Thursday, January 31, 2008

Maxvision 127ED

A friend reminded me of the above option, it's a 127mm f/7.5 ED triplet.

Aperture is 127mm and focal length is 952mm.

Dew shield retracted, it is ~840mm long and when extended, it's like 1020mm long, the weight is like 6.5kg, not very heavy considering that it's a triplet. The diameter of the dew shield is slightly more than 150mm, i.e. my Cheapy-ERF will still be large enough, finally at f/7.5, the PST etalon module should be happy with it.

Last but not least, it's pretty inexpensive, and in case there's not enough back focus, I can always ask my local friend to cut it... since it's cheap and so I won't hesitate to cut it. :-)



1. Solar imaging:-

- to be used with the Cheapy-ERF, PST etalon, BF10, this will ensure internal reflection free; since it's also less than 1000mm, the BF10 will still be big enough to cover the full solar disc, maybe good for DSLR at prime focus

- to be used with my Herschel Wedge, for excellent white light observation

- to be used with my Herschel Wedge + Baader CaK, for the best possible CaK

2. Deep sky scanning:-

- to be used with my Unistar Lighter at lower power, with my Pentax 40mm XL, it yields 2.73 degree which is very nice!

3. Planet imaging:-

I guess it's do-able with my LXD55


With the very long tube, I guess I can only hide it behind the door, maybe to put the front inside a big plastic box with some dessicant inside

Monday, January 28, 2008

Pittman motors

I got two Pittman geared motor at home, they're from my old Nexstar mount.

My impression is that they're of 1/4" or ~6mm shaft, i.e. very suitable for my project, therefore, I tried to check its speed. On applying 2.4V to its terminals, it won't move, but I could feel there's some response inside, but there's certain no visual movement. On applying 6V to its terminals, it moves pretty quickly, probably too quick for autoguiding kind of movement, however.

Since it won't move at 2.4V, I guess I will need PWM to control its speed, and that will complicate the circuitry a lot, and so I guess that I will continue to look for alternative motors.


On more careful testing 2.4V is enough to turn the motor, and the speed is not too fast, however, I checked that the shaft is too small... maybe like 5mm or similar.


I've also tried to hand fit my existing tiny motors to the focuser knob of my C5 OTA, and I guess it's not too hard to put them together, maybe I can use one for them to motorize the focuser of my C5.

Sunday, January 27, 2008

Cloudy day task: soldering the L298 motor driver

It has been cloudy, so there's no solar observation (also any other forms of observations) for this weekend. Instead, I began my soldering work for the autoguiding project.

I ordered the Compact L298 motor driver kit from Solarbotics but got no time to really solder all those components together. This kit allows you to control the two motors by using relay signals, since it's TTL compatible and so it accepts ST4 compatible autoguiding signal as well.

The soldering process is quite easy, despite the small PCB, you still got a lot of rooms. You can see from the following photographs that I ain't a skilled people in this regard, but I managed to get it done fairly quickly, like within an hour.

You can see from below that I am never a skilled guy in soldering.

I tested the finished kit with my elder daughter Alby and she's really happy with it. It got four LEDs to indicate the status, and we also hooked up a tiny DC geared motor to show the direction of the current flow.

Thursday, January 24, 2008

Canon 450D

Today we saw a lot of news about the new camera from Canon, the 450D.

It comes with Live View which is really nice for focusing especially with a telescope, however, the increase in the pixel count will probably also increase the amount of noise for deep sky imaging.

Also, just like 400D, the dust removing system will likely make the removal of the low pass filter harder than before. With the low pass filter in place, the sensitivity for H-alpha signal is going to be weak, that means it's not very good for deep sky imaging.

To me, I'm considering a DSLR again mostly due to the upcoming total solar eclipse, for that matter, the low pass filter and the increased noise level shouldn't be very important. However, Live View will definitely help in focusing, especially if there's no big sunspot on the solar disc. So, I actually consider this camera more suitable than 350D/400D.

