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Skywatcher 80ED OTA PRO on an AZ-3
The Purchase
I recently purchased my second real* telescope for astronomical purposes. The Skywatcher 80ED OTA PRO is an 80mm F7.5 Apochromat Refractor and quite simply a beautiful little machine. I've put this scope on a solid Altitude/Azimuth mount and it will back up my 6" Newtonian Equatorial as a smaller more portable scope for the quick or mobile observing sessions.
The 80ED comes with a travel case, a 9x50 finder scope, tube rings, and a 2" crayford focusser. Assembly is quick and easy making it convenient to properly store the scope in the case between observing sessions. All parts are solid and well made, giving, if nothing else, a warm fuzzy feeling of confidence in the machine!
First Light
With predictable timing the 80ED arrived just before full moon, so, combined with the light pollution around my home, first light felt like an anti-climax. However, with some run-of-the-mill mid range Plossl eye pieces, the the views of the moon, Jupiter, Saturn, Crux and Orion were superb, with no hint of false colour or image aberrations and both planets showing faint surface detail. After several happy hours I remembered to go to bed before work the next day! The first night left me feeling excited about this little scope!
The Alt/Az Mount
Skywatcher recommends the pro series apochromats be put on an equatorial mount for star tracking and photography purposes, however I was after a good quality portable scope on an Alt/Az mount for simple visual star hopping while my 6" Newtonian EQ did other stuff. The whole setup needed to be light weight, compact, and quick to setup and use. I chose the Skywatcher AZ-3 mount with fine motion controls.
The first thing one notices about the AZ-3 is that at angles higher than around 60 degrees, the altitude bearing needs to be under significant tension to prevent the scope falling backward due to an off center of gravity. This tension results in a stiff altitude action. The AZ-3 mount really needs a counter weight to shine, so for around $10 at my local hardware store (nothing more than threaded rod bent in a vice, two holes drilled in the mount, and some nuts and washers!), I added one. The weight in use here is temporarily nicked from the 6" Newtonian EQ's mount; it is a little heavy for the 80ED and thus the moment a little short here, but the counterweight system still works well leaving the altitude bearing loose with a nice, smooth action. Next purchase: a smaller counter weight.
The AZ-3 also deserved a little service and cleanup after delivery as the manfacturer's idea of lubrication seems odd. I quickly stripped it down, cleaned it, regreased everything and reassembled to get very smooth operation with barely noticeable backlash and stick. I think I will also be changing the aluminium tripod to wooden legs in the near future to damp down the last bit of mount vibration.
Finally...
The Skywatcher Pro series refractors seem like great telescopes for a mid range budget. I have a very critical eye so putting one of these scopes (instead of a cheaper sibling) on an Alt/Az mount for visual observing might be considered an overkill for some. But, the 80ED feels like it will be my favourite companion for the quick astronomy sessions for many years to come, and wonderful in the second fiddle role for the more serious astronomy meets.
Night!
* I once had a horrid little 60mm refractor, purchased from a nameless department store, that very nearly turned me off astronomy for life. My 6" Newtonian EQ eventually made me feel much better, but I still have nightmares...
cPanel Parked vs Addon Domains
Recently I started using a web hosting company that uses cPanel providing only Parked Domains and not Addon Domains. As you may know, a Parked Domain allows people to surf to a website via a secondary domain name (basically just a website alias) while an Addon Domain has its own separate location on the webserver acting as a different website on the same hosting account.
Being quite ready to use an Addon Domain or two this lacklustre service disapointed me! Upon further investigation in retrospect, the hosting package description and the T&C appeared conveniently vague on the subject. Not to be deterred, Apache's mod_rewrite allows one to get around this little hurdle quite simply by using the following .htaccess file:
Options FollowSymLinks
RewriteEngine on
RewriteCond %{HTTP_HOST} alpha\.net
RewriteCond %{REQUEST_URI} !^/alpha\.net/
RewriteRule ^(.*)$ /alpha.net/$1 [L]
RewriteCond %{HTTP_HOST} beta\.net
RewriteCond %{REQUEST_URI} !^/beta\.net/
RewriteRule ^(.*)$ /beta.net/$1 [L]
This invisibly transforms a URL:
http://alpha.net/ --> http://alpha.net/alpha.net/ http://beta.net/ --> http://beta.net/beta.net/
And results in the following directory structure:
public_html/ public_html/.htaccess public_html/alpha.net/ public_html/beta.net/
Easy!
1/10 of a Picture
Random words pulled from the internet create a far more interesting day dream than real sentances :-)
Raven: A Scripting Language for MySQL
I've been using a home grown scripting language called Raven for a couple of years now. I think it is a good tool for working with MySQL, particularly when one needs to crank out a quick script on the fly using simple and readable code. Currently it spends a lot of time talking to my cluster. Here are the basics...
Connect to the Database:
'mysql://user:password@localhost/test' open as $mysql
Select some records:
'SELECT * FROM mytable' $mysql query as $result
Get the number of selected records:
$result selected as $num_rows
Iterate over the result set and output a CSV:
$result each as $record $record ',' join print "\n" print
Insert a record and return the last AUTO_INCREMENT value generated:
'INSERT INTO mytable (first_name, last_name) VALUES ("Sean", "Pringle")' $mysql query inserted as $record_id
Retrieve a single record into local variables:
'SELECT first_name, last_name FROM mytable WHERE id = 10' $mysql query fetch values into $first_name , $last_name
Update some records:
'UPDATE mytable SET field_1 = 10 WHERE field_2 < 100' $mysql query as $result
Get the number of records affected by the update:
$result affected as $num_rows
The astute among you may have recognised Raven uses Postfix Notation, and although it isn't very obvious here, Raven also uses whitespace to define code blocks (a la Python). The core library is made up of short functions using only English words and because I only care about talking to MySQL I can use:
- query instead of mysql_query
- fetch instead of mysql_fetch_array
- selected instead of mysql_num_rows
- inserted instead of mysql_insert_id
Ahhh, the luxury of simplicity...
The Raven engine is written in C and compiles to a very small (for a scripting language! ~100K) standalone binary on Linux.
Postfix Notation and significant whitespace are not everyone's cup of tea, but I think the result here is quite elegant, particularly in combination with SQL which tries very hard to emulate natural langauge. And at the end of the day, I figure there are already plenty of people following the herd and using the well known scripting languages, so I might as well go have fun some place nobody else is :-)
MySQL Cluster @ Home
I'm building a MySQL Cluster which you can see pictured on the right. Partly it is for serious learning and testing purposes, and partly because it is winter Down Under and this keeps the office warm. The smallest desktop box goes particularly well under the desk as a heated foot rest :-)
- Management Node: PIII 700 Dell Laptop mal (My old faithful laptop.)
- SQL Nodes: 2 x PIII 800 Dell Optiplexes inara, river (Optiplexii? Different form factor, doh! How messy. Had these two boxes laying around the office already.)
- Data Nodes: 4 x PIII 1GHz clone boxes w/ 512Mb RAM simon, jayne, book, wash (Found these boxes cheap at an ex-gov computer market. Another 1Gb RAM each on order - how rare SDRAM is becoming - for some DataMemory breathing space.)
I have several other machines that participate sometimes, bringing the cluster size to 10. However this 7 box configuration is the usual size. In the long term I have a half height 19" rack salvaged from a University skip which I hope will eventually hold the data nodes. All that is lacking is a supply of ply board (a la early days at google) to act as shelves. Once storage is more compact I can start increasing the number of nodes.
Ah, gotta love the heat and noise... I think come summer time I will be moving this thing into the basement...
