AlexK

Good choice! With the 200mm aperture you will need a decent star chart. As ideally you want it to map every star you can see in your eyepiece to properly find and identify most distant deep space objects your 200mm is capable of revealing between stars. Paper charts doesn't cut it starting from approximately 100mm aperture, as the sole weight of the paper and paint needed to print millions of stars would be insane. Thus, meanwhile you can try to play with some digital star charts on your smartphone (if you have one of course). There are plenty of offerings for both Android and iPhone platforms. Having an all in one digital astronomy assistant in the palm of your hand when you are at the eyepiece is on par only with a seasoned visual observer sitting patiently behind your shoulder

My bad. Peter's reply is indeed OK per jure That flimsy tripod wouldn't carry a typical 8" well. Though still lacking a diligent explanation. The OP point was to continue using the CSSE on a better telescope, but Peter's answer was frankly "No, you cannot". Which is discouraging. So I unintentionally (or subconsciously? ) did the same: ignored Peter's point and haven't realized that just until now! Because a 8" is usually associated with a Dob to me, and the Dob means the decent proper mount for it is included. Fixed my post above.

You were smart indeed! And fake "brands" are indeed not bad at all in many departments. But you've missed my point in the reply to John, that this research must be current. You haven't stated how long ago you have purchased yours and also confused stuff quite a bit for him providing the link to the obscure merchant's website (which is often vanishing overnight) instead of the trusted Amazon product page with all the real reviews and warranties. I do believe to your praising micro-review. However I personally had 3 powerbanks over the years which were working like a charm for months but then developing a hidden defect well after the Amazon return window (in 2 cases it was a faulty cell in the pack, in one the faulty charging controller which I have fixed later). Thus, you want at least 50 people confirming it's good (which is pointing at the fact they are using it for a while) and no discrete complaints on failures pointing at bad quality control. If there is a comparable product with more reviews that's usually even better.

That's because you are not following my advice Beaudens is just a "fake" brand name of China electronics' reseller. They are re-branding China stuff to build some public trust locally. I bet you will find the exact same formfactor, specs and even the faceplate on Amazon under some "Ugebogat" "brand" name. "Swarey", actually. Just found it: https://www.amazon.com/Portable-75000mAh-Phosphate-Generator-Emergency/dp/B08FD4R8ZM/ Again. Don't do that. Use the keyword and research what thousands of users are buying on Amazon today and not complaining too much about (if they are - see what was that). As these "brands" often vanish after their complaints metter drops below 3 and starting a new "brandname" with the same faulty junk listed.

That Baader Zoom is actually considered lightweight, as all of its lenses inside are under 1.25" mark (or close) that's in fact a 1.25" EP (just with the stock 2" adapter attachment). Telrad is very lightweight as well (single lens), especially if you use it with Lithium cells (by the way, these are bar none in weight and longevity departments to the task, except for the external USB power cable of course). So you are good. And you are definitely don't have to do anything with your mount until something starts annoying you. I.i.r.c. SW S line dobs are using the side brake mechanism to adjust the friction in altitude as their mount trunnions are rolling on plastic wheels there. That one of the "improvements" from China engineers to the classic Dobsonian design. I would be personally annoyed by the need to tweak it with that handle constantly

Thank you, Dave! A sub-question then: The performance on a GEM depends only on the plate-solving algorithm implementation used in the CSSE app. There are several ways it could be done. Theoretically, as they require you to align with a target first, they are most likely using one of the straight-forward math approaches (Ha/Dec <-> XY mapping). However, some folks are reporting consistent failures on their GEMs and on a Ball scope. Which are capable of tilting the phone at significant angles from having the screen sides close to the vertical on Alt/Az mounts. So that's could be the culprit (application code bug or a purposeful limitation). So the question is: can you tell that you've been starting or ending the pointing with the CSSE with the phone orientation being obviously not close to the vertical? Surely it depends on your DIY mount-point as well, but the idea is that if you start with the phone vertical the algorithm will be tolerant to the subsequent side tilting (simply works), but if you start from an awkward angle it will fail. Or in reverse instead. Knowing that could help other folks considering moving the CSSE cradle (or getting another one) to a better telescope to decide their options.

