Archive for the ‘Reviews’ Category

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New scope: Bresser Spektar 15-45×60 spotting scope

December 9, 2015

Bresser Spektar 15-45x60 6 - side view

Thanks to this thread on CN, I recently learned about Optical Instruments, a sort of online clearing house for optical gear from Explore Scientific, Explore ONE, Bresser, and a few other instrument makers and resellers. In particular I was taken by the screaming deal on the 60mm Bresser spotting scope. I’ve had a lot of fun scoping birds with my telescopes (most recently with the C80ED), but I thought it would be nice to have a light, rugged all-in-one spotter for camping and hiking. And at $39.99 with free shipping, the price was certainly right – normally the scope lists for over $100. I placed my order on November 25, got a shipping notice on December 3, and the scope came in today (well, yesterday, December 8 – I’m up late).

Bresser Spektar 15-45x60 4 - on L-bar

I got the scope out for a few minutes late this afternoon for a test drive. It’s solid. The eye lens is nice and big and the objective has purplish anti-reflection coatings. Optically okay – the image does go soft in the outer 10-15% of the field, and there’s a bit of chromatic aberration, but neither problem is severe enough to put me off. The eyepiece is not quite parfocal across the zoom range, but it’s close enough that I just need to touch up the focus a bit after changing magnification. Fit and finish are merely serviceable, about on par with inexpensive Celestron binoculars. It certainly doesn’t have the feeling of machined perfection that you get from a nice telescope, but part of that may be the rubber armor (which I’m more happy about than not, as I intend to use this scope).

Here are a couple of unboxing photos with the scope still in its case.

Bresser Spektar 15-45x60 1 - in box

Bresser Spektar 15-45x60 2 - in case

Five features I really like:

  1. Padded view-through case – this has cutouts for the mounting foot and focus knob, and the covers for the objective lens and eyepiece snap off, so in bad weather you can leave the case on while viewing.
  2. Sliding dewshield for the objective lens – I’ve only had my scope out on a cloudy day just before sunset, but I’m sure this will come in handy for cutting down glare on sunny days. This is extended in the first picture at the top of the post, collapsed in the second one.
  3. Twist-up eyecup on the eyepiece – nice for visual, great for digiscoping as it helps get the distance from the camera to the eye lens just right.
  4. Mounting foot on a rotating collar – super useful for side-mounting. The focus knob is on the right side of the scope, so it’s better to put the mount on the left if possible. I used a Universal Astronomics DwarfStar mount for testing, first with the scope upright on an L-adapter (second photo above), and then later on side-mounted using a spare footplate from a Manfrotto ball-head as a makeshift dovetail bar (see next photo below). One thing to be aware of – the cutouts in the case for the focus knob and mounting foot are fixed, so you can’t have the view-through case on if you side mount the scope.
  5. Side-mounted focus knob – most spotting scopes have a little knob in front of the eyepiece that you roll side-to-side to focus. I’ve never gotten the hang of that; I’m always struggling to find the right amount of pressure to turn the focus knob precisely without pushing the scope off-target or shaking the view. The side-mounted focus knob on the Spektar makes it feel just like using any other refractor, in that I’m reaching my right hand forward and rolling a focus knob. Lefties may not be so wild about this.

Here’s a photo showing the scope side-mounted, with the mounting foot facing left from the eyepiece and the Manfrotto footplate ‘dovetail’ (lighter grey metal) serving as a dovetail bar. The lock knob for the rotating collar with the mounting foot is facing straight up here, and the larger, right-mounted focus knob is also visible.

Bresser Spektar 15-45x60 5 - side mounted

Now, five things I don’t like:

  1. No pictures in the so-called instruction manual. Until now, I’ve always gotten a chuckle out of the labelled photo of the assembled scope in most telescope instruction manuals – sheesh, who doesn’t know what the eyepiece is? But now the shoe’s on the other foot, and I’m not laughing anymore. This scope has some non-standard features and you’re basically left to figure them out by trial and error. I did that, mostly successfully (but see below), but it’s still an irritating oversight.
  2. Just below the eyepiece is a knurled ring that rotates. I don’t know what it’s for – maybe it’s a lock ring to hold the zoom eyepiece in place? I haven’t had the courage to unscrew it and find out.
  3. The rotating collar and lock knob feel very plastic-y, and the lock knob does not come to an authoritative stop. Instead it sort of oozes into tightness. I’m worried I’m going to overtighten it and either strip the threads or break the knob.
  4. As people on CN have noted, the soft rubber dust cap for the objective lens is a loose, floppy joke. At one point while I was unboxing the scope I happened to point the objective end downward and the dust cap just fell off. And most frustratingly, while I was packing the scope up at the end of the day my hand hit the dust cap and it bent in and left a smudge on the objective lens. Grrrrr. I have a cheap Meade spotting scope from back when and it has spring-loaded dust cap that locks in place, like the dust caps on most DSLR cameras and lenses. If the dust cap on the Spektar was at least hard plastic, I could shim it with felt (I’ve done this with countless telescope dust caps). Feels like they really cheaped out here.
  5. The padded view-through case is nice but it leaves the focus knob exposed. In my book that’s okay for day use but not for something you’re going to store the scope in. If there’s one place you don’t want moisture or dust getting inside the case, it’s at the focus mechanism. Something like a velcro flap over the focus knob would be easy enough to install, but it feels like something that should have been addressed at the design end. Maybe it’s mean to pick on this one thing – I buy scopes all the time that come in padded boxes with no case, so the padded case here is definitely a step up. The Telescope Warehouse on eBay sells locking and waterproof cases that fit spotting scopes – I’ll probably be picking one up shortly.

Verdict? The scope has some quirks and some outright deficits. Fortunately they are with the mechanics and accessories rather than the optics. It also has some very nice features that make it easier and more convenient to use, compared with most spotters I’ve used in the past. At the list price of $130 it’s probably possible to do at least as well or better with something from Alpen, Barska, Bushnell, or Celestron. But for $40 it’s a steal.

