Nik271

This has been my experience too, the Pup appears briefly next to the glare of Sirus in moments of good seeing. I managed to see it again last night - just a couple of brief glimpses during 20 mins of looking. My problem is that there are many of houses and a road just south of my garden, so in winter the heat plumes from them create a mess at low altitude. Last night I split Eta Geminorum (Propus). The separation is 1.7'' , position is west of the primary and with big magnitude difference. (3.5 and 6.1). Used x300 with Skymax 180. This is one of Burnham's discoveries, so quite pleased to manage one more from his catalogue. The separation was smaller when Burnham discovered it in 1880s and keeps increasing. The orbit is somewhat uncertain, I've seen at least two different plots, with periods 400 years and 1000 years.

This chart seems to be based on the LAC series produced for USAF for the Apollo moon landings from observations and photographs. They have a very classic look similar to a geography atlas with altitude contours. In this age of satellite imagery they have a very different look. I like them a lot actually. They are available for free here: https://www.lpi.usra.edu/resources/mapcatalog/LAC/ I printed them out and bound them in an A3 atlas. A bit bulky for the observing session but wonderful to browse and plan on a rainy day.

Gruithuisen domes should be near the terminator. They look like a pair of white mushrooms 🙂 But you don't need great seeing to spot them. The rilles of Gassendi could be worth a look too in good seeing.

I spent most of the evenig on the Moon with my Skymax 180, the seeing started OK-ish and steadily improved, by 11pm it was fantastic. I spent ages trying to spot the central rille in the Alpine valley but can't say I got a conclusive observation, just hints of something on the valley floor. Part of the problem is that there are also shadows from the rim of the valley which confuse the eye. I was using x300 but maybe 7 inch aperture is not enough for this or the illumination was not favourable. By contrast the 4 large craterlets on Plato were 'easy'. Rima Hadley looked great, I could trace the north part which the curves towards one of the outcrops of Mons Hadley. By 11pm I was freezing but remembered Sirius, so had 30 mins looking at it. The lower elevation was a big difference, x300 was too much and I switched to x220. Sirius looked good at this magnification with well defined airy rings. The Pup was showing intermittently, if I didn't know where to look I would not have spotted it . Let's hope the fog stays away for the next few days as we finally have a good calm high pressure air system overhead!

Transparency was very good last night but seeing went downhill after 9pm, I had the big Mak out looking first at the Moon, then planning for some close doubles, but gave up. At one point I had trouble splitting even Rigel which was dancing all over the place. So I took my 20x80 bins and had a pleasant half an hour scan of the low southern clusters. M41 looked very good, normally I don't get to see it well because of the low altitude and city glow. M47 was sparkling, flanked by two red giants and I could even spot nearby M46 and NGC 2423. I read that M46 has a planetary nebula, that is a nice project with the telescope for another day.

This area is definitely worth revisting aroung the 6-th day old Moon. Actually I forgot to look for another interesting feature nearby - the submerged crater Lamont. https://en.wikipedia.org/wiki/Lamont_(lunar_crater) It was in fact labelled on my map but I thought it referred to an actual crater. Another reason to return to it again for a careful study.

If you can adjust the distance of the barlow lense to the sensor you could convert it to 1.5x barlow, the closer it is to the sensor the less magnification factor.

I've been trying to complete the Lunar 100 (https://skyandtelescope.org/observing/the-lunar-100/) and one of the features that I was missing was the Arago domes. They are only 300 meters high volcanic domes near the crater Arago in the Sea of Tranquility, so only visible when close to the terminator. Last night the illumination was perfect and after a rain shower the clouds cleared around 8pm. I set up my Skymax 127 and pointed it at the Moon with a 12mm BST EP. Sure enough the domes are very prominent next to the Arago crater. The seeing was not great and the 12mm EP was already a bit too much but I spent 20 minutes scanning the areas near the terminator. Theophilus, Cyrillus and Catharina were the main attraction further south, whilte in the north I enjoyed a good view of Dorsa Smirnov and Posidonius crater. Beyond them to the north was Lacus Mortis with the crater Burg. Despite the poor seeing I could see some of the rilles in this basin, especially those oriented north south due to the shadows they were casting on their flloors. The moon libration was favourable for features on the easter limb: I could see well into Mare Humboldtianum, Mare Marginis and Mare Smythii and even parts of Mare Australe on the south eastern limb. So overall pretty good session for lunar observing for me Clear skies!

