Monday, August 31, 2009

Finally Some Photos from the ZenithStar 70 ED

I was able to order a "store demo" William Optics ZenithStar 70mm ED refractor from the W-O online store for $338. This included free shipping worldwide!

I had it shipped to Singapore and paid the 7% GST. At least no unpredictable customs fees depending on the phase of the moon and the arbitrary-ness of Philippines bureaucrats..

The thing has amazing fit and finish. The 10:1 2-inch Crayford focuser is really smooth, and yet does not suffer from creep. The entire focuser also rotates, although as reported by others on the internet, there is a "catch" at one point of the rotation which causes the 360-degree rotation to be not entirely smooth. Not a huge problem however as rotating the entire focuser is not something one does very often..

I also got an EQ-1M quartz-controlled motor drive for the EQ-1 mount which I bought at True Value. Actually I purchased an Orion mini-EQ mount and the motor for S$100 from someone on the SingAstro forum.

Here's an afocal Jupiter at about 140X (12mm Plossl, 3X Meade Barlow). It's not as good as it could be, I've seen much better with this type of equipment. The EQ-1 mount is really horrible, with a lot of backlash that needs to be taken up before the system starts tracking properly.

Also even with good equatorial alignment, the EQ-1M does not track perfectly. I would expect that Jupiter can only remain in the field at 140X (0.35-degree) for about 2 - 3 minutes.

And here's the moon, with 32mm Plossl and 3X barlow.

Monday, June 15, 2009

Nikon DK-21M

I fortuitously found a Nikon DK-21M eyepiece magnifier at Infomax in Market! Market! while looking for some computer parts. Which is a good thing because the computer-assembly exercise has turned out to be a disaster.

Anyway it was around $35 which is expensive as this is a sub-$30 item in the US, but one would have to deal with the hassle of shipping so it ends up about the same.

Here are three viewfinders: Canon EOS 350D, Pentax K20D without DK-21M, and K20D with the DK-21M. It's a usable magnification. Not quite a 5D-class viewfinder, but not too shabby.

Sunday, May 03, 2009

DIY Beauty Dish


One aluminum pie tin (about $1 at SM Department Store):

Mark the outline of your hot shoe flash head on the underside, I used a white board marker:

Cut an H-shaped slot in the pie tin using a Dremel with emery cutting wheel:

Bend the tin outward along the H-cuts (I also used a screwdriver to poke the two screw-holes):

Second ingredient: the lid from a KFC Bucket Meal (free if you eat the chicken!)

I taped a circular aluminum foil cutout to the KFC Bucket Meal lid, this bounces the light from the flash back toward the pie tin, and eliminates the hot spot in the center:

Bolt the KFC Bucket Meal lid to the pie tin (it's easy to poke holes in the plastic using a heated screwdriver or similar):

The metal tabs formed on the underside of the pie tin are for fastening the pie tin to the hot shoe flash. Make sure to cover everything with tape to avoid accidents and so as not to scratch your hot shoe flash. I used a very thick rubber band to hold everything together (logo optional):

Here's what it's supposed to look like:

Nice ring flash effect:

I don't have any post-worthy portrait photos with the DIY Beauty Dish yet, but here is a close-up photo with direct flash:

and with the DIY Beauty Dish. Note the groovy circular highlights in the lens, and the much softer shadows:

I also noticed that on human subjects, at portrait distances, the Beauty Dish produces far more interesting lighting than ceiling bounce, let alone direct flash. It doesn't have the shadows under the chin of ceiling bounce, and it works even when there is no ceiling! (or if the ceiling is too high or too dark).

Wednesday, March 11, 2009

More Cheap Telescope Upgrades

I've replaced the aluminum tripod legs on my cheap Barska with some wooden legs I had from a previous project. I even spray-painted them orange several years ago so they look like Vixen tripod legs.

These are more stable than the aluminum legs (more stable and with better damping, than the collapsed aluminum tripod). As such, the eyepiece is in a convenient position for seated observation even when pointing close to the zenith.

I just used some 1/4"-20 bolts to attach the wooden legs to the EQ hub. The bolts which came with the Barska are too short for the wooden legs.

This is a full-frame (uncropped) image of the full moon. I used a 32mm Vixen Plossl (giving 28X magnification) and the Pentax K10D with 50mm f/2 manual focus lens, afocal projection:

I'll just tweak the leg mounting, find a reticle eyepiece so I can guide through the main tube and take photos of DSO's using a 200mm Super-Multi-Coated Takumar piggybacked to the scope. That way I can do 30-second to 2-minute exposures without a motor.

If results are promising, I'll buy an EQ-1M motor for the thing.

Monday, March 09, 2009

Cheap Equatorial Mount

I've been seeing these Barska 90060 telescopes at True Value over the past couple months. They always sell out really quickly but yesterday Dennis spotted a pair at True Value in Shangri-La Mall. I asked him to reserve one for me, and bought it last night. Cost around $110. This is in contrast to $70 to $100 in the US, however not factoring in the hefty cost of shipping a 20-pound box to the Philippines.

I really was only after the mount (or more specifically, the equatorial head).

I did not have high expectations (these things have 200-arcsecond periodic error, a wobbly aluminum tripod, and a poor-quality telescope). I did not even intend to unpack the telescope, instead I planned to mount my 80mm Vixen refractor on the mount.

A few conclusions are in order:
  • The 100-tooth Right Ascension gear has a significant amount of slop;
  • However the biggest source of inaccuracy is slop in the worm gear caused by an improperly-tightened end bushing. I intend to adjust this when I can get an Allen wrench set.
  • It uses a non-standard dovetail, however the entire EQ head is made of some pot metal so I enlarged the dovetail bolt holes with a screwdriver so I could bolt my tube rings to it.
  • The Celestron/Vixen 80mm f11 is way too heavy for the tiny counterweight.
The view of the moon at 28X (with a 32mm Vixen Plossl) and 90X (with a 10mm) was razor-sharp, with only a tiny hint of CA on the limb. The equatorial mount works as advertised, allowing hassle-free tracking (so long as the tube isn't so unbalanced by the tiny counterweight), even with only an eyeball polar alignment.

Due to the really heavy Vixen OTA, I decided to give the telescope tube (a 60mm f11) which came with the Barska a try.

To my tremendous surprise, the cheap plastic focuser is a 1.25" one, not the usual 0.965" on cheap telescopes. So I was spared the indignity of using the supplied Huygenians and Symmetrical Ramsden (17th-century technology!) eyepieces with the kit.

The view of the moon is decidedly less impressive than with the Vixen (as expected). The cheap plastic focuser doesn't quite reach focus with the 32mm Vixen Plossl, but the 10mm works fine and I could see the Straight Wall quite well near the lunar limb.

The 5x24 finder which comes with the kit has a very small eye relief, tiny field of view, and is pretty useless (I used the hole in the mounting stalk to aim the main telescope tube). Good thing I intend to use a Telrad or Rigel Quick-Finder (I have one of each) with the Vixen tube.

In summary, the Barska 90060 is a piece of crap which should not be purchased by newbie star-gazers, who will gnash their teeth in frustration at the many limitations of this mount and telescope. But it's a relatively cheap entree into equatorial mount land, and with enough tuning up and tooling, I'm confident that I can make it competent enough.