Dobsonian Telescopes

Aperture Mask: Yes. Pluto: Not so much.

Got home from the trustees meeting last night to a glorious clear sky. On a Monday? Really?

I made an aperture mask for my dob over the weekend and was itching to try it out. The idea behind the mask is that on bright targets cutting out a bit of light and diffraction from the secondary struts should improve clarity, even though the aperture is reduced (350 to 160 in this instance).

And so after failing to resist temptation I was setup by 11:20:

Jupiter: Disappeared behind neighbors house. Need to catch it in the gap between house and apple tree 1.

Saturn: Seeing dreadful without mask: boiling away with no clarity at all. With the mask: same but dimmer. Hmmm.

Pluto: Spent ages looking for this. Definitely in the right place. Pluto formed a triangle asterism with two other faint stars. I upped the magnification to dim the sky glow and there was definitely something there. Wobbled the scope – that helped. Averted vision- didn’t make much difference. So- I’ve looked at Pluto but not seen it! Beginning to regret doing this on a work night…

Jupiter again. Behind apple tree 1. That moved quick! Damn!

Izar: At last- some success. Successively improved views moving from Baader zoom to binoviewers to adding aperture mask. In the final view the stars were pinpoint sharp and well separated with the companion showing a lovely blue.

Double double: the same experience. The 2 pairs were easily separated in all 3 configurations, but the binoviewers plus aperture mask gave the best view.

M13: Too dim for the mask, the best view was in the binoviewers- resolving all the way to the core and seemingly spherical, even though at that distance you don’t really have depth perception!

Jupiter again: Gotcha! Just before it snuck behind apple tree 2… Definitely a better view with the aperture mask- slightly dimmer but with much more clarity. 6 bands plus the GRS were clearly visible, with some detailing on the bands, plus the moons spread out as clear disks 3 to one side and one on the other.

Well worth the fatigue today!

Very pleased with the aperture mask- it’s not often an astro upgrade is almost free. It’s only really good for bright objects and with the binoviewers I had to velcro 4kgs onto the bottom of the tube to balance it- bit well worth the hassle!

Fading Noctilucent Clouds

Popped out for a quick session on Friday night and there was a lovely Noctilucent Cloud formation to the North, so I popped my camera on a tripod and recorded it.

The video above was using a Canon SL1 at 22mm f4 taking 265 shots between 23:49 and 00:30. I used Pixinsight for a curves tweak and some unsharp masking and then Videopad to string it all together and add a bit of music.

The red light in the foreground for part of it is me setting up the dob. It doesn’t really add to the ambience- but it led a pretty good session despite needing to do a bit of cloud dodging. Finally got the Binoviewers dialled in for some good views of the Double Double, Izar, Albireo, M29 and M57. Really surprised that at similar magnification they outperformed my 7mm Celestorn X-Cel Eyepiece- the split on Izar was really clear, and the companion was a vivid blue, wheras the Celestron had them fuzzier and less colourful. Even Saturn came out to play- and despite hugging the horizon, the seeing gave me glimpses of the Cassini division plus Titan, Rhea, Dione and Enceladus. Best of all was M13- it resolved close to the core, but with tails everywhere- it looked like a ball of wool after a kitten’s been at it!

A Year of Observing

“You’re writing a blog about a spreadsheet???” My wife has just discovered that not only have I adopted the habit over the last couple of years of sitting in the garden on clear dark nights and then making notes about it, but I’ve then been putting it into a spreadsheet and getting statistics about it. And now I’m sharing it in public. She’s giggling at me with what I hope is affection…

Last year I bought a 14 inch dob and after a few months enjoying the views and wandering through the skies I decided I wanted to be a bit more rigorous and start planning my sessions, so I started making notes on my phone of what I wanted to look at after reading observing reports on the web. I quickly moved onto recording the success or otherwise of these observations on a black notepad on my phone (to minimise disruption to my dark adjustment, although to be honest, in Bortle 5 skies it doesn’t make a huge difference), and it was a short step from there to Excel. I just spotted I’ve been doing this for around a year so I thought I’d share it, partly out of curiosity to see how it compares with others experiences…

Stating the obvious: we get quite a lot of cloud.

