- Star Party Etiquette: Cocktail dresses are out. But what’s in?
- Sidewalk Astronomy Tips: What to expect and do.
- General Observing Tips: How the get the most of what you look at.
- Hand Scale: How to use your hand to measure angles.
- Astro Links: Astronomy Links
- Astro Humour: Just because we’re silly.
- Individual OAFs personal opinion pages
I’m an OAF and also a member of the Ottawa Centre, RASC. I particularly like Sidewalk Astronomy and Outreach.
Web Page Tech Stuff
I’m the technical contact person for this web page — contact with the ISP, installer of the content management software, administrator of the database, etc.
Astronomy Writings and Wramblings
Recently completed articles:
Based on feedback, the article that has been popular and seems to have been useful to a number of people is
Astro Suppliers that I like
Mail order places
- Astro-Physics Send me two of each, please.
- TeleVue For eyepieces
- Telescopes Normand Fullum Makes fine mirrors. Better known for making telescopes for the “Harry Potter” universe
- Starstructure Telescopes Aluminum bigdobs that damp better than wood.
My Rabid Opinions on Telescopes
- Larger aperture scopes show more detail and fainter detail than smaller scopes in *all circumstances*.
- It is a myth that smaller scope do better in poor seeing.
- It is a myth that smaller scopes do better in light pollution
- It is a myth that larger scopes have “diminishing returns” over smaller scopes under light pollution. Actually, the ratio of performance is constant.
- However smaller scopes are better than larger scopes because
- Smaller scopes are more transportable. The scope you have with you is better than any scope you left behind. The scope you use the most is, by definition, the best scope you have.
- Smaller scopes cool down faster. At least half of the time people have complained about “poor seeing”, it was actually tube currents caused by warm optics.
- Larger scopes are more work to collimate. Some small scopes, like quality refractors, never need collimation. Large truss scopes must be collimated every night and in some cases, re-collimated more than once per night.
- Large newtonians, particularly truss-tube newtonians are poorly baffled. So light from local light sources can sometimes directly illuminate the focal plane greatly reducing contrast. On the other hand, small refractors tend to be very well baffled and can show very much better contrast than larger scopes when there are local light sources. (This difference may be the basis of the “smaller scopes do better in light pollution myth”.)
- Small scopes have a larger field of view. It doesn’t matter how long a focal length eyepiece you use. The true field you get on the sky is determined only by the focal length of your primary and the diameter of your focuser. A 25 inch scope cannot get more than about 1 degree on the sky, whereas most 4″ scopes can get over 5 degrees. The result: open clusters look far better in the 4″
- Small telescopes and large telescopes do different things well. No single scope does everything well. One telescope is never enough. (The real problem is explaining to S.O. why you need 13 telescopes. 🙂 )
- An off axis mask, to eliminate “central obstruction” does not improve the view in any seeing conditions.
- Actually, if it does, it means that you’ve got poor optics. (Did I mention this was the place for my *rabid* opinions.)
- If you live in an environment like Ontario, big telescopes need to be actively cooled *all night long*
- It’s a myth that one needs to cool a 20″ or larger dob primary for “an hour” and then it’s ready to use.
- In my experiments where I actually measured the temperature of my 25″ primary and the surrounding air I found:
- # a 1 degree C difference between mirror and air was enough to visibly degrade detail on planets
- # after the mirror came to thermal equilibrium, if I then turned the cooling fan off, it would take only 20 minutes for the air to again out-cool the mirror so that there was again a 1 degree C difference and thefore degraded planetary detail.
- The moral is: learn to know when your mirror needs cooling. (see next rabid opinion)
My Rabid Opinions on Weather
- Many times people complain about “bad seeing” the problem is actually warm mirrors. It is possible to learn to tell the difference if you have a newtonian with an open mirror cell. Try this experiment (the Wirths-Danko demonstration):
- While you look though the eyepiece at an out-of focus star (looks like a donut), have your buddy turn on a box fan which is pointed at the back of your mirror. Any change in the ripply pattern you see in the eyepiece is tube current and not seeing.
- In an out-of-focus image of a star, tube currents move slowly, are swirly and seem to know that your telescope is round.
- In an out-of-focus image of a star, true seeing zips quickly straight across the donut and does not know that your telescope is round.
- The jet stream is *not* the major cause of bad seeing.
- Three years of careful experimental work by Allan Rahill has shown that the presence of the jet stream above is correlated with bad seeing to only 30%
- The other 70% of coreleation is to wind shear in the bottom few thousand feet of atmosphere.
- Don’t depend on jet stream maps plan observing. Use Allan Rahill’s seeing forecast or this shortcut to it.
- Weather for astronomy, in southern Ontario sucks. (That’s the technical term.) The south-west USA and north-west Mexico get 3 to 4 times the number of deep-sky observing hours that we do.
My Rabid Opinions On Observing
- There is a least a 2 magnitude variation in sensitivity of eyesight from person to person. So questions of “limiting magnitude” are at best theoretical.
- There is a wide variation in color sensitivity from person to person. This is hard to measure, but judging by how much more aperture I need to see color than Mike Wirths, I’d say a factor of 2 variation is not unreasonable.
- To me, the difference between astrophotography and visual observing is exactly like the difference between my SO yelling at me for observing to much and a picture of my SO yelling at me for observing to much. (Lurid alternative deleted for family audience.) There is a difference in emotional response. As a result, I will always prefer a poor visual view to a great photograph. However, I’ve often get visual views that stun astrophotographers (I have a 25″ scope). I’m happy to look at other people’s astrophotographs and can appreciate the great effort it takes to make a good image. But I don’t have the patience to do astrophotography myself. I prefer to spend my limited time looking though telescopes. Being a visual only observer is rare in this hobby.
