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Lunar Crack with the Big Mak!

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Last night I managed to get the ‘Big Mak’ out for the first time this year. Some people regularly inform me that at 127mm it isn’t really that big. Although it’s what you do with it that counts, right? Besides, it’s the biggest Maksutov telescope I own. 



Big Mak cooling on a Vixen Porta II/TL-130 with a Baader Zeiss specification Amici and newly added reflex sight


I set-up at twilight around 19:45 BST. The enclosed system of the ‘Big Mak’ can take up to an hour to reach thermal equilibrium. The Moon was at about 58° in altitude and would descend to around 49° by 21:00. It was 36.3% illuminated and almost thirty arc minutes in apparent size. The seeing and transparency were about average, albeit a little humid.

My original intention was to take out only one eyepiece; an 8-24mm Celestron zoom. This was fundamentally to save weight and space when transporting the entire ensemble down the garden. However, I couldn’t resist taking a fistful of Plossls out with me. Or rather more accurately three of my old Omni Plossls of 15mm, 12mm and 6mm (now with GSO barrels) accompanied by 9mm and 20mm Bresser five element 60° ‘Plossls’. This collection was topped off with four Wratten (# 8, 12, 15, 21) filters. Along with the Baader Neodymium and Baader Single Polarising filters that regularly accompany me on nocturnal excursions.




At 20:30 I decided the tube had cooled sufficiently to try the 20mm Bresser for 77x. This gave approximately forty seven arc minutes of field and I could see the entirety of the lunar disc in the eyepiece view. As it seemed relatively clear with adequate visual acuity I increased the magnification. Initially to 103x, and then 128x with the 15mm and 12mm Celestron Plossls respectively. 



SkySafari 6 Pro on Android


I could not see the floor of either of the Aristotles and Eudoxus features. The bottom of the craters were shrouded in darkness as a consequence of being too near the terminator. The ninety five kilometre Posidonius impact crater was particularly well illuminated and warranted further magnification. Its seventy eight kilometre rimae (fissure) and adjacent crater were astonishingly revealed. What fascinated me the most however were the intricate and intriguing shadow details around the crater rim itself. This terminator chiaroscuro dramatically highlighted the escarpment area around the rim of Posidonius. Which prompted me to increase the magnification to 171x with the 9mm Bresser and then ultimately to 257x with the 6mm Omni. I switched to the Celestron zoom and moving back and forth between 128x and 192.5x I was getting a nice ‘butcher’s hook’ at the Dorsum Buckland. An elevated ridge area north west of the Plinius crater. I could also easily view one of my favourite linked trio of craters, now enticingly near the terminator. These are situated just to the south of the two hundred kilometre Sinus Asperitatus region. Theophilus, Cyrillus and Catherina are all possible impact craters between ninety eight and ninety nine kilometres wide. There has been some conjecture that one or more of them are volcanic in origin. 



Moon Atlas on macOS (Theophilus, Cyrillus and Catherina can be seen immediately to the left of the Mare Nectaris)


The two kilometre high triple-peaked central mountain of Theophilus was very distinct and its crater walls were very nicely defined with a great deal of detail. The floor of the adjoining Cyrillus and its satellite crater ‘Cyrillus A’ within it were easily perceived. Catherina’s highly irregular rim was well in evidence as were the ‘Catherina P’ and ‘Catherina S’ depressions in the crater floor. Other notable features were the Mare Nectaris, Piccolomini, and Janssen with its distinctive rimae. After two hours and forty minutes it was getting damp and cold. I finished the session feeling quite confident that I’d had a good crack at the Moon with the Big Mak.



Edited by Nightspore
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On Saturday teatime I had my usual weekend fish and chips and was correspondingly full of beans. Well, full of lightly battered cod and chips. That is, of course, assuming it was not Vietnamese catfish masquerading as the benthopelagic Gadus morhua. So suitably energised by all the protein and carbohydrates I decided to set the Big Mak up again. I took the same eyepieces out as Friday, except this time I took some Baader colour filters and a Lumicon #11 Yellow-Green. The First Quarter Moon was unmistakably in Gemini, at an altitude of nearly 62° and 55.2% illuminated. At 20:30 the 127mm catadioptric had cooled sufficiently to attempt some viewing. As usual I started off at 77x and 103x. The seeing and transparency appeared above average. As the sky was still a bit blue I used the Baader 495nm yellow longpass filter for a tad more contrast. In fact, I used this particular filter for virtually the entirety of the session. I’d totally forgotten just how effective it was.




Starting in the northern hemisphere I was very impressed with the jagged crater wall shadows on the eastern floor of Archimedes. The largest impact crater (eighty one kilometres) on the Mare Imbrium. The nearby Aristillus crater’s ejecta ray system was prevalent but it was the central peaks, nearly a kilometre high, that really caught my attention.




