Wednesday, February 25, 2009

Comet C/2007 N3 (Lulin)

Today evening Espoo skies were not clear enough for photography, a layer of hazy clouds were on sky. I took a look at Lulin, with 15*70 binoculars. It was visible as a dim and fuzzy spot. Tomorrow I will check sky conditions again.

Comet is currently located at Leo -constellation. Comet brightness will decrease within next few weeks. Best information of this comet is on Seiichi Yoshida's pages.

Friday, February 13, 2009

Nikon D200 problems, part 2

Today I picked up my D200 camera from the service. It was a positive surprise to me... It has been repaired for free of charge.

Mirror mechanics had been replaced and adjusted. Also cleaning and camera final testing was included. Firmware was updated to version 2.00. When I looked the info leaflet, more was about to come... Also there was following items replaced, and again free of charge (!)

-grip rubber unit
-I/F side rubber unit
-bottom cover rubber unit
-front body unit
-rear rubber unit

During repairing, I told also to find out total shutter count. It was 3926 images, since I bought camera at 03/2006. Not very much... I should start using my camera more often.

Thanks goes to Nikon and JAS Tekniikka for a good service !

Sunday, February 8, 2009

Venus imaging

On second of February 2009 I had my C8 OTA collimated and ready for planet imaging. Venus was already too low on the sky, but I still was able to take an acceptable image. Below is one captured frame from video, showing clearly disturbances in the image.
Below is result of 219 stacked frames. Next time I need to do imaging, when Venus is higher on the sky. Focusing must be done more carefully, Bahtinov mask could help...
Additional information:
Date: 2.2.2009
Time: 20:17 (GMT+2)
Location: Karakallio, Espoo, Finland
Telescope: Celestron C8
Web camera: Philips SPC 900NC
Barlow: TeleVue 3x

Friday, February 6, 2009

Collimating C8 OTA

Couple of weeks ago I finished collimating my C8. I used previously built artificial fibre star and SPC900NC camera. I did collimation in the "basement premises", along the 25m long hallway. I also judged collimation with short focal length eyepiece. From my earlier planet images, I saw that the collimation was "way out" a lot... This causes loss of image details, and blurry edges to planets (like Mars).

I got a better collimation by ajusting one screw, approximately 1/5 turns. Images are taken without any barlow lens. Focus patterns - before collimation:
Focus patterns - after collimation:
In / out focus pattern is now much more symmetric and focused star appears without "comets tail" effect. When there is any need to tweak collimation, that is better to do "in the field"....

I also decided to make a test, is it possible to capture airy disk & diffraction rings. I got some... TeleVue 3x barlow was used. Image is stacked and resized to 400% of original size. Airy disk became visible, and first diffraction ring (although not uniformly). On some parts, there are traces of second diffraction ring (?) visible. The large faint disk around star, that I do not where it came from. If anyone knows, leave comments...
Two videos I also took of artificial star. Fist one with precise focusing (1) and second about disturbances in the video (2), caused by air movements.

Wednesday, February 4, 2009

Building artificial star

My C8 OTA needs a collimation process to be completed. I have seen some artificial stars usually made my pinching a small hole to a very thin metal foil.

I wanted to build a "prototype" of a artificial star, which had very small hole for light rays. I had some pieces of broken single mode fibre, which should be fine.

Both ends had a exposed connector (SC type if I correctly remember). Cable type designation was 10/125 - which means very thin core of optic cable. I put my small Maglite into other end of cable. With the beamwidth, I could adjust brightness of a artificial star.

I did not put all the things in enclosure. If have some extra time, maybe then...