Fri Sep 24 2010 6 pm at Chatkhara
- Umair Asim
- Hassaan Ghazali
- Irfan Ahmed
- M. Ali
- Dr. Farhan
- Ahsan Khursheed
- Maroof Mian
- and myself attended.
- LAST will conduct its own public events, independent of KSS.
- Maroof will get the required signatures for registration after Hassaan gives him required papers.
- Umair will send LAST logo to Hassaan, it will feature a telescope.
- Outreach events in rich schools result in few questions from audience. Will try to do events in not-so-rich schools.
- Suparco will be asked to conduct event in Model Town Park instead of Iqbal Park.
- High altitude jet streams travel to East, not West. So no danger from India.
- 100 galileoscopes arrived in Karachi. 40 Suparco, 30 KSS, 30 Society of Sun.
- For distribution to institutions, not individuals.
- One will go to Museum of Science and Tech. to become an exhibit.
- One for Lawrence College Ghora Gali, one for Abbotabad Public School.
- Leo meteor showers will be watched at Hassaan’s place in November.
- Hassaan loves his 12×60 Skymaster. It is leaking oily stuff and needs some adjustments to prevent double vision. He has been very busy bird watching and identifying.
- His dog is no longer afraid of water and now there are two, not one dog.
- For asronomy, best bino is 15×70 and best telescope is 5″ minimum.
- Hassaan was about to buy a dob but its sensitivity to feather light touch made him back away at the very last moment. He will get an SCT goto like Omer’s, which is sturdy even with general public observation.
- Dr. Farhan will compare a high end 12×50 with a much cheaper 10×50 and decide what to buy. After that he wants a telescope.
- Umair and Hassaan have used binos on motorway to see patrol cars in advance.
- KSS collected s few thousand dollars as donation recently, after LUMS event.
- KSS wants equipment for a mobile telescope, to spare Umair’s C14. They asked him to suggest equipment within 1700 dollars.
- At LUMS, KSS people unpacked C14 carelessly, scratching IR and another filter.
- LUMS event did not collect enough donations.
- LAST needs a permanent address and business cards. Then membership will increase.
- Next meeting will be in Oct start, at Suparco event.
- M. Ali can easily arrange any outreach in Modle Town Park.
- He is not on the look out of some telescope. He and Hassaan are saving cash for telescopes.
- Ali Chawla is about to get married soon.
- Irfan Ahmed has a collection of astronomy videos. He wants me and Umair to do events in Lahore Grammer School. He says that a lot of stuff is available at Torrent.
- Umair will give a few audio books to Hassaan, to be heard on iPod during driving. During one book, Umair has to stop his car to listen, it was so good.
- Umair loved Okara and Shahdara events due to kid participation and questions. Flood of endless questions.
- Hassaan is working with US Aid. He said that rebuilding is not coordinated. Plans get stopped and remade.
- The food at Chatkhara was too expensive. M. Ali paid for everyone and took Hassaan by surprise. I made a remark which I regret. Im best off with my mouth shut.
- Hassaan dropped one green laser which exploded. I was happy as I wouldnt have to pay 1500.
- Questions Questions.
- Why was I living alone? For clean air, nothing else.
- Rent? 2000. Cheap.
- Why was I always wearing shalwar kameez? Dont have wardrobe at the new place.
- Was I looking into peoples homes with binos? No.
- Umair showed his Jupiter moon picture on his phone. Cool.
- Some light stuff….
- One student asked why dont stars have five pointed spikes.
- Hassaan will say a few words to his driver of the extra long limosine. Why didnt he pick him up from Chatkhara?
By: Ali Khan
The power of a telescope is not entirely dependent on the aperture alone, but many factors come into play. For example a 4″ apochromat will far outperform a 6″ achromat or even an 8″ Dobsonian. It will stand closer to perhaps a 6″ Maksutove-Cassegrain or SCT. An 11″ Newtonian with Zambuto optics mirror has been known to beat 18″ aperture in clarity and contrast. The sturdiness and smoothness of the mount also plays a role. Same OTA will work more efficiently on a GIRO-3 mount than on an Alt-Az mount (personal experience).
