2024 Solar Eclipse (Gatesville, TX): A tale of two coronas

May 5, 2024 // by ecuador

2024 Total Solar Eclipse inc. HDR, 2 coronas

After my 2017 Solar Eclipse experience, I had told myself that I would try to catch all future totalities in the US or Europe and April 2024 was the next one. I had chosen Texas a few months earlier because it statistically offered the best chance of sunshine. As luck would have it, when time came, Texas was the worst place to be, with high clouds covering the entire State and fast moving mid/low clouds in most places. I started off from Austin in the morning having marked 2 possible locations towards North and North East and when it was time to make the choice while driving, the weather radar showed a ranch near Gatesville, TX as having the best chance.
I set up my automated photography rig – I had my trusty Canon 800D, but I got a new super portable SharpStar 61EDPH-III triplet for the occasion along with a SkyWatcher AZ-GTe mount/tripod. A laptop running Eclipse Orchestrator was programmed to take about 200 photos by itself (most in brackets covering from 1/4000s to 1/2s). I’d be enjoying totality with my own eyes and binoculars. All I needed was for the clouds to not be in the way.
And they were not (completely) in the way; they sort of gave us a good opening for the start of the total phase and then for a significant portion of it. It was glorious, the dozen or so people around me were ecstatic (you can hear them in the video above), and having had my previous experience under clear skies, it was interesting to get something “new”, including an optical phenomenon called “corona”. Yes, it’s the same name as the Sun’s atmosphere, but it’s an effect caused by water droplets in the clouds refracting the light to produce a sort of rainbow around the sun. So most of my photos have 2 different coronas visible! Starting with the diamond ring shots:

Diamond Ring / Baily’s Beads

Diamond ring
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Polar Scope Align Pro v6.8 released for iOS!

April 16, 2024 // by ecuador

Alt-Az field rotation

WHAT’S NEW v6.8:

– Added Alt-Az Field Rotation calculator.
– Barlow/Reducer option added to 6 calculators (Eyepiece Magnification, Eyepiece Projection Focal Length, FoV for Imaging System, Actual Size of Lunar View, Eyepiece Field of View, Arcsec/px for Imaging System).
– Updated Sat24 and Clear Sky Chart locations for Xasteria Weather. (Pro)

More info on Polar Scope Align on the dedicated page.

Download on the App Store

Free Version

Download on the App Store

Pro Version

Download on the App Store

Pro Watch Bundle

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Polarie and Star Adventurer Daytime Alignment Setup

April 1, 2023 // by ecuador

Polar Scope Align‘s Daytime Alignment tool is easy to mount on traditional equatorial mounts – just put the phone on the saddle (preferably with a dovetail extension) and you are set. Users have even made 3D printed dovetail holders:

However, the way the Vixen Polarie, SkyWatcher Star Adventurer and other star trackers are designed, there is no obvious way to mount the phone for Polar alignment so that you can guarantee it is parallel to the RA axis, although it could possibly be done with an attachment to the shoe mount, or even with an L-bracket. Here are some ideas on which you can build on for the two of the most popular trackers:

Vixen Polarie

Polar Scope Align Pro user Noriyoshi Hashimoto (橋本 憲良) kindly send me the procedure he uses to get up to 60sec exposures on 200mm using an L-bracket:


Level the tripod head, but setting the phone on top of it and using PS Align pro’s Bubble Level tool:

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Cheap Push-To for your Dobsonian with Polar Scope Align Pro

September 6, 2020 // by ecuador

Version 5.1 of Polar Scope Align Pro came out recently with a new feature designed for manual mounts (mainly with Dobsonians in mind, but also for manual alt/az or EQ): Attach your phone parallel to your mount, select a target and Polar Scope Align Pro will help you push your manual mount towards the target. Because phone compasses are very sensitive to local magnetic fields (like those produced by metal mounts, telescope tubes), the app offers a “Hop To” function, where you first find a bright star and center it so that the app can calibrate to get to the desired object with good accuracy. Rob Pettengill helped me develop the feature, testing it with his Questar and Dobsonian, so it is worth reading his report on using the feature, with ideas about mounting it etc. Here is the app mounted on his Questar:

Celestron, iOptron, Losmandy, Orion, Sky-Watcher, Vixen telescope mount comparison table.

