Further experience with the FSQ-85

I have had the scope for three weeks now and have used it three times. That's good going in the UK in case you possibly thought that's bad; its not uncommon to wait for six weeks for a first light in our cloudy climate!  Anyway, leaving aside the usual British moans about our weather......

The FSQ is so easy to use.  Just point it, focus and forget.  I am using Baader LRGB filters.  These ones in 1.25" version in an Atik EFW2 filter wheel.  These filters are stated to be parfocal.  However, with my Skywatcher ED80 telescope I found they were not.  The focus wandered slightly between the filters.  I normally focus on the Luminance channel first.  I then grab LRGB in that order.  But by the time I got to the blue filter I found stars were becoming bloated, not massively - but enough to take the edge off the picture.  This problem is definitely not an issue with the ED80 stock focuser - I could adjust that sufficiently to make it rock solid -  but is more attributed to the differing light wavelengths coming to a minutely different focus with the ED80 primary objective, blue is always affected worse.  This is hardly surprising at the ED80 price point and indeed, the ED80 is an excellent telescope for its price.  When using the FSQ though the focus is perfect on all LRGB filters and is as perfect on all four corners of the image.  It just makes the scope so easy to use.  I sincerely hope this is also the case when I get some Baader narrowband filters as well.  However. considering the FSQ is ten times the cost of the ED80 is it ten times better?  Of course not.  That is not the way of things - it is diminishing returns at this end of the market as is the case with any other premium product.  You pay a massive amount more to make it 20% better.

The FSQ-85 focuser is heavy and robust.  However, a slight word of caution here that knocks a mark off the score for the FSQ-85.  I have found that with my filter wheel and camera attached (EFW2+Atik460 = just over 1kg so hardly that heavy) I find that I need to have some focus knob lock applied or else the focuser can start to very slowly slip when pointed at over 50 degrees or so above the horizon.  This came as a bit of a surprise to me since I have read some web articles that state the focus lock can be fully undone and the focuser does not slip even when pointed vertically.  This is not my finding; I need some focuser lock applied to "brake" the slip and can then use the fine focuser.  That makes me give the scope 9/10.  Otherwise it would have got a perfect 10/10.  I penalise it a full mark since the focuser action is a critical part of using a scope and at this price point I should not be expected to start shelling out yet more money for after market focusers or fiddling with tightening screws etc.  This is a Rolls-Royce scope; you don't buy a Roller and expect to be under the hood tinkering on day 1.  I need to do some further research into this.  Maybe the focuser can be "tightened" perhaps..... Or maybe my expectations are unrealistic and this is the whole point of having the focus lock.  To be fair the use of the lock screw is pretty intuitive and easy.  Had it not been I would have sent the scope back.

What is very commendable about the FSQ is the accuracy of the Camera Angle adjuster and focuser working together.  So, when I achieve precise focus and then need to turn the CAA to frame the subject (something that I will be doing all the time) the focus does not shift even a fraction.  I checked it out by slewing the scope to a bright star and putting on the Bahtinov mask after so adjusting the CAA after previous focus - the focus had not moved at all.  That shows how accurately the scope and its bits are made.

I have used the FSQ on two objects so far, in both cases at native focal length - I have yet to use it with the reducer even though I bought the reducer with the scope.  I grabbed further data on M33 Triangulum galaxy to add to the image on my previous post and I also grabbed RGB on the Double Cluster.

This image of M33 in Triangulum (lower quality here as a jpeg) has two hours of Luminance and 90 minutes each of RGB. The Luminance was 1x1 binned and the RGB was 2x2.  The data was captured on the evenings of 21 and 25 November 2013 from my back yard (semi light polluted).  I also should really have been using my IDAS Hutech Light pollution filter! All processing was in Pixinsight.  The image needs more data to really let the spiral arms and the HII regions jump out.  It could use some Ha as well.  Nevertheless, it is coming along nicely I think.  The two data sets are closely aligned and that will allow me to grab a whole lot more data.  Next time it is clear I will grab a lot more luminance and Red data.  Indeed,  I might push the subs out to 15 minutes.  What stops me doing that normally is that Nottingham is under the flight path for US West Coast flights from Heathrow that tend to plague my exposures!  It hurts throwing away otherwise perfect 15 minute subs!  However, I have recently discovered that Pixinsight's Windsorised Sigma clipping routines are extremely effective at removing plane and satellite trails, especially if I use dithering during capture.