It all depends on your telescope construction. But as soon as you have a classic Dobsonian without various braking handles recently emerged on some designs from China engineers the CoG (Center of Gravity) maintenance is unavoidable as soon as you upgrade your stock cheap and small and thus lightweight eyepieces with something with more expensive glass inside. I do. So for over 10 years I've been using a simple DIY solution made from an old small GEM counterweight puck and two magnets from dead 3.5" computer hard drive: Just a piece of masking tape over magnets to prevent OTA scratching. It holds anywhere on the OTA. Ideally, it should go on the opposite side from the focuser. To keep the CoG below the altitude axis, but that's an awkward location to reach, so I'm using it on the top side of the OTA most of the time, which means I have to remove it closer to Zenith. Lately, I'm using that puck in the special cradle with the pocket for the USB Powerbank, which is powering the mirror cooler, QuInsight pointer, and other low power electronics on the scope. That helps keeping the counterweight higher at hand (no image yet, but here is the 3DP draft of the cradle: The root principle of the Dobsonian mount is that the CoG is always below the Altitude axis line and the gravity vector down from it is always exactly in the middle between Altitude PTFE tabs. That the key not only for its rock-solid stability but also to the perfect fluidity of rocking forward and backward motion.

Thank you for sharing that info, Steve! Good to know CSSE (CelestronStarSense Explorer) app internals. A quick question: have you tried the CSSE cradle with the scope on a GEM? Just curious if it worked for you when the phone's top is not parallel to the horizon? (There is a controversy about the possibility to use it on anything but Alt/Az mounts). For the "black screen and cross only" issue try to move the scope downwards, so the camera could pick up some bright terrestrial target. Older phones cannot show anything in the night sky on the camera preview screen but the Moon (some could even refuse to focus at infinity with nothing in the view, so even if there is actually something it's not focused and thus even less detectable on the screen). In that case, they must be aligned on that "cross screen" with some distant terrestrial target instead. After that, they will employ stacking to reveal hardly visible on the screen stars just fine for the plate solving to work.

Peter is not exactly right. I'm 100% positive you can use the CSSE (Celestron StarSense Explorer) device on any other telescope with ease. And I know people who's done not only that but also revamping the entire phone cradle as the original one is too bulky. It works with any Alt/Az mounted and Dobson telescopes. So, just make sure your future 8" is a normal Dobsonian or Alt/Az mounted (the latter is rare), not some GEM or a Ball mounted scope (even though there are mixed reports the CSSE works on the latter, better skip those for now). Then, just figure a mechanically solid way to secure the CSSE phone cradle with the mirror on the 8" scope tube or mount reliably. The goal is to make it perfectly rigid relatively to the optical axis of the telescope, so when you move it around the sky it's not flexing or rotating from gravity, inertia, or accidental forces (kick, push/pull), otherwise, obviously the pointing performance wouldn't be reliable. E.g. you can make an adapter for the cradle to mount it in the standard finer shoe (just make sure it sits tight on the OTA). Or just drill the OTA on the top and screw the cradle down there. On a side note: the CSSE technology is truly revolutional. Only Celestron's corporate greed delaying it from landing on every telescope making pointing at any targets even more reliable and accurate than with expensive/heavy/bulky motorized GoTo controllers.

The single keyword you should look for when purchasing for you conditions (in fact for most any typical field conditions) is the LiFePo4. The rest is up to you and you will find hundreds of options. Good or bad reviews in the replies here wouldn't be very helpful, as it's always a gambling, because China is sitting tight on the power banks horse lately. Which means the quality control is the thing of the past, brand name or not, unless you are willing to pay quadruple the standard price of $1 for 1Watt/hour (well, at least that what was always a rule of thumb just before the recent prices hike). Otherwise, just stick with Amazon, or any other reputable merchant offering instant free returns and an instant extended warranty (a must with battery products). And good advice from Alan (Alien 13) - get the USB charging tester. They have a nice logger and some even BT/WiFi connection to your smartphone. So you can monitor the drain and peak consumption required (perhaps you have fried your old PB internals due to the unexpected overcurrent which the controller failed to prevent due to the cold). Then just seek for the required watt*hours number + some extra slack.

China is falling into the deep economy crysis. It's a communist state, don't forget. Their economy is much more weird than ours. In short they want more money, that's all.

