WHAT’S NEW v4.2:
– Added Explore Scientific 8×50 RACI PolarFinder.
– Updated reticle help.
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.
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.
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).
-The main Xasteria weather service (7Timer!) will now be more reliable, as a brand new Xasteria-funded US-based server is up and running. This version tries that mirror first.
-The NOAA water vapor page got an update, as there was a satellite replacement: GOES-13 (GOES-East) was retired and GOES-16 is now up in its place.
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!
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):
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!
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:
This is the first exposure attempting to capture the diamond ring, getting a lot of glare with a longish exposure:
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:
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.
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.
For some reason, mount manufacturers give you azimuth adjustment bolts that are not easy to grab (in the usual freezing temperatures) and don’t have much of travel to allow you for a significant adjustment. There are some replacements sold at rather obscene (for a pair of bolts) prices, so I had bought inexpensive HEQ5 replacement bolts from an Ali Express seller a while back for me and my friends, and now I see pretty much the same bolts, with a very nice grip and decent length (50mm) on ebay for just £2.69/pair or £7.28/10pc (although you’ll have to wait a couple of weeks for them to arrive). They look like this:
When I got my first 127mm Maksutov, I had not done my research and so I was a bit disappointed by the maximum possible field of view it could provide. You see, its baffle tube diameter was 27mm, which is the same as the maximum field stop for a 1.25″ eyepiece, so even with a reducer I could not get more FoV than what a 32mm Plossl provides – which is not much at a 1500mm focal length (1.03 degrees). A wider baffle tube allows you to either use 2″ eyepieces that can have a larger field stop, or a reducer without vignetting.
In the following table, I have used the baffle tube diameters from the Celestron knowledge base to calculate the maximum field of view for each of their Catadioptric OTAs (if you want to do it yourself, the formula is 57.3*field stop/focal length). The Maksutov numbers should also be valid for the Skywatcher and Orion models. I also list the eyepiece that will provide the maximum field of view without vignetting. In the case of the C11-C14, their baffle tube is larger than the maximum possible field stop for 2″ eyepieces. In the case of the C90, the tube is tiny in diameter, but not very long apparently so if you don’t mind vignetting you can almost go to the 1.3° that Celestron advertises with a 32mm Plossl.
|OTA||Focal Length||Baffle Tube||Max FoV||Example Eyepiece Max Fov with no vignetting|
|C90 Mak||1250mm||15mm||0.69°*||25mm 50° Plossl|
|C127 Mak||1500mm||27mm||1.03°||32mm 50° Plossl|
|C5||1250mm||27mm||1.24°||32mm 50° Plossl|
|C6||1500mm||27mm||1.03°||32mm 50° Plossl|
|150 Mak||1800mm||30mm||0.96°||ES 70° 25mm; Panoptic 27|
|C8||2032mm||37mm||1.04°||Panaview/SWA 32mm; ES 68° 34mm; Ethos 21|
|C9.25||2350mm||46mm||1.12°||Panaview/SWA 38mm; ES 68° 40mm; Panoptic 41|
|C11||2800mm||54mm||1.1°||0.94° /w 2" Panaview/SWA 28mm etc; 1.07° /w 3" ES 100° 30mm|
|C14||3910mm||54mm||0.79°||0.67° /w 2" Panaview/SWA 28mm etc; 0.77° /w 3" ES 100° 30mm|
*Due to the short tube you can apparently reach 1.3° using a 32mm Plossl with some vignetting.
As you can see, one more reason I like my C9.25 is that it can give you the maximum apparent field of view possible for a 2″ eyepiece (which goes up to a 46mm field stop), so it can actually provide a wider true field of view than either the smaller C8 or the larger C11. The C11 and C14 can take advantage of eyepieces larger than the 2″ standard to go closer to their max field of view, but you’d have to find an external focuser to take an eyepiece such as the 3″ Explore Scientific 100° 30mm.