If it’s clear, I’m not doing family stuff and work’s not in the way then I’ll go out and observe. Altogether I’ve recorded 26 sessions. I’m pretty sure there have been more than that- if I’m observing in company I’m much less diligent about recording it. I also sometimes have quick sessions with my 8 inch for half an hour and I’m a bit rubbish about recording those too. So: 26 is roughly the number of ‘proper’ sessions where I’ve sat outside with a target list and written it down. From this I reckon twice a month is a good working average for how often I can do a ‘good’ session.

Objects:

No of Objects 149
Messiers 65
No of Observations 280

If I was a bit disappointed to realise how infrequent observing sessions are, I was quite surprised by how many objects I’ve managed to record during that period- including quite a good chunk of the Messier catalogue. I suspect I’ve managed to get through most of the easier ones. From my location, although my southern horizon goes down to a few degrees in places, I’m looking directly over rooftops and at the dome of light pollution of Burton on Trent and often the orange haze makes finding reference stars to hop from very difficult, so I’ll probably need to make more effort to get to dark sites to grow this list a bit.

Favourites

I wasn’t surprised to find that there are some objects I come back to again and again, but I was quite surprised to find the Leo triplet at the top of the list, although on 3 of those occasions I couldn’t find NGC3628. M13 is less of a surprise, I never get tired of looking at it and trying to resolve as far as possible into the core. I notice that over time I’ve been less inclined towards the higher magnifications. The Double Double is a favourite first port of call, both because it tells me how good the seeing is, and also whether my mirror has cooled. Plus, I love the idea of it as a vast interstellar executive toy- with six components that we can’t see. I’m sure M42 would have overtaken all of these if it were visible for more of the year and not so subject to winter weather.

Failure…

Something I’ve not done much of is logging how often I can’t find or see things. The Horsehead is conspicuous by its absence (I picked up an H-Beta filter in March, but just missed out on the HH) and I really want to see Stephan’s Quintet visually- this will need darker skies! I suspect that if I was logging more diligently the times I’ve failed to find either of those targets they’d be quite high up on the list and I’m going to start doing that. I’m also going to record a bit more about where I observe (usually my back garden) and what equipment used.

I’ve attached the spreadsheet I’ve used in case anyone wants to re-use the format- it’s pretty basic and has just sort of grown organically as I’ve added bits and pieces to it. It’s a bit of effort to keep it up to date, but I’m glad I did it as it’s been interesting to look back over it and remind myself of what I’ve seen- It’s also a reminder of how great visual astronomy can be when you’re suffering the frustration of several weeks of cloud cover.

I’m going to brush over the slightly worrying and repeated experience, of reading about targets, thinking they sound great, then finding I’ve already seen them…

Log 18-19

 

DIY Dob Mount for SW 200P

After hearing about the rapid set up and simplicity of a Dobsonian mount for casual observing, I thought I would investigate how to get one as an alternative to my EQ5. Strange that these mounts cannot be bought separately, except at Orion Optics UK, where I was quoted a high price. This set me on the DIY route.

I decided that I wanted the capability to adjust the tube axially (for balancing) and rotationally (for comfotable viewing position), as with the EQ5.I also wanted easy transfer of the tube between Dob and EQ5 (no tools needed). After a week of research, I settled for a hybrid that included a features from this article: http://www.scopemaking.net/dobson/dobson.htm, The Sky at Night articles in Dec 2014 and Jan 2015 and the Orion Optics design. Originally, I was going to design the rings and dovetail bar to be interchangeable, but when a set became available I settled on a separate ring set for each mount.

I won’t go into detail about the build/assembly but show various stages in pictures. The main stages are; 1.mods to the ring set, 2.cutting, shaping and painting, 3.bearings and the 4.optional brake. Anyone who wants more detail please contact me.

1. Modify ring/rails assembly.

Trunions: PVC 160mm pipe plugs (Buildbase, Newhall, Swadlincote). Protect bearing surface with masking tape. Locate centre and fix to bar with 1/4″UNC fasteners (Pugh & Sanders Ltd Burton on Trent).

Shape and fit 2nd ‘rail’ from 10mm plywood. Fix to rings with 1/4″ csk head screws. Locate trunion on centreline in same position exactly as other trunion.

