Category Archives: Equatorial Mount

Geminid Meteor (and other) Shower Tips

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Psst. It’s not a secret but we love meteor showers here at StarCircleAcademy.com. So much so, that we frequently schedule expeditions to capture meteors in interesting dark sky locations.  The latest expedition is in a few days. But if you look through our catalog of events, (e.g. the latest and this one) you’ll see we’ve been hunting meteors for quite a long time.

Star Man and Perseus [C_059960-1]

The things you want to happen for a meteor shower include a non-intervening moon. Showers peaking on or near full moons are usually disappointing. Then, of course you’ll will want good weather, and an interesting foreground.  However there is no cookie-cutter approach to getting that to all work out.  For the Geminid meteor shower, it’s useful to know that Gemini rises in the East a little after sunset and sets in the west around sunrise. If you want to get the MOST meteors, you generally want to shoot after midnight and before dawn (so southwest), and thus southwest is the direction you’ll want the darkest skies. But if spending midnight to dawn somewhere is not practical for you, consider finding dark skies facing the south East instead.

Meteors CAN appear anywhere in the sky, however, so even when we suggest dark skies to the south, do not let that stop you from finding dark skies in any direction.  The interesting foreground you want may only work with a Northern view.

We describe at length how to find dark skies in this article and in the discussion consider alternatives, such as  distance, weather, and goals. In that article we also link to a resource to help you find dark skies. But do not be mislead: not all dark skies are created equal and there is really no substitute for having been in a location a time or two to know how “dark” is “dark.” Understand that weather conditions significantly affect the darkness of skies. Dry, arid places as a rule will be darker than moister climes.

Once you have landed on a place, you need to know how to shoot those meteors – so we have an article for that, too!  And once you get those little streakers, you will want to be confident that they really ARE meteors (most of the time they are not). So if you want to know that what you got are indeed meteors, please read our article on identifying those streaks accurately.

Satellite Flash (Iridium) [5_033852-4br]

 

To fully enjoy a meteor shower we suggest the following preparations:

  1. Dress appropriately. Assume it will be 20 degrees F colder than the stated overnight low. Not because it will be colder, but because with no sun to warm you at all plus little activity it will FEEL colder.
  2. Bring a fully reclining chair or sleeping mat so you can lay down and look straight up (or toward the darkest skies).
  3. Bring a blanket or sleeping bag and a pillow.
  4. Bring some hot (and/or cold) beverages in a thermos and some snacks.
  5. Set up you camera with an equatorial mount to track the skies, or just point it toward the dark. Use an intervalometer to automatically take photos (using the settings we suggested in this article – don’t want to read that: try ISO 6400, maximum aperture, 20 seconds or less).
  6. Bring a friend. You will be encouraged to hear your friends going OOOH and AAAAAH when you do – and if nothing else, you can keep each other awake and share stories.
  7. Be sure your family knows where you’re going and when you’ll be back (if they aren’t coming with you).

There is always more, of course, but ultimately we suggest that when possible, you consider joining us when we schedule a workshop or field expedition.

Happy space debris hunting to you!

Astrophotography Equipment Follow Up

Andromeda

New Equipment vs Old

In the years since I began writing about astrophotography techniques and equipment (including review of the Polarie, pointing tips, and processing techniques) things have obviously changed for me.  For one, I’m not working at astrophotography as hardcore as I expected.  The reality of managing an informative website (this one!), creating publishing and supporting tools, conducting fairly frequent expeditions and workshops, writing and improving content for webinars *AND* having a day job means I have to temper my enthusiasm. Or to say it more plainly, have my enthusiasm tempered by reality.

However a student asked me this question and I felt it was a good topic. The question:

I read your review suggesting the Orion Astroview EQ mount with optional dual axis motors. I’ve been looking for a cheap way to do decent tracking and have considered making a homemade Barn-door mechanical tracker to something more reliable (motor driven).

On Orion’s website, I find their Astroview EQ mount (#09822) and the dual axis motors for the Astroview (07828).

Soooo, my question is this: Since you wrote that article, is that still the most bang for your buck, or have you found something better/bigger/cheaper?
— Bruce L.