This is the (long) thread I remember which discusses the issue of exit pupil, aperture and magnification when observing DSOs:

To observe faint DSO you need BOTH large exit pupil and some magnification, precisely how much magnification depending on the size of the object. Your APO with a 24mm EP will give you magnification of about 18 which is basically a binocular class magnification. WIth a wide field of view it is ideal for open clusters (Pleaides must look wonderful in it) and the large DSO: Andromeda and Triangulum galaxies, The Pinwheel galaxy M101, M42, the Veil nebula, North America nebula and so on. The sky brightness is very important as well: large exit pupil makes everything brighter including the sky background. So if you have significant light pollution large exit pupil does not help on its own. The same EP with the Mak on the other hand gives you about x60 magnification, much better for the smaller galaxies. 2mm exit pupil is actually sufficient to see them, personally I consider 2-3mm exit pupil the ideal for small DSO observing. I have observed many galaxies with my 127Mak e.g. M81,M82, M51 in Bortle 5 sky as well as many planetary nebulae. This is not to say that 4mm exit pupil is useless, not at all, one big advantage to it is that you can put narrowband filters to improve the contrast of some nebulae and still have bright image. The Veil nebula is a prime example where an OIII filter does a very good job with a 4mm exit pupil. I recenlty observed it with binoculars (20x80 so again giving 4mm exit pupil like your scope) with a filter inserted in the eyecup. I hope this helps. There is a lot of discussion of image brightness and exit pupil in some recent threads in the observing section.

You should try Tegmine (Zeta Cancri). The separation is 1.1'' and the two components are of equal brightness. A four inch scope in good seeing should be able to show the separation.

I managed to spot Dubhe's secondary this morning with my Skymax 180 at x450 magnification 🙂 Last night the seeing was OK but nothing special so I didn't even plan for anything difficult. In the morning however it was very still and a bit misty, a good sign. Luckily I didn't dismantle the scope last night, just capped and covered it on the mount with a BBQ cover and the corrector plate stayed dry and clear. Dubhe was quite high in the northern sky at 7am and it was still dark. This was as good a chance as ever so I went directly for the 6mm EP giving x450. The seeing was good, but not the best. The diffraction pattern of the orange primary was shimmering a bit, there were moments of stillness and in these I could see a faint bump on the first diffraction ring. I noted the position as north west and stayed at the scope for half an hour waiting in moments of clarity. The bump kept appearing and disappearing, always in the same position. It was also noticeable at x340 with the 8mm Starguider. I would not call this a clean split since I didn't see a well defined secondary airy disc, just a dim hump on the diffraction ring. I checked with stelle doppie and PA is 330 degrees which tallies with my observation. I'm very happy about this one, it was one of my 'bucket list' doubles. I'm very confident that in better seeing this double is doable with even smaller aperture. Not my 127 Mak perhaps but certainly a 5 inch refractor or above should show it. The separation is about 0.8'' and stays like this for several more years. Clear skies! Nik

Jupiter is quite low in the evening so it might be a case of bad seeing or heat plume from a nearby house. The best way to test the optics is to pick a bright star near the zenith when the stars are shining steadily (without any twinkling) and use your 9mm eyepiece. You should see the Airy disc like this one: ( well looking much smaller than this). If you see anything else then could indicate a problem with the scope or the eyepiece.

