The New Family Member

I got my Coronado Personal Solar Telescope (PST) from my friend, it's in pretty good shape except the famous PST rust. See below:-



Double stacked with my Solarmax40, some people call this PSM:-


Let's see how it performs, the short extension tube between the black block and the visual back is removed to focus with a DMK, the visual back also host the blocking filter which is 5mm in size.

Since the rust issue is so series, most probably I won't need to keep the further modifications reversible at all.

Venus

Saw Venus from inside my home tonight after coming back from office, attempted to point my C5 to it, failed due to the poor viewing angle with the LXD55; tried to use a smaller scope, my Ranger, still failed for the same reason.

No chance for this time... maybe next time when it's an evening star again.

Really wanted to try out the CaK on Venus.

PST project

After posting WANTED ads in a local forum and astromart, I got several response since I believe my offer is pretty attractive indeed. Anyway, I will get a rusted PST at a good price. I'll do the following towards my project:-

1. Stage one: use the PST as-is, with minimal modifications

- to explore it full potential, use it with my DMK
- double stack it with my SM40
- to use it remotely (since everything is internal, it's safe)

may need to remove part of the focuser tube for focusing.

2. Stage two: heavy modifications

- unscrew the golden tube, don't cut it; unscrew the black focuser part, don't break it
- custom make 1.25" barrel (item 1)
- custom make 1.25" visual back (item 2)
- custom make cell with set screws for my Cheapy-ERF (item 3)

use-case:-

- use with my Borg 45ED II, SM40/BF10, for double stacking as internal module (bandwidth)
- use with my C5, Cheapy-ERF as large aperture at 1A (resolution)
- screw back together as a PST again (portability)
- use with Herschel Wedge + refractor (need to solve focus travel issue)

Stage one deadline will be April 2007, and to start stage two by then.

20070225 CaK First Light

Last night, the heavy rain cleared away all the fog and also gave a clear sky this morning, but I was in the church by that time. When I back home, the sky was all covered, I prayed inside my heart, I really hope to test my new 2nd hand Baader CaK and soon I got some cloud gaps, today, I tried CaK with my Borg 45ED II, my C5, and later also did an IR with my Borg, and then a few H-alpha with my SM40/BF10.

I also made up my mind to hunt for a 2nd hand PST to double stack my SM40/BF10 on the cheap, and to scale up with larger scope with my Cheapy-ERF but that would be a more long term project.

Back to today's observations:-

AR944, C5 + Baader visual film + Baader CaK:-


Borg 45ED II + APM Herschel Wedge + Baader CaK:-


Same as above + 2x Barlows:-


SM40/BF10, Borg 45ED II, full disc:-


Same as above + 2x:-


2x again:-


3x:-


Finally, a failed mosaic, taken from 1605-1610:-



as you can see, a certain frame is darker, since cloud rolled in during its capture, and the missing piece was just next to it. Click for full size.

Stuff used:-



After several hour, here's a sunset, it's not that red normally, since it's not really too low in the sky, but just sink behind the tall buildings:-

DMK and ToUCam Pro compared at f/41 (II)

This time, I tried to set 0 gain and 1/5s for both cameras for comparison, hopefully a better test.

ToUCam Pro:-


DMK:-


Stacked final of 100 raw frames:-

ToUCam Pro:-


DMK:-

Solar webcam test run

After several experiments, finally my solar webcam is ready. It is just a simple webcam modified as a remote solar finder by using a small piece of Baader film. It will be used to guide my remote controlled telescope to locate the solar disc.





The sun is "smaller" due to cloud, I believe.








No more sun but cloud:-

TG-SP II modifications

Yesterday night, I brought out my TG-SP II to recharge the small SLA inside the same box. I took the mount out for inspection, and I found that the RA/DEC slow motion control knobs can be removed easily and they're attached to the shaft like that of a typical focuser.




A sudden thought come to my mind, I wonder if I could add two focuser style motors to it, to replace the original knob for guiding operations?

