Telescopes

 

Telescopes for Astrophotography

 

When I first started taking deep-sky astrophotos, most were taken with a Nikon FM2n mounted at the prime focus of a Takahashi Epsilon 160mm Hyperbolic Astrograph. This instrument is basically a Newtonian reflector with a hyperbolic primary mirror, and a Ross-type corrector lens inside the focuser. The instrument is very fast, at f/3.3, which lets you get a lot of shots done in one night's work. The focuser is a magnificent piece of engineering, silky smooth yet big and beefy, and it rotates 360 degrees without losing focus. The camera is mounted to the focuser via a threaded "wide-mount" T-adapter that is both very solid and wide enough to prevent vignetting with 35mm cameras.  

 

Once I got interested in medium format work, I acquired a Borg 100ED refractor.  This scope was typically sold as a set of equipment that allows converting it from its native f/6.4 configuration to f/4 using a four-element reducer lens assembly.  The focuser on this scope offers a 95mm clear aperture to fully cover a 6x7 frame - even 6x9 with an appropriate camera.  I use it with Pentax 6x7 and 67 cameras, so there is some vignetting from the cameras' lens mount flange.  At f/4, it was a good match in exposure times when mounted side-by-side with the Epsilon and using the same speed film.

 

Since the Epsilon 160 couldn't cover the medium format 6x7 frame, I eventually sold it, somewhat regrettably since it was such a fine instrument.  Unfortunately, this can be an expensive hobby, especially once you're hooked, and the Tak astrograph had to go to help defray the cost of an instrument of longer focal length than the Borg 100ED that could cover 120 film.  Such an instrument is the excellent TMB 152mm Triplet Apochromatic Refractor sold by Tom Back or his exclusive dealer in the USA, Astronomics.  The purchase of this scope has an interesting history.  When I first ordered it, the lead time was about six months, but this soon grew to over a year.  Just a month or so before my scope became available, the company I was working for closed and I was out of work, making the purchase of this expensive instrument impossible.  When Astronomics called and said my TMB was ready, I had to decline it since I was unemployed.  A month or so later, I found a job again back in the astrodynamics software business - my real area of expertise, and so all was well from an employment standpoint.  On a whim, I checked the Astronomics web site and found that they had one TMB 152 in stock - my scope hadn't sold yet after I declined it.  With great joy I immediately purchased the instrument and eagerly awaited shipment.  The enormous packing box showed up at my wife's office looking pretty banged up.  We opened it up and sure enough, UPS had managed to destroy the scope, completely puncturing the tube and crushing one of the tube rings.  This isn't the first time UPS has damaged something I ordered, and I make every effort to find alternative shipping whenever possible for my purchases, as should everyone else in this hobby.  After much hassle with UPS, even just to get them to come over and inspect their handiwork, the destroyed scope was returned to Astronomics and it became their problem - I sincerely hope it was resolved successfully, because Mike and company have been an outstanding company to deal with in many transactions over the years.  Eventually a new 152 became available, and was shipped directly from Tom Back in Cleveland, arriving safely this time to start its job as my main astrophotographic instrument.

 

The color correction of the TMB 152 is superb, and superior in every way to the Borg ED glass.  This led me to desire a better short focal length scope, and I subsequently sold the Borg 100ED and purchased a TMB 105 f/6.2 Triplet Apochromatic Refractor, but this time from TMB's European dealer APM Telescopes operated by Markus Ludes in Germany.   There have been several problems with this scope that make me sorry I bought it from a German dealer, since shipping back and forth has wound up costing more than I saved by getting it from him in the first place.  All the problems have been overcome - after two lens replacements - and this now superb instrument is ready to start producing some astrophotographs.

 

Until recently, I have guided my astrophotos manually with a Takahashi FC60 refractor and a Tak 5mm guiding eyepiece. The guidescope sits inside 90mm Losmandy rings on top of the Epsilon.  Since I acquired an SBIG STV autoguider, I've been able to take longer exposures, because my neck and my concentration usually start giving out after about 45 minutes of manual guiding.  The STV is used in place of the guiding eyepiece and star diagonal, and with careful drift alignment of the mount, can guide pretty much indefinitely.  Now that I have two mounts, I still often manually guide wide field shots with normal camera lenses while the STV is busy guiding very long exposures with other instruments.

 

Telescopes for Visual Use

 

I'm not much of a visual astronomer, but over the years I've had a few scopes and binoculars that I've really enjoyed using, especially after I started using an autoguider and have time to enjoy the universe through the eyepiece.  At first, I thought I would save some money and get a big bang for the buck by building my own Dobsonian reflector.  I ordered a 10" f/7 mirror from R. F. Royce and built the scope using a concrete form tube and an MDF and plywood rocker box.  It worked out really well and gave great views of the planets, globular clusters, and other objects, but it was just too cumbersome to be practical.  The tube was over 7 feet long, and the MDF base panel of the rocker box and ground board made it heavy to move around (though very stable once set up).  It took up so much room in the truck that I never took it with me on astrophotography adventures, so it only got used at home, and then very little since it was such a pain to horse the long tube out the back door.  The thick mirror had a long cool-down time that wouldn't have been a problem on an adventure, but it just wasn't good for a "grab and go" situation at home.  I eventually parted out the mirror and other components, but kept the bearings and other mount hardware in case I decide to build another one.

