Fraunhoffer

best book I ever bought. 
There is a 5th edition 2018 - I expect all the updates are on the Cambridge site posted above anyway.

I love this technique.
I got some sketching pencils and charcoals for Christmas. Eager to try them out.

very nice. 
I like the effect with charcoal + chalk.

I saw on space weather that a new sunspot cycle had started so I dusted off (literally) my little Bresser scope and found the (also dusty) solar filters to take a view.

Even at 1pm the sun was so low that it was about to slide behind the neighbours roof so it was all a bit hurried and I hoped that plonking the tripod on its white patio marks and levelling it up would be good enough to keep the sun more or less in track - which it did. Securely fixing the solar filter was followed by the usual farce of me trying to point the scope at the sun using its shadow and without looking at the sun. Eventually I got there and was pleased to find a small group of 3 sunspots. I had just a few moments to snap a photo off before the roofline started to eat into the solar disk.

As it looked like it might remain clear for the evening I covered the scope up and retired until the sun had set.
Venus started to become visible around 4 pm so hoping that the previous rather rough alignment was good enough I manually slewed around to find the bright planet. Using an 8mm ep revealed a nice crescent shape or about 2/3 illumination. The bright planet was ringed by a small amount of chromatic aberration and trying some coloured filters didn't seem to make that much difference. Like the sun, it quickly slipped behind the roofline, but it was nice to see it. I look forward to it rising higher and presenting more of a half illuminated shape in the coming days.

The moon had cleared the trees in the south east so I manually swung the scope over and switched the tracking rate on my Exos-2/Eq5 hybrid mount to lunar rate for some very pleasant early evening observing whilst it was high in the sky. As darkness fell, early this time of year I sketched the region around Mare Imbrium. The angle of the sun illuminated some of the lava lines very nicely and there seemed to be some radiating lines from a bright crater near the alpine valley this evening that I hadn't noticed before. It didn't look like that in my book so was probably a feature of that days illumination. I must get a decent lunar atlas. Plato was half illuminated and the sun was just tough some of the higher peaks on the terminator side.

It was time for supper so I covered the scope intending to return afterwards. Unfortunately some cloud had rolled in. After checking a bit later I called it a day, which was a bit of a shame as I had hoped to add some quadrantid meteors onto the nights list. Still it was a very pleasant opportunity to get out after so many weeks of rain.

Thanks. Looks like I'll start with 1kg, and work my way up to 2 kg and see how it goes.

There's probably just a bit of play in the altitude, if I don't do the bolt right up , to feel when I'm getting close.

Hi all.

I'm taking the opportunitybto tinker with my 12" flextube whilst it's cloudy and going to add a counterweight. Rather than mess about with the clutch nut, I wondered what a good approx weight to start with might be.

I would like to get the top heavy balance better than it is, but not too worried about perfection. Thinking of using some old dive trim weights and a weightbelt.

What approx weight are people using?

Nice details.

A quick setup before dinner enabled me to do some lunar observing. I came across s faint line which turns out to be the Ariadaeus Ceft that extends for about 120 km. 

lovely sketches.

On ‎11‎/‎11‎/‎2019 at 06:49, acr_astro said:

Hi,

an excellent start of lunar sketching! Especially in our fast moving times, lunar observerving and sketches might be treated by some people as outdated. But for me it's a great time to come down and relax. I hope that you've already got addicted to it and we'll see more of your sketches here soon!

Clear skies!

Achim

Many thanks for the encouragement. I found it a nice way to chill out (in literal sense too ). 

yes on Monday-Tuesday night after the moon had set. North of M38 and very very faint, just discernable with averted position using a 12" dob when it was nearly overhead. I double checked the location using Kstars and Stellarium and moved the scope around a bit to check it wasn't my mind playing tricks or a speck of dust somewhere. It was right where it was supposed to be.