The important thing to note is the stars are nice and round in the corners so the scope is performing very well!  You can see this image at higher resolution here.

Next up is the Double Cluster in Perseus.  This data was captured on 4th December 2013, again from my back yard.  This time though I used the IDAS LP filter and this has reduced light pollution light splatter very effectively.

Star field pictures show errors in an optical system all too readily and I am very pleased the Tak came through this test very well I think, despite very mediocre seeing on the night.  Here are 30 minutes per RGB channel at 5 minutes exposures, binned 1x1.  Higher resolution of this image is here. There is no luminance here at all.  Also, no flats here since I mistakenly captured the flats at 2x2 binning as I normally bin 2x2 on RGB!  Doh... Oh well, it still came out quite well with Pixinsight's DBE tool to remove the vignetting.

So, to sum up, I am very pleased with the scope so far.  It is optically wonderful.  It looks the part and I have great pride in owning it.  The build quality is superb.  The focuser is good and robust but has slight slippage that has taken the edge off a tiny, weeny bit.

Would I buy again?  Absolutely!  This is scope for life and look forward to doing some great things with it.  I might even buy a FSQ-106 to go with it as well ;)

Next blog entries will be how I connect all the bits together to connect to my Atik EFW2 at both native and reduced.  Another blog entry will be about how I mounted the scope to my NEQ6 and guidescope.

My New Takahashi FSQ-85

I bought this wonderful new Takahashi FSQ-85EDX telescope from Ian King Imaging in November 2013 and bought it with the 0.73 reducer and numerous Takahashi adapters.  I have not as yet used it reduced, only at the native F5.3.  I am incredibly impressed with this scope!  It weighs only 4kg but feels so much more than that.  The scope is a thing of beauty with impeccable paintwork and build quality.  This is truly a scope to last a lifetime if cared for.

I went around the mental "shall I buy a 85 or 106" loop a million times.  However, I already have a RC8 telescope to give me a smaller (or zoomed in) image scale for smaller objects like M81, M87 etc and the Abell galaxy clusters.  I felt the FSQ-85 gave me better options for wide-field imaging of large targets like M31, M33, North American Nebula, Rossette Nebula etc.

My FSQ-85 rig consists of a Skywatcher ST80 guide-scope with a QHY5 guide-camera.  The whole shebang is mounted by ADM dovetails/bars/saddle onto a Skywatcher NEQ6 mount and I control it all via ASCOM/EQmod from my Dell D630 latitude laptop.

Here is a picture I did of M33 with 75 minutes of Luminance, binned at 1x1 and 20 mins each of RGB binned at 2x2.  All this done on an Atik 460 at -21C.  The seeing was terrible, the moon was rising and I was dodging clouds!  To say the UK climate is challenging for Astro-Photography with our milky white skies and constant cloud is the understatement of the century!

The image really needs more data in the colour channels and ideally some Ha as well to bring out some of the HII regions.  But not too shabby at all for a first light I reckon under the circumstances. All four corners are nicely round.

All in all I am impressed.  I intend to do some videos of how I mounted this scope so watch out for those.  I also will do some articles on how the camera connects to the scope in both reduced and native guises with the different Takahashi adapters.

Collimating My GSO RC8 telescope

Hi all, 
I thought it would be a good idea to start a Ritchey-Chretien (RC) telescope collimation discussion!  There are a lot of folk out there quite confused about how to best get these scopes collimated so here's an attempt to share some ideas.

