Thursday, April 30, 2015

A large piece of glass!

70mm refractor on the left and 300mm f2.8 lens on the right... as an amateur astronomer, we all love aperture!

My very first autoguiding exercise

The Sky Adventurer has only single axis guiding, so it would require good polar alignment to guide successfully... of course, it's rather hard to do indoor.

Finding a bright enough star is not easy too... but I managed to get one.  The polar alignment was rather off despite the target star stayed in the field for quite long, and that indicates not too bad polar alignment.  However, it did drift away slowly and PHD guiding was complaining.

Cloud moved in before I could try EQ Align to fine tune the polar alignment.

Now at least I know that my ASI 130mc and the ST4 port of my Sky Adventurer works, I will need a better night to try the whole thing again.

A small DEC motor was on order, together with some electronics, and I will try to make my Sky Adventurer with dual axis motor/guiding.  Not very confident, but why not have a try?


For dual axis guiding, the guide scope and the imaging scope  should be on the same side of the L adapter, so the balancing side should carry something heavy as well... is that making the whole thing meaningless in that case?  The Sky Adventurer is wide field and portable!

I guess I will be taking a 200mm lens for my trip, so the polar scope should be enough and no need of guiding.  So, I will be bring a 50mm lens, a 200mm lens plus a 2x tele extender and that's all.  The 300mm f2.8 will be left at home.


To test the concept of using camera lenses as guide scope, I found that I have to insert a 2x barlows in order to reach focus with a camera lens.  It's good in the sense that, the guiding lens is always working at higher power!  Suppose I have two lenses, 200mm and 300mm respectively.  If I use the 200mm as imaging scope and the 300mm as guide scope, the guide scope will be working at 600mm due to the barlows.  Even if I swap their role, the 300mm as imaging scope and the 200mm as the guider, but then the guiding side will still have 400mm focal length!

Wednesday, April 29, 2015

Sky Adventurer dual axis guiding

The Sky Adventurer features a ST4 style guiding port which allows RA guiding, but that also means it only correct PEC.  The DEC part is manual driven only, so we couldn't guide in a dual axis way.

Motorizing the DEC part is the first step, here we have two approaches:

The one on the left is to use an inline shaft coupler, I got one at home which matches quite nicely.  Problem is that, the motor would make the whole thing much more bulky.  The next method is the one on the right, it uses two gears, one on the original manual control knob and another one on the motor, but I got only one such gear ready at home.  I will need to buy one more and the motor could be placed below the DEC body, I will want a smaller motor in that case, and I will also need to find a way to mount the body and mesh the gear correctly.

The following wiring scheme could be used:

Guider -> 
ST4 port of my own, getting the DEC signal to drive the motor -> 
ST4 port of the Sky Adventurer

So no need to modify the Sky Adventurer, just add a "relay box" and steal the unused DEC signal.  A simple geared motor controller could be used to drive the DEC.  Too good to be true?  Best of both worlds?  Let's see... I shall start hunting for suitable parts.  We need gear with 6mm shaft bore.

Further downsizing: Skywatcher Sky Adventurer

This is a huge move again.

My GOTO Mark-X is very portable but yet, it requires a "heavy" 410 geared head, and it is rather heavy and bulky as well.  So here I go for an even smaller mount.  This mount should be able to do astrophotography and it should be able to let me use my C5 visually or for planet imaging.

First of all, the tripod that I'm going to use is a Velbon mini-white.  It is ultra-portable as you can see from the above picture on the right.  It can even sneak within a lens compartment of my Fastpack 350!  Next is the Sky Adventurer, the mount body could be hidden in a lens compartment of my Fastpack, too!  The polar wedge is lighter and easier to use than the 410 geared head, and again, could be fitted into a lens compartment.

This is what I have fitted within the lower padded compartment of my Fastpack 350 as shown above:

Upper left: Canon 50mm f1.8, plus a ASI 120mc for guiding.

Lower left: Skywatcher main body which is a self contained mount with hand controller and battery compartment, polarscope!  It even features an ST4 style guider port!

Upper middle: a Velbon mini white tripod, frankly, it's even more miraculous than the Sky Adventurer and they are also a perfect fit.

Upper right: polar wedge for the Skywatcher

Lower right: a Canon 200mm f2.8L

Also a Canon 70D with a 8mm fisheye lens

What's left is a L adapter containing also the DEC body on the upper compartment, and the notebook computer in its own compartment.  Too good to be true, right?  A simple backpack containing all the lenses, tracking mount with guiding, guider and camera!