- I don’t keep an observing log. I used to. But then I found that I never went back to read it. I figure there is no point writing something if noone will ever read it. Fairly silly of me. Each of my rabid opinions, above was learned from observing experience. Had I kept my logs, they’d be scientific observations rather than blather.
Other internet stuff I’m to blame for
My name is Allen. I’d say I am an advanced newbie at hunting photons. Being a practicing social misanthrope but falling short of anarchist, OAFs suit my sensibilities, sort of an aloof democracy.
To be honest I have not run across an astronomy shop that did not have integrity (well one, but they are gone now). The astro community is small … and we love to gossip (and bitch about the weather, … but of course it’s Attilla’s fault). Disreputable shops will not last long. Some are better than others of course in terms of knowledge and service, but nobody will outright stiff you. Just remember: If it is not in stock, anything you order will only take a week or two (ummm … for them to get around to ordering it, then it can be anyone’s guess after that).
Shops I have dealt with and like:
- Lire La Nature in Montreal
- KW Telescope in Kitchener
- Adirondack Astronomy in Hudson Falls NY
- Ken Dauzat in Texas. Great source for Synta clone mount accessories (i.e. EQ5/6, Sirius/Atlas, CG5, etc …)
Useful Free Astro Software
- CCDCalc: very nice image scale evaluator for astrophotography
- Aberrator software that allows you to study various optical problems with telescopes
- Exposure Calculator software that gives you a rough idea of exposures required for astrophotography (first link)
Books I can recommend
- NightWatch: A Practical Guide to Viewing the Universe (Spiral Bound)
- ISBN-10: 155407147X
- Possibly one of the few must have books for the starting astronomer. Well written, easy to read, great for kids, and very well illustrated. It covers everything a beginner needs to know to “get out there”. Solid info on equipment to purchase, simple charts to identify the constellations and find objects of interest. Highly recommended.
- The Backyard Astronomer’s Guide (Hardcover)
- ISBN-10: 155209507X
- By the same hoodlums as above. It is similar as well, but with much wider scope, with far more detail about everything. An amateur’s should have. Also very well written and is easy to read by everyone, tons of beautiful pictures. It is non-pretentious and even engaging. A great coffee table reference.
- Star Watch: The Amateur Astronomer’s Guide to Finding, Observing, and Learning about Over 125 Celestial Objects (Paperback)
- ISBN-10: 0471418048
- This book covers first objects you will look at when you start out in astronomy. In fact for the majority of the time in most urban environments these are the objects you will be coming back to again and again (come on, who gets bored with M13?). It helps you locate them and tells you what you will see in binos, and in small and medium telescopes. Rates the objects by WOW factor and finding difficulty. A really good clever practical guide to start your observing adventures.
- Celestial Sampler: 60 Small-Scope Tours for Starlit Nights (Paperback)
- ISBN-10: 1931559287
- Another really good guide for the beginner, directed to small telescopes and perhaps binoculars.
- Introduction To Digital Astrophotography: Imaging The Universe With A Digital Camera (Hardcover)
- ISBN-10: 0943396832
- Detailed and technical, but well written and easy to read, and very well illustrated. It has broad scope, covering everything to do with digital astrophotography. Detailed pros and cons of the equipment and software you will need and use to get into astrophotography. It goes into techniques and procedures with your scopes and software. A real leg up, and an excellent guide and reference book you will read several times and refer to often.
This is a list of OAFs persoanl web pages. There they get to voice any opinion they like withought without having to seek the consensus of a bulk of OAFs.
- All posting to Individual OAFs page must be civil.
- Be polite. No editing someone else’s personal page.
- If you want to comment on a OAF’s individual page, use the Comments field, or better post to OAFuscators.
- There is no rule 4.
- You can’t blame the bulk of OAFs for the opinion of just one OAF.
Individual OAFs Opinion Pages
Not to be taken too seriously. In alphabetical order:
Ottawa Astronomy Clubs & Groups
- Ottawa Centre of the Royal Astronomical Society of Canada
- Ottawa RASC Mailing list for discussing and planning outreach events.
- OAFs (You are here)
Astronomy Web Sites and Blogs
- Wikipedia’s entry on Amateur Astronomy
- Phil Plait’s Bad Astronomy blog
- Richard McDonald’s Astronomy Writings for beginners
Astronomy Discussion Groups
Equipment Information Sites
- Articles on Andy’s Shot Glass. We like the video tutorials on this site. But we have no opinion as to whether it’s a good place to buy from.
- Astrophotography with Canon DSLRs Of course he hopes it will inspire you to buy his books but we have no opinion on that either.
Free Astronomy Software
- Carts du Ciel Star Charting / Planetarium software.
- Stellarium Multi-platform Planetarium Software (PC, Mac, Linux).
- RegiStax Image processing software
- PLOP automated mirror-cell designer
- Virtual Moon Atlas superb moon atlas software
How to Buy A Telescope
(Actually, we recommend you *don’t* buy a telescope. Instead, come to our star parties and try the different types of telescopes. Buy when you know what you like and dislike about different models.)
- Cloudy Nights equipment reviews
- Ed Ting’s scopereviews.com
- Todd Gross’s short telescope reviews
- Sky News Magazine telescope reviews
- Northern Virginia Astronomy Club scope reviews
- Excelsis equipment reviews
Buy & Sell Sites
Forecasts and News
OAFs, the Ottawa Astronomy Friends group, has done a much-needed refresh of its web page. Welcome to the new site. Please forgive the dust while we finish construction.
Any “OAF in good standing” can add articles or edit pages on this site. Ask for an Editor ID on the OAFs mailing list.