A lovely clear 10 day old moon hung in the sky last night. I hadn't intended to go out but it seemed rude not to. I had a lovely lunar session scanning the terminator.
Clavius looked fantastic and so thought I would try and sketch something of what I saw as the frost settled around me.

wow. That's great. Chapeau, for going out there in the dark.

Messier Medley and a comet

An unexpected sky full of stars greeted me when I awok in the middle of the night. Checking the weather and stepping oputside, it looked like there were going to be several patches of clear skies for the rest of thr night. Quickly dressing and dragging the Dob' outside I managed to get set up as the streetlights turned off, so it was nice and dark.

It seemed strange to see Ursa Major rising in the East when I have been used to seeing it settle in the West. I had woken the familiy up in my preparations and they dutifully stepped out expecting a wonder of the night sky. They were not disappointed. M42 was spectacular this cold night (about 4c). The trapezium was clear in a darker area and the 'wings' spread right across the field of view of my 26mm eyepiece.

After they had returned to their slumbers I set about tonights business which was an observation of M1 and an attempt to track down C/2017 T2 Panstarrs.

M1 was first on the list to get my eyes practiced before comet hunting. Isnt go-to wonderful -straight there. A clear misty patch with a slight elongation. It looked better with the 15mm ep that gave it more contrast although I could not make out any structures apart from the overall shape. I remember how I had struggled to locate this with my little refractor star hopping last year.

The Panstarrs comet was next. I had already looked up its expected co-ordinates for this time and entered them into 'user object #1' noting that it was near M38 and some other nearby star patterns. Slewing to M38 I heard a clonk from the scope tube and M38 was right at the edge of the field. I hadnt done the dec bolt up fully secure and so the tube had settled slighthly in the mount - doh. After re-alighning using the sync-encoders function on Pollux which had been one of my alignment stars I started again. Fortunatley I did not have to hunt about after recalling user-object #1, a very faint misty ball was present as I scoured the field of view. Checking my notes of nearby stars it was in exactly the right place. Hooray. 
I pulled up my scarf, settled onto my stool and stared into the blackness trying to get as much accommodation and light as possible. The fuzz drifted in and out of visibility and just maybe I could see some elongation - or was it my mind playing tricks? I didnt feel like getting the camera out this evening to probe further with a time exposure. Seeing was good enough tonight and I would leave that to a few weeks time when it should be a bit brighter.

The sky was still gorgeously clear and having located my goal it was play-time with a cluster hunt.

M79 and M93 were too low and below the fence.
M46 47 48 and 50 were more fruitful. M47 had a nice V shape within its varying magniture open cluster of stars.
M41 filled the field nicely and included a few orange stars.
M74 was quite small and looked like a couple of stars within a misty patch. Probably better with a time exposure.
M36 36 37 and 38 (again) followed. I hadnt noticed the bright star in the middle of M37 before so that was nice.

Finally, it was nearly time for the street lights to come on so I finished with Caroline's Cluster NGC 2360. Named after Caroline Herschel who discovered it.

A very pleasurable night out, after so much rain, and a chance to practice some sketching.

Its the eyepieces I have problems with and have to tuck the binos inside my coat or under a warm hat from time to time.
Sometimes I wondering if Im breathing out through my eyes. Maybe I should try a swimmers snorkel ?

A friend tipped me off that some clear skies were advancing in my direction so at 7pm I ventured out with the big 12" Dob' for its second outing since buying it second hand a few weeks ago.

The 12 dob just fits through the door frame and settles nicely on a concrete patch in the patio and on went the tube. I used a laser collimater to align the scope having attempted to collimate the collimater earlier in the week (it was way off). Connected up the battery and started to align. The sky was looking very grey with the rising moon, streetlights and damp in the air from rain during the day so I wasn't sure what I would be able to see and as this was an unexpected outing I hadn't prepared any particular targets to vue either. 😕

For some reason the suggested alignment stars always seem to below the fence or behind a house. I settled on Altair and Mizar. Mizar making a nice double to start the evening.

