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.

SC OTA for planets, thoughts

Since the weather doesn't allow planet photography, I have plenty of time to consider what I need to invest in the near future to my C8 package:

• Dew shield

Needed especially in cold winter nights. Normally the corrector lens will suffer from frost formation, just when the imaging session is ongoing... Flexible model would be more convenient, since my setup needs to be portable.

• Magnifying finder

There was only a red dot finder (RDF) include in C8 (without base..., that was promised to be separately sent to me). Brightest planets will be visible through an RDF, but it may be a bit struggling to get planet directly in the field of small webcam sensor. This remains to be seen with the actual use of scope.

• Heater strips

Combined with dewshield, heater strips will be another (and propably the best) solution to battle against corrector lens frost. If/when I get more seriously interested about visual use of my scope, I may need to buy heater strip for eyepieces also.

SC OTA for planets, scope arrived

The C8 XLT scope arrived, at 30th November 2007. I wasn't home, when first delivery was attempted by UPS, so scope had to picked up at local UPS storage premises. This is how my planet imaging setup looks like:

System consists of Celestron C8 XLT Schmidt-Cassegrain scope (2032mm, f/10), mounted on Skywatcher HEQ-5. There is enough of focal length in C8 to be used for planet imaging. In case I later on get interested in DS photography, this tube will come in handy with some focal reducer - like 0.5x -model from Optec.

I have bought a separate Grayford focuser from William Optics. This way you can get a smoother focusing, and also both 1.25" and 2" accessory connections. Focuser also rotates around it's axis, to allow suitable composition in the image.

3X barlox is from Televue, quality and build looks and feels very convincing. Barlow lens felt solid, and a bit heavy when I first took it in my hand. I believe it will be worth of invesment. Reflections in the lens surfaces were very deep green, so I assume lens coatings are typical (and good) Televue value.

AVI sequence of the planets will be captured with Philips web camera. SPC900NC was available at the time. Oririginal lens was removed from camera and 1.25" adapter was screwed into lens thread. I also use a Baader UV/IR cut filter in front of the sensor, to ensure better image quality.

All I need now is some freetime and clear skies with good seeing. Currently it does not look too promising... Sleet is pouring down from the sky.

SC OTA for planets, order status

Order process is ongoing, but not so fluently as I expected. All the needed parts arrived to dealer. That had been informed to me already, my e-mail safety rules had blocked this mail. Payment is now done. Currently I am waiting for the dealer in Germany to inform me, when payment is received at their side. I was told that I will receive UPS tracking number, when shipment is done. I would estimate that scope arrives somewhere on the end of next week, hopefully...

SC OTA for planets, order placed

Today I have placed an order of SC OTA, to be used for planet photography mainly. I would expect, that there is good package for many years to come:

Celestron C8 OTA with XLT coatings
William Optics SC Grayford focuser
TeleVue 3x barlow (1.25" size)

Now I have couple of weeks and endless hours of waiting the package to arrive. Just like a small child waiting for the Santa Claus to visit :-)