AlexK

When you start using that concenter you will quickly realize that all you need from that wonder-disk is just the center hole and a single ring (just use the focuser to go from the secondary edge to the primary. There are many rings there just to cover more telescopes. Otherwise, that's just a glorified sighting tube. There is no secondary offset gauge either (how come they are saying it is addressed too?). I have just 3D printed a combo tool (see the first link in that blogpost for the guide I've been following) when I needed to adjust the secondary in my Astroscan once (~10 cents cost ). Works the same as that concenter I believe, but custom-tailored to the target aperture.

Kinda expensive for what it actually is (a trivial sighting tube for an arbitrary sized newt). But I guess you are buying a peace of mind Unless I'm missing some hidden ingenuity in that carved polycarbonate front disk?

Thank you Tiny Clanger for remining about those good old days of film camera tricks. I agree some might work. My favorite one is the "space walk": hold it at the very CoG and use the short shutter delay; watch the counter indicator; and just prior to the shutter release "drop" the camera, as if it's free falling straight down from your hands for a split second. Makes wonders in low light as soon as you figure how to make it falling straight without rotation. However, there is a serious difference from the photography here: you need to sweep the sky with binos often and the angle is usually very high. So I would look into video shooting tricks as well. For example, I'm used to handle my 16x50 holding it as a monocular with my elbows resting on my chest one hand on the lower bino OTA, another holding its wrist. That's how you hold the ancient portable 8mm camera by its pistol-grip handle. However, a trivial long enough stick is such a DIY no-brainer that there is no single excuse for not making one for a trivial lean-to monopod, which will improve your binos steadiness at least an order of magnitude granted. Add a single bolt and nut to clamp one more wooden piece from the side and you have a sturdy bino attachment point. Cut it and add another bolt and you have the venerable bending section to look near Zenith. It's good to mend stray dogs problem in a rural black hole as well

Sorry, for the generalization (corrected that post for clarity). I might be too far with that, there are rare (2-3 models I ever encountered) RDFs with the lens collimator indeed. However, Telrad and RDF are two very different pointing devices in terms of the supported pointing flow, even though I know for sure that 99% of observers are using their Telrads as a trivial RDF all the time, because there is no "how to point with Telrad" instruction coming with it Telrad is still better at that indeed, due to the reduced aberrations ruining the collimation away from the optical axis. The primary difference is that RDF has just a dot which is rather easy to collimate satisfactory on a cheap, while Telrad has a set of rings covering the much wider FOV, which is harder to maintain collimated thus it's equipped with robust collimation mechanism. Only recently we've got even wider rings pattern with the Telrad successor invention QuInsight. It's using a much higher quality two component collimator objective allowing to expand the 4 degrees Telrad reticle to whopping 16 degrees! Using it exclusively lately. Re the image above: it's a bit misleading. #5 is not a projection display, it's just a light splitting mirror, making the collimated (parallel) beam from the lit reticle and the starlight coinciding in your eye optics as if both are coming from the same direction at infinity. And #4 is not a focusing lens, but a collimating lens (or simply "collimator"). See my Wiki link above for details of that physics.

That's only partially correct I've been also trying to steer from the RA optical finder idea the OP mentioned towards the RACI one and warn about the required mental equilibristics transitioning from the naked eye direct view to the RA and then to the Newtonian FOV, which is also upside down. Sure thing, for some people that might be a nobrainer, and definitely it's learnable, but I saw folks really struggling with that, especially in B1 sky when even a cheap RACI is full of stars enough to cause a nausea in unprepared minds ....

A common misconception. All RDFs (except really exotic el-cheapo China plastic inventions) are using the light collimation principle utilizing a semi-transparent concave mirror (or a lens) as a collimator for that. In a nutshell, it is placing the lit reticle at infinity, where the stars are. You supposed to place your eye as close as you feel comfortable to avoid hunting for the reflex dot around. Sadly, several optical aberrations of a cheap mirror as well as possibly not ideal eye-sight of the observer coupled with fixed focal position of the reticle might ruin the collimator principle to the extent of the dot being not perfectly fixed in the sky as it supposed to. But in Telrad, for example, which is using the exact same principle, you can focus the reticle perfectly collimated, so you just bring your face to the mirror, notice the reticle and point with it as if it's really in the sky.

