Starry Vistas by Don J. McCrady


Astrophotography Equipment

Telescope:  I have done all my astrophotography since 2004 using a Takahashi Sky 90A 3.5" doublet apochromatic refractor, it weighs just 7 pounds, and is a mere 13.8" long with the dew shield retracted.  The Sky 90 operates normally at f/5.6; however, for photography, an f/4.5 focal reducer / field flattener is a required accessory.  This accessory performs superbly, giving me sharp stars all the way to the edge of my field of view.

As a planetary instrument, the Sky 90 is not ideal.  However, if you view the planetary photos on this site you may well see that it can still perform much better than one would expect.  To get decent planetary shots, the native 504mm focal length of the scope must be extended.  There are several ways to accomplish this.  First is the Takahashi 1.6x Extender-Q which turns the Sky 90 into an 800mm f/8.9 instrument, although that is still too short by itself for planetary instruments.  A second way is to use a 5x PowerMate from TeleVue, which brings the scope up to 2500mm and f/28.  On those rare occasions when the seeing is steady enough, I've successfully stacked the 5x PowerMate on top of the Extender-Q to achieve a focal length of 4000mm and f/44!

A camera angle adjuster is also a highly useful accessory, allowing the camera to rotate without losing focus.

Because I image from light-polluted areas, I have a Hutech LPS filter permanently installed in the imaging train.

I use a RoboFocus motorized focuser to provide repeatable automated focusing.  Prior to getting this, getting correct focus was one of the least enjoyable aspects of astrophotography, and I wasted more than one night getting hours of data that turned out to be out of focus.  Coupled with automated focusing software such as FocusMax, getting precise focus is very easy and quick.

Mount:  My first astrophotography-capable mount was a Losmandy GM-8 equatorial mount with the Gemini GOTO system, which I used for two years.  While this mount performed very well unguided (~2 minutes unguided at an image scale of about 3.77 arcsec/pixel), it had severe backlash issues that made autoguiding a hit-or-miss proposition.  Also, when I upgraded to the 4 pound STL camera and the corresponding DEC counterweights, the mount was pushed beyond its imaging weight-limit.

In September 2006 I sold the GM-8 and replaced it with a Takahashi EM-200 Temma2 mount.  The EM-200 has a much heavier photographic capacity, between 30 and 40 pounds, which will allow for an eventual telescope upgrade.  Its polar alignment scope is just plain slick:  2 arcminute alignment in seconds, which really cuts down on setup time.  Its periodic error is very low, giving me up to 4 minutes unguided, and its autoguiding performance is excellent.  The Temma2 controller is not quite as good as the Gemini system, but the pointing accuracy is still extremely good.

Camera:  I made a low-budget start by using unmodified Phillips ToUCam Pro web-cam, which is a 640x480 colour chip.  I still use it for planetary and lunar photography, since its 5.6µ pixels give me maximum resolution when the seeing allows.  At the time when it was my only camera, attempted a couple of DSO shots with it, notably M42, but that's not its forte. Then I purchased the highly popular Canon EOS 300D Digital Rebel (digital SLR).  It's a nice match for my scope, offering a 6 megapixel array (3072x2048) and the ability to do arbitrarily long exposures, all for much less than a CCD camera would cost.  It's a great general daytime camera too, which makes it easy to justify to one's spouse.  While I used it successfully for two years, it did have some drawbacks which made me want to upgrade.  For example, DSLR's typically have poor red response because of the built-in IR-cut filter.

STL-4020MIn May 2006 I took delivery of my next step in CCD astrophotography, an SBIG STL-4020M with colour filter wheel.  This is a 2048x2048 camera with 7.4µ pixels, the same as the Digital Rebel.  However, since it doesn't have a Bayer matrix for one shot colour, it has improved resolution over the Digital Rebel, not to mention a lot more sensitivity (especially in the reds), and much less noise.  The monochrome sensor allows me to take LRGB images, and I also purchased an H-Alpha filter for emission nebula.

The internal guide chip built into the camera works pretty well for luminance and RGB exposures, but can be a pain for narrowband Hα imaging because it attenuates light from potential guide stars.  In November of 2008 I purchased the SBIG Remote Guide Head, as well as a Fujinon 50mm C-mount lens (with a 2x extender).  This allows me to guide using a 100mm guide "scope" and thus avoid the problems associated with guiding through filters.  As an added bonus, by turning off the internal guide chip the amount of dark noise is reduced and an annoying source of amp glow is removed.

I use Astrodon filters:  for LRGB I use the tru-balance clear, red, green, and blue filters.  For narrowband imaging I use 3nm H-alpha, Sulfur-II, and Oxygen-III.  Since the filter wheel is only 5-position, I have to swap them out when I switch from LRGB to narrowband.

Software:  For DSLR astrophotography, there is no better choice than Mike Unsold's Images Plus.  This is an extremely powerful image processing tool that directly supports my Digital Rebel (and other camera models), inasmuch as it can automate the shutter release in a specified sequence and duration of exposures.  It also does a good job of RAW file conversion, dark & flat calibration, as well as final processing.  The software is a bit clunky and hard to use, but that is mitigated by Mike's excellent video tutorials, which explain not only how to use each feature, but why you'd want to use it.