The Mons Bradley massif, named after the astronomer James Bradley (1692-1762), was very nicely illuminated. Situated in the Montes Apenninus it is over four kilometres high. Although I could easily see the nearby Conon crater, the fifty nine kilometre Eratosthenes impact crater was mostly obscured by terminator shadow. Baron von Gruithuisen’s ‘lunar city’ was nicely highlighted. No sign of his giant moon fleas though! The almost perfectly circular one hundred and fifty four kilometre Ptolemaeus depression is usually best observed at quarter phase. It didn’t let me down and the internal Ammonius impact crater was nicely contrasted.




I find Ptolemaeus eminently useful for locating the Rupes Recta. A one hundred and ten kilometre escarpment or linear fault. It is actually shallower than it appears, but when it is sufficiently near the terminator it is fabulously and dramatically contrasted against the cycloramic backdrop of the Mare Nubium. This was in fact my ‘target for tonight’. I certainly wasn’t disappointed and managed 192.5x and 257x on it for a while. Eventually around 22:00 a blanket of very white cloud came out of the west and ended the session. 


Screenshots by courtesy of Stellarium and SkySafari Pro

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On Wednesday the 13th of April at 20:30 BST the Big Mak had been cooling for thirty minutes. The Moon was in Leo and about 37° in altitude. It was 89.7% illuminated and would reach transit at 23:01 BST. I decided on an initial observation with Baader Red 610 nm and Orange 570 nm longpass filters. The conditions were generally above average although it was fairly humid. There was some slight atmospheric ‘boiling’ perceptible around the limb. I assumed this would dissipate as the Moon rose higher. At transit it would be at a very congenial 46° in altitude.




The Mare Imbrium displayed some engaging detail and the Montes Recti were clearly delineated. Mons Pico was bright but not too well defined. To the east there was detail in Copernicus even though it was some distance from the terminator. Aristarchus and the surrounding region looked very promising. The nearby valley area was wonderfully highlighted. The Gassendi crater was conspicuously distinct as it nestled just inside the twenty six hundred kilometre Oceanus Procellarum.




Further south the Schickard crater was marvellously displayed and it was just touching the tenebrous side of the terminator. Schickard actually appears as an elliptical shape through the eyepiece due to the foreshortening effect. Eventually I increased the magnifications to between 125x and 257x. I used three more filters in succession, this time predominantly threaded into the Baader Amici prism nosepiece. I find that there is less chance of the filter dewing over in the relatively insulated back of a catadioptric, especially compared to a refractor visual back. Most of the session was now conducted with the Baader Yellow 495 nm longpass and predominantly between around 154x and 171x. Although I did occasionally use the Baader Contrast Booster, Light Blue 470 nm bandpass and Lumicon #11 Yellow-Green filters. 




I spent some time in the Montes Jura and the surrounding area before inevitably travelling south towards the ninety three kilometre wide Montes Harbinger. So called as they appear to harbinger the dawn on the nearby Aristarchus crater. The detail in the terraced outer wall of the crater itself was considerable. Aristarchus reputedly has an albedo twice as bright as that of any comparable lunar feature. I was delighted, and slightly surprised, to observe sunlight glinting on its multiple central peaks. This was peculiarly juxtaposed with the flat, gloomy, and caliginous frozen lava floor of the adjacent Herodotus crater. The Vallis Schroteri is the largest sinuous rille on the Moon. I saw excellent detail in the pyroclastic flow areas up to and including a good 257x magnification with a 6mm Plossl and the Lumicon #11. 




Further south I had a sublime view of the ‘diamond ring’ formed by the large impact crater Gassendi and its smaller satellite Gassendi ‘A’ (the diamond). Although I have to admit Gassendi has always suggested the outline of a ruined castle and its turret to me. The rilles in the crater floor (Rimae Gassendi) were readily apparent. As were many albedo features in the foreshortened Schickard crater. These were very well highlighted prompting me to spend considerable time observing them. After about three hours the Moon had reached transit and I called it a night. The Baader 495 nm filter was probably the most effective for contrast detail. Although The Baader Contrast Booster gave the most natural image. The Lumicon #11 made of Japanese Hoya glass excelled at magnifications of 200x and over. This session has effectively concluded my recent triptych of outings with the Big Mak. At the time of writing the Moon is 98.9% illuminated. Which means one of the only features now well contrasted by terminator shadowing is the Grimaldi crater. Although, several years ago, when the lunar phase was virtually identical, I saw possible Transient Lunar Phenomena in Grimaldi. Alternatively the bright flash of light I witnessed may have been a meteor strike. However, that's another story.


Lunar images by courtesy of Stellarium & SkySafari 6 Pro

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On 4/20/2022 at 11:13 PM, Stephen Waldee said:


Wonderful post; it corresponds with some tests I made, based on your suggestions, of using the light yellow filter plus an IR/UV cut filter.  (I will say only that the seeing, here, was SO good on the particular night, that I did not see any 'revelations'; and my ST-80's achromatic correction is sufficient that I do not "suffer" with it, the way my wife Regina does (she has had her lenses replaced and sees ALL KINDS of 'false chroma' in such small achromats that I don't exactly envy that...)


