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Richie's Blog


Collimation, Focusing and Seeing
Written by Richie Jarvis   
Tuesday, 11 October 2011 20:54

Over the last few years, I have been trying in vain to get good images of the planets.  I've blamed it on alot of different things, however, I think the real problem was insufficient attention to detail!

To try and correct my problems, I've been checking the collimation and focusing of my VC200L with my Skynyx 2-1c and Televue 3x barlow.

This first video shows the collimation of the setup.  To obtain this video, I pointed at Vega, and then racked the focus in and out.  It was a little cloudy as well, as you can see from the video!  I hope to run this past other astronomers as well to see if they think my setup is collimated 'enough' - because I really am not sure at this point!!!

Update: Damian Peach kindly looked over the videos - his opinion is that my collimation 'looks pretty good to me'

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Now for focusing.  I use a Bahtinov mask to achieve my focusing with Deep Sky objects, and so thought it might work here too.  This is a video shot with the Bahtinov in place - I am winding the focus knob in and out before finally achieving a 'good' focus.  Notice that the diffraction spikes jump around alot - I guess this is indication of bad seeing (and vibrations whilst I am touching the scope!)

Comments appreciated on this one also....

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Update: Damian also looked at this video, and commented 'the seeing looks a bit ropy in the video when focusing'

So to get a gauge on this, I shot this video, which shows the star Hamal in Aries both with and without the Bahtinov mask.  As you can see, the star dances around alot, which when compared to Damian's Pickering Scale videos seen here: http://www.damianpeach.com/pickering.htm - I reckon that is about a pickering scale 4...  Poor....  No wonder my Jupiter images are coming out pants!

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Pinwheel Galaxy Supernova
Written by Richie Jarvis   
Sunday, 11 September 2011 22:16

The recent Type 1a Supernova discovered by the Palomar Transit Factory, and labelled as PTF11kly.  It was discovered on 24th August, and anyone with images showing this supernova earlier should contact This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

The skies have not been kinda for me to image this Supernova, however, I did manage to get some red frames for photometry purposes on the 6th September 2011.  I measured the magnitude of the supernova as 9.9 from this image using the wonderful Astrometrica software from Herbert Raab.

I hope to be able to image this galaxy over the next few weeks, and discover whether it continues to brighten, or starts to diminish.

If you wish to find and view this supernova for yourself, my friends over at the Society for Popular Astronomy have produced this wonderful guide.

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

Introduction

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!

Richie

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

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