The right angle finder is actually harder to use. You need a lot of practice pointing looking into the ground instead of along the OTA into the starry sky (boring isn't it? ) and a good digital star chart capable of flipping the chart left to right (mirror) to match your finder FOV. If you really want to point tediously star-hopping with optical finder (e.g. heavy light pollution) I'd recommend to add some RDF for the initial direct pointing, otherwise it's a lot of confusion. Better look for a RACI finder (Right Angle Correct Image). You still looking into the ground with it, but at least it moves the field intuitively when you push/pull your Dob around. OTOH, an optical finder is a PITA in my opinion for an average scope (up to 16" easily). After 30 years of fiddling with different finders and pointers, I'm settled on Telrad and TPM for the past 10+ years. Because as soon as you learn constellations to the extent of being able to identify every well visible star (after proper darkness adaptation there are just about 500 to ever care for) nothing could beat Telrad, even GoTo and the latest StarSense Explorer tech. You just move the reticle between stars naked eye to match its position on the chart and your target is in the main eyepiece in 5-6 seconds from the idea to try finding that dim nebula guaranteed every time. My RACI finder is just a mounted binoculars replacement.

There are 3 accessories perfectly complementing my z12, eyepieces, and NBs, which are essential and frankly all I actually need for my visual DSO observations lately: The dedicated old Android "phablet" with AMOLED screen and a pen (Galaxy Note 4) with the DIY DSO Planner app custom-configured to my observing flow making the night planning, objects finding, identification, and observing fast, efficient, and not ruining my strictly maintained darkness adaptation. QuInsight reflex pointing device (Telrad before that) with the DIY modded electronics (targeting the darkness adaptation preservation as well) for the ultimate objects finding and scope pointing aid (with the direct help of the app above). It's also my current astronomy-related tinkering toy (as I'm a programmer) amusing enough in the field and at home (coding, electronics, and 3D printing ideas). My DIY observing "throne" convertible in minutes to/from the highly adaptable 12" Dobsonian transportation aid, table during the day in the field, and to the slim storage package. Without it I might be stuck observing from light polluted home location too much. A bit heavy, but super comfy.

What Jiggy said ^^^^ Many folks observing sitting in the chair high in the air. Jumping back and forth would be tiring. But you can place your finder anywhere on the OTA where you feel it comfortable! It all depends on your scope, its mount range of freedom, your pointing/observing flow, and physical condition/parameters of your body. E.g. on mine I had the Telrad (my only pointer) placed on the side for over a decade: As that was super convenient (and even more healthy) with my quick TPM flow, when I've been using the telescope "Bazooka style" sighting through standing on my knees. Now I'm using the QuInsight for pointing and have it placed a bit above the Eyepiece and all the way behind the rim of the OTA! No actual image yet, but that allows to simply turn your head to the left from the eyepiece view and point to the next target. As you can see I'm keeping my stock RACI finder in place, as I just need to stretch a bit to take a look through its eyepiece. Not using it for pointing though as that's counterproductive having the QuInsight aligned.

Thanks for that, Paul. Even though I've ditched the Fusion360 in favor of OnShape.com simplicity long ago and making all threads by simply spiraling a triangle over the surface These threads can be FDM printed indeed after some test prints done to fine tune the sizes, as all plastics are different and often can't match needed tolerances just out of the box on a random printer. However I would stay away from that possibility at all cost as they will be unreliable if need to be used often. If that's a rare occasion for that thread to be undone then it might be OK if it's not too short (e.g. I would hesitate using it in a filter wheel for example, or with a $3K interchangeable camera lens). Still I would print it undersized and use the heat gun to set it over the mating metal thread semi-permanently. Fortunately, the 3D Printer at home and free CAD software allows you to avoid using threaded connections in 90% of cases completely. E.g. for a filter wheel you can print filter cassettes and use sturdy spring latches to fix them in place with filters clamped inside.

I believe in Musk. I feel all the hype around missions complexity is just to squeeze more money from the govt to cover all the legal risks and stuff they require to be covered just in case. For a private journey you can go with much less, but in a better shape, especially having all the AI advancements Musk owns by now.

That's basically a combination of Cheshire and universal sighting tube. Concentric rings in the middle of the FOV are for different scope apertures (but surely could be leveraged as additional visual references on a particular one). The proper sighting tube need to be calculated for a particular scope. See the first link in my blogpost here with all the theory behind it.

