Find us on Google+ Astronomy Box: November 2012

26 November 2012

To Planisphere or to App-isphere? - Astronomy apps

One of the most recommended pieces of equipment to buy when starting out in astronomy is the humble Planisphere.

Planisphere Wikipedia
Although these are very quick and easy to use, not to mention cheap, a lot of us now own smartphones. Off course, smartphones aren't cheap in any context but they are never the less part of our lives now and the chances that a new amateur astronomer owns one are high. With this in mind, I decided to list off some of my favourite apps that I like to use when doing astronomy. I must mention that this list will be totally biased towards Android, although I know that amazing apps do also exist for iOS.

1. Weather apps

A good place to start is weather forecasting apps. Without clear skies there is no astronomy, at least in the optical sense, and to know what the weather is doing a few days in advance in invaluable for planning your observing or imaging sessions. To say that I have trialled a few weather apps, would be an understatement. I've gone through AccuWeather, Weatherbug, you name it, but the only one that really stood out from the crowd is a fantastic little app called Astro Panel by Shibby Developments. I have already covered the features of this app in a previous article, but it has a solid position in my list and deserves another mention

Screenshot of Astro Panel on my phone. This was during my visit to the Mt Teide Observatory, Tenerife.

2. Planetarium apps

Being an Android user there are really only two choices to consider when looking for a decent planetarium software, Google Sky Map Devs Sky Map and Harshad RJs SkEye. While Sky Map is a perfectly good planetarium app with lots of great features and searchable objects, not to mention being the first one I used, I'm going to show preference to SkEye. The main reason for this is that I encountered a lot of glitches in Sky Map when searching for objects in real time, and the planetarium would be misaligned from the true sky. I don't know if it was an issue with my phone or the current OS at the time, but it made me search for something better. Something better came in the form of SkEye.

Screenshot of SkEye, looking at the constellation Orion.
As you can see from the screenshot, there is a wealth of information on-screen when trawling through the sky, much more in fact  than Sky Map has to offer. The simple displaying of right ascension, declination and other coordinates shows that this app is made for the serious amateur. Another great feature is that magnitudes for celestial objects are also provided.

Don't get me wrong, Sky Map is a great app. However. if you are an Android using amateur astronomer and want an app that is useful beyond simply locating objects in the sky, SkEye is the one for you. I cannot vouch for any of the planetarium apps on iOS platforms but I have been told that they run very smoothly and are very reliable. As to features, you'll need to talk to an Apple fan.

3. Compass apps

 The next couple of apps I'm going to discuss, I use mainly for mount set up. Compass apps are very useful, and come in all shapes and sizes. However, the compass I chose is actually part of a package app containing a number of different navigation and positioning apps. Ulysse Gizmos by binarytoys has an array of interfaces, including a very detailed compass.

Screenshot of Ulysse Gizmos on the compass interface.
As well as finding your bearings, it also measures your altitude which is important for many GOTO systems that may not have GPS included, and require the manual entering of these coordinates. Another feature shown in the screenshot hints at my next chosen app for use in astronomy and the reason why I chose Ulysse Gizmos.

4. Spirit Level apps

Getting your mount level and polar aligned is in most cases essential, especially when using GOTO systems and doing high focal length astrophotography. Whereas some do, many mounts don't come with built in spirit levels. The solution I came up with was using a spirit level app on my Android phone and placing the phone onto the accessory tray of my HEQ5 Pro while levelling it. The Ulysse Gizmos spirit level works great. Since doing this my mount alignment has been very satisfactory, enabling unguided subs of 1min and being perfectly adequate for 5min+ guided exposures.

If for some reason, like me, you'd like to have a simpler dedicated spirit level app on your phone, I would recommend Bubble Level by Antoine Vianey.

Screenshot of Bubble Level
With this super simple interface and high resolution spirit level, aligning and levelling your mount is easy as pie.