To make the whole thing even simpler, maybe I could add just a single motor to the DEC part which is not motorized by now? and then to add another circuit to control the existing motor, or to modify the existing hand controller to accept guiding signals?

If that could be done, the TG-SP II will become a dual axis motorized mount, and at the same time, an autoguide-able platform.

I further checked that if I remove the high profile engagement screw of the RA part, it could clear 360 degrees in one direction, and if I remove the motor cover, it could clear in both directions, making it even GOTO capable. Of course, GOTO is not my concern and I think without proper encoders, this kind of open loop GOTO is not worth at all.

Baader CaK

It arrives today, actually, it should be faster if it's not Chinese New Year holidays.

This filter looked rather special, with a casual glance, you will see it's reflecting a lot of light, silvery looking, can be used as a mirror. If you looked at it from different angles, you will see purple color reflection. Looking through it with naked eye will show a very dim image.

It has a 8nm bandpass, centered at 395nm.

I've placed it side by side with a Baader IR-UV blocking filter:-



On turning it upside down, you will notice some difference. The filter glass really occupied the filter cell from both sides. I guess it's really consist of two different filters, I mean two pieces of glasses with dielectric coating and that's why it looked so thick. Maybe that's why Baader called it double stacked?



Sadly, we only got cloud for several days, so here is the first shot. It's taken with my Borg 45ED II, no diagonal is used, it's a stacked image of 16 raw images, each of them having exposure of around 3.5s:-



No more comment until I got chance to put it together with my Herschel Wedge with the sun!

1.25" and 2" eyepieces follow up test

Today, I have conducted a followup test to see the effect on the true field of view for 1.25" and 2" focuser.

Strange is that, my 2" Pentax SMC XL does provide more true field of view than my 20mm Widescan Type III and also my 40mm Plossl in my Tele Vue Ranger which has only a 1.25" focuser.

That said, it's nothing strange that my C5 and my Borg can deliver more field of view with a 2" eyepiece.

I have also done some tests with my Meade prism, chromatic abberation really jumps in together with other distortions and a softer image. It's not to be used for any serious observation.

Family Photograph

The white guy on the left-most is a Takahashi Sky90 Florite doublet with serial number 1006, co-owned with Paul Ng.

Next is a short white guy, which is a Borg 45ED II with NGF-S, no serial number can be found on the lens or the OTA.

Then the fat guy is a Celestron Nexstar 5" OTA, better known as a C5, serial number is 65425.

Finally is my Ranger, serial number 3001485 from Tele Vue.

C5 and 2" eyepiece

Upon knowing that there's a 25mm rear port opening for a C5, I tried to see if a 2" eyepiece can really give wider field of view than a 1.25" one.

I tried a 20mm Widescan Type III which can maximize the field stop of any 1.25" focuser, i.e. around 27mm, and a 40mm Pentax SMC XL which can maximize the field stop of any 2" focuser, i.e. around 46mm.

Experiment shows that the 2" gives far true wider field of view, that means at least a 2" diagonal is not going to be a complete waste, despite it's just 25mm. From my test target, I could see slightly more than 3 squares plus a tiny bit of space with a 1.25" but I could see nearly 5 squares with a 2".

Borg 45ED II and 2" eyepiece

Upon knowing that there's a 37mm light baffle inside the drawtube of my Borg 45ED II, I tried to see if a 2" eyepiece can really give wider field of view than a 1.25" one.

I tried a 20mm Widescan Type III which can maximize the field stop of any 1.25" focuser, i.e. around 27mm, and a 40mm Pentax SMC XL which can maximize the field stop of any 2" focuser, i.e. around 46mm.

Experiment shows that the 2" gives far true wider field of view, that means at least a 2" diagonal is not going to be a complete waste, despite it's just 37mm.

Also, I found that my Widescan cannot reach focus with a 2" diagonal, but a 1.25" diagonal works.

Solar finder webcam

Finally made one successfully, with the sun present during the modification process makes it an easy job:-



A processed image taken by it:-



It's really hard to mount a film evenly on such a small lens, so internal reflection is a problem, but as a "finder", there's no problem at all.