I have already gave a hint on the fact that at least 90% of old astro market players can't really compete with China on many positions anymore as their old high-tech is actually so mainstream now that a perfect laser diode can be purchased for $1, while those in their collimators are barely c10 in a batch. As a result, today, that old $150 Hotech is actually on par in quality at least by points at the dedicated task of a Newtonian collimation with a $20 noname china collimator. I would even speculate that these Hotech lasers are made in China for $10 a piece. I.o.w.: the higher price-tag on astronomy merchandise doesn't always means a better quality. The above thread confirms that conclusion very well I think. My advice, if you still need basic astro stuff like a trivial laser collimator get it from China now, as China knowledge of the open market grows fast. I have purchased that $25 laser collimator linked above for just $13 shipped only 14 months ago. Soon the price on it will be on par with that Hotech as they are practically the same thing...

Welcome to the forum, Martha. Your best bet would be to look around for a used telescope in that price range on the local Craigslist (or its UK/EU analog free web service). Also, I'd check your local Facebook market as well. If your FB profile is decent (as sellers will check it no doubt) you may negotiate a very good price (been there done that). If still not 100% sure, just showcase your findings right here and we will lead you to the best bang for your buck among the options you see viable yourself (e.g. short drive from home). The online store prices and delivery delays are on the steep hike lately due to the pandemics craze.

Also, Cheshire (vs the Barlowed laser) has only about a half of the possible accuracy, due to the Barlowed return beam magnification aiding with significantly more accurate visual centering. But for the OP scope size it looks like a good alternative indeed, as the distance to the image you want to center is just ~650x2 = 1300mm (frankly like checking if your foot nails require grooming ). Try that from 3 meters of the double focal path of a typical 12" F5.

These cheap LCs might be good enmasses as they have much smaller and lighter laser emitter piece inside (harder to knock it off by typical shipping/handling forces). I'm collimating my LCs using the 2" to 1.25" eyepieces adapter (comes with that cheap model linked above). Just clamp the adapter in the vises, or by a C-Clamp, (or even drill a hole for a wood screw in the side) to a desk/table what have you steady and rotate the LC in the adapter fixing by the set screw for each mark point angle, making sure it's in contact by the front lip (for the orthogonality). A "V-block" like that classic one above assumes the piece is turned. While in China it might be stamped, so the coaxiality of its body "curves" is not guaranteed actually. I.o.w.: you want your nails on its 1.25" barrel only.

First of, check the collimation of your laser collimator (LC). It may be just OK as is (~3mm shift at ~7m distance screen is OK), so it doesn't actually need a collimation. As soon as you confirm that the shift in your OTA is smaller than that (if not, you have to do the total re-collimation of your OTA, not the LC), collimate with it as usual, and then move to the Simplified Barlowed LC method (SBLC), which could actually benefit from el-cheapo LC device like the one recommended above (I have that one too, and it is better than the stock LC which originally came with my 15 y/o Zhumell 12" (z12)). If still in doubt (I know, it's hard to trust a new method, especially when it's "simplified") follow with the star test. I'm using the above flow for over a decade with my z12 and never had the SBLC failing the Star test even with a total garbage LCs used on occasion. On a side note that short 130P-DS you have have to be collimated only once. So if you don't play football with it it should stay perfect forever if you do the last collimation step with the counter-screws and lock the cell. Thus for that $145 Hotech wants for a $20 LC, I'd rather invest into a dedicated Barlow (with your 650 mm focal you might want a 3x one for a wider light cone to cover the center mark; you don't have a center mark? Just draw it!).

The most crucial part of the platform planning is figuring your telescope CoG geometry. That should be taking into account all of the possible configurations (e.g. the heavy smartphone in the DIY Starsense Explorer cradle and its counterweight attached). Which will often limit what you can use in your design given the optimal size of the platform. As too large a platform will interfere with your dancing around the eyepiece in the dark in X/Y/Z dimensions, while a too small one might limit your guiding time or have compromised stability at the ends of the tracking range.

Welcome to the forum, cdbrad! To address your question properly, please let us know what telescope (mount) model exactly you plan to connect to your smartphone? Have you been doing that before with SkEye on an Android smartphone? And if so what's the reason you want to switch to the iPhone now?

Ahh! The first post! Welcome! Surely depending on the city park air conditions, but in my opinion, the skill of achieving and maintaining the eyes darkness adaptation in the heavily light polluted environment long enough from pointing at to observing of the DSO is the key to success, Bortle 9 or 1. But that's surely a totally different and huge subject of its own...