The rest of the photos are quick digiscoping pix from this afternoon’s test run. It was overcast, I didn’t get outside until just before sunset, and I didn’t put on the camera adapter but instead shot everything handheld. So some of the problems with the photos are not the fault of the scope – the low light levels meant low contrast, uneven field illumination was mostly my inability to get the iPhone’s camera lens centered in the spotting scope’s exit pupil, most of the CA and almost all of the spherical aberration are from the iPhone, and I couldn’t hold the camera as still as the adapter so the detail in the photos does not nearly match the view through the eyepiece. I need to get out and play with the scope under better conditions, but for now, this is what I have. Other than the unmagnified reference image, none of these are processed at all, partly for versimilitude and partly because I’m lazy.

With all of those caveats in mind, here we go. Captions are below photos.

Telephone pole at 1x

Here’s an unmagnified iPhone pic of the utility pole and the mountain shown in the close-ups below. The utility pole is about 300 feet away, the mountaintop is 10.5 miles according to Google Earth.

Telephone pole at 15x

Utility pole at 15x. Darkening around the outside is me not getting the camera in the right spot – it was not visible visually. See the woodpecker?

Telephone pole at 45x

Utility pole at 45x. Woodpecker had moved on by this point. I could see a lot more detail visually, including growth rings in the wood and the twisted wires that make up the power lines.

Mountains at 45x

Those trees on the ridgeline admittedly do not look brilliant. But considering that they’re 10.5 miles away and being imaged handheld through a couple of intermediate layers of branches, I’m pretty impressed. We’re in the glidepath for airliners going to LAX and Ontario, and for small private planes out of Cable Airport, and I had fun this afternoon chasing airplanes with this scope. The next clear night, I’ll probably be out chasing satellites instead.

As of right now (early in the morning of December 9, 2015) the spotting scope is still available at $39.99 with free ground shipping. Optical Instruments has a bunch of other stuff on sale right now, including some binoculars and small telescopes. If you’re interested enough to get this far, you owe it to yourself to give ’em a look.

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Gear reports: Explore Scientific eyepieces, Orion Apex 127 Mak, Celestron Travel Scope 70

July 16, 2012

Apex 127 (left) and Travel Scope 70 (right) under dark skies on Mount Baldy. The Apex is on a SkyWatcher AZ4 mount, and the TS70 is on a Manfrotto CXPRO4 with a Universal Astronomics DwarfStar alt-az head. Photo by Terry Nakazono.

As promised in the last post, here are my thoughts on the scopes and charts I used up on Mount Baldy Saturday night. I haven’t had half of this stuff long enough for these to be considered true reviews, so I’m calling them “gear reports”.

Explore Scientific eyepieces–For  a long time my workhorse eyepieces have been 32mm and 12mm Plossls and the 6mm Expanse. The 24mm ES68 gives the same true field as the 32mm Plossl but with higher magnification and a larger apparent field–68 degrees versus 52. The 14mm and 8.8mm ES82s give me a nice pair of mid-to-high power options, without taking business away from the 6mm Expanse.

How important is all that apparent field of view? I’ve also had the opportunity recently to look through a few TeleVue Ethos 100-degree eyepieces, and here are my impressions.

  • Ethos: I could not quite see all of the field of view at once. I had to actually move my head around to see the field stop. It was nice–when I first looked in the eyepiece, at what was in the middle of the field, I could not immediately see the field stop in any direction. It actually was like looking through a window into space. I can see why people shell out big bucks for this experience (think $600 and up for the TeleVue Ethos models and $400 and up for the other brands).
  • ES82: I can see all of the field and the field stop at once, but it is so far out to the edge of my field of view that I am not really aware of it. Very comfortable, too, in terms of eye placement and eye relief.
  • ES68 and Orion Expanse (66-degree apparent field): ditto. For me, the jump from 52 degrees to 66 or 68 degrees is much more noticeable than the jump from the sixties up to 82–or back. I never went from one of the 82s to one of the sixties and thought, “oh, hey, where did my extra field go?”, which definitely does happen when I go directly from a widefield to a Plossl. My only explanation is that, at least for me, 66-68 degrees is over a threshold where additional apparent field makes little difference, until the I-can’t-see-it-all-at-once threshold I get with the Ethos.
  • Plossls (52-degree apparent field): I like Plossls. They’re good, solid workhorse eyepieces, that can handle a wide range of focal ratios and tend to be sharp and have good light throughput. They were my go-to eyepieces for years. But, like many, many stargazers before me, I am spoiled now. The fact is, after using 66-82 degree eyepieces (I’ve had a pair of 68-degree Orion Stratuses for a couple of years, and just not used them much), going back to the Plossls is like being struck with tunnel vision: I am acutely aware that a lot of my visual real estate is occupied by non-sky inside-of-eyepiece black nothingness. That said, the effect really only jumps out at me when I swap a widefield for a Plossl back to back in the same scope. Saturday night I would be observing with widefields in the Apex and then wander over to the TS70 with the 32mm Plossl and not notice the sudden decrease in field. So I’m not getting rid of my Plossls anytime soon. For one thing, they all weigh much less than their widefield counterparts, and so play better in small scopes and travel kits.

By the way, if you’re in the market for budget Plossls and Expanse clones, check out the Black Knight Super Plossls and Enhanced Super-Wides at OWL Astronomy.

Apex 127–Under dark skies, a potent deep-sky instrument. Its maximum true field of just a bit over a degree will frame almost all deep sky objects, except for the very closest open clusters (like the Pleiades and Hyades). Everything I tried for, I found–my problems with the two open clusters were not that I could not see them, but that I could tell exactly what parts of the rich Milky Way starfields were supposed to be the clusters–more on this farther down. It’s also a planet-killer and excellent double-star scope. One night this spring I was trying to split a particularly tough double with this scope. It refused to budge at 257x, so I Barlowed my 6mm expanse to give 514x, and finally saw that stripe of black sky between the two stars. That’s about 100x per inch of aperture, or twice the rule-of-thumb “maximum effective magnification” of 50x per inch. Which means it’s a damn fine scope.

Travel Scope 70–Four things about this scope, three good, and one not so good. The good stuff first.