And I guess Canon will probably discontinue 400D when 450D finally comes out, but I believe 350D will be here to stay for one year or two, to target on the really entry level market. It would always be nice to buy a 350D later for modification, if one day I'm interested and have more time for deep sky imaging.

Remarks: the estimation on the noise level is pure speculation, we can only tell when it comes out; again, the H-alpha sensitivity is also yet to be checked.

Wednesday, January 23, 2008

Looking for a better scope

My C5/PST setup has internal reflection issue, the problem is from the blocking filter, it reflects light back to the secondary. It seems like it's hard to correct in a SCT kind of system. A refractor is a must, therefore.

From the past experiments, I know we need at least f/7, and f/8-f/10 would be even better for the PST etalon module.

A bigger refractor will also be nice to fully exploit the potential of my Herschel Wedge, and therefore also the Baader CaK.

At the same time, I believe the C5 would be the maximum for my TG-SP II for planets, however, I found it's not the case, it's simply too heavy, I will need my LXD55 in that case. So, a C5 is no longer the choice.

A ~4" to 5" refractor would be nice, and to keep my LXD55 happy, I guess that I'll need to stay below around 12lb. That would be fine with my Unistar Light mount for visual observation as well.

Tuesday, January 22, 2008

Images of the Tilted ERF experiment

Notice: It's an extremely dangerous experiment, please don't do it.

A plastic cylindrical box is cut by using a cutter roughly, it will not be good in the first cut, but we can always use a good scissor to make it better.

Then the ERF is attached in the most ugly way, a firm and secure attachment is more than the outlook:-

Another angle to show the tilting angle:-

Finally, to put it at work... you can see light leakage, so it's better to cover it, but since that was a cloudy day, it does not affect much:-

A last note is that, this tilting does not help to remove the secondary shadow.

Monday, January 21, 2008

Shaft coupling

The surplus 1/4" shaft coupling works perfectly on the slow motion control shaft of the TG-SP II, of course, it's too big for the small geared motors.

So now I've two choices:

1. buy another small shaft coupling with 3mm bore and with OD ~ 1/4 inch OR

2. buy another set of geared motors with ~ 1/4 inch shaft

I guess I prefer (2) since the small motors which I got now could be a bit too fast (5 RPM at 6V) and maybe too small to deliver enough torque. And these smaller motors can be left for other projects like motorizing different focusers.

Sunday, January 20, 2008

20080120 Sun

Clear sky!!! We got clear sky today here in Hong Kong, transparency is like 7/10, seeing is 5/10, a pretty good day, the sun surface is very silent, virtually nothing and we got two prominences. Borg 45ED II, SM40/BF10 used at first, and then C5/PST next. I also used the Canon 10x30 IS to have a look in white light, nothing basically.

Let's show three shots first, they're taken at 1525 (GMT+8), 1526 (GMT+8) and 1536 (GMT+8), the first two are taken with Borg 45ED II, SM40/BF10 at prime focus, and the last one is double stacked with a PST etalon. The first one is target at the surface detail and the second one is on the prominences, the last one is taken with exposure suitable for surface detail. You can see that the double stacked shot shows both surface detail and prominences pretty well at the same time.

And as you can see from the 1526 (GMT+8) shot, you can see there're two prominences, and here're two close up taken at 1528 (GMT+8), and 1530 (GMT+8), they're taken with Borg 45ED II at 3x, SM40/BF10:-

Finally, we have five shots taken with the C5/PST setup:-

1551 (GMT+8):-

1553 (GMT+8):-

1600 (GMT+8):-

1606 (GMT+8):-

1613 (GMT+8):-

I really love this kind of prominences especially when we have no surface detail to look at :-)

Saturday, January 19, 2008

20080119 Cloudy Day Sun

Seeing 1/10, transparency 0-1/10, totally covered essentially, these were taken with near maximum gain and 1/2s exposure at f/10, C5/PST with tilted ERF (experimental setup), due to the poor condition, no shots can be taken, just a few short AVIs and one of them shows a really big prominence...

