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Forum: Mini-Challenges, Games, and Photo Stories
09-08-2009, 09:38 AM
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MattGunn:
Nice photo of a seagull. They are soaring birds so can hang in the air when it is breezy. I had a several gulls soaring over my head once and had my 50-200mm kit lens on a K100D. Below is one of the shots. I've seen a red tailed hawk hover motionless, but did not have my camera handy.
I see you are from Wales. My wife and I thoroughly enjoyed visiting Conwy Castle a few years ago. I've been to Caernarfon Castle as well.
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Forum: Pentax DSLR Discussion
11-22-2009, 08:11 AM
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I'm back.
I was away one night on short notice: a friend with a second home and observatory in the Berkshires asked if I'd like to join him for a night under a dark sky. I dropped everything I was doing and drove 80 minutes to join him. I imaged 9 hours (384 RAW Frames, almost filled a 4 GB memory card) with my modified K110D using an old manual Sigma 70-210 mm and CG-4 tripod. I had a slight cold when I started and ended up with frost on the equipment and a worse cold. I'm just now recovering but for me one night at a dark site is worth a couple of nights coughing...
I've been too sick to finish processing, just the first step with Images Plus ran for 8 hours. I did stack one small trial set of 24 frames and it looks promising. Perhaps tonight I can tackle the rest.
Scrolling though the messages:
I think I confused some people. The photo I linked to was at 2000mm f10 but the photo I embedded was 480 mm f6.
Both were unguided. Both were on a well aligned mount.
I've had real flowers hanging from both 4*4 in observatory beams every summer for 9 years and leave the pots up year around. If I leave a beam un-potted I will strike my head within a week or two! In hindsight I could have made the walls 2 inches higher and save many a head injury.
Here is a list of "tracking and guiding" examples to try and solve the confusion:
1. No and No. Camera on a fixed tripod. Can take short exposure Full Moon shots and star trails.
2. Yes and No. Camera on a motorized, equatorial tripod in the field. Can do most low and medium power astrophotography. Must be "polar aligned." This is what I did early in the week, I aligned the CG-4 on Polaris by sighting through a tube. Since my longest focal length was 210 mm and only exposures were 30 seconds I could get away with alignment within perhaps 1 degree.
2. Yes and No. Camera on a motorized, equatorial, permanent pier. This is what I'm doing in my little home observatory with novel wooden pier. My friend spent more on each of his piers than I spent on the whole setup. My Meade LX200 Classic mount (bought used for $600 in 2005), Meade LX3 2000mm f10 optical tube (also bought used as a scope for $900 in 1997), and Stellarvue 480 mm f6 (new $400) all ride on the pier. I have stopped guiding and just rely on the accuracy of the polar alignment for which I use PemPro software to get within 2 arcminutes of the Celestial North Pole. The short (2 minutes or less) exposures of the DSLR make any drift less than the other quirks of the Classic mount.
3. Yes and Yes. Camera mounted on a motorized, equatorial, tripod or pier. Manually guided by a person watching a guide star and correcting for drift. I did this a couple of years with my old LX3 scope. It had Periodic Error of 45 arcminutes that would destroy long film exposures at 200mm if not corrected by guiding.
4. Yes and Yes. Camera mounted on a motorized, equatorial, tripod or pier. Computerized guiding with separate camera on another scope. I tried this using an SBIG and Pentax. The flexure between the two scopes, mirror sag in the SCT, focuser sag in the refractor, and other problems caused more drift than then I had with guiding off! With very sold equipment the pros do this method.
5. Yes and Yes. Camera mounted on a motorized, equatorial, tripod or pier. Computerized guiding with one scope. This can be done with an "off axis" guide camera. This would work well but I don't have or want the equipment needed. Since both cameras are on the same scope most of the problems of item 4 vanish.
6. Yes and Yes. Camera mounted on a motorized, equatorial, tripod or pier. Computerized guiding with one scope using a camera with internal guide chip. To me this is the ultimate, my SBIG has both an imaging sensor and guide sensor side by side. There can be no differential error between the two sensors. Scope errors like mirror shfit are corrected by the guide sensor. I did this for seven years. I got tired of the small sensor (0.4 MP) and the difficulty of doing color. I bought my first DSLRs (K100D for daytime, K110D for astronomy).
I think I covered all the combinations of Tracking and guiding!
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Forum: Pentax DSLR Discussion
09-28-2011, 05:35 PM
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As someone who took many hundreds of 2 minute astrophotos with a K110D rest assured I did not hold the button all that time. :p
At first I used the Pentax cable release, a bit pricey at $44. Simply a two step switch with a locking position. Then I switched to various timers that plugged into the Pentax. These allowed multiple images with a delay between them.
Be glad our older models have a jack for external shutter switch, some newer Pentaxs do not.
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