I hope this list might make some ones observing or imaging life a little easier, and I might add to it in the future. Also, watch out for another future article on a very handy little modification I made to my smartphone that I use every single night I go out to observe or do some astrophotography.

For now, clear skies.

21 November 2012

Off Axis Guiders and Light Pollution Filters

Most of the time, I live in a moderately light polluted area. Like a lot of us, I use a standard light pollution filter to counteract the effects of sodium light and other artificial light when I'm doing my astro-imaging. Recently a new friend of mine explained to me that although they do a pretty good job of dealing with light pollution, they also filter out some of the light from stars and other astronomical sources, particularly in the red spectrum. After comparing some of my own astro-images with those of other astrophotographers, this became apparent, and I noticed that some of the stars in my images that should have been redder had been desaturated.

Obviously, no filter can ever replace a proper dark sky, but my friend very kindly pointed me to a certain type of specialised light pollution filter called a IDAS LPS filter. This filter, produced by Hutech, has much better colour correction. It lets all the important light through, while filtering out that unwanted light pollution, and without introducing that characteristic blue/violet tinge associated with cheap LPR filters.

Researching the IDAS LPS I noticed that many Nikon users were having trouble finding CLS versions of this filter, which clip into your DSLR before it gets attached to your imaging train. The benefits of this is that you can have your filter behind your off axis guider instead of in front. With a filter in front of your OAG it could darken already faint but usable guide stars. Now, I did find a Nikon CLS version of this filter. Only thing was, it was quite expensive and quite a bit more than the regular 2" filter. 

I took a look at my Nikon T-ring and noticed that it actually had a groove in it which would accommodate 2" filter glass. Thus, the solution presented itself.

Nikon T-ring and standard 2" LPR filter
I simply removed my LPR filter from its cell and inserted it into the T-ring. This is something I haven't seen done anywhere and thought perhaps people weren't aware of it, that being the reason for this article.

The 2" LPR filter glass inserted into the Nikon T-ring
The procedure was quite straight forward, needing only a small hex key and a small minus screw driver to unscrew the filter cell. 

In doing this I have come up with two solutions. I can now use my standard LPR filter behind my off axis guider, and when I'm ready to purchase the IDAS LPS, I can go for the cheaper 2" version and do the same modification.

So, thanks to Pawel for putting me on this train of thought.

13 November 2012

DSO 5 - M45 Pleiades Cluster (Colour)

A slight improvement in processing, and now in glorious Technicolor.

I managed to retain the colour information from the Nikon RAW NEF files by simply saving the images as TIFFs in Photoshop before processing them in Nebulosity.

OTA: WO 72mm Megrez w/ Moonlite Focuser & SkyWatcher FF & LPR Filter
Mount: HEQ5 Pro
Camera: Nikon D3100 14.2mp
ISO: 1600
Lights: 15x60sec
Darks: 15x60sec
Flats: None
Bias: None
Processing: Nebulosity
Post-processing: Photoshop

8 November 2012

DSO 4 - M45 Pleiades Cluster

We got a nice clear night recently and I managed to get some pretty satisfactory
data of M45 to go with my new copy of Nebulosity.

I'm having a few initial niggles with processing the raw data from my Nikon D3100, but I'm quite pleased with what came out the other end.

OTA: WO 72mm Megrez w/ Moonlite Focuser & SkyWatcher FF & LPR Filter
Mount: HEQ5 Pro
Camera: Nikon D3100 14.2mp
ISO: 1600
Lights: 15x60sec
Darks: 15x60sec
Flats: None
Bias: None

Basically, my stacked results of M45 are coming out pretty much monochrome although the blue nebulosity is clearly visible in the raw images. I'm obviously doing something wrong in one of the steps. I'm following Craig Starks tutorials on the Stark website. Hopefully I'll be able to iron out these issues soon, and show the seven sisters in all their reflective nebulosity.

Also, part two of my Tenerife trip to come shortly. 
Apologies for the delay.