Another single frame shot, no time to really focus or adjust the exposure:-

Tilted ERF

Last night I have made a new cell for my Cheapy-ERF, the former mechanism is better, more elegant and secure, but this new one is aimed as a prototype of an alternative concept - in order to remove the internal reflection.

Since the internal reflection is pretty strong, I believe if the tilting is effective, the overall image quality will improve significantly, the contrast will be much better and I believe it can be readily seen in the histogram of the image capture.

So far it's sunny, and I believe that I'll have chance to test it today.

Once the design is proven, I will try to find someone to make a more permanent and secure setup... right now it's based on a $3 cylindrical plastic box and a lot of duct tapes only, have to be extremely careful when used.


1316 (GMT+8): it's very cloudy now, essentially a total covering, however, I still setup the C5/PST with tilting. During some short breaks when cloud got thinner, I actually saw the same internal reflection. Therefore, it's not about the ERF, I tilted up the whole ERF by at least 15 degrees, but it's the bright secondary shadow was still there, so this route is not viable.

Wednesday, January 16, 2008

Inline shaft coupling

I found a surplus source with google, and the price is of course, better from normal sources. However, after submitting my order for 5 days, I got zero response... but then I finally got a response last night to confirm my shipping cost.

Originally, one the same day, I'm about to order from another source, it's more expensive, but it's a 4mm to 6mm shaft coupler which should suit the purpose better, but for some reason, I cancelled the order in the last minute, or else I will have some what duplicated items.

Let's see how it works out, I guess that I will need something to secure a 3mm shaft in a 6mm port of the shaft coupler, or I will need to buy another two motors with 6mm shaft.

Tuesday, January 15, 2008

Printing solar photographs

I had a big solar mosaic done early 2007, and yesterday I've some photographs to be printed, so I took them all to a shop downstair to have them printed.

The shop told me that since the size is weired (17xx * 17xx), and the image is too close to the boundary, part of it might get cropped.... Oh right... as a sort of tech guy, I thought it was easy to add black space around the image and then to have it printed without cropping, but then the guy's response should not be unexpected... he said, yes it's possible but it should not be $0.9 HKD including printing! For me, it's so easy, actually for him, it should be easy as well, but then they're doing business, if everyone did like me, they will spend far more time. But soon he added, okay, this time I do it for you. :-)

The outcome is fairly nice, I seldom have my astronomical photographs printed on paper, I mean printed by shops, even if I printed them, I did it at home by myself, usually by ink-jet paper and sometimes photo paper.

Saturday, January 12, 2008

20080112 Sun

Seeing was no good, just something like 3/10, transparency could be pretty high when the cloud was away, like 6/10, but there were quite much cloud around.

AR980 still there, and the active region with reversed polarity (i.e. sign of the new cycle) could be seen as well, near the equatorial region.

1318 (GMT+8), surface detail exposure, so much cloud at that moment so not really got time to tune the Tmax to the best:-

1318 (GMT+8), prominence shot, not too much to see:-

1321 (GMT+8), the active region near the middle of the solar disc, 3x barlows added:-

1322 (GMT+8), AR980:-

1324 (GMT+8), another AR980:-

1327 (GMT+8), close up of that prominence, 3x barlows:-

All taken with Borg 45ED II, SM40/BF10.

Friday, January 11, 2008

L298 motor driver arrived

It's pretty quick, it arrived. It's The Compact L298 motor driver from Solarbotics. I might have some time to do the soldering work this sunday after my busy services in the church this weekend.

It's really compact, I guess it fits ito a hand controller box easily as well, actually, I planned to use it for autoguiding signal, but now I found it's an overshoot, since from Shoestring astronomy, I know their guiding signal is strong enough to push SPDT relay, which should be enough for driving motors. Anyway, it's a learning process, I went the complicated and more expensive route.

