Autoguida - Tecniche avanzate

András Dán, MSc, Gemini, Nov. 2012.

Traduzione italiana a cura di Alessandro Di Giusto

Introduzione

E' il momento giusto per avviare un approccio sistematico a questo settore molto importante dell'astrofotografia, in maniera tale da ottenere il massimo dalle nostre costose montature, telescopi di guida, camera di guida e camera di ripresa principale.

Lo scopo di questo documento, pensato per novizi ed esperti, è di aiutare nella comprensione del processo di funzionamento dell'autoguida e ottenere così il miglior risultato possibile dai vostri sistemi.

L'autoguida è sostanzialmente il tentativo di inseguire il cielo con un errore inferiore a quello riscontrabile, in base al rapporto scala/pixel, sulle riprese del sensore principale. Mentre cerchiamo di correggere gli errori della montatura ignoriamo la dilatazione delle immagini stellare introdotte dal seeing, (salvo che non si usi un sistema di ottica attiva ad alta frequenza)

Iniziamo creando una lista dei giocatori che parteciperanno alla partita.

Stella guida - la sua posizione sul sensore di guida viene misurata

L'articolo completo si trova qui: www.geminitelescope.com/autoguida_gemini.pdf

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Hi,

as you can see from the image above, some languages are lagging behind a little. Would you like to help AstroBin by contributing to the translation to your native language? It's easy!

Go to the localization server, and create an account. Then click on your language, then a project, and start translating!

Remember to click on the Submit button instead of the Suggest button, so your translation won't need approval from another translator.

And if you have any questions or trouble, just let us know!

Thank you!

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2012 was the first full year of AstroBin's life, as the site was launched in November 2011. So let's wrap the year up. Almost 200,000 people visited the site, totaling almost 4 million page views!

That's way beyond my expectations, so it was a great year!

I would like to give a huge thanks to:

• The 20+ people who have helped translate the site to 13 languages. We are all indebted to them. AstroBin contains around 10,000 words, so it was no picnic.
• The dozens and dozens people who have helped by reporting bugs, and making requests. A lot of the best features of AstroBin have been suggestions coming from you users.
• All those who have been active with AstroBin Questions, the Q&A website for astrophotography, who have helped create a small community there.
• Carine Souplet of Astronomie Magazine, a French publication, and Luigi Fontana of Nuovo Orione, an Italian publication, for writing and publishing articles about AstroBin.
• Every one who has blogged about AstroBin, or put a link on their website, or talked about AstroBin with their club members or other friends.
• Every single one of you for doing a great job with not abusing the site. There hasn't been a single incident.

Thank you all and a happy and clear 2013!

Tags : stats year-recap

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It's with deep sadness that I share here the news that Giovanni Sostero has passed, after being striken by a heart attack.

Giovanni, class 1964, was very active in the research concerning minor bodies of our solar system, variable stars and supernovae.

He is the discoverer of eleven supernovae and one nova.

Giovanni was also very involved in public outreach, and has several publication in scientific journals. He was a very loved and respected astronomer, and will be sorely missed.

My personal condolescences go to this family and his friends.

Salvatore.

Tags : announcements

Discussions : 7 comments

Autoguiding – Advanced Techniques

András Dán, MSc, Gemini, Nov. 2012.

Introduction

It is time we take a systematic approach at this very important topic of astrophotography to get the most out of our expensive gear – mount, guide scope, guide camera, main camera.

The aim of this document is to help understanding the process of autoguiding and to get the best result possible with your gear. It is intended for both beginners and experts.

Autoguiding is an attempt to track the sky with smaller error than the pixel scale (smallest visible error) of our imaging (main) camera. While trying to correct mount errors we want to disregard seeing blur (except with active optics using high frequency).

Let's start by creating a list of the players of the game.

Guide star – its position on the guide chip is measured by the guide software at regular intervals, normally with a few seconds (1-5) of integration. The measured so called “guide error” is the result of mount tracking errors (refraction and mechanical errors) and seeing blur.

Mount – it tracks the sky as precisely as its polar alignment, software and mechanics allow.

Guide camera – it takes images of the guide star and sends them to the guide software for analysis.

Guide scope (separate) – images the guide star for the guide chip. In case of off axis guiding or dual chip camera we have no guide scope.

Guide software – this is the brain of the system, interprets the guide chip data and sends guide commands to the mount.

Main telescope – don't blame everything on the guider, the main telescope is half of the story

The process of guiding

It all starts with taking an integration of the guide star. Let this be 2 sec.

When finished, the image is downloaded and analyzed by the software, the centroid position is calculated (to 1/100^th of a pixel normally). Let this be 0.2 sec.

Read more.

Please download the pdf: www.astronomy.hu/guide1.pdf

Tags : guiding

Discussions : 4 comments

A while ago I set up a Facebook page for AstroBin, with the goal of promoting beautiful images uploaded to AstroBin on the popular social network.

Alas, I don't have time for that, so I would like to ask if anybody wishes to volunteer!

What do you need to do?

Volunteers would be granted admin privileges on the Facebook page, where they would post 1 to 3 images every day (in total, not per person), selected among all the images recently uploaded to AstroBin, with a short explanation (some words about the equipment used and some words about the object in the image.)

What are the qualifications required?

1. You have a very good command of the English language
2. You have been an astrophotographer for a while (so you have a good sense of what is a "beautiful" image)
3. You can write a few sentences about the equipment and the imaged object (you don't need to be a professional astronomer or anything, it's enough to just search for information online, like Wikipedia, APOD and other sources, and phrase an explanation in your own words)
4. You have about 10 minutes every day, or so, to do this (if there are many volunteers, then the amount of work will be even less!)

