chiltonstar

Last night, the seeing here (Oxford) was excellent, some cloud though and some hazy cloud moving across from earlier con trails, but it looked like a good night for close doubles! I set up the 180 Mak on the SkyTee2 and headed for Pi Aquilae for starters. Beautifully split at x270 (10mm baader Ortho), with a shrap Airy disk and diffraction rings. Always an absolutely beautiful pair. On to Astronomy Now's doubles for September, starting with 1 Delphinii. This is a close pair, sep 0.9 arcsec, mags 6.20 and 8.02 and seemed quite a challenge. At x270, it is obviously a double and split, but much more obvious at x450 (6mm Ortho), and nicely resolved. Good to have an evening when x450 was possible and gave a sharp Airy disk and razor sharp diffraction rings. STF 2690 (also AN) is next door to 1 Del and an interesting one. Visibly at x270, it appears to be a wide double (17 arcsec), but at x450, the westerly star of the pair (B component I think?) was decidedly oblong. Both of the two components are in fact doubles apparently - a very close double-double for big scopes? I finished with Lambda Cygni - always a tricky little devil at the best of times (Mags 4.73, 6.26, sep 0.90, PA 358 degrees). At x270, it was visibly split with two apparent disks; at x450, more detail was visible with the secondary more like an egg shape on the diffraction ring. I've attached two simulations (Aberrator) of this double for the 180 Mak, one at lower mag and one at high mag which are very similar to the eyepiece view I had with the two Baader Orthos. Always a pleasure when the scope can be pushed to x450 (65x per inch) and still be sharp! Chris

I occasionally resort to music while observing, usually Tomas Luis da Vittoria or JSB. Chris

A good arrangement - you're circle cutting skills are obviously better than mine!. I use the setting circles on my EQ mount (Vixen SP), but to be honest, it's not that convenient with the 180 Mak due to lack of rings - I tend to end up in some very odd positions trying to observe, and for this reason, an Alt Az arrangement is easier (on the neck!). Once the az circle is set to true geographic north, it remains fixed and the calculation of current alt and az is done by Skysafari - so convenient, unlike EQ setting circles where the RA scale has to be adjusted all the time. I wanted an accuracy of <1 degree because of the limited FoV of the Mak, and this seems to work. Chris

Now posted in DIY forum, as requested! More details available if you need them, and the image of the 360 degree scale I used. Chris

Posted by request! After some rather annoying evenings using my normal star hopping method, frustrated because of the 70-80% cloud cover so I had very few reference points to start from, I decided to construct a simple Az setting circle, and add a Wixey inclinometer so that I could get accurate enough alt-az settings to get to the right part of the sky, even when partly clouded! The az scale was an image of a 360 degree protractor (using macro lens to retain linearity) enlarged to ca. 200mm diameter, printed on thin card and then laminated onto 1mm high-density waxed card (aka pizza base) and covered with plastic stick-on film. To get it to be relatively stiff to turn, I added a disk of high density foam on it to grip the 100mm non-rotating base of the Skytee. The pointer is a miniature laser pointer, with a disc of blue acetate over it to reduce the intensity. It is mounted on a small aluminium bracket to avoid fouling the slomo knob, and the angle can be adjusted up or down to centre on a larger or smaller scale. It is fastened to the Skytee on a flat surface using velcro. Alt uses a normal Wixey with a magnetic base, clamped in the top mounting position on a ferromagnetic plate. Modus operandi: level base, find a star somewhere in the right area of sky and centre on it. Zero the Wixey on a level surface and clamp it in position. Using Skysafari (settings adjusted to horizon coordinates, ie alt-az) read the az value and set the scale to that by rotation. Loosen the mount clamp for the top mount and move the Wixey and clamp in the alt axis until it reads the right value for the star (again, from SkySafari) and clamp. Then just "push-to" the right coordinates for the target! Accuracy and repeatability? I've managed to use it twice so far (alas, the climate), both times finding Neptune in a partly clouded sky, once using the Moon to set up and the second time using Vega. On both occasions, Neptune was in the finder view (9x50 RACI) about 0.5 degrees from the centre. To increase the readability of the az scale, I'm working on printing out a large enough disc to lay on the ground, just outside the tripod legs. Some pics below....