July 13, 2020 // by ecuador

Update July 13 2020: :Long time coming update, apart from price updates, we have the Celestron CGX and CGEM II replacing CGEM, new iOptron mounts GEM45, CEM40, CEM70, Losmandy GM811G, SkyWatcher EQ6-R Pro, EQM-35. Losmandy G11 & SkyWatcher EQ8 are now on the mid/high-end mount page.

Price update Jan 9 2017: Some price updates. A few impressive price drops, the CEM25 in the UK (£699 from £899), the Orion HDX110 ($3505 from $4499!) and CGEM DX in the US ($1695 from $1999), otherwise mostly price increases in the UK, due to the $1=£0.82 exchange rate.

Note Oct 3 2016: After over a decade of listing the HEQ5 as 15kg payload and the EQ6 as 18kg img/25kg visual, Skywatcher has downgraded the capacities of these mounts as 13.7 and 18.2 respectively. To me it looks like a marketing idea to differentiate the more expensive AZ-EQ5 and AZ-EQ6, so I am keeping the listing as it was, at least for now.

Update Sept 19 2016: I added the three smallest/least expensive mounts (SmartEQ, EQ3, EQ5) just to be more complete, although they don’t really compete with the rest in astrophotographic capabilities. Prices are updated, mostly the weaker GB pound made some UK prices – especially Vixen – higher  (with the notable exception of the CGEM DX which dropped dramatically). I added a separate price graph for UK, it has an extra mount compared to the US graph, as the EQ3 Synscan doesn’t seem to be sold in the USA (you can find it in Canada though).

There was a UK store that had a nice table with the basic specs of Sky-Watcher and iOptron which I had found quite useful especially to see at a glance which mount from a company was at the same category with what mount from the other. That page is no longer online, so I thought I’d compile my own table and try to include more and newer mounts. I’ll only include computerized EQ mounts from comparable/high volume manufacturers (under $4000), so no expensive Astro-Physics, Takahashi etc (but you can find all those and more mid-high end mounts on this comparison table here).

The specs were mainly lifted from the manufacturer page, except the peak to peak Periodic Error which is shown as a range (with before / after Periodic Error Correction values) from various reports (this source was helpful, also this and some of this – although may be less reliable – as well as numerous CN threads with PEMPro, PHd2 etc graphs). Note peak-to-peak error is twice the +/- values that are sometimes used and some extreme cases were not included. Also not included are values of 1-2 arcsec reported for some mounts (iEQ45, G11) with TDM. Payload normally means visual (apart from where noted) and sometimes I had to choose a source (e.g. Skywatcher and Orion give a bit different spec for the exact same mount). iOptron CEM mounts come in more expensive “EC” versions that include encoders for better unguided performance, they are not included as they only change pricing/PE and most other mounts do not include encoders. Prices are typical US & UK prices with basic tripod included (unless noted).

Manufacturer / ModelPriceMount Head (kg)Payload (kg)Resolution (arcsec)ObjectsPolar ScopeGPSPE/PEC (arcsec)Prede-cessor
Celestron AVX$899/£7797.714N/A40000-130/8CG-5
Celestron CGEM II$1649/£149918.218.2N/A40000-1CGEM
Celestron CGX$2299/£214519.418N/A40000-110
iOptron SmartEQ Pro+$499/£3852.8 50.5150000Yes230-60SmartEQ
iOptron CEM25P$898/£7254.7 120.14150000Yes2Yes<20ZEQ25
iOptron iEQ30 Pro $1198/£12856.8 140.14358000Yes2Yes16/5iEQ30
iOptron CEM40 $1998/£1690 7.2180.08358000Yes5Yes<14
iOptron GEM45 $2098/£1849 7.2200.08358000Yes5Yes<14iEQ45
iOptron CEM60$2398/£2299* 12.3270.06359000Yes5Yes8-16/1.5
iOptron CEM70$2548/£2349*13.6320.07359000Yes5Yes<7
Losmandy GM8 G$2495/£29889.516***N/A40000-313-20/8
Losmandy GM811G$2895/£339012.2 22.7***0.1440000-3
SkyWatcher EQ3 Pro Synscan (Orion AstroView Pro)-/£3994.25.5?42000-4>80
SkyWatcher EQM35 Pro$725/£5494.4100.28142900Yes60EQ3
SkyWatcher EQ5 Pro Synscan (Orion SkyView Pro)$699/£5696.29.10.28842000-4>60
SkyWatcher AZ EQ5-GT (Orion Sirius Pro)$1299/£10297.7150.2542000-416-40/?
SkyWatcher HEQ5 Pro (Orion Sirius)$1099/£78910150.14442000Yes220-50/6-7
SkyWatcher AZ EQ6-GT (Orion Atlas Pro)$1999/£139915.425**0.14442900Yes225-30/8
SkyWatcher EQ6/NEQ6 Pro (Orion Atlas)$1399/£10491625**0.14442900Yes220-50/6-7
SkyWatcher EQ6-R (Orion Atlas II)$1599/£119917.320***0.1442900Yes212-30/5-7EQ6
Vixen SX2 (+SB10****)$2199/£2048712***N/A270000-3?/?
Vixen SXD2$2659/£22709.215***N/A270000Yes227/?
Vixen SXP$2999/£29991116***N/A270000Yes2?/?