Taking my tour around anticlockwise to start with I slewed to M13 as a nice easy target. The cluster showed up clearly against the grey sky with a 15mm EP and a number of outlying stars could be resolved, the centre starting to look a little grainy

The next target was M57, the ring nebula. This landed in the right half of my 25mm EP fov so I guess my alignment was a bit hurried. The ring was unmistakeable and it was nice to be able to look at it directly and then see even more with averted vision. My CLS filter and the 15mm ep helped to subdue a bit of the grey background.

Then came M27, the dumbell nebula, which was also nearly overhead. Ive seen it clearer than this night, but it was again an obvious misty patch looking a slightly rectangular in shape. The CLS filter helping a little bit to subdue the background again.

At this point I noticed that my stars were looking a little astigmatic so I checked the collimation. I dont know if the scope had just settled a bit or I had jogged the flextube, but it wasnt quite right. I also noticed that the standard skywatcher EP adapter tilted the collimater when the screws were tightened. Returning indoors for a rummage in a box of bits, I returned with a Baader 2"-1.25" adapter and the collimater sat nice and squarely in it. The collimation needed a slight adjustment and was rewarded by some nice dark circles right in the middle of any out of focus star images.

The moon was now advancing and blanking out most of the sky so I switched to some star clusters.

M103 came first which revealed its lovely triangular shape with the red giant star showing clearly near the centre

M29 came next, slewing back over towards the west now away from the moon, which is a new addition to my Messier collection. The small triangle and rectangle were quite clear and reminded me of the Pleaides (which were still behind the tree near the moon).

M39 was another addition to my Messier collection and appeared as a rather loose collection of stars. In spite of the large number of stars in this region the open cluster was clearly a cluster of stars although I couldn't pick out any memorable shapes.

M34 was the final cluster of the night. The cluster was clearly visible in a 25mm EP even though the moon was now quite high. The drop in temperature seemed to have cleared some of the mistyness from the air - and deposited the water all over my scope.

To close the evening I toured the western edge of the moon. This is an area I haven't explored in much detail and there were a number of significant craters with central peaks casting long shadows onto the walls. I must learn what some of these are. The air must have steadied since I was able to use an 8mm EP on the 1500mm fl dob to get some nice close-in views.

The dew was falling heavily by 11pm, my secondary had started to mist up and thin cloud was drifting back across the sky so I called it a night. A very pleasant and un-expect night out and all tucked up by midnight.

I must get my pencils and pad ready next time for some sketches.

PS - loving the posts on here for some great ideas of things to look at.

Thank you for the detailed explanation.
I found the metal bits affect the compass, so Ill have to mark the fence where north is and put a little sight on the tube when using it at home.
Im in the process of making a small platform with adjustable feet to get the base level.

I wondered that, but a 12 inch dob at F/5 will have approx. 1500mm focal length and a Fov of around 1 deg with 30mm ep.
Then I thought maybe if the base wasn't exactly level there could be elevation errors between the alignment points as the axis of rotation might be in slightly different places.

Maybe im just thinking too hard 🙂
I was just surprised it didn't come up in the menu and yet PE correction is.

I'm a bit puzzled why the ALT-AZ handset configuration on a SW Dobsonian go-to only offers 2 star alignment, yet the EQ mount versions offers both a 2 and a 3 star alignment.
Isn't the 3 star more accurate - so why not on the ALT-AZ mount (Dobsonian) aswell ?

Which then makes me think - how accurate does the levelling on the Dob mount need to be?
Puzzled.

Hi,
I have a 105mm refractor that I put on an old Exos2 with a skywatcher EQ5 motorset fitted to it and I use an old Sony NEX5 (APSC sized)
Im very happy with getting 45 second exposures through the 600mm focal length scope just using this  motorset unguided with ISO 800 and RAW format.
I use a Bahtinov mask to get a good focus on a bright star near my subject and spend some time balancing the scope well and setting the polar alignment well.
To set the pictures I bought a cheap intervalometer and set it to do 20 pictures of 45 seconds with the camera set to bulb mode with 15s gap to allow the camera to write the file, 5s preview and get ready for the next picture.
I use the preview just to check all is well from time to time - just my looking - don't touch.
At the end of the 20 frames I check the weather and the last frame and can set another sequence off . 

