Wednesday, December 30, 2009

Helping focus.. Bahtinov Mask

In my long line of posting fun stuff that helps make my astro-life easier... I decided to write a short one on gaining perfect focus quickly and easily. While performing focus with an eyepiece, you can normally get pretty decent focus by taking a little bit of time and moving the eyepiece back and forth. In all likelihood you can get a pretty good focus (at least good enough for your viewing pleasure) just by moving in and out of focus, perhaps pretending your at the optometrist and chanting 'how about now' or 'this one or this one' :-) until the image looks good.

When attempting to take photos however, this becomes a bit more problematic as the camera and associated photos are generally less tolerant of less_than_perfect focus, this becomes more apparent with longer exposure times. It is also more difficult and time consuming gaining focus when you are using a camera (either prime focus or via a computer) as you need multiple exposures to test the focus, this takes a very long time to get perfect for your next frame-able photo of M42. One evening I spent almost 40 minutes moving my focuser back and forth trying to gain perfect focus. :-( Spending this much time on focusing, takes valuable time away from capturing those photons on your image sensor... not a great use of time.

While looking for focusers (dual speed Crayford types), I ran into some sites that discussed products they made to make focusing easier ( / Astrozap). I decided to give one a try, selecting the astrozap version.

I ordered it from Astronomics and received it a couple of days later, on a cloud-less evening no less! So I took it right out and placed it on my CPC, hooked up my CCD camera and gave it a run.

In less than 3 minutes (after alignment) I had the selected star in perfect focus! My shots came out just as planned and even better than expected. The more you use the mask, the faster your focusing becomes (as with all things, the more you practice something, the more efficient you become).

You can find more detail about how these things work, but I will supply a brief overview here:
The mask creates diffraction spikes (like an astrograph, but instead of 4 spikes you will see 6) that can be used to dial in your focus.
If the spikes are not perfectly aligned, then the star is out of focus.. but when aligned you will have a perfectly round star. If you have a dual focuser, it will be easier to put the diffraction spikes in perfect alignment, if you do not, it will still get you right on the 'money' it just might take a few seconds longer.

This turned out to be a pretty good purchase overall, as it reduced my focusing time from 40+ minutes to less than 2 minutes. You can go to to see how they work, at less than 100 dollars (USD) it is probably the least expensive
accessory I own but one that saves me quite a bit of time (and time is money right?).

Happy Photon Hunting!

[note: I am not getting paid by astrozap or any other vendor for publishing my views here]

Saturday, October 17, 2009

SCT collimation tool: 'collimation helper'

Collimation of a Schmidt-Cassegrain telescope (SCT) is no simple task... good news is, doesn't need to be done too often. ;-)

One thing I struggle with continually in my infrequent collimation attempts is understanding the direction that I need to adjust in order to make the correct movements of the secondary mirror.
Articles on SCT collimation say to look into your eyepiece and reach around the front of your telescope putting your index finger near the front of your telescope pointing towards the center. While a great (and easy) thing to describe, this is a very difficult thing to do, especially if your telescope is wedge mounted.
The distance from your eyepiece to the front of a wedge mounted telescope (alt-az is much easier as it is a shorter distance) is pretty far making it pretty much out of reach unless you have some pretty long arms. ;-)

So thinking about this more, I wondered what I could do to mimic the pointing characteristics needed during collimation, without reaching around to the front of the scope with my hand.
Here were the characteristics I considered:
- stability (it needed to stay put in one place until I removed it)
- mobility (it needed be able to be put on and removed as necessary)
- size and weight matters (needed to be something I could put in pocket or toolkit)
it also needed to reasonably perform the function necessary, meaning that it should obstruct enough light to mimic a finger but not enough that it takes away from the collimation efforts.

I decided to try out a very simple mechanism to do this, choosing an ice cream stick *, an 'alligator clip' and a wood screw**. I also decided to use epoxy to bind the stick / 'alligator clip'.

Now, when I use the 'collimation helper' I clip it on to the band surrounding the front of the telescope, pointing towards one of the three collimation screws. This then gives me an awesome point of reference when adjusting the screws to collimate the scope and takes the guess out of the direction of movement necessary in perfect collimation. Now my collimation attempts are easier and faster with less frustration due to incorrect directional movement.

This is a representation of what to expect when peering through your eyepiece while collimating your telescope using this device, the straight line emanating from the outer circle is the 'collimation helper'.

