Alan64

If the 50/600 achromat has a .965" visual-back, a hybrid star-diagonal would be required, in order to use current 1.25" eyepieces... https://optcorp.com/products/ae-msdh-965inch-to-1-25inch-hybrid-mirror-diagonal, or... https://www.ebay.com/itm/234590518632?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=234590518632&targetid=1263104805286&device=c&mktype=&googleloc=9013737&poi=&campaignid=14859008593&mkgroupid=130497710760&rlsatarget=pla-1263104805286&abcId=9300678&merchantid=8487194&gclid=Cj0KCQiApb2bBhDYARIsAChHC9tJFVKQCsDIvoENdP2mRJZVwR8iF5xUV_q_DEga3K8ByQ6oBuk5Mr4aAqFxEALw_wcB However, if there are .965" eyepieces on hand to use... https://www.ebay.com/itm/115240816158, or... https://www.ebay.com/itm/234476833378?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=234476833378&targetid=1263104805286&device=c&mktype=&googleloc=9013737&poi=&campaignid=14859008593&mkgroupid=130497710760&rlsatarget=pla-1263104805286&abcId=9300678&merchantid=8487194&gclid=Cj0KCQiApb2bBhDYARIsAChHC9ujMUAIo_VIYi4Tsh87dd6Mq6b4Lh3TQoMO0Q72xWWNQ7UFPf5Z3QwaAgRLEALw_wcB If the telescope has a current 1.25" visual-back, this star-prism diagonal would serve... https://telescope-warehouse.com/shop/ols/products/1-14-all-metal-unranded-90-degree-prism-diagonal If that last one is sold by the time, then this star-mirror diagonal would also serve... https://www.ebay.com/itm/363772085781?hash=item54b2818615:g:Dk8AAOSwPLFiOPgB That is, if you can't locate the screws, or replacements for the original diagonal. Telescope Warehouse, also on eBay as "scopehed1", is owned by Bill Vorce, a respected and well-known vendor in the astronomical community. I've ordered a few things from them myself. It would help to see a clear image of the diagonal in question. Do you have one to post, to share with us? If not, here's an image of one of my own. You might then identify the problem for us more clearly...

Believe it or not, I have a 50/600 too, but from 1969, a Sears/Towa. I got it off of eBay for $25, a few years ago. I restored, enhanced it, then saw a globular-cluster with it... What's wrong with the diagonal?

I had gotten a 127mm f/15 Maksutov, an ES/Bresser, my very first of the design... It simulates a 115mm f/16.5 achromat(refractor), yet with the refractor being 190cm in length, over 6'. Among all reflectors, a Maksutov is the only design that has been described as being refractor-like, regarding the clarity of the views. Those who favour a long-focus achromat find that they may have their cake and eat it, too, with a Maksutov; much shorter, compact. Also, with the Maksutov being a reflector, the construction is tighter, and holds its collimation best among same. Refractors, over all, are the most tightly-constructed, and require virtually no collimation, forever? A 127mm Maksutov is the sweet-spot among the varying apertures of the design; not too big, not too small, just right. I see within your signature that you have a 70/300 achromat, at /4.3. I have one of those, too... Most have a go-to mount for their Maksutovs, but I can't use one, as I have far too many trees surrounding me. So, I will be using that little achromat as a finder-scope instead, and for my own Maksutov... I chose a 70mm over a standard 50mm, like a 9x50 optical-finder, as my Maksutov is blind as a bat. It cannot serve as its own finder, a 59x127, no. But with the 70mm, I may realise a 9x70 optical-finder, actually 9.4x, with a 32mm Plossl and a star-diagonal. I knew what was coming, and became resigned to the fact that I would be observing with the Maksutov on manual mounts almost exclusively; for example, on an alt-azimuth... Note the dew-shield jutting out there, of black art-paper, and temporary, yet nigh as long as the telescope itself. Since, I've gotten a proper one... A dew-shield is mandatory, absolutely, without a doubt for a Maksutov, as you don't want the "lens", the meniscus, to get dirty, or as dirty. It also helps to block natural(the Moon) and artificial (street lights, passing cars) light-sources from entering the telescope, entering the view. If you're wanting larger than 5", there are solid-tube and collapsible Newtonians and Newtonian-Dobsons at 6" and up. I have a 6" at f/5...

Keep in mind that the higher in power, the wider a view is desired, 60° AFOV at a barest minimum, per a manual tracking, and so to catch a steady look before the object races out of view.

