Wednesday, October 31, 2007

A dream camera

I didn't go for a DSLR yet both because of the fact that I'm lacking of time to use it, and also because of the lack of a really great camera in the market.

Live preview is getting more popular in the market, and I believe it's really useful for astrophotography, it really saves a lot of effort, making a DSLR even more standalone. Right now people depends on a notebook PC with suitable software to really focus a DSLR, however, with Live preview, things should become much easier.

Frankly, what makes a DSLR a SLR is the traditional through the lens view finder, however, it's not necessary and I would better say, it's useless for astrophotography especially with Live preview. So, all we need is a big sensor like APS-C or bigger, and an inter-changeable lens system so that we can connect to our telescope's prime focus.

Having said that, such a camera will become more like a regular DC with a bigger CCD/CMOS and an inter-changeable lens. It will probably allow you to record video clip as well. ;-)

Such an animal should be more compact than existing DSLR, but yet at least as powerful as a DSLR, and far more suitable for astrophotography.

To be more realistic, so far Canon 40D is the best one available from the market.

Tuesday, October 30, 2007

More thoughts on Canon 10x30 IS

Have been using it for a couple of days, I nearly get a view or two through it every day, despite the sky was cloudy sometimes.

1. I tried to look at high contrast objects against the white sky background, chromatic abberation is like my Pentax PCF III 10x50, maybe slightly less. For all other less demanding targets like the moon, chromatic abberation is minimal, better than my trusty Pentax.

2. Brightnes test: I really want to try to see when the 50mm aperture of the Pentax will help, but so far I failed. Maybe it's due to the fact that I didn't compare them at really dark places, in brighter places, our pupil never dilates to more than 3mm maybe, and that's why the bigger exit pupil of the Pentax does not help much. Believe it or not, I even get out a ruler to measure if the Canon is really 30mm!!! It's simply too bright to be 30mm actually.

3. Stabilizer test: I begin to enjoy the feeling to press that button, it feels like pressing the shutter of a camera, of course, it won't record an image, but the stabilization effect is simply superb! You immediately see more detail with it engaged. This button even helps when I support my elbow while looking, I suppose it's otherwise pretty stable, but that button still helps!

4. Stars: I didn't get a lot of chance to look at stars with it, but from the limited chances, I found that it really helps to dig out stars otherwise washed out by the air and light pollution from Hong Kong. No bad indeed.

6. Field of view: the added 10 degrees of apparent field of view is truely a nice place, it gives a stronger sense of being out there rather than looking through a telescope. It definitely helps to frame targets, and it's still not too wide that you need to roll your eye balls around.

7. Eye-relief: the eye relief is truely comfortable, without eye-glasses, I can see the whole field of view with the rubber eye cup, still have a little bit room to spare to avoid foggy the eyepieces. At the same time, when the eye cup is retrated, I can also see the whole field rather comfortably with my eye-glasses. Some occassional back out will be detected, but it's minor and not annoying at least for experienced telescope users.

More later.

Sunday, October 28, 2007

20071028 Sun

The big prominence yesterday is gone, but we still got another smaller one, since it's pretty small in size, I used my C5/PST based setup to capture it, at 1250mm focal length and f/10, I already need to use 1/15s and medium gain to capture, it's faint as well. Full disc shots were also captured to record down its relative size to the solar disc.

First is a tiny quiet region filament (QRF), taken with C5 at prime focus, histogram highly scratched to show the detail, 1449 (GMT+8):-

A random patch on the sun, 1453 (GMT+8):-

Full disc prominence shot at 1529 (GMT+8), plus two higher image scale shots at 1443 and 1458 (GMT+8):-

Full disc surface detail at 1530, Borg 45ED II at prime focus, we probably can't find that tiny QRF in the first shot, can you? Oh sorry, I can't.

Transparency is 2/10, seeing is something like 1-2/10. It was cloudy at first, but after some wait, I got the sun through otherwise very misty sky, probably no luck to watch the comet again tonight due to the bad transparency.

Also did an experiment to use a Herschel Wedge as a ERF, with PST etalon and PST-BF5, also a red filter, a IR-UV block to see if it's a working configuration, good news is that, some surface detail does show up! It's a very scalable setup since the Herschel Wedge can be used in virtually refractors of any size! Let's see.