*Does not include tripod.
**Orion rates these at 18kg, Sky-Watcher at 18kg imaging / 25kg visual, so we use the specifically “visual” number.
***Value is for imaging load, so probably more modest than the rest.
****The SX2 comes with the Star Book One as standard. The Star Book Ten that provides goto is added to the price to match the list’s minimum spec.
Polar Scope Notes:
1. Optional non-illuminated available.
2. Illuminated Polar scope comes standard.
3. Optional illuminated available.
4. Optional non-illuminated available that attaches externally.
5. Electronic (iPolar – requires computer) included.

Let’s make some charts. We’ll start with the Payload vs Mount weight:

A y = x/2 line is drawn and there are actually several mounts below it, most from iOptron (plus the new small SkyWatcher mount), meaning they can lift more than twice their weight. The Celestron mounts are rather disappointing, although the new version of the CGEM, finally claims to “lift” at least as much at it weights, although Celestron may be a bit modest about their payload spec. Note that the EQ6-R is not disappointing, as its “photo”
payload is listed versus “visual” for most others.
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Mid-high End ($3-15k) Telescope Mount Comparison Table

June 30, 2020 // by ecuador

  • UPDATE 2020-06-30: I guess it was time for an update, the main changes are the Mesu Mount 200 MKII (instead of the original), the Gemini E.fric instead of the G53F, the Astro-Physics Mach2GTO instead of the Mach1 and the Celestron CGX-L instead of the CGE Pro. The iOptron CEM120 and SkyWatcher EQ8 were added to the mix, as they were closer to this tier. Several price updates too.

I while ago I made a comparison table for mass-production mounts under $5k and some nice charts with its data. Since I was recently looking at the mid/high end mount category, which is even less straightforward, I thought it would be interesting if I made a similar table. So, this time nicer small mounts like Takahashi and Astro-physics are included, along with observatory-grade mounts up to $15k and 100kg capacity. There’s a Celestron, a Meade, a SkyWatcher and an iOptron thrown in because they didn’t fit the other table, but otherwise this listing contains superior quality mounts and thus things like mount capacity are not comparable the other table, as high end manufacturers tend to be very conservative with their numbers, quoting “realistic” imaging loads. As before, the specs were mainly lifted from the manufacturer page, except the peak to peak Periodic Error which is shown as a range (and also before / after PE Correction values separated by a “/”) from various reports (this source was helpful also this and numerous CN threads).

The table will not tell you which mount to buy obviously, but it should be useful to see at a quick glance what kind of competition there is in your desired category. The prices are current at the posting of this article, but don’t expect me to keep up with price changes, I will only update if the table becomes outdated overall.

Also, prices in this list are often just an indication, as they may exclude significant shipping costs/duty/tax – although I tried to find a price from a US or UK/EU seller where possible.