Borg 45ED and Borg 60ED

Previously I found there's a light baffle inside the Borg 45ED II, so I wonder if the same tube would result in vigneting when used with a Borg 60ED given it's bigger aperture.

I disassembled (just unscrew actually) the Borg 45ED II, found the light baffle to have 35mm openning. On simple calculation, it means it should be 72mm from the objective, and I found it matches the distance from the objective to the baffle.

When I plug 60mm aperture and 350mm focal length into the equation, it yields 146mm from the objective, and that probably explain why there's a tube to connect the lens cell and the same drawtube.

There won't be any vigneting when used in the standard configuration, but if one want to remove that middle tube, one is effectively stopping down the aperture.

Now, the problem reduces to focus range. My JMI-S with adapters will cost 80mm minimum, with the back focus of the 60ED of 98-148mm, that means I'll have 18mm to 68mm to spare for diagonal or blocking filter, 1.25" diagonal and blocking filter is going to work, but 2" will be hard.

Sun 20070220

Cloudy again, but still spend some effort to dig out something from impossibility.



Very poor, right? It proves that I'm a die hard solar observer, nothing more and nothing less.

20070217 ultrashort solar

Got several seconds before the sun sinked behind some distant buildings, no time to setup any equipment, but only to hand held my Borg 45ED II with APM Herschel Wedge and 20mm Japanese Widescan Type III. Since it's low in the sky, ND3 or polarizers are not needed.

No sunspot was detected.

Captured a shot using my Z5 without any scope, no filter used:-

Why webcam is better for planets?

I hear many people asked, why a webcam can out perform cooled CCD, DSLR, DC, etc? Their assumption is, other cameras are more expensive, higher quality, with lower noise level than that of a webcam, so they probably should perform better.

So, what's good for a webcam? the single most important advantage is high frame rate, other than that, smaller pixel size could be another one. Okay, let's go into a little bit more detail.

For high resolution imaging, we're dealing with very large focal ratio in terms of f/20 to even f/50, and therefore, we will need relatively long exposure which at the same time means noise. You will say a DC is cleaner than a webcam here, yes, you're right, but it's only right for a single frame only. The most important thing which makes webcam shines is image stacking. By image stacking, we average out the noise, and the noise amount is inversely propotional to the number of frames that we stack. When using a DC, you can do 100-200 frames at most, but with a webcam, you could get 1000 frames rather easily.

Second is the pixel size, for most webcam, you can do f/20 and you can the proper sampling, but with film, we will need f/60 or even more.

High frame rate also helps you to freeze seeing condition, when we got a lot of samples (frames), we could selectively throw away ugly frames and stack only the best of the batch.

Of course, the above is a simplification of the situation but this is about what's the most criticial reasons.

For the above, you can easily see that why those expensive Lumenera and DMK are gaining popularity among serious imagers. They provide even higher frame rate and they can deliver raw frames uncompressed.

New small tracking mounts

With the growing popularity of DSLR and their capability to take long exposure, various astronomical equipment manufacturers are coming out of products which can let even non-astronomers to get into the field of wide field imaging easily without the need to buy heavy equatorial mounts and telescopes.

These small mounts also allow people to take starry night shots during non-astronomy trip, when they travel to darker skies. So, I believe that many people will be interested.

The first one which I'm going to introduce is the Eyebell CD-1, which is available mainly from Japan but is also available from a Hong Kong dealer below:-

Eyebell CD-1

it comes with a Vixen drive, so the quality is not a problem, it's very compact in size and thus you can take it any where. For many DSLR owners, they already have a tripod on hand, adding this small mount will enable them to take wide field shots of the night sky with their camera lenses, nothing more to bring other than this small thing.

Next is from Canada:-

Astrotrack

It looks interesting too, and it can be folded to make it quite compact. It also mentions the possibility to combine with other compact telescope mounts to be used with small telescopes!

I expect more new exciting stuff are coming.