As I noted in my article, there are definitely bigger and better and significantly more expensive things … though nothing cheaper that I’d recommend. The Polarie is in the same price league.  After I made my recommendation my Astroview suffered a series of blows to the declination drive that rendered the drive useless.  The first blow was that the locking nut fell off in the dark and was lost. Once I replaced the lost piece (at about $35) the next blow was quite literal and it bent the drive axis rendering the motor useless. The truth, however, is I really didn’t need the second axis at all and I’d have saved a few bucks by only buying the single drive motor to begin with.  The Astroview is just beefy enough to carry the weight of my Orion 80ED refractor and a camera.  And to be quite honest since it is lighter and not a “GoTo” mount it’s actually easier to set up and take down than it’s bigger cousin, the Sirius mount. But the Astroview is nowhere nearly as well made.  So yes, I’d still recommend an Astroview as a minimum viable solution… provided you stick with a camera and telephoto / normal lens to do imaging.  Most telescopes worth mounting on the Astroview will cross the boundary of what the Astroview is designed to carry and will be too heavy for good operation.

Automating Focus – Two Steps Forward, One Step Back

I had upgraded the focuser on my 80ED to one sold by ScopeStuff (#RNFR) – a $320 motorized focuser. That focuser proved easier to use and more versatile, but I later found it coming apart and it required some heavy tinkering and investigation to get it working again.  I also realized that the system was not that well thought out – it was designed to have the motor base mounted to the focus TENSIONING screw rather than attached to a fixed screw on the focuser.  That’s probably in part why when I got it, the tube would not travel all the way through the almost 4 inches of focus. I’ve restored it to operation but it still won’t travel in the final 3/4 of an inch… that’s fine, however as I have never needed that much in-focus – I’m usually working with the focus tube nearly fully extended.

In focus - moving the camera inward, toward the front element of the telescope, thus shortening the overall length.
Out focus (aka back focus) - moving the camera outward from the front element lengthening the apparatus.

Is A Barn Door Tracker A Good Solution?

Let me address the question about a Barn Door Tracker.  There are no places that I have found to buy barn door trackers, it’s strictly a home-built type of thing. As I explain in the Astrophotography 101 webinar, a barn door tracker is a form of an equatorial mount that has been simplified to drive only one axis (the right ascension) and with a limited tracking time.  Various designs like the double arm version improve tracking accuracy while complicating assembly. My personal bias is that even though I’m pretty handy with tools I’d rather spend $400 on a fully built system than $80 on parts and 10-20 hours of my own labor building and perfecting the system.  I suppose if someone handed me a robust kit for $100 and told me I could assemble a motor driven barn-door tracker in an hour or less, I’d give it a try.  But at much more cost in time or money the barn door tracker starts bumping into fully built solutions like the Orion Astroview and the Vixen Polarie or the iOptron SkyTracker.

One of the principle impediments with all things astrophography – and part of the reason I created the Astrophotography 101 course is that there is a LOT of language used that is foreign to most people. And, there are legion of difficult choices to make. For example, I recently bought a William Optics Telescope. It is a well built, heavier than expected, refracting telescope that features a power focuser. Perhaps as a surprise to the uninitiated the “power focuser” is not actually powered (motor driven), it is an improved version of the manual Dual speed Crayford focuser and the term “power” implies it’s ability to hold focus without slop or creep – even if the other end of the focus mechanism is a pretty substantial camera.

I had hoped my existing finder scope and guide scopes would easily attach to the new William Optics telescope, but they won’t. The fittings are all different. For the most part astronomy and astrophotography equipment is a wild west of non-compatible, non-interchangeable components.  Much like you see if you try to use a Nikon lens on a Canon camera.  Or an intervalometer built for a Sony on a Lumix camera.  The difference, at least to my way of thinking, is that the compatibility of components is much better spelled out in the camera world than the astronomy world.

What about the Polarie?

The Polarie will work well with normal lenses. When I mounted my 70-200 with a 1.4x and the Canon 5D Mark II (or 40D) on the Polarie, tracking accuracy was pretty bad – but not directly because of the Polarie. The problem is that the systems is not balanced and there are three different points around which the apparatus gets sloppy: at the connection between the ring-collar of the lens and the head mounted on the Polarie. At the point where the head is attached to the Polarie screw, and where the “collet” with it’s two thumb screws attaches to the Polarie.  Invariably one of those would become loose enough that it would slip.  I found that putting a counter weight at the end of the lens reduced slipping and improved the tracking – but it’s a hassle and highly dependent on where you aim.  A true equatorial mount is easier to balance. The Polarie system works better when there isn’t a lot of torque around those attachment points.

In summary, I like and use the Polarie because it’s compact, light, not bulky and easy to take with me literally anywhere I go. But I would not use it to take serious astro images.  The Polarie best fits Landscape astrophotography.  For example, below is a 63 second exposure using a Canon 40D at 1000 ISO, f/2.8 at 16mm.  Using the 500 rule, star streaking would become apparent at about 12 seconds.  In this small size there is nothing at all visible, but do notice how the foreground head frame at Bodie State Historical Park is blurred – that’s because the Polarie was tracking the sky at 1/2 sidereal (star) rate. The photo has been exposure enhanced (brightened) to see details, and noise reduced a bit.