The picture on the right is the testing setup.  It takes a Ranger without any problem and I would say a C5 is easy for this small guy with proper balancing on the other side of the L adapter.

Monday, April 27, 2015

20150427 Sun

Heard that there's a long filament these days, and I got time at home, so why not?

First up is a prime focus shot stitched from two shots at 1431 and 1432 respectively.

Then we have 3x shots:

1434 (GMT+8), this one is aimed at taking the filament and prominence in a single shot, but it's too big to fit into the field of my Lumenera Lu070M.

AR2327 and AR2311, taken at 1437 (GMT+8):-

An exposure aimed at the prominence, and it shows more detail than the 1434 shot.

An exposure aimed at the filament, and it shows more detail the 1434 shot as well.

Enjoyable short session.

Friday, April 24, 2015

Dedicated Guidescope?

I am thinking about the need of a guidescope which is important for astrophotography.

However, if you're going to bring several camera lens for different focal length, we might actually use them to guide each others.  For example, if you're going to bring a 200mm f2.8 and a 300mm f2.8, they might be able to serve as the guidescope of the counterpart with suitable adapters.

In case the focal lengths are quite different, say 100mm and a 300mm, a tele-extender might be added to make them close.  We know that the guiding accuracy might suffer if you use shorter focal length to guide longer, but that's what you have to live with when we want absolute simplicity.

Remember the good old days, my friend used a FS60C and Sky90 in that way with great success.

Conclusion is that, for relatively wide field imaging, and I know that 300mm is pushing the limit, we might not need a dedicated Guidescope.

Tuesday, April 21, 2015

Selling my GOTO Mark-X

It's a very great mount, high capacity, compact, precise, and the most important thing is that, it's a working piece of history, a collector's item.

But still, I'm moving to lighter weight stuff.  So here we go, if you're lucky enough to see this, feel free to make an offer to me.  I have a reserve price in mind, but why not just offer and ask?

Here is a few pictures of the mount.  First of all, the controller and the motor is not original, but from Carton which is the OEM of the discontinued Tele Vue System Mount.  The speed of the motor could be fine tuned by turning a small knob inside the hand paddle.  It supports both northern and southern operation, and it has stop and 2x mode.

On the back of the paddle, there is a detachable battery pack of two 18650 Lithium batteries.   A set of two will last for many observation sessions.  The battery pack could be attached to the back of the hand paddle neatly as shown.

So, it could be removed any time.

The black motor mounted on the Mark-X.

A U-adapter was mounted securely on the Mark-X, with one side with a worm geared driven DEC slow motion control block and GP style dovetail saddle, the other side was a 3/8" screw which allows attachment of a ball head, I will throw in a good ball head if the offer is good enough.

Another view of the mount, the mount body is very new indeed.

Finally, everything could be packed in a small padded camera bag which is included in this deal.

Thank you for looking, and waiting for any reasonable offer.  If there is no offer within a week or so, I will put it on local astronomy forums.

Sunday, April 19, 2015

The Quest of a 4" refractor/astrograph: experiment and fine tuning (Canon FD 300mm f2.8)

As an amateur astronomer, I have several Canon EF adapters lying around. I found this one to be perfect for such purpose, since there are three fixing screws so that you can turn the M42 thread again the EF mount!

So the orientation of the lens could be fixed easily!   Note the pencil mark I made above in order to find out the best orientation.


Tonight, I have conducted photographic and visual test.

Visually, it's sharp at low magnifications.  I have used a diagonal by placing a 2x barlows lens in front of it, serving as a relay lens.  It could reach focus without problem.  Pushing the power will result in softening, unacceptable I would say, and it looks like internal reflection due to the extra lens elements on the rear part.  My primary impression is that, this is not a good visual telescope, and it is not going to replace my C5 therefore.

Photographically, it's great.  It's very sharp and free of any color fringes.  On pushing it with a Kenko 2x, I found that it will produce error, but of course, if I use a M42-EOS adapter with built-in chip, the error will go away, and I will have focus confirm signal too.  So, I will need to buy myself a rotatable M42-EOS adapter with built-in chip, and then the project will probably close.

Conclusion: this is a very nice camera lens, but not exactly a great telescope.  I found that my 200mm f2.8L suffers from the same problem, while the Canon 100-400mm is a great telescope, however.  Faster lens is not really good candidate for visual purpose at high power.

