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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Polar Scope Align for iPhone and iPad v3.1 released!

April 4, 2017 // by ecuador

WHAT’S NEW v3.1:

-Astro calculators: Over 15 calculators useful for observing and astrophotography, from eyepiece magnification and field of view, to imaging resolution and reducers. (Pro)
-Xasteria uses the 7Timer! service which will be, unfortunately, unavailable for technical reasons for quite a while. Thus, a link to an alternative weather report is provided, and my own server is accessed and a message about the status of the service is retrieved. (Pro)
-Added South Hemisphere versions for two Skywatcher reticles and improved reticle instructions.
-Sharpless 2 catalog added to the DSO DB, as well as 329 named stars and a few more named nebulae, taking the total to over 13000 objects for the Pro version, bright stars added to the non-Pro version.
-Added ability to sort by distance from an alt/az coordinate point in DSO DB.

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 Version

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Xasteria 1.9 released! World Astro Weather Report for iOS

March 27, 2017 // by ecuador

What’s New v1.9

-The 7Timer! service that Xasteria uses will be down for technical reasons. The 7Timer! people are sending their apologies, it is unfortunately an issue beyond their direct control. An alternative weather report link is added for the meantime, and Xasteria will connect to its own server on app launch and notify users about any changes to the situation.

More info on the Xasteria page.

Download on the App Store


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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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Cheap azimuth adjustment bolt upgrade for Skywatcher EQ3, HEQ5, NEQ6 etc, Orion, iOptron

January 28, 2017 // by ecuador

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:

Replacement bolts on SkyWatcher HEQ5

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Maximum field of view for Celestron SCT and Maksutov

January 27, 2017 // by ecuador

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
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

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.

Refractor Reducers: TeleVue TRF-2008 vs Altair Lightwave 0.8x on SW Evostar 80ED & Equinox 80 ED

January 11, 2017 // by ecuador

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).

The Reducers

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
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Review: Inexpensive Solomark 50mm Guide Scopes (same as Orion, Starguider, TS etc)

December 18, 2016 // by ecuador

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:

Solomark 50mm Mini Guide Scope

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 or There is also the StarGuider version on

Solomark F50 Guidescope

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 or 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 or, although I haven’t tried it myself.

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Barlow shootout: Skywatcher, Celestron, High Point, TeleVue Powermate and more

December 2, 2016 // by ecuador

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)

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Processing a (noisy) DSLR image stack with StarTools

November 20, 2016 // by ecuador

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:


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Amazon best seller binoculars, “30×60”, “ruby lens” and more…

October 14, 2016 // by ecuador

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 (fortunately they are a little less popular on  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 (e.g. if you have an account you could try upvoting this or the other 1-2 sensible reviews of that binocular). Interestingly my (rather generous I thought) 3-star review of that set 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:

L to R: SkyGenius 10x50, Mini "30*60", Hobby Store 10x50

Left to right: SkyGenius 10×50, Mini “30*60”, Hobby Store “Good Quality” 10×50

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Baader Astrosolar Photo film ND 3.8

September 23, 2016 // by ecuador

In a previous Solar filter test I explored how various filters help with getting some better white-light Solar surface feature photos, and I had noted that while I was using the Baader Astrosolar Safety ND=5.0 film, some narrowband filters would benefit from the photo grade Astrosolar ND=3.8 film, as with allowing as much as 1/6310 of the Sun’s light (vs the 1/100000 of the ND=5.0) gives you much smaller exposures that have less noise. It turns out that the photo film by itself gives you an improvement in results that no combination of filter can give you when using the ND=5.0 film, and allows you to use really long focal lengths. Because it speaks louder than words, just take a look at my first attempt at the Sun with the photo film and just my 80mm ED and Canon 600D in 3x zoom video (stacked with Autostakkert):

Skywatcher 80ED, TeleVue Powermate 5x, Baader Astrosolar ND 3.8, Canon 600D mod @ 3x zoom video

Great detail, right? It is at an effective 4000mm focal length using a 5x TeleVue Powermate and yet thanks to the high transmission of the filter I could do a 1/1250s exposure at ISO 400. Apart from stacking with Autostakkert I used Registax 6 for wavelet sharpening and made the color yellow in post-processing (normally the Baader filter gives you pink/purple with a modded DSLR). The filter is usually sold in 20x30mm and 50x100mm sheets (at £30-60 usually in the UK, similar in the rest of the world) but, strangely, there seems to be a shortage right now, so your best is to look at ebay – that’s where I got mine.