To me, I'll stay with my Takahashi TG-SP II, since it looks more like a real mount, more versatile as well, with Takahashi quality. For absolute portability, the counter weight shaft can be removed, and the DEC body can be replaced by a simple ball head, so it's indeed as portable (if not better) as the options I introduced above.

It's a really good time for wide field astronomy! Things are so compact and portable now, and they're also very affordable.

Celestron C5, C6, C8, C9.25 baffle size

Belows figures are collected from the Internet via Google search, I didn't measure myself and thus the figures might not be accurate, just for further reference:-

C5 - 25mm
C6 - 27mm
C8 - 38mm
C9.25 - 48mm but it's restricted by SCT port size which is ~45mm

So, it's pretty pointless to use 2" visual back with a C5 or C6? However, mechanical advantage with beefier 2" visual back will keep me using one with my C5.

I did this searching originally wanted to give myself a reason to upgrade to a C6, after downgrading from a C8 to a C5, but now, I simply won't.

I shall check by myself to see if my 40mm Pentax SMC XL can deliver more actual field of view than my 20mm Japanese Widescan Type III. If it couldn't my Pentax would be only useful for my tiny Borg 45ED II, but in any case, I won't sell my Pentax since I truely love this eyepiece, very comfortable, extremely high constrast, second to none color fidelity and sharp to edge.

DMK and ToUCam Pro compared at f/41

This is a side by side comparison of the color Philips ToUCam Pro II, and the monochrome TIS DMK 31AF03 with the same scope at f/41 on the same target.

Notice the difference in field of view, image scale, and cleaniness. ToUCam Pro is using USB 1.1 and DMK is using IEEE 1394. DMK has a bigger chip and thus wider field of view, DMK has smaller pixel size and thus larger image scale, DMK is cleaner both because it's monochromatic, uncompressed image, and the capability for longer exposure, also probably cleaner amplication circuit.

Results can be seen below:-

By DMK:-


By ToUCam Pro:-

Worst solar observation ever

Very poor sky, 0.1/10 transparency, no data to assess the seeing condition, 4s exposure at near maximum gain for my DMK revealed some prominence... nothing else.



A shot was taken by my DC when transparency was still "acceptable":-

Collimating my C5 and M41 Located

First task of tonight is to make my elder daughter to sleep. Next, I took out my C5, aimmed it at Sirius, plugged in my DMK to do collimation, I found the seeing pretty bad but my C5 is at least quite collimated indeed.

A video of the out of focus image of Sirius:-



Image shift is there, but not too bad.

Took off the scope, try to locate M41, quite easily done. Push up the Fujinon 75mm to shoot, 548 gain, 4s exposure * 64:-



Next is the Cosmicar 150mm, 570 gain, 8.158s * :-



Unable to locate M46/M47 due to light pollution and poor transparency.

On Image stacking

This is the first article about the new tag "image processing" and I hope you will like them. The first topic is stacking. Today a newbie asked about what's image stacking in an Internet forum, I come up with the following in my mind:-

Image stacking is like when we're in school, when we try to measure something, we did several independent measurements, and then we sum it up and take the average as our final result. You might also want to kick out the highest and the lowest value before taking average.

Intuitive and sound enough, I suppose. I hope that can clear the misconception about stacked image is not scientific, and it's anything worse than a single snapshot. You won't think a single measurement will be more accurate, or closer to the reality, right?

Why stacking?

* The primary reason is to reduce noise, the noise level is inversely proportional to the square root of the number of frames stacked. For examples, with 4 frames stack, the amount of noise will be reduced by half.

* Stacking average out unwanted signal, for example, dust on the CCD. Imagine that the same spot of dust will remain stationary on the CCD, but your target may drift, that means the relative position of the dust on your target image will change over time. By averaging the individual frames, the dust will be effectively removed.

* Seeing will distort your target in a random manner. By stacking a number of randomly distorted frames, you end up with an image which is statistically non-distorted. The effect is most noteable when the number of frames are large and it approaches to the reality as the number of frames are increased.

Why not stacking?