As to the concept of Big Mac (k), the largest commercial one I know of is the AP 10"; so perhaps along with the 7" once made by Questar (not to ignore the 7" Meade); the 6" Russian ones, and so forth, 127 mm IS perhaps near the middle.  However...


So few persons have the apertures larger than 127 mm (in a half century I have seen--in person--exactly ONE of the 7" Questars, ONE of the Russian sixes; and NONE of the others save in magazine articles and advertising pictures) that for all practical purposes, the amateur community pretty much tops out at that size.  And I've used onr myself (actually had to repair one) and liked it VERY much for things like globular clusters; disliked ONLY the problem that one can't use it much lower than around 50x in any practical way.  


You are lucky to be able to thermally stabilize this in an hour.  IMO, it takes about 3 hours for my C-11 to stabilize well enough for planets at hundreds of diameters of magnification.  I found that a 100 mm Mak I had my hands on, for a while, also required AT LEAST an hour.  Even our 4.5" Newtonian StarBlast requires a half-hour (but it has a soda-lime primary, not a Pyrex one.) 


I was visiting the Celestron factory on behalf of one of my employers, once, and watched with great interest how they were collimating a 90 mm Mak in their "clean room" with an artificial star.  They employed *900x* and the tech showed me a FLAWLESS, textbook Airy Disk, equal in and out of focus.  It's rare to be able to do that in the *actual atmosphere*.  In discussions about that I was led to accept the notion that MOST of the time, the telescope is FAR better than the air.  Only when I got nights of Pickering 10 at my Calif. west coast high altitude mountaintop sites, did I have the same actual experiences with flawless star images "in the real world", as it were.  It's quite disconcerting when that happens! Based on my experiences with a 127 Mak (probably made at exactly the same factory as YOURS, Nightspore) I'm of the opinion that such instruments as this are REALLY quite special.  If I did more planetary observing than I do in truth, I would definitely get one.


Steve & Regina, Ivins UT



Thanks Steve, I'm glad you enjoyed the post. Combining a yellow filter with another contrast filter is supposedly an old trick to ameliorate cyan fringing in achromats.




Over the years I've tried many of these.





Although yellow or yellow-green filters are good for lunar viewing with any scope as they help with contrast. Staring at the lunar surface for hours without some sort of filter tends to get a bit weird for me. 




Six and a half grand for an OMC200 seems a little extravagant lol. So I think I stick with my 127mm for now. For a start it's far more portable. The OMC does look nice though. The three Mak's in the picture are made for the Synta Technology Corporation of Taiwan, almost certainly by the Suzhou Synta Optical Technology Co., Ltd. in Jiangsu on the Chinese mainland. I believe the same scopes are or were marketed as Celestron among others. The 102mm and 127mm can take around an hour to cool down, possibly longer, depending on conditions. The 102mm was the first MCT I ever bought. It was originally bundled on an EQ mount. They are portable and effective scopes for lunar/planetary.




Getting a wide exit pupil is not easy with such slow scopes (the 90mm is f/13.8). I've tried experimenting with reducers on 25mm eyepieces to effectively make them 50mm focal lengths. I couldn't see the Gregory spot through the eyepiece but I was never really satisfied with the result. Another thing I dislike about Mak's is that the first diffraction ring is fairly bright. This isn't a problem for lunar or planetary viewing, but can hinder splitting close double stars.




It took me a while to figure out how to use the 102mm with a viable finder on an AZ. It's usually pretty stable after an hour of cool down.




The UK has a fairly temperate climate though and I store it in an unheated room. So the differential usually isn't that huge really. I was initially surprised when I discovered that the 127mm on average only really needed about the same cool down time.




The 90mm is usually pretty stable after around forty five minutes. 




You're probably wondering about the metal silhouette cat on my lawn. It was to discourage the neighbourhood cats from using my lawns as a toilet. I've since discovered ultrasonic motion detectors are more efficient. ROTFL


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13 hours ago, Stephen Waldee said:

 Good thing you pointed out the metal cat in your yard.  I had NOT noticed it! Regina reminded me that Sherlock Holmes once said, "Watson: you SEE, but you do not OBSERVE." Sometimes that's my problem, too!



I think Watson was smarter than people think lol. The metal cats cease to fool the actual cats after a while. Although initially they work. Multiple ultrasonic motion detectors work well, scaring any malignant moggies away. 




If you look vertically down from the base of the dew shield on the 127mm SkyMax above you can see a small dark green box right next to the fence gravel board. That is one of five detectors I have around my bottom lawn. If I use less than that the cantankerous cats try to furtively sneak around them. With five detectors (each corner & the entrance) the flatulent felines can't move without one or more of the ultrasonics going off and scaring the pants off them. Elementary, my dear Watson. lol

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