To capture images with my STL-4020M, I use Maxim/DL from Diffraction Limited.  It has some great features for automating the acquisition process, and is fully scriptable.  It integrates well with FocusMax and many other third-party tools.

I also use the ubiquitous Adobe Photoshop CS3, a must-have application for any kind of image processing.  Several useful third-party tools, such as GradientXTerminator and Noel Carboni's Astronomy Tools make this an extremely powerful image processing tool.

Visual Observing Equipment

12.5" Discovery PDHQ

Telescope:  For visual observing, I took the maxim "aperture rules" to heart, and when I got serious about observing I purchased a 12.5" Dobsonian, a Discovery PDHQ.  Although Discovery Telescopes seems to be defunct, they produced extremely high quality optics.  This model is easy to handle by myself (only 65 pounds), and easily fits into the trunk of my Acura Integra.

For finding devices, I have a TelRad for rough pointing, and a right-angle correct-image 7.5x50 finderscope. The combination makes for trouble-free star-hopping. Both are subject to dewing up in high humidity, so I heat them with the Kendrick Dew Remover system.

Eyepieces:  For several months I observed with a couple of Sirius Plossl's, 32mm and 12.5mm, and a 5mm Vixen Lanthanum.  These were very decent eyepieces, and I don't hesitate to recommend a good quality set of Plossl's to any observer.  However, since my Dobsonian is a non-driven alt-az mounted, I soon got tired of my images zipping through my field of view before I had a chance to really observe them.  Also, Plossl's perform much better in the center of the field than at the edges, so it was quite a chore keeping my target in the sweet spot.  I decided that some premium wide-field eyepieces were required to maximize my enjoyment at the telescope.

Over the course of about a year I eventually acquired the following eyepieces:

  • Eyepieces24mm Panoptic
  • 13mm Nagler Type 6
  • 9mm Nagler Type 6
  • 7mm Nagler Type 6
  • 2.5x Televue PowerMate

Note that all my eyepieces are 1.25" barrel sizes.  While a 35mm Panoptic would be an attractive addition to my collection, it implies fiddling with adapters when swapping between 1.25" eyepieces.  Worse yet, from a cost perspective, all my nebula filters are 1.25", and I'd have to buy new ones to fit 2" eyepieces.  I'd also have to get a 2" diagonal for my refractor.  Most likely I'll just stick with the 1.25" eyepieces I have and be happy with them.

Filters:  I've found a good set of filters to be an absolute necessity when it comes to observing certain objects.  I have a complete set of Meade colour filters for planetary viewing, as well as a Meade neutral density lunar filter for the moon.  But by far, my most useful filters are my nebular filters, which I'll briefly discuss here.  For an excellent site that discusses all kinds of filters, please visit

Nebular filters are often referred to as LPR filters (Light Pollution Reducing).  A true LPR filter is a broadband filter, which means that it passes a very broad spectrum of light, rejecting only a few wavelengths. Generally these wavelengths correspond to sodium and mercury, prime ingredients of light pollution produced by street lamps.  In theory, these broadband filters filter out all the bad light, leaving only the good light, improving the contrast of all deep sky objects.  I have a Meade Broadband filter for this purpose, and I have to say I haven't had much use for it.  It doesn't improve my views significantly, if at all, and I never use it any more.  Another filter that falls into this category is the Orion SkyGlow filter, but I've never tried that and can't specifically comment on it.

Far more useful are the so-called line filters or narrowband filters, those that filter out all wavelengths except for a few specific lines.  In this category, I have a Meade Narrowband filter, a Lumicon OIII filter, and a Lumicon H-Beta filter.

The first two of these, the Meade narrowband and the Lumicon OIII, are quite similar in that they are useful on the same classes of objects: bright emission nebulae and planetary nebulae.  By far, my favourite of the two is the OIII filter, which produces stunning contrast improvements on almost all bright nebulae.  Some of the objects that it works best on are (in no particular order): the Orion Nebula, the Swan Nebula, The Lagoon Nebulae, the Dumbbell Nebula, the Ring Nebula, the Helix Nebula, the Veil Nebula, the Rosette, and Thor's Helmet, to name just a few.

The H-Beta filter is far more specialized.  Lumicon dubs it the "Horsehead Nebula Filter", as that is the most famous object it helps reveal.  It also is the filter of choice for the California Nebula and the Flaming Star Nebula, to name just a few.  (It is also the single best Mars filter I've encountered.  I accidentally discovered this when, on a lark, I tried all my nebular filters on Mars during the 2003 opposition, and was absolutely stunned by the detail that it helped reveal.  Surface features such as Sinus Sabaeus, which had been smoothly outlined without the filter suddenly became jagged when using the H-Beta.  The polar cap also became blindingly bright.  If you feel uncomfortable paying over $100 for a filter that only works on a couple of nebulas, perhaps this will help convince you that the H-Beta is far more useful than it appears at first glance.)