Manufacturer / ModelPriceMount Head (kg)Payload (kg)Hand-controllerPolar ScopePE (arcsec) / PE w. PECPEC
10 Micron GM1000 HPS$9196/£728519.525YesNo1Yes
10 Micron GM2000 HPS II$13969/£112003050YesNo1Yes
Astro-Physics Mach2GTO$8940/£997017.734YesOptional0.25Yes
Astro-Physics 1100GTO$7970/£886224.550YesOptional<7/1-2Yes
Astro-Physics 1600GTO$10870/£1210052100YesOptional<5/1-2Yes
Avalon M-Zero$4183/£32387.58YesYes, illum***No
Avalon Linear$5470/£427012.520YesYes, illum***No
Avalon M-Uno$6759/£528014.920YesYes, illum***No
Celestron CGX-L$3599/£35552434YesOpt, external?/4Yes
Fornax 52$4748/£39803550OptOptional16/<1*TDM
Fornax 100$6740/£59705080OptOptional16/<1*TDM
Fornax 150/100$9797/£909870100OptOptional12/<1*TDM
Gemini E.fric$3722/£32811830OptionalOptional?No
Losmandy G11G$3395/£356316.327YesOptional3.5-10/<1Yes
Losmandy HGM Titan$5995/£68003445YesOpt, external7-14/2Yes
Meade LX850$6579/£69652542YesNo8-16/3-7Yes
Mesu-Mount 200 MKII$5290/£514024.1**100YesOpt, external4.6/-No
Paramount MyT$5995/£65501523NoNo4-7/<1Yes
Paramount MX+$8995/£101002345NoOptional4-7/<1Yes
Takahashi EM-11 Temma-2Z$3350/£359079YesYes, illum7-20/-No
Takahashi EM-200 Temma-2Z$5210/£54251518YesYes, illum10/-No
Takahashi EM-400 Temma-2Z$9150/£957027.735YesYes, illum10/-No
Takahashi EM-500 Temma-2Z$13020/£147774545YesYes, illum7/-No
Vixen AXD2 (Atlux Deluxe)$7999/£71002530YesYes, illum?Yes
iOptron CEM120$3999/£32502652YesOpt, electronic<7****Yes
SkyWatcher EQ8-R$4080/£299925.850YesOpt, externalYes

* Fornax mounts don’t offer PEC, they do suggest you optionally purchase the TDM encoder system.
** The Mesu Mount 200 MKII head is technically 16kg, but the detachable 5kg wedge and 2.5kg counterweight bar were included for comparison with the other mounts that have them as part of the head.
*** The Avalon mounts by design have a very high (reportedly even over 50-60″ p-p), but very slow PE (with no PEC possibility), so cannot be used for unguided AP at any significant focal ratio. Their slow PE is very easy to guide, so they are popular mounts for guided AP.
**** The CEM120 also comes in two more expensive encoder versions (EC/EC2) which specify PE <0.15″ RMS.

So, as in the mass produced mount comparison, we start with the mount head weight vs payload capacity graph:

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3D-printable iPhone X dovetail holder!

October 1, 2018 // by ecuador

An industrious Polar Scope Align Pro user, Zach Hartman, shared with me photos of the iPhone X dovetail (standard “Vixen” style) holder he made to use with the app’s daytime alignment tool, which follows my suggestion of extending the phone away from the saddle to reduce effects on the magnetometers:

He also uploaded his design to Thingiverse, so that anyone can download it and print it:

Pretty cool, and hopefully helpful for people who are trying day alignment.

Polar Scope Align v4.0: new Watch extension

June 18, 2018 // by ecuador

Major release, especially for Apple Watch users, featuring a new Watch extension taking advantage of . A quick preview:

New Watch Features:
– Moon Phase view added to the first screen, moon/sun rise/set times on second screen.
– New (third) screen with the Xasteria weather report.
– Reticle zoom slider.
– Ability to switch mode (Polar Alignment, Bubble Level, Day Alignment, Moon Phase) from the watch.
– Day/night mode switch on the watch.
– Watch type is now automatically detected (manual setting removed)
– Better refresh rate for Bubble level and Day alignment.

Best astronomy apps for iOS (iPhone & iPad)

June 2, 2018 // by ecuador

I will try to list a few of my favorite astronomy apps for iOS. Caveat: I will have to start with a couple of my own apps, since by definition (being designed by myself, exactly as I wanted them), as far as I am concerned they are the best at what they do, so I cannot objectively rank them among others. Hopefully you will forgive that little bias. In any case, this is not a definitive list, I may add (or remove) apps as new apps or new versions come out.