  • It costs next to nothing. As I’ve pointed out in other posts, you can’t buy a 9×50 right-angle correct-image finder for what they’re charging for this scope.
  • It’s small and light. I think it would ride on the same tripod as my SV50 and the scope itself takes up hardly any more room, but 70mm gathers roughly twice as much light as 50mm (5*5=25, 7*7=49). It has the same focal length as the venerable Short Tube 80 but weighs about half as much. You could think of it as a Short Tube 70, but its focal ratio of 5.7 is a hair more forgiving. That combined with the slightly smaller aperture should knock down the chromatic aberration a bit, compared to the ST80, and indeed I’ve found the CA unnoticeable in casual use, even on the moon and  planets (that is, I’m sure it’s there if one goes hunting, but it’s never risen to the level of attracting my attention at the eyepiece).
  • The optics are wonderfully clear. The low-power views are really bright and contrasty. I noticed this the first night I had the scope. I was cruising the summer Milky Way from my driveway, trying the 12.5x view with the 32mm Plossl for the first time. Now, Lyra was dead overhead, and atmospheric problems are almost always minimized at the zenith, but still, the view was bright, and I found the Ring Nebula, M57, right away. I thought “No way, there’s just no way the Ring is that easy at 12.5x. Must be an out-of-focus star.” So I started working my way up in magnification, and sure enough, it was the Ring after all. I noticed the same thing again Saturday night. I couldn’t see much detail on most of the Messier objects at that magnification, but they just jumped out of the background starfields, even the smaller ones. If you like low-power scanning, this scope is a blast under dark skies and still a fun ride even under so-so skies.

Now, the not-so-hot:

  • It’s hard to push the magnification, and I don’t like the result when I do. A 12mm eyepiece gives 128x in the Apex 127, 108x in the 90mm Mak, and 100x in the XT10, but only 33x in this  scope. A 6mm eyepiece gets you to 67x, but it ain’t worf it. The scope starts to pant around 40x and anything north of 60x is just bad. I noticed this the first night out, looking at Saturn and the moon, and it was still true this weekend. I don’t know if its astigmatism or poor collimation or what, but trying to achieve focus on planets is maddening. Jupiter goes from a vertical fan of red light on one side of focus to a horizontal fan of blue light on the other, and only sort of flirts with being a clean disk in between those extremes, at an infinitesimally tiny point that the rack-and-pinion focuser tends to shoot right past. It’s actually really puzzling to me that a scope that gives such clear, contrasty images at low power goes to crap so fast as the magnification goes up. (In case you’re wondering, we used exclusively low-power eyepieces with this scope for the Venus transit.)

So in the end the TS70 is kind of a one-trick pony. It is awesome for scanning around at low power and surfing the Milky Way. That’s the one thing it can do that neither of my Maks can. But unless you get a much better sample than I did, forget about doing any serious work at even moderate magnifications. The 90mm Mak is a much more versatile tool–it can do almost everything except widefield scanning. So at least the two small scopes complement each other.

UPDATE: the TS70 performs MUCH better after having been disassembled and reassembled (details in this post). It’s not hard, all it takes is a screwdriver. Blackening the lens edges with a Sharpie improves the scope’s already decent contrast, and shaking the lens cell a little while the objective lenses are loose will improve the collimation. After doing only that, I can now take this scope up to at least 133x without the image falling apart. It’s like a whole new scope. That said, there are still better choices out there – see my astronomy wish-list for beginning stargazers for some suggestions.

Actually the awesome low-power views of the TS70 have inspired me. A small ED refractor like the Astro-Tech AT72ED ought to give equally good low-power views and be able to take magnification well, and could potentially put both the TS70 and the 90mm Mak out of business. I don’t know if it actually will, but I aim to find out. So I think one of those will be my next big astro purchase–once I save up for it.

In the meantime, since the TS70 performs like a superfinder anyway, I’m going to keep scheming on how to turn it into one. I’d love to have it mounted side-by-side with the Apex 127, so I’d have a rich-field scope and a planet-killer on the same mount.

Pocket Sky Atlas–Since I started out in astronomy, the PSA has been essentially the only atlas I’ve used. It has stars down to magnitude 7.6 and about 1600 deep-sky objects. That includes all the Messiers, all the Caldwells, and all the Herschel 400s, plus another thousand or so, so it’s covered my needs and then some. The only time I’ve printed up my own finder charts has been for hunting quasars. I haven’t felt the need to move up to a “deeper” atlas until very recently.

I started thinking about a deeper atlas after observing with Terry Nakazono last month. His most-used atlas is the Observer’s Sky Atlas, which covers the whole sky to mag 6 but also has enlarged charts to mag 9 for finding 250 deep sky objects, including all the Messiers. He also prints out detailed finder charts from the Tri-Atlas (a huge free atlas in three versions: mag 9, 11, and 13). He was surprised that I’ve gotten along as well as I have with just the PSA.

Part of the difference in preference probably has to do with the instruments that we use and how we get on target. Terry’s most-used scope is the SkyScanner 100, which has a red-dot finder. So he gets in the neighborhood–or closer, sometimes you can really bullseye things with an RDF–with the dot finder and then star-hops to his targets at the eyepiece. In contrast, I use a 9×50 RACI finder on whatever scope I am observing with (I only have one, and just move it around among scopes), and do almost all of my star-hopping with the finder alone. The 50mm finder does not go nearly as deep as the 100mm reflector–it simply shows fewer stars–so I often use the geometrical method of centering the finder on an unseen target (this is detailed by Harvard Pennington in The Year-Round Messier Marathon Field Guide and by Stephen Saber in his post on “sharpshooting” deep-sky objects–search for it here). I hadn’t given this much thought before Terry brought it up, but my less-deep atlas suits my finder-driven navigation, whereas eyepiece starhopping really requires that you be able to see as many charted stars as possible to keep from getting lost. So we have each gravitated toward the atlas that best suits our observing style–or rather, I started with PSA and never had a reason to gravitate away.

Until now, that is. The problem is not that the PSA doesn’t show enough deep-sky objects. I’ve only seen about a fifth of its 1600 plotted DSOs. The problem, as Terry pointed out, is that it just doesn’t show enough stars, at least for some problems. In trying to track down some of those small open clusters in Cygnus and Cassiopeia, I found that the plotted symbol in the PSA covered a good-sized field that was striped and mottled with star chains and asterisms of the summer Milky Way. The geometrical relationships shown in the PSA just weren’t enough. I couldn’t go to “the” cluster of stars that made an equilateral triangle (or whatever) with the nearest guide stars, because there half a dozen plausible candidates (actually, this might be a not-enough-DSOs plotted problem as well as a not-enough-stars problem). I need to see some of the fainter stars in between plotted on the chart, to break up those rich starfields into manageable–and interpretable–chunks.