I have recorded some videos of how I have gone about doing this on my own Altair-Astro re-badge of the GSO RC8 design.  In the US these are sometimes marketed as Astrotech and Astro-Physics RC scopes.  Teleskop-Service in Germany also rebadge them. What I discuss here is equally appropriate to the 6 and 10-inch versions of this scope too.  I understand there is also a 12" version too.  My scope is a 8" (200mm) model.

What I want is a RC scope collimation technique that I could perform during the day, at my leisure, indoors, with no artificial stars etc and would give me a high degree of accuracy - maybe not 100% perfect but somewhere approaching that and giving me a starting position to just do a quick tweak when under the stars. Clear skies in the UK and NW Europe are so rare just lately that when we get one I want to be observing and imaging and not spending half the precious time collimating scopes!

I have read some scary experiences about collimating RC telescopes.  This initially made me nervous and afraid to tinker with mine.  However, I found the process straightforward enough as long as a careful, iterative approach is adopted and you have the correct tools.  Don’t lets forget, all we are doing here is turning a few screws and adjusting mirrors slightly.  We are not splitting the atom!

The Cheshire EP method.  

Please read on and don't dismiss this technique!!! It works superbly well and gives highly accurate results. The idea with the Cheshire technique is to centre the dot from the Cheshire in the middle of the central rings by adjusting the secondary mirror.  Once this step has been done you need to ensure the central rings are concentric by adjusting the primary mirror. 

TIP: Do this outdoors on a bright day with the Cheshire 45 degree surface facing upwards (towards the sky) and the tube parallel to the ground.  It is much easier to see the shadows and reflections that way.  We want the concentric rings' reflections that you will see (as long as you are in good light) as concentric as is possible with a central dot in the centre.  Only tiny, tiny tweaks are required to do this.

Repeat these two steps perhaps three or four times until you converge on a collimated scope.  It sounds complicated and kinda scary but really, it isn't.  Its very straightforward and a quick procedure to perform.  Indeed, after playing around with numerous methods to collimate an RC scope (including the one below), the Cheshire is the one I now use because it works so well when out in the field setting up and needing to quickly tweak the scope. 

Once you get the mirrors correct as above, if you stand 3 or 4 metres (12 feet) away from the front of the tube, adjusting your viewing angle so your eye is aligned with the optical axis (by adjusting your eye position) you should see very close to a perfectly centralised series of multiple reflections, all centred around the central axis of the scope.

Once you get to this stage, use the laser collimator (an accurate one - I use my Howie Glatter) to ensure the laser is projected as close to the central secondary marker as possible and is reflected back into the origin (i.e. back into the collimator body by the secondary mirror bending the laser beam back onto itself).  I use the Teleskop-Service adjustable tipping plate to do this since I don't want to fiddle with the primary collimation screws now that I have the alignment of the mirrors correct!  Once this is done you need to use the Cheshire again to check you did not disturb the ring pattern and the centralised dot.  This iterative approach is fundamental to getting the RC scope design properly collimated.

Once this is done you are finished!  It really is straightforward and takes 5 to 10 minutes once every four months or so - these scopes hold collimation very well indeed!  The GOLDEN RULE when adjusting the scope is that tiny tweaks only to the screws are required. TINY!!! Literally 1/32 of a turn or less.  If you go at it ham-fisted you will wreck the collimation completely (although still straightforward enough to get it back if you do).

It wants to look something like this - with a central dot and concentric shadows surrounding it.  Note my scope looks better than this - it was difficult to take the photo with the camera perfectly on the optical axis!

The objective of this post however is to discuss a novel method that Jefferey Jongmans from the Netherlands introduced me to and we have discussed at some length. My advice is to read this thread entirely and take your time and don’t rush.  Do the procedure when you have plenty of time in a spare room or somewhere where you can draw the curtains/shutters to make it dark easily. Don’t be tempted to take shortcuts or skip the iterative nature of this method.