Next step will be to paint it, probably flat black but that is only cosmetic, it is really unnecessary as it will work just fine without any paint.

* any ice cream stick should work, I chose a thicker one to ensure I had a decent obstruction.
** any type of screw should do, as long as it fits snugly within the 'alligator clip'

Update: Never bothered to color the instrument, worked as expected even without coloring. Choosing a fatter stick worked well as it enabled me to really see it in the focal picture. One modification that I did and would highly suggest is making the end (toward the center of the view) pointed, I worked out what the center should be and then employed my 'dremel tool' on it to give it a pointed end, leaving the rest of the contour in place, this minor adjustment gave me something to focus on and assisted in making the final adjustments.

Happy Photon Hunting!

Friday, October 2, 2009

Dual Speed Focuser

This post covers the use of an external focuser to increase the granularity / speed of focusing your telescope.

In attempting to gain fine focus on my Celestron CPC, I found the primary focus knob insufficient for fine grained or quick focus of the telescope. So what does the primary focus knob do? Well it focuses the telescope, more specifically, the primary focus knob moves the primary mirror back and forth to focus an image in your eyepiece or camera (as the case may be). This mechanical movement of the mirror *may* be prone to many irregularities that make focusing your telescope challenging, like image shift (eg: movement in mirror causing the movement of an object in the Field of View [FOV]).

In addition to the potential movement (shift) of the mirror I was also unhappy with the amount of time it would take to gain focus on objects, even when using a bahtinov mask, where the 'sloppiness' associated with the original focuser led to lots of back and forth movement attempting to focus the object. (I will cover the use of a bahtinov mask in a future blog as it is a nifty tool to have in your toolbox). While looking for ways to combat the above, I started to look into 'crayford' style focusers as they took the movement out of the primary mirror, making focusing faster and more fine grained by moving the eyepieces or 'image train'.

I found a couple of different options and finally settled on a dual-speed focuser from William Optics, ordering it online directly from the company as opposed to one of it's distributors.

A few weeks later my new focuser came via the US Postal service, tightly wrapped and sufficiently encased in bubble wrap. The very first thing I noticed about this focuser was the weight, it came in at just under 2 lbs!
It was very well constructed, with a very smooth focal range (about 2 inches of travel). The small focus knob made getting precise focus super-simple, while the larger focus ring made for very quick focus.

My original telescope focusing routine, had me centering an object in my FOV, then using the primary focuser to move the primary mirror forward and backward until the object was close to focus, then I would move the primary mirror into a more solid position by turning the primary focus knob counter-clockwise to place the mirror in a more stable position. This was normally repeated at least 3-4 times as I would inadvertently 'pass' the optimal focus and have to perform a 'do-over' until I stopped the mirror at a perfect position.

Now the focus routine is far easier and faster to perform, here are the steps I take:
1) center the object in my FOV
2) perform a rough focus using the primary focus knob on the telescope, making sure to make the final movement counter-clockwise to steady the primary mirror
3) perform a second level focus with the larger focus knob on the focuser, getting the object to close focus
4) performed the final focus with the smaller focus knob on the focuser, putting the object in perfect focus

My focus routines now take less than half the time to obtain a perfect pinpoint focus and offer an easier and less frustrating time, giving me more time to stargaze and less time in set-up mode.

Just a note to say that both of my dual-speed focusers are very well constructed, I purchased the William Optics focuser after-market for my CPC, but the focuser that came stock on my Astro-Tech AT66ED finderscope is also well constructed and silky smooth. It doesn't matter what type of viewing you do, if you don't have one already a dual-speed focuser would be a very good investment, making the pinpoint focusing of objects a breeze.

Happy photon hunting!

Sunday, September 27, 2009

Balancing Act

This post covers some tips, tricks and observations on scope balancing.

Of the several things you need to do to properly align your telescope, I previously posted about balancing via the use of a leveling system... this one covers another important aspect; balancing your telescope.

When you pull the scope out of the box and use *only* the accessories provided in the box, which may include the scope, tripod, small star diagonal, small finder-scope and maybe one eyepiece, it is likely that all the equipment will balance fairly well. When you start adding new accessories like I have, you will start to see that the scope will become unbalanced and heavier in either the 'front' or 'rear' ends of the scope. Additionally, you may find that now your scope is heavier on one side or the other, but that is for a different post, this one only covers the front / rear balance issues.