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

September 19, 2016 // by ecuador

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 $5000), 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 (and before / after correction values) from various reports (this source was helpful also this and numerous CN threads). 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 and sometimes I had to choose a source (e.g. Skywatcher and Orion give a bit different spec for the exact same mount). Prices are typical US & UK prices with basic tripod (or pier where applicable) included.

Manufacturer / Model Price Mount Head (kg) Payload (kg) Resolution (arcsec) Objects Polar Scope GPS PE/PEC (arcsec)
Celestron AVX $849/£739 7.7 14 N/A 40000 -1 30/8
Celestron CGEM $1499/£1289 19.4 18 N/A 40000 -1 16-30/6-10
Celestron CGEM DX $1695/£1499 19.4 23 N/A 40000 -1 ?/?
iOptron SmartEQ Pro $499/£449 2.8 5 0.5 59000 Yes2 No ?
iOptron ZEQ25 $799/- 4.7 12 0.14 150000 Yes2 Yes 12-32/5-6
iOptron CEM25 $799/£699 4.7 12 0.14 150000 Yes2 Yes ?/?
iOptron iEQ30 Pro $1398/£1285 6.8 14 0.14 358000 Yes2 Yes 16/5
iOptron iEQ45 Pro $1848/£1450 11.4 20 0.09 358000 Yes2 Yes 15/5
iOptron iEQ45-AZ $1948/£1450 11.4 20 0.09 358000 Yes2 Yes 15/5
iOptron CEM60 $2499/£2299 12.3 27 0.06 359000 Yes2 Yes 8-16/1.5
iOptron CEM60-EC $3999/£3599 12.3 27 0.06 359000 Yes2 Yes 4/0.5
Losmandy GM8 G $2495/£2240 9.5 14 N/A 40000 -3 13-20/8
Losmandy G11 G $3150/£2850 16.3 27 0.14 40000 -3 9-20/?
Skywatcher EQ3 Pro Synscan -/£399 4.2 5.5 ? 42000 -4 ?
Skywatcher EQ5 Pro Synscan (Orion SkyView) $790/£549 6.2 9.1 0.288 42000 -4 ?/?
Skywatcher AZ EQ5-GT (Orion Sirius Pro) $1300/£999 7.7 15 0.25 42000 -4 16-40/?
Skywatcher HEQ5 Pro (Orion Sirius) $1115/£779 10 15 0.144 42000 Yes2 20-50/6-7
Skywatcher AZ EQ6-GT (Orion Atlas Pro) $1899/£1419 15.4 18-25* 0.144 42900 Yes2 25-30/8
Skywatcher EQ6/NEQ6 Pro (Orion Atlas) $1395/£999 16 18-25* 0.144 42900 Yes2 20-50/6-7
Skywatcher EQ8 (Orion HDX110) $3505**/£3289 25.4 50 0.12 42900 -4 6-8/?
Vixen SX2 (+SB10****) $2199/£2449 7 12*** N/A 270000 -3 ?/?
Vixen SXD2 $2659/£2459 9.2 15*** N/A 270000 Yes2 27/?
Vixen SXP $3299/£3299 11 16** N/A 270000 Yes2 ?/?

*Orion rates these at 18kg, Sky-Watcher at 18kg imaging / 25kg visual (in the graphs below the average value is used).
**The price is with the Pier, as the mount is also sold head-only.
***Vixen rates their mounts for imaging, so they are probably more modest values compared to 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.

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 some mounts that are below it, all from iOptron, meaning they can lift more than twice their weight. The CGEM seems like a disappointing outlier, being the only mount to lift less than its own weight, but it is possible Celestron is being modest about their payload spec.
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Mid-high End ($3-15k) Telescope Mount Comparison Table

September 13, 2016 // by ecuador

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 and a Meade 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 before / after correction values) 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.

