Sunday, April 29, 2007

Reassembling the PST

I put the PST-BF5 back to the visual back, screw the etalon module in again, for what purpose?

Actually, I've rotated the PST etalon module, just to test its range, however, I found my action probably knock it out of optimal, so I screwed it back tonight, when the sky clears again, I shall check it's optimal position, keep it there and re-assemble the tuning ring back for further use.

Saturday, April 28, 2007

20070428 Solar

Alby's new piano is here, things are all relocated, got a break to shoot.

SM40/BF10, Borg 45ED II, DMK 31AF03, platform plate used, 2x barlows (closeup), 2.5x corrector with extension tube (mosaic), poor seeing (2/10) and transparency (2/10):

1416, full disc shot:-

1417, full disc shot, colorized:-

1420, close up of AR953 (2x barlows):-

1421, close up of AR953, colorized (2x barlows):-

3 frames failed mosaic, from 1423-1426, 2.5x corrector with extension tube:-

I packed up my stuff 1430 HKT due to the cloud, but then the sky cleared up again at around 1530, transparency is now around 6/10, seeing is 2-3/10, I did some CaK, white light and IR, with APM Herschel Wedge, Baader CaK and a generic 52mm IR pass filter:

1538, Borg 45ED II, APM Herschel Wedge, Baader CaK, full disc:-

1540, Tele Vue 2x barlows added:-

1542, removed the CaK and installed the ND3, white light:-

1543, added a IR Pass in the front, infrared:-

1552, close up of AR953 again, it changes rather rapidly:-

1556, close up of a prominence, SM40/BF10, 2x:-

Finally, this is how I take the above images:-

Thursday, April 26, 2007

20070426 Lunar Observation

We have some non-cloudy sky, I mean it's not fully covered with cloud, but still it's covered with a not-so-thin layer of mist. Seeing is 2-3/10, transparency is something like 3/10.

Borg 45ED II is used, 3x barlows is used for close up, DMK 31AF03, all on a Bogen 410 head on top of a long mounting plate, on a LXD55, to extend the view outside my home window.

2223 (HKT), prime focus, full disc shot:-

2228 (HKT), 3x barlows:-

2231 (HKT), 3x barlows:-

2237 (HKT), 3x barlows, transparency was worsen during this one, noise increases and some parts are cropped for this reason:-

Not bad for a sky-hungry guy, not exactly a good night, but it's fun enough to play with this small gun.

Wednesday, April 25, 2007

Blocking filter size

The size of the blocking filter imposes something like a field stop in your eyepiece, and therefore, the field of view is limited by it rather than the one inside your eyepiece, and it's always the limiting factor for any eyepiece with field stop larger than your blocking filter size.

For example, with a BF5, any eyepiece with more than 5mm field stop will yield the same true field of view, regardless of the focal length of the eyepiece.

Normally, we switch to lower power for wider field of view, but in this case, switching to lower power might not usually give wider field of view. It will only show a smaller solar disc. Of course, the image brightness will be affected, if you have smaller aperture front filter (the etalon), you will not like to go too high power (short focal length) even if the field of view is the same, for you are not limited by the exit pupil size (image brightness).

Sunday, April 22, 2007

A good home for PST BF5

I bought a PST just to dig out the PST etalon module, but then how should I use the rest of the system? Wouldn't it a big waste if I simply throw the rest away?

I've disassembled the PST BF5 which also forms the visual back of the PST, I've removed the blocking filter inside this visual back, it's basically two pieces of glasses cemented together:-

The red side is facing the eyepiece, feels like a H-alpha narrow band filter.

The gold side is facing the objective end, it has very high reflectivity.

Given it's very small size, I wonder where shall I put it? With a blink of mind, I think of my 7x25 monocular which was used as a white light scope to see if there's any sunspot before I setup a bigger scope for imaging, so I disassemble it as well:-

I've placed the PST-BF5 in the field stop of the eyepiece part, however, it couldn't cover it all since it's very small. Then I also picked the circular field stop inside the PST visual back to put it as the field stop again for this scope:-

So, finally, I've a 7x25 which has a PST-BF5 installed. If a SM40 is placed in front of it, it's basically a very small H-alpha telescope! I plan to use it for afocal imaging with my DC, since it's so small, even a tripod is not required and I can use it for snapshot type of H-alpha imaging.

I shall conduct some experiments to see if the PST etalon can be used as a front filter, if it can, it will be even more portable. At the same time, since the PST etalon has no central obstruction to block the already small 25mm aperture, it will actually be more suitable than the SM40.

Saturday, April 21, 2007

Cloudy exercise

It is cloudy again when it's saturday and sunday, let's don't give up until the last minutes, to see if we can have some chance to shoot.

The below were calculated based on my DMK 31AF03 and Borg 45ED II, it's nice to find that with a 2x barlows, full disc solar shot can be covered by 2*2 mosaic indeed with reasonable overlapping, when there's chance, I shall try it out! mosaic is the best way to get even illumination for H-alpha solar imaging.