So, to make a long story short, I ordered the first volume of Uranometria 2000.0, a mag 9 atlas, and I’ll get the other two volumes as funds allow. Stay tuned.

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Guest post: A few thoughts about the Orion SkyScanner and other scopes, including the Bushnell Ares 5

July 8, 2012

Here’s the first guest post by frequent commenter and dedicated deep-sky observer Terry Nakazono. Actually “dedicated” is an appalling understatement, since Terry regularly challenges himself and his scopes by (1) observing faint deep-sky objects, mostly galaxies, (2) with small scopes he can carry on public transportation and by foot, (3) from light-polluted skies in and around Los Angeles. I’ve been looking forward to reading about Terry’s scopes and his observing techniques, so this guest post is most welcome–hopefully there will be more to follow.

I’ve been using the Orion SkyScanner the past 2 years for nearly all of my deep-sky observing needs because it’s so easy to transport and set up – crucial if you rely on public transport and your own two feet to get to darker sky sites. For a package weighing in at 6.2 lbs with scope and mount combined, 100mm of mirror is a lot of aperture.

Both scope and mount fits snugly in this Adidas Schmidt backpack. All that’s needed is a tripod to attach the mount to, and a solid Manfrotto weighing in at only 4.5 lbs. (but with a 15.5 lb. weight load capacity) provides a strong, stable support.

Factor in the eyepieces, star charts and other accessories, and you’re only transporting about 12-13 lbs. of equipment on your body. By comparison, the Orion StarBlast 4.5 weighs 13 lbs, while the Orion SkyQuest XT4.5 is 17.6 lbs. Both cost about twice as much ($199.99 and $239.99, respectively) as the SkyScanner ($109.99) and both add only 14mm of additional aperture to the mirror. As Joe Roberts says, you will not likely find a scope that will show more for the cost.

For deep-sky work, superb optics isn’t as critical compared to planetary and double star work, so a 100mm Newtonian reflector works well (for me). Despite not having a collimatable primary mirror, collimation can be achieved by center spotting the primary mirror and adjusting the tilt on the secondary with the help of a collimation cap, significantly improving the views of the planets and double stars as well as deep-sky objects.

Here, you can just see the notebook reinforcement ring I put on the center of the primary mirror; the secondary mirror is collimated by adjusting the three allen screws surrounding the main screw in the center of the secondary holder with an allen-head screwdriver.

Having said all that, I’m no longer wedded to the SkyScanner as my sole dark-sky instrument.

I now have an Orion shoulder bag that I can carry my Orion VersaGo II mount and Bushnell Ares 5 in.

I also have a Vixen Mini-Porta mount which will support my Celestron C90 Maksutov-Cassegrain (C90Mak, top) and Orion ShortTube 80-A (ST80A, bottom) telescopes. I just ordered a smaller Orion shoulder bag that will carry the aforementioned mount and one of these two scopes. These Orion bags are ergonomically well-designed and make it easy to carry both scope and mount over your shoulder without causing major strain.

I suspect that despite their better optics, both the C90Mak and the ST80A will not allow me to see “deeper” into space (i.e. detect fainter objects) than the SkyScanner. But I’ll need to perform a “shoot-out” between these scopes outside of light-polluted urban skies to confirm.

Right now, I see the collapsible tube Bushnell Ares 5 (BA5) as the scope that will eventually replace the SkyScanner as my deep-sky instrument once I’ve gone as far as I can with the latter. This is an F/5 130mm Newtonian which thanks to its unusual design, weighs only about 6.5 lbs. for the OTA. At only $164.99 (with no shipping or sales tax) from Optics Planet, this is probably the best scope deal in the country right now.

Here is the scope with the tube collapsed, mounted on an Orion VersaGo II (because of its bulkiness, I’ve discarded the 6.5 lb. tabletop mount that came with this scope).

And here is the scope with the tube extended all the way out.

I’ve created a light shroud made out of black felt to cover the open tube and protect it from the elements while observing.

In the limited amount of time I’ve used this scope in both light-polluted and semi-dark skies, I’ve had a tantalizing taste of what 130 mm. of light gathering power can show. In my light-polluted front driveway with direct vision, I was able to see the ring shape of M57 for the very first time, using only 65X magnification. With the 100mm SkyScanner, I can barely make out shading within the interior of the oval-shaped disk at 80X or more using averted vision in darker skies. Less than two months ago, I took my BA5 out to a semi-dark (orange-zone) site for the first time. M13 looked nothing like the views I saw through the SkyScanner – at 130X, this globular was just exploding with stars all over the place. Ditto for M5.

As Matt has shown us through his reports on using “Stubby Fats” in the desert, you can do some serious deep-sky observing with a 130 mm F/5 Newtonian in semi-dark or dark skies.

But the BA5 has to wait until I’ve exhausted all the possibilities of the 100mm F/4 SkyScanner.

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Guest post: Four-way diagonal comparison!

June 2, 2012

I’m happy to host another guest post (here’s his last one) by frequent commenter and indefatigable scope hacker David DeLano. In this one David compares four 90-degree diagonals: a high-end prism and mirror, and a low-end prism and mirror.

The Test Scope and Target

Here are pictures of the setup I used to test the diagonals.  But first, here’s the dovetail on spare ring that I made for my RDF.

Here is a picture of the target I shot.  It’s the AC unit in the middle of the picture.  This picture is taken at the same zoom level as I used for the pictures taken through the scope.

Here is the scope setup.

The Contenders

Here are the StellarVue prism diagonal on the left and the Astro-Tech mirror diagonal on the right.

Here are the generic diagonals, prism on the left (with SV helical focuser) and mirror on the right.

Here is a shot of the SV diag to show that it’s stopped down.  The generic has similar baffling.

The Camera Mount

Here are the parts to the camera setup, the part that fits onto the camera mount hole to give a T-thread, the barrel that holds the EP and provides a T-thread, and both together.

    

The Comparison

I used my 80AR on my AZ mount for this test.  I had to extend the legs all the way to get a decent target in sight, and then had to pull out my step stool to be able to see into the camera.  I used the bracket I have that puts a T-thread on my Sony P71.  I put a SkyWatcher 10mm Super Plossl into the barrel I have, and attached it to the T-thread.  I’m just not steady enough to shoot freehand like Matt does.  I picked an AC unit about a block away, and was shooting at 91x.  I could see heat waves, so took a couple pictures with each diagonal.  I had the camera set to macro, so the telescope was doing all the focusing.  I still found it very difficult to get a decent focus on my LCD screen, and it shows in the pictures.  I shot the pictures to get email versions, but have the full versions for closer examination.  I tried to use the same zoom for each picture, though one set is one setting wider.  I used the timer on my camera so that I wasn’t touching anything when the picture was taken.

