Astromart

July 2, 2004 01:32 AM Forum: Telescope Making

curved vanes ??

what is the difference between the straight and curved spider vanes ?
How can I improve my 12.5" f/4.7 for planetary observation ?

Thanks,
Andre

July 3, 2004 04:47 AM Forum: Equipment Talk

widest field 2" ep for my 12.5" f/4.7 newtonian

Posted By Andre Moutinho

Hi,

I have upgraded my focuser to 2" and I would like to know which ep in the 30mm-40mm range should I use. I know that fast systems requires expensive eps. What about the BW ? What should be the longest ep I should use for this telescope ?

Thanks,
Andre

July 4, 2004 08:58 PM Forum: Equipment Talk

Reviews of the Burgless SWA eps ??

Posted By Andre Moutinho

Hi,

I would like to read some reviews of these eps series. Mainly on fast f/5 scopes.

Thanks !
Andre

July 6, 2004 12:11 AM Forum: Equipment Talk

Does curved vanes improve planetary observation ?

Posted By Andre Moutinho

I have heard that curved vanes removes star spikes caused by diffraction. But what about planetary observation enhancement ?
Do I have a real improvement in planetary observation using a curved spider vanes ?
Thanks,
Andre

July 6, 2004 05:16 PM Forum: Equipment Talk

5mm spider vanes thickness influence planetary res

Posted By Andre Moutinho

Hi,

My current 12.5" spider vanes are so thick (5mm) that I have calculated the area of the 3 vanes in front of the tube. The total area is more than 50% of the central obstruction caused by the 2.6" secondary. How does this effect planetary resolution ?
I´m planning to rebuilt it.

Thanks,
Andre

July 6, 2004 10:10 PM Forum: Equipment Talk

equatorial platform for dobs and astrophotography

Posted By Andre Moutinho

Hi,

What level of astrophotography I can reach using an equatorial plataform for a dob mount. I believe that for planetary imaging it should be OK. What about long exposure ? How long can I take a picture, for instance, in a 12.5" f/4.7 using prime focus technique and a 35mm camera ? or a webcam ? Does anyone have any experience ?
Thanks,
Andre

July 7, 2004 10:36 PM Forum: Equipment Talk

star testing differences between the in and out focus disks

Posted By Andre Moutinho

According to Suiter's book page 14:
"The out-of-focus image has a fairly flat distribution of intensity along the radial direction, except for a slightly brighter outer ring. It is divided by diffraction groves, but they are of very low constrast. They are mostly washed out in white light"
Does anyone know how to explain this difference ? The in-of-focus seems to be much sharper than the out-of-focus.
Thanks,
Andre

July 10, 2004 06:43 PM Forum: Equipment Talk