Right now the problem goes to the mechnical parts, I guess right now I've at least 3 or 4 workable methods to do hand control and receiving autoguiding signal... I ordered some inline shaft coupling last night, but due to the size difference of the shaft, maybe it would cause big trouble. Also, since the guiding actions are pretty small, I should have very good mechanical construction or else they will be eaten up by backlash, or whatever mechanical imperfection, etc.

Originally, I was think about a motorized focuser, but the accuracy for driving a mount should be way higher, anyway, I'll just move on and the bottom line is, it will be a fun project!

Thursday, January 10, 2008

Internal reflection from the Cheapy ERF/C5/PST

It suffers from internal reflection and it really washes out detail and reduce the contrast by much...

I've tilted it up slightly but as I can tell from the herschel wedge image, I know it's still well within the field of view. So, I guess that I'll have to tilt it further.

Maybe to build something like the mechanism of a Tmax... of course, to make it simpler so that the cost will be lower... Time to go to the drawing board again.


Just a random thought, maybe a small rubbish bin will do the trick... grin

Connecting the motor to the slow motion control

This is that TG-SP II motorized guiding project.

Last night I really try to place the motors around the slow motion control knobs to see different possibilities. The shaft under the knob is 6mm in diameter, while my motors are having 3mm shaft, and I find difficulties in locating 6mm-3mm inline shaft coupling, all I could find are those 6mm to 5mm or maybe 6mm to 4mm (unsure if I saw it?), but I guess maybe that is enough, or in the worst case, I just find other motors.

There're two potential issues by using inline shaft coupling. First of all, the motor will extend all the way from the shaft, while the motors are pretty small ones, I don't know if it will make the transportation of the mount harder, since we got something sticked out which can be bumped, not exactly a good idea. Secondly, I found the shaft hard to turn, at least it cannot be turned with my fingers. The motors are pretty powerful, but I have to try before I can really tell that the motors are powerful enough. I suppose that they can do, since some motorized focuser work like this, i.e. directly drive the shaft.

There're two other possibilities, they're similar. First is to use two sets of gears, the advantage is that, the gears can be bought to match the size of the shafts, and the motors can be placed side by side with the shaft under the knobs, thus making them the same as with the knobs, i.e. nothing protruded outside like that of those inline couplings. Secondly, I could choose suitable gear to make the driving torque stronger, and this will ensure that the motor can turn the shaft effectively. Another possibility is to use timing pulley and timing belt, for that to work, I believe that the timing belt can be used to drive the existing slow motion control knobs directly, and it works similarly with the gear as well, but problem is, I probably need to derive an engagement mechanism for the belt, i.e. to make it tight enough to drive the slow motion control knobs. That part could be hard to DIY.

It terms of DIY ease, the inline coupling way is the best, but it's not the best design overall. Timing pulley is the best design I'd say, but it's hardest in terms of DIY.

Wednesday, January 09, 2008

DSLR choice revisited

It's getting funny again. My friend told me that we could have very cheap service and source for Baader replacement filter for Canon 350D, so everything added together will be just around HKD 5xxx, that means a new Canon 350D, plus a kit lens, and modified with Baader filter! But I checked that the new sharper IS kits lens is not available with the Canon 350D.

What's so interesting is that, with the Baader replacement filter, we can actually take daily shots with custom white balance, autofocus is still functional as well.

Frankly, comparing to live-view, the H-alpha capability is definitely more important, and the noise level of a 350D should be better as well, thus making it fundamentally more suitable for deep sky imaging, or H-alpha solar shots. Live-view is something for convenience, and given enough patience, it's not a hindrance.

A side note is that, I really think that it takes time to learn and get use to a camera before one can really use it. I got such a strong feeling after the last two Mars session - I even found a hard time to center Mars enough to be captured by my DBK... So, I think that I shall get more time to use it first.