The prisms are on top, the mirrors on the bottom, the generic versions on the right, and a diagonal-less shot at the end.  It was a lot more difficult to get the straight shot, believe it or not, and I didn’t realize that it had drooped on me as much as it did.  The collage is from the full sized pictures, reduced by 50%. I can zoom in and inspect specific data on the originals, but it really only tells me that there was a light breeze blowing.  I took at least two pictures from each setup and took the best picture.

I still have the same conclusions.  The generic prism is the worst, but probably not as bad as the one Matt has.  Definitely good enough for a finder or lower power viewing.  The A-T is slightly brighter, but note that it’s a little less bright than straight through.  The generic mirror holds its own, and I don’t think anyone would be disappointed using it.  That is the main message here for the posters that didn’t want to buy the A-T but wondered if a generic mirror was good enough – it is.

I think this convinces me that I’m not losing much with my SV prism, but it also shows me that I should give the A-T a decent shot in the 80AR.  Zooming in on the pictures, I can almost read some of the tags in the A-T shot (though the text is backwards), but I can also see purple edges with the A-T that aren’t there with the SV.  People disagree with Vic [Maris, of StellarVue] that their prism takes out some CA, but these pictures would say that he’s right (and I’ve not heard an explanation as to why it reduces CA).

An interesting note…..there is a seam on the electrical box going down the middle of the edge.  On all these shots, I used that to focus on, to be as consistent as possible.  It was definitely there in the camera LCD.  You can’t see it very much at all in any of the pictures.

Conclusions

Well, this isn’t quite what I expected.  I’m guessing my ability to focus is a variable that needs to be removed.  But, I’d be happy with any of these, with the generic prism coming in last.  If your prism is of worse quality, I can see you not wanting to use it.  But the SV appears to hold its own, and knocks down some of the CA (which it is rumored to do – I won’t say advertised).  The A-T is definitely a brighter view, and I look forward to getting it out under the stars to see how it does.  For those worried about a generic mirror, it holds its own.  My guess is that I spent $15-20 for this one and it’s the one I started with several years ago.

BTW, I have a third prism that I didn’t test.  I have an Orion brand in the GS.  It too is stopped down more than a mirror.  I’m guessing that stopping down an underperforming prism would help with the reflections.

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SkyWatcher Mak 90–more pictures, and using the mount in manual mode

March 4, 2012

More pictures of the SkyWatcher 90mm Backpacker Mak-Cass. Yesterday I took the multi-mount off its tabletop base and put it on my Manfrotto tripod for some digiscoping. I was using it without the power on, as a manually-aimed alt-az mount.

Another of those down-the-tube shots showing the optics. The point of this photo is different, though. Check out the knurled knob on the left that tightens the dovetail. Usually these just have a fat set-screw that goes straight onto the scope’s dovetail bar, and tightening that screw puts a tiny dent or ‘bite’ into the dovetail bar. On this mount, though, the set-screw bypasses the scope’s dovetail bar, and turning the hand knob tightens a broad metal clamp (the silver bit just underneath the hand knob in the above photo) that grips the dovetail bar along its entire length. So the scope is held more securely, and there’s no bite mark on the dovetail bar. Very nifty–I wish more mounts had this.

The big news about using the mount manually is simply that it can be used that way. You don’t want to manually aim the scope once the power is on, or you risk damaging the gears inside the mount, but as long as the power is off you can just grab the tube and point.

A close-up of the back end showing, from left to right, the Astro-Tech dielectric diagonal and 32mm Plossl I was using for birding, the six-screw  mount for the little 8×20 optical finder, and the dovetail clamp and adjacent latitude/altitude scale on the mount.

Getting lined up on a distant bird using the optical finderscope. Imagine that the mount was sitting on its tabletop base and that you were trying to find something high in the sky–eventually there is just no room to get your head behind the eyepiece of the finder. That’s why I strongly prefer RACI–right angle, correct image–finders, which orient the finder eyepiece in the same direction as the telescope eyepiece, so you can look down and in from above.

Waiting for the fall of night.

My two best shots of Jupiter with the little Mak. I could see about half a dozen distinct cloud bands at the eyepiece, and for once the photos bear that out. As usual, however, I could still see more detail at the eyepiece than the camera captured. The views are not as good as through the Apex 127–compare to the Jupiter photo here–but they’re not that far behind.

The waxing gibbous moon, again with the little Mak. This is probably the sharpest moon photo I’ve ever gotten with a 90mm Mak. This SkyWatcher scope is at least as good, optically, as the Orion Apex 90 I used to have. I don’t know yet if it’s as good as the Celestron C90, which has gotten stupid-good reviews, but I don’t think it will disappoint anyone. Last night the sky was still enough that I could run it up to 200x and the view was still razor-sharp. That’s 57x per inch of aperture, compared to the rough rule of thumb of 50x/inch in a good scope, so this little scope is punching above its weight. I haven’t tried to max out the magnification to see where it breaks down, but I think it will probably be quite a bit higher.

The fact that the meniscus is merely coated instead of multi-coated has not impaired the scope’s performance as far as I can tell. Possibly the few percent difference in light transmission will be noticeable when one can switch back and forth between this scope and one with a multi-coated meniscus; it is certainly not noticeable when using the scope on its own.

I still haven’t had time to try out the tracking function on the mount, but this afternoon I did put batteries in and slewed it around and didn’t have any problems. I’ll report back when I’ve had it out tracking under the stars.

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The SkyWatcher 90 Backpacker on the moon and some birds

March 2, 2012

Fate smiled on me yesterday and early this morning, and I was able to get some pictures with the SkyWatcher 90 mm Backpacker. If you’re impatient you can scroll to the bottom of the post for the photos.

I should stop here and say that I ultimately intend to test the whole kit–scope, mount, and accessories–as a system, because whether you use it as-is or mix-and-match components, it is sold as a system and is at least theoretically supposed to function as one. However, between teaching, taking a statistics class, and wrangling ostriches, I just haven’t had time to mess with the mount. My primary concern has been to assess the optical quality of the scope–and now I actually have some information.

