Monthly Archives: June 2005

Mac Astro Software

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I’m not happy with the state of astronomical image-processing software on the Mac. I’ve been using Keith’s Image Stacker for the past few days, and while it’s better than nothing, it’s not better by much. So far it has crashed several times, and in one case managed to remove all trace of work in progress (in fact, trying to save the work in progress triggered the crash). The interface is not well thought out, and it doesn’t protect you from silly errors. In trying to remove one frame from a stack I wound up removing all frames – there’s no fail-safe asking whether you’re sure you want to wipe out all your work….

iCCD and iAstronomy looked as though they might be worthwhile, but iCCD doesn’t support digital SLR cameras, and iAstronomy doesn’t support Canon 20Ds (supposedly the author is working on it, but he hasn’t responded to my queries)July 3 – Steve Bryson responded, more later. I’ll be looking at PC software shortly, turning to the Dark Side if I must.

Cheating

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The cloud gods have been having a conversation over the observatory, so I’m still playing with the M57 captures from last week. There’s a small 14th magnitude (14.8 – but that’s integrated rather than surface brightness, and so not seen at the same time as 14th magnitude stars) spiral galaxy [IC1296] close to the Ring. You can see it in this link[hmm, seems to be broken now]. Knowing that the galaxy is present — i.e., cheating — with a lot of processing and a certain amount of wishful thinking you can see the core of the galaxy in this image (roll your mouse over the image to see the equivalent normal image):

M57 area showing supposed galaxy

It’s just a dot in the image, so not directly identifiable as a spiral galaxy. It’s much fainter – to the point of being a smudge not much better than variation due to noise in the normal image.

Can’t see it? You have to believe! [And if the mouse rollover does nothing for you, you need a newer browser...]

This started out as a stack of 7 10-second images with a common dark frame removed. Some of the stars which are definitely there are as low as magnitude 15.3, and the central star of M57 is clearly present at magnitude 15.2. There’s still a lot of noise – the images were captured at ISO1600 using an uncooled Canon 20D in 30 degree Celsius conditions (and lots of mosquitoes!). Some stars I expected to see were not found, or are dimmer than expected. I’m not sure if I processed them out of the image or if there was a problem with colour sensitivity. The visual magnitude limit at the time was 2 or 2 1/2, and the sky was a nasty reddish brown from the sky glow. Removing the sky glow has compromised the colour, but if the haze ever goes away I will try again with longer exposures in an attempt to capture the colour properly. Unfortunately weekend predictions are for clear skies with poor transparency.

Reworking the Ring

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It’s been a while since I used Keith’s Image Stacker, so I thought I’d take another look at it. I have to say it’s still a pain to use, but on the other hand it has become a good deal more useful than it used to be. I took eight 10-second images of the Ring Nebula and added them together to get this image:

A closely cropped image of M57, the Ring Nebula

–Not a great shot, but definitely better than the single 10-second frame I was looking at before. This is actually several generations removed from the original series of images, and has gone through at least one stage of jpeggery, so the noise level is not entirely valid. No dark frame was subtracted, and the background sky fogging was fairly high before it was removed, so I’m neither surprised by the noise nor unhappy with it. The sky has been clear for the past few days, but transparency has been terrible, with a high haze which doesn’t dissipate until early morning — by which point it is starting to build again. Heat alerts and smog alerts have been coming fast and furiously all week.

At prime focus

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I captured a few Jupiter images and a few Ring Nebula images at the prime focus of the FLT-110 scope. I was using an Orion two-inch T-mount adapter to connect the camera to the scope, but the back focus was just a tad short. With great trepidation I pulled the camera slightly out of the two-inch holder and clamped it down TIGHT, and I was able to reach focus.

Immediately I realised I needed a couple of additions to my accessory rack. For one thing, the USB 2.0 cable supplied with the camera is inadequate. I knew that before but I couldn’t find my regular extension cable, so the point was driven home hard. It’s also clear that the scope has drifted way out of alignment over the winter. I’ll have to correct that as soon as possible. Visually it’s fine, but as soon as you try to image it becomes clear that the image is turning – the alignment with the pole is way off, and only the Gemini saves the visual appearance. I also need to swap the laptop for a while so that I can use DSLR Focus and – probably – Mike Unsold’s excellent Images Plus software. The Mac just doesn’t have the support right now for EASY astro-imaging. That’s not to say the Mac can’t be used, but the 20D is supported on Wintel right now, but not on the Mac. That’s probably because of Canon’s policy about the SDK for their DSLR products: you have to have a company of some sort to obtain the SDK – hobbyists need not apply. And that’s a shame.