Saturday, October 27, 2007

Effect on Image Stabilizer of Canon 10x30 IS

In short, I used to find my hands pretty steady, since I can hand held a pair of 10x50 or even 10x70 without major issue. I can hold them quite long, and I found the view quite steady, at least the vibration will not be annoying, I can resolve pretty much detail from the targets which I observe.

However, when I press the button my the Canon 10x30 IS, wow... I know my hand is quite shaky, the vibration is not very bad, but it definitely washes out some small detail. When the IS button is engaged, I can resolve some more detail from the view, and the small vibrations are all gone!

At the first few usages, I found after pressing the IS button, the view becomes a bit strange in a sense that you can feel like floating on the sea, I even got a bit sea-sick after several minutes of usage. However, such feeling goes away soon after just one day. I get used to that feeling.

Like most people comment on the IS button, yes, we will need to hold the button down to enable the IS function, however, it's so easy to hold it, you don't feel tired even if you use it continuously. So, it's not an issue indeed.

20071027 Sun

Seeing is 3-4/10, transparency is 3-4/10. Borg 45ED II, SM40/BF10/DMK31AF03.

Full disc, Borg 45ED II at prime focus, 1302 (GMT+8):-

1304, same as above, but focused on prominences, 1304 (GMT+8):-

1308, higher magnifications with the prominence around 1.5x, 1308 (GMT+8):-

A failed mosaic, consisting of 4 frames, taken from 1310-1312 (GMT+8), around 3x:-

Three shots on the same prominence, around 3x:-

Friday, October 26, 2007

Comet 17P/Holmes

It's a real surprise when people report that it brightens suddenly and it's available whole night long. So, I shall catch it by all means :-)

Originally, I planned to bring my DBK/DMK to capture some shots with my c mount lenses, however, I gave up finally with the worriness about security issue. The areas around my home is pretty quiet, and security is really a concern. Therefore, I only brought my newly arrived (this afternoon!) Canon 10x30 IS with me, together with a self printed finder chart.

Actually, I expect that it's a very easy find, for it's very close Mirphak (Alpha Perseus), so with the wide field of view of the Canon (6 degrees), it's a very easy job. Even in urban area of Hong Kong, with Capella around, the nearly full moon, it should be really easy.

I choose a small playground from my home, I thought it will be very quiet, but instead, there's still a little kid playing with her father, a couple, plus some security guards around chatting with cleaning staff. It's a very nice and secure place indeed.

I choose to lay down on the slide (the kid is not playing), the moon is my first target, it's to test the CA of the Canon and also the function of the Image Stabilizer. I'm very satisfied with both, zero complain.

Next, I tried to locate Mirphak with my eyes, sorry, no luck. Next is Alpha Aries (Hamal), yes, it's barely visible. Strange, I think Mirphak is easier since it's farther away from the moon. Maybe due to thin cloud/mist?

I also tried to locate Capella.... it's visible on and off, never very certain with naked eyes. Anyway, I scan around in the expected sky patch with the Canon... two bright stars are located very easily, and then... I saw a yellowish dot of light, it's as bright as that two stars, if not brighter, and on pressing the IS button, wow... I saw it's not a dot of light, it's definitely non-stellar! It's that comet for sure!

I'm very happy, since it's the first time which I really see a comet! It's not big at 10x, but it's definitely big enough to be detected as a small disc!

I think if we have to shoot it, we either need longer focal length (like my C5) or to be at a darker place. Let's see if we have chance soon.

Canon 10x30 IS

I got mine eventually.

It's very nice, in terms of size and weight, it's pretty close to my Pentax 10x50 PCF III, but if you take IS (image stablization) into account, it's way lighter, since no tripod is required now.

It comes with only eyepiece caps, no objective lens cap. The bag that comes with it is pretty nice.

I just tested it indoor, it reaches focus rather easily, a good sign for bird watching. It's made in Japan. The apparent field of view is large at 60 degree, which is bigger than my Pentax despite they're both rated as 10x.

I shall report back after some actual usage.

Tuesday, October 23, 2007


Hong Kong sky were too bad for this.

What I've done was to point my DMK 31AF03 with a Computar 2.3-6mm at 2.3mm outside the window, keep recording for the whole night.

A night worth of AVI will be something like 2G.

No luck, however.

