A few posts below I gave a procedure on collimating your imaging camera to a Hyperstar III.  On reflection I thought that this could be considered as so much “hot air” without results to prove the procedure actually works.  So a few nights ago I fired up the Hyperstar III and ran through the collimation procedure with a nicely flattened M25C OSC CCD.  I flattened the M25C chip using the procedure described on the Starlight Xpress web site.  The results of around 45-minutes of collimation adjustments are given below, and the results speak for themselves

A larger view of the results can be seen here:

On the evening of the 19th October I got a couple of clear hours before it clouded over.  Enough time to set up the Hyperstar and get an hour (4 x 15-minute subs) on the California nebula.  I had forgotten just how fast the Hyperstar is – a total of 1-hour’s exposure time only, but that is equal to five hours on a Sky 90 at f#4.5 I suppose.  Still, the Hyperstar is FAST

It is possible to get perfect stars right across the diagonal of an APS-size chip such as the Starlight Xpress M25C or M26C – but only if your Hyperstar imaging system is in very good collimation.  Getting good collimation is not a trivial exercise, but once you have it set up then it only becomes a matter of very small tweaks if any mirror movement requires re-collimation.

The very first thing you must do is make sure that your imaging chip is perfectly normal to the optical axis.  For the Starlight Xpress cameras mentioned above there are adjustment screws to move the camera chip with respect to the front plate which connects to your OTA.  Starlight give a method here http://www.sxccd.com/maintenance_info/Aligning_CCD.pdf for getting the chip flat using a laser pen.  I have found that this method works extremely well and you can get precise chip flatness very quickly and easily once you have gone through the process a couple of times.  The only change I made to the Starlight setup was that I work in a vertical plane with the laser pen pointing upwards from the ground as using this geometry you don’t have the camera mounted sideways against gravity.  Being vertically mounted makes it a lot easier to maintain the camera flat against whatever rotation holder you use.

With the camera chip perfectly flat to the front plate, fix the camera to the Hyperstar and get a good focus.  I recommend the electric MicroFocuser and MicroTouch software for all your focusing.  You can do it manually, but it takes much longer using that route.  Get a good focus and take a 20-second image.

Unless you are extremely lucky you will find that stars towards the centre of the image look pretty good, but stars out towards the edge are “tailed” like comets – and this is the collimation needing adjusting.  You will need the program CCDInspector to get really good collimation, and to get a numerical feedback that your collimation is good – but the initial “rough” collimation is done by eye by referring to the image on the monitor.

Pick any one of the Hyperstar collimation adjusters and move it either in or out a touch, where a touch is no more than a quarter of a turn.  Retake the image and note the result on the outermost stars.  It will soon become obvious which adjustments “push the tail” of the stars up into the main star until you end up with a decent looking round star.  With the collimation adjustments made so that you can see you have decent round stars in all 4 corners, you are good to go, and you will get extremely good results from your Hyperstar – but you can fine tweak things a little better than your eye can pick up just looking at the monitor – and this is where CCDInspector comes in.

Take a 20-second image of a star field preferably without galaxies or nebulae in the field as these can “throw” the CCDInspector values out.  Put CCDInspector into arc seconds mode rather than giving “pixels” output, as this gives you more accuracy in the next part of the setup.  You will see values for the tilt in the X and Y directions, and the aim now is to get the smallest value you can for these.  The next adjustments of the collimation screws on the Hyperstar are TINY, no big movements or you will throw away all your hard work so far.  You now need to make tiny adjustments of the collimation screws on the Hyperstar and note their effect on the tilt X and Y values as you adjust them.  You will need to write these figures down as relying on memory alone, especially if you are working out in the freezing cold, simply doesn’t work.  You will also need to re-focus after each adjustment and this is why it is a very good idea to have computer-controlled focusing, otherwise this step will simply take far too long.  Make adjustments to the collimation screws to get the smallest values you can for the tilt in X and Y in CCDInspector, and don’t forget to refocus after each adjustment.  You will see that a natural by-product of small X and Y tilt values is a small value for the collimation and for the field curvature.  Proceed iteratively until you get the smallest X and Y values possible.

Finally, when you have managed to get the Hyperstar collimated as best you can, it is a good idea to then re-run all your V-curves for FocusMax so that they apply to your new, nicely collimated system.

That’s all there is to it – Happy Imaging J

I have completed the initial experiments with the Canon 200mm lens piggy-backed on the C11, so yesterday I removed the kludge on the back of the C11 and re-instated the Hyperstar III – just in time for all the winter goodies.

The 200mm lens will go on the top plate of the mini-WASP with the other 200mm lens.  One lens will have an M26C attached, the other will use the Canon 5D MkII – all bases covered.

Cloud last night meant I couldn’t focus train and collimate the Hyperstar III – but from the images I did download I could see there wasn’t too much sorting out to do.

So final steps before we’re up and running again, focus train using FocusMax and collimate the Hyperstar using CCDInspector.

Then image the goodies

Managed to get 15 x 4-minute subs using the Hyperstar III on the new supernova in M82 last night.  Although the sky looked crystal clear, and was Moonless as a bonus, the seeing was terrible.  Never mind – I do have at least a decent record of the event

So what’s the excuse for such a grubby image then? Half the sky (towards the East) was clear at 6:00 p.m. but half the sky running north to south and covering the whole of the West was black and overcast. M82 was in the clear bit  Fired up the Hyperstar, did the 2 star align, autofocused on the second star and slewed to M82 – all going well so far. Took a single 30-second sub to check the framing (that’s the image above) – great – M82 is dead centre. Now just need to get a guide star, get autoguiding, and get a load of subs. Autoguide setup playing up – yep, completely clouded out in those 10-15 minutes  So all I got was this 30-second setting up sub. But at least you can see the damn thing.

As it has been non-stop rain for days on end now, I have resorted to taking a look at old data.

Just put together all the datasets I could find of the Cygnus Wall region taken with the Hyperstar III and the M25C one shot colour camera.

You can see the result here:

The Canon 200mm prime lens and the Canon 5D MkII DSLR were put to good use a few days back grabbing a massive (10 x 6.8 degree) wide-field around the Cocoon nebula in Cygnus.  Using ISO 400 and f#4.5 with an IDAS filter I captured 21 x 4-minute subs with the DSLR and guided using the SX guide camera on a small refractor – all piggy-backed on the C11 which is now groaning under all the added weight.  Further Hyperstar III data of the Cocoon region alone was added to the DSLR template by Noel Carboni who created the final composite using Photoshop and his Astronomy Action Tools.  The Hyperstar III data set was taken a couple of years ago and comprises a 3-frame mosaic with each frame being around 3-4 hours total exposure time using 10-minute sub-exposures.

This combination of using the DSLR to create the wide-field star-field template, and then filling in the nebulosity and faint stuff with either the Hyperstar III or the mini-WASP looks like a winning combination.  The only problem is that the images only look impressive when printed out BIG – all the detail gets lost in A4 size or smaller.

This is a composite image combining the recent 8 x 20-minute subs from the Hyperstar III with earlier Sky 90/M25C which incorporated H-alpha and OIII narrowband data.

Taken with the HSIII on 04/07/2013 this is an S-type star, SAO 69360 in Cygnus.