To stack the frames I take the card out the camera and put it in the PC stack directly on the card using DSS  rather than transfer many Gb of data onto the Pc hard drive.
When Im done I just save the stacks (both with adjustment applied and without adjustment applied) - I don't usually save the initial 'lights' due to lack of hard drive space.

My secondary dewed up so thought Id try and insulate it.
If this doesn't work I'll add a resistor matrix over the top.
 

Basically its a layer of old diving sock neoprene cut to lay over the top of the secondary and the support has a piece of shaped 22mm plumbing insulation wrapped around it with some neoprene tape to hold it all in place. I cut the pieces based upon a paper template and took care not to add any pressure to the back of the glass or obstruct the light path. The neoprene is just resting on top - no adhesive.

Clear skies.
 

I thought about getting a printer for ages. Ive stuck with sending my stuff off to i.materialise or 3dhubs. It usually comes back within a couple of weeks. Theres a nice selection of different materials from standard PLA to more detailed and resilient mult jet fusion and laser sintered plastics. I don't have to find room for the printer, set up all the temperatures and add-ons,  maintain it and keep buying reels of PLA. 

Thanks for everyones comments. I took the plunge and took the opportunity to pick up a 3rd hand 12" flextube goto.

First light:
I set it up last night even though the weather was a bit iffy, aligned no problem and had a lovely view of M57 and Alberio before everything got dripping wet with dew.
Lovely to be able to stare directly at M57 to see it. The colours of Alberio were nice and clear. Vega (one of my alignment stars) was a dazzling light blue - lovely.

It isn't too heavy in the 2 parts - more slightly awkward to get the base through the door (tuck that az wire in).
Its very quiet - I was surprised.
Collimation (not done that before) was dead easy with the collimation laser ep that came with it.
The stock single speed focusser was ok and there wasn't much wobbling when in use, so Ill probably leave it as is for now. (I guess the weight helps here).
It was quicker to set up than my equatorial mount. Base down - tube in - extend tube - set horizontal and collimate - connect up battery - align - go.
Quite like the shove-to save time when changing from one side of the sky to the other.
At 185 cm tall, the ep is at a nice height too.
Well pleased.

It was so wet yesterday that the finder and secondary dewed up massively after about an hour so I will make up some simple dew heaters over the weekend.
Ill also be making up a stand to keep the base off the floor.
The existing particle board has swelled slightly near the base so I want to control that and will take the suggestion of silicone and some light PVA.

Thanks all, clear skies.

I do my darks with the camera off the rig when I start clearing down and when Im setting up so not to lose time and whilst its at the same sort of temperature as everything else.
Im experimenting with artificial flats at the moment as I got some very strange gradients earlier in the year no matter where I pointed the scope - sky/clouds/ fence/indoor wall - that were different to those on the lights.
So what I do now is to quickly stack the lights using DSS at 100% and manually weed out any with low scores then do a stretch in DSS, save the stretched TIFF file and load it into PaintShop. In PaintShop I clone out the brightest stars and the general area of interest if a bright nebula. Then I do a massive gaussian blur at 90 or 100 pixels and save the file as my 'flat'.
Then I either re-stack using my blurred image as a flat or take the original saved file and blend it with the blurred image (layer) using difference (Subtract) mode at 80-90% to remove the gradients. It can be quite severe so have to play about with the settings a bit, but saves me a load of time in taking flats with a screen etc. Its not perfect and had its downsides but in the limited time I have it usually works as 'good enough' for me. 
 

Hi - not considered that - thanks.
I was also thinking of something to go on small pavers that might sink over time or on a patch of concrete path. - hence levelling advice of some sort.