 

A much better choice for portability, rapid set up, and excellent views was the Takahashi FS-102 flourite doublet refractor.  In the photo at the top of this page, you can see the FS-102 set up on the G-11 mount farthest from the truck.  It's alongside the 300mm Nikkor ED-IF f/2.8 AIS lens and was used to guide astrophotos that night, in addition to allowing some visual use in between images.  This scope, bought as an OTA on sale from Astronomics, is the finest small refractor I've used, giving crisp views while being a joy to use.  I tried using it on the APM Giro mount on a heavy duty Bogen 3036 tripod with some success.  The Giro was a very well-made alt-az mount, but it never seemed really stable with the longish Tak tube, and the scope was always much more enjoyable to use on the G-11.  Somewhat reluctantly, I sold the FS-102 to partly finance the TMB 105 purchase, which looks like a bad idea now, given the ongoing problems with that scope.

 

Along the way, I've also owned a Takahashi FS-78 flourite doublet refractor, and I have to say that for the money, it's got to be one of the nicest scopes out there.  It doesn't have the sliding dew shield,  2" focuser, or triplet objective of some of it's competitors, but it's a very sharp  and lightweight scope at several hundred dollars less than the competition.  After some tinkering, I was able to get it to mount on the excellent TeleVue Telepod head, and had a great time using it as a grab and go scope or in the field on an adventure.  I sold the FS-78 to partly finance a Intes MK-69 astrograph, and have missed the portability and sharp views of this small scope ever since. The MK-69 is long gone, too, having not been up to the astrophotography job due to its focuser (although it was excellent optically). 

 

Eventually, I decided that I wanted something that had enough aperture to give good views of the planets and other deep space objects, but would still be portable enough to make it easy to take along on adventures.  After some thought, I took the plunge on a Celestron C9.25 OTA, which, at about the same cost as the FS-78 OTA, must be considered a real bargain in terms of cost per unit aperture.  This scope is easy to collimate when needed, cools down quickly enough for my purposes (there's always plenty of cool-down time while I'm drift aligning and setting up all the gear for astrophotography), and gives very pleasing views of just about everything in a fairly compact and light package.  You still need something like a G-11 to mount it, and I'm not sure there's really any alt-az mount that could handle it with enough stability, but it's a fine SCT and I plan to keep mine for a while.

 

Binoculars for Visual Use

 

Binoculars have always been along on my adventures.  My first real astronomy binocular was the affordable and quite pleasing Celestron 9x63 Pro model.  This was lightweight and fairly sharp optic that could be hand held and had a very good light grasp.  It wasn't really sharp at the edges of the field, but was certainly very good for its modest cost.  It wasn't very rugged, and I had to get mine re-collimated once, but fortunately I know an old Navy optician who did the job for the cost of a beer.  This is an ideal size binocular for most astronomical use.

 

The next move up was a big one, to the outstanding Fujinon 16x70 FMT-SX binocular.  This isn't cheap, but it's not nearly as much as some of the high-end German optics, and the large aperture and excellent optics are really a joy to use.  At first, I was worried about the small exit pupil of this optic due to the relatively high magnification, but in the field it's really no problem at all, and I've really come to appreciate the 16x view.  Cruising the Milky Way in Scutum or Auriga can be simply mesmerizing with this binocular.  At the time I bought it, I knew I'd need a good tripod mount to handle the magnification, so I ordered the LightSpeed DSP.  This is an expertly made CNC aluminum mount that is very compact and easy to travel with - I keep mine in a small pistol rug under the seat of my truck so it's with me all the time on my adventures.  Compared to the parallelogram mounts, this one has a tiny footprint that makes it a no-brainer to take with you and use.  Both the Fujinon and the DSP are highly recommended.

 

Sometime around 2001, I bought my wife a Leica 10x32 binocular to help encourage her emerging bird watching interest.  This is a pricey little instrument, but the optics are first-rate, and I knew from previous experience that you usually get the view you pay for when it comes to optics.  The purchase turned out to be an excellent idea, as my wife is now an avid birder and gets great enjoyment from various optics in that hobby.  This experience led me to look for a binocular that would complement hers, and allow me to enjoy the birds with her but could also be used for astronomy.  The result was a purchase of the very fine Swarovski 8x56 model.  It cost a ton, but at the time I had a much better paying job and it was just within reach after selling off some other items I wasn't using anymore.  What a fine optic!  The 8x magnification is ideal for scanning the Milky Way, for comet observing, and for birds.  It's heavy for continuous hand-held use, but for short views it's really hard to beat.  Great field of view, and very sharp to nearly the edge of the field, with very little if any false color around bright stars.  The moon is fantastic in this binocular, as are the big open clusters like M45.  The large aperture compared to most birding binoculars makes it good for low light views of birds in dense forest or under the trees in our backyard.  This one is a keeper.