So now you have an interesting challenge, you need to add weight to either the front / rear of the scope to balance it out. You do have some options, I chose to head to to see what counterweight options they had available. Looking at their storefront I saw the following options:
--> top weight set
--> bottom weight set
--> complete weight set

Then I was faced with the inevitable question, what should I order? Without any documentation to guide me to a decision, I opted for the complete weight set.. I couldn't possibly go wrong there! (famous last words)

So in comes my order, I read the instructions and placed them on my scope.. now to do my balancing act.
I immediately installed the top weight (only 1 to start) and the bottom rail (with 1 disc). I was able to almost immediately balance vertically by moving the bottom rail to a rearward position (see image below).

Notice the weight on top as well as the position of the weight disc on the bottom rail, this position allowed me to get a perfect balance vertically, but unfortunately not horizontally. So I would reposition the weights horizontally to get balance and it would negate my vertical balance, leaving the scope unbalanced in the vertical position again... just when this looked so simple... ;-)

I ended up taking off the upper / lower weights and observed the scope balance more carefully. The scope was pretty heavy in the rearward upper position, placing a weight on top made horizontal balance easy, but didn't help the vertical balance at all. So noting the above, I decided to not put a counterweight on the top at all and instead move the bottom counterweight into a more forward position.

Moving the bottom counterweight back and forth, I was eventually able to find the sweetspot for both vertical and horizontal balance.

Now my scope is perfectly balanced in both the vertical as well as horizontal positions!

One other thing that I had to work on for the balance was the position / distribution of the weights on the bottom rail not only for balance but also to ensure that I could clear the CPC base with the bottom counterweight. I was able to find and mark the position appropriate to this particular visual setup.
As I use some other accessories like cameras, etc.. I had to additionally put other marks on the bottom rail so I could know where exact balance was for these other configurations (eg: imaging).

Of note: In retrospect, now knowing my scopes balance points, I would have probably just ordered the bottom rail and weight set, saving myself $79.00 (plus shipping / tax). Of course your mileage and setup may vary... understanding your setup and observing your specific balance variables on your setup, will lead you to select the right product for you.

Happy (Photon) Hunting!

Saturday, September 26, 2009

Scope Port Protection: Homebrew

I have heard some horror stories about scopes electronics being fried by dew getting into the external ports on the CPC (eg: aux, PC, etc). This is probably a real issue as you have contacts inside those ports that do carry electricity, dew build-up *could* lead to the possibility of shorting those contacts, leading to (guess what) a fried CPC motherboard.

Hadn't happened to me yet, but I convinced myself that it *could* happen to me and so off I embarked on a small project: to find a cheap and easy way to cover those exposed ports!

So looking at the options here:
You could surf to, where you will find molded 'dust covers' @ .69 cents each + shipping of $4.49 (total $5.18 for one RJ-45 cover, not even adding the RJ-11 dust covers to the equation)
You could go to your local Radio Shack (now called 'The Shack") and pick up 3 RJ-11 connectors and 1 RJ-45 connector, 4 small finishing nails, glue or epoxy and some leftover black paint (paint is optional) and make yourself some nifty plugs for only about $2.00 (save yourself $3.18++, get it done in one day and have the fun of building homebrew... priceless!)

*** Note: I have some basic tools (eg: crimper for connectors) so this option may not be for everyone as you do have to crimp the empty connector to get it to fit into CPC ports. ***

Here is what I did:
- Buy supplies (above incl; 1 rj-45 connector and 3 rj-11 connectors)
- Crimp the connectors to fit into CPC ports
- Pushed finishing nails into the rear of connector (where wires normally go), just enough to hold in place, you should not push them too far in as you don't want them to come in contact with the connector contacts.
- Applied epoxy to nail / rear of connector to hold in place (of note: I oriented the nail such that it pointed downwards or away from the tab on the connectors, time will tell if an upwards or downwards orientation is best, will update blog accordingly)
- Let epoxy set for 2 hours per the instructions
- Painted the units, let them dry for a couple of hours..
- Insert into CPC ports and walk away

Now should you need to unplug covers and plug in a device, just grab the nail and push in the tab, you will be good to go.

As the retail dust covers make no promises about being water-tight or any such thing, this option *should* be at least as good as the dust covers.
I take no responsibility for your scopes *protection* from dew or any other problem that arises from using this method of plugging your CPC external ports.

Thursday, September 24, 2009

Telescope levelers (part III)

This is the final post (perhaps) on the telescope levelers... so about now after two other posts on the leveler quality as well as installation methods, I am now at the point to comment on the use of the levelers.