In my case I have purchased a very accurate Howie Glatter laser collimator (which I have also reviewed on my blog) and a circular holographic attachment that screws onto it.  This tool is very useful for collimating an RC scope as we shall see.  It will also be very useful for my other scopes too so I regard this investment as one that will reap dividends on my other scopes for years to come.  

I have also bought a focuser tipping plate for my RC8 scope so that the focuser can be adjusted independently from the main mirror.  Recall that on the GSO RC design, the focuser is permanently attached to the mirror.  As such on the scope as purchased one cannot adjust the alignment of the focuser independently from the primary mirror.  In a perfect world, with a 100% perfectly built scope the mechanical axis of the scope (focuser, secondary and primary) would be precisely aligned around the centre axis of the scope.  Ahhh, perfect worlds, wouldn’t that be nice?  I’d have several Ferraris, my own 40m yacht off St Tropez and my own premiership football team……  Alas, we don’t live in that perfect word and these scopes are built to a budget - its amazing they can be built as good as they are for such little money.  If the focuser and primary are not 100% perfectly mechanically aligned then unless we can separate them in some way to allow independent adjustment we can never collimate this design of RC scope properly. The tipping plate provides this decoupling of the focuser and the mirror and allows collimation of the focuser, secondary and primary completely independently.  As we shall discover later, this independence is very important.  Indeed, even if you use the Cheshire method, it is very useful to be able to separate the focuser and primary for collimation purposes.

What you'll need:
1. Cheshire Eyepiece (and if its a 1.25 inch one then ideally also a centering adaptor so that it fits snugly in a 2" focuser).
2. Howie Glatter Collimator with holographic attachment (or equivalent other brand).

STEP 1
Firstly, ensure your scope OTA is approximately parallel with the floor on your mount or a table, facing a plain wall in a well lit room (or outside of course).  You do NOT want the tube vertical and risk dropping an allen key/wrench onto your primary! 

Now, the very first thing to do if the scope is considerably out of collimation is to get it back to something resembling collimation with a Cheshire EP in a bright room or outdoors.  You want the dot to be in the centre and the rings that you see in the centre of the FoV of the Cheshire as concentric and as circular as you can.  The rest of the entire procedure is to refine what you have achieved in this very first step!  Indeed, if you are accurate enough with this step you don't need the rest of the procedure, as mentioned.  I have found I am now accurate enough with the Cheshire Eyepiece not to need to do the holographic procedure.

With an ACCURATE laser collimator inserted into the focuser check that the laser falls onto the centre marker spot of the secondary mirror – you will see this reflected off the primary by slightly standing to one side when peering into the OTA.  I cannot emphasise enough the importance of an accurate laser collimator in this method; if its inaccurate you are worse than wasting your time – you are putting errors INTO your scope!!!  As mentioned I use the Howie Glatter 2” version with the 635 nm laser.  Expensive?  Sure. Worth it?  Absolutely in my opinion.  If you want quality then get your wallet/pocket book out! Rotate the collimator in the focuser and make yourself happy that the collimator is indeed accurate; it should stay on one spot as it is rotated.  I have found that only LIGHTLY tightening the focuser EP retaining screws ensures you don’t compress the collimator body in the focuser on one side and skew the result in one direction.

If the laser is not on the centre spot (ideally in the centre of the centre spot) adjust the COLLIMATOR TIPPING PLATE so that the laser moves to the centre.  DO NOT adjust the primary or secondary at this stage. It may take some time and practise to get this right.  When you’ve done this rack the focuser in and out a few times and you may see that the laser spot does move very slightly from the dead centre but stays inside the centre spot.  Don’t worry about this too much – get it as accurate as you can.  Keep your eye on the collimator reflection back into the collimator body by the secondary mirror folding the laser beam back into itself.  This is the situation we want in step 1.   First, ensure the laser is as accurate on the centre of the secondary centre spot as you can realistically get it.  Take your time and get this right.  Now, be aware that the exact optical centre of the secondary may not be the exact physical centre of the mirror (i.e. where the centre spot is located).  It all probability it will be but it may not be (in my RC8 scope the two match precisely).  So in order to get the laser beam to bend back onto itself (and re-enter the collimator body) its possible that the laser may need to hit the secondary mirror slightly off the exact center of the secondary physical centre spot to achieve this bending of the laser onto itself.  Our objective at the end of this step is the laser is as close to the centre of the secondary collimation spot as we can realistically make it for all focuser positions with the laser folded back onto itself.  You may have to compromise getting it 100% perfect in one focuser position in order to get it 99% right for all focuser positions.