B_180-002309_sm

 


Here is an exposure that is a bit more germane. Two exposures, actually. One focused for the hand-lit tree, the other focused on the stars and both were combined in Photoshop.

Heaven Bound [C_075698+701]

De Streaking

In a recent article I explained how you can bump up the brightness of stars using a simple layering trick in Photoshop.  In this article we will be going in the opposite direction. Instead of increasing the contrast of stars our goal will be to reduce the streaking that results from long exposures or exposures at a long focal length.  For background on streaking, please refer to the article The 600 Rule which as rules go is a pretty bad rule.

Streak Reduction Procedure

The original image, cropped.

For the streak reduction procedure we only need one image.

  1. Open the document in Photoshop.
  2. (Noise reduce as needed – method to be described in a column coming soon)
  3. Duplicate the background (Ctl-J).
  4. Change the new layer blend mode to Darken.
  5. Select the move tool to “nudge” the top layer in the direction of the predominate streak (in this case up one and right two).  It helps to zoom (Z) pretty far before making the nudge.
  6. Apply levels and curves to brighten the image and correct the color. The color correction process is described in this article.  The easiest way to apply an adjustment layer is to view the Layer tool (key F7) and click the adjustments icon at the bottom as shown here:

    To make it easier to see what you are doing, you can apply a curve to lighten the image. Make sure to drag any temporary adjustment layer to the top of the layer stack.

The nudge operation may result in foreground elements being noticeably duplicated like the tree tops below:

Background plus nudge foreground, unmasked.

Fortunately it is easy to undo that duplication by masking off the area by painting black on a layer mask.  Here is the same darkened layer combination, but I have created a mask and painted out the area around the duplicated tree tops. To create a mask click the icon that looks like a camera on the Layer Tool – it’s just to the left of the adjustment icon shown earlier.

Tree duplication has been masked off here.

This image looks better. Now we might want to apply the bump operation using the combined background and nudged darken layer.  There are three ways to get the layers combined: use flatten image, select the two layers and select layer-merge, or – and this is a really useful trick, use the keys: Ctl-Alt-Shift-E (that’s how I got Layer 2).  On the Mac you use Option rather than Alt.  Two ways to get to the flatten or merge operations include clicking on the tool bar under “Layer” or clicking the tiny little menu icon at the upper right of the layer tool window.

After a little bump:

Caveats

This destreak method works best if you are not using a wide or ultra wide view. With a really wide view, the star streaks are not uniform. The closer the stars are to the north or south poles, the more curved their streaks will be.

In another article I will walk through how you can composite together images taken at different times or exposures, as was done below.

DeStreaking [C_049387+406]

Astrophotography – The Polarie

We have a once-in-a-while webinar on beginning Astrophotography. The purpose of the webinar is to get people acquainted with the tools and techniques required to delve into this interesting genre of night photography.  As we teach in that webinar the single most important piece of equipment you can buy is an Equatorial Mount.  An Equatorial mount is an apparatus that counteracts the rotation of the earth so that your camera can peer at the same place in the sky for long enough to capture an image without streaks. There are many equatorial mounts that range in price from almost nothing (and not even worth nothing) to more expensive than logic would dictate.  For more background please see our survey of Astrophotography Gear.

One of the newer pieces of equipment in the arsenal is a less-than three pound piece of gear called a Polarie.  Here is what it looks like with a ball head attached to its face.

Polarie – Close Up

What Polarie Can Do

As noted earlier, the primary purpose of Polarie is to counteract the effect of the earth’s rotation so that objects in the night sky can be exposed longer without getting streaking. Below are examples of 42 second exposures using an effective focal length of 215 mm. The image at the left is with the Polarie turned on in normal mode, the middle image is the same length exposure but in 1/2 speed mode, and the right is what you get if you use no tracking at all.

Polarie Test - Telephoto

Tracking is less critical when shooting with wider angle lenses. I ran a test with a 200mm telephoto lens because it is a more difficult scenario. For example when shooting the Milky Way, an effective focal length of 10 to 50mm makes more sense.