On average it took me about 10 - 15 minutes of lower tripod leg adjustment to get my scope to level and even then on many occasions the level wasn't 'dead-on' but as close as I could get it without messing around with it for another 10 minutes or so.

Now in comes the TPIastro telescope leveler... it took me all of 2.5 minutes to get a PERFECT level, a really 'DEAD-ON' level. No lifting, pulling, pushing or any hard labor, merely turning the handles and watching the movement on the bubble-level. I could have never imagined an easier way to level my scope.

I can take that 7.5+ minutes and use it towards gaining 'dead-center' on my star alignments!

Awesome job on the levelers TPIastro!

I would highly recommend these levelers to anyone requiring perfect level!

Telescope levelers (part II)

In the previous post I spoke about the new telescope levelers from in terms of fit / finish. This post will cover the installation of the levelers on the Celestron HD Tripod.

Ok, so I unwrapped the Telescope levelers and took down my telescope to start the install process. The Celestron HD Tripod is a pretty stable device overall, pretty solid and heavy. Here is what I did to install the levelers:
1) Removed my telescope from the tripod
2) Removed the telescope wedge from the tripod (to make the tripod easier to maneuver)

Now here is where the decision point comes in... in order to install the levelers, you need to first remove the existing tripod extension legs... there are two ways to do this (that I am aware of) one of the options is easier than the other, but in some ways perhaps not optimal.

Methods of removal:
a) Unscrew each tripod leg from the tripod 'head' and extension leg will come (fall) out of the top of the upper leg.
b) Release clamp on extension leg and pull briskly until the internal guide pops off, leaving a part inside the tripod upper leg.

Method (a) is more difficult and time consuming but it is the method I chose. Why did I choose that method? Great question!
I opted for method (a) as it offers me an easy way to get back to 'stock configuration' in case I ever decide to sell my CPC and HD Tripod. Method (b) leaves parts inside the tripod, which *may* lower the selling price of the unit.

Ok, so method (a) it is:
1) remove the locknuts and bolts from the tripod head, releasing the legs from the head
2) there are some small screws that hold the upper leg tube assembly to the tube head connector (get a piece of tape and put the screws on the tape to ensure they don't get lost)
3) tap off the tube head connector with a rubber mallet (it is wedged in pretty good)
4) tap off the 'ground spike' at the bottom of the lower extension tube, the rubber mallet is good here too.
5) Once the head connector and 'ground spike' is removed, you can release the lower extension leg clamp and invert the tripod upper tube, the lower extension leg should fall right out of the tube.

So now the old lower extension leg is out of the tripod, next comes the easy part. Take the new leveler and insert it into the bottom of the upper tube, closing the clamp to restrict the movement of the leveler. Place the tube head connector on the upper leg tube, insert the screws that connect these parts. Next replace the head tube connector and head connection, using the head screw and bolt to secure the connection.

Super simple! You have now successfully installed the new levelers!

Next post will cover the acquisition of perfect level and differences in time to acquire level with the new equipment.

Until then, happy photon hunting!

Wednesday, September 23, 2009

Telescope Levelers

If you are into astronomy and more specifically astro-photography, you will eventually run into many 'learning opportunities' that need to be overcome in order to capture that great shot of .

One of these 'opportunities' is leveling the telescope, this of course is no easy matter.
Let me give you an example: I have about 100 lbs sitting on my tripod legs, this makes upwards and downwards adjustments on the individual legs very difficult and obtaining a perfectly level telescope nearly impossible for one person to acquire.

In comes Telescope Performance Industries to answer all of my leveling needs! I spoke with Dave Y at about their levelers and how they could make my telescope leveling duties much easier and more accurate. Dave told me about his manufacturing process, materials used and sent me the documentation as well as some photos so I could see his work in action.
I immediately liked what I saw, in fact I thought to myself if they were half as well constructed as they appeared in the photo, these would be very solid levelers and make it 'super-simple' to dial in my telescope.

Dave shipped me a set to mount on my telescope, along with stellar documentation and packing that would have made a mummy jealous. When I opened the box and packing materials (probably spent the majority of the time unwrapping the bubble wrap!), I saw a sight to behold! The levelers were even better quality than they appeared in the photos / documentation, worth every penny just on look and feel alone.

Next blog, mounting the levelers on my tripod and putting them to use...