I got in a brief observing session between responsibilities yesterday afternoon. I was plinking around the yard, looking at birds. For these observations I started out using the included 90-degree prism diagonal and 25mm Plossl eyepiece. I first looked at a couple of obvious birds silhouetted against the sky in treetops, and they looked fine. Then I went after one hidden in the leaves and branches of one of my neighbor’s trees, and in those dimmer conditions I noticed something unnerving: the eyepiece view was very soft and didn’t snap to focus, as if I was observing with a very short focal ratio scope like an Astroscan. Also, there was some ghosting of the image in the eyepiece, and the edge of the image was poorly defined. In short, it was very, very different from the crisp, sharp, detailed images that Maks are renowned for, and not in a good way. I was just having a “Hey, what the–!” moment when I remembered where I had seen these kinds of problems before: in scopes using cheap prism diagonals instead of mirrors.

Without moving the scope, I went to the garage and pulled the Astro-Tech dielectric diagonal off my Apex 127, and swapped that out for the prism diagonal. I held my breath as I put my eye back to the eyepiece–were the problems all in the diagonal, or had I gotten a lemon of a scope?

Sweet relief–even in the dim light amongst the leaves and branches, the view was razor-sharp and contrasty. It was like someone had run a very good image-sharpening algorithm on the eyepiece view. Suddenly details that were invisible before were popping out all over the place. Leaves that had been too fuzzy to invite close inspection were etched with delicate networks of veins. The whole view just looked more real.

I decided then that I would try to find out just how good or bad the prism diagonal is, and under what conditions.

After that quick peek I didn’t get another chance to use the scope until about 10:00 last night. The first quarter moon was still fairly high in the west, but the seeing was not good. The air just roiled over the moon, and every star I looked at scintillated with fast-moving rays of light. Not good conditions for testing a new telescope, because it’s hard to push the magnification up and tell if the results you’re getting are because of the scope, the seeing, or both. But I went ahead and put the scope through it’s paces anyway. The thing about seeing is that from time to time it does settle down a bit, at least momentarily, and in those instants the amount of additional detail that is visible is sometimes shocking. So the longer you look and the more patiently you observe, the more likely you are to catch those rare moments of steadier air and see something really remarkable.

For eyepieces I used a 32mm Sirius Plossl from Orion and the 12.5mm and 6.3mm SkyWatcher Plossls that came with the scope. I took all of the pictures in this post afocally with a Nikon Coolpix 4500 hand-held to the 32mm Plossl, and with the camera optically zoomed enough to eliminate any vignetting.

The moon looked surprisingly good with the Astro-Tech diagonal in place. It was fairly swimming in the turbulent air, as if being viewed under a thin stream of moving water. But if I focused on a particular crater or feature for the space of a minute or two I would catch a patch of calmer air and see perhaps double the detail in those brief glimpses. Small craters that were otherwise just spots would pop into focus with dark rims and bright floors. The 12.5mm eyepiece had tighter eye relief than I am used to in that focal length; I have long-ish eyelashes and they were occasionally brushing the eye lens, something I don’t remember ever happening with the 12mm SkyWatcher Plossl that I got with Shorty Long, my 80mm f/11 achromat. That 12mm looks identical to the Orion Sirius line, whereas the eyepieces that came with the Backpacker have smooth silver barrels and no rubber eyecups, so even though they are both branded SkyWatcher they might have somewhat different guts. Also, I’ll have to look more closely the next time I’m out, but the 12mm felt like it had a narrower apparent field of view than the 32mm, which shouldn’t be possible if they are both Plossls, which typically yield a 52-degree apparent field. Could be that the short eye relief was playing tricks on my perceptions. Anyway, with the 12.5mm EP in the scope was working at 100x and I was still seeing plenty of few detail in the still moments.

I put the 6.3mm EP in just for the heck of it. I wasn’t expecting much, both because of the punk seeing and because that magnification–200x–ought to be pushing on the edge of what this scope can do. A commonly used rule of thumb is that a good scope should be able to handle 50x per inch of aperture. At 3.5 inches, any of these 90mm Maks ought to be good up to at least 175x. But I have to point out that the 50x/inch “rule” is often broken and not only by premium scopes. David DeLano has had his 114mm reflector up to 400x (89x per inch), and the other night I took my Apex 127 to 514x (103x) to split a close double star that was not split at 257x. I’ll just note that those are both relatively long focal ratio scopes, about f/8 for David’s reflector and f/12 for the Apex, and maybe that has something to do with it; such gently-tapering light cones are certainly easier on eyepieces and so on. Anyway, at 200x with the 6.3mm EP I was still getting glimpses of considerable detail. I can’t say for certain because of the lousy seeing, but I think this scope can handle 200x. I hope I get a still night soon to test that.

Okay, so far so good with the Astro-Tech diagonal. I swapped it out for the stock prism diagonal and went back to the 32mm Plossl. YUCK! I almost could not focus my eye on the moon, because there was a moon-sized ghost image floating around in the field of view that looked like it was probably some kind of reflection of the primary mirror or maybe even the corrector. It was a big white donut with a dark hole in the middle, anyway. I’ll stress that this ghost image or whatever it was was not there with the Astro-Tech diagonal. I have never seen anything quite like it before, and given the controlled conditions of time, place, observer, scope, and eyepiece, I feel confident blaming the prism diagonal.

I tried the two other eyepieces. The ghost didn’t show up in either of them. The 12.5mm was merely okay, producing a slightly softer view in the prism diagonal than in the Astro-Tech. The 6.3mm was very noticeably softer; this time going from 100x to 200x looked and felt like empty magnification.

I also looked at Belelgeuse and Mars with all combinations of diagonals and eyepieces. Betelgeuse was sparkling in the Astro-Tech diagonal, but at least the scintillating rays of light were sharp. In the prism diagonal it was a fuzzy mess. Betelgeuse was down near the horizon, though, and Mars was very high, so I hoped to see at least some detail on good old Barsoom.