According to Wikipedia LaHire is 'arrowhead shaped': it seems that the smaller shadow is cast by the 'point of the arrow' on the valley next to it and the peaks on the other side are cathing the light. However in my observation I couldn't see two shadows just one continuous long one. This must be very time dependent - at these low sun angles even a few minutes may make a difference.

I had a brief clear spell at 7am this morning, grabbed the Skymax127 and set it up in 5 minutes outside. The last quarter moon was still high in the dark sky and I had pleasant 20 minutes exploring the terminator and both polar highlands. It was very windy and the seeing was wobbly, I stayed at 125x with the 12mm BST EP. In the south the pair of craters Longomontanus and Wilhelm were mostly in shadow except their rim and looked like dark lakes. Further south Bailly was on the limb, I could see smaller craters and hills on its floor. In the north Sinus Iridum and Mare Imbrium were splendid with many ridges visible. Montes Jura was very bright catching the sunlight. Pythagoras was showing its floor and central peak at the extreme north. One of the best views was of Mons LaHire in Mare Imbrium - it was casting a dramatic shadow. LaHire is 1.5km high, but the shadow must have been 20km long at least. Afterwards I made this crop from the moon phase similation on https://svs.gsfc.nasa.gov/ for the same time: LaHire is the small peak near the centre. The crater in lower centre is Euler, it is 25km wide, almost as long as the shadow of LaHire. Soon afterward clouds rolled back and now it's raining again. I'm glad I managed to observe the Moon, it has been some time. Clear skies! Nik

I finally managed to bag this triple star yesterday, after reading about it on this forum. It was a misty and very still night yesterday, the Met office and CO agreed there should be a clear spell around 9pm and they were right, hurrah! My 180 Skymax lives in the shed and I quickly put it on the EQ5. At this time I was almost sure it will come to nothing because as of 7pm I could not see a single star! Amazingly the sky started to clear from 8pm. It never really cleared completely and I could only see stars up to 2-3 magnitide, just enough for navigation with the 9x50 finder. Luckily 7 Tauri is easy to find: continue a line from Atlas to Alcyone, the handle of the 'mini big dipper' of the Pleaides asterism and you are going to hit 7 Tauri, a bright 6-th magnitude star after going on about 2 degrees from the Pleiades. I tested the seeing first with Theta Aurigae (easy at x350) and Delta 3 Tauri in the Hyades (quite hard but intermittently visible, separation is 1.8'' and magnitude difference is 3.5). Even at x350 the stars looked stable. So I aimed at 7 Tauri with confidence. The distant component C (10-th magnitude, NE of the primary) was easily visible, but at first it looked that my focus on the primary star was slightly off. As some of you know these Maks are no joy to focus with the knob at high magnification. Eventually I realized that I'm in focus - simply the star is very close pair 🙂 It looked like a figure 8 oriented north south, both components of equal brightness. The separation is just .7'' and the two diffraction patterns were intersecting and looked like tiny ripples in the blackness. I kept looking at it for 15 minutes at least, and the view was very steady. I was hoping to contiue with some other tough doubles (Dubhe?) but when I looked up again I could not see any stars, just milky glow from the Moon. My hands were frozen from the manual tracking - too excited to connect the cables for the RA drive. When I packed the scope at 10pm the Moon had a halo. Everything was so still it felt like being in another world. Very pleased with this session! The high pressure air sitting over us will be worth the foggy days if the night skies clear a few more times. Cheers and clear skies! Nik

It was misty last night but excellent seeing for double stars higher up. I pushed the magnification to x350 and the stars were still stable airy discs. Managed to split 7 Tauri, a personal best for me at separation .7'' 🙂 I'll write a short report with more details in the double star section.

Well done, @tripleped! It seems to have brightened to magnitude 3 - perfect for Souther hemisphere observers. Just bad luck for us in the north to miss it with this appalling weather.

