Very Amateur Astronomy

I had another go at the ISS last night, this time with the 2x barlow in place in an attempt to achieve higher magnification :

• Exposure 1/1500
• Gain 50
• Brightness 60

I think that’s gone a bit above the limit of the webcam. I can’t increase the exposure any further without getting blurring, which means I have to increase the gain which in turn produces to much noise. Still it has been a very production week for imaging for me.

The next experiment now I have the UV/IR cut filter is to look at using EOS movie record to capture the AVI through the barlow and see what magnification I get with that combination. The better chip and better control should allow for a better image, but I think any targets will be to small. I may need to keep an eye out for a higher magnification barlow for this option.

I also want to try the webcam, through the barlow but with my 0.6 reducer attached as well. I may well be getting carried away there though. The ideal would be an imaging source camera, add yet another item to the shopping list!

Continuing my exploration of webcam astrophotography I have had a couple of goes at capturing the ISS as it has been very bright for us in south east England over the last few nights. The best efforts came from last night.

Some good detail captured there, so I’m happy with that! The equipment and settings used are as follows :

• Orion Optics Europa 250mm Reflector
• Manually guided on the Vixen Sphinx mount
• Philips SPC900NC webcam (Exp 1/2500 – Gain 40 – Bright 60)

I captured around 2000 frames of which about 50 contained the target, any sequential runs of four or more were exported and stacked in Registax. I applied a gentle wavelets filter to bring out the detail, then a very soft gaussian blur to clean them up.

Tonight I may go completely mad and try it with the 2x barlow!

Last night I spent a bit more time working on the Andromeda image in Pixinsight to sort out the colour, boost the saturation and remove a bit more noise from the image. I’m now finished I think, and I have to admit to be very pleased with the result.

Here is a close up of the core cropped from the full size original image. You can see detail right down to the centre.

My next challenge will be to improve my knowledge and skills of the software by reprocessing some of my older images. I can’t wait to see what lies hidden behind my previous dodgy versions!

I’m never happy with my processing, and I’m always looking for a better way. On the strength of various threads on the Stargazers Lounge forum I decided to have a go with the Pixinsight astronomy image processing suite, following the excellent video guides from Harry Page. Here is the result :

You can see I have managed to create a significantly more subtle image, and retained detail right down to the core. I’ve got to say I am hugely impressed with pixinsight, everything just seemed to come together so much easier!

I’ve been meaning to give this a go for a while, but the lure of deep sky has kept me from it so far. Unfortunately however, I broke the starbook controller for my mount last weekend and it’s away for repairs, and with out that the mount won’t do anything useful at all.

Still, looking at it as an opportunity to try something new, and understanding that in webcam astrophotography only short exposures are required, I decided to see what I could do with Jupiter.

Not bad for a first attempt really, you can at least tell what it is! This is Jupiter compiled from about three and a half minutes of video captured my my Philips SPC900NC webcam and stacking in registax 5.

To improve the image I’m going to need to zoom it in a bit more, which means a barlow, which I have. But will also require an IR filter as passing light through a lens causes the infra red light to scatter, making focus very nearly impossible to reach. So that’s the next item on the shopping list.

So, it’s been a bit quite here recently as August was a very busy month. Myself, my wife and my three year old son drove the 1000 miles or so from Basingstoke to north Italy for a two week holiday in the lakes. Specifically we stayed at the wonderful Camping Al Sole on the beautiful Lago Di Ledro, not far from the north tip of Lago di Garda. We had a fantastic time, visited various castles, swam in the lake a lot and I of course got some imaging done.

I took my Vixen Sphinx mount on it’s portable pier setup, and a lovely little William Optics ZS66SD telescope with the 0.6x Focal Reducer and flattener. I was tied to the tent unfortunately as I ran out of space in the car for a portable power supply, but as we were 2000ft up in the mountains it wasn’t the worst thing, at least I had a bottle of wine close to hand. The seeing was excellent even with the camp sites bright white globe lights, and Andromeda was the best target in the clear view between the trees. Here is the result :

• William Optics ZS66SD / 0.6x Focal Reducer / Flattener
• Canon EOS 1000D – unmodified
• Vixen Sphinx Mount – no guiding
• 93 x 2.30 exposures / 3h 52m total exposure time
• Stacked in Iris

The critical viewer will note that on this processing attempt I’ve made a few mistakes, noticeably I’ve over done the white point resulting in some nasty looking stars and wiping out detail in some areas. Also I think my flats have been incorrect, I’ll be taking some more tonight to get the exposure level better and recompiling the image.

Unfortunately I managed to damage my Starbook over the weekend so I’ll be out of action on the deep space imaging until it is repaired. I’m not sure if Jupiter is in a suitable position for imaging with the webcam right now either but I’ll be giving it a go.