Manufacturer / Model Price Mount Head (kg) Payload (kg) Hand-controller Polar Scope PE (arcsec) PEC
10 Micron GM1000 HPS $9020/£6198 19.5 25 Yes No 1 Yes
10 Micron GM2000 HPS II $13703/£9514 30 50 Yes No 1 Yes
Astro-Physics Mach1GTO $5490/£5945 14.6 20 Yes Optional 4-7/1-2 Yes
Astro-Physics 1100GTO $7970/£9999 24.5 50 Yes Optional <7/1-2 Yes
Astro-Physics 1600GTO $10870/£12800 52 100 Yes Optional <5/1-2 Yes
Avalon M-Zero $4150/£3399 7.5 8 Yes Yes, illum 10-14/- No
Avalon Linear $5160/£3840 12.5 20 Yes Yes, illum 10-14/- No
Avalon M-Uno $6289/£4660 14.9 20 Yes Yes, illum 10-14/- No
Celestron CGE Pro $4999/£3889 34 41 Yes No 14-18/5 Yes
Fornax 52 $6200/£4299 35 50 Opt Optional 16/<1* TDM
Fornax 100 $9000/£5999 50 80 Opt Optional 16/<1* TDM
Fornax 150/100 $11750/£8220 70 100 Opt Optional 12/<1* TDM
Gemini G53F $7315/£5849 20 45 Yes Optional ? ?
Losmandy G11 $3195/£2850 16.3 27 Yes Optional 9-20/2-3 Yes
Losmandy HGM Titan $5995/£5799 34 45 Yes Opt, external 7/14/2002 Yes
Meade LX850 $6199/£7695 25 42 Yes No 8-16/3-7 Yes
Mesu-Mount 200 ?/£5199 25.7 65 Yes Opt, external 2-4/- No
Paramount MyT $6000/£5382 15 23 No No 4-7/<1 Yes
Paramount MX $9000/£8289 23 45 No Optional 4-7/<1 Yes
Takahashi EM-11 Temma-2 $3350/£3043 7 9 Yes Yes, illum 7-20/- No
Takahashi EM-200 Temma-2M $5210/£4198 15 18 Yes Yes, illum 10/- No
Takahashi EM-400 Temma-2M $9150/£7596 27.7 35 Yes Yes, illum 10/- No
Takahashi EM-500 Temma-2M $13020/£12324 45 45 Yes Yes, illum 7/- No
Vixen AXD (Atlux Deluxe) $7500/£7999 25 30 Yes Yes, illum ? Yes

As before, we start charting with the mount head weight vs payload capacity graph:

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Baader Astrosolar vs Thousand Oaks Black Polymer solar filter

September 11, 2016 // by ecuador

There are two popular kinds of inexpensive solar filters which you can buy in unmounted sheets, cut them and mount them yourself. The older kind is the black polymer type, with the most famous kind (especially in the US) being the one that Thousand Oaks makes (their glass filters are also popular), while the currently more popular (at least in Europe) type is Baader’s Astrosolar safety film. I have used the Baader film for a few years, but thought I’d give the Thousand Oaks a try in case it gives me something the Baader does not.

You can get the Thousand Oaks filter directly from the US manufacturer, or you can find a bit cheaper sheets on, or ebay (starting at around $15/£14 for a 6″x6″ sheet). The Baader film can also be found on,, FLO and ebay with prices starting at around £20/$37 for an A4 sheet. Be careful, we are talking here about the “visual” (ND=5.0) Baader film, as there is also the photo version (ND=3.8) which is only for high-power photo use (or visual with narrowband filters).

The Material


Baader on the left, Thousand Oaks on the right

Both materials are relatively easy to cut with scissors. Don’t worry if the baader film looks crumbled when you mount it, you are not supposed to tighten it, that’s how it should be. The black polymer seems like a tougher material, but as I’ve never had the Baader tear on me with some reasonable handling, I wouldn’t say it is too sensitive. It is always recommended to check your filters for holes before your session in any case – this particular Baader hasn’t developed any in the 3-4 years I’ve been using it.

First impressions

The biggest difference when you see through these two filters is the color of the Sun:

Baader Astrosolar Safety Film

Baader Astrosolar Safety Film ISO100 1/160s

Thousand Oaks Black Polymer

Thousand Oaks Black Polymer ISO800 1/80s

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