Congrats for your eyesight incapable of detecting any damage so far. Let's see what you could film in a month and then after 5-th cleaning like that Seriously. There are too many variables involved in this "method", which might work fine for some folks, but could be a disaster for others: Are your hands/fingers/fingernails REALLY clean? An abrasive particle may be embedded in your skin pores unnoticeably for a long time. One can be washed out from under a too long dirty fingernail... Is your tap water REALLY clean? That "shower spigot" creates quite a pressure, which could propel an abrasive flake chipped off your old rusty metal pipes 1 kilometer from your house a week ago... Are you 100% sure no lose particles can be thrown from your sink sides, edges, spigot, clothes while are you working that vigorously around the optical surface which is usually handled in dedicated "clean rooms" by people in special suits? If there are micro cracks in the mirror surface the sole sheer flow of water like from that showerhead could promote some of them expanding further... Have you equalized the water temperature to the mirror surface temperature enough, to say that the thermal expansion/contraction haven't promoted any existing micro-cracks in the surface? Water is overwhelmingly more heat conductive compared to the air. Do you know HOW your tap water is chemically treated? Many countries are still using Chlorine in their water cleaning factories, which is like an acid for aluminum coatings... So No.4: Are you sure your mirror is a top grade mirror made to all optical tolerances so that its aluminum protective coating is (still) 100% intact and uniform? So the aluminum is not exposed to chlorine and other oxidizers (in the soap blob on your spigot?) anywhere through micro scratches, at the not well coated edge, through abrasions under mirror holders? Thus: The only truly safe method we could generalize upon, if you are rather ignorant on most of the above is... TADA! Just leave it alone already! Even a 10mm hole drilled in the coating is nearly nothing for most visual work. While an invisible net of micro-scratches and micro-oxidations is the contrast killer.

Telrad is not just a glorified red dot finder despite the well known fact that 99.9% of amateurs are using it like the one. It's an ultimate pointing device not requiring a second optical finder or UWA pointing eyepiece to land the telescope FOV on your naked eye visible or invisible target from the first try. I'm pointing with it exclusively for 10+ years already (following the TPM method) and it takes me only 5-10 seconds(!) to move the 12" Dob to ANY target I see on my digital star chart. From the moment I tap it on the screen to the moment I'm already enjoying it in my 88x eyepiece. Every. Single. Time. Try that with any RDF or Rigel when that's an obscure lonely 14m galaxy in Cetus. Its size is dictated by certain laws of optics. That's why it was the only trustable in immediate accuracy naked eye pointer for so many years (just until recently, as the QuInsight optics is even better). Because this is the only collimator on the market under $100 (before the QuInsight was invented) with the nearly zero parallax. That means that when it's used as a trivial RDF pointer, and is calibrated properly it allows me to point directly at planets and even guide the view (!) with a 800x magnification eyepiece (E3.7) + 2xBarlow. As the pointing accuracy with it can be 2-3 arc minutes (limited only by your eyesight). Thanks to the longer than other cheap RDFs focal range of the collimator lens and the flat beam splitter mirror instead of the concave reflex semi-transparent mirror off all RDFs (except for the Rigel). All smallish RDFs (except maybe the $400 TeleVue) have a bad parallax in vertical direction because their reticle is off axis in that direction. But in fact, Telrad's primary function is the indirect pointing. Which requires a reticle covering some surface of the sky (well known Telrad measuring rings) and always consistently. That even more demanding on the collimator's quality due to the spherical aberrations stepping into the game. Only when recent China economy advances allowed an affordable SA corrected aspherical duplet collimator mass-produced the QuInsight's expanded reticle became possible for a Telrad-like quality wide-field sighting and still well under $100. The shape of the Telrad is not an ugly joke but the carefully considered highly functional multipurpose engineering design: Many newbies often struggling with figuring where the telescope is ponting in the sky and even relatively to the compass points. The Telrad's large elongated body with right angle edges supposed to provide the miniature model of the telescope OTA functional geometry at hand (the eye comprehends straight lines and angles alignment in space better than any round 3D shapes) and it is also well aligned with its optical axis. So when you move your head to the position behind it, until you can't see its long body, the dimly lit reticle will be immediately visible in the beam-split mirror on the top (by the way, I'm shocked to read you want your RDF retice brighter! But then figuring you pointing to really uber bright stars and planets only with it, and seemingly don't care about your darkness adaptation at all). The long Telrad mounting shoe matching its long body purpose is to provide the 100% reproducible 100% accurate clamping. So after aligning your Telrad once you don't have to re-align it again after removing. You can calculate it for yourself: the typical clamping shoe error it's arctg( 0.1 mm/Shoe length mm ). Not to mention, that it allows perfect shoe grip without drilling the expensive OTA for the mounting shoe. It's an instant nondestructive nonpermanent easily removable telescope pointing upgrade. (I'm also shocked to read you want to collimate your RDF in the day time, as at night it will be off due to the parallax and temperature drift no doubt, but then I understand that you can't point with it accurately due to the parallax and irregular dot shape blinding your eyes anyway, so you have to resort to some second stage pointing aid like an optical finder even if just an UWA EP). The large Telrad's body allows it to fit not only widely available AA cells but also a larger collimator lens and a correspondingly larger beam splitting mirror, thus providing a huge unobstructed field of view compared to any trivial RDFs (but the QuInsight which has that feature improved all the way to perceiving its rings just flying in the open sky well above the UTA rim). The large body height not only providing enough space for convenient collimation handscrews but also a natural riser. No need for flymsy stalks RDFs require most of the time. I would also add the ease of batteries replacement in the dark (no flashlight required). But Telrad's power consumption is so small that I can barely recall ever replacing them actually (~6? 7 years ago?). For most RDFs it's a chore to fiddle with their coin batteries blindly. Or it's DIY potential with plenty of space for additional controls, external connectors, and even microcontrollers. But I feel for you, in Russia we have a saying: "The beauty demands sacrifices", which means : A pleasant decorative external outlook often means lacking of internal contents qualities. I'm personally barely see my Telrad in the dark, perhaps, because I'm usually observing in Bortle 1-3