Mars really required the 12.5mm EP; at 39x it was a bright orange BB, too small to see detail on, and at 200x it was a big orange smudge. At 100x with the prism diagonal I could only suspect the polar cap, and that might have been because I knew it was there to be seen. I had started that run with the Astro-Tech, and in steadier moments the polar cap was a well-defined white patch with a hair-fine black border. In brief flashes I also saw dark markings on the face of the planet’s disk. So despite the lousy seeing, the little scope lived up to the Maksutov reputation as a fine planetary instrument.

I did see some off-axis glare from Betelgeuse and Mars, but only in the 32mm Plossl. I am going to do some more testing to see if that is a scope issue or, as I suspect, an eyepiece issue. Also, getting the scope on target using the 8×20 straight-through finder was not difficult but it was uncomfortable, and usually required me to move my chair, squat behind the scope, and go back and forth between sighting down the tube and squinting through the finder. It’s doable, it’s just not fun, and something like a 6×30 RACI should be a high-priority upgrade if you get one of these.

This morning before work I got some photos of neighborhood birds, using both the Astro-Tech dielectric diagonal and the prism diagonal that came with the scope. Be aware that that both my camera and my photographic method are primitive. The camera is a 4-megapixel job more than a decade old now, and while its rotating barrel design is convenient for digiscoping, it just can’t keep up with the better modern cameras. Also, hand-holding the camera to the eyepiece means that I’m usually the most mobile link in the system, so any fuzz or blurring in the photos is possibly caused by my minuscule shakes rather than by the optics. To try to eliminate that factor as best I could, I took several exposures of each target and picked the sharpest from each set for the comparison images. In all of the comparisons between diagonals, the photo through the prism is on the left, and the dielectric photo is on the right. Other than having been put into the same image for comparative purposes, the photos are completely unprocessed: no sharpening, no levels or curves, no rotation, and I didn’t even flip the photos through the star diagonal, which are reversed left-to-right. Click each image for the original, full-resolution version.

The moon last night. The view through the dielectric diagonal was markedly sharper and more contrasty, and these unprocessed photos, taken just minutes apart, bear that out. The full-resolution dielectric photo shows a very thin line of purple chromatic aberration around the limb of the moon, but I couldn’t see it at the eyepiece despite being on the lookout for it.

This fellow was sitting a tree that I have paced out at about 70 yards from my driveway. Again, the dielectric photo (right) has better contrast, and look at the difference in the color of the background sky. This is the same bird and I took the photos about 2 minutes apart.

This dove was quite a bit farther way. I haven’t paced it out, but this powerline must be well over 100 yards from my driveway. Notice the scale of the bird in the photos and the pronounced drop-off in detail compared to the little songbird above. Detail is probably a wash here, but the dielectric photo has better contrast and again the background sky is more blue.

One more point to make is that I hardly ever post raw images. Almost every photo can benefit from a little processing with Unsharp Mask and Curves (I use GIMP, which is free–see details on what I do to each photo in this post). Here are the best dielectric photos of the moon and the songbird, with the unprocessed photo on the left and the lightly processed version on the right (this time I did rotate the moon and flip it to its correct side).

So, what did I learn from all of this? The SkyWatcher 90 Backpacker is a decent little scope. I couldn’t see any optical problems, and I was impressed to see details on Mars at 100x with the included 12.mm Plossl and the Astro-Tech diagonal. Views of birds are as good as those I used to get with my Orion Apex 90. But the supplied diagonal is not good, and really limits the views the telescope is capable of providing. If you get one, replacing the diagonal with even an inexpensive mirror diagonal should be a top priority. Let me put in a plug here for the Astro-Tech dielectric diagonal. It consistently throws up a great image–it’s the diagonal I used when taking the Apex 127 to 514x for that double star split–but at $69.95 for the 1.25″ version it is no more expensive than some ‘entry-level’ mirror diagonals.

The supplied prism diagonal does have one potential use: if you have an old binocular laying around, you can disassemble it and use one of the objective lenses to make a proper finderscope, and if you include the diagonal it could even be a RACI. Mounting a bigger homemade finder to the scope will take some ingenuity, but I figure anyone who likes to tinker enough to build a finder in the first place can be trusted to come up with a mount as well.

So I now feel confident enough to recommend the scope, at least, although the mount is still a question mark and the diagonal and finder are troublesome (as expected). I don’t know how the scope performs compared to the Celestron C90, which is also on sale, because I haven’t had the chance to test them side-by-side. But with a little luck I may get that chance soon.

Hopefully this weekend I’ll have time to get the mount up and running. Stay tuned.

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SkyWatcher 90mm Mak unboxing

February 29, 2012

The Sky Watcher 90 mm Backpacker telescope that I ordered last week was delivered today. I wasn’t sure what all to expect in the box–the list of included items on Amazon is maddeningly unformatted and cuts off midstream. I thought I’d do a series of unboxing photos to document what’s in there for anyone who is considering buying this scope while it’s on sale.

Inside the usual plain-Jane shipping box is the actual product box with pretty pictures.

Inside that box are a backpack, the mount base, the warranty, and–yep–another box, all in their own plastic bags.

I was expecting to find the mount inside the backpack and the telescope inside the box, but I was wrong. The backpack contained the telescope tube–still swaddled in packing material in this shot–and the smaller boxes containing the accessories.

As with all the scopes I’ve bought new recently, the tube was wrapped in tissue paper to protect the finish, then cocooned in bubble wrap, then put in a plastic bag. Note the enclosed silica gel pack and “don’t blind yourself” warning tag.

Accessories, left to right: 90-degree prism diagonal (I was hoping for a mirror diagonal), 8×20 optical finder, and eyepieces. The eyepieces are 25mm, 12.5mm, and 6.3mm Plossls, all with silver barrels and stamped “Multi-coated”.

The back end of the scope, showing off the finish–which is insanely gorgeous–and the little descriptive plate with the scope’s specs. Note that the meniscus corrector plate up front is coated, not multi-coated or fully multi-coated (these are classes of anti-reflection coatings that improve light transfer through the scope; fully multi-coated is best).

Inside the smallest of the nested boxes: the mount, an L-bar adapter, the controller and cables. The L-bar was a nice surprise. Pictures of the assembled scope show the scope mating directly with the mount via its dovetail bar. The L-bar allows one to mount the scope upright instead of on its side, or to mount other devices with 1/4-20 mounting bolts, like cameras, binocular mounts, and other sport optics. Some thought went into the other accessories, too: there are a couple strips of sticky-backed Velcro so you can hang the hand controller on the side arm of the mount.