This may, or may not, work for you... https://explorescientificusa.com/products/iexos-100-2-pmc-eight-equatorial-tracker-system

https://scopethegalaxy.com/what-are-the-differences-between-spherical-and-parabolic-mirrors/ If you wish to avoid coma, and opt for spherical-aberration rather... https://www.kohls.com/product/prd-3797120/celestron-114az-sr-smartphone-ready-reflector-telescope.jsp?skuid=42960323&CID=seo_offers&utm_campaign=SAG&utm_medium=organic&utm_source=google&utm_product=42960323

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I have that one... I regard it as my Celestron "C5", for it is indeed an economical simulation of a Celestron C5 Schmidt-Cassegrain. The collimation was a bit off, to put it mildly, upon arrival. I was seeing doubles of everything. I got it collimated... I then saw Jupiter's Great Red Spot for the first time in my life, through a 6mm perhaps, and nigh tack-sharp. The primary sphere is at a native f/4, which accounts for that drastic off-setting of the secondary flat. However, the optical-system operates at f/8, not quite up to f/10 as that of a C5. Everything required for a satisfactory operation is there, within and without, being predominately of metal, yet all it needs is finishing up, which I did.

I've sent you a PM.

A bit of artistic license, is all. 🖌️ For example, the "Moon Monster"... Then, it's only an afocal shot, like that taken with a "smartphone".

Back to the telescope at hand... I have this base-model 150/750... It started out on a Dobson(or Parsons)-type base, then onto a GSO alt-azimuth, and where it came into its own, up to round 200x. A 150/750 Newtonian enables powers from a somewhat low yet effective 23x(32mm), up to, in theory, 300x(2.5mm), particularly on the Moon. I took this through the telescope, although at round 180x(4mm), afocally... ...and this... At the lower and lowest powers, the telescope may serve as a finder in its own right, particularly with an even longer eyepiece, such as a 2" 38mm 70°... https://www.firstlightoptics.com/ovl-eyepieces/panaview-2-eyepieces.html ...or even a 50mm Erfle(15x, and binocular-like)... https://www.apm-telescopes.net/en/ts-optics-2-erfle-50mm-rich-field-eyepiece-52-field

There was no way of knowing at the time, of course. Over the last few years, I have wanted an OTA of that kit, myself, as I have other mounts, and in knowledge of its characteristics. Over the years I have also learned that, sometimes, opinions, and even recollections online do not match what a user experiences, there in the wilderness, at and in their home.

It is only a slight, nagging thought that the reply was in error. I still think it to be spherical, given that when a Newtonian does have a parabola, that is usually, always, touted within its sales-listing online. The trouble in the case of this one is that Celestron simply doesn't divulge specs for their products, hence not knowing if it is or isn't, with certainty. I just now discovered that 130mm f/5 spherical primary-mirrors are being made overseas, and being sold on AliExpress, at least. Did you choose, purchase your kit , and if so, what was it about the kit that had drawn you to it?

I got this base Synta 150/750 OTA, with a plastic focusser, back in 2012... I've witnessed snap-to focussing, and with a barlow inserted to boot, with the Newtonian. Granted, that is not to say that it's perfect, no, as it is mass-produced.

From 76mm to 130mm, the Newtonians, in the marketplace, with a Dobson base or no, are definitely mass-produced, and in danger of bearing spheres as a result. Thankfully, we're not seeing spheres, much, at 150mm and larger, save within the Cassegrain family, of which my "Bird Jones" is a proud member, however shunned. Once, a parabola was most coveted and prized, more then than as it is now, as we're used to their inclusion within most Newtonians, taking same for granted even. Refractors with a doublet of obsidian; what, an inherent variable-polariser, or for observing our nearest star?

The cold, hard facts of life: it is more difficult, more costly, for the manufacturers overseas, to produce parabolas, at left... I found this the other day... https://www.telescope.com/Orion-SkyScanner-BL102mm-TableTop-Reflector-Telescope/p/134763.uts It is a 102mm f/6.3 Newtonian-Dobson, and with a spherical primary-mirror indicated. Elsewhere, I had asked as to whether or not it would be suggestible to those first starting out. No one replied to say yea, or nay, which I was meant to take as a no(?), hence, f/7 and above going forward as suggestible; and with the mirrors dictated by said manufacturers, apparently. A 130mm f/7, and with a known spherical primary-mirror... https://www.firstlightoptics.com/reflectors/skywatcher-explorer-130.html I would love to have just the OTA, there. Its sphere would be the least of my concerns. Instead, I would have to remove three of the spider-vanes, and as I did for this Celestron "PowerSeeker" 127EQ, and with a primary-mirror at a native f/4 or thereabouts.... However, the telescope is itself at f/8. After I had collimated it, I saw the GRS of Jupiter, for the first time in my life, and nigh tack-sharp, at over 150x. But with a traditional, classical Newtonian, let's be thankful for the spheres we're receiving from overseas, but at f/7 and above. Let's keep in mind that the master observed at f/5, and with a sphere... Who are we to deserve better?

No, at f/6.3 and under, that would be a gamble if spherical, which includes an f/5. I should mention that the Q&A reply from Celestron may have been in error, I sometimes think, regarding the "AstroMaster" 130EQ. It may have a parabola, in fact. Historically, Celestron has been tight-lipped about a lot of their specifications, for this, and for that.