A Critical Look At Polarie

I purchased only the Polarie unit (about $400 USD) not any of the accessories. The unit is deceptively heavy at almost 3 pounds but at that weight it is still – and by far – the lightest equatorial mount you can find. The only other device in its weight class at present is the Astrotrac with a starting price about twice as much. The Astrotrac does come with a better tripod mount, however at a total cost of around $1300 USD.  I paired up the Polarie with my Canon 50D and the 70-200 f/4 lens.  The addition of a Giottos ball head brings the total weight of the equipment attached to Polarie to about 6 pounds.

The Positives

  • Inexpensive
  • Good instruction manual
  • Mostly easy to set up and to use
  • Suitable for a beginner
  • Good power for the price.
  • Can be powered with mini USB (or two AA batteries). Claimed life is 4 hours on AA batteries but mine lasted at least 6 hours using rechargeable batteries.
  • Compact and MUCH lighter than almost everything else.
  • Can be used in Northern or Southern latitudes.
  • Tracks at star, solar or lunar rates (and yes, they are all different) as well as a 1/2 speed rate which should be good for Landscape Astrophotography.

The Negatives

  • The back plate can be unscrewed to peer through the axis of the motor and also houses a built-in magnetic compass but the plate is almost flush to the Polarie body and it is quite hard to grip.
  • The inclinometer (angle measurement device on the side) seems like a good idea except that the markings are so small and coarse that to my eyes it is illegible.  The lighted inclinometer *might* help if the North Star is obscured by trees or such.
  • The front plate has a 1/4″ retractable bolt and attaches awkwardly to the motor plate with two thumbscrews that are hard to reach once a head is on the motor plate. I would have preferred that Polarie supply a 1/4 to 3/8″ adapter since most good heads attach via 3/8″ bolts.
  • The battery compartment door is a nail buster to open.
  • Since Polarie will certainly be used with a DSLR camera, Vixen really missed an opportunity to add a remote release cord – I see no jack for one.
  • Not sure what the point of the flash shoe is. I do see the Vixen has another (much larger) inclinometer that can be attached there, but you may be able to do better using an application on your smart phone.
  • The optional polar alignment scope is expensive, and bulky. It’s also complicated to operate because you must remove the ball head and camera from the device. BUT the weight of the camera and ball head is likely to create enough “sag” that the careful measurements will be wasted.  We like the SkyTracker much better in this regard.

There is a sight hole to line up Polaris – the North star. I used only that method to align Polarie and got fair results. To get really long exposures one of two methods will need to be undertaken to increase the alignment accuracy: either invest in a Polarie polar alignment scope at almost double the cost or do drift alignment. Drift alignment is not simple and probably would frustrate the aspiring astrophotographer. The Polarie can be purchased with an optional ratcheting tripod base which might be a good idea, however the stated load capacity of the bundled tripod seems too low to use with a heavy camera.

Noteworthy

Remember that you will need at least two heads and you’ll want them both to be ball heads for optimum configurability. The head on the tripod should be sturdy – see below for why.  Below I refer to tripod head – the apparatus that joins the tripod to the Polarie, and to the Polarie head – which is the hardware used to attach a camera to the Polarie.

Problem Areas

In addition to the negatives listed above, there are several other sources of problems including every point where one element attaches to another. For example: the Polarie base if not attached securely to the tripod head can rotate.  If using quick release plates the attachment point creates another source of rotation. If the camera is not securely attached to the Polarie head rotation can occur there, too. All the pieces together may severely tax a cheap tripod head making it difficult to hold up or adjust the load.  In my configuration I found I had to allow some slouching – meaning I had to adjust the camera so it was pointing slightly above my target and then tighten the head so that it would settle to the right place.

What Can You Do With A Polarie?

Maybe we should have put this section first! Some of these things can only be done with a Polarie are highlighted in RED.

  • Point the Polarie straight up and use it as an automatic panning motor for a time-lapse.
  • Align Polarie and take a series of shots of the night sky – the sky will stay in the same place in every shot – and any minor movement can be compensated for using Astrophotography procedures.
  • Outfit your lens with a solar filter and track the sun (e.g. for photographing eclipses or solar activity)
  • Track the moon e.g. to catch the space station flying across its face, the slow creep of the terminator, or just to get a time-lapse as the moon sets or rises.
  • Double your exposure on a landscape astrophotography shot by using 1/2 speed mode.

For more hints tips and examples on how to use Polarie, stay tuned to this channel!

My first test of the Polarie was to track the radiant point of the Orionid Meteor shower. My attempt was mostly a bust due to clouds, however note how stable the time-lapse is – and remember this spans almost 14 minutes of real-time.

Here are two more ways I’ve used the Polarie – as a horizontal panning device

As a sky tracking device