...ah yes, of course! Always a bit difficult to get one's head around the view and timings from the Southern Hemisphere. Chris

....and a Europa transit if I'm not mistaken! Too low for us near the North Pole but you might see it Geoff? Chris

Nothing very original or sophisticated, but effective. I'll take some pics and post it in the DIY forum. Chris

I caught a glimpse before Jupiter set in the trees - the seeing here was poor to average, but high cloud made things difficult. Saturn seemed to come with a cloud attached last night which tracked it for some time - very annoying. I tried out my DIY azimuth circle for the Skytee2 mount and Wixey to find Neptune which was in a clearer patch of sky. Straight to it within 0.5 degrees - a very nice view, although too much background haze and Moon to have a chance at Triton though. Chris

My starting EP with my 180 Mak is a 40mm Plossl; the field of view is limited, but it works well when looking for DSOs which fit within the field of view. I have a 56mm Meade as well, which is good for showing objects like fainter galaxies, but there some optical issues. As stated above though, the 180 Mak is primarily a planetary/double star/lunar scope, for which it excels! The views last night of Saturn at x350 were amazing. Chris

I would say I've found it a lot easier with my 180 Mak than with my smaller scopes. I've not imaged it with the 180 Mak yet, but a simulation for different apertures shows how much better it is resolved at 180mm aperture - this closely matches the visual impression. Chris

I imagine OOUK might well be prepared to do a production run of 8" f8 tubes if they thought there was a market - for example ten of us signing up to put in an order??? Chris

Great Stuff Stu! What a fantastic scope by the sound of it! I've certainly split it with my 127 mak (true aperture 119mm) - smaller than this the secondary will merge with the diff ring of the primary I imagine, but maybe still visible in nights of exceptional seeing. This is a stacked image of Zeta Her with my 127 Mak, together with a simulation using Aberrator for 119mm aperture:- Chris

I have my 180 mak on mine usually, or my 102mm f13 frac (Vixen objective) which is a beast to mount and needs something fairly "industrial" to mount it on. It is worth adding that the second mounting position (top) on the SkyTee is for lightweight scopes only such as a small frac - I put my ED80 on it, eg below:- Chris

How big? Chris

It's the technique I use for fainter secondaries of doubles, and for moons eg of Uranus. I suspect that now I've seen Enceladus, it will be easier to spot in the future - bit like Sirius B! Chris

I have been looking for Enceladus all through this Saturn season, without success until now! Last night, the conditions were right, Saturn was beautifully clear, Cassini razor sharp and the relatively good transparency reduced the haze around the planet and made the colours of the disk much richer creamy-orange. Also, Enceladus (mag 12.3) was due W of Saturn in a favourable spot. Moving Saturn out of the field to the E with the SkyTee2 slomo knob, and then allowing it to drift back into the field of view showed Dione (mag 10.9) first as a bright pinpoint, then shortly after and just before Saturn itself appeared, the fainter little point of light of Enceladus itself. It was bright enough to be direct vision, although with Saturn in the field of view, it wasn't visible even with averted vision. I repeated this a few times before going on to look for as many other moons as I could see. The scope was my 180 Mak, EP a 10mm Baader Ortho (x270), with the ADC in place. SkySafari screenshot adjusted to match the eyepiece view (laterally reversed). Chris

When conditions are excellent, the view can be stunning as you clearly found! Although these light, humid and hazy evenings are not to everyone's taste, they do bring out the best in Saturn and Jupiter don't they? Chris

Something to look forward to, Deo volente....... Chris

I caught it for 15 mins between patchy cloud and rain which was moving across., using my grab 'n go (127 Mak, 8-24mm zoom and Vixen Porta2 mount). The GRS was very clear and well defined, with Io intermittently visible above the GRS and the sharpish shadow close to the edge of the disk. Unfortunately as Jupiter started to set behind some pines, the seeing went to some extent so I headed back inside. Well worth the look though! Chris

Simply amazing images, as ever! Are the sites you go to chosen for their seeing (if so, how do you select), or simply stunning places you like going to? What a beautiful object Jupiter is.... Chris

For the first time, I saw a blood red Jupiter last night - two combines were working a few hundred metres S of me, and producing a huge cloud of dust. Powdered wheat doesn't seem to work as well as thin cloud though for improving seeing.... Chris

Ed's point about focus is a good one - the secondary is on or close to the first diffraction ring of the primary and if the scope is even a tiny bit out of focus, the secondary just becomes a "brightening" of the diffraction ring to me rather than a pinpoint. With my 180 and 127 Maks I split it fairly easily in good conditions, but it takes a bit of a wiggle with the Baader helical focuser to get it dead right. Chris

I just caught it - quite a sight as ever! Many thanks for the heads-up. Monday July 29th at ca.23:00 should be nice - Io plus shadow, and GRS all transiting together, with Jupiter at 13 degrees up (Oxford). Chris

With my ED80 (80/600) the best views are with a 3.7mm eyepiece or 5mm. Chris