I don't have the CC but just looking at the photos the two full length dovetails bars will add some extra weight. The Losmandy one is quite massive. The Mak has just a single Vixen bar. Also the CC has a 2 inch focuser which the Mak does not have. I think these add up in the end. The lightest in the 8 inch class is the Celestron SCT, just 6 kilos I believe.

So the width with your 2.5x is fine. If you rotate the camera you can fit all of the terminator, which is the best area to photograph. 4x and above Barlow will not be worth it, in my opinion. It will create more trouble keeping the object in view and probably lead to oversampling.

You said you have a DSLR, so I assume you wish to attach it to the scope at the focuser (at 'prime focus') essentially using the scope as a big lens for the camera. The sensor inside your DSLR is either 'full frame' size ( 36x24mm) or a crop sensor (size varies, most often it's the APS-C size: 23x15mm). The image of the moon projects on the sensor and its size depends only the focal length so you should match the focal length with the sensor to fit either the full moon or part of it. This calculator will show you what you can expect. Choose the imaging mode and enter the details of your telescope and camera. https://astronomy.tools/calculators/field_of_view/ I suspect that without a Barlow the image of the moon will be undersampled i.e. too small for the resolution of your telescope. Sure it will still look good but with 150mm of aperture you may be able to resolve more detail. For the Moon and planets ideally you should aim for focal ratio about 4 times the pixel size of the sensor in micrometers. Most cameras these days have pixel size of about 3-4micrometers, so you want a F12-F16 focal ratio to catch the best detail possible. In your case F5 is very undersampled but with 2.5 Balrow you are at F12.3 which seems about right. The above applies for planets when you are taking very short exposures. For imaging DSO it's the other way round you take long exposures (minutes long) and then big focal length is disadvantage because the tracking mounts are never that perfect. So for DSO your scope does not need the Barlow at F5 it's close to ideal. But then you need a tracking mount.

I recommend using a 2x Barlow. Your scope is a bit fast and the moon will appear too small and bright at the native focal lenght. With a Barlow at say 1500mm focal length the Moon will fit perfectly on a crop sized sensor.

The next couple of days seem to be the last chance to see it in the evening twilight at 'reasonable' elevation: 5 degrees around 4:30pm. Should be near Venus but lower down. There are reports in cobs.si putting it at magnitude 4 or even 3 today (!!!). The weather seems determined to stay cloudy in the midlands sadly Perhaps people in other locations will be more lucky!

I have two Maks: the 127 and 180 Skymax. I agree with all views expressed above both pro and against. Catadioptics are a compromise of various features. As a happy Mak owner I'm of course somewhat biased and here are some more pro points: Maks are very cost effective, in cost/aperture they deliver lots for your money (but note that simple Newtonians deliver more, and the new StellaLyra CCs from FLO are comparable) One big advantage for me is the total lack of the need to collimate, the secondary is just painted on the front corrector and will never move. In principle you can collimate them by moving the primary but I never had to do it and never heard of a Mak that has arrived out of collimation. For me the sealed tube is a plus not a negative, sure it needs more times to cool and a dew shield but the mirror surfaces stay dust free for a long long time. If you are careful you'll probably never need to clean them until the coating fades (which is does eventually with all mirror scopes). For this reason the Maks up to size 127mm make excellent travel scopes. More than 127mm they are specialized for small objects (planetaries, globulars, double starts and of course planets) I say if your sky is dark go for a big mirror scope. If you have significant light pollution then a catadioptric and/or a refractor is a maybe a better choice.

I tend to use about 100x for wide doubles (Albireo, Almach) and 200x-300x for tight doubles, seeing dependent. For equal close doubles even with 1'' separataion a magnification of 200x is actually sufficient (provided the scope has the needed resolution) The pair will look 3.3 arcminutes apart in the EP wich is wide enough to resolve for most people. Unequal doubles is another matter, I would say at least 50% extra magnification is needed and sometimes even more.