 Trial fit completed ring/rail assembly to scope

2.Cutting, shaping and painting frame

I used 18mm mdf for the base and sides and 10mm plywood for the front, back, rail and accessory tray. Use plastic fixing blocks and screws to hold everything together. No adhesive needed. Take basic dimensions from the article referenced above, except width of front and back, noting that alt bearing box is not needed and friction brake needs to be included.

Mark out parts using trammel to draw circular base.

Cut with jigsaw and smooth with rasp and glasspaper

To obtain width of front and back, measure distance between trunion flanges and add 10mm.

Use plastic fixing blocks to assemble, drill through upper base and screw to frame, bolt to lower base, trial-fit scope assembly. If all goes pear shaped, use as a ‘lazy-susan’ coffee table!

Trial fit 3 feet 120° apart.

Use jigsaw and ripsaw to cut holes to reduce weight and improve appearance.

Smooth all edges with rasp and coarse glasspaper, particularly the upper curve of the front cut-out to be used for carrying

Hang from washing line for painting – 2 coats minimum. Have a coffee between coats!

3. Bearings

For altitude bearing use two 2mm thick ptfe sheets, drilled and countersunk in centre for small csk head screw.

 

 

 

 

 

For azimuth bearing use 3 Magic Glides (Wickes) spaced 120° apart within 300mm circle .

Use M10x60mm carriage or ordinary bolt and M10 Tee Nut (Amazon or ebay) inserted upside down for pivot in lower base. Tighten so it will not fall out or turn when M10 Nyloc nut is tightened.

 

For upper bearing use 12″ vinyl record (grooves make for low friction). To form a good bearing for the bolt in the upper base use a brass10-15mm reducer plumbing fitting (Wickes) drilled out to 10mm. Secure bases with oversize washer, spring washer and M10 Nyloc nut. Tighten only enough to take up slack.

Small spacers are needed to prevent sideways movement of scope assembly. Spacers are squares of ptfe fastened with small screw and spring washer fitted between side and flange of trunion. Trial fit to to gauge the spacer size and position of spacers.

 

4, Friction Brake Feature – Optional

This feature prevents the scope moving if the assembly becomes out of balance, although there is the option to slide the tube axially.

Attach another strip of ptfe to top of curved section of brake. Attach small hinges between brake and side using small 90° brackets to allow screwing into face of wood – mdf will split if screwed into edge! Attach a ‘Brighton sash window catch’ (satin chrome finish from Screwfix) such that it can be released to allow the scope to be lowered into place and tightened to stop movement or lock the scope.   Fit accessory tray to front and hooks to sides for clipboard, glasses etc. Extension legs can be used if elevation is low or if the ground is long wet grass. To make carrying more comfortable, fit a length of 12mm soft clear plastic hose cut lengthways to upper curve of the front.

I had great fun making this but have used it only briefly to observe the Moon and was pleased the way it moved…but I still like the fine control provided by my EQ5 control cables. Now how can I add this feature to the Dob…?

Moon, Methane and Messiers

Splendid night of observing and (hopefully) imaging last night.

Sam had his mate James round, and then Andy T came over to join us as well. Due to the long evening twilight and the terminator being in a prime position on the moon, we started there. Once they’d got the hang of it the 2 lads were thoroughly enjoying scanning up and down the terminator taking videos of moonscapes, which when I get some time will hopefully become some nice images.

The areas we looked at were the craters around the South Pole (Scott and Amundsen!) then worked our way down (the image appeared upside down in the mark/planetary camera) past Cuvier, Stofler, Albertegnius and Hipparchus toward the smoother area that’s more dominated by mare. The highlight for me was Albertegnius which was just in the perfect position to be in complete darkness, but with the sun illuminating just the summit of the central peak.

By this time Andy had set up his spectroscopy rig and took a reading from the moon- and matched in to an internet reading of the sun- explaining to the lads that this was because all the light coming from the moon was reflected from the sun, and how the technique enables us to derive what the elements are in the star.

We also did some visual exploration of the terminator- and no matter how amazing the views of the moon through the planetary camera, there is nothing for comes close to the stunning HD quality through the eyepiece. Even at 465x through the zoom the view was sharp and full of contrast; a really stunning view.

It was, by this time, bed o’clock for the boys, but Andy and I carried on. First step was swapping the mak for the 130pd-s and setting some imaging runs going on globular clusters with the planetary camera as I felt that the glare from the moon made any other targets a bit unrealistic. I’ll post these when I get the chance to do some processing!

