Wednesday, March 28, 2012

An idea about automated polar alignment

Now we have smart phones which really help us on finding our targets.

I'm thinking we should be able to use them to align polar alignment.  Most, if not all, smart phones are equipped with a camera, and through afocal imaging, the camera could detect a bright star in the eyepiece. 

By following the drift of the star, the smart phone can actually help us to do drift polar alignment by asking the user to adjust the polar axes.  It could be done rather easily.

Monday, March 26, 2012

20120326 Sun

Testing my Maksutov again, but then while I was waiting for the sun to get into a better position without aperture blocking, cloud rolled in.

First one was taken at prime focus, i.e. 1500mm:

And then another closeup at 3000mm:

For comparison, I also captured a 2400mm version with my Ranger and 5x Powermate:

So there seems to be nothing wrong with the Maksutov now.  Of course, I will need to test further under better sky.

20120326 Mars

I found that since there's a tall building nearby now, I only have a very short imaging window from inside my home for the Mars, and it's less than 30 minutes.  Virtually useless unless I keep waiting all night since such a short window could not be calculated exactly easily.

Here is what I got last night, very bad!  Ranger with a 5x barlows:

Featureless ball of light.

20120324 Sun

Conventional wisdom told us that the wrinkles on the filter does not affect the image quality much, however, I found that it's not the case for a Maksutov, it is because the internal reflections between the secondary and the filter could become very complicated due to those wrinkles!

We have two testing sample behind which the aperture was over 50% blocked by my window frame, but still it's enough to show the improvement on contrast.  The first shot is taken at prime focus of my 127mm Maksutov:

Next is taken with a 2x barlows, i.e. 3000mm focal length:-

I'm longing for a chance which I could image with full aperture.

Friday, March 23, 2012

Compact field power

Many years ago when I was using my Giro mount with Tech 2000 GiroDrive, I have bought a 12V 7Ah Sealed Lead Acid battery to power everything.  It has enough juice for a whole night of observation and it even supplies power to my Sony Vaio U3.  Then I moved to a Meade LXD55 and I continue to use the same battery.  It works well, too.  Until then, I have bought a Takahashi TG-SP II for wide field imaging and I bought another 6V Sealed Lead Acid for it.

After so many years, I eventually settled myself with a GOTO Mark-X mount with a modified Carton tracking motor (the one with Tele Vue System Mount), and now it takes 9V.  With its very energy efficient controller and motor, now I only need a small battery.  In order to improve the overall portability, I've sold all my Sealed Lead Acid batteries together with the charger, and the transformer for notebook computers.  I turned myself to a Lithium battery pack.

This battery features a solar charger which works even under overcast sky, and in strong direct sunshine, the solar panel gives 0.8W which is not bad.  It provides 4.5V/5.5V/6.5V and 9V and the maximum output current is 800mA.  Now I just leave it near the window and it will gather enough juice for my weekend observations (which is usually one to two hours at most).  Of course, if I plan for a longer observation session, I will charge it via USB.

This battery is very light and compact.  Its rated capacity of 2600mmAh is probably real according from my test.  I have tried to use it with my Mark-X and it works for over 5 hours without problem.  Theoretically, it will work over 8 hours.  However, given the efficiency drop due to voltage stepping and also discounted capacity, I would expect around 5 hours.

This is a very good battery for an energy efficient mount.   However, it does have one problem.  One day with strong sunshine while I was doing solar imaging, I found that the controller was complaining low power but the battery should be charged.  Why is that?

I found that when the solar panel was working, the internal battery will be switched to charging mode and it will not delivery power.  And in that case, only the solar panel will be providing power and at 9V, the 0.8W panel at fully efficiency, will be just giving 88.9mA which is just half of what is required (160mA) by my motor and controller!  No wonder it was complaining.  In order to verify such hypothesis, I turned the solar panel upside down and then the controller stop complains at once.

This is no good.  I was thinking that I could harvest solar energy while imaging but then I found it's not supported by this battery pack.  Anyway, it is not too critical.

Another side note about this battery pack is that, it features three bright white light LED and they could be nice for us to setup and tear down the setup on site.

The bottomline is that, given its relatively low capacity, we should better have two such battery pack or we will need some short of backup power source.  While the solar panel is a interesting thing, we just could not rely on it.

Monday, March 19, 2012

For Sales: 127mm Masutov (SOLD)

Up for sales is a  Skywatcher 127mm Maksutov (same as Orion), it's compact and high quality.  I bought it for white light solar imaging but I soon found that the silver secondary was creating internal (multiple) reflections between the solar filter.  Other than that, this small scope works out very well.

I have made a belt driven focusing motor for it.  The motor could be mounted and taken away within seconds.  Notice that a hand controller is not included, you may use any controller for DC motors like JMI or Rigel, etc.  I can include a DIY controller box for $200 HKD extra, or you can add $400 for a USB controller box for computerized focusing.

Detail of the focusing motor:

Come with end caps, 1.25" visual back (with T thread), Vixen compatible dovetail.

The color patch on the lower left shown on the picture is just reflection, the objective is clean with little dust.  Ask for $1999 HKD (SOLD).

Sunday, March 18, 2012

20120318 M41 and M42

The transparency is good and thus I did some imaging from inside my home.  Due to the serious light pollution, I'm using 20s exposure at f/2.8 with 200mm focal length.  I'm shooting M42 first (222 shots taken) and when it sinks too low, I turn to M41 then (95 shots taken).

I believe that I should use a better flat-field.

20120318 Sun

Today the sky is very clear, I would rate the transparency 8/10 which is rare in Hong Kong.  Seeing is rather stable, I would say it's like 6-7/10.