* Targets with highly dynamic nature are not suitable for stacking. To define highly dynamic, it is related to the image scale which we used. For example, if the image scale is so small such that the change is less than one pixel in size, stacking will NOT be shown the final image at all since it is not detectable. So the question is, whether your exposure window is within the detectable limit of change over time

Other points to be noted:

* Stacking can reduce the amount of noise, but it will not increase the amount of signal. Long exposures are required to gather enough signal, in case of insufficient signal, suppressing noise by stacking will not help to deliver more signal

* Stacking cannot replace cooling, but instead, they can be done at the same time

* Single frame is by no means superior to stacking in terms of the capability to reproduce reality, as long as the change of the target is within 1 pixel. Therefore, it will critical to determine the capturing time window and keep it within limit.

More on image processing later.

Venus and Mercury

When I walked back home tonight after work, I mean after I left the mini-bus, I looked at the west, and I could spot a very bright "star" which I know should be Venus, it's truely very bright, and rather high in the sky.

On its lower right, I could also spot Mercury, it's not too low as well.

Too bad that I didn't bring any camera, otherwise, it's sight even in urban center.

Lovely.

Mercury was pretty like a myth to me many years ago, I also thought it's too low in the sky, too close to the sun to be seen... but actually, there's some favorable moments to see it.

It was around 6:55p (HKT).

M45 Located

Funny, since it's urban environment. M45 is the first deep sky object which I discovered by myself independently. Tonight, I re-discover it again with my DMK, using a platform plate plus a 410 head so that I can shoot the zenith indoor.

This setup is optimized from the one last time, the 410 is used instead of the ball head, which is strong and also more flexible.

First shot is by Fujinon 25mm c mount lens at f/1.4, 4.841s (600 gain) * 64 shots:-



Second shot is by Fujinon 75mm c mount lens at f/1.8, 5.761s (540 gain) * 256 shots, this nearly filled up the field of view:-



Too short exposure to reveal anything than stars, I tried to push the exposure to 6s, and it's then all white.

Lunar observation 20070207 (around 5:30am)

Got such a strange observation chance, originally wanted to see if I could get a Saturn or two, but found that it's already too low. Indoor imaging is strange since you got only an hour or two time frame to shoot your target everyday and the time is shifting. Saturn is never well placed inside my home, and I guess it might be out of place with an EQ mount, previously even a Giro mount would have an hard time.

Better try again later at around 1:00a.

The moon, however, is also fun, that's why I did this. Seeing 3/10, low frequency type, transpareny pretty high at 6-7/10, with some cloud passing, not a big issue.

Most images are of rather poor quality, if it's not the last one which is not too bad, I would say it's due to poor collimation, but it's now more like poor seeing:-

Area near Aldebaran?

Nothing, just scan around, with the platform plate plus the ball head, to push the camera as far out as possible.

Cosmicar 8mm f/1.5:-



it's too close to the top wall outside my window and part of it can be seen in the photograph, cropped a bit to make it more evenly illuminated.

20070204 Cloudy day!

Cloudy for whole afternoon, got a gap before it's too late! Just enough to shoot a short clip after basically waiting for the whole afternoon... during the wait, I removed one hard disk from the system, place it inside an external 1394 hard disk box... this is to save a bit energy since it would be only used for backup... cleaned the computer table, etc... ok, back to the topic, the shot:

1639 (HKT):-



Near no prominence today.

20070203 Solar

Alby (my elder daughter) changed her piano class schedule, thus occupied my playing room (which is also her piano room) until quite late, so not much time to shoot today. Did an experiment to use my 52mm 850nm IR pass filter with the Herschel Wedge.

Transparency improved a bit (5/10) but with moving cloud, more contrast today, seeing still sucks (2/10).

1251, IR Pass, Borg 45ED II, APM Herschel Wedge, DMK 31AF03, ND3:-



1258, SM40/BF10, Borg 45ED II, DMK 31AF03, really push up the prominence part:-



1300, same setup as above + 2x barlows, close up of 940/941:-



1303, another close up AR941:-


An alternative approach to capture full disc, taken around 1305:-


1309:-


1311:-


1313, close up of a prominence:-