Saturday, April 18, 2015

The Quest of a 4" refractor/astrograph: implementaton (Canon FD 300mm f2.8)

After removing that three little screws, it's still pretty hard to remove the rear part... but then I've a tool which was used when I was disassembling my PST before!  With it, it could be done rather easily!

Rear assembly removed cleanly:

The 77mm P0.75 male thread was left:

I'm getting excited!  With the M77-M58, M58-M42, M42-EOS adapters in place, we have the following compact 4" refractor with 300mm focal length!

The amount of 77mm thread is enough, on the contrary of my previous imagination!  Next, the flange distance is correctly made for EOS with a single extension tube.  This becomes a very fast f/2.8 compact refractor!  Unluckily, when all the adapters were screwed together, the orientation of the built-in tripod socket was in a bad position, I have to find a solution for that.

The above configuation allows infinity focus without any problem!  The built-in focuser is butter smooth despite it is a very aged lens.  Canon L series is really really serious!

To switch it into visual configuration, the extension tube should be removed, and a EOS-1.25" adapter is used.  Unluckily, the amount of optical path length is insufficient for a star diagonal.  The following picture shows how I could reach infinity focus with an eyepiece.

This is a 300mm wide field refractor, with my 20mm widescan, it yields 15x with 5.3+ degree field of view, very sharp and respectable!

To use a star diagonal, I must insert a 2x barlows in front of the diagonal, so it becomes a 900mm focal length telescope.  The exact focal length must be measured.  I must try to use it for planet imaging soon, and if it's good enough, I shall sell my C5.

Keywords: Canon FD 300mm f2.8 conversion EOS digital EF mount astrograph telescope flange distance eyepiece M42

Friday, April 17, 2015

The Quest of a 4" refractor/astrograph

This is a progress report of the following:

The FD 300mm f/2.8 is still being delivered by Hong Kong Post, way slower than anticipated and it's abnormal.  Other parts arrived.

The first one is the most critical, ordered new.  It's a M42-EOS adapter with chip which allows focus detection.  The FD 300mm f/2.8 should have 77mm thread upon removing the rear aperture control part, so a 42-58mm adapter was sandwiched between the M42-EOS and a 58-77mm stepping ring.  It's rather compact and strong enough as shown below:

However, as expected, the amount of 77mm thread is a bit little since it's originally designed for filter, but now it's going to hold a lens-camera combination.

In order to create the proper flange distance, a 3-piece extension tube will be used to connect to a camera.  The FD 300mm f/2.8 will then become an astrograph or for regular imaging.  In case the combination could not meet the flange distance, an adjustable M42 tube should be ordered.

To be used in visual mode, the extension tubes would be removed, and instead, a 1.25" barrel adapter will be used, plus a diagonal which should probably make up the optical path length to allow infinity focus.

Of course, the combination above might be a bit optimistic, and might require some more fine tuning, like adding extensions.

You know, I am getting excited.  A poor man's portable astrograph and wide field 4" refractor all in one!  Even an expensive new EF 300mm f/2.8 will not be able to serve in that visual configuration without a 2x barlows as a relay lens!  Best of both worlds.

Thursday, April 16, 2015

20150416 Sun

I only got around half an hour to go before I need to go to work.

Prime focus shot at 1315 (GMT+8):-


Two frames mosaic 1318, 1319 (GMT+8), AR2321, 2324 and 2325 taken with 3x barlows..


I just found that the 3x barlows is nearly parfocal with the Lumenera!  So, I'm going to use it very often.


At the same night, I tried to pack my C5 and go Jupiter imaging.  The new bag is rather large but it's too heavy as a shoulder bag.

The worst thing was, I left my Lumenera at home!  So, I went home empty handed.

Monday, April 13, 2015

Camera lenses

First up is a Canon 24-105mm f/4L, this is a very decent lens for daily purpose. I had been considering the 24-70mm f4L before, but given up since I prefer longer focal length than the macro capability. For macro, we really want a separate lens.

While the above is a general purpose, this is a special purpose lens.  It is a 8mm f3.5 fisheye, good for selfie and extremely wide field imaging.  Good for star field as well, and in that case, I usually stop it down to f5.6.  This is a fully manual lens, and the infinity marking is rather accurate.

This is my all time favorite.  I had sold one before but I soon got another one back.  This is good for general photography, birding and it could be used as a portable telescope, too!  I use it for butterfly imaging, feels like a poor man's macro lens.

This is the newer STM kit lens.  I love it indeed!  The old non-STM version was way worse, this model comes with a decent focus ring, and the image quality is noticeably higher.  If I were not longing for the wider range of the 24-105mm, I would use this one all the time!  The focusing motor is nearly as fast as USM, but it's total silent for movie recording.