Polar Scope Align

Current price: FREE (Basic), $1.99 (Pro), $3.99 (Pro Watch)

Thousands of users turn to Polar Scope Align for their polar alignment needs, and with good reason – it supports probably every polar scope used in the field including ones from iOptron, Astro-Physics, Takahashi, Orion, Celestron, Meade, Vixen, Astrotrac, Losmandy, Kenko, Avalon, even early 80’s designs like the Tuthill, or finders like the Telrad. Basically, if you have a polar scope that is not supported, contact me and with some help (e.g. images), I will add it. What’s more, for many of these polar scopes, especially the less precise ones, if you read the in-app instructions you will discover that Polar Scope Align offers you an alternative method of aligning with them to improve their precision.

And all the functionality for polar alignment with all those polar scopes is included in the free version. But there are also the Pro and Pro Watch versions which add tools that I like to use for my astrophotography session: From weather and bubble level to calculators and a Deep Space Object database. The latter is not actually a very well known feature of the app, as it is not very related to polar alignment, but it is probably the feature I use the most in an astrophotography session. Take a look at the video below for a lesser known Deep Space Object database feature that I use often.

PS Align Pro: Finding astro targets by pointing to the sky.

Read more about Polar Scope Align.

Download on the App Store

Free Version

Download on the App Store

Pro Version

Download on the App Store

Pro Watch Version

SkySafari 6

Current price: FREE (Basic), $14.99 (Plus), $39.99 (Pro)

Most people consider SkySafari to be the best astronomy app overall and, well, they are probably right. It starts out as an excellent planetarium-type program in its Basic (currently free) version, and continues on to be a space-simulator and telescope control software in the Plus/Pro versions. The only gripe I’ve heard about this app is that you have to pay to get a new major version, although it is in any case worth the functionality you pay for at the time, even if it means they might make a better version in the future that you can’t upgrade to.

So, the Basic version does the base planetarium-type stuff that a few other (sometimes free) apps mostly do as well, although it is a solid implementation and easy UI which makes it rank towards the top of this category. If it is free, it is a no brainer. However, the most popular version of SkySafari is probably the “Plus” version. It adds a bigger object database, observation planning tools, object visibility graphs, space-simulator abilities and telescope control. Most amateur astronomers won’t need anything more, but there is also a more expensive “Pro” version which adds the ability to get extensive object databases (like PGC galaxies).

Download on the App Store

SkySafari Basic

Download on the App Store

SkySafari Plus

Download on the App Store

SkySafari Pro

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Daytime Polar alignment iPad setup

February 7, 2018 // by ecuador

Michel Moreau, a user of Polar Scope Align in France sent me his very elaborate iPad daytime polar alignment setup a while ago, but I never got around to post it, so here it goes now:


I have an older iPad which does not have a good magnetometer, but he tells me he is happy with his setup (and it looks cool too!) and he kindly shared his plans for both a 9.7″ and a 10.5″ iPad Pro (descriptions in French only – sorry) which you can download here. Thanks Michel!

2017 Total Solar Eclipse @ Madisonville, TN

August 31, 2017 // by ecuador

About 25 years ago as a kid I had looked up future total eclipses and had marked the 2017 eclipse as the one I would see. I’d be old enough to travel when I please, it would be summer and it would be at a location that’s easy to go to (I visit the US regularly). As it often happens, I wasn’t really going to honor my childhood plans, I had a rather busy summer, until, about a month before the eclipse I suddenly said, hey, why the hell not? I called up my cousin in Baltimore, asked him if he was up for an eclipse road trip to somewhere around Tennessee/North Carolina, and, as they say, the rest is history (images enlarge when you click them):

8-frame HDR composite, Canon 550D /w Equinox 80ED

The location

I tried to stay at Knoxville, but ended up in nearby Pigeon Forge due to trying to book too late. The plan was to look at the forecast and head to one of a few sites I had looked up, the closest being Madisonville, TN and alternatives like Hiawassee GA or TN beyond Nashville. As luck would have it, Madisonville had the best forecast and we headed there (2m 38s totality). The town had arranged a big party at Kefauver park, about 5 miles from the town center. We, along with about 200 people ended up at Not-Kefauver-park, a smaller park in the center of the town, having only read the big letters “Kefauver park” on a helpful sign at the smaller park (that apparently went on explaining how to actually get to Kefauver park – the town had even set up buses to take you there). To our defense the town’s online advertisement said “Houston Park”, so that’s what we had tried to locate on our GPS. Well, the weather was great, our toilets did not have long lines and I met some very nice people, so I can’t complain!