For the same reasons I decided to go for similar targets visually whilst Andy did his spectroscopy and we shared the results with each other. First up, though, was the double-double- it didn’t split as easily as normal which suggested the seeing wasn’t great (I already knew my scope was both cooled and collimated). Nonetheless I pressed onto some globs:

– M13 Obvs! Always a lovely sight. Whilst there Andy moved the scope onto NGC 6207- a new one on me, and just next to M13. It was a struggle to see and needed averted vision to spot, but at Mag 11 the skies cannot have been too bad to pick this up.
– M92 It’s a bit smaller, but somehow feels more compact and symmetrical than its big brother.
– M3 Again- like M92, more compact and symmetrical. It was nice going through these one after the other- on their own globs are all similar, but when looking at them one after the other you really start to see the differences.
– As we were in the neighbourhood popped over to see the Whale galaxy- several club members have been imaging this lately so it was good to have a proper look. With proximity to the moon it was quite an effort to find this and I had it in the eyepiece for quite a while before I was sure I had it. By relaxing and just looking around the target it became obvious how huge it was- nearly filling the ep at 210x. I couldn’t make out the distinctive shape, however, and neither could we spot NGC4656
– Next stop as M5, which was visibly smaller, but with a dense bright core and was pleasingly circular.
– The next Messier glob easily visible looked to be M9. Whilst aiming the scope Andy asked about the bright light in the same direction- which is over towards East Mids airport- and we both agreed was clearly a plane- although not moving too much. Realising that this meant it was heading towards away from us I tried to aim the scope at it, because sometimes it’s a great view in the eyepiece. This plane turned out to have horizontal banding and 4 moons. JUPITER IS BACK!! Albeit hugging the horizon in a boiling atmosphere. Because of this the views were not brilliant, but it was great to see after a long break. Andy quickly headed back to his spectroscopy gear and lined it up- the result was a mixture of the same elements we’d found from the moon, plus a couple of lines for methane. Very pleasing! I then moved onto M9 and caught a quick glimpse, but was kneeling uncomfortably over the telescope by this stage and was getting decidedly cold so we decided to head in for a cup of tea in the warm and to look at Andy’s spectroscopy results.

Suitably refreshed, and with the moon down near the horizon the sky was darker, but also more hazy. We decided to look at some summer targets and started off with the Ring nebula. I think the effects of time and cold were beginning to set in by this stage as I struggled to get it in the eyepiece- not helped by the fact that everything was dewing over. Andy quickly rectified this and we were rewarded with some lovely rich views and spent some time comparing the views in the Baader zoom with Andy’s Binoviewers. The conclusion was that the binoviewers offered a different experience- more natural and pleasing to look at, but also there was some loss of detail. Partly this is caused by the higher magnification available to the Baader, but we also thought it may be down to the greater number of optical surfaces involved on the binoviewers. We returned to M13 to see if we’d find the same outcome- and it was pretty much the same; although the binoviewers rendered the glob as a sphere- a wonderful view.

I’d have liked to try them out on Jupiter, but by this point it was behind the neighbours house, so we returned to deep sky targets instead- trying for M51. Unfortunately, by this point, the sky was pretty hazy and despite being certain I had the dob in the right place, I could not see the galaxies. Spent a while trying to remove dew from EPs, finders etc, but it was pretty clear that the sky was lightening and it was time to pack up. Big thanks to Andy for coming over- observing in company and sharing ideas adds so much to an evening and the output from the spectroscopy was really interesting!

Galaxy Quest! Observing Report 25/3/19

A clear sky and a free evening coincide at last!

First up was setting up the 200p for an imaging run on M101 (still stacking!) and then a nice little session with Sam and the 8 inch Dob.

Betelgeuse was first up and discussing how if it was where the Sun was we’d be in it!
The Orion Nebula at 48x was a nice site, with the 4 brighter trapezium stars quite distinct.
We then moved onto the Double Cluster which filled the eyepiece at the same magnification- so many stars!
Finally we had a look at M65 and M66 in the Leo Triplet.

A bit of family time and then back out with the 14″ for a more serious session.