APO/ED refractors are great, however they do need a flattener to give you those pinpoint stars, or, even better, a reducer/flattener to also give you faster exposures and wider field at the same time. Some refractors will have a matched reducers (especially the “slow” ones), but, for those that do not the expensive TeleVue TRF-2008 is often recommended. I thought I’d test how it actually performs using the two ED doublets I have right now, the 600mm f/7.5 Evostar 80ED and the 500mm f/6.25 Equinox 80 ED, and pit it against an inexpensive Altair Lightwave 0.8x that had gotten me curious for a while now (it looks a bit like the Orion 0.8x – no idea how similar they are).
|Reducer Model||Reduction: Spec / Actual||Weight||Compatibility||Price|
|TeleVue TRF-2008||0.8x / 0.785x||347g||400-600 focal length||$305 / £306|
|Altair Lightwave 0.8x||0.8x / 0.801x||170g||f/6+||£75|
A popular guiding solution is the 50mm guide scope, often by converting an existing 9×50 finder scope. It has the advantage that it is light, it can fit on your existing finder shoe, it is very fast giving you many stars at low exposures and it can be quite effective at short and medium focal lengths. After getting a bit frustrated with a couple of OAGs (off-axis guiders), I looked into adapters for converting the classing 9×50 finder, however they were very expensive for what they are, and, as I found out, for a little more you can get a dedicated guide-scope that should be better suited to the task. I got two units sold by “Solomark”. Well, I got one unit actually, it was very competitively priced, came quickly, but it was the wrong one! It was obviously an honest mistake as I received a more expensive unit, but I had not read good things about guiding with helical focusers, hence I wrote them and they immediately sent me the one I ordered and told me to keep the more expensive one, so that was some great service from Solomark. But, you will also find these guide-scopes sold under various names, sometimes with minor differences and for varying prices. Let’s have a look at them:
If it seems familiar, that’s because it is identical to the Orion 50mm mini guider (including all the accessories that come with the Orion). In fact, my unit came marked as “Starguider”, which is how Agena brands their own version, and there is also a TS (Teleskop-Service) version. The optics look good and construction is metal except the 3 adjustment screws, but relatively light at 496g including the stand which fits snuggly on the usual skywatcher/celestron etc finder-scope shoe (a shoe is also included if don’t have one).
Focusing is a bit awkward: you focus roughly by manually sliding your camera into the tube as much as required and tightening (you can attach the provided parfocal ring to not have to repeat this) and then you can adjust a bit by rotating the front part which can move the objective by a few mm. Due to this limited focus travel, to focus with an eyepiece (i.e. to use this as a regular finderscope) you need a small extension. I also tried a 1.25″ diagonal, but that added too much distance so I could not get focus with an eyepiece, so you are quite limited if you expected to swap the camera with an eyepiece now and then.
I don’t see a way to remove the guide scope from the holding bracket (in case you wanted to upgrade the bracket or the scope) and the 3 adjustment screws provide very little travel, although I doubt you’d have a problem finding a guide star with a decent guide camera.
The specs claim 162mm f/3.2, however plate-solving with a QHY5L-IIm camera gave me 183mm. This is actually a bit more useful, as at f/3.66 it is still really fast, but the extra focal length is welcome.
Where to buy: Right now I see the Solomark out of stock, but you can get the Orion version at a decent price from Amazon.com or Amazon.co.uk. There is also the StarGuider version on ebay.com.
Right from the start, I liked the smooth, graded helical focuser that makes focusing very easy, a big advantage over models without one. In fact, apart from the helical focusing travel, the focuser has a telescoping drawtube (also graded) which allows you to reach focus easily even with an eyepiece – no need for an extension. Some people claim helical focusers can add flexure, so we’ll have to see about that. The optics look good (real 50mmm unobstructed aperture) and the build is solid, even the front cap is metal (no focuser cap though, strangely), except the nylon screws – although it seems quite sturdy I have heard some cases where nylon screws added flexure, so that’s an additional concern. The total weight of base & optical assembly is 590g.