The setup

I had brought with me from the UK my trusty Canon 550D, the Equinox 80D – my most portable OTA, and a Skywatcher Star Adventurer I had picked up just for the trip, which sat on a heavy duty tripod I borrowed from my uncle. Daytime alignment with Polar Scope Align Pro was of course a breeze and gave excellent tracking. In the above image you can see some weird bubble wrap which was a last-minute modification once I realized I had with me the wider Baader Astrosolar ND5.0 film mount (from my Evostar 80ED). I also had an ND3.8 Baader photo film which went to my cousin’s Nikon 300mm lens, and an Acuter Innova 10×42 pair of binoculars with Thousand Oaks filters. The plan was to have the camera on the telescope controlled by my laptop running Eclipse Orchestrator, so that it takes the exposures I had programmed (about 100 around totality) while I enjoyed the eclipse. I had the only telescope in the park and, being my usual helpful self, I had it set up for viewing so that people can enjoy the partial phases (quite some sunspot activity), so I only switched it to the camera quite late as can be seen from this sequence that starts with the first partial phase I was able to take:

Single Shots

This is the first exposure attempting to capture the diamond ring, getting a lot of glare with a longish exposure:

Shorter exposure:

Bailey’s beads:

Near midpoint:

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Daytime polar alignment (for the 2017 Solar Eclipse of course!)

August 14, 2017 // by ecuador

If you are going to try and capture the solar eclipse with an equatorial mount, you are probably concerned about how you are going to do the polar alignment (unless you are lucky enough to be able to set up the previous night).

Sky & Telescope seems to have popularized a method which uses a planetarium-type app in your smartphone in order to see where your polar scope points. The setup for an equatorial mount looks a bit like this:

There is some slight problem with this setup… IT DOESN’T ACTUALLY WORK! At least not as described…

I don’t know what kind of magical phone Sky & Telescope used, however when I approach a metallic object with any of my phones, the magnetometer goes wild. In the above image (similar setup to the popular article) it was off by 5-10 degrees. If I put it flat on a metal surface like the images I saw with a wedge mount, it would probably go much more. So, to use this method you have to take your phone away from anything metal. Something like that though, would probably be easier with a different method altogether… Enter the latest tool I made for my Polar Scope Align Pro app:
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Lunar mosaic in UV, L, IR with an Altair GPCAM2 IMX224

April 9, 2017 // by ecuador

I had my first imaging session with my new Altair GPCAM2 IMX224 last Friday – until then I had only used it for guiding. Since I was going for the moon with a small sensor, I would have to do a mosaic, even with the relatively wide field Skywatcher 130PDS. But I thought I’d go even further, getting a set with the camera’s standard UV/IR filter, a set with a 630nm IR-pass and a set with a Venus U. Combining them R=IR, G=L, B=UV gave this interesting lunar rendering:

It is not a “true” UV/L/IR, in the sense that the GPCAM2 has a color sensor, so even with its UV/IR filter removed it can only record the very near-UV spectrum (realistically only down to around 380nm or so), so for a bit more of UV you need both a newtonian reflector with no barlows/reducers etc, and an unfiltered mono sensor that is a bit UV-sensitive (a Sony/Kodak usually is, an Aptina is not).

It is worth giving a quick description of the two main techniques involved in producing images like the above: Lunar mosaics, and RGB/Channel compositing.

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Review: From the ZEQ25 to the iOptron CEM25P

January 29, 2017 // by ecuador

If you have read my review for the iOptron ZEQ25, you might remember that I was very happy with the mount. You might also remember I had mentioned there was an updated version called the CEM25, which was the same mechanically, but had updated electronics & stepper instead of servo motors. Well, a month ago I gave in and ordered the CEM25 from the UK distributor, Altair Astro. What I received though, was this:

Enter the CEM25 update, unannounced at the time I received it, the CEM25P. Apart from the “P” in the logo, you can tell it apart from the CEM25 by the bolt handles which don’t have the central white dot.
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