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!
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!
As you can work out, I am very new to this astrophotography thing – I am simply recording my journey on this blog!
So.……now I have discovered the power of even very simple processing in software like GIMP2 used below.
Original image of trees at bottom of my garden – QHY10 single shot colour camera on Sky Watcher Equinox Pro 80mm OTA taken with EZCAP_QT software and debayered (colour shown) using Deep Sky Stacker (below):
In the image below, the image above has had its curves tweaked in GIMP2:
In the next image, the image above has further been sharpened using unsharp mask in GIMP2 (OK – it is over-sharpened but it shows what can be done!):
Teleskop Express (https://www.teleskop-express.de/shop/index.php/language/en) produce a combined flip mirror-off axis guider & I think this is going to be perfect for the QHY10 camera.
I tried the combination tonight – and it works – with an extra extension on the 1.25 inch port (3x15mm in total but one needed on this device at least to act as eyepiece holder), the illuminated finder becomes parfocal with the camera and the pillar can be taken in to turn the device into a flip mirror for finding purposes or out to use as off axis guider.
So far only tried on the house beyond end of my garden – will need more in focus for focusing on the sky but the telescope has 2cm left do I hope this is enough!
Success! Colour image obtained with QHY10 camera. I made an aperture mask for the Sky Watcher Equinox Pro 80mm OTA to reduce light so that EZCAP_QT did not white out when the image was taken and then took the following FITS image:
As before, the image appears in black and white.
However, it turns out the is due to the need to select an appropriate Bayer matrix in astrophotography software – the following screenshot shows the above image appearing in colour when a particular generic Bayer matrix setting has been chosen. The pop box is obtained by clicking on “Raw/FITS DDP Settings” under <Options> in left hand menu options in Deep Sky Stacker (DSS) software:
Focus point on Equinox 80 to focus on trees/swing at bottom of our garden:
Pointed at window on distant house (curtains closed so no peeping but does have light behind it to give some contrast & help me to find focus point on Sky Watcher Equinox Pro 80mm telescope!).
I was surprised how long the exposures needed to be to get bright image – although less bright images could be manipulated in GIMP2 but using curves to bring out detail.
The size of the senor is large – three fourths (slightly larger than APS) giving enormous image compared to tiny sensors I have used in past, but clearly less sensitive than for example my QHY6 camera.
What I don’t understand tonight is that the images appear to be monochrome on a single shot colour camera – I can’t see setting in the software to make the images colour……I think I can sort this tomorrow by taking image during day when clearly colour around. Perhaps I am saving the images in wrong format or exposure not long enough to obtain colour data?
Tonight the focus point for the QHY10 camera on the Sky Watcher Equinox Pro 80mm with the nosepiece & Altair self centring 35mm extension tube that came with the camera & my own additional 50mm extension tube was 44mm on the Vernier scale on the Equinox’s focus tube – note this is likely to be slightly longer than will be needed for sky as the window below is closer than the sky which drives the focus point further out from the telescope.
Oringal image = 3896 x 2612 pixels, 10 second exposure using Nebulosity 4 software & selecting Nebulosity’s own in-built driver for QHY10 camera (below):
Above image cropped = this image looks like it has colour data but I think this might be artificial from my playing around with GIMP…..
The following image was taken using EZCAP_QT (recommended by QHY for this camera) – just under 4 seconds exposure with increased gain:
Image 2 – 60secs on Nebulosity 4 – as far as I can tell this is saved as B&W image:
“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.
No of Objects
No of Observations
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.
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.
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…
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.
Hang from washing line for painting – 2 coats minimum. Have a coffee between coats!
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…?