8" is a good choice (even though with a collapsible I'd go all the way to the venerable 12") and definitely a significant upgrade to the 4" MAC (the rule of thumb is: double your aperture when you want to see more). That 150p heritage is indeed very popular but in fact quite junky (if you search for it on the forums you will find kilometers long threads discussing how to fix its numerous flaws) , especially with its particle-board semi-fork. I would hesitate to call it a Dob even to avoid insulting the marvelous Dobsonian mount Besides, the Heritage is a tabletop. So you will have to haul a tripod as well, which is harder to conceal. That retractable SW looks like a good compromise for the urban "concealed carry" task as well, even though a couple of kilos heavier than a solid OTA. In my 18 I've been a very slim built but have been carrying 70kg flour bags with no single sneeze by several dozens a day ("easy" money on railroad station loading/unloading work). A 8" SW should be a piece of cake for you. I know a guy hauling his 16" collapsible in the backpack to the 2km high mountain top through the snow almost every New Moon! I'm personally taking my 12" full OTA z12 Dob to the car trips and I do carry them from the car to the observing location for 50-100 meters into the open field easily in my bare hands. OTA in the right, base in the left, backpack with eyepieces on the back. You just need to attach proper handles to make it possible, as a 10-15 kg in each hand must be laughable for a man On a side note. I'm living in the 15+ story high-rise apt complex in a heavily light polluted place too (on 10th floor though) and found its roof a way better observing choice than any local park around as all the lights around, haze and city smog being way below the 360 degrees round fully open horizon up there (well, I have a hill-top eucalyptus on the North-East blocking almost 20 deg, tbh). When the Ocean is calm the views are on par with the B3-4. The roof access door is locked (which is a security benefit for a solo observer too). But I have a key. Just try to approach your building management or security politely to allow you there occasionally with all necessary precautions and rules obeyed. It might turn out the person in charge might be interested in astronomy too! Also, in some buildings you can find public balconies on each or certain floors or in certain buildings you have lawful access to. Just research your artificial hills!

That hack is called "Milk Jug Ring" for like 20+ years. Just cut a ring or a pair from the side of the milk jug with scissors.

The difference is that imaging tasks doesn't need platform resetting often as it intended for long exposures of the same object. While visually you may reconsider your target quickly after starting observing it. So to avoid the tracking stopped in the middle of the session you want to reset the platform each time you starting the new target finding/observation just to be sure. So the platform reset better be be easy and quick. Poncet "finger" usually have to be "rewound" back to the start with the motor, which is often geared at its peak performance, so can't be simply speeded up much to achieve that rotating backwards (unless you have a gears switch, or a finger clip, which are both too complicated thus prone to systematic tracking errors and less reliable overall). Another arc means you have 4 points of free resting for the platform. Which is always inferior to 3 points as it is hard to make all 4 on a single plane/surface at all times mechanically (we are talking simple plywood garage DIY project of course). A wooden platform can sag under uneven load and simply with time and weather elements. So it may start rocking around some unpredictable "axes maze" or overload one of the bearings often. In addition, for the high latitude you have a stronger side sliding force on the top platform, which will push into side rollers also unevenly. So your platform will tend to wobble between 8 (!) points of possible contact having 2 sectors. That's why rollers are often made soft, to at least remove all gaps. The high above the CoG South bearing will take that side load perfectly and allow to use just 2 rollers on the north sector without any side-support necessary, so you can go with the most simple, most efficient, stable, and most reliable horizontal motor shaft driving position. Besides, if you draw the cone for a higher than 45 degrees latitude you will notice, that the South end sector tends shrinking to zero anyway As I have mentioned earlier, the recent advances in the modern electronics make the complex driving speed variation a piece of cake even for DC motors, not to mention steppers very popular lately due to silent driver chips available. If in the past all you could do is changing the speed, now you can change the entire math model of that speed changing flow based simply on the internal timer (started on the motor start from the end stop). Thus taking into account any flaws of your DIY construction.

That's the South side single point pivot I've been talking about for higher latitudes. The tangential rod driving mechanism is unnecessarily junky here though, as it's following the classic Poncet "finger" idea, which is considered a flaw due to the too long platform reset time (besides, the classic Poncet platform is actually an imaging device, so it has a very little appeal for visual work).

Looking at the above, a note for the CSSE standalone software successor: Make a feature to limit the PS area to a certain manually selectable region of the camera frame. That way you can avoid dealing with the DIY enclosure issues. The other obvious one: don't limit your ingenious creation to the mirrored image only. But I do understand Celestron limiting DIY hacking possibilities of their product, unless that's their software developer's negligence