This is not exactly a lens but a 2x tele-extender.  I would use it for really close up with the 100-400mm above.  We will still have autofocus with Live-View mode.  This is originally bought to be used with my 200mm f2.8L, for my total solar eclipse trip.

A poor man's prime lens 50mm f1.8, it is very high quality actually.  I never wanted a 50mm f1.4 indeed.  When stopped down to f2.8, it is great for astrophotography, too!

This is my astrophotographic lens, it's good for indoor imaging events as well.

Testing the velbon mini white

It's really small and compact!

The color matches the U-adapter and the DEC slow motion block too!  I keep the smallest leg retracted, it's very stable.  At least on par with my Gitzo G106.

The bad thing is that, with a 3/8" to 1/4" adapter, the screw did not flush all the way in, and the gap is creating some shake.

 Adding a washer should fix most of the problem, however.

20150413 Sun

This is a very bad one, I dare not even to process it.  The sun was in a weird angle even as early as 14:00... so I missed the boat.

AR2321, taken at prime focus:

most of the objective blocked by the window frame and partially through the dirty ugly window glass... so the image was so poor... anyway, just a record.

Thursday, April 09, 2015

The quest for portable tripod

I never use those tripod specially geared for astronomy, except a few sets of wooden legs bundled with those equatorial mount.  I soon switched to camera tripods with tailor made adapters in order to maximize the portability.

Gitzo G1415 has been my heavy duty work horse.  It has been used with my APM Giro mount, and also Meade LXD55 and maybe a couple of other heavier duty mounts.  But then when I began to switch to absolute portable stuff, I go back to my Gitzo G106 for all the time.

Gitzo G106 is extremely small.  When the first time I met it in the shop, I could not fall into sleep that night and I go to the shop to buy it on the next day.  It supports my C5 well enough, even with a Nexstar SE mount.  It supports my GOTO Mark-X very well too!  It has been with my to solar eclipse trip, and also some traveling with my family.

However, it could be still quite big that I have to carry it with my hands.  It couldn't easily stow inside my backpack.  Until recently Velbon comes out with a mini white:

Crazy indeed, right?  I placed my regular sized mouse for comparison!  It's rated at 6kg capacity, just like my Gitzo G106, but it's way shorter and quite lighter!  The best thing is that, it's in the size of a camera lens and thus it could be placed inside a bag!

It's a bit cheaper than my G106 about twenty years ago.  The tripod head interface is 1/4" instead of 3/16" but then conversion screws are easy to find.

I couldn't wait to put it side by side with my G106 tonight.  I still believe the G106 is a bit stronger, but for absolute portability, this is going to be with me in the time to come!


I got home and couldn't wait to compare them side by side.  The tiny Gitzo G106 is a big boy in front of the Mini White!   Something like half of the height.

However, when fully extended (without the central column), they're pretty close in height.  The Gitzo has its traditional twist lock which is very effective and durable, however, it could be pretty slow to get all the legs fully extended, as you will need to do it one by one.   On the contrary, the Velbon twist lock action is very quick and easy, you can turn a leg until all the sections disengage, and then you can pull it all out, and turn on the opposite direction to get it fully locked.

However, such a locking mechanism has a price to pay, see the following picture.

There are quite a lot of plastic there, I doubt how long it would last.  The Gitzo, however, has brass locking rings and it's still kicking after like twenty years of services.

Anyway, the Mini White is still attractive, due to its size and weight.  To close this little preliminary impression article, I placed it side by side with my Canon 100-400mm... you see how small it is!

I won't hesitate to bring it out every time when I wanted to take photographs! 

Like a telescope, the one which got used the most is the best telescope.  This is going to be the best tripod as it's going to be used as much as it could be!

Tuesday, April 07, 2015

Partial lunar eclipse on 20150404

I am not trying to join the debate to see if it's a real total lunar eclipse or was it partial.  I'm impartial since I missed the moment of "totality" anyway.

I was away from my home city and I was observing in a remote rural area where there's a small but close enough hill to block all my view during the best moments.

This is what I got when I left that place before going into my hotel room:

I have a friend around who's a novice photographer, I borrowed her my lens and she was amazed to be able to take image of the partially eclipsed moon!

On the same night, I observed Jupiter with my Canon 100-400mm plus a 20mm eyepiece and a 2x barlows lens working at 3x as a relay lens so that I could use a star diagonal.