TIP – you may find that with some focusers at the very ends of the focusing action (i.e. when the focuser is all the way in or all the way out) the focuser “droops” very slightly.  Don’t worry about this - just don’t do your adjustments with the focuser in those two positions – and naturally, don’t do your imaging with the focuser like that either!  Ideally, try to find the position that the focuser will be in on your setup with your camera. 


First Step - Aligning Focuser with the Secondary Centre Spot


STEP 2
Screw the circular holographic attachment onto the Howie Glatter collimator and insert into the focuser.  Now look into the front of the OTA tube.  You are looking for a set of rings from the collimator reflected off of the secondary and back onto the primary mirror.  In other words there should be a set of concentric rings visible on the surface of the primary.  It may not be easy to see these rings and, paradoxically, the cleaner the mirror the harder it will be to see the rings.  The rings are reflected off of the microscopic dust on the mirror surface that will be present even on a very clean mirror. Adjust your eye position by hiding the bright central beam behind the secondary when viewing from the front.  Can you see the concentric rings?  They are faint so if not look again and keep trying!  They will definitely be there.  You may need to darken the room.

When you have found the rings you want them to be as concentric as you can possibly get them and equidistant from the centre and to the mirror edge.  Rack the focuser in and out to try to get a ring near the edge of the mirror – this makes it easier to judge whether or not they are concentric.  If they are not, and it will be most obvious if they are not, you need to adjust the three collimation screws on the secondary.  Using VERY small adjustments, only a 1/32 of a turn or less, adjust these three screws to get the rings concentric on the primary’s surface, checking after every tweak. It can be tricky to do this and see the effect on the rings simultaneously. 

Personally, I have found that combining this ring viewing method and a Cheshire EP to be highly effective.   Get the dot in the centre by adjusting the secondary by using a Cheshire EP then swap for the laser holograph and check the rings again by viewing from the front of the OTA.  It is surprising how little adjustment of those screws is needed. Very small tweaks are the difference between being collimated and not collimated.  Take your time and enjoy doing this precision part of our hobby!  That said, don’t be obsessive either.  You want it as accurate as is realistically possible within your capabilities.  You can get 98% there in five minutes say but that final 2% can take hours!  Don’t bother!  When checking the concentric rings get them as good as you can.  They may not be 100% perfect but do the best you can.  For example, if the rings are one or two mm from being perfect then don't bother adjusting - that is accurate enough.  It isn't the Hubble Space Telescope we're collimating here!

At the end of this step our objective is as near as possible to concentric rings on the primary surface with the laser central beam folded back onto itself back into the collimator body.  Do not move onto step 3 until you have achieved these objectives.

Second Step - Ensure Perfect Circles reflected onto Primary

Should look something like this

STEP 3
You may have noticed the rings on the primary mirror we discussed in Step 2 are also projected from the primary out the front of the OTA onto an adjacent surface.  In this third step we want to project those rings onto a wall about two metres (6 feet) or so away.  The scope needs to be approximately parallel to the floor. We are looking for concentric rings on the wall with the shadow of the secondary absolutely centred.  Make some accurate circles on a piece of paper and tape it to the wall or use a ruler to check.