Quote: a 4″ apochromat will far outperform a 6″ achromat or even an 8″ Dobsonian. It will stand closer to perhaps a 6″ Maksutove-Cassegrain or SCT”.
Oops! Akbar bhai, you’ve made it too generic. A 6″ long-focus achro can beat the hell out of a 4″ f/6 apo, depending on the target. Yes, the 4″ apo will rule when you’re talking about wide-fields, but talk of the planets, luna, many planetary nebulae and DSO’s the long f-ratio and greater light gathering of the 6″ will simply overwhelm the 4″. It will also excel at splitting tight doubles.
Outperform an optically excellent 8″ dob? Cummon dear.
A 4″ apo will easily beat a 6″ SCT or MCT on most targets. But talk of a cooled 8″ MCT on a good night, and that’s a different story.
That’s true about the Zambuto mirror; the story is on his website. He says:
There is brightness, which is provided by aperture, and there is contrast, which allows one to see detail. I have been accused of overstating the importance of contrast, so please let me be clear. “Contrast is not everything. Outside of aperture, contrast is the only thing”.
So, there are many circumstances when the adage “aperture rules” holds.
For the record, I’ll take a Zambuto 8″ anytime instead of a 4″ apochromat. Make your offer!
An 8″ MCT is a gem. I am talking of a comparison with an 8″ simple newtonian dobs with a 4″ Apo. That is why I said a 4″ apo may stand closer to a 6″ MCT but I didn’t go anywhere near the utmost respectable 8″ MCT.
Akbar bhai, I’m also talking of your comparison of an 8″ Newtonian and a 4″ apo. Assuming both have accurate figures and properly acclimated, the apochromat stands no chance other than for very wide field views.
Zain, we are not exactly talking about accurate figure here, because, based on my very limited knowledge, this is what makes telescopes of different genre different from each other. For example, a single lens telescope has chromatic aberration (Like the ones I hade made, vis a vis, SK’EYE-1,2, and 3). In such telescopes, at high magnifications, you can clearly see the fainter star’s image in form of concentric circles colorful spikes spread at an area. That decreases the net resolution of a telescope as the image of a dim star gets even dimmer because it is spread at a larger area. An achromat solves this problem to some extent by focusing most of the light rays of differing wavelengths to a much smaller area, but still not pinpoint. An apochromat solves this problem further and brings nearly all the light to a single pinpoint. Hence, it will show fainter objects than an achromatic lens by a simple trick of bringing all the light to a smaller area. (Tip: galaxies are not visible to naked eye because even though they are apparently large on the sky and overall brighter than many visible stars, their light is diffusely spread at a larger area than a star, hence invisible.)
Mirrors face a slightly different problem of spherical aberration. A plane concave mirror shows stars as elongated comma like shapes. Parabolic mirror (commonly used for Newtonians) solves this problem to some extent but the comma problem remains to some extent, hence the starlight is still spread over a certain area. Other modifications like Schmidt or Maksutov correcting plates, or RC design etc, aim to solve the comma problem and bring all the light to one pinpoint. (remember, mirrors do not suffer from chromatic aberration). So the resolutions of different designs of same aperture diameters are different…hence the price too. An apochromat is not all about the wide field, it is also about increasing the resolution in a given diameter.
“Alt-Az” in the last line…read equitorial mount 🙂
I mean equatorial
Who eats that BURGER ? :O If you call that a burger… :O
Laser pointer exploded? Oh.. hm, must be a cheap one I guess.
“One student asked why dont stars have five pointed spikes.”
Hah, how did you respond to him? 🙂
Stars don’t have pointed spikes because gravity pulls all the matter towards the core causing the star to be shaped like a ball rather than a spiky thing.
Good reply! I cant think of anything with 5 pointed spikes o_O it was a strange question I thought.