In Auriga- M36, M37 and M38 were a good place to start, they’re sliding off to the West now and in a better place for comfort and (from my location) light pollution and seeing. I was swapping between the 24mm Baader zoom and the 35mm Orion that came with the scope, and whilst the 35mm offered a better Field of View the 24mm had better contrast and brighter stars. It became clear during this time that whichever eyepiece I was using, the seeing was good and conditions were better than they’ve been for weeks.

Next up I returned to Leo and the triplet. As usual M65 & 66 were quite easy to see, but whilst the 35mm needed averted vision to see NGC3389, it was quite clear in the Baader zoom with direct vision and that eyepiece remained in the scope for the rest of the session. M105 and friends were quite clear and continued the evening’s theme of multiple galaxies in a single field of view.

And so- over to Virgo- starting at Vindemiatix and hopping up to M60, with M59 again in the same view. Whilst looking around and enjoying the pairing, with both galaxies showing a bit of shape, NGC 4638 popped out at me as well. With the conditions better than for weeks I then embarked on a wander through the wonders of Virgo that went well past bed o’clock but where the next object was rarely more than a Field of View away. From my notes:

M84 Bright Core, no Shape
M86 Bright with some shape
M88 Yeah! Bright, some shape
M89 Core very bright- but no shape
M90 Clear flat elipse; some shape with AV
M91 V faint- no shape
NGC4638 Quite easy to distinguish
NGC4564 Clearly seen
NGC4568 AV Only
NGC4477 Direct Vision
NGC4479 AV Only
NGC4473 Clearly seen with DV
NGC4458 AV Only
NGC4461 AV Only
NGC4435 Clear and distinct from other Eye
NGC4438 Clear and distinct from other Eye
NGC4388 Flat shape
NGC4413 V Faint but direct
NGC4402 Faint- AV only
NGC4476 Quite clear next to M87
NGC4478 Quite clear next to M87
NGC4486a Quite clear next to M87

Altogether that’s 30 galaxies observed in quite a small segment of sky. I was discussing with my wife afterwards my fascination with looking at these. In many ways they’re no spectacle at all- fuzzy patches of lighter sky, some of them little more than mottling against darkness. Yet when viewing them with the knowledge of what they are, of the vast eons across which this light has travelled, and of the journey we have been on as a species to reach our present knowledge plus the many open questions that remain about them they are, in the most literal sense, awesome. All this was combined with a little buzz of achievement- several times last year I tried to galaxy hop through Virgo to Markarian’s and always found myself losing track somewhere and returning to the start point. There were a few shaky moments last night but the feeling of accomplishment at the end was quite immense.

I spent today at a corporate event needing to look bright eyed and bushy tailed which required rather a lot of coffee. I’m not sure I was making much sense by the end, but it was well worth it!

Adding Sky Watcher finder scope style mounting shoes to Orion UK 10″ Dobsonian telescope

My trusty and well used Orion 10″ Dobsonian telescope does not have Sky Watcher style finder scope shoes – a nuisance as I would like to use a finder scope with it and also attach my heated laser finder device which has Sky Watcher style finder bracket.

So today out came the glue gun and I attached two finder shoes to the tube. If the glue gun turns off with time not to be strong enough then I will bolt them on but hopefully this won’t be needed as not much weight on them.

The other advantage of using the glue gun initially is that I can change position of the finder shoes if it turns out they are not in the best place in practice.

Andy

I chose a rather cold day to do this!

OK so in the next picture it looks a mess. However, once the glue has cooled I will then be able to tidy it up and I would rather put a bit more glue on so that my stuff does not fall off the scope, including my bargain from the Practical Astronomy Show – right angled 9×50 finder scope with illuminated eyepiece for only £45, which I bought especially to put on this scope!

 

Observing Report 12/12/18

Slightly strange conditions last night- the sky south and east was distinctly murky with very ropey seeing. This isn’t unusual as I live north and west of Burton, but it seemed to be especially exaggerated. List below was all in 14” dob:

Aldeberan and the Hyades– whilst checking the Finder and the Rigel were lined up properly I put Aldeberan in the EP. It’s too easy to forget the simple pleasure of putting a big fat red star with whopping diffraction spikes (yeah, I know- not everyone’s cup of tea) in the middle of your field of view. Spent a while wandering round the neighbouring star field. A lovely start and almost forgot I had a list to go through.