You may think that if step 2 was done carefully to achieve concentric rings then surely step 3 would be unnecessary and that the rings on the wall must likewise be concentric?  This is NOT the case with a RC scope.  This is because the primary mirror could be slightly tipped with respect to the secondary resulting in the wall projection being inaccurate with incomplete or partial inner or outer rings even though step 2 was perfectly concentric.  Remember, with an RC design we are adjusting two hyperbolic mirror surfaces, not just the secondary that we were adjusting in step 2.  These two mirrors need to be collimated with respect to each other.

It is very possible that your scope shows these rings perfectly without any adjustment.  This is because in the RC design the secondary can lose collimation more easily than the primary. If so then good for you and well done!  However, if the rings on the wall are not concentric, or the secondary shadow is not central, or you have partial inner or outer rings, then the primary mirror needs to be adjusted.  Again, only small adjustments or tweaks to the primary mirror collimation screws are required.  Observe the rings on the wall whilst adjusting the primary collimation screws. Get the wall rings as concentric as possible.  Also, ensure that when the focuser is racked in and out the outermost and innermost rings on the wall “come in and out of view” around the whole ring at approximately the same time.    You want the rings to fade in and out all around the edge at almost the same focuser position - this indicates alignment of the two mirrors.  You may not get this 100% perfect but do your best.  You will find that only the inner and outer rings will show this effect – the middle rings will always be visible.  Again, take your time and don’t rush.  Little tweaks are all that are required.


Third Step - Project Rings onto Wall

This is the projection on the wall

Now, in the process of collimating the primary mirror in step3, we will also have slightly spoiled steps 1 and 2 since the focuser tipping ring and focuser itself will have moved slightly as a result of adjusting the primary mirror.  So go back to step 1.  Check again the beam is on the centre spot (removing the holographic attachment of course before doing so).  Then check for the concentric rings on the primary and finally the projection on the wall again.  You will find the second and third iterations take only a couple of minutes now you understand the method.  Before putting your tools away make sure all the collimation screws are tight, particularly the locking ones on the primary.  Then do a final check.  This process may take some time the first time you do it when you are naturally being very cautious.  But trust me, it gets a lot quicker after a few practices!

NOTE.  I have found that it is quite tricky to get all three stages perfect for all focuser positions.  In other words you may find you can get it perfect in one focuser position but it will then move out slightly for different focuser positions.  So I suggest that before you start this procedure, make a note of where your focuser is with respect to your imaging train setup when in focus one night and then perform this three step procedure with the focuser in that position.

Finally you may want to do a star test and a final primary tweak to further refine the collimation.  But this method will get you very close to collimation whilst indoors and you may not need to do such a star test!  Check also with your Cheshire EP and with the "hall of mirrors" method.  It should be almost spot on accurate!  And there’s the thing…. you can still get very accurate collimation with the Cheshire EP alone if you know what you are doing.  But the holograph method makes it so very easy to CHECK the results and allows you to fiddle with collimation screws in real time whilst checking the circular patterns whilst you have the wrenches in your hands.  Brilliant!

It goes without saying that now you have got the scope collimated you DO NOT want to remove the focuser  or turn it!  If you do you, or you need to add another M90 tube extender, you will probably slightly disturb step 1 and as a consequence steps 2 and 3.  Ideally you should collimate again.

I have found that RC telescopes hold their collimation fantastically well.  Since the primary does not move, like it does on a SCT, the collimation tends to stay accurate for many months at a time unlike a Newtonian.

Enjoy using your collimated RC telescope!  They are truly wonderful and easy scopes to own!

By all means feel free to add your own experiences to this in the chat window below.

Review of the Howie Glatter Laser Collimator

I have bought this super Laser Collimator and I have reviewed it here.  Hope you find it useful.

In the past I have had nothing but trouble with "budget" laser collimators.  I have been in tears of frustration with them, almost, and thrown them at the brick wall in desperation.  Could the Howie Glatter laser collimator be the exception?  Lets see....

This collimator works extremely well on my Ritchey Chretien RC telescope; see the method in my post.