Tuesday, January 08, 2008

Local astronomy forums

For local, I mean Hong Kong, those forums are mostly Chinese based. English is also welcome but for non-Chinese speakers, they might not be able to understand all the posts:

- This is now down, this is like the mother of most astronomy forums in Hong Kong.

- This is run by the Hong Kong Astronomy Society

- This is run by Mr. APO Che, one of the active amateurs in Hong Kong

- This is run by Mr. Wong Lung, one of the pioneers of ATM in Hong Kong, this forum is mostly for his ATM students

Sunday, January 06, 2008

DBK Orion Nebula test

The viewing angle is very bad, I couldn't reach out enough until I discovered a way to append two dovetail plate together, but then the camera already hit the window frame so that I only got less than a few minutes of exposure, so I did a stack of 9 shots, each of 11s. Stretched crazily to show whatever possible. Just a test, by no means real attempt.

DBK with Fujinon 75mm f/1.8 wide open.

I also tried that Cosmicar 6mm, it's large enough to cover the whole Orion.

Red hot Herschel Wedge!

I've installed a small heat sink on my Herschel Wedge to cover the bright sun light and to let it cool down, let's see the following:

Hey, it's red hot? No, it's just red light. Normally, we cannot use a Herschel Wedge with a SCT, but since I've placed an ERF in the front, I can, but the light will become red in color, so it makes a false impression of being red hot! :-)

20080106 Sun

Followup observation of yesterday, transparency at 5-7/10 (scattered thin cloud moving around), seeing very poor at 1/10 to 3/10 at best. Borg 45ED II, SM40/BF10, prime focus for full disc, 3x for closeup. Borg 45ED II, APM Herschel Wedge with Baader CaK for CaK. Finally, ERF/C5/PST at prime focus for close up again, and then C5/ERF/APM Herschel Wedge for white light.

First, let's see how poor is the seeing, you can see the shadow of the secondary, taken by ERF + C5 at f/30:-

First two are taken with SM40/BF10, Borg 45ED II at prime focus:-

1515 (GMT+8):-

1516 (GMT+8):-

Next three are taken with the same setup with 3x barlows:-

1521 (GMT+8):-

1522 (GMT+8):-

1524 (GMT+8):-

1531 (GMT+8), Full disc CaK, Borg 45ED II, APM Herschel Wedge + Baader CaK:-

1540 (GMT+8), C5/PST:-

1542 (GMT+8), C5/PST:-

1544 (GMT+8), C5/PST:-

1546 (GMT+8), C5/PST:-

Saturday, January 05, 2008

20080105 Sun

The sun becomes active again, we have AR980 and we even got more behind it. Borg 45ED II used, with SM40/BF10 for H-alpha, close up with 3x barlows. APM Herschel Wedge and Baader CaK for CaK shots, close up again with 3x barlows. Both by DMK 31AF03.

1355 (GMT+8), SM40/BF10, Borg 45ED II prime focus, surface detail:-

1356 (GMT+8), SM40/BF10, Borg 45ED II prime focus, prominences:-

Combined with the above two:-

1400 (GMT+8), SM40/BF10, Borg 45ED II with 3x, AR980:-

1403 (GMT+8), SM40/BF10, Borg 45ED II with 3x, AR980:-

1405 (GMT+8), SM40/BF10, Borg 45ED II with 3x, focus on the new active region following:-

1406 (GMT+8), SM40/BF10, Borg 45ED II with 3x, some small active region on the sun surface:-

1407 (GMT+8), SM40/BF10, Borg 45ED II with 3x, some small active region on the sun surface:-

1413 (GMT+8), APM Herschel Wedge, Baader CaK, Borg 45ED II at prime focus, full disc:-

1413 (GMT+8), APM Herschel Wedge, Baader CaK, Borg 45ED II at 3x, area around AR980 and the active region following:-

It's grear to learn that the new solar cycle has begun, let's keep watching! During the last year or the last few months, I begin to feel 40mm aperture is not enough, but when it's active again, we will begin to feel the lack of field of view!