It’s always the way, some things are as predictable as, well, the planets I guess. I get the best night for imaging I’ve had for ages, and it’s on a Friday night so I don’t have to get up in the morning, my wife has no complaints,- so I head out and get myself setup. Naturally nothing works properly at all and I end up spending a fruitless night getting no where fast as I attempt to track down all the little problems.

First off the mount is tracking terribly, this one I can only blame myself for. I had remounted the scope in a different configuration the day before, and then re-leveled the mount to insure everything was square. Unfortunately I neglected to realign the mount after and didn’t do it before I started imaging. This combination threw out the tracking and the goto and PHD guiding wasn’t very happy at all.

Once I had everything sort of working I tried to get a bit of imaging going with what I had left of the night, again my own lack of thought kicked me squarely in the nuts. Imaging with a standard DSLR can give very nice results, but as people expect there photos to look exactly like the image we see through our own limited eye sight DSLR cameras have an in built IR filter. If they didn’t have one all our pictures would look red. Unfortunately for the budding astrophotographer using such a tool, pointing it at a faint red nebula and taking pictures is likely to result in disappointment, which is exactly what I did. I knew the scope was in the right spot, the stars matched, but I could see nothing of the nebula! Lesson learnt, one day I may have to get the camera modified.

With the night rolling on I had one last chance of getting some worth while imaging going and swung the scope round to the rapidly rising Jupiter which has now cleared the tree on my southern horizon. Now for planets the weapon of choice is the webcam, so that’s what I decided to try with. I had no trouble finding or centering Jupiter in the webcam, but focus was another matter.

To focus my DSLR I have it at prime focus, directly into the focuser, to focus a 1.25″ eyepiece I have to use a 50mm extension tube. The webcam though, well at prime without the extension it won’t rack out enough, with the extension it won’t rack in enough! So I need a smaller extension tube, something like a 30mm should do it.

So I put a 5mm TMB planetary eyepiece in and just enjoyed a fantastic view of Jupiter and it’s collection of moons instead.

A reasonable successful imaging session last night I think, though I won’t see the results until I can process the frames this evening. However I still have some issues which require further investigation, mainly there is still a small amount of drift and occasionally a noticeable shift where I end up with double stars.

The prime culprit for this is almost certainly going to be differential flexure, that being movement or changes in the optical path of the imaging scope or the guiding scope resulting in drift in the image. So whats the cause and how can we fix it? Well the potential causes are many.

1. Mirror sag – the primary mirror shifts slightly as the scope tracks
2. Focuser sag – the focuser shifts slightly as the scope tracks
3. Camera sag – the camera moves as the scope tracks
4. Tube flex – the optical tube bends of flexes as it tracks
5. Mount flex – the scope array shifts on the mount

The problem here is that  scope  guiding, where the guide camera looks through a different scope to the imaging camera, requires that both scopes remain perfectly in position with no deviation in where they point. The guide scope is technically only guiding itself, if anything moves or changes on the imaging side then the guide software won’t care, as long as it’s camera remains pointing in the right place it doesn’t matter.

My task then is to eliminate this by carefully addressing each potential cause and correcting it, so starting from tonight I’ll be on a mission to :

• Fix the primary mirror, make sure it doesn’t move.
• Tune the focuser, ensure it does not shift with the weight of the camera
• Improve the fit of my tube rings, the felt is thick and will allow shift
• Improve the mounting of the guide scope, it can move to much at present
• Improve cable runs to prevent pulling on cameras
• Improve the fit of the declination head and the clamping on the mounting

Busy, busy.

Once again I am somewhat humbled by the abilities of others. CloudWatcher a poster on the Stargazers Lounge message boards took my jpeg and applied a measure of experience and as far as I can tell a dash of magic and turned it into this.

So much better in every way. I did not even think that I could turn what I had into anything like this, and despite an hour or so mucking about with the hue and saturation controls I still can’t pull out anything quite like this! I shall plod on though, ever time I post a new image I learn something new!

I’ve been having a go with these techniques on my M101 image with the following results, you can compare in the gallary, I think I’ve brought out the depth a bit more.

The skies finally cleared last night allowing me to have a go with my upgrades from the last few weeks. For a target I chose NGC6946, the fireworks galaxy, it’s impossible for me to see it from my site with an eyepiece and even a two minute exposure only brought out a very faint core.

I had everything setup reasonably quickly and managed to locate a guide star after quite a bit of mucking about, the 70mm F12.9 refractor really needs a focal reducer, the field of view if tiny and the web cams tiny chip does not improve it much at all.

I went with 6 minute exposures with auto guiding controlled by PHD guiding. It seemed fine most of the time, but every so often the scope would for some reason move and the guide star would shift just enough for PHD to loose it. This resulted in several lost frames each time it happened, the scopes had slipped pushing things out of balance which may explain the problem.

Still for a first attempt on a faint object with only limited exposure time it’s not terrible. I’ll have to revisit this one in the future and get another couple of hours of data.