20070930 Sun

Seeing was 1-2/10, transparency 0-2/10, cloudy moved in and out.

Tried red filter + Ranger + PST etalon and it does not work at any configuration, both PST-BF5 or regular BF10, with the 2.5x in front of the nosepiece of PST etalon, all failed. I suppose that it takes closer to f/10 to make it work.

Next was Borg 45ED II with SM40/BF10, of course, it works, but the contrast was low due to poor transparency. Adding a PST etalon did help a bit.

1512 (GMT+8), SM40/BF10, <0.7A:-


1517 (GMT+8), SM40/PST/BF10, <0.6A:-


All taken with Borg 45ED II.

Issues in a C5 PST configuration

First issue: two picture says it all, it's internal reflection. The strong sun light after passing through the Cheapy ERF, is still strong enough when it comes to the SCT corrector, and then light is reflected again by the ERF, creating a secondary ghost image. Another source of secondary reflection is that, light going to PST etalon is reflected partially back to the SCT secondary mirror, to create another ghost again.




Yes, it's internal reflection. You can clearly see the shadow of the secondary, right?

It's even worst at first, but I managed to tilt up the ERF in order to kick the reflection out of view a little bit more. But it's there still. The tuner in the PST etalon module does help a bit more, but still, it's still there.

Need to find better way, or else contrast really suffers.

Such effect is best demonstrated by the histogram, all the signal is on the right side, without any signal at the left... similar problem in white light can be seen and thus, I guess the reflection from PST etalon is not as big as the one from Cheapy ERF and SCT corrector:



Second issue is newton's ring:-

20070929 Sun (AR971)

The sun has been silent for quite some time. The sky has been cloudy too.

Finally, the sun is in a good position from inside my home, so that I can use my C5. While waiting for the sun to go to a really good position, I did an experiment with my C5 with my Cheapy-ERF, and the Herschel Wedge. A Herschel Wedge can usually only be used with a refractor, but with a ERF in the front, it can also be used with my C5.

The first shot is conducted with half aperture still blocked, Cheapy-ERF + Herschel Wedge + ND3 at AR970, C5 at f/10:-



Seeing was no good at around 1-2/10, transparency was like 4/10 at first but dropped to 2/10 for the last few shots. Peltier cooling was used except for the first few shots, but I only powered the Peltier/fan using power from USB, so the cooling is just about to put the setup back to a few degrees below ambient, also due to the direct sun light.

** Internal reflection is the prime killer of this setup, if the Cheaper ERF can be tilted further, I believe the contrast will increase tremendously ** The last few shots were fine tuned by tilting the Cheapy ERF a little bit more to reduce internal reflection.

1508 (GMT+8):-


1519 (GMT+8):-


1530 (GMT+8):-


1532 (GMT+8):-


All kinds of issue come out like internal reflection or ghosting, dust, newton's ring, etc.

Cheapy ERF configuration

I found the light at the prime focus of my C5 is pretty hot even with the Cheapy-ERF in place.

It could burn the skin within 5s I believe. Sounds bad?

However, I have just gone through an imaging session of more than 20 minutes, but the PST etalon is still in good sharp and still maintain a stable temperature, otherwise, the bandwidth cannot be kept to show all those detail.

Of course, I believe that I will still want to find way to reduce the temperature further, in order to optimize the performance, and be safer at the same time.

20070926 C5 Sun

It's the first chance which I used my own PST, the sun finally goes to a nice position from inside my home. No big thing there on the sun, but some tiny stuff become big at 1250mm or even 2500mm! Small etalon becomes a big one, small prominence becomes a big one, too.

Seeing was no good at 1-2/10, transparency quite nice at 3/10.

All taken with my C5, a cheapy-ERF, a PST etalon, BF10, and a DMK31AF03, with or without a Tele Vue 2x barlows:-

1342 (GMT+8), f/20:-


1345 (GMT+8), f/10:-


1354 (GMT+8), f/10:-


1355 (GMT+8), f/10:-


1356 (GMT+8), f/10:-

20070922 Narrow band H-alpha Solar shot

The sky was no good, but transparency is a bit better than that of the last night, I'd rate it as 3/10, seeing is still bad at 2/10 at most. Borg 45ED II, DMK 31AF03, Coronado SM40/BF10 filter set.

The solar disc is very quiet, we got only one small but tall prominence, and a few QRF on the surface.

1327 (GMT+8):-


1329 (GMT+8), prominence only:-


1330 (GMT+8), image pending.

Finally, I made a shot with my window closed, to evaluate how worse the image would become. I still have the remote solar imaging project in mind, but the limiting factor would be that, I'll not be able to keep my window wide open during the day, due to the children at home, as well as sudden rain, etc. The quality below would mean that maybe I'll have to give up?

20070921 Moon by an astronomy addicts

The transparency is oh so low, it's something like the worst other than totally cloudy. Seeing is bad too. The moon is the only visible target, deep yellowish, closer to orange/brown maybe.

With my Borg 45ED II at prime focus (f/7.2), even 30 fps will be too fast since the shutter is 1/15s. I even tried a 2x barlows in the next shot, and it means 1/8s exposure, i.e. 7.5 fps only.

2254 (GMT+8):-


2255 (GMT+8):-


2300 (GMT+8), 2x barlows:-


Why I still setup my gear under this poor situation? It simply proves that I'm nuts, an astronomy addicts who just want to do some astronomy whenever not impossible (I'd rather not say whenever possible for it's really whenever not impossible is closer to reality).

