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Richie's Blog

Starlight Xpress Filter Wheel and SXVR-H18 Collimation
Written by Richie Jarvis   
Sunday, 08 May 2011 18:06


I've recently acquired a Starlight Xpress Filter Wheel and Off-Axis Guider to go with my Starlight Xpress SXVR-H18.  One of the first things that needed doing was to ensure that the chip is correctly collimated with the optical axis.

When the SXVR-H18 is fitted to the filter wheel, the T-Threaded ring is removed and replaced by a special plate for the SXVR-H18.  This plate requires accurate collimation with the chip in the camera, as the plate will be inline with the optical axis of the telescope.

My solution, which I dreamt up whilst sufferring a bout of insomnia involves using a standard low power green laser pointer and using the reflections from the laser to align the plate and the chip.

The Setup

The green laser pointer (a low power one) was mounted on a tripod, and I made a simple bracket from a shelving bracket and a short dovetail bar. This was then aimed just to the side of my workbench vice.  The camera and plate were then mounted in the vice.  The screen is a sheet of paper laminated and cut down to size.


Step 1: Collimating the Plate

First, we need to ensure that the plate is accurately aligned with the laser.  The black surface of the plate was not enough to reflect the laser in daytime, so I put some brown parcel tape on the plate to provide extra reflection.

Here is the plate with the brown parcel tape in place.

Here is the initial rough alignment by moving the tripod around.

Step 2: Plate in Alignment

Once the return from the chip is in line with the hole in the paper, the plate is aligned, and you are ready to move onto the next step.

Step 3: Rotate chip into line

Now undo the vice, and rotate the camera chip into the laser beam.  If you have a shutter, like the SXVR-H18, then you will need to run a computer to open the shutter.  The power supply isn't required for this though!  I used 10 minute sub-exposures for my setup.  You might think this would cause damage to the chip - I certainly was worried, and so checked with Terry Platt on the SX forum.  He confirmed that there should be no problem with shooting a low power laser at the camera.

Step 4: Align the chip using the grubscrews

My initial rough alignment looked like this. The chip throws off a 5 point reflection.  The sixth point nearest to the central spot on this picture is the glass reflection I believe.

After tweaking the grubscrews, here is the camera almost in collimation.

A few final tweaks, and the central reflection is in alignment with the spot.

Voila! Your done :)

A Supernova, some galaxies and a handful of clusters!
Written by Richie Jarvis   
Saturday, 07 May 2011 01:14

Its been an interesting few weeks.  My new Starlight Xpress Filter Wheel and Off-Axis Guider has arrived, and I've now got a set of LRGB 2" Astronomik filters to go with it.  Waiting for the Ha and Oiii, but for now I am strictly confined to true colour imaging!  It couldn't have been timed better - the last few weeks have been warm and mostly clear.  I've had chance to shoot a relatively new supernova (SN2011by) in NGC3972, and also been catching up on Globular Clusters with Messier 3, Messier 53 and NGC5053.

NGC3972 and a few other galaxies in Ursa Major.  SN2011by is marked.  Click for the image capture details and a large version.

Preparation for this months Under British Skies show has also been quite hectic.  We've got an update from Nick Howes on his recent grand astro tour of NEAF and NAM.  John Zarnecki kindly took some time to speak to Sam Hawkins and I, and Paul Harper and Tavi Greiner interviewed Geoff Notkin, one of the famed Meteorite Men.  I've still got to get that little lot edited up before the next show on the 15th!

I have also just uploaded my latest 'Clear Skies' talk, so you can have some fun investigating the night sky.  Get it here as a pdf.

Clear Skies All!


Simple Image Processing Tutorial
Written by Richie Jarvis   
Wednesday, 23 March 2011 22:58

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Isle of Wight Star Party and a new piccy
Written by Richie Jarvis   
Sunday, 13 March 2011 22:03

Just got back from the Isle of Wight Star Party, had a thoroughly great time as per usual.  Stephen, Lucy and Bill did a wonderful job yet again.  Good times.

Whilst I was on the island, I captured a few Ha exposures of the Rosette Nebula, and decided to finish it off with some Oiii when I got home.  The weather was kind on Monday night, so I was able to grab 14 x 15 minute exposures to go with the 12 Ha exposures I captured on the island.

After a bit of processing, here is how it came out.  Very pleased with the result, and it is now entered into the Astronomy Photographer of the Year competition at the Royal Observatory Greenwich.  Fingers crossed!

Click for full image and capture details:

A work in progress
Written by Richie Jarvis   
Friday, 07 January 2011 19:25


You know that feeling that you are just not happy with something?  Well, I've got that at the moment.  I wanted to put M42 to bed once and for all.  Its a lovely target in our Winter skies, but how many images of M42 does a man need?

This year, I have an excuse though.  The H18 and the Televue Genesis give me a 2" field of view.  That alone is a good excuse to re-visit the area in my book, so I did.  So far this year, I've captured 8 and a half hours worth of data, and thats not including the data I threw away!  My official standpoint is 'its getting there' - Ha and Oiii have been the focus so far.  I have enough data in those bands now, giving a nice and smooth result.  But I don't like the way the Running Man Nebula (to the left of the image) is not showing his true colours.  There should be more blue evident in the image that the Oiii filter just is not picking up.

The plan?  I want to see if I can capture some Blue filter data before the end of the Winter.  With any luck, that will combine well with the Ha and Oiii filter data and finally put this one to bed.  And as for the rest of the Winter skies?  Once this is done, the Vixen will be going back on the EQ6, and its back to capture this years Messier 1 data to see if I can pickup any changes since last year.  I've left it a bit late in the season, but beggars can't be choosers!

Happy New Year and Clear Skies Everyone!


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