1/3" CCD
CCD pixel 4.65 4.65
CCD resolution 1024 768
CCD size 4761.6 3571.2
Pixel area 21.6225

target size 33 33

Aperture 40 40
f 325 325
f * 2 650 650
f * 3 975 975

FoV 50.37 37.78
FoV * 2 25.19 18.89
FoV * 3 16.79 12.59

Sampling 2.95 2.95
Sampling * 2 1.48 1.48
Sampling * 3 0.98 0.98

Target resolution 670.81 670.81
Target resolution * 2 1,341.61 1,341.61
Target resolution * 3 2,012.42 2,012.42

mosaic 0.66 0.87
mosaic * 2 1.31 1.75
mosaic * 3 1.97 2.62

daws limit 2.9 2.9

Friday, April 20, 2007

An ultra-portable H-alpha setup

Borg 45ED II with SM40/BF10 is very portable indeed, however, since it requires a tripod, it could be a bit hard for everyday usage.

For everyday usage with it, the only exception is probably to use it remotely, but at the time being, I still find it hard to find a suitable place to host my remote controllable setup.

On doing the PST etalon module transplanting, I am thinking if there's a better way. I think of the Pencil Borg which is a 25mm telescope, possible configurations are:-

1. Use a red filter as a small ERF on the aperture, the the PST etalon and BF10 at the back, then do afocal coupling with an eyepiece and my DC.

2. Use a red filter in front of the the PST etalon module, place them on the aperture of the Pencil Borg, and then use the BF10 at the end of the Pencil Borg, again, do afocal coupling with an eyepiece and my DC.

Which setup depends on the focus travel. The first setup might not be do-able however, it does not require any separate adapter, and the whole 25mm aperture of the Pencil Borg can be used. The second setup will not have any focus travel issue, however, the Pencil Borg will be stopped down by the PST etalon module, and also I might have to remove the built-in lens from the PST etalon before use, and new adapters have to be made.

If the PST-BF5 can be used, it would be even better since it allows straight through setup, which would be easier for aimming.

Sounds too good to be true, everyday snapshots style solar imaging!


An H-alpha dream: last night I dreamed of a very active sun, I saw a giant prominence of around the size of the solar disc itself, however, later it's blocked by something inside my home, I remove it angrily and later found that the prominence was gone. I woke up in big anger...

This is probably my first observation log from my dream, actually, I did dream of astronomy observation before, but didn't have good record of them.

Thursday, April 19, 2007

Thin Moon (20070419)

On the way back home, I saw a very thin slice of moon hanging over in the sky, it's quite a rare sight here in Hong Kong these years, for the air pollution is very serious, and thus making this kind of moon hard to see.

I managed to catch a few shots when it's still away from a close-by building:-

Taken by my Konica Minolta Z5, at full zoom, click for full size.

BTW, on the way back home, I saw a woman holding a DSLR to shoot the scene, but her lens is probably too short. Actually, the Venus is quite close, too.

Tuesday, April 17, 2007

Borg 125ED

Recently, I was thinking if I should acquire a Borg 125ED to replace my C5.

The logic behind is that, it gives equivalent aperture without central obstruction, it could be used with a Herschel Wedge, and also can be used more effectively for H-alpha imaging with PST etalon module.

However, with a recent discussion in cloudynights, I was reminded that the decision is really on the mount. The C5 can be mounted on the TG-SP II very peacefully, but the Borg is probably too long even if it's not too heavy. So, the Borg 125ED can never replace the C5, a C6 could be.

For this factor, I suppose I will stop looking for a Borg 125ED, for it is not really a good fit. A Borg 101ED could be, however. But in that case, it might not be able to completely replace a C5. And still, my TG-SP II would be a bit hard to handle a Borg 101ED, too.

Time to re-think.

Sunday, April 15, 2007

20070415 Solar

The sun remains very inactive. Cloud move in and out, seeing bad as well.

CaK revealed nothing basically, Borg 45ED II, APM Herschel Wedge, Baader CaK, 1608 (HKT):-

H-alpha does not show up anything interesting too, some small filaments, plus two set of prominence, not big either.

SM40/BF10/Borg 45ED II, 2x barlows:-

1621, closeup:-

1625, closeup of a prominence:-

1626, exposure optimized for surface detail, but prominence can be digged out too, not the best:-

1627, down under the above shot, some nice surface detail can be found, too:-


Did an experiment, it is to use the PST-BF5 to replace the BF10, however, due to the fact that I'm hand holding it, collimation problem leaves some double image, not a good test at all.

Saturday, April 14, 2007

Heart of PST transmission

I put the PST etalon module and the PST BF5 together, I found the transmission was quite high, by high, I mean I can see terrestial targets through this combination.

Sounds like the ERF of this older version is in the objective.

The high transmission could probably mean it's even more suitable to be used with a Herschel Wedge, let's see.

Wednesday, April 11, 2007

Sidewalk astronomy, public outreach

6th of April

We did some deep sky observations in road side, some local people came too. Introduction to constellations, bright stars, etc. Borg 45ED is used on a weak tripod, but that's the only viable way for me when going with two children.

8th of April

I brought along my SM40/BF10/Borg with a very light weight tripod with me during the trip to the northern part of China. When we did some exchange activities with the local schools, I showed the students the sun in H-alpha!

Solar activities were pretty low, but I saw some students are impressed.

At the same night, we went to have some night time observation, too.

Sunday, April 01, 2007

20070401 Solar Observation

Cloud also came and went, in the best case, we still have some cloud, exposure time was ~1/180s which indicates poor transparency, something like 1-2/10. Seeing was bad, too.

1532 (H-alpha)

1540 (H-alpha)

1546 (CaK)

1548 (CaK)

1550 (CaK)

1552 (Infrared)