Everything set up, with an ink pen and the spare eyepieces (1.25″ barrel diameter) for scale. Note the leveling bubble on the mount. I was pleasantly surprised by the tabletop base. It looks plastic-y in pictures but it’s a nice big piece of aluminum with big rubber feet at the corners and a knurled hand-knob underneath for turning the 3/8″ bolt that goes into the bottom of the mount itself. That means the mount can go on any platform with a 3/8″ bolt, which includes most of the better photographic and surveyors’ tripods.

I had little time this afternoon and didn’t want to mess around with putting batteries in the mount and learning how to use it, so I put the scope on the Manfrotto CXPRO4 I use for museum photography and birding. This hall-of-mirrors shot is a typical view down the guts of a Mak. Incoming light passes through the meniscus corrector plate up front, bounces off the primary mirror at the back of the tube, then off the secondary mirror–not a separate piece of glass but an aluminized spot on the back of the corrector–then through a hole in the center of the primary mirror, then either straight into the eyepiece or, more commonly, off a mirror or through a prism that bends the light path by 45 to 90 degrees so you can look down to observe instead of crouching behind the tube to peer through it. The white dot farthest in is my ceiling light coming down through the translucent dust cover on the vertically-facing eyepiece. If you got lost among all of those reflections, no worries–see the ray-tracing diagram for a Gregory Maksutov here.

Outside, ready to go. Note the purplish color of the meniscus, caused by the magnesium flouride anti-reflection coatings. On refractors, the best fully multi-coated lenses look like dark-green holes, they just swallow incoming light like you wouldn’t believe. From what I’ve seen and read, catadioptric scopes like Maks tend to have correctors that are almost invisible if they have top-of-the-line coatings. This less well coated corrector shows some reflections, but in truth the difference is slight, just a few percent of the total incoming light. To see some photos of the correctors on other 90mm Maks, including a Questar, see Ed Ting’s 3-way comparo here.

I was all set up to take some pictures of the male hummingbird who sits in the top of our neighbor’s tree, but the little sod must be psychic. Every time I got the camera settings right and the camera to the eyepiece, he’d fly away. My time was limited and eventually I had to give up and go do other things. You can see some birding photos I got through my old Orion 90mm Mak, including what might be the same hummingbird, here.

I knew from the online UPS package tracker that the scope was coming today. For the past week, Weather Underground was predicting clear skies tonight. But sure enough, the New Scope Curse struck, and about sunset the sky went from a few scattered clouds to completely socked in. So the only views I got through the scope today were of a distant treetop to get the finder aligned, and a few seconds’ observation of that rotten hummingbird. Everything looked good and I didn’t see any obvious problems, but starlight will be the real test, as it is for any scope. Not tonight, unfortunately!

In lieu of a first-light report, here’s what I learned from the unboxing and my few minutes outside with the scope:

HOTS:

  • The scope is real purty. Fit and finish are very nice.
  • Mechanics seem good. Focusing is smooth with no detectable backlash, at least at the low magnifications I was using during the day. Stay tuned.
  • Given my extremely limited time out with the scope, the optics seem fine. At 50x with the 25mm Plossl, I was counting scales on a tiny pollen cone in the top of a tall pine tree half a block away. I had no problem focusing directly to a crisp image, without having to flop around on either side of focus until I got it right–again, under the forgiving, low-mag conditions I was using it in today. No false color detected, but I haven’t really put it to the test yet.
  • I haven’t used the supplied mount yet, but it gives a reassuring impression of solidity and has some nice touches I didn’t expect, like the built-in bubble level, included L-bar adapter, and Velcro strips for hanging the hand controller from the side arm.

NOTS:

  • I’m disappointed that the diagonal has a prism rather than a mirror. Mirrors tend to be much sharper, especially at the high magnifications Maks are capable of delivering. Now, most Mak spotting scopes come with 45-degree prism diagonals so this one isn’t behind the curve, it just seems weird that essentially all Mak-makers (Questar excepted, obviously) hobble their scopes as shipped with inferior diagonals.
  • I knew this coming in, but the supplied finder is tiny, and uncomfortable to use since I have to crouch behind it. Unfortunately I don’t have the 6×30 RACI anymore that I used to use with my little Maks. For review purposes I will use the supplied finder, but when it’s just me using the scope for pleasure I am either going to have to move the 9×50 over from one of my bigger scopes or buy another optical finderscope (or, just maybe, see if I can get along with dead-reckoning using a spare red-dot finder I have laying around). Also, the finder bracket is not one of the convenient two-bolts-and-a-spring models but an old-fashioned six-screw job, which means that getting the finder aligned takes about 5 times as long as I’m used to.
  • The choice of eyepieces is odd, because each one is a factor of two away from another one. One of the most common astronomical accessories is a 2x Barlow lens, which effectively halves the focal length of any eyepiece. Eyepieces are often sold in staggered pairs to take advantage of this. For example, my first scope came with 25mm and 10mm Plossls, which when Barlowed gave me four focal lengths to choose from: 25mm, 12.5mm, 10mm, and 5mm. If they were similarly staggered, the three eyepieces included with this scope could have yielded six magnifications when Barlowed. Instead, they give just four: 25mm, 12.5mm (both natively and with the 25mm Barlowed), 6.3mm (both natively and with the 12.5mm Barlowed), and 3.2mm. So the 12.5mm eyepiece is superfluous if you have a Barlow. On the other hand, this bundle is clearly aiming for everything-a-beginner-needs-in-one-box completeness, and if you don’t have a Barlow yet, having three eyepieces is very convenient. Most other Maks come with just one (although some C90 packages come with two); advantage SkyWatcher.
  • The optics are coated rather than multi-coated or fully multi-coated. I haven’t had a chance to see if this makes a detectable difference at the eyepiece. It only strikes me as odd because I have seen so many affordable Chinese-made scopes that are multi-coated that I had started to assume that was the new baseline.

I see that I went on at much greater length about the nots than the hots. Don’t read too much into that, it’s mostly whinging about accessories which are just as good as or better than those shipped with most other 90mm Maks. The only criticism that applies to the scope itself has to do with a level of lens coating that may not make much difference in actual practice. Remember that these are all first impressions; I have not yet had the scope out under the stars. Until I have done that and reported back, take this post for what it is: a list of parts.