That's all! If you wish to help, send me a message by clicking here!

Thank you!

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Discussions : 1 comment

Last week I have launched AstroBin Questions, a community driven, highly interactive, wiki-capable website that you moderate, thanks to a system based on reputation points.

I've just written down a meta questions that explains how reputation and votes work, what they are and how they should be used. You can read it on AstroBin Questions, or here below. And by the way, if you are still wondering what AstroBin Question is, and why it's so important for the astrophotography community, read this: What is AstroBin Questions?

Introduction

This website works a lot differently than a forum. A good explanation about how this is not a forum can be found in the first meta-question asked.

This meta-question talks about reputation and voting.

One key reason why this website was made, was to provide the astrophotography community with a way to get correct answers to question, not just any answer.

Reputation and votes are the way in which the community moderates itself, and makes sure the best answer is on top.

What is the proper way to vote?

Every question, and every answer, can be voted up or down.

You should vote up if:

• You think the question is interesting
• You think the answer is correct or informative

You should vote a question down if:

• You think the question is off-topic, or too poorly worded to be comprehensible
• You think the question doesn't bring any value to the community, for instance because an answer could have easily been found on Wikipedia
• You think the question has already be asked in the past (in this case, please also leave a comment with the link to the old question)

You should vote an answer down if:

• The answer is objectively incorrect
• The answer is not substantial enough to actually answer the question
• The answer is not really an answer, but it should have been posted as a comment or as a new question (e.g. follow-up questions)

What's the role of reputation?

Reputation points are a way to express how reputable a person is in the community. Reputation can be earned and lost, primarily because of votes received.

When a person has a high reputation, people will know that they can trust their answers.

These are the primary reputation gain and loss rules, but bear in mind that the numbers might change in the future, if the community becomes larger:

• Maximum daily reputation gain per user: 200
• Gain for receiving an upvote: 10
• Gain for the author of accepted answer: 15
• Gain for accepting best answer: 2
• Gain for post owner on canceled downvote: 2
• Gain for voter on canceling downvote: 1
• Loss for voter for canceling of answer acceptance: -2
• Loss for author whose answer was "un-accepted": -5
• Loss for giving a downvote: -2
• Loss for owner of post that was flagged offensive: -2
• Loss for owner of post that was downvoted: -10
• Loss for owner of post that was flagged 3 times per same revision: -30
• Loss for owner of post that was flagged 5 times per same revision: -100
• Loss for post owner when upvote is canceled: -10

As you can see, users are rewarded reputation for actively helping to shape the community. If you accept an answer, for instance, you are rewarded 2 reputation points. Also, notice how downvoting will cost you reputation: this is because downvoting should not be done lightly, but in the spirit of bettering the community when this is necessary.

What can I do with my reputation?

Besides gaining respect in the community, reputation allows you certain privileges. These are the reputation points you need to perform certain actions (remember that these numbers too might change in the future, as the community grows):

• Upvote: 5
• Downvote: 50
• Answer own question immediately: 5
• Accept own answer: 20
• Accept any answer: 500
• Flag offensive: 5
• Leave comments: 10
• Delete comments posted by others: 200
• Delete questions and answers posted by others: 500
• Upload files: 10
• Insert clickable links: 1
• Insert link suggestions as plain text: 1
• Close own questions: 25
• Retag questions posted by other people: 50
• Reopen own questions: 50
• Edit community wiki posts: 75
• Edit posts authored by other people: 200
• View offensive flags: 200
• Close questions asked by others: 200
• Lock posts: 400

As you can see, after 200 reputation points, things start to get serious and you are allowed lots of moderation tasks. This is all in the best interest of the community, so we can have a website that has good, legitimate and correct content!

What does it mean to "flag offensive"?

Finally, you have the option of flagging posts (both questions and answers) as offensive. This should be used if the post contains spam, vulgarity or is actually offending to the community for other reasons.

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Today, AstroBin is one! It's been a great year, so this is a quick message to thank you all for the support, feedback, encouragement and help during the past year.

Thank you!

Salvatore.

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Discussions : 13 comments

I've just realized that some code I had introduced on October 26th caused a bug and some images would hang for a long time (or forever) as "still processing."

The bug has now been solved, but would you care to please let me know if you were affected?

Thanks and sorry about the incovenience!

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As most of you will have noticed, AstroBin has just launched a sister site, called AstroBin Questions.

AstroBin Questions is a Questions & Answers site focused on the quality of the content. The allowed subjects of discussion are Astrophotography and Astronomy.

AstroBin Questions was created because, as of today, the most common form in which astronomy communities exist is that of the forum. A 20+ years old concept, that doesn't scale well with massive amount of information, does a terrible job at organizing such information (in fact it barely tries), and presents a number of flaws.

AstroBin Questions address the problems forums have, and is a community driven, highly interactive, wiki-capable website that you moderate, thanks to a system based on karma points. If you haven't already, checkout the introductory page here: http://www.astrobin.com/help/questions/

In addition to this, I'd like to tell you that your image pages now have a large button: Request critique. Clicking this button will bring you to AstroBin Questions's "Ask a question" page. The page will be pre-filled with information about the image for which you clicked on Request critique.

This way, you can ask the community specific questions you may have about how to improve your acquisition or processing technique, in relation to that particular image.

Check out the help and faq pages on AstroBin Questions and join today!

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