seat and thermal socks, double Stars bible, observing fluid (Red wine in the summer (gets warmer) and IPA or similar in the winter (happy cold). I only drank the one  - the rest went in the fridge to warm up after the session!) notebook and pen!

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UFF Whitterings with added astigmatism:

I started about 1930 and initially the seeing didn't look that good - I started at the Trapezium and they were moving about a fair bit - the E star was occasionally visible at 50x (24mm UFF).  It actually felt warmer than the night before because there was no wind and I think the air was less humid - it may already have been below freezing so all the moisture was probably on the grass instead of in the air. With the 18mm UFF (70x) the E was clearer and the F was hinted at. With the 10mm UFF (127x) both E and F were occasionally clear.

I noticed a smaller zone of sharpness from the 10mm than from the 18mm. I'm not sure whether this is astigmatism or coma etc but I tried the 18mm barlowed (140x) and I think it was slightly better - the zone of sharpness was larger. Or maybe it was a slightly smaller exit pupil working to supress my eye's own astigmatism. I don't know enough to be able to tell - I also find I have to be cautious with eye position with regard to star shapes too - again I'm not sure whether that's my eyes or the eyepieces... My prescription seems to be in flux at the moment (aging eyes) so maybe I need specs with smaller exit pupils now - time will tell.

I'm pleased the Svbony UFF eyepieces barlow nicely (if you're careful with eye relief) - the 24mm Altair did so I had high hopes... I may pick up the 15mm to complete the set.

The 10mm doesn't seem quite as good as the other two UFF designs in the sharpness zone size - nice and contrasty though.  Barlowing the 10mm pushed the seeing a bit too far (254x) most of the time but when the conditions momentarily played ball both E and F showed up as nice discrete tiny dots. 

Plenty of doubles in and near M42 so while I was there....

Zeta Orionis:

Blue Blue double easily split at 50x. I had to check with Sky Safari in dob view as I expected it to be harder - perhaps my collimation was better than I thought? Or perhaps the secret contrast weapon is helping? 

Struve 790:

A single finder's diameter from the above. Yellow Blue pair of roughly the same apparent magnitude - a wide split even at 50x.

Theta2 Orionis:

This looks like a mini Orion's belt! I had no idea they were gravitationally bound. Also in view were S490B and V1073 with pleasant contrasting colours. With lower magnifications I can't help glancing to see if Trap E is visible - distracting!

Struve 747 and Iota Orionis:

This was my favourite view of the night - at 50x you can see the trapezium (Theta), Theta2, Iota Orionis or Hatysa and Struve 747.  Struve 747 is a nice bright white white widely split double.  Hatysa is my favourite type of double - closely separated and different apparent magnitudes so it looks like the smaller star is peeking out from behind the larger. I liked the view so much I stepped onto the top of a very long and slippery slope and..

Took a photo. Help!

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Rigel:

Like Iota Orionis and Polaris my fave type of double - a nice bright primary and a shy secondary peeping out.  I found out Rigel was a double last year the first night I pointed the dob at Orion. I'd looked at the Trap, meh with so so seeing and decided to try the UFF24mm barlowed and picked Rigel as a close bright target.

I saw a sharply defined star and diffraction rings and a tiny perfect second dot.  The seeing and transparency were amazing - the campfire smoke had blown aside and the running water I was used to looking through was still. I turned back to the Trap and saw 4x sharp stars with diffraction rings and E and F as perfect little bright dots.  It was like that for a few seconds and then the seeing went back to normal - the wobbles poured back, the stars dimmed down.. Amazing while it lasted though!

This year at 50x the secondary was almost lost in a diffraction spike but easily discernible. At 70x it was slightly more obvious but both the primary and secondary were dancing about. One day that seeing will return.....

I came in about 2145 with a flat battery on my phone thanks to the cold and SkySafari and another one on my heated vest. I thought the thermal socks had been rubbish until I started bringing the kit in and noticed the crunchy frozen grass!

 

Edited by cwis
Spelling, grammar, incorrect names - the list is long...

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