Equipment for Astronomy

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!

Photos through Cheshire sight tube and Catseye collimators after Lee has collimated Orion 10″ Dobsonian telescope

The photos below are through my Cheshire colliminating eyepiece sight tube and through Catseye collimators today – latter are 2 x 2″ collimators, one of which at least is a Blackcat collimator. Lee collimated the scope for me on Friday night and I thought it would be useful to keep a record of what the reflections seen through the sight tube should look like when the scope is properly collimated, to help me with my own attempts at collimation in the future.

The wrinkly edge at one side of view is the top of my sofa!

This post follows from the previous one regarding Lee’s collimation on Friday night:

Lee collimates my Orion UK 10″ Dobsonian Telescope

Andy

View through Cheshire sight tube:

View through Catseye collimators:

Lee collimates my Orion UK 10″ Dobsonian Telescope

I really need to learn how to collimate my telescopes well – I had today off work and spent several hours attempting to collimate the 10″ Orion UK Dobsonian Telescope…..but Lee demonstrated how much better it could be done.

Andy

   

View down Cheshire eyepiece sight tube after Lee collimated the telescope:

See also the following post which has better photos of view through the Cheshire post collimation today:

Photos through Cheshire sight tube after Lee has collimated Orion 10″ Dobsonian telescope

Making a video eyepiece using Phil Dyer astronomy-modified camera

Next stage of my video eyepiece construction completed today, ready for testing hopefully tomorrow evening which is predicted to be clear.

Andy

 

In the first photo, the components are connected and working. In the second photo, I have assembled everything into single unit. The photo below shows the video eyepiece with lens on it rather than 1.25 inch telescope adapter.

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!

First light Orion Premium Linear Binoviewer with Orion UK Dobsonian 10 in telescope 20/3/19

First light last night with my new Orion Premium Linear Binoviewer used on my Orion 10 inch Dobsonian telescope. What excited me about his binoviewer when I got it was that it claimed not to need any in focus – an issue that has meant other binoviewers I have tried only work if a Barlow lens is also used which means they only work at high magnifications. The whole point (in my view) of using Dobsonian telescopes are the immersive wide angle views – and you need the wide angle at least initially with an object to find it in a Dob when you are star hopping!

Great news! The Orion (USA) Premium Linear Binoviewer does come to focus in my Orion UK (different company) 10 inch Dobsonian. In fact I needed to use a 35mm extension tube – although that is common too with eyepieces in this scope so does not imply that the binoviewer increases out focus. So I think the manufacturer’s claim that no extra in focus is required seems to be supported on this test.

I had more of a problem bringing images of the Moon and a couple of stars together with my two eyes in the binoviewer – I put this down to lack of experience. There were times when the Moon images did come together and then suddenly the Moon would be significantly brighter.

Mind you, I am being a bit unfair on the binoviewer here. Due to the Moon being located awkwardly behind a tree, I had to place the scope in an awkward position to get a view and my own body was somewhat awkwardly positioned too – so that it wasn’t easy to view properly through the binoviewer.

Andy

Orion Premium Linear Binoviewer

My best purchase from the Practical Astronomy Show. These binoviewers differ from other makes in that they do not require any extra in-focus. You never see these on sale….but this one was around £100 off new price! I have tried binoviewers before but the need to use a Barlow lens in order to obtain focus on my Newtonian telescopes has meant that they weren’t very practical. I decent read a review in one of the astronomy magazine about this binoviewers and the reviewer was so impressed he bought one!

I tried it today on my Orion 10″ Dobsonian telescope. In order to get focus, I had to use an extension tube plus my Tele Vue Paracorr – the latter has a long tube and I can pull it out quite a distance to act as an extension tube. All of this suggests that I will easily obtain focus on the night sky.

At the Practical Astronomy Show I purchased a pair of discounted APM ultra flat field 18mm 65 AFOV eyepiece and I already had a pair on Tele Vue Nagler 7mm eyepiece.

The view of the trees at the bottom of the garden was amazing! This the first time I have ever had a proper binocular view through a telescope without any sense of strain on my eyes! Both pairs of eyepiece worked well. I can’t wait to get out under the night sky. Only problem is this could work out really expensive on eyepiece with my having to buy a second one to accompany some of those I already have…..

Andy

  

Always worth having a bag of eyepiece caps so if you see any being sold cheap I recommend you purchase some spares in 1.25 inch and 2 inch varieties for both ends of the eyepiece. Below is my bag – the cheap 18mm eyepiece did not come with caps so good job I had some spare.

The attachments I used to obtain focus – this was opposite of in focus = out focus – as I was focusing on the trees at the bottom of my garden which are closer than infinity.

The Tele Vue Paracorr is one of my best ever purchases – so useful!