I pulled out m 127mm Maksutov for testing, but to my surprise, the contrast was low.  However, on switching to my Ranger, the contrast is way better, I suspect that the internal reflection between the solar film and the silvery secondary is very serious!  When the sun was sinking in front of a tall building, the complex silhouette confirmed this hypothesis.

First up is a full disc taken with a DIY reducer with my Ranger at prime focus:-

Then, we have a close up taken with my Ranger and a 5x Powermate.

I believe that I shall sell the 127 Maksutov, keep my Ranger as my only telescope.


I'm using the solar re-chargeable pack today for imaging.  We have strong sunshine today but then I found the motor controller was complaining about low battery.  The battery was fully charged via USB previously and I found that under sunshine, the output seems to be solely from the solar panels instead of the built-in battery!  Therefore, I must turn the panel upside down in order to make sure that it's using the internal battery instead.

A rather silly design.

Saturday, March 10, 2012

Cabinet Clearing Sales Update

Package deal: $899 HKD takes them all! 

Individual items price reduced, all reasonable offer will be entertained, just don't want to waste all these stuff.

Shoestring FCUSB, virtually new never used in the field, ask for $400 HKD. Control and power your JMI focuser via your USB port. 

SkyAtlas 2000.0 Deluxe Version, ask for $200:-

And the inside, a pen is placed along side to see the size, it's really a good visual reference!

Next is a 70mm doublet (f=500mm) mounted and with 77mm thread, suitable for macro imaging which brings the closest focusing distance down to less than 500mm. Ask for $150 HKD.

Celestron Nexstar mount parts, the gears were still available at $100 HKD as shown below, the bigger one was about 6" in diameter and the smaller one was 5".  Someone said they have "24 pitch teeth".  The bigger one has 288 teeth and the smaller one has 240 teeth. The central bore is 22mm.

Another custom machined 2" to 1.25" adapter, it's pretty heavy and could be good for balancing light weight 1.25" eyepiece and heavier 2" eyepiece. With two locking screws for added security.  Ask for $50 HKD.

Originally for my Gitzo G1415 when I lost one of the spikes on the legs, so I still have two remain. I've sold my G1415 and now they're sitting idle... very hard to find in Hong Kong and even the distributor refused to order them for me. Ask for $200 HKD.

A small 7-14x monocular, good quality for this size, ask for $50 HKD.

Free stuff when purchase all:

One of those screw type cases was sent as free gift already, so two eyepiece boxes and a simple tripod is still available as bundled free gift:

Thursday, March 08, 2012

Minor improvement on the Mark-X DEC arm

I've enlarged 2mm of the mounting holes of the aluminium bar for mounting the DEC arm.  By doing that way, the head of the mounting screws could sit all the way into the mounting hole for shake free and more secure connection.

Previously, I found that the DEC arm was loosen a bit after several operations.  I suspect that's the reason behind is that the mounting screw was not getting all the way inside, now the DEC slow motion control block got a few more turns of threads for fixation and the mounting screw has less room for shaking as well.

Wednesday, March 07, 2012

Carton CXD-1 Field Power Solution

After selling my heavy SLA, I have turned to those portable Lithium polymer battery and I have got one with solar charger and also a few LED as flashlight.  It's rated at 2600mmAh with 4.5V, 5.5V and 6.5V and 9V.  It has a mini-USB socket both for charging and powering.

The solar charging panel seems quite good and even with an overcast sky, the charger started working.  Of course, expect extremely slow charging under this situation but then I won't rely on it but treat it as a bonus during solar imaging or observation.

This CXD-1 controller requires 160mA at 9V and it has a center negative pin.  In order to reduce the complexity of the wiring, I've soldered another cable into the circuit board directly.  That power cable is a retractable USB cable from a dead device:

I assume that the 2600mmAh rating is for 4.5V and thus, at 9V, it means 1300mmAh.  Given these products were usually over-rated and also with the efficiency reduction due to voltage conversion, I guess it would mean 700mmAh?

So, it should work for 700 / 160 which means over 4 hours.  At the time of writing this blog entry, the mount has been running for nearly 4 hours and there is no sign of low power yet.


After 5 hours of continuous tracking with some occasional 4x fast movement, it's still going strong.  Actually, if it's really rated at 2600mmAh, we should have enough juice for 8 hours of continuous usage.  Frankly, 5 hours are more than enough for me for I rarely observe more than 5 hours.  I simply do not have the luxury to do so.

For day time events like solar eclipse or the upcoming Venus transit, the solar panel should help to extend the usable tracking time.  For night time events like a total lunar eclipse, it's still pretty enough for I will only do half of the whole process.


For very long observation session, I've a backup solution.  It consists of 8AA re-chargeables  (Eneloop) which deliver 9.6V with 1900mmAh guarantee capacity, so it translates to another 11+ hours, more than a night worth of observation.

Friday, March 02, 2012

2012-03-02 Very brief sunny period

The sun finally comes out with poor seeing.  Thin cloud floating around and the high humidity is no fun at all.  When I pulled out the solar filter after observation, I can see a thin layer of moisture on the corrector of my Maksutov.

Despite the poor weather, I really want to try out my Maksutov with Baader 3.8, centering the target is not too hard and I managed to do it even at 3000mm and focusing is okay as well even without using a motor.

This is taken at prime focus, i.e. 1500mm focal length at around f/11.  Given a green filter, shutter speed keeps fast and it's good to freeze seeing.  I've also tried to do at 3000mm but then the seeing was just too bad to give any detail, even accurate focusing is impossible.  I shall try again whenever I have chance, see if I can get something with white light.