You've probably missed the point that the OP's goal is to extend the versatility of his particular Zoom eyepiece as much as possible. Thus, general Barlow use cases aren't exactly applicable here if at all. A 3x Barlow would be still a better idea. But a 2x would be OK with the additional extender(s), and possibly in the long run, when deficiencies of a Zoom EP become apparent to him.

That's true. We are predators after all, contrary to some opinions. But if the seeing is not there yet bino or artificial shaking wouldn't work on planets anyway. Perhaps, bino also promoting the eyes specialization when necessary. I.e. one eye is used for guiding/tracking body control feedback, another for actual observing of the target's behavior. But that's already a much higher level of the observing expertise, carved into the habit from hundreds hours of observing. Guiding a shaky mount at the very high zoom usually consumes all the attention of a beginner so not to lose it from a random shivering and having to start over from a lower zoom. By the way, for the mono view, that "shaking/rocking" technique is especially useful for very tough DSOs in the peripheral vision. To stay on topic: Any Barlow actually can be easily converted to a higher zoom rate Barlow with an extender tube. E.g. by screwing together two EP barrels. So if the OP is in the analysis-paralysis or denial state after this lengthy chat, feel free to go with the 2x Barlow having an unscrewing lens end (just for the higher versatility) While on a side note, I would ask why 2x Barlows actually existing, when the rule of thumb for the perfect EPs collection is the 2x ramp as well? I'd rather have a 1.5x, 2.5x, or 3x Barlow to extend my perfect EPs collection with more in-between zoom levels variety (not me, but kinda more logical desire than having same zooms with the Barlow for all EPs but the shortest one).

No problem. Just check that https://www.astronomics.com/info-library/how-to-pick-an-eyepiece/highest-useful-magnification/ link and treat that as an axiom. The common misconception is that at too high a magnification like 2.4Dmm everything always looks blurry. That's true most of the time due to the local atmosphere turbulence. However the turbulence is not something permanent at all. There are rare moments it's extremely steady and the trained eye is capable of recognizing a lot of details in a split second (contrary to any cameras even after meticulous stacking of millions of frames). That's why when observing planets you must watch that blurry blob long enough to have a chance catching every such moment. In my experience 30 min is the minimum if the seeing is not ideal. Thus you want either a GEM with fine manual or motorized tracking, or a properly built Dob + experience for smooth manual tracking, and an observer's chair. As even a slight jitter of the view at a high magnification when you are guiding could happen exactly at that split second when the view is truly cosmic at 800x magnification, so you may never even notice it's ever happened. I know many seasoned amateurs who never saw swirling clouds in the belts of Jupiter with their own eyes observing it for many decades just because they were blindly following the "2D rule of thumb" and didn't want to do the observing work looking just for an immediate eye candy treat.