The bright patch is the moon, and the irregular shape is due to the diffraction pattern of the aperture adjustment diaphram.

Sunday, October 21, 2007

Testing two C/CS mount lens

DMK 31AF03 (1/3" CCD), Computar CS 2.3mm - 6mm f/1.2 at 2.3mm, it gives some fish eye effect which is very nice for ultra-wide field, unluckily, we got only one brighter star here, the circular bright patch is the moon:-

The same camera with a 75mm f/1.8 Fujinon C mount lens, quite sharp indeed, the halo is caused by poor sky, I believe:-

20071021 Sun

Transparency is 3/10, seeing is 3-4/10.

3*2 solar mosaic, Borg 45ED II, SM40/BF10, 2x barlows, DMK 31AF03, more overlapping is required to have better boundaries between raw frames, taken from 1519-1522 (GMT+8), click for full size:-

Closeup by Cheapy ERF, C5/PST/BF10/2x, they're good demonstration only to show the dust on my CCD:-

Impulse buying?

After reading the binoculars article in S&T, I was tempted to get a pair of Canon 10x30 IS for myself.

I've been on ebay looking for a deal, after several attempts, I finally won one of them, just paid, see how's it perform.

Is it impulse buying? I'd say it's probably yes, since yesterday morning after I reviewed my maximum bid, I kept on dreaming that someone will place a higher bid so that I don't have to buy finally. But then, this morning, I know that I won.

Anyway, now it's just to wait for it, to test it and to enjoy!

Saturday, October 20, 2007

20071020 Venus? No, it's Jupiter!

I saw a bright "star" from my window (SW facing) and thought that it's Venus, but since I've to go out by then, I failed to take any shot. Tonight, I saw it again but it's much dimmer, due to the low transparency. Anyway, I setup my C5 and point at it. To my surprise, it's Jupiter!!!!

C5, 2x barlows, DMK31AF03. Transparency 2/10, seeing 0-1/10.

1830 (GMT+8):-

Camera rotated, 1832 (GMT+8):-

20071020 Sun

The sun continue to silent, transparency dropped to 2/10, seeing 2/10. Borg 45ED II, SM40/BF10 for the first shot, PST etalon added forthe second, and finally Cheapy ERF C5 PST etalon for the last shot.

1310 (GMT+8), SM40/BF10:-

1315 (GMT+8), SM40/PST/BF10:-

1325 (GMT+8), Cheapy ERF/C5/BF10:-

I found that even in the Borg setup, internal reflection of the PST etalon is washing out of the contrast, anyway, when you want large aperture, and yet cheap, you will have to live with some problem. Anyway, I'll still try to find solution for it. BTW, I found the objective of the PST has a concave surface on the side facing the etalon, maybe it's the key to stay away from the internal reflection?

Infrared eye

The title is a little bit confusing :-)

Actually, I feel a little bit boring while doing my revision, so took my new Cosmicar 6mm f/1.2 lens out with it's IR pass filter to play, this is my eye in infra-red light.

I guess it would be funny to point it to some brighter deep sky objects, to see whether we have IR signal there.

Friday, October 19, 2007

20071019 Quiet Sun? No!

It's Chung Yeung Festival today, and we got a holiday today. Chung Yeung in Chinese is called double nine, or double Sun. The Sun has been quiet for a couple of days (weeks?), there is little or no active region, little prominences and lack of filaments. Transparency is 4/10, seeing is 2/10.

The first two shots are obtained by SM40/BF10 with my Ranger, DMK31AF03 at prime focus, they're stitched as a mosaic below:-

Then I pulled out my C5 based setup, consisting of a Cheapy-ERF plus the PST etalon, BF10 to shoot, first is a prominence and then next is the surface detail of the same location:-

Finally, another quiet corner of the sun... oh no! it's not quiet at all! I told myself, there's no quiet sun, and there's only insufficient aperture or too wide bandwidth:-

Okay, switch to CaK to get some idea of the sun in another wavelength. Borg 45ED II, APM Herschel Wedge, Baader CaK, DMK31AF03:-

Tuesday, October 16, 2007

20071016 Sun

I caught a flu, slept until 11:30a and visited the doctor, had a quick lunch and also a quick observation of the sun during cloud break.