A wide field lens for DBK/DMK

Just ordered a Computar 2.3-6mm f/1.2 CS mount lens.

It's my first CS mount lens, my first Computar lens, also my first zoom lens for DBK/DMK, it will be my wide field work horse. I don't expect very high quality, but just to get a taste of wide field imaging.

Should have well over 100 degree field of view horizontally with my DMK.

Cost $28 USD shipped, fairly nice deal it seems.

20070909 Sun

The sun moved to a favorable location from inside my home, no need the long mounting plate to extend the Borg outside of my apartment window any more, I hope to try out my C5 soon.

Very little activity, several small prominences, seeing 5/10, transparency 2-3/10.

Borg 45ED II, SM40/BF10, DMK 31AF03, PST etalon:-

1507 (GMT+8):-


1508 (GMT+8):-


We soon got cloud out after these two shots, originally I wanted to try to compare the above to a setup without PST etalon if the sky was still clear enough.

New Peltier Cooler

The outside. The box is a name card box, all the wires are connected to the power socket, i.e. the Peltier module and the CPU fan shares the same power supply. I've tested the setup with 5V (from USB port) to 12V, they work well within this range. You can also see a DIY USB power cable.


The inside. All those ugly wiring can be seen, the Peltier is installed with blue tack, both for insulation and to keep dew out of the box.


The Peltier is installed on the left side, since I found the amplifier glow is seen on the top left. You can also see the power socket on this side.


The back, nothing except a Firewire socket.


The bottom, we can see the mounting plate, with 1/4" sockets.

I shall find a better mean to keep it mounted and yet removable from the camera. Also, I need to find ways to keep dew out, i.e. the shield the gap between.

New Peltier cooler configuration

It's done basically, except I still need some time to think of a better attachment mechanism, right now it's attached via a garment type rubber band, rather ad hoc but work, I shall use Velcro tape soon.

This time, the Peltier module is placed on the left side of the camera since I found the amplifier glow is like on the upper left, wonder if it will help or not?

The box is much smaller this time, so the dew and heat insulation should be better. And this time, a 12V power is applied on the Peltier with a larger fan, so the cooling effect should be stronger. (Remarks: after the test, I found that the unlabelled transformer which I used should be around 5V only)

I've conducted a few test, first one is 3m15s exposure each, 5 uncooled frames and then follow by 5 cooled frames, zero gain:-

Next is 10m30s exposure each, 3 cooled frames, followed by 6 uncooled frames, zero gain:-

And then 132s exposure, 633 gain, a test of shorter exposure with higher gain, 12 uncooled followed by ** cooled:-

Again 132s exposure, 1023 gain (maximum) but reduced to 903 gain after first 3 frames due to excessive noise even cooled, later reduced to 750 gain after another 3 frames, 12 cooled followed by 12 uncooled:-

Finally, 312s exposure, 612 gain 5 uncooled to 5 cooled:-

After knowing that the source was indeed 5-6V only, I searched around and found a real 12V 5A source. I plugged it in and the fan spinned really fast! And the heat sink really got very hot which should be, I know I am going to re-do everything soon.

Packaging the Peltier Cooler

Found a small piece of thin plastic, hope it's large enough. A socket will be cut for the Peltier module, while the heat sink, and the fan will be on the other side, I will also mount a 12V power socket there, and this plastic mounting board will be used for holding the wires.

The whole thing will then be mounted on the DBK/DMK by using elastic band, those used for garments, and Velcro tapes so that it will be removable and re-attachable.

The plastic mounting board is from some existing parts, the elastic band and the Velcro tape amounts for $4 HKD, really cheap :-)

--

Finally, I've used a small plastic box which holds my name card when it comes from the printing factory. It's large enough to hold everything, but small enough to be very portable.

Another experiment on Peltier cooling

I've replaced the fan with a bigger one, this one is bigger than than the heat sink a little bit, so the cooling is much more effective. I'm using a bigger fan in the hope that the Peltier can be driven by the same 12V source instead of using a 6V source. Previously, if I use a 12V source, the fan cannot drive the heat fast enough so the cold side of the Peltier will be overwhelmed, and therefore, I will have to go back to 6V. This is both inconvenient and not using the Peltier to its full potential.

In short, the experiment is very successful. I turned on the Peltier and the fan for over 15 minutes and the cold side is still cold, even with a heat load (which is my body), the heat sink is very hot, even a bit too hot to touch, but it didn't overwhelm the cold side! That's enough. The air driving out from the heat sink is a bit warm.

When I finished the experiment, I turned off the power to the Peltier first and I found that the cold side get warm very rapidly, due to the high temperature from the hot side, but since the fan is still on, it got cooled down too within one or two minutes. The heat sink got cooled down within 10-20 seconds (I didn't measure).

So, finally, I plan to use the whole thing without the moisture insulation box, since the cooling effect is not that strong. Without a load, there's some water droplets on the cold side, but with a load, no water there, or maybe just a trace, so I believe dew is not an important issue here. Even if there's some dew, I believe a simple plastic bad trick, with dessicant would do the job rather than using a full size box which is bulky and troublesome to maintain.

So, now I will need to find a small plastic board, to drill holes for the cable, install the power socket, connect the power to it, make a slot for the Peltier, hold the fan, heat sink and Peltier there, maybe add an adjustable clamp for the attachment of a camera, done.

I believe it will stay on my DBK for most of the time. Cooling is not very useful for the sun since the exposure is short enough, of course, maybe it's useful too? So, a removable mechanism is desirable so that it could be used with my DMK, too.

Another short project for the coming weeks.