Comet 46p – A nice little hop from Epsilon Taurus, but still took a couple of attempts. The head was really clear; I spent ages trying to see the tail. Eventually, with the 35mm in, a bit of averted vision and wiggling the scope I could see some elongation of the head and a hint of the tail.

Pleiades – Because if you’re in the area with a low power eyepiece it’s rude not to.

Mars – shrinking after the summer, but some detail still visible at 206x including polar cap.

Neptune – very small, but the blue colour is so striking. Given the seeing so low in the sky I didn’t try to go past 206x

NGC 6543 – Cat’s eye nebula – lovely pleasing green, and decent disk at 206x

NGC 7023 – Iris Cluster and Nebula – I got to the cluster OK, and I think I found some nebulosity but it was very faint. Not really sure.

NGC6946 – Fireworks Galaxy – Very faint and averted vision only.

NGC7331 and Stephan’s Quintet (NGC7320) – I’ve wanted to have a go at this one for a while, and with it high in a good part of the sky it seemed like a good chance. NGC7331 was straightforward- with an elongated shape clearly visible with direct vision. At low power (47x) it was easy to put it in same the FOV as Stephan’s Quintet. The four stars that they sit within were a distinctive shape and easily picked out. I think when you know what something is supposed to look like it’s easy to imagine it right there. There could possibly, maybe, have been a sort of mottling in the right area with averted vision??? I don’t think I can really claim that.

M42 – Again- rude not to and wonderful as always. The seeing was bad around there, although there was a hint of the ‘E’ star in the trapezium. Spent a while playing with Oiii and UHC filters. The Oiii filter just gives a brilliant view of the cloud with so much texture.

Rosette Nebula – My first observation of this object. The central cluster was easily picked out and I could find some faint nebulosity, especially beneath and to the right of the cluster.

Really enjoyable evening, and hopefully have some subs of 46p to play with soon…

Observing Report- 17/11/18

Sam and I met up with Neil Wyatt on Saturday night for an excellent night’s observing and imaging at Brankley Pastures near Barton under Needwood.

Neil was already setting up his imaging rig when we arrived at 8pm, and Sam and I got our 8 inch dob out to get started quickly. Unfortunately we quickly found that it was a night of absent mindedness: I’d forgotten the trusses for the larger dob, Sam had left behind 5 of the 6 pages of his lunar observing plan and Neil didn’t have the memory card for his camera. I can see that if I’m going to do more of these trips a checklist is going to be essential…

The moon was high in the sky so we started off with doing planetary and lunar with Sam doing the finding:
– Mars- polar cap just about vsible but couldn’t see other surface features.
– Lunar- Copernicus, Tycho, Altai Scarp, Theophilus, Cyrillus, Catharina, and Clavius (just around the same time Roger was imaging it).

Unfortunately this was as far as the first page of the Lunar 100 log gave us. So next we tried for a few deep sky objects- looking at Vega, the Double double and the Pleiades. Neil also brought up the Pleiades in his ED66 and it definitely looked better it the little frac with wonderful contrast and sharpness. I then ran Sam home, which was a good opportunity to pick up some Hot Chocolate and Dob trusses!

On my return the sky was darkening with the setting moon and we switched to the 14inch for some more deep space stuff with views of M1 (faint), The Auriga Open Clusters M36 & M37, the Ring, Andromeda, M81/82 pair and the highlight of the night: M42. We switched between the dob and the ED66 and used various magnifications, eyepieces and filters. At 205x, without filters in the Dob we both managed to spot the 5th brightest star in the Trapezium. There is a serious risk of my getting stuck on this target all winter…

A really enjoyable evening, and a pleasure to observe in good company!

A note on the site: Brankley Pastures is a Staffs Wildlife Trust site near Barton- so quite convenient for many RAG members and where- at least in winter- it’s possible to observe with minimal risk of being disturbed. It’s not a completely dark site- there’s a significant patch of light pollution to the North (presumably from Tutbury), and another to the North East from Burton. But overhead the skies are much darker than home and there is a great southern horizon. It was brilliant, as the moon set, to see the sky come alive- with Auriga turning from an empty circle to one rich with naked eye detail. Just next time I need to remember all the key parts of my kit!