Now there is a small issue with the dovetail. While you’d expect it to be the same size as the usual finderscope base, it is, in fact, a few mm thinner. This has the effect that some bases with relatively short screws (e.g. the standard finder shoe on the SkyWatcher Evostar 80ED) can’t reach it to secure it. A longer screw fixes the problem (and some shoes, like the one on my SkyWatcher 130PDS, don’t have an issue to begin with).
The specs claim “190mm f/3.4” (which does not exactly compute with a 50mm aperture), and plate-solving with a QHY5L-IIm camera gave me a close enough value of 182mm focal length, which makes it a very fast f3.64. There is also an “F60” model, which is the 60mm version.
Where to buy: You can get the F50 on Amazon.com or Amazon.co.uk. You can get cheaper unbranded versions from China on Ebay, although I can’t vouch for any specific seller. You might be tempted to also look at the larger F60 at Amazon.com or Amazon.co.uk, although I haven’t tried it myself.
I have several barlows in my possession, some came part of larger purchases (a Celestron 2x and a Skywatcher 2x), some where bought when I wanted more than 2x at good quality (High Point Scientific 2.5x, TeleVue 3x, TeleVue Powermate 5x) and some because I was just curious what you could get for cheap (no-name 3x ED, 5x Datyson). Having tried them all, I ended up only using 2-3 of them and I guess it would be good to share my experience with others especially so that they can see what an inexpensive barlow can get them, especially compared to the standard all barlows are usually compared to: the TeleVues Barlow or Powermate.
From left to right: TeleVue 3x, 3x ED, Datyson 5x (top), SkyWatcher 2x (bottom), High Point 2.5x, Celestron 2x (top), TeleVue Powermate 5x (bottom)
Using a DSLR camera for astrophotography has you dealing with quite noisy data, and the issue is compounded if you are shooting from the city under light-polluted skies. Noisy data gives you a hard time when processing, so it would initially take me quite some time and effort to get to pleasing results, even with dedicated software.
StarTools has made my life much easier as it does many things that require many manual steps in other software almost automatically, allowing me to get decent results from an image in just 10-15 minutes. You can always tweak some more of course, but the example process I am going to demonstrate on this post will get you to the following result in just a few minutes:
Until recently Amazon allowed sellers to give (for free or a deep discount) an item to a customer in exchange for a review. “Review clubs” where formed where this would work systematically, with sellers viewing the profiles of reviewers to select where to send their items. As you can imagine, this led to “reviewers” happily giving 4-5 star reviews to anything that didn’t right-out collapse in their hands, in order to score free stuff. I had noticed that the previously very useful Amazon ratings were getting sort of funky and unreliable the last couple of years, and the worst cases happened in the more sophisticated products, where the average review club serial reviewer would anyway be unqualified to pass judgment. At one point I noticed that Amazon was full of “30×60” binoculars, which, magically (for a set that claims 60mm objective lenses in the title), could fit in the palm of your hand! In some listings they even claimed night-vision! With these charactersitics and their stellar reviews they are the second most popular binoculars on Amazon.co.uk (fortunately they are a little less popular on Amazon.com). So I ordered a set. Then, I signed up in a review club myself, and got a discount on one of the most popular 10×50 sets and also I borrowed from a friend another cheaper, popular 10×50 set and reviewed them all. The spoiler is: don’t buy no-name binoculars based on dubious reviews, and especially avoid anything “ruby lens”, “red membrane” etc. I’ve left reviews on Amazon and some are prominent enough to spare some people from garbage purchases, although others get rather inexplicably voted down and disappear from the first page (I’ve been contacted by people who get stuff from seller for free to tell me the sellers ask them to down-vote me). My “Hobby Store” review actually pissed off the seller and there were some exchanges (they apologized in the end)… Anyway, here’s what I gathered to put to the test: