Posts tagged 'Saturn'

Observing Report 27th-28th March 2008 (Webcam gets first light)

Posted by on March 28th 2008 in Observing Reports
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After what seems to be weeks of cloudy sky, last night started reasonably clear, so I nabbed the chance to see what can be done with a webcam attached to the scope.

The webcam of choice is the Philips SPC900NC, which is recommended by every man and his dog because the sensor is a CCD instead of a CMOS, and because it's fairly easy to modify for raw image and/or long-exposure capture (I might get around to modding mine sometime, but for now I'll keep it as is until I get the hang of this imaging malarkey). It's also recommended because it's cheap (currently <£30 from Amazon, even cheaper if you shop around).

It's been removed from the original housing and temporarily rehoused in a cheap plastic box, primarily to allow a T-thread adapter to be fitted in place of the supplied lens. Removing the lens means that the IR-cut capability is removed as well, which has a detrimental effect on image quality, so I'll be sourcing a suitable filter soon. For now, though, it's a case of going with what's available.

The webcam was attached to the Baader Hyperion Zoom eyepiece using a 50mm extension tube to give the required image size on the chip. Setting the BHZ to 12mm gave the best image, but the seeing was absolutely rubbish, nothing was staying in focus and the image was boiling and hopping about all over the field of view.

Still, anything's better than nothing, I needed some practice and some material to work with, so I rattled off a few .avi captures until I'd amassed just over 9,000 frames, then took some dark-frame captures to aid in the stacking process. Shortly afterwards, I had to stop as the skies clouded over again, so I didn't get to look at anything else interesting.

After packing up, I plugged the dark-frame and the best 5% of the .avis into the K3CCDTools stacker and a while later, after much mucking about with settings, parameters, buttons, knobs, dials, gauges and other such software options, it spat out an image not unlike this:

which was crudely Photoshopped (over-exposed, too much gain, many other faults too) to give this:

I'll play about with the acquired .avis later to see if I can drag a better image out of the data.

Observing Report 09th-10th March 2008 (A better Saturn)

Posted by on March 10th 2008 in Observing Reports
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During the early evening the weather was looking grim. Low clouds were scudding in from the West, making mount alignment impossible. After resigning myself to another missed night, I got the kids ready for bed and then went out for a smoke only to find the skies were clear with minimal light-pollution, so I raced back inside, grabbed the gear and got set up sharpish.

After three attempts to get the mount-software to accept a 3-star alignment (it's no fun having a 65ft willow tree in the garden obscuring all the reference stars!) I popped in the new Baader Hyperion eyepiece and had a look at a few old favourites (M3, M44 and M45) and was impressed with the view provided at this magnification. By this time, Saturn was well up in the sky, so I slewed around to have yet another look and there it was, bright and clear, banding visible on the surface and with moons to boot. The seeing wasn't good, thin clouds were forming and the image in the eyepiece was dancing around a fair bit, so I decided to skip the photo-session with the D50.

Taking the camera back indoors, I had a flash of inspiration/stupidity/call it what you will, and I grabbed the Olympus C730-UZ, set up the BH Zoom at 8mm and hooked up the camera in auto-focus video-mode. I set it running just to see what I could get, to download the movie click HERE.

Anyway, more of that later.

Ten minutes later and the sky was totally clouded over, so I put the kit away and set to with the laptop, trying to extract something reasonable from the movie file.

I had installed K3CCDTools3 (the free trial version) earlier that day, and was keen to see what it could do. Annoyingly, it won't accept .mov files, so I had to convert the movie to .avi and then start again. Plugging the .avi into K3CCDTools3 resulted in over 3000 .jpg frames, which I then sorted to drag out the best 20% which were auto-stacked to produce this image:

 

Stacked Saturn Experiment

 

OK, so it's not properly focused (mind you, it's better than the previous shots I took with the D50), but I reckon it's not bad for a rushed first attempt with unsuitable kit and limited Photoshop skills, and good practise for using the cheap webcam that's due for delivery any day now.

Observing Report 15th-16th February 2008 (More of the Moon)

Posted by on February 16th 2008 in Astrostuff, Observing Reports
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Last night I was back out on the yard trying out different astrophotographic methods and a few home-made gadgets for making this scoping business a little easier.

Using the Baader zoom eyepiece for the 3-star alignment routine makes the process a doddle. Centre a calibration star in the finderscope and it's usually visible in the field of view of the Baader when it's set to 24mm. Re-centre it in the eyepiece then zoom in to 8mm and recentre it again. Reset the finderscope again, so the star's centred in both fields of view. Much easier than having to change eyepieces again and again...

After doing the alignment routine I told the handset to slew the scope around to the Moon and then I set the tracking to Lunar Mode. After taking a few shots afocally (D50 with 18-55 lens @ 55mm through 20mm eyepiece) I decided to try some prime-focus shots (D50 body T-mounted directly to the scope) and rattled off a series of shots at various speeds after getting a fairly good focus using the Hartmann Mask. I reduced the diffraction-spikes by fitting a shroud around the open end of the scope to prevent ambient light from hitting the vanes that support the secondary mirror. The shroud, like the Hartmann Mask, is a simple home-made jobbie made out of a bit of closed-cell foam sleeping-mat.

Mars was out of sight behind the house, so next up was Saturn. Again, I got great views through the zoom, the Cassini Division in the rings was well-defined and all five of the main moons stood out well despite the glare of their mother planet. I couldn't take any pics because the camera had iced up and needed taking inside to recover.

I had a look at a few DSOs before packing away and getting the kit (and myself) inside to defrost.

Anyway, here's the best image of the night:

 

D50 on C8-N at prime-focus, 12 frames at 1/1000s, ISO 200, stacked in DSS, not Photoshopped (yet).

 

Next, I need to work on the focusing for imaging stars using the prime-focus setup. Maybe when this cold-snap's over.

If you want the 12 original NEF files, they're in a zipfile HERE.

Observing Report 8th-9th February 2008 (First Saturns)

Posted by on February 11th 2008 in Astrostuff, Observing Reports
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After re-collimating the primary mirror (which, I found, was loose in the mounting cell) I got the scope out again to take advantage of the exceptionally clear skies, and to try out the new Baader 8-24mm zoom eyepiece and various combinations of camera mountings.

After doing the polar-alignment and 3-star alignment routines, I told the handset to slew the scope around to Mars for a quick look before it went out of sight behind the house. With the eyepiece set to 8mm, I could just about make out some faint surface detail, but I couldn't capture it on camera as there was too much ambient light from the surrounding houses, causing excessive diffraction-spiking.

Next was Saturn. I got great views through the zoom, the Cassini Division in the rings was well-defined and all five of the main moons (Enceladus, Dione, Titan, Tethys and Rhea) were visible. I set up the D50 and took a series of afocal shots through the 20mm eyepiece at various camera settings, trying to find a good compromise between exposure time and aperture. Here's a montage of the nine best pre-processing images:

 

D50 with 70-300 lens @ 70mm, f/4.0, 1s, ISO 200, through 20mm ep in C8-N, Feb 09, 2008

 

Focusing is still a little out despite using a home-made Hartmann Mask (made from a bit of grey closed-cell sit-mat), this is mainly due to the low-tech sloppy focuser supplied with the scope. I need to get it shimmed-up to take out some of the axial play.

I had a look at a NGC 3628 (edge-on spiral galaxy in Leo), M45 (The Pleiades), M40 (double-star in Ursa Major) and M44 (The Beehive Cluster, also called the "Praesepe", in Cancer) before packing away before everything got dewed-up.

The new tracking motors worked well, acceptably quiet and fairly accurate, although I've still to go through the Periodic Error Correction routine and I also need to refine the backlash settings. I've a minor cone-error on the scope mounting-plate which I'll correct as soon as I get the time.

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