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An SGL-Thread inspired 10" Dob Session


SuburbanMak

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Last nights session was very much "brought to me by SGL".   

Starting a couple of weeks ago when my new AZGTiX mount turned up allowing me to run ST80 & Mak 127 side by side, @RobertI noted that in my photo of the new gear my Dob looked like it was "sulking in the corner".     Then reading @Optic Nerve's thread on collimation queries got me thinking about Dob-tweaking matters again, the final push came from @Mr Spock's comment on @F15Rules' excellent thread on sharp to the edge eyepieces that his new Stellalyra 30mm Ultra Flat Field was working beautifully in his own 12" F5. All were signs it was time to get the Dob out. 

Last night looked like the last for a few where there would be a clear sky so I set up as it got dark and left to cool. Seeing was very steady, transparency less good - maybe 3/5, calm and hovering around freezing at just after 7pm. 

I did a quick collimation tweak, aligned the Telrad on RIgel and swung to the Pleiades.  The first thing I always notice when I switch to the 10" is just how bright the stars appear compared to my smaller aperture scopes - the Pleaides were truly sparkling but in my Baader Aspheric 31mm, definitely little comet shapes from about 2/3s the way to the edge, along with some kind of spherical/pincushion error the overall effect makes me almost seasick after a while.   

Switching in the Stellalyra 30mm Ultra Flat Field brought an immediate improvement - yes there is still some focus difference across the field but the coma effect is vastly reduced and the image is sharp in the central 75% or so and absolutely acceptable right across the field.  Its not quite as transformative as it was in the ST80 but the clear conclusion is that this APM UFF-Clone 30mm is a superb performer in an f5 'scope.  I'm not ruling out having a go with a coma corrector at some point, but the 30mm UFF will almost certainly mean that my GSO 10" f5 will see a lot more starlight this year!   M45 in this eyepiece was gorgeous, I couldn't be sure about the Merope Nebula given slightly iffy transparency and the ambient LP around but i had a sense it was just beyond vision.  

The other huge improvement for Dob-comfort is the addition of a proper observing chair (Berlebach Charon), I've found the Dob really uncomfortable to use up to now but this simple but classy piece of kit is an absolute game-changer in this regard.   

M42 was showing plenty of billowing 3D texture, a real sense of the stars embedded within. For the first time I could see a dim glow where the Running Man Nebula (NGC 1977) should be and I have looked in vain many times. I couldn't make out the "man" but in AV there was a definite glow in that region  which - considering my light polluted back yard -I was really excited by.  On splitting the Trap' this was where I concluded that I don't have perfect collimation yet, I could get 5 stars (with a Hyperion Zoom from around 120x) but not the sixth, mainly due to the messiness of the picture. The separation between the others notably greater than it appears in my 5 inch Mak. 

Star colours were gorgeous with this combination, I was drawn to the profound orange of 31 Orionis a degree and half or so SW of the easily & widely-split Mintaka. 

On to M35 which despite the murk was revealing a rich eyeful of stars criss-crossed with darker lanes.  Whilst a good view in the 30mm, this really shone in the Baader zoom at mid-focal lengths (60-80x).

Up overhead to the Double Cluster - really enjoying that chair at these angles! - and its just breathtaking, even though not in the best direction for me, over the lights of the town centre - but still one my absolute favourite "Deep-space" fileds of view. Stunning in both eyepieces, dense glitter separated by a dark chasm and, in the 1.68 degrees of the 30mm, on an almost equally rich background.   

Around this time the bellringers started practicing over at the cathedral adding a nice soundtrack to my town-centre session.   

As I was already almost pointing overhead I figured it was time for another look at the comet C/2022/E3 (ZTF)  easy to find next to the (again brightly orange) Iota Aurigae. The bright, coloured star with the diffuse comet, showing some extension in AV, made a super field in the 30mm (42x) against a sprinkling of mag 8-10 stars in what looked to me like a mini-Hercules shape. This all reminded me of the sketching challenge so I went inside and after a short (warm & whisky) break came back out and made a sketch.  Spending the extra time on the view and looking closely at the relative positions to capture them on paper, really brought home the rate of progress of the comet - moving around a half degree North in the half hour or so it took me to make the sketch, which I based on its original position.  

Transparency began to decline further around 9 o'clock so I called it a night and, having heaved the Dob under cover, put the bin-lid type lens cap on and, for some stupid reason, gave it a gentle pat - wedging it askew in the top of the tube!   For a minute or two I had a vision of mangled spider-veins and collimating from scratch rebuilds, but on getting inside found to my relief no damage done! Won't be doing that again....

So a great session and a different pace of observing, fewer targets, in seated comfort, sketching, all manual - Telrad powered finding and the combination of just 2 eyepieces in 2" mode all night working really well.   I must make the effort to get the Dob out more often!  

 

 

 

 

 

 

 

 

 

 

 

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Edited by SuburbanMak
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