1419 (GMT+8):-

1420 (GMT+8):-

Full of cloud, no real cloud free gap, but the cloud got averaged out during stacking only.

Friday, October 12, 2007

PST further disassembled

Finally, I've removed the objective lens from the PST lens cell by removing the retaining ring. It's a very thick cemented doublet. Maybe I will want to buy a similar doublet to replace it myself, of course, since there's no ITF in a regular lens, I will need to install an ERF in the front as a replacement. It will not be very safe, but at least it will work for imaging.

I've also checked that the prism inside has a special coating, images through it will become red in color, so it's some form of filter as well. This prism is the one inside the black block, both for focusing and as a prism diagonal.

Tuesday, October 09, 2007

Followup experiments with PST etalon

It was found that the PST etalon will work at f/7.22 but not at f/6.86, and previously, another sample was found to work at f/7.14 as well.

Followup experiment should be conducted to add a barlows in front of the PST etalon to see if it will make it work with the Ranger.

Corrently possibilities are Tele Vue 2x and 3x barlows, as well as a 2.5x binoviewer corrector which should work at around 1.29x and 1.51x without and with extension tube respectivity. That would mean f/8.85 and f/10.35 respectively. There should be better than using the 2x and 3x barlows.

If it ever works, it will be the most elegant way to upsize, instead of going for a Cheapy-ERF with my C5, tilting will be a bit easier to do with a smaller ERF.

Sunday, October 07, 2007

20071007 Sun

Seeing was 3-4/10, transparency like 1-2/10, AR972 still there. Low transparency is washing out contrast, only 1/4 of the whole histogram contains signal. The close up is taken by 3x.

1401 (GMT+8), prominence only:-

1405 (GMT+8), monochrome and color versions:-

1413 (GMT+8), close up of AR972:-

Experiment was also conducted with 52mm red filter as ERF with PST etalon and it works, unlike the Ranger. The Borg 45ED II is f/7.2 while the Ranger is f/6.86, that's about the critical focal ratio for the PST etalon to work.

Saturday, October 06, 2007

20071006 Sun

Borg 45ED II, SM40/BF10/PST etalon, DMK 31AF03 at prime focus. Seeing was 3/10, transparency was 2/10. We have AR972 here, nothing else.



1307, re-tune the SM40 Tmax and PST etalon, more even disc:-

More contrasty than SM40 alone definitely.

1307 reprocessed:-

Friday, October 05, 2007

Testing Computar 2.3-6mm f/1.2

No star for testing, so just take a shot with terrestial targets. The color shot is obtained by my DBK 21AF04.AS which has a 1/4" color CCD, zero gain is used at 2s each, the black white shot is acquired by my DMK 31AF03.AS which has a 1/3" monochromatic CCD, zero gain is used at 1s each. Seems like the monochromatic chip has twice the sensitivity of the color chip. Both at f/1.2, i.e. wide open.

With a large chip, the monochromatic one covers more area. No UV/IR block is used.

Thursday, October 04, 2007

Cosmicar 6mm f/1.2

This lens arrived just two days later than the 2.3-6mm Computar zoom.

This is the best bargain ever! It's very new, I'd say, if it comes in a box, I would say it's a new lens! It comes with both lens cap, the lenses are in excellent condition, the coating is very nice, the focus and the aperture rings are all very nice and they give a firm feel.

It even comes with a IR pass filter, again in excellent condition, the filter is B+W from Germany, 40mm thread as measured roughly by a cheap ruler.

All for $6.5 USD only, even shipped! That's probably why I also got this one despite the Computar zoom can reach 6mm, too.

Tuesday, October 02, 2007

Computar 2.3-6mm f/1.2

Received today, it's very compact and light weight.

Just plugged it into my DBK 21AF04, the field of view is really fast. Focus adjustment is not very good, but it works. Zooming can be done similarly.

There's a lock screw for focal length and focus, a nice touch.

At the widest setting, barrel distortion is quite apparently but it's expected for such a wide field of view at 2.3mm only! It should be nice as a finder lens, and for capturing milkway shots.

The next lens will be a Cosmicar 6mm f/1.2 prime lens which should be free of distortion, but it's not as wide as well. Should be good for more serious work.

Really want to try it out under stars.


I also tried it in my DMK 31AF03 on the next day, the field of view is even wider, and it gives slight fisheye view which is lovely, too!