Keeping my fingers crossed

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According to both regular weather reports and the Clear Sky site, Sunday 19 June will have clear skies in the evening hours. On the assumption that that’s correct I’m going to work myself up to taking at least one image on Sunday. That sounds like a paltry ambition, but I’m up to my ears in work-related activity, specifically in making corrections to malformed XML on a number of CDs. We can’t regenerate the XML files in a reasonable amount of time so we have to dive into text files which fill the entire CD and change them so they pass validation tests. I can’t say much more as there are confidentiality concerns, but I made a commitment to deliver the replacement CDs sometime on Monday so I’ve been busily editing and validating the files. Unfortunately after I committed to a schedule my process went south, and though I can still edit the files it is now taking many more hours than anticipated to complete the file changes and testing. I think I have the process back under control, but I’m way behind where I expected to be at this moment. Despite this, I’ll take a little time out after dusk tomorrow so that I can grab an image or two. I’m figuring by then I’ll need the break.

Wish me luck!

A new feature

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Through the kind courtesy of Attila Danko there is now a Clear Sky clock for Woodbridge, Ontario. This makes it easier for me to figure out when the skies are likely to be good for observing. This is particularly useful for me as the weekend approaches, but will also be useful during the week as the summer dwindles and the nights grow longer.

Anyway, a thumbnail of the predictions for the area now appears at the top of each page, and you can click on it to see a larger and more detailed view. If you’re an amateur astronomer in North America, bookmark the Clear Sky home page and keep an eye on your own location. And don’t forget to send a few bucks every now and then to Attila – he deserves our support!

Watching Jupiter

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Transparency is currently the pits, though the sky is relatively clear. All four of the Galilean satellites are spread for review on the eastern (I think – have to consider this) side of the planet, but the Great Red Spot is not yet visible, and won’t be for a couple of hours. The planet itself is a far cry from the view in the DDO’s little scope — it’s hard to see in the 3 mm eyepiece, though the magnification is comparable, and I can see Callisto mainly by averted vision – that’s about magnitude 6 as a limit in a 110 mm scope!. Even making allowances for Jupiter’s glare, that’s low transparency! Looking straight up from where I sit the sky is a milky grey colour, and though I can see Arcturus it is rivalled by the glow from the searchlights to the south at the local cinema – and I can’t see other stars unless I know exactly where to look. Still, I spent quite a while watching Jupiter and the satellites dancing – Callisto passed north of Jupiter, and Europa was overtaking Io as I shut down for the night. Without the observatory I probably wouldn’t have bothered, so I count this as a positive mark for the observatory.

The solar filter design died over the winter as the foam core deteriorated in the sunlight. I’ll try using plywood instead, but in the meantime I’ve marked the filter as “out of stock” on the store page.

Riding the Weather rollercoaster

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I had thought this week that I would head out to the Lorentz Observatory a few miles northeast of Cobourg, Ontario and set up for some dark sky observing. Early in the week the forecast looked good, and I expected I would be joining other members of the NYAA overnight Saturday. Then the weather forecast turned right around, and people started cancelling out. I changed my plans and set up for cloudy night activities. Now stepping outside I look at the sky and it’s clear, though transparency looks poor. The Clear Sky clock shows the L.O. site as clear, with average transparency and seeing throughout the early evening. I’ll slip outside later to see how Jupiter looks, but I suspect that fuzzies will be beyond my reach tonight – but perhaps I can set up the camera at prime focus instead of afocally. I live in hope….

Coping with an upgrade

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I’m in the middle of upgrading my laptop — iBook, actually — after the previous version fell victim to a relatively common problem in which the display would flicker when the laptop was open at certain angles.

The new version is faster – 1.2 GHz against 800 MHz, has a more advanced processor – G4 against G3 – and a number of other improvements. It’s even cheaper, coming in at C$1249 instead of C$1999. But it doesn’t feel as good. The plastic is more obvious, and the bezels around the display look junky. Perhaps this is a little silly, but my enjoyment of the machine is just a teeny bit diminished by this. It’s too bad.

Meanwhile, another glitch has turned up, though this is my own fault. Just before sending the old iBook in for repairs I backed up the content of the laptop’s hard drive. Now it’s time to restore the content–onto the new machine–and I’m having trouble doing it. Apple has a very nice process set up when you start up the machine in which you are asked if you are upgrading from a prior Mac, and, if you are, you are given instructions on how to migrate your data from one machine to the other. The only problem is that it assumes you still have access to the old machine, which of course I do not. I’ll have to try another approach. But not tonight.

Later: It turns out I can also migrate–not restore–to the laptop using the backup image as long as I can mount the image on the laptop. Right now the image is sitting on the upper partition of a 160 Mb drive and can’t be seen by the laptop, because when I mount the drives in target mode on the desktop, only the first 128 Mb of the drive are visible. I have a driver on the hard drive which makes the entire drive available in regular use, but it doesn’t engage in target mode. I’ll work around this…later.