I wrote, "At f/5 for a reflector, a spherical mirror is inexcusable, and acceptable only at f/7, minimum, and longer, like a 114mm f/8"; not "f12" or above.

During a few weeks round late August of 2015, we experienced a drought, and as I'm experiencing again, at present. I then decided to take my FS-102, 102mm f/8 out to the Moon... The image of its doublet there has always reminded me of these... The blue light from the power indicator of my desktop PC from across the room entering the doublet... Here, blue and green are seen... An afocal shot of the Moon through a medium-grade ocular; nothing fancy...

I'm relieved to hear that you've bypassed the "Astromaster" 130EQ. Celestron had stated on their website, a Q&A reply, some years ago that the primary-mirror of same was spherical, rather than parabolic. At f/5 for a reflector, a spherical mirror is inexcusable, and acceptable only at f/7, minimum, and longer, like a 114mm f/8. That of the Bresser 150mm f/5 is parabolic, and for sharper images; well done. I have a 150/750, and my largest operational telescope, which started as a Newtonian-Dobson... The mount of the Bresser kit may be motorised... https://www.bresser.de/en/Astronomy/BRESSER-RA-Tracking-Motor-Controller.html ...and for automatic, hands-free tracking of everything in the sky, keeping any object there in the centre of an eyepiece, for hours if desired. The 6V battery-pack for the motor-drive may be bypassed, and for either a direct connection to the mains, or for portability, a rechargeable, lithium-ion, 6v battery-pack, which may require a bit of tinkering. There will be the discipline of collimation to learn and master, and for sharp images at the higher and highest powers. At f/5, the Bresser will be somewhat difficult, however easier than at f/4. Hopefully, the telescope will arrive well-collimated. I've had my own up to 180x or so, and have seen the glories, but on a motorised equatorial, like that of the Bresser kit, 300x is possible, albeit most easily when observing the Moon. I saw this one night with my own, at said power; an afocal shot... That feature has been called 'The Maiden Looking Out Upon The Sea", or "...Looking Out To Sea", whichever. Again, well done.

Modern, go-to equatorial mounts are equipped with a host of computerised/electronic features to help ensure perfect results. Some success can be expected without, but it will be more difficult.

Given its age, yes, absolutely, a re-build is in order, and you can get an idea as to how to go about that from this... https://www.youtube.com/watch?v=qujs7Kt_6_c&t=2587s I use heavy-duty Super-Lube for my mounts. I do not use the silicone-based version, only the PTFE(Teflon) version... The silicone-based is for plastics, plastic gears for example. Of course, you can use any grease that you prefer.

If you get an 8", you'll always wonder what a 10" might've been like. If you get a 10", you'll never wonder as to an 8". Two extra inches in diameter doesn't sound like much, but when you consider the light-gathering area instead... ...there lies the advantage, particularly under darker skies... ...for globular-clusters, nebulae, and galaxies, as well as the planets.

The Celestron "AVX" is considered to be an entry-level imaging mount. It is a go-to EQ5-class mount, which evolved from the manual CG-5(an EQ5-class). It has lots of bells and whistles for that very thing. I have a manual EQ5-class mount, this Meade LX70... The "AVX" is simply a go-to equipped version of that one, sans the pier, and in black. However, for the long run, if one anticipates many merry respites whilst imaging under the night sky, one of these would be the better choice... https://www.telescope.com/Orion-Sirius-EQ-G-Computerized-GoTo-Telescope-Mount/p/116276.uts It is the same as the HEQ5 Pro, sold in Europe, and the U.S. even, but in white... https://www.highpointscientific.com/sky-watcher-heq5-equatorial-goto-mount-s30400?utm_source=google&utm_medium=cse&utm_term=SKY-S30400&gclid=CjwKCAiAvriMBhAuEiwA8Cs5lXunewcuO0PoNKvdCrOwC3dyHtLrE-g63GOsTa7M4lk37YURZy1pahoC-AwQAvD_BwE You could say that either one of those is an EQ5.25 or 5.5 class mount. A bit sturdier than an EQ-5, but still not quite an EQ-6. When imaging is considered, the mount is of paramount importance. A camera's sensor is most unforgiving if a mount shakes and wobbles, resulting in blurry images, and to the point that if a telescope and camera could be mounted upon a huge boulder, that would be the ideal. A 5" Schmidt would be quite comfortable upon one of those, or a short 80mm triplet refractor.

I would skip a 200mm/8", and get a 250mm/10". The best 8" is a 10". The 10" would require somewhat more expensive eyepieces to observe at the lower powers, but in the long run it's still the better choice. A 250mm is the same length as a 200mm, just a little larger in girth. Collimation will be a bit more difficult, at f/5, but not too terribly much.