2x130mm (= 260x) corresponds to the 50xDinch. How? because 1inch is approx. 25mm => 50xDinch/25mm = 50/25xDmm = 2xDmm. While 307x to 60xDinch. so it will correspond to metric 2.4xD, i.e. 2.4*130 = 312 (307 is just more precise inch/mm conversion as in fact it should be 2.362xDmm) (perhaps, you started answering when I've been adding the 307x test to my post above; check it out again if still confused). Re terminology: I'm not a linguist, but "Great Britain" on the road sign means "the Great Britain is ahead". While "unpaved road" sign means "an unpaved road is ahead". No? Even the words capitalization is just a random feature in your Celestron quote? I'm not a native speaker as you have probably noticed already , but the technical terminology logics behind the quoted Celestron technical specifications sheet is clear to me.

That's nothing to agree or disagree with as it's not "a highest useful magnification" but "The Highest Useful Magnification" Which is just a long settled telescope specifications terminology: "The Highest Useful Magnification of a telescope equals the telescope primary aperture diameter in inches multiplied by 60". More modest China scope manufacturers knowing their poor quality and afraid of claims had it modified to "... by 50" (just kidding ), which corresponds to 2xD mm. Just to quote it with more explanation: https://www.astronomics.com/info-library/how-to-pick-an-eyepiece/highest-useful-magnification/ And the test: 307/60 = 5.117", * 25.4mm = 129.97mm So, as I have already mentioned above, very high magnifications are working with small(ish) instruments. You just have to be very prepared, extremely observant, patient, and observe often to actually catch these rare occasions.

Gotcha. You are correct on the latter. My point is just that having same magnifications as your eyepiece is already providing being repeated with the 2x Barlow on half of the Zoom EP range is not beneficial in any way as no-Barlow views will be better (at every duplicated by the 2x Barlow magnification) and can be perceived as the 1/2 of the Barlow's price waste 3x Barlow cannot provide same magnifications as that 9-27 Zoom EP. So no duplicated magnifications, zero waste. Thus still: if planets (or other bright compact objects i.e. PNs, as well as Moon and Sun) magnification is the goal of bumping the zoom with a Barlow, I'd go with the 3x here and only here no single doubt. These minor FOV variations doesn't matter much for that if at all. Especially as the scope is on the GEM with "micrometers".

You are right about California, Steve. The pristine sky is not that rare here in comparison. However, I spent 20 years of my "amateur career" at the latitude of London (Russia, Novosibirsk). Great sky is possible there too (I understand on an island it's even worse, but still). Yes, maybe just once a year, and maybe just for a couple of seconds. But if that's happened to be a Jupiter's view, even a 110mm reflector views are breathtaking then, an I remember a dozen of these down to split second on planets still, 20+ years later. By the way, the Astromaster 130 which bandsman has is a 1:5 reflector actually not a 102mm refractor you are using as an example. Sure thing, the bottom limit for planets is a 150mm, but 130 is already very close to bet on 2.5D zooms with it. At any rate, with a 3x barlow there is nothing to lose, while anything else will be just a wasted redundancy with that particular Zoom eyepiece (not necessarily so with a random set of fixed eyepieces indeed). Regarding the AFOV, it's actually expanding as you zoom in, so with a 2x Barlow (with intersecting zooms) you will have a smaller field at the same magnification as without Barlow (which is a nonsense to do or desire).

Your focal is 650mm, so 9 - 27 zoom = 72x - 24x I'd rather go with a 3x Barlow which will give you exactly the missing higher mags range: 3 - 9mm = 216x - 72x The max magnification for a cheap instrument is indeed 2D (Heather is right) but if you are lucky your mirrors might be from a better batch, so under ideal sky you can push to 2.5D (~300x). I do even higher (2.75D)! The 3x is most viable anyway why would you want intersecting magnifications afterall? Don't bother getting an expensive one for a 3x, just avoid total nonames. E.g. a $40 Meade 3x would be totally adequate.

Rule No.1: Dark adapt your eyes for at least 15 min first.

Simple. UK and EU have an International airport like in every neighborhood, and it's hard to tell when one neighborhood ends and another starts. Few thousands years of development are incomparable with just a few hundreds in the US

Re optical finder alignment. Surely the best alignment target is Polaris (or any other bright star when you learn to work fast to ignore the celestial drift). However, terrestrial targets can be totally adequate if you simply adjust the process for the parallax. In a nutshell, after pointing the telescope to a feature on a terrestrial target (e.g. a corner of the brick on the mentioned above chimney) point the finder away from that feature with an offset equal to the offset and direction of these two optical axes difference as if they are drawn on that chimney (surely you should know the brick and gap size, but a sane estimation is usually enough). That's also the way to figure if aligning on a particular terrestrial target needs any adjustment at all (if the needed offset is impossible to figure looking through the finder, that means there is no adjustment for the parallax required at all). Another crucial consideration should be made for the actual pointing technique with a particular optical finder. The crosshairs in various models are different in features so no universal advice (the cross' thickness, orientation, subtle crosshairs manufacturing features you could leverage...). E.g. on my 8x50 RACI the cross is enormouslysly thick, so stars are passing behind it for like a minute. That means you can't actually point with it precisely enough to always hit the target with a high mag narrow AFOV EP. The common advice is to point with low mag EP first to amend these issues, but that adds other issues for a novice (overcrowded FOV). However, instead of guess-centering the cross over the target and then hoping that semi-bright star on the edge of the FOV is what you are centering, you can point much more accurately with the particular cross' corner instead. E.g. the topmost one (on my 8x50 I simply disassembled the EP, scratched the paint on one of the cross lines near the center with a needle, and got a decent sharp point in it to align with targets much more accurately, that's especially useful on mine as it's easy to rotate in the holder so I'm often using that feature for outreach for manual planets guiding standing on the other side of my Dob at the finder EP with the guest at the main EP to avoid us jumping around; despite the huge magnification difference it works tolerably even at 200x ). Also, keep in mind that optical finders might have a significant parallax as well in case the cross and the target are not in perfect focus. Cheap finders often have a focuser for the objects, but nothing for the crosshairs. So when focusing the finder focus your eye on the cross first, then focus stars keeping the cross focused. In a worst case (no way to bring both into the same focus plane and eyeglasses are not an option) use the "eyeballing" technique to amend that to some extent: Center your focused star on the crosshairs and now move your head around a bit so the eye looks through the EP at the crosshairs at different angles. You will see it moving around the star. That's the parallax due to difference in their focal planes. The idea is to find the center of that circle, stop "eyeballing" at that center of it and move the scope so the target star is under the crosshairs there. And finally, the tip for the scope alignment accuracy improvement using a bright star: Just defocus it. The eye is much better distinguishing the perfect concentricity than the perfect centrality. So having the alignment star in the eyepiece view looking like a large disk (donut in a reflector) it will be much easier to ensure the telescope is perfectly centered on the star by keeping its edge concentric (equally spaced) with the EP field stop (warning! not working with 100 deg AFOV EPs well ). The same can be used with the optical finder, but instead of concentricity watch for the defocused disk to be equally split by the cross, as some crosses might be not exactly centered in the FOV (surely only if your finder is easy to refocus as some are easy to knock off from just trying that). By the way, the "by the crosslines feature" pointing technique above is applicable to ordinary RDFs too, as they often having an irregular red dot. E.g. I once had an RDF which dot looked like a tiny angled stick (narrow ellipse actually). No biggie, even beneficial as I found pointing by placing targets on its sharp top end highly accurate. Telrad, QuInsight, and Rigel obviously much better at that as they have a tiny ring helping to center stars ideally by concentricity and without obstruction (just watch for the parallax error compensated by "eyeballing" if it's significant in your device).

That's exactly why we have this conversation. The proper RDF is way better for direct naked eye pointing than any magnifying finder. And that "Gunsight" above so far seems to be the best bang for the buck on the market (all aluminum, by the way). The only issue to some is that it's a gunsight, so it will require you to take care of its proper mounting. E.g. 20 years ago I simply hand-filed a piece of aluminum to this: My ETX-125 with handmade aluminum dovetail between the OTA back cover and the gunsight (right top) I have it clamped down forever as it is very compact, but you can hunt for the real Picatinny rail and a quick release riser. E.g.: They are usually all aluminum, reproducing the collimation not only from day to night, but also after 12ga magnum slug BOOM (even 100 of those )! As well as